Chilled foods a comprehensive guide 2ed 2000 stringer dennis INCOMPLETE

This introduction reviewsthe definition, range and market size of chilled food and indicates trends for thefuture.I.1 Definition Foods distributed under refrigeration and sold from refri

Chilled foods

A comprehensive guide

Second edition

Edited by Mike Stringer and Colin Dennis

Published by Woodhead Publishing Limited, Abington Hall, Abington

Cambridge CB1 6AH, England

www.woodhead-publishing.com

Published in North and South America by CRC Press LLC, 2000 Corporate Blvd, NWBoca Raton FL 33431, USA

First edition 1992, Ellis Horwood Ltd

Second edition 2000, Woodhead Publishing Limited and CRC Press LLC

ß 2000, Woodhead Publishing Limited

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Chapter 3

Dr Steve JamesFood Refrigeration & ProcessEngineering Research CentreUniversity of BristolChurchill BuildingLangford

Bristol BS18 7DYTel: +44 (0)117 928 9239Fax: +44 (0)117 928 9314E-mail: steve.james@bristol.ac.uk

Contributors

Chapter 4

Mr Robert D Heap MBE

Cambridge Refrigeration Technology

Dr Steven Walker and Dr Gail Betts

Campden & Chorleywood Food Research

Chipping Campden GL55 6LDTel: +44 (0)1386 842075Fax: +44 (0)1386 842100E-mail: r.betts@campden.co.uk

Chapter 9

Dr Helen Brown and M N HallCampden & Chorleywood Food ResearchAssociation

Chipping Campden GL55 6LDTel: +44 (0)1386 842016 (HB)+44 (0)1386 842014 (MNH)Fax: +44 (0)1386 842100E-mail: h.brown@campden.co.ukm.hall@campden.co.uk

Chapter 10

Dr Linda Everis and Dr Gail BettsCampden & Chorleywood Food ResearchAssociation

Chipping Campden GL55 6LDTel: +44 (0)1386 842063 (LE)+44 (0)1386 842071 (GB)Fax: +44 (0)1386 842100E-mail: l.everis@campden.co.ukg.betts@campden.co.uk

Chapter 11

Professor Martyn BrownMicrobiology DepartmentUnilever ResearchColworth LaboratoryColworth HouseSharnbrookBedford MK44 1LQTel: +44 (0)1234 222351Fax: +44 (0)1234 222277E-mail: martyn.brown@unilever.comxiv Contributors

Dr John Holah and R H Thorpe

Campden & Chorleywood Food Research

Chipping Campden GL55 6LDTel: +44 (0)1386 842088Fax: +44 (0)1386 842100E-mail: d.rose@campden.co.uk

Chapter 16

Ms Kaarin Goodburn

11 Yewfield RoadLondon NW10 9TDTel: +44 (0) 20 8451 0503Fax: +44 (0) 20 8459 8061E-mail: kgoodburn@bigfoot.com

Contributors xv

During the last 40 years, consumer choice has been transformed bydevelopments in the production, distribution and retailing of food, which withimprovements in the design and equipment of the domestic kitchen havefacilitated a major change in our lifestyle.

Perhaps the most striking development is the marketing of a wide andexpanding range of chilled perishable foods Convenience, easy preparation andthe ‘fresh’ and ‘healthy’ image and an extensive choice of different culinarytastes are attractive features Many products are made by industrial processesusing technology which has no parallel in the domestic kitchen Others, notablycooked ready meals of all kinds, require skills, time and patience to prepare.These developments have occurred by the application of technology to theproduction, packaging, distribution and retailing of food

The integrity and safety of chilled foods is multifactorial Care is required atevery stage in the food chain, from primary production of raw materials, throughmanufacture, distribution, retail and consumer use

This book provides a comprehensive guide to the many important aspectsnecessary to provide the consumer with safe, high quality products, and includesrecent developments in legislation Since the introduction of the firstcoordinated chilled distribution chain in the late 1960s, substantial develop-ments have occurred in the refrigeration equipment available and in thetemperature monitoring and control systems

Product, process and packaging developments which have occurred over thelast 20 years have resulted in chilled foods representing a larger and increasingproportion of weekly purchases for home consumption as well as in institutionaland service catering Their safety and reliability have resulted from theapplication of scientific principles of food technology and depend on a series of

Preface

safety factors in their preparation, processing, distribution and retail sale Theoverriding requirement is for the reliable ‘chill chain’ to control the temperature

at every stage from the final process of production to the moment of purchaseand absence of abuse by the consumer Hygienic preparation and productionareas are a further essential requirement for chilled food manufacture This hasresulted from a greater understanding and awareness of hygienic design ofequipment and buildings, together with appropriate cleaning and sanitationregimes Developments in methods of detection of microorganisms have greatlyassisted in improving approaches to hygiene practices and monitoring themicrobiological status of raw materials and finished products

The establishment of the shelf-life of chilled foods requires a fullappreciation of the microbiological, chemical, physical and biochemical aspectswhich influence the sensory acceptability of products These factors arediscussed in relation to the safety and quality of products, together with methods

of determining shelf life of such products The importance of the application ofHACCP as part of quality management systems in the production anddistribution of chilled foods brings together the many aspects of chilled foodswhich are covered in this book

Further developments in processing and packaging technology willundoubtedly contribute to the continued development and innovation in thechilled food sector High pressure processing, electric-field sterilisation andactive and intelligent packaging all offer potential in this respect

As editors, we have between us over 35 years experience in chilled foodscience and technology Our contacts with the contributing authors have beenbuilt up over these years They all have wide research and industrial experienceand are recognised experts in their fields We consider ourselves fortunate tohave secured their cooperation in providing a major and unique contribution tothe scientific and technical understanding of the chilled food market

We are grateful to all the authors for applying themselves so diligently to givethe best of their knowledge and skills

Mike StringerColin Dennisxii Preface

Preface xi

List of contributors xiii

Introduction: the chilled foods market 1 C Dennis and M Stringer, Campden and Chorleywood Food Research Association I.1 Definition 1

I.2 Drivers in the chilled food sector 3

I.3 Overall market size 6

I.4 Individual categories within the chilled food sector 12

I.5 Conclusion 15

I.6 References 16

Part I Raw materials 1 Raw material selection: fruit and vegetables 19

L Bedford, Campden and Chorleywood Food Research Association 1.1 Introduction 19

1.2 Criteria for selection 20

1.3 Specifications 28

1.4 New trends in raw material production 30

1.5 New trends in plant breeding 31

1.6 Conclusion 32

1.7 Sources of further information and advice 33

1.8 References 33

Contents

2 Raw material selection: dairy ingredients 37

L R Early, Harper Adams University College 2.1 Introduction 37

2.2 Milk composition 37

2.3 Functional approach 38

2.4 Sensory properties 39

2.5 Microbiological criteria for milk products 41

2.6 Chilled dairy products and milk-based ingredients used in chilled foods 41

2.7 Chilled desserts 52

2.8 Ready meals 53

2.9 Maximising quality in processing 53

2.10 Food safety issues 55

2.11 Future trends 57

2.12 References 58

3 Raw material selection: meat and poultry 63

S J James, Food Refrigeration and Process Engineering Research Centre 3.1 Introduction 63

3.2 The influence of the live animal 65

3.3 Pre- and post-slaughter handling 69

3.4 Conclusions 72

3.5 References 73

Part II Technologies and processes 4 The refrigeration of chilled foods 79

R D Heap, Cambridge Refrigeration Technology 4.1 Introduction 79

4.2 Principles of refrigeration 81

4.3 Safety and quality issues 81

4.4 Refrigerant fluids and the environment 82

4.5 Chilled foods and refrigeration 83

4.6 Chilling 84

4.7 Chilling equipment 85

4.8 Chilled storage 87

4.9 Refrigerated transport 90

4.10 Refrigerated display cabinets 94

4.11 Regulations and legislation 96

4.12 Sources of further information 97

4.13 References 97

vi Contents

5 Temperature monitoring and measurement 99

M Wolfe, Food Standards Agency, London 5.1 Introduction 99

5.2 Importance of temperature monitoring 101

5.3 Principles of temperature monitoring 102

5.4 Temperature monitoring in practice 105

5.5 Equipment for temperature monitoring 116

5.6 Temperature and time–temperature indicators 126

5.7 Temperature modelling and control 130

5.8 Further reading 131

5.9 References 131

6 Chilled food packaging 135

B P F Day, Campden and Chorleywood Food Research Association 6.1 Introduction 135

6.2 Requirements of chilled food packaging materials 135

6.3 Chilled food packaging materials 136

6.4 Packaging techniques for chilled food 139

6.5 Future trends 147

6.6 Sources of further information 149

6.7 References 149

Part III Microbiological and non-microbiological hazards 7 Chilled foods microbiology 153

S J Walker and G Betts, Campden and Chorleywood Food Research Association 7.1 Introduction 153

7.2 Why chill? 154

7.3 Classification of growth 154

7.4 The impact of microbial growth 156

7.5 Factors affecting the microflora of chilled foods 157

7.6 Spoilage microorganisms 162

7.7 Pathogenic microorganisms 167

7.8 Temperature control 173

7.9 Predictive microbiology 174

7.10 Conclusions 178

7.11 References 179

8 Conventional and rapid analytical microbiology 187

R P Betts, Campden and Chorleywood Food Research Association 8.1 Introduction 187

8.2 Sampling 188

8.3 Conventional microbiological techniques 188

8.4 Rapid and automated methods 191

Contents vii

8.5 Microbiological methods – the future 214

8.6 References and further reading 214

9 Non-microbial factors affecting quality and safety 225

H M Brown and M H Hall, Campden and Chorleywood Food Research Association 9.1 Introduction 225

9.2 Characteristics of chemical reactions 226

9.3 Chemical reactions of significance in chilled foods 226

9.4 Characteristics of biochemical reactions 231

9.5 Biochemical reactions of significance in chilled foods 233

9.6 Characteristics of physico-chemical reactions 238

9.7 Physico-chemical reactions of significance in chilled foods 238 9.8 Non-microbiological safety issues of significance in chilled foods 243

9.9 Conclusions 248

9.10 References 248

Part IV Safety and quality issues 10 Shelf-life determination and challenge testing 259

G Betts and L Everis, Campden and Chorleywood Food Research Association 10.1 Introduction 259

10.2 Factors affecting shelf-life 260

10.3 Modelling shelf-life 268

10.4 Determination of product shelf-life 270

10.5 Maximising shelf-life 278

10.6 Challenge testing 279

10.7 Future trends 283

10.8 References 283

11 Microbiological hazards and safe process design 287

M H Brown, Unilever Research, Sharnbrook 11.1 Introduction 287

11.2 Definitions 290

11.3 Microbiological hazards 304

11.4 Risk classes 307

11.5 Safe process design 1: equipment and processes 308

11.6 Safe process design 2: manufacturing areas 316

11.7 Safe process design 3: unit operations for decontaminated products 323

11.8 Control systems 328

11.9 Conclusions 332

11.10 References 333 viii Contents

12 Quality and consumer acceptability 341

S R P R Durand, HP Foods Ltd 12.1 Introduction 341

12.2 What defines sensory quality? 342

12.3 Sensory evaluation techniques 344

12.4 Determining consumer acceptability 349

12.5 Future trends and conclusion 351

12.6 References 352

13 The hygienic design of chilled foods plant 355

J Holah and R H Thorpe, Campden and Chorleywood Food Research Association 13.1 Introduction 355

13.2 Segregation of work zones 357

13.3 High-risk barrier technology 363

13.4 Hygienic construction 380

13.5 Equipment 389

13.6 Conclusion 394

13.7 References 394

14 Cleaning and disinfection 397

J Holah, Campden and Chorleywood Food Research Association 14.1 Introduction 397

14.2 Sanitation principles 398

14.3 Sanitation chemicals 402

14.4 Sanitation methodology 409

14.5 Sanitation procedures 414

14.6 Evaluation of effectiveness 416

14.7 Management responsibilities 421

14.8 References 423

15 Total quality management 429

D J Rose, Campden and Chorleywood Food Research Association 15.1 Introduction 429

15.2 The scope of a quality system 433

15.3 Developing a quality system 435

15.4 Implementation 442

15.5 Performance measuring and auditing 446

15.6 Benefits 448

15.7 Future trends 449

15.8 References and further reading 450

16 Legislation 451 K Goodburn, Chilled Food Association 16.1 Introduction 451

Contents ix

16.2 Food law is reactive 451

16.3 Food laws and international trade 452

16.4 Chilled foods are 453

16.5 Approaches to legislation 454

16.6 Codex 455

16.7 ATP 457

16.8 Canada 458

16.9 European Union 458

16.10 Australia/New Zealand 461

16.11 France 462

16.12 The Netherlands 463

16.13 United Kingdom 464

16.14 United States 465

16.15 Summary 468

16.16 References and further reading 468

Index 474

x Contents

Chilled food technology has had a very significant impact on the types of foodeaten by consumers during the 1980s and 1990s This method of foodpreservation has satisfied the desires of people for safe, reliable, ‘fresh’ productsproviding convenience despite the limited shelf-life This introduction reviewsthe definition, range and market size of chilled food and indicates trends for thefuture.

I.1 Definition

Foods distributed under refrigeration and sold from refrigerator cabinets havebeen available for many years Although there were many new chilled productintroductions made during the 1970s, it was not until the 1980s that significantnumerous and major technological developments for chilled foods occurred(Bond 1992) This trend continued throughout the 1990s with the majoremphasis on value added, convenience and increasing consumer choice Thisunprecedented activity during the 1980s and 1990s stimulated the production ofgood practice guides related to refrigerated or chilled foods In 1990, theInstitute of Food Science and Technology (IFST) defined chilled foods as

‘perishable foods which, to extend the time during which they remainwholesome, are kept within specified ranges of temperature above 1ºC’ (IFST1990) More recently the UK Chilled Foods Association (CFA) restricted theterm to ‘prepared foods’ with the following definition ‘prepared foods that, forreasons of safety and/or quality, are designed to be stored at refrigeratedtemperatures (at or below 8C but not frozen) throughout their entire life’ (CFA1997) Whereas the IFST definition emphasises ‘perishability’, the CFA

Introduction

The chilled foods market

C Dennis and M Stringer, Campden and Chorleywood Food Research Association

definition excludes non-prepared materials such as raw meat, poultry and fishand commodity dairy products such as butter and cheese which are also notconsidered ‘prepared’ The more general and broader definition of chilled foodshas been used in compiling the content of this book, although some sectionsmore appropriately only deal with prepared chilled foods as defined by theCFA.

Food Products Intelligence (FPI) at Campden and Chorleywood FoodResearch Association (CCFRA) has been monitoring new UK food and drinkproduct introductions since 1969 Its records of new products for the 1980s and1990s illustrates the dramatic increase in the number of chilled productsidentified as new (Table I.1) with almost fourfold increases in the 1980s andagain in the 1990s The definition of ‘new’ used by FPI is one that appears in amajor food retail outlet and is previously unknown to FPI or has been recorded

by FPI but has been packaged in a different size/format which creates a neweating occasion or new consumer purchase Frequent updates on new chilledfoods entering the UK market-place are available from FPI together with fulldetails of each product on the NewFoods CD-ROM1 or via the internet(www.newfoods.com)

Unlike other major technology sectors (e.g frozen foods, ambient foods) thedevelopment of the chilled foods market in the UK has been dominated by ownlabel brands for example Marks & Spencer, Tesco and Sainsbury Approxi-mately 80% of new chilled foods introduced during the 1980s and 1990s wereown label In particular, Marks & Spencer with the St Michael brand isrecognised by both the trade and the consumer as having pioneered the earlydevelopment of chilled foods and for initiating many innovative productconcepts which have since been built on and expanded by other brands.Chilled foods can be designed to be ready to eat, to be reheated (minimalheating before serving for organoleptic purposes) or to be cooked (thorough and

Table I.1 Number of chilled product introductions in the UK market-place

prolonged heating before serving for both safety and quality) Cooked chilledfoods are sometimes wrongly referred to as ‘cook-chill’ This specific category

of foods has been defined as a catering system based on the full cooking of foodfollowed by fast chilling and storage in controlled temperature conditions (0–3ºC) and subsequent thorough reheating before consumption (Department ofHealth (UK) 1989) Cook-chill foods have a maximum recommended shelf-life

of five days, inclusive of the day of cooking

I.2 Drivers in the chilled food sector

The background to the market in the UK is provided by demographic trendsshown in Table I.2 This shows the biggest areas of growth to be the 10–14, 35–

44 and 55–64-year-old age ranges Against this background, there are a number

of forces driving the market:

Table I.2 Demographic trends in the UK 1992–2002 (Source: Office for NationalStatistics)

1992 1997 2002 (estimate)

(millions) (millions) (millions) population) change

The drive towards more convenience foods, such as ready meals, hasreflected the decline in traditional home-prepared meals and the associatedskills Convenience is a specific need of the cash-rich time-poor consumer Thisdevelopment is in part the result of the increase in the number of workingwomen, single-parent and single-person households with limited time availablefor home cooking Government estimates suggest that there are over 12 millionwomen in full or part-time work in the UK, representing 45% of the totalworkforce Also in the UK, demographic trends show particular growth innumbers of older children and their parents It is these families in particular,with children at school and with a greater degree of independence, where there ismost scope for women to undertake part- or full-time work It is also in thesefamilies in particular that members have developed more independent andflexible patterns of eating Such patterns have also been stimulated by theincrease in microwave ownership and the dramatic rise in the availability ofmicrowaveable foods, especially chilled foods (see Table I.3) This can be seen

in the increase in ‘snacking’, eating more frequent small meals at varying times

in the day Research in 1998 suggested that 31% of UK housewives snackedbetween meals (Anon 1998a) The trend towards snacking is also reflected inthe decline of the single family evening meal, and the shift towards differingmembers of the family eating at different times This development has alsoprompted consumers to look for a range of light, easy to use ingredients such ascheese spreads or salads, for example, which can be used to prepare a variety ofquick snacks or meals tailored to the requirements and preferences of individualfamily members Recent research also shows that the total lunch box occasions(i.e prepared and packed lunch) have grown steadily over the past seven years,

up by 21%, with sandwiches featuring in 81% of these Children are estimated toconsume 675 million sandwiches in the UK or 7% of total consumption (Anon.1999b)

A survey of 25,000 adults in the UK in 1997 found that 17% of all thosesurveyed and 22% of women in the survey were concerned about countingcalories in their diet, whilst over half of all respondents claimed to have reducedfat intake in their diet In the US, surveys also suggest that consumers are

Table I.3 Different categories of chilled food product introductions in the UK place

concerned about nutritional issues, particularly information on calorie and fatcontent of food products (Bender 1992, Rodolfo 1998) The trend in attitudes inthe UK has been for a slight reduction in concern about healthy eating since theearly 1990s, but a large number of consumers remain concerned about levels offat intake This is noticeably true of the 35–44-year-old age range, which has aparticularly high proportion of dieters The overall picture is of consumersfeeling more in control of their diet, looking for low-fat and low-calorie productsbut with a greater tendency to allow the occasional treat in what they eat.Consumers have also shown an increased interest in the origin andcomposition of food products and in their methods of production Afteradverse publicity in the 1980s, consumers demonstrated an increased concernabout the health implications of synthetic additives, related to a general fear ofchemicals and their possible links to disease or allergy (Sloan 1986, Crowe

1992, Wandel 1997) This is reflected in increasing consumer pressure forfresh-tasting products with fewer preservatives and minimal preparation.During the 1990s there has also been a growing interest in moreenvironmentally friendly and ‘natural’ methods of production, reflected indemand for organic foods (Jolly 1989) The FPI at Campden and ChorleywoodFood Research Association recorded approximately 5% of the new chilled foodproducts in 1999 as organic

Exposure to a wider range of cuisine, stimulated in part by the growth inoverseas holidays, has encouraged consumers to look for greater variety andnovelty in the food they eat There has been much greater interest in ethnic food,reflected for instance in the growth in popularity of Chinese, Indian and otherethnic chilled ready meals Britain’s younger generations are reported to be asfamiliar with ethnic food as with roast beef with nearly three-quarters of Britishhouseholds buying ethnic food (Anon 1999c) Consumers are now moreadventurous than ever, demanding variety and authenticity from the dishesselected The flavours for the start of the new millennium are predicted tooriginate from South America (e.g Cuba, Argentina, Brazil) to extend the hotand spicy trend (Sloan 1999) In tandem with this interest in variety, consumerscontinue to put a premium on taste and enjoyment of food Recent research inthe UK suggests that 21% of housewives ranked taste over other factors in whatthey ate, with 14% of respondents claiming to buy treats for themselves and theirfamilies at the weekend (Anon 1998b) This interest reflects the relative decline

in health concerns as a dominant factor in food purchases This renewedemphasis on food as a treat or an indulgence has, for example, fuelled theexpansion of the chilled desserts market

Competition in the chilled food sector has intensified, with the leadingretailers increasing the range of own-label products, and an increasingemphasis throughout the sector on quality and value-added products Table I.4indicates the new product introductions by the major UK retailers during recentyears and not only particularly highlights the leading position of Marks &Spencer in this sector, but also the high level of activity by some of the othermajor players

Introduction 5

Table I.5 summarises the key features of the UK chilled food market in the1990s and highlights the importance of drivers such as convenience includingmicrowaveability, snacking, healthy eating, ethnicity and vegetarianism Inaddition, notable inclusions are products designed for home entertainment such

as items for dinner parties as well as more informal type snacks and productsspecifically for children These trends have developed from the extensive range

of products available during the 1980s (Bond 1992)

I.3 Overall market size

In the UK, the chilled foods market for dairy products, meat products, readymeals, pizzas and prepared salads was valued at £5 billion in 1997, representing6% of total grocery sales (Anon 1998b) Forecasts are for continued growth at

as much as 6% per annum, reaching a market value of over £6 billion by 2002(Anon 1998a; Anon 1998b, Anon 1997) The various chilled foods categorieshad the following shares of overall UK chilled foods sales in 1997 by value(Anon 1998a, Anon 1997: figures have been rounded to the nearest wholenumber):

• dairy products 70%

• meat products (excluding raw meat, poultry and fish) 15%

• ready meals, pizzas and prepared salads 15% (chilled ready meals 9%; pizzas5%; prepared salads 1%)

These categories show differing levels of growth in value over the period 1993–

7 ((Anon 1998a; Anon 1998b, Anon 1997, IDF 1995):

Table I.5 Product features of UK chilled foods market in the 1990s

Product area Key product development

Yellow fats Butter

• Increasing numbers of organic butters

• Biggest innovation has been spreadable butter

Fat blends and spreads

• Spreads have been one of the success stories of the 1990s

• The aim to produce a ‘butter tasting’ product with low/or nocholesterol

• Olive oil products e.g Olivio

• The move to functional products e.g BenecolCheese • Cheddar still popular, the stronger flavours being most popular

• Regional varieties and flavour additions continue

• Healthy eating (specifically low fat)

• Innovation with cheese snacks e.g Lunchables, Dunkers andCheestrings – ideal for lunch boxes

• Now large variety of imported cheeses

• Cottage cheeses follow the ethnic trends for flavour additions andhealthy eating trends

• Organic varieties availableMilk • Overall, decline in milk consumption

• Health-conscious consumers have switched to lower-fat milks

• Few with added vitamins and aimed at specific groups ofconsumers (age groups)

• Flavoured milks are growing, aimed at younger consumers (incompetition with soft drinks)

• Organic milks also availablePoultry • Gained more popularity during BSE crisis

• Processed poultry products, and crumb coated are popular withchildren

• Added value, marinaded chicken, particularly popular for thebarbecue season

• Free range and organic also available at a premiumMeat • Leaner, smaller joints developed, more modern image

• Quick cook joints and presentations, component meals and recipedishes – convenience

• Sausages declined during BSE crisis, but since then sausages havemoved more upmarket and traditional – now more of a premiumimage

• Marinaded/added-value cuts available, particularly during thebarbecue season

• RSPCA freedom food, animal husbandry, organic meats availableFish and seafood Fish

• Perceived as healthy, benefited from BSE crisis

• Processed and crumb coated or battered aimed at encouragingchildren to eat more fish

• In store fishmongers, with trained staff to ‘educate’ and helpconsumers

• Salmon, once seen as a speciality, now farmed, are used in recipedishes

Introduction 7

Table I.5 Continued

Product area Key product development

Fish and seafood Seafood

(continued) • Increased in popularity Convenience and further processing make

seafood more attractiveDips, paˆte´ and

spreads

• Products are convenient, no preparation and reflect trends seenacross other food groups e.g vegetarian, healthy eating, ethnicand traditional

• Lend themselves to the snacking culture

• Paˆte´s – especially fish are ideal for starters and entertaining, with

the emphasis on presentation

• Sandwich spreads – quality and fresh ingredients to compete with

the huge range of sandwiches now available

• Dips – ideal complementary products for crisps and snacks

Pizzas • A success story of the 1990s

• Huge range of different bases and toppings, reflecting some of thetrends seen across all food groups i.e vegetarian, healthy eating,children’s, ethnic

• Perceived as a snack, but also popular as a main meal

• Suits today’s lifestyles of minimum cooking and no preparationtime

Pastry products • Pastry products still popular with the fillings reflecting vegetarian,

healthy eating, traditional – poultry meat, fish and vegetables

• Many different formats and use of different pastries e.g filo pastry

• Lattice topped became popular

• Individual pies as well as family pies – ideal for single-personhouseholds and snacking

Recipe dishes

and ready meals

• Indian, Italian and Oriental meals are outstripping traditionalmeals as popular alternative for consumers

• Kit meals such as Fresh Creations and Just Cook (packedindividually and arranged together in one cabinet, so combinationscan be selected) (from Sainsbury’s) enable customers to createrestaurant-quality meals for two in 10 minutes

• More indulgent and up-market foods e.g Tesco’s Finest andMarks & Spencer Cafe´ Specials for eating in rather than eating out

• Snack meals suit today’s lifestyles with family members eatingdifferent foods at different times Vegetarian, healthy eating,children’s products Easy, convenient, microwave, reheat

• Meat alternatives such as Quorn giving choice in basic raw materiale.g minced, cubed and in recipe dishes, and complete meals

• Poultry recipe dishes and ready meal new products nowoutnumber red meat

Pasta • Fresh pasta has grown in popularity, with the perception of it

being ‘quicker to cook’ and ‘because it’s ‘‘fresh’’ it’s better’

• Pasta and sauces create quick, convenient meals with thatMediterranean healthy image

• Filled pasta with an Italian-style bread is a quick-to-prepare mealRice • Many different ethnic styles to accompany the many different

dishes from India, China, Thailand Ready prepared andconvenient for quick reheating in either the microwave or the oven

• More authentic styles as consumers become more knowledgeable

8 Chilled foods

Table I.5 Continued

Product area Key product development

Rice (continued) • Arborio rice (Italian risotto rice) eaten as a ready meal The

traditional dish is quite time consuming – microwave reheatingmakes this a very quick meal

• Fresh oil-based salad dressings are now also a feature of thechilled cabinet

• Pre-washed salads offer healthy, convenient product which can betailored to today’s eating requirements

• All-year-round availability

• Ideal for sandwiches and replicating restaurant-style foods andpresentations

• Organic possibilities

• Dressed salads, layered salads and deli-style salads reflect choice

of ingredients, different styles of eating, snacking, healthy,vegetarian and ethnic flavours and styles

• Salad dressings – a huge variety of many flavours, reflecting

ethnic influences and healthy eating

• Pasta sauces no longer a niche market – to accompany pasta which

is convenient, easy to prepare, healthy and extremely versatile –fitting today’s lifestyles

• Many new flavour sauces - microwaveable in the pot

• Stir fry sauces, in many flavours and ideal for quick cook stir fries– again convenient, easy to prepare, healthy and extremelyversatile

Vegetables • Again, convenience and quick preparation of fresh products at a

price premium – suiting today’s lifestyles

• Ready prepared and ready to cook, some with added value sauces,dressings and flavoured butters – microwaveable in the pack

• May be just bunches of carrots or upmarket variety mixes, or stirfry combinations using ethnic ingredients

• No preparation, no waste, quick and easy and versatileVegetable

Introduction 9

Table I.5 Continued

Product area Key product development

Cooked poultry • Varieties of joints e.g breast, leg or wings or whole birds in many

ethnic flavours – now commonplace

• Can be reheated or eaten cold with salads or ideal for snacks andsandwiches

• Also available sliced and flavoured and cut into strips or chunksfor cooking

• Not only prepacked but also available on deli counter

• Home Meal Replacement market is growing – one of the mostpopular purchases is the rotisserie chicken

Cooked meats • Availability of ethnic meats e.g proscuito, salami

• Many styles of cooked meats, straight and flavoured

• Different formats for different uses – thick sliced and wafer thin

• All suit sandwich making, snacking

Sandwiches • Innovation in styles of bread, ethnic and traditional e.g filled

rolls, baguettes, croissants, wraps

• Innovation in fillings – children’s style, ethnic, traditional, healthyeating, vegetarian

• Suits snacking and grazingSoups • Reflecting the ongoing need for convenience, quality (particularly

in terms of taste) and choice, this market has seen massive growth

• The flavours and combinations reflect traditional ethnic, ian and healthy eating versions

vegetar-• They range from cold summer soups for entertaining to heartywinter recipes, as meal replacements

• Many are microwaveableFruit juices and

drinks

• Juices, drinks, nectars, smoothies – freshly squeezed, smooth,

‘with bits’, some with added vitamins

• Many exotic flavour combinations

• Seen as healthy and consumption increases in hot weather

• Some organic varieties availableYoghurts • One of the oldest products in the supermarket but the range of

products on offer is astounding

• The biggest market is the children’s sector

• Low-fat and very low-fat yoghurts constitute a big market

• Luxury yoghurts are also important, as are plain natural

• Bio yoghurts also have a following and it is expected that in thefuture functional yoghurts will grow e.g Maval, Benecol

• Organic also have a niche sector

• Sold as individuals, multipacks and split pots – ideal for snacking

10 Chilled foods

Whilst the more mature dairy products market has shown steady growth, themost dynamic categories have been in ready meals, pizzas and salads, reflectingthe increasing importance of convenience foods in consumer purchasing.These figures may be compared to data on two dairy products for Europeshown in Table I.6 The biggest per capita consumption of yoghurt in 1992 was

in the Netherlands, followed by France, Switzerland, Finland and Sweden.Average per capita consumption of yoghurt in Europe in 1992 was 9.76 kg Thebiggest per capita consumption of chilled desserts in 1992 was Denmark,followed by France, Germany, Austria and Luxembourg, with an average percapita consumption across Europe in 1992 of 2.86 kg The UK spends less onfood as a percentage of total consumption, and around half of the Europeanaverage for per capita consumption of yoghurt and chilled desserts It is perhapsnot surprising that, from such a modest base, it has shown some of the mostdynamic growth Whilst average annual growth in yoghurt and chilled dessertsconsumption by value for Europe as a whole between 1987 and 1992 was 6%and 14% respectively, comparable growth in the UK was 17% and 50% Thiscomparison suggests that these sectors of the UK chilled foods market arecatching up rapidly with Europe and that growth will settle down in the comingdecade to more modest levels reflecting the European average

Table I.5 Continued

Product area Key product development

Desserts • Pot desserts and fromage frais suit snacking, luxury, healthy

eating and children’s trends, similar to the yoghurts

• Packaged in individual pots, some with spoons, multipacks,twinpots and tubes e.g Frubes

• Some of the indulgent varieties are dual branded with famousconfectionery brands e.g Cadbury’s flake

• Some up-market desserts are ideal for entertaining and arepackaged in glass reusable containers

• Amongst chilled desserts are such products as cheesecakes, fools,mousses, rice puddings and trifles

Ethnic

accompaniments

• As people travel more and experience different cuisines they aredemanding more authentic foods The accompaniments for theseare widely available as prepacked products and also sold on thedeli e.g onion bhajis, samosas, spring rolls They are ideal forparties, snacking and as part of an Indian or Chinese mealMeat alternatives • There are many reasons for people becoming vegetarians or

decreasing their intake of meat

Introduction 11

I.4 Individual categories within the chilled food sector (see also Table I.5)

I.4.1 Dairy products

Dairy products remain the biggest single category in the chilled foods sector.The various components of this category by value in 1997 in the UK were(Anon 1998a; Anon 1998b):

• butter, margarine and spreads 4%

• yoghurts/fromage frais 19% (yoghurt 15%; fromage frais 44%)

• desserts 74–77% (Keynote and Mintel estimates)

• cream 20%

Table I.6 Consumption of yoghurt and chilled desserts in Europe (Sources: Eurostat

Yearbook 1997; European Food Databook 1994)

Country Consumption of food Per capita consumption Per capita consumption

as a percentage of of yoghurt in 1992 (kg) of chilled desserts in

Cheese remains both the biggest segment of dairy products and the biggestsingle sector in the chilled foods market in the UK (just under 30% of the chilledfoods market as a whole) The sector has demonstrated steady growth in recentyears The strength of the market has been due, in part, to the emergence of low-fat cheeses, but it has also been boosted by consumers’ desire for greater varietyand improved taste, reflected in the popularity of mature cheddar and specialitycheeses The soft cheese market has also benefited from the growth in snackingwith successful brands such as Kraft Dairylea and Philadelphia.

The overall market for butter, margarine and spreads has remained generallystatic Consumption of butter and margarine has declined overall, balanced by anincreased use of low-fat spreads influenced by consumer concern for healthiereating More recently, sales of butter have shown some improvement, suggestingconsumers might be showing a renewed interest in taste as a factor in purchasingdecisions Sales have also been boosted by the introduction of spreadable butteraimed in part at the snacks market

The yoghurt and fromage frais markets have benefited both from the move tosnacking and the concern for healthier eating Manufacturers such as Mu¨llerhave met this demand through such developments as split pots and bio yoghurtswhich have helped it move out of the dessert category in consumers’ eyes.Because they combine nutritional value with sweetness and are in convenientlysmall portions, yoghurt and fromage frais have become especially popular as achildren’s snack The growth in sales has also been driven by increased interest

in the range of Continental food, boosting sales of fromage frais and Greekyoghurt, for example Natural fromage frais is widely seen by consumers as alow-fat alternative to cream, and this, together with its popularity as a children’ssnack, has kept sales expanding significantly Indeed, some 39% of housewives

in the UK claimed to have purchased fromage frais at some point during 1998(Anon 1998a) Similarly, the biggest areas of growth for yoghurt have been inbio yoghurts, low-fat and children’s yoghurts, reflecting in part the growingimportance of the 10–14 age group and their diet-conscious middle-agedparents Per capita consumption of yoghurt in the UK is 4.8 kg per annum, underhalf of the total for Germany and just over one-fifth of French consumption,suggesting scope for further expansion of the UK market However, with anannual growth rate of 17% between 1987 and 1992, compared to a Europeanaverage of 6%, The UK market has been catching up rapidly At a per capitaconsumption of 2.1 kg in 1993, the United States lags behind even the UKmarket, suggesting potential for growth (IDF 1995)

The most dynamic single sector of chilled dairy products has been desserts.This category is highly diverse, including rice pudding, mousse, trifles, cheesecake and gateaux The biggest single categories are mousse and trifles Thesuccess of this category has been partly the result of the development of low-fatdesserts, but it has been fuelled by manufacturers’ emphasis on luxury, premiumproducts meeting consumer demands for taste and enjoyment The biggest areas

of expansion in this sector have been in sales of mousse, non-cream toppeddesserts such as tiramisu, rice pudding and fools Sales of cream represent a

Introduction 13

small proportion of overall chilled dairy product sales, but sales have alsobenefited from a renewed consumer interest in taste and a sense of enjoymentand indulgence in eating.

I.4.2 Chilled meat products

Even when more narrowly defined to exclude raw meat, the chilled meats sector

is the second largest sector of the dairy market, and has shown significant recentgrowth, despite concern over BSE Growth has been stimulated by consumerdemand for prepacked meats for snacks Ham remains the most popular meat atthe delicatessen, outselling other meats such as beef, pork and poultry However,sales in this sector have also benefited from consumer interest in Continental,premium-priced products such as paˆte´ and salami

I.4.3 Chilled ready meals, pizzas and prepared salads

Although they still represent only 15% of the overall UK chilled foods market,these sectors have seen some of the most dramatic growth as consumers havelooked for an alternative to home cooking Improvements in quality have madeready meals a cheaper and more convenient option than eating out or ordering atakeaway Almost half the sector is made up of ethnic dishes, primarily Chineseand Indian, reflecting the interest in more exotic tastes, with a further third made

up of Continental recipes, particularly Italian Indeed, Italian ready mealsrepresent the biggest single variety of ready meal given the healthy image ofpasta and its appeal to children Over the period 1993–98 the value of the chilledready-meals market has been estimated to have grown by as much as 50% in realterms, with recent growth rates of 7–10% a year Within the ready-meals market,the biggest growth has come from vegetable-based ready meals, followed byfish-based meals and then those with a meat base, reflecting the healthier profile

of vegetables and fish The UK is the most developed market in Europe forchilled ready meals, with per capita consumption of 1 kg in 1994, compared to0.3 kg for Germany, 0.2 kg for France and 0.1 kg for Spain (Anon 1996) If UKtrends are reflected in Europe, the European market for ready meals may wellhave significant future potential

Pizza sales have shown the most dramatic growth of all, with an annualgrowth rate of over 10% in the period 1994–97 Manufacturers have sought tostimulate demand in part by introducing a wider variety of flavours to exploitconsumer interest in more exotic tastes, and also by extending the range ofvegetarian pizzas to respond to consumers’ healthier life styles At the premiumend of the market manufacturers have sought to provide a more authentic taste

by refocusing on traditional Italian recipes and ingredient quality Consumerinterest in convenience, healthier eating and more exotic tastes has fuelledstrong growth in the prepared salads sector Salads are now widely seen as aconvenient replacement for vegetables in a main meal, as well as a popularingredient in snacks Manufacturers have responded by producing a wider range

14 Chilled foods

of mixed salads, using new varieties of leaves as well as other ingredients such

as peppers

Another important sector of the chilled food market not mentioned above issandwiches, a major feature of the snacking habit According to the BritishSandwich Association sandwiches are now the UK’s most popular fast food with

a market of £3.25 billion and growing at 13% a year (Anon 1999d) Sandwichesare estimated to represent 41% of the fast food market compared to burgers at18% and fish and chips at 12% The UK has the highest per capita consumption

of sandwiches in the world, with every man, women and child munching theirway through 37 bought sandwiches a year Sandwiches are perceived as ahealthy snack meal, they are portable, yet nutritious and offer infinite variety interms of combinations of ingredients which can be used This variety and choice

in availability of sandwiches is highlighted in the data of new introductions inthe major retail outlets recorded by FPI at CCFRA The standard varieties,however, still account for 80% of the total sales and there has been little change

in the most popular varieties according to the British Sandwich Association Thetop selling sandwiches by fillings are tuna, chicken, egg mayonnaise/salad, ham,cheese, prawn and bacon, lettuce and tomato The ethnic trend is also a feature

of the sandwich sector with for example Spanish, Italian and Moroccan varieties

I.5 Conclusion

The chilled foods market has been successful because it has met a number ofcustomer needs Chilled foods have been seen as fresh and healthy, and theyhave been ideally suited to meet the growing demand for ready meals andsnacks At the same time they have been rapidly adapted to cater for ever morecosmopolitan tastes and consumers’ desire for variety, quality of sensoryexperience, and even indulgence in what they eat

Product innovation will remain essential in an increasingly competitive sector

of the industry Market analysts suggest that continued growth may be restricted

to the ‘extremes’ of the market, that is extra low-fat products at one end andpremium indulgent products at the other (Anon 1998b) Manufacturers willneed to differentiate their products even more on the basis of quality,emphasising the fresh and ‘authentic’ taste consumers look for, and theirconcern for more environmentally friendly and ‘natural’ methods of production.Such trends suggest that the whole supply chain will need to pay attention to arange of factors, including:

• the importance of raw material selection in final product quality

• the quality of packaging and temperature control technologies across the chillchain in maintaining product quality

• the complexity and interdependence of technologies across the chill chain –the improved control of the microbiological and other factors affectingproduct safety

Introduction 15

ANON (1998a) Chilled ready meals/Yoghurt/Chilled pot desserts: market

intelligence reports Mintel International Group London.

ANON (1998b) Chilled foods: 1998 market report Keynote: BMRB

Interna-tional London

ANON(1999a) ‘Convenience is everything’ The Grocer, May 29, p 10.

ANON(1999b) Supermarketing, August 27, p 20.

ANON(1999c) ‘Ethnic Foods’ The Grocer, August 21, pp 53–66.

ANON(1999d) The Grocer, December 11, p 12.

BOND S, (1992) ‘Marketplace product knowledge – from the consumer

viewpoint’ In Chilled Foods: A comprehensive Guide, 1st eds C Dennis

and M F Stringer, Ellis Horwood Ltd, Chichester, West Sussex UK

BENDER M M and DERBY B M, (1992) ‘Prevalence of reading nutritionalinformation and ingredient information on food labels among adult

Americans: 1982–1988’, Journal of Nutrition Education, 1992 24 (6)

292–7

CHILLED FOOD ASSOCIATION, (1997) Guidelines for good hygienic practice in the

manufacture of chilled foods ISBN 1901798003 Chilled Food Association,

PO Box 14811, London, NW10 0ZR

CROWE M, HARRIS S, MAGGIORE PandBINNS C‘Consumer understanding of

food-additive labels’, Australian Journal of Nutrition and Dietetics, 1992 49 19–

22

DEPARTMENT OF HEALTH, (1989) Chilled and Frozen – Guidelines on cook-chill

and cook-freeze catering systems HMSO, 49 High Holborn, London,

WC1V 6HB

IDF, (1995) In Consumption Statistics for Milk and Milk Products 1993, Doc.

No 301, International Dairy Federation, Brussels, Belgium, pp 4–6

INSTITUTE OF FOOD SCIENCE & TECHNOLOGY (UK), (1990) Guidelines for the

handling of chilled foods, 2nd edn, IFST, London.

JOLLY D, SCHULTZ H, DIAZ-KNAUF D and JOHAL J, (1989) ‘Organic foods:

consumer attitudes and use’, Food Technology, 1989 November 60–6.

RODOLFO M N, F R, LIPINSKI D and SAVUR N, (1998) ‘Consumers’ use of

nutritional labels while food shopping and at home’, Journal of Consumer

Affairs, 1998 32 (1) 106–120.

SLOAN A, POWERS MandHOM B, (1986) ‘Consumer attitudes toward additives’,

Cereal Foods World, 1986 31 (8) 523–32.

SLOAN A E, (1999) ‘Top Ten Trends to watch and work on for the millennium’

Food Technology 53 (8) pp 40–60.

WANDEL M, (1997) ‘Food Labeling from a consumer perspective’, British Food

Journal, 1997 99 (6) 212–9.

16 Chilled foods

Part I

Raw materials

1.1 Introduction

Fresh fruits and vegetables are utilised in a wide range of chilled products Theymay be sold whole, or peeled (for example peeled potatoes and onions) orfurther prepared (e.g carrot batons) After washing or further preparation theyform ingredients for mixes such as mixed fruit or salad packs or for furtherprocessing in a wide range of products From this it can be seen that raw materialrequirements can be very varied but are specific to each end use Sourcing ofsuitable raw material is essential for the production of final products ofconsistently high quality and for this both the producer and the user need to have

a clear understanding of the requirements

In this chapter some of the criteria for selection will be discussed Theexamples are drawn from a range of fruit and vegetable crops Most whole fruitsand vegetables are best stored at chill temperatures and thus come naturallyunder the scope of this book Some however, such as potatoes and tomatoes andsome other fruits are low-temperature sensitive and should ideally be kept athigher temperatures However even these items, once they are cut and preparedneed to be kept chilled, to avoid enzyme-mediated changes and disease-relatedspoilage, both of which proceed more rapidly at higher temperatures

Supply of suitable raw material requires collaboration between the growerand the purchaser of the produce In effect, the grower forms the first link in thefood chain The decisions made, including variety selection and agronomicpractices and the grower’s skill in harvesting and where appropriate in storingthe crop are crucial steps in the supply of high-quality raw material for chilledfruit and vegetable products

1.2 Criteria for selection

First of all it is necessary to consider the factors which contribute to productvariability and what makes raw material suitable for different purposes,particularly for use in chilled food products Some of the factors are geneticallycontrolled Thus varieties may differ in size, shape and other characteristics.Many plant characteristics are also influenced by environmental factors, such assite and climate and seasonal weather patterns These genetic and environmentalaspects interact, contributing to the variability of the produce at harvest.The parts of the plant which are consumed may be leaves, stems, roots,flowering heads, fruits or seeds, all requiring harvesting at the correct stage ofmaturity Further factors apply after harvest, such as the handling and storage ofthe products before they are sold or prepared for further processing Post-harvestfactors can have a considerable impact on shelf-life and quality

1.2.1 Variety

Plant species have recognisable inherited characteristics, which can be used todistinguish them from other species Members of a species are generally able tointerbreed easily, but much less easily, or not at all with other species Within aspecies, natural variation gives rise to groups of individuals with small butdefinite differences, which are known as ‘varieties’ When the variations arebrought about by human intervention as in plant breeding then botanists use theterm ‘cultivars’ However in common parlance the term ‘variety’ is used for theman-made products of plant breeding as well

When selecting raw material for particular purposes, one of the mostimportant criteria under human control, is the choice of suitable varieties Thereare many different ways in which varieties can differ There may be obviousdifferences in colour, shape and size There may be differences in fieldcharacteristics, such as yield, plant growth habit and disease resistance In somecases flavour and other sensory characteristics may differ

For most crops, a range of varieties can be used for any specific purpose, forexample, a number of different varieties of Dutch white cabbage all possess thethick leaf texture and white colour required by the chilled salad producer Inother cases, the choice of a variety suitable for a specific purpose may be morelimited; for instance an apple variety such as Cox may be specifically selectedfor a chilled fruit salad, because of its skin colour, which will enhance theoverall appearance A good variety has to meet the requirements of the primaryproducer, processor, retailer and ultimately the consumer

Agronomic characteristics

Traditionally, farmers and growers have selected varieties for their field or

‘agronomic’ performance They have been concerned to achieve high yields, thisbeing a major factor affecting profitability This may be in terms of total yield

or, more importantly, of marketable yield The latter refers to the saleable

20 Chilled foods

produce after all waste and defective material has been removed Taking a rootcrop, such as carrots, all the roots will be lifted from the soil and grading willremove undersized and misshapen roots.

Disease resistance is another major issue Field diseases can cause completecrop losses, or they may produce blemishes, which cause produce to bedowngraded Chemical pesticides can be applied to control some, but not alldiseases Genetic resistance is preferable, reducing the need for chemicals.Disease resistance may be controlled by a single gene or by several genes actingtogether (multigene resistance) Single gene resistance is easier to work with.However the disadvantage is that plant pathogens often rapidly produce newraces able to overcome this type of resistance An example is found in downy

mildew of spinach (Peronospora farinosa f sp spinaciae) The disease is difficult

to control chemically and varieties have been bred with specific genes forresistance, originally to races 1, 2 and 3 of the disease Following the appearance

in 1995 of the new race 4, whole crops were wiped out Plant breeders have nowproduced a series of new varieties with resistance to race 41but the resistance ofthese varieties may also have a limited life Multigene resistance (fieldtolerance) gives greater stability Some varieties of lettuce show this type of

resistance to lettuce downy mildew (Bremia lactucae).

Plant habit is another varietal characteristic, which is particularly importantwhen the flowering parts of the plant or the seeds are consumed Plants shouldhave sturdy stems to enable them to remain erect in windy conditions or whenthe foliage is wet Varieties are said to have ‘good standing ability’ and not to

‘lodge’ or become flattened In the green bean crop, plant breeders have givenconsiderable thought to the plant architecture Stems need to be sufficientlystrong to support the combined weight of pods produced and, as yields increase,this becomes more of a problem If all the pods were to be bunched together atthe tops of the plants this might make for easier harvesting, but it could causeincreased lodging Plants on which the pods are distributed more evenlythroughout the plant canopy are more likely to remain upright

A major change in varieties over the last fifty years is associated with partial

or complete mechanisation of harvesting Older varieties of many crops, such ascauliflower and lettuce would have individual plants producing their heads over

a period of time In crops such as peas and beans individual pods were alsoproduced over a long period With the introduction of machine harvesting, theobjective was once-over harvesting and the result, over years of breeding, hasbeen varieties where individual heads mature very evenly Peas and beans aresaid to be more ‘determinate’, that is to say that after producing a certain number

of flowering nodes growth tends to stop The pods then all develop and can beharvested at one time

While all these field characteristics are necessary for the growth of crops,successful marketing of the crop requires attention to characteristics required bythe processor, the retailer and ultimately by the consumer These relate to quality

of the final product

Raw material selection – fruits and vegetables 21

Shape and size

Within some crops there is a range of shapes and sizes For instance there is arange of types of carrots with different shapes and size of roots Nantes varietieshave cylindrical roots and so are preferred for pre-packing Berlicum varietiesare also cylindrical They are generally larger and mature later in the season thanNantes varieties The other common UK types are the conical Chantenays andAutumn King varieties which have very large roots tapering to a point Largerroots of cylindrical or slightly conical varieties are suitable for slicing in chilledfood products

A recent development has been the breeding of specific varieties for ‘minivegetable’ production The concept is a response to consumer perception thatsmall size equates to high quality and is seen as a way of adding value tovegetable products such as cauliflower The varieties may also require specialgrowing techniques Varieties may also be selected according to their ability toproduce the correct size of portion for prepared foods Cauliflowers are oftenpresented ready cut into florets and varieties differ in the ease with which theycan be cut up and the size of florets produced.2For chopping or dicing, large size

is required and the overall yield of prepared product is an importantconsideration Large cabbages are specified for processing uses such ascoleslaw production, the total yield of cabbage shreds being the major concern.This contrasts with retail sale where smaller varieties are required

Colour and appearance

It is often said that the consumer buys by eye, so an attractive colour andappearance is essential Varieties often vary in colour The characteristic colours

of different apple varieties make them easily identified They differ not only inthe ground colour (Coxes are yellow and red, Bramleys are green) but also in themarkings known as ‘russetting’ Chilled food manufacturers will consider theflesh colour, as well as the skins and the ability to resist grey discoloration whenselecting a variety to provide colour to a mixed fruit salad

Modern commercial carrot varieties are orange, but they were arrived at bycareful selection from a varied ancestral gene pool in which yellow and purplecolours were common More recently a series of large-rooted varieties weredeveloped for dicing They had a deeper orange colour that was particularlyevenly spread across the core and flesh of the roots Colour may not be soimportant where the product is chopped or otherwise prepared White cabbagefor retail sale needs to have bright colour and fresh appearance Slight greynessmay be acceptable if the cabbage is used for coleslaw, as the colour will bemasked by the mayonnaise

Flavour and texture

To the consumer, of course, the ultimate requirement is good eating quality, andfood products should have good natural flavour and texture Varieties of somecrops such as apples have very distinctive flavours and consumers commonlyselect their own favourites e.g Cox, Golden Delicious, Russet In other crops,

22 Chilled foods

many varieties have quite similar flavour A consumer would be unlikely to beable to tell the difference between many varieties of, say, iceberg lettuce.

On the other hand, flavour has been a particular issue with Brussels sprouts.Varieties differ in flavour, particularly in levels of bitterness and excess bitternesshas caused some varieties to be unacceptable The flavour and aromacharacteristics of varieties are governed by their chemical constituents Breedersmay be able to manipulate these, in order to improve varietal quality Thechemicals responsible for bitterness in Brussels sprouts have been identified asthe glucosinolates, sinigrin and progoitrin.3 In the 1970s and 80s deep greencoloured varieties appeared on the market, which had been selected for resistance

to insect pests However, taste panel assessments showed these varieties to bebitter and chemical analysis confirmed that they were high in glucosinolates.Some varieties, such as Topline, Rasalon and Lunet had consistently goodquality over several years.4Van Doorn et al.5conducted consumer studies with arange of different Brussels sprout varieties and suggested that at a level ofglucosinolates (sinigrin plus progoitrin) of above 2.2g per kg negative consumerreaction was registered Breeders can now select for lower levels of thesechemicals either by analysis or by tasting

Flavour can vary even within the portion of the crop that is consumed Bothleeks and celery have white tissue at the base of their stems and greener tissueand leaves higher up There are differences in flavour between white and greenportions.6EU regulations7dictate the proportions of white and green in celeryfor sale and varieties vary in their ability to satisfy this requirement

The texture of a product also contributes to eating quality This is oftenrelated to maturity, with an over-mature product becoming tough However,there may be variety differences Potatoes have obvious texture differencesbeing either waxy or floury Waxy varieties are firm and will retain their shapeafter cooking They are preferred for salad use or for products such as potatoscallops Floury varieties, which soften on cooking, are used for mashedpotatoes

Chilled food manufacturers use large volumes of sliced and diced onions toadd flavour to their products Onion varieties differ in pungency In the UK themajority of main crop onions are of the Rijnsburger type which are relativelyhigh in pungency.8Some of the varieties grown in Spain are less pungent andhence ‘Spanish’ onions are used if the onion is to be eaten raw The AmericanVidalia type is noted for its sweetness

Sweetness is an important flavour attribute of most crops but sugar levels canalso be important for other reasons Amounts of reducing sugars in potatoesinfluence colour after frying and there is a strong variety-related component tothis effect.9Maris Piper is a preferred variety for the chipping trade because it islower in reducing sugars Flavour variations in tomatoes are related todifferences in the amounts of sugars and acids in the fruit If both are at lowlevels, the flavour will be bland Commercial varieties with high levels of bothacid and sugar are preferred

Raw material selection – fruits and vegetables 23

Recently there has been interest in the health-promoting effects of some of thecomponent substances found in fruit and vegetables Varieties may differ in

amounts of these so called bioactive substances Schonhof et al.10 working oncalabrese determined concentrations of carotenoids, chlorophylls and glucosino-lates in three different varieties They reported that although there were seasonalinfluences on the concentrations of these, the genetic differences were constant

1.2.2 Crop maturity

Another major consideration in raw material production and selection isharvesting of crops at the optimal stage of maturity Visual indications oftenreflect the stage of development of the plant and aid the grower in timelyharvesting When bulb onions are mature the leaves begin to wilt and bend over.Growers refer to the ‘fall-over’ date Assessment criteria are different forvegetables and fruits and assessment of the correct stage depends on the part ofthe plant that is consumed

Leafy crops are harvested according to size and firmness Most types ofcabbage and lettuce are allowed to produce a heart and the heads should be firmand of the size required by the particular outlet Cabbage greens are harvestedbefore the hearts have had time to form Lettuce and spinach for leafy salads areharvested only a few weeks after drilling, when leaf size is very small In cropssuch as cauliflower and calabrese, where the flowering heads are consumed,assessment is also by eye and development is monitored until firm heads haveformed Once this stage is passed the heads will open out as flower developmentproceeds In over-mature calabrese, the yellow flower petals may be seen.Harvest time is less critical with root crops such as carrots, swedes, turnips, orparsnips They may be harvested when they reach the size required by aparticular outlet but are often stored in the field for several months Carrots may

be considered to have reached maturity when there is no white coloration at thetip of the root but will continue to grow after this Bunching carrots may beharvested immature, with some white roots Other types are harvested at a laterstage when roots have achieved a sufficient size to meet specific marketrequirements Similarly early potatoes are harvested immature, but other

‘maincrop’ or ‘ware’ potatoes are harvested after the leaves have died down, thisbeing a sign that the crop has completed bulking up

In some crops the immature pods or immature seeds are consumed (e.g.runner beans, dwarf French beans, peas, sweetcorn) As the seeds develop andswell they accumulate carbohydrates, first of all in the form of sugars and theseare then converted to starch as the seed dries out At the same time the pods aredrying out and the texture becomes tough or mealy Maturity assessment isparticularly critical for these crops as they rapidly become tough if left in thefield after optimum maturity In beans the seed development is monitored andmaturity is related to pod and bean size for specific varieties

Fruits are divided into two ripening types Climacteric fruits such as ‘pome’fruits (apples and pears) apricots, peaches, plums and kiwifruit continue to ripen

24 Chilled foods

naturally after harvest As the fruit matures, carbohydrates are accumulated asstarch and as ripening proceeds starch is broken down to sugars When they areallowed to mature on the tree the climacteric begins, respiration rate increasesand there is an increase in the production of ethylene gas, which promotesripening If allowed to ripen fully on the tree the crop is only suitable forimmediate sale Fruit destined for long-term storage is harvested immature andstorage conditions are designed to control ripening Non-climacteric fruit, forexample raspberries, strawberries and cherries, accumulate sugars as they ripen

on the plant and do not continue ripening after they are harvested They areharvested at maturity

Maturity of both types of fruit can be assessed using a refractometer, whichmeasures total soluble solids, and in the case of fruits this is mostly sugar Whereapplicable, starch can be measured using the iodine test This has been used forapples and pears but has been most successful as a maturity indicator for pears

1.2.3 Growing and environmental influences on suitability

In addition to variety and maturity, in the production of high-quality rawmaterial, the other major influences are environmental Growing site and seasonand the growers’ production techniques may in fact be as, or more, important tothe final crop quality but the effects are more difficult to define or control

Site

When selecting suitable sites, consideration must be given to climatic conditionsand soil type The former influences the ability to grow crops successfully InEngland, some crops such as sweetcorn are best suited to growing in southerncounties where overall temperatures are warmer and there are sufficient frost-free days Low temperatures slow down growth of the plants and cobdevelopment Frosts after sowing will kill young seedlings and at the end ofthe season will destroy the cobs Other crops, more suited to growing in the UKare able to grow at lower temperatures, e.g cabbages, potatoes, or to completetheir development in a shorter time period, e.g peas Research on carrots,mainly in Scandinavia and the USA has also shown latitude and other sitedifferences to be influential11, 12Martens et al.13found that season and site had amajor influence on sensory quality and chemical composition, with varietybeing much less important

Selection of suitable soil type is important, particularly for root crops Whencarrots are grown on stony soils the result is fanged and twisted carrots Hence inEngland either sand or peat soil types have historically been chosen Rootgrowth has been found to be different on these two soil types and roots from peatsoils are longer than the same variety from sand sites Site may also influencechemical composition and through this sensory quality Heany and Fenwick14reported differences in glucosinolate concentrations and hence bitterness ofBrussels sprout varieties from five UK sites In Ireland, Gormley15found thatsoil type influenced chemical composition and sensory quality Carrots from

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mineral soil had higher dry matter and higher levels of carotene and, aftercooking, taste panels rated them higher for flavour and softer in texture.However Day16, in a three-year project on sand and peat soils, found neithertype to be consistently better for yield or quality.

Season

Crop production is greatly influenced by seasonal weather conditions Foroptimum crop growth, the right balance of temperature and moisture arerequired This not only has a great influence on crop growth and yield, but mayalso affect post-harvest quality In wet conditions, leafy plant material oftentakes in a lot of water and results in soft tissue If this occurs at harvest it canlead to tissue which bruises easily and leads to shorter shelf-life Conversely, toolittle water leads to plants suffering from moisture stress and they may wilt orfail to develop properly as in cauliflowers which are said to ‘button’ Theyproduce only very small heads, too small to market

Disease and pest development also require very specific temperature andmoisture conditions and sophisticated prediction methods have been developed,based on weather data collected nationally, as in potato blight prediction, orlocally Some diseases prefer wet (e.g powdery mildew) and some dryconditions (downy mildew) but this is to oversimplify the topic Differentregimes are required for different parts of the life cycle of the disease.The yield of tomatoes is dependent on light levels during the growing season.Light levels also influence the growth of lettuce crops and the accumulation ofnitrates in the plants.17Manufacturers of chilled baby foods will be particularlyconcerned that their raw materials are low in nitrates

For chopped lettuce products a dense head will give the most efficientthroughput for use in a chilled salad product Recent research has shown that dayand night temperatures have large effects on the shape and density of heads oficeberg lettuce.18

Growing techniques

Production techniques constitute the one area where the grower can have a majorimpact on the yield, quality and suitability for purpose of his crops Thisincludes time of drilling, plant spacing and plant protection throughout thegrowing season and the provision of all the nutrients needed to optimiseproduction The application of fertilisers to provide the plants with sources ofnitrogen, phosphorus and potassium and other major and minor nutrients hasbeen researched over many years Nitrogen is essential for crop growth, butexcess nitrates in the tissues are perceived as a possible health hazard There are

EU prescribed levels for lettuce and spinach Field studies on a range of cropsshowed that some of the variation in nitrate levels may be attributed to rate offertiliser application, but that there is likely to be an interaction with otherfactors affecting absorption, translocation and assimilation Nitrate concentra-tions also varied in different parts of the plant, being higher for instance in theouter leaves of lettuce than at the heart.19 New research on lettuce aims to

26 Chilled foods

investigate the extent to which nitrate accumulation of protected lettuce can beadjusted by different crop management and fertiliser treatments.20

The primary producer can also influence the suitability for purpose ofparticular crops by growing and harvesting suitably sized material A majorrequirement of batoning carrots is that they are of suitable size and shape tomaximise throughput of the batoning equipment The optimum size is produced

by a combination of suitable varieties and growing techniques and this has to berelated to the requirements of different makes of equipment

1.2.4 Post-harvest handling and storage

Once a crop is harvested its quality cannot be improved At this stage, theobjective must be to maintain the produce in good condition through any short-

or long-term storage until it is delivered to the customer Thus, the ultimatequality and shelf-life of a final product depends not only on growing conditionsbut also on harvesting and on post-harvest handling Avoidance of handlingdamage at this stage is important Rough handling leads to bruises which spoilthe appearance of produce and can become a focus of infection by spoilagediseases Bruising can be a major reason for losses of fruit in store as well as forvegetable crops such as Dutch white cabbage

Maintenance of suitable post-harvest temperature is extremely important tomaximise shelf-life, both for produce for immediate use and for that to be stored.Crops continue to respire after harvesting using up reserves and shorteningshelf-life through wilting and yellowing Respiration rate is temperature relatedand is roughly halved for every 10ºC that the temperature is reduced Thegeneral rule is to remove field heat as quickly as possible after harvest and then

to maintain the produce at chill temperature This is achieved by variousmethods such as vacuum cooling for lettuce, hydrocooling of carrots andtomatoes and storage in various types of refrigerated stores (see Ch 4).Increasingly, use of the ‘cool chain’ aims to retain the produce at the requiredlow temperature during packing and transport to the retailer

Some delicate crops such as lettuce are not suitable for other than very term storage Others such as root crops, cabbage and many fruit crops can bestored for many months to provide the continuity of supply required by thechilled food manufacturer and customer Storage may be in field, for examplefor carrots, which are covered with straw, or in ambient stores for beetroot andother root crops For longer storage, refrigerated stores are used Many use moistair cooling to maintain the desired relative humidity and prevent dehydrationand positive ventilation to draw air through the stored crop

short-Specialised storage methods are required for some crops For example there

is a three-stage procedure for onion curing and storage, each stage requiring adifferent temperature and humidity.21 In the first stage the aim is to dry thesurface of the bulbs At the next stage moisture is removed from their necks athigh temperature The temperature is then reduced to prepare the onions forlong-term storage

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