Effect of hot water treatment combined with edible coating and modified atmosphere packaging on yellowing of thai lime fruit

61Table 13 Effect of hot water treatment HWT at 50oC for 5 minutes combined with edible coating and modified atmosphere packaging on total chlorophyll content of lime fruits stored at 13

THAI NGUYEN UNIVERSITY

UNIVERSITY OF AGRICULTURE AND FORESTRY

HUA TRA MY EFFECT OF HOT WATER TREATMENT COMBINED WITH EDIBLE COATING AND MODIFIED ATMOSPHERE PACKAGING

ON YELLOWING OF THAI LIME FRUIT

BACHELOR THESIS

Study Mode : Full-time

Major : Postharvest Technology

Faculty : Biotechnology – Food Technology

Thai Nguyen, 2017

THAI NGUYEN UNIVERSITY

UNIVERSITY OF AGRICULTURE AND FORESTRY

HUA TRA MY EFFECT OF HOT WATER TREATMENT COMBINED WITH

EDIBLE COATING AND MODIFIED ATMOSPHERE PACKAGING

ON YELLOWING OF THAI LIME FRUIT

BACHELOR THESIS

Study Mode : Full-time

Major : Postharvest Technology

Faculty : Biotechnology – Food Technology

Batch : 2013 – 2017

Supervisor : Assoc Prof Dr Apiradee Uthairatanakiji

Thai Nguyen, 2017

i

ABSTRACT

Thai Nguyen University of Agriculture and Forestry

Thesis title Effect of hot water treatment combined with edible coating and

modified atmosphere packaging on yellowing of Thai lime fruit Supervisors Assoc Prof Dr Apiradee Uthairatanakij

Ms Trinh Thi Chung

The influence of hot water treatment combined with edible coating on yellowing of

Thai lime fruit was studied In experiment 1, mature green limes (C aurantifolia Swingle)

treated with hot water dipping (HWD) at 50 o C for 5 minutes and then dipped into solutions containing 1.0%, 5.0% and 10.0% Sta-Fresh 8711 for 5 minutes In experiment 2, chitosan concentrations at 0.5%, 1.0%, 2.0% were used to coat surface of lime fruits for

1 minute after HWD Untreated fruits were used as a control Thereafter, the fruit were stored at 25 o C The combination of HWD and 10.0% Sta-Fresh could retain the highest hue angle value, likewise the L*, a*, b*, C* values were retarded, and coating reduced percentage of weight loss during storage HWD combined with 1.0% chitosan was the best treatment which could reduce the percentage of weight loss and maintain the color quality in the lime peel Therefore, in order to evaluate the influence of combined treatments on quality

of lime fruit, the study continued a combination of the best treatment in experiments 1 and 2 with modified atmosphere packaging (PE bags and Active bags) stored at 13 o C for 20 days The treatment combined with Sta-Fresh sealed in active bag induced a retarding chlorophyll content in both chlorophyll a and b Fruits treated in hot water dipping and Sta-Fresh has brought positive effects on peel colour, content of titratable acid, respiration rate and pitting

of the lime peel Combination of hot water treatment and Sta-Fresh was recommended to effectively controlling chlorophyll degradation and the quality of Thai lime fruit during storage

atmosphere packaging, chlorophyll degradation

Date of submission 26/06/2017

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ACKNOWLEDGEMENT

I would like to express my appreciation and gratitude for the assistance of those who contributed to the completion of this study First of all, I would like to sincerely express my thanks to my supervisor, Assoc Prof Dr Apiradee Uthairatanakiji, who gave me a great opportunity to do the internship at King Mongkut’s University of Technology Thonburi, Thailand, whose understanding, guidance and support I am grateful to my co-advisor Ms Trinh Thi Chung of Faculty of Biotechnology and Food Technology, Thai Nguyen University of Agriculture and Forestry, Vietnam, for her support, encourage and help Thanks for being my great teacher

Besides my advisor, I would like to thank my instructor, Ms Chalida Cholmaitri for your guidance, experience, thanks for helping me all the time when I was doing my internship And I am grateful to my special friend, Ms Esther Yap Shiau Ping Thanks for your helping, suggestions and sharing your great experience, both academic and non-academic

My sincere thanks also goes to all staff members from physiological laboratory and from department of Postharvest Technology Division, School of Bioresources and Technology, King Mongkut’s University of Technology Thonburi, Thailand I would like to thank all sister and brother from Vietnam and all Vietnamese friends, for their kindness, encourage, valuable advises and assistance during my stay in Thailand

Likewise, word could not express my sincerest appreciation to all teachers of Postharvest Technology and Faculty of Biotechnology and Food Technology, Thai Nguyen University of Agriculture and Forestry, Vietnam, for their knowledge, guidance, supported my education

Last but not the least, I would like to thank my family: my parents and my elder sister for supporting me spiritually throughout internship course and my life in general

To all these people and others, thank you

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TABLE OF CONTENTS

ABSTRACT i

ACKNOWLEDGEMENT ii

TABLE OF CONTENTS iii

LIST OF FIGURES AND TABLES iv

LIST OF ABBREVIATIONS x

PART 1 INTRODUCTION 1

1.1 Research rationale 1

1.2 Problem statement and justification 2

1.3 Objectives 7

1.4 Expected benefit 8

PART 2 MATERIALS AND METHODS 9

2.1 Fruit supply and handling 9

2.2 Experimental design 9

2.3 Analytical procedures 11

PART 3 RESULT AND DISCUSSION 13

3.1 Experiment 1: Effect of hot water treatment combined with three Sta-Fresh 8711 concentration on yellowing of lime fruit 13

3.2 Experiment 2: Effect of hot water treatment combined with various chitosan concentration on de-greening of lime during storage 20

3.3 Experiment 3: Effect of hot water treatment combined with edible coating and modified atmosphere packaging on yellowing of lime fruit 25

PART 4 CONCLUSION AND RECOMMENDATION 42

REFERENCES 44

APPENDICES 50

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LIST OF FIGURES AND TABLES

Figure 1 The chlorophyll degradation pathway of higher plants (Zhang et al., 2008) 3

Figure 2 Visual peel color changes in lime fruit when non-treated and treated with hot water (HWT) at 50oC for 5 minutes and combined with various Sta-Fresh 8711 concentration under room temperature 13Figure 3 Changes in hue angle value of peel treated with hot water at 50oC for 5 minutes, hot water combined with various Sta-Fresh concentration (1.0%, 5.0%, 10.0%) and non-treated fruits (** = P<0.01, * = P<0.05, ns = P>0.05) 14Figure 4 Changes in L* value of peel treated with hot water at 50oC for 5 minutes, hot water combined with various Sta-Fresh concentration (1.0%, 5.0%, 10.0%) and non-treated fruits (* = P<0.05) 15Figure 5 Changes in a* value of peel treated with hot water at 50oC for 5 minutes, hot water combined with various Sta-Fresh concentration (1.0%, 5.0%, 10.0%) and non-treated fruits 16Figure 6 Changes in b* value of peel treated with hot water at 50oC for 5 minutes, hot water combined with various Sta-Fresh concentration (1.0%, 5.0%, 10.0%) and non-treated fruits (* = P<0.05) 16Figure 7 Changes in C* value of peel treated with Hot water at 50oC for 5 minutes, hot water combined with various Sta-Fresh concentration (1.0%, 5.0%, 10.0%) and non-treated fruits (* = P<0.05) 17Figure 8 Changes in weight loss of lime fruit treated with hot water at 50oC for 5 minutes, hot water combined with various Sta-Fresh concentration (1.0%, 5.0%, 10.0%) and non-treated fruits (** = P<0.01) 18Figure 9 Visual peel color changes in lime fruit when non-treated and treated with hot water (HWT) at 50oC for 5 minutes and combined with various Chitosan concentration under room temperature 20Figure 10 Changes in hue angle value of peel treated with hot water at 50oC for 5 minutes, hot water combined with various Chitosan concentration (0.5%, 1.0%, 2.0%) and non-treated fruits 21

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Figure 11 Changes in L* value of peel treated with hot water at 50oC for 5 minutes, hot water combined with various Chitosan concentration (0.5%, 1.0%, 2.0%) and non-treated fruits 21Figure 12 Changes in a* value of peel treated with hot water at 50oC for 5 minutes, hot water combined with various Chitosan concentration (0.5%, 1.0%, 2.0%) and non-treated fruits 22Figure 13 Changes in b* value of peel treated with hot water at 50oC for 5 minutes, hot water combined with various Chitosan concentration (0.5%, 1.0%, 2.0%) and non-treated fruits 23Figure 14 Changes in weight loss treated with hot water at 50oC for 5 minutes, hot water combined with various Chitosan concentration (0.5%, 1.0%, 2.0%) and non-treated fruits 24Figure 15 Visual peel color changes in lime fruits within 20 days of storage at 13oC 26Figure 16 Changes in Hue angle value of peel treated with hot water combined with edible coating and non-heat treated kept in PE and Active bags at 20 storage days (** = P<0.01) 27Figure 17 Changes in L* value of peel treated with hot water combined with edible coating and non-heat treated kept in PE and Active bags at 20 storage days (** = P<0.01, * = P<0.05) 28Figure 19 Changes in a* value of peel treated with hot water combined with edible coating and non-heat treated kept in PE and Active bags at 20 storage days (** = P<0.01) 29Figure 20 Changes in b* value of peel treated with hot water combined with edible coating and non-heat treated kept in PE and Active bags at 20 storage days (** = P<0.01, * = P<0.05) 29Figure 21 Changes in C* value of peel treated with hot water combined with edible coating and non-heat treated kept in PE and Active bags at 20 storage days (** = P<0.01) 30

Figure 22 Changes in chlorophyll a content of peel treated with hot water combined

with edible coating and non-heat treated kept in PE and Active bags at 20 storage days (** = P<0.01, * = P<0.05) 32

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Figure 23 Changes in chlorophyll b content of peel treated with hot water combined with edible coating and non-heat treated kept in PE and Active bags at 20 storage days (** = P<0.01) 33Figure 24 Changes in total chlorophyll content of peel treated with hot water combined with edible coating and non-heat treated kept in PE and Active bags at 20 storage 20 days (** = P<0.01, * = P<0.05) 34Figure 25 Changes in respiration of lime fruit treated with hot water combined with edible coating and non-heat treated kept in PE and Active bags at 20 storage days (** = P<0.01, * = P<0.05) 35Figure 26 Changes in titratable acidity of lime fruit treated with hot water combined with edible coating and non-heat treated kept in PE and Active bags at 20 storage days 37Figure 27 Pitting area in the peel of fruits treated with Sta-Fresh sealed in PE bags and stored at 13oC during storage 38Figure 28 Changes in pitting area in the peel of lime fruit treated with hot water combined with edible coating and non-heat treated kept in PE and Active bags at 20 storage days (** = P<0.01) 394.3.6 Diseases severity 40Figure 29 Visual of diseases severity in the peel of lime fruit within 20 days of storage

at 13oC 40Figure 30 Changes in diseases severity in the peel of lime fruit treated with hot water combined with edible coating and non-heat treated kept in PE and Active bags at 20 storage days 40Table 1 Effect of hot water treatment (HWT) at 50oC for 5 minutes combined with various Sta-Fresh 8711 concentrations on Hue angle values of lime peel stored at room temperature (25oC) for 6 days 50Table 2 Effect of hot water treatment at 50oC for 5 minutes combined with various Sta-Fresh 8711 concentrations on L* values of lime peel stored at room temperature (25oC) for 6 days 51

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Table 3 Effect of hot water treatment at 50oC for 5 minutes combined with various Fresh 8711 concentrations on a* values of lime peel stored at room temperature (25oC) for 6 days 52Table 4 Effect of hot water treatment at 50oC for 5 minutes combined with various Sta-Fresh 8711 concentrations on b* values of lime peel stored at room temperature (25oC) for 6 days 53Table 5 Effect of hot water treatment at 50oC for 5 minutes combined with various Sta-Fresh 8711 concentrations on C* values of lime peel stored at room temperature (25oC) for 6 days 54Table 6 Effect of hot water treatment at 50oC for 5 minutes combined with various Sta-Fresh 8711 concentrations on percentage of weight loss of lime fruits stored at room temperature (25oC) for 6 days 55Table 7 Effect of hot water treatment (HWT) at 50oC for 5 minutes combined with chitosan on hue angle value of lime peel stored at room temperature (25oC) for 6 days 56Table 8 Effect of hot water treatment at 50oC for 5 minutes combined with chitosan L* value of lime peel stored at room temperature (25oC) for 6 days 57Table 9 Effect of hot water treatment at 50oC for 5 minutes combined with chitosan on a* value of lime peel stored at room temperature (25oC) for 6 days 58Table 10 Effect of hot water treatment at 50oC for 5 minutes combined with chitosan on b* value of lime peel stored at room temperature (25oC) for 6 days 59Table 11 Effect of hot water treatment at 50oC for 5 minutes combined with chitosan on a* value of lime peel stored at room temperature (25oC) for 6 days 60Table 12 Effect of hot water treatment at 50oC for 5 minutes combined with chitosan on percentage of weight loss of lime fruits stored at room temperature (25oC) for 6 days 61Table 13 Effect of hot water treatment (HWT) at 50oC for 5 minutes combined with edible coating and modified atmosphere packaging on total chlorophyll content of lime fruits stored at 13oC for 20 days 62Table 14 Effect of hot water treatment at 50oC for 5 minutes combined with edible coating and modified atmosphere packaging on total carotenoid content of lime fruits stored at 13oC for 20 days 63

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Table 15 Effect of hot water treatment at 50oC for 5 minutes combined with edible coating and modified atmosphere packaging on hue angle value of peel of lime fruits stored at 13oC for 20 days 64Table 16 Effect of hot water treatment at 50oC for 5 minutes combined with edible coating and modified atmosphere packaging on L* value of peel of lime fruits stored at

13oC for 20 days 65Table 17 Effect of hot water treatment at 50oC for 5 minutes combined with edible coating and modified atmosphere packaging on a* value of peel of lime fruits stored at

13oC for 20 days 66Table 18 Effect of hot water treatment at 50oC for 5 minutes combined with edible coating and modified atmosphere packaging on b* value of peel of lime fruits stored at

13oC for 20 days 67Table 19 Effect of hot water treatment at 50oC for 5 minutes combined with edible coating and modified atmosphere packaging on C* value of peel of lime fruits stored at

13oC for 20 days 68Table 20 Effect of hot water treatment at 50oC for 5 minutes combined with edible coating and modified atmosphere packaging on respiration rate of lime fruits stored at

13oC for 20 days 69Table 21 Effect of hot water treatment at 50oC for 5 minutes combined with edible coating and modified atmosphere packaging on titratable acidity of lime fruits stored at

13oC for 20 days 70Table 22 Effect of hot water treatment at 50oC for 5 minutes combined with edible coating and modified atmosphere packaging on pitting area of lime fruits stored at 13oC for 20 days 71Table 23 Effect of hot water treatment at 50oC for 5 minutes combined with edible coating and modified atmosphere packaging on disease severity of lime fruits stored at

13oC for 20 days 72Table 24 Effect of hot water treatment at 50oC for 5 minutes combined with edible

coating and modified atmosphere packaging on chlorophyll a content of lime fruits

stored at 13oC for 20 days 73

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Table 25 Effect of hot water treatment at 50oC for 5 minutes combined with edible

coating and modified atmosphere packaging on chlorophyll b content of lime fruits

stored at 13oC for 20 days 74

x

LIST OF ABBREVIATIONS

commercial species of citrus available such as orange (C sinensis (L.) Osb.), mandarin and tangerine (C unshiu Marc and C reticulata Blanco), lemon (C Limon) and lime (C aurantifolia Swingle, C Latifolia), grapefruit (C paradisi Macf.), pomelo (pummelo) (C grandis Osb.), kumquat (Fortunella spp.), Citron (C medica), Hassaku

(C Hassaku tanaka), Calamondin (C madurensis loureiro) (Ladanyia et al., 2010)

Lime fruit belongs to the genus Citrus and family Rutaceae The fruit is

classified as a hesperidium or berry of special structure There are two kinds of acid

lime: low acid (sweet) lime (C limettioides Tanaka) cultivars such as ‘Indian sweet lime’ (Palestine lime) and acid (sour) lime with cultivars such as ‘Thai’ lime (C

aurantifolia swingle), also known as Mexican or West Indian lime with small fruit size

(Ladanyia et al., 2010) Lime (C aurantifolia Swingle) is a Citrus species, which is a

popular ingredient in Mexican, Vietnamese and Thai cuisine Lime has small, round, ovate or short-elliptical fruits; present a very thin rind; smooth surface; and a greenish-yellow color at maturity The flesh is juicy and highly acidic with a distinctive aroma

(Rivera-Cabrera et al., 2010) The fruit is used in nearly every home in the tropics,

mainly to flavor food, but also to prepare drinks and for a variety of medicinal applications The rich flavor and acidic taste make lime a favorite for hot and spicy dishes, either fresh or in the form of pickles and sauces It is refreshing qualities come

in the form of lime juice, lime tea and in use on other fruit such as papaya According

2

to the US Department of Agriculture National Nutrient Database (2016), the lime fruits are nutrient-dense foods that can be a good sources of vitamin C, carbohydrates,

including dietary fiber, and many vitamins and minerals (Chaisawadi et al., 2005)

reported of the possibility of using medicinal herbs from Thai food ingredients as natural antimicrobial agents Furthermore, lime peels showed high sensitivity for all

studied microbial such as Bacillus cereus, Salmonella typhi, and Staphylococus

aureus In Thailand, lime (C aurantifolia Swingle), locally known as ‘Ma-nao’, has

been used for providing a sour taste and its unique fragrance to enhance overall flavor and aroma in various Thai foods It is also used in Thai traditional medicine

(Pranamornkith, 2009)

For countries with tropical climates, like Thailand, citrus production is found on all types of soil and under a wide range of climatic condition (Sethpakdee, 1997) This because lime is an economically significant horticulture crop and the harvesting season

is mainly in July to September (Pranamornkith et al., 2005) Some large commercial

orchards were found in lowland areas, especially in the central plain which is a major citrus growing area Trees can be harvested three or four times a year Nevertheless, it

is difficult to protect trees from insect pests in the warm temperatures throughout the year (Jungbluth, 2000) The following statistics of FAOSTAT (2013) reported that, Thai lemons and limes production was 132.170 tons (rank 17th in the world) and the yield is increasing every year However, the quantity of limes available varies from season to season and in the dry season (February to April) the price of limes can increase by as much as five to ten times In contrast, the price of limes is very low in

the wet season because there is a surplus of fruits in the market (Chaisawadi et al., 2005; Uthairatanakij et al., 2006) Therefore, this study aims to look at the effect

different postharvest treatments on the quality of lime fruits to ensure continuous supply of lime fruits in the market

1.2 Problem statement and justification

All fruits, vegetables and root crops are living biological organisms, having a respiratory system, similar to that of humans They continue their living processes after harvest (Gaetano Paltrinieri et al., 2002) The interaction of metabolic and

3

environmental factors are responsible for many postharvest deteriorations Among the main causes of wastage are the following: General senescence, water loss, diseases and pests; physical damages (mechanical injury), injuries from temperature effects (chilling injuries, CI), and other causes Although the loss of green color in senescent leaves and ripening fruits is a natural phenomenon but the price of lime fruit is directly affected by chlorophyll degradation Since limes are commercially marketed as green fruit, they are harvested when the skin is still green Full with highly aromatic compounds, lime fruit is important in some countries where it is processed to yield lime oil and lime juice Most of the customer in many countries prefer green lime to yellow lime (Thompson, 2003) In addition, the quality of lime fruit deteriorates

quickly after harvest (Kaewsuksaeng et al., 2015) Therefore the maintenance of green

color in the peel of lime fruit is necessary

Figure 1 The chlorophyll degradation pathway of higher plants (Zhang et al., 2008)

Occurrence of a yellow color in plant leaves denotes chlorophyll breakdown that is a visible symptom of leaf senescence and is often also observable during

postharvest storage of fruit and vegetables under ambient temperature (Srilaong et al.,

2011)

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Chlorophyll degradation is mediated through several processes such as action of enzyme chlorophyllase, enzymatic oxidation and photodegradation The process of chlorophyll degradation which occurs during postharvest storage of horticultural crops has been suggested to portray the following putative pathway The major steps of the chlorophyll catabolic pathway had been elucidated during the last two decades

(Hörtensteiner, Stefan, 2006; Hörtensteiner, S et al., 2004) The pathway starts with the removal of the phytol moiety from the chlorophyll a molecule by chlorophyllase, producing the first green breakdown product, chlorophyllide a Then, after the

removal of the central Mg2+ form chlorophyllide by Mg-dechelatase, the porphyrin macrocycle of pheophorbide a is oxygenolytically cleaved by the joint action of

pheophorbide a oxygenase (PaO) and red chlorophyll catabolite reductase The

product, a primary fluorescent catabolite, is further con-verted to the final fluorescent chlorophyll catabolites The pathway was designated the PaO pathway due

non-to the critical function of PaO enzyme Based on the fact that all the non-fluorescent

chlorophyll catabolites were identified as the derivatives of chlorophyll a, it was proposed that the conversion of chlorophyll b to chlorophyll a is required for the degradation of chlorophyll b via PaO pathway (Hörtensteiner, Stefan, 2006) chlorophyll b reductases were suggested to be the enzymes responsible for the conversion (Zhang et al., 2008) Therefore, delaying the chlorophyll degrading

enzymes could be a useful method to controlling the chlorophyll breakdown in plant The measures to control chlorophyll breakdown to reach or maintain the required color

of fruits in the postharvest handling chain are different Since the present measures may have different effects on chlorophyll breakdown in various fruits, the handling of

other fruits needs suitable selection and application (Zhang et al., 2008)

Effect of hot water treatment to postharvest quality of fruit and vegetable were evaluated There are three methods used such as hot water, vapor heat and hot air Hot water dips to control decay are often applied for a few minutes whereby the temperature are used is higher than those for hot air, while, vapor heat only transfers heat to the surface of the commodity (Lurie, 1998) However, hot air produces heat slower than hot water or vapor heat, although forced hot air will heat produce faster than a regular heating chamber

treatment by immersion of the citrus fruit at 52°C for one minute slowed the rate of rot

development by approximately 15% in litchi fruit (Olesen et al., 2004), immersion of

Broccoli in 50oC for two minutes to extended the shelf life of fresh Broccoli (Forney,

1995)and also improve the storage quality of sweet pepper (Fallik et al., 1999)

Alongside, different temperatures could reduce enzymes active and some heat

treatment could delay ripening as reported by (Khademi et al., 2013) on persimmon whereby hot water treatment reduced the fresh browning The study of (Tian, M et al.,

1996) indicated treatment at 47oC for 7.5 min consistently reduced yellowing for up to

5 days In addition, heat treatment on commodities also suppressed the activities of

chlorophyll oxidase in broccoli treated at 50 °C for 2 hours (Yamauchi et al., 2002) Specifically in lime, (Kaewsuksaeng et al., 2015) reported that hot water treatment at

50oC for 5 minutes could be an useful method to delay chlorophyll degradation and to maintain postharvest quality in mature green lime in storage

Application of edible coating and films have been shown to improve food quality (Elizaneth A., et al., 2002) Edible coatings are substances applied to the

exterior of food so that the final product is fit for consumption (Baldwin et al., 2011)

According to Attila E Pavlath and William Orts (2009) edible films and coatings, such

as wax on various fruits, have been used for centuries to prevent loss of moisture and

to create a shiny fruit surface for aesthetic purposes These practices were accepted long before their associated chemistries were understood, and are still carried out in the present day The term, edible film, has been related to food applications only in the past 50 years The edible based on feature natural waxy coating called a cuticle of

plant (Baldwin et al., 2011) It could retard respiration, ethylene rate, water loss,

reduce weight loss, firm loss, ethanol fermentation, transpiration, control interval gas composition, de-color

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For example, application of chitosan coating on enzymatic browning and decay

during postharvest storage of litchi (Litchi chinensis Sonn.) fruit (Quantick et al., 1997) and possible control of postharvest diseases of tomato fruit (Tian, S et al.,

2007) were demonstrated Edible chitosan coating effectively prolongs the quality

attributes and extends the shelf life of sliced mango fruit (Chien et al., 2007), peels of litchi fruit (Jiang et al., 2004) and red kiwifruit (Kaya et al., 2016) Furthermore, the

combination of hot water and chitosan treatments is a valid strategy to improve the existing ones that were already used in controlling postharvest decay of sweet cherries

(Chailoo et al., 2011) In another study of combined effects of postharvest heat treatment and chitosan coating on quality of fresh-cut mangoes (Magifera indica L.)

indicated that both hot water dipping at 50oC for 30 minutes and chitosan coating, either alone or combined, did not a ect the taste and the flavor of mangoes slices but maintained firmness and color for 9 days at 6oC The chitosan coating was used as

antimicrobial proprieties (Djioua et al., 2010)

According to the information of Jirakorn Company (www.jirakorn.com) which

is the producer of Sta-Fresh 8711 Sta-Fresh product is a vegetable oil based coating as well as chitosan which is an edible coating It is ready to use the product formulated from food-grade ingredients that are approved by Title 21 of the code Federal Regulation by the U.S Food and Drug Administration (FDA) Effect of Sta-Fresh coating on storage life of mango cv Namdokmai were also evaluated The fruits were last perceived to be marketable after 25 days of storage Uncoated fruits kept for 20

days in storage (Kaewchana et al., 2003) Additionally, lime fruit coated with

Sta-Fresh no.360 mix with GA3 at 0, 20, 100 and 500 ppm, stored at 0.03, 1 and 5 percent

CO2 could prolong their storage life up to 60 days (Kanlayanarat et al., 2003)

Furthermore, edible coatings are environmental friendly technology that are applied on many products to control cuticle transpiration, gas exchange or oxidation processes Edible coatings can provide an additional protective coating and can also give the same effect as modified atmosphere storage in modifying internal gas composition (Dhall, 2013) Consequently, a combination of hot water and edible coating treatments could be an effective method to retain postharvest quality of lime fruits during storage

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Packaging is increasingly important as part of the communicator role to reach the consumer through printing and package appearance In addition, new packaging technologies are creating advancements in barrier polymers, improved sealant polymers, and abuse properties The composition of the storage atmosphere can significantly affected to the storage life of horticultural crops Modified atmosphere packing (MAP), a technique used to prolong the shelf life of fresh or minimally processed foods, refers to the development of an MA around the product through the use of permeable polymeric films MAP is used with various types of products, where the mixture of gases in the package depends on the type of product; packaging materials and storage temperature It can be broadly defined as any process that significantly changes the environment around the product from the normal composition of air in a package (Yahia, 2009) MAP can become an important supplement to other postharvest technologies for the quality maintenance of fruit and vegetables in both the developed and developing countries

Application of MAP have been done on the quality of fruits and vegetables such as the combination of wax and packaging to prolong the post-harvest preservation

of acid limes (Caron et al., 2015); Reduction of postharvest rind disorders in citrus fruit by modified atmosphere packaging (Porat et al., 2004); the effects of various

postharvest treatments on quality changes in main- and late-season New Zealand lime

fruit (Pranamornkith et al., 2005) and the study of Uthairatannakiji (2006) reported

that controlled atmosphere storage retained physiological changes of lime fruit better

than control treatment (Uthairatanakij et al., 2006)

Therefore, this study aims to look at the effect different postharvest treatments

on the quality of lime fruits to ensure continuous supply of lime fruits in the market

1.3 Objectives

• To study the effect of hot water treatment combined with various Sta-Fresh

8711 concentration on yellowing of lime fruit

• To study the effect of hot water treatment combined with chitosan on yellowing

of lime fruit

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• To determine the effect of hot water treatment combined with edible coating and modified atmosphere packaging (MAP) on storage life and quality of lime fruit

1.4 Expected benefit

• To extend the knowledge regarding effect of hot water treatment combined with

Sta-Fresh 8711 coating on yellowing of lime fruit during storage

• To improve the beneficial effects of hot water treatment combined with

chitosan coating on de-greening of lime fruit

• To discern the effect of hot water treatment combined with edible coating and modified atmosphere packaging on retardation of chlorophyll breakdown and other physiological processes through which this study will widen an understanding how the treatments result in control of chlorophyll degradation in

lime fruit

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PART 2 MATERIALS AND METHODS

2.1 Fruit supply and handling

Mature green Thai limes (C aurantifolia Swingle) fruit were purchased from

Ratchaburi Province, Thailand Fruit were transported to the laboratory at King Mongkut’s University of Technology Thonburi Fruit were classified for uniformity in maturity, size, shape, peel color, and blemish

The treatments were as following:

1) Non treated fruit (control)

2) Hot water treatment at 50oC for 5 minutes (HWT)

3) HWT + coated with Sta-Fresh 8711 at 1.0%

4) HWT + coated with Sta-Fresh 8711 at 5.0%

5) HWT + coated with Sta-Fresh 8711 at 10.0%

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2.2.2 Experiment 2: Effect of hot water treatment and chitosan coating on the yellowing of lime fruit

Fruits described in 2.1 were used in this experiment Fruit were subjected

to hot water at 50oC for 5 minutes, after hot water treatment, the samples were immediately immersed in ice water 10oC to cool down for 10 minutes Original chitosan solution 2% were diluted by distilled water to series of 0.5%, 1.0%, 2.0% concentrations Thereafter, samples were dipped for 1 minute into various chitosan concentration and then air-dried at room temperature Untreated fruits were used as the control After complete dried, the fruits were stored at 25oC Samples from each treatment were measured the peel color and weight loss every

day until de-greening in the peel of lime

The treatments were as following:

1) Non-treated fruits

2) Hot water treatment at 50oC for 5 minutes (HWT)

3) HWT + coated with chitosan at 0.5%

4) HWT + coated with chitosan at 1.0%

5) HWT + coated with chitosan at 2.0%

2.2.3 Experiment 3: Effect of hot water treatment combined with chitosan and Sta-Fresh 8711 coating and modified atmosphere packaging (MAP) on storage life and quality of lime fruit

In this experiment, the best treatment to retain the best characteristics of lime fruit from experiment 1 and 2 had been chosen Packaging used in this experiment were polyethylene film bags (0.03 mm in thickness) with perforated (6 holes) and active bags with the top folded over The experiment design was a complete randomized design with three replicates Each replicate contained 4 fruits (approximately 180 gram/bag) All treatments were kept at 13°C in dark Samples were withdrawn for analysis at four days interval and storage period being 20 days

The treatments were as follows:

1) Non-heat treated fruits

2) Non-heat treated fruits + Polyethylene (PE) bags

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3) Non-heat treated fruits + Active bags

4) Hot water treatment at 50oC for 5 minutes (HWT) + Sta-Fresh + PE bags

2.3 Analytical procedures

2.3.1 Determination peel of color

A Minolta chromameter (model CR-200, Minolta Camera Co., Ltd, Osaka, Japan) was used for measuring fruit peel color during storage Peel colour of fruit were measured Hunter L*, a*, b*, C* values Hue angle of 0, 90, 180 and 270 degrees showed corresponding red-purple, yellow, bluish-green and blue color

2.3.2 Weight loss

Every lime fruit in the same selected packages for each treatment was determined by weighing at the initial weight and during storage and then calculating weight loss by weight differences Results were expressed as the percentage of weight loss (%)

Weight loss (%) = (The initial weight of fruit – The final weight of fruit) ×100

The initial weight of fruit

2.3.3 Determination of respiration rate

Two fruits were placed in a 240 ml air-tight plastic container, incubated at room temperature for 1 hour A 1 ml sample of headspace gas was taken by hypodermic syringe and injected into the LI-7000 CO2/H2O Analyzer (LI-COR Biosciences) with nitrogen used as a carrier gas

2.3.4 Determine of Chlorophyll content

Chlorophyll content was determined according to Moran (1982) A sample

of 0.2 g of lime fruit peel was homogenized in 10 ml of N, N-dimethylformamide

and kept in the dark under 4oC for 24 hours to elute the chlorophyll pigments completely Thereafter, the mixture was filtered through Whatman No 1 filter

paper The extracted filtrate was assayed for chlorophyll a, chlorophyll b, and

12

total chlorophyll content with a spectrophotometer (UV-1800, SHIMADZU,

Japan) at 663 and 647 nm for chlorophyll a and chlorophyll b respectively:

Chlorophyll content was calculated using Arnon (1949) equations:

Chlorophyll a = (12.70A663 - 2.79A647) × dilution factor/1000

Chlorophyll b = (20.70A647 - 4.62A663) × dilution factor/1000

Total chlorophyll = (20.20A663 + 8.02A647) × dilution factor/1000

Where, A663 = OD value at 663 nm

A647 = OD value at 647 nm The chlorophyll content was expressed and reported as mg/100 g FW

2.3.5 Total acids (TA)

The titratable acidity (TA) of fruit juice was determined by titrating 1 ml of fruit juice diluted 10 times with distilled water against 0.1 N NaOH, using 1-2 drops of 1% (v/v) phenolphthalein as an indicator to light pink color as end-point Titratable acidity was calculated as below formula and expressed as the percentage of

the citric acid content (meq Citric acid = 0.064) (Opio et al., 2015)

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PART 3 RESULT AND DISCUSSION

3.1 Experiment 1: Effect of hot water treatment combined with three Fresh 8711 concentration on yellowing of lime fruit

Sta-Lime (C aurantifolia Swingle) is widely consumed at the green stage

Unfortunately, de-greening due to the chlorophyll degradation happen during postharvest handling As with many products, the price of the fruit is strongly

dependent on its availability and quality characteristics (Pranamornkith et al., 2005)

Moreover, the external appearance of lime fruit is used by consumers as an indication

of quality (Miller, 1946) The influence of heat treatment and edible film on the quality

of fruits were demonstrated In this experiment, effect of postharvest hot water treatment combined with various Sta-Fresh 8711 concentration on yellowing of lime fruit under room temperature within 7 days of storage were evaluated

3.1.1 Effect of hot water treatment combined with various Sta-Fresh 8711 concentration on color change in lime fruit peel

Figure 2 Visual peel color changes in lime fruit when non-treated and treated with hot water (HWT) at 50oC for 5 minutes and combined with various Sta-Fresh 8711

concentration under room temperature

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The color hue of pigments is also expressed by the hue angle H° that has interval 0° – 360°, and for red colour, it has value 350° – 35°, for orange 35° – 70°, for yellow 70° – 105°, for green 105° – 195°, for blue 195° – 285° and for violet 285° – 350°

In this present study, hue values in lime fruit decreased during storage in all samples and this was shown in the change in color from green to yellow without a significant difference among all treatments in 6 days of storage (Figure 3) The hue angle values corresponded with the appearance of color in lime fruit as the period progressed (Figure 2) Nevertheless, the graph showed that on day 4 and the days following all of the treated samples maintained better hue value compared to the non-treated fruits Moreover, the result also indicated that the rate of change in the Sta-Fresh 10.0% treated (from 119.91 to 115.44) is lower than the non-treated fruits (from 118.94 to 111.02) Overall, the combination of hot water treatment at 50oC for 5 minutes with Sta-Fresh 10.0% retained the green color in the peel of lime higher than other treatments

HWT 50oC 5min,StaFresh 1.0%

HWT 50oC 5min,StaFresh 5.0%

HWT 50oC 5min,StaFresh 10.0%

L* value is a skin color measurement, and the lightness coefficient L* ranges from black = 0 to white = 100 According to the result was shown in the graph (Figure 4), the changing L* values of peel were different between various samples on 6 days

15

of storage associated with yellowing of fruit peel There was no significant difference among all treatments in the first 3 days of storage Thereafter, the fruit treated with hot water combined with various Sta-Fresh concentration (1.0, 5.0, 10.0%) maintained a considerably better (P<0.05) L* value compared to the untreated fruit and hot water treatment Furthermore, the L* value in the treatment of hot water combined with sta-fesh 10.0% increased slightly (from 43.99 to 45.68); in contrast, that is non-treated sample was increased more rapidly (from 46.01 to 53.85) Hence, the L* value was retained the best by Sta-Fresh 10.0% (P<0.05)

HWT 50oC 5min,StaFresh 5.0%

HWT 50oC 5min,StaFresh 10.0%

The parameter of a* value has no specific numerical limits On the horizontal axis, positive a* indicates a hue of red-purple and negative a* of bluish-green

According to the result (Figure 5), a* values decreased with no significant difference among samples during storage There were only slightly changes in first 4 days of storage and after that a reducing a* value in all treatments were seen Nevertheless, both the treatments of hot water combined with Sta-Fresh 10% (from15.57 to 16.49) and non-treated fruits (from 15.02 to 15.94) were effective in improving a* values within 6 days of storage

*

HWT 50oC 5min,StaFresh 5.0%

HWT 50oC 5min,StaFresh 10.0%

HWT 50oC 5min,StaFresh 5.0%

HWT 50oC 5min,StaFresh 10.0%

On the axis, positive b* indicates yellow and negative b* blue The b* values of peel is increased every day during storage (Figure 6) which corresponded with the changing of color in lime fruit (Figure 2) Although, there were no significant difference among treatments except for day 5 (P<0.05) where b* value increased more

*

17

rapidly in fruit of non-treated However, the combination of HWT and Sta-Fresh were comparable more effective than non-treated and HWT fruits in retarding b* value loss The graph showed that the treatment with Sta-Fresh 10.0% had the best inhibition efficiency in increasing b* value (from 27.12 to 34.01), whereas, the non-treated fruit lost the highest b* value (from 27.29 to 41.27)

HWT 50oC 5min,StaFresh 5.0%

HWT 50oC 5min,StaFresh 10.0%

Value C* (Chroma) determines the saturation of the colour and is calculated according to the formula C* = (a*2 + b*2)1/2

In the present study, changes in C* values of peel is shown in Figure 7 that increased in all fruits over storage time Changing values had no significant difference among treatments on first the 3 days of storage The fruits treated with Stra-fresh were comparably more effective than non-treated fruits and hot water treatment However, fluctuation in treatment of Sta-Fresh differ among all days of storage Another key point, the treatment of hot water combined with Sta-Fresh 10.0% observed a reduction considerably (P<0.05) on day 3 and day 5 compared to non-treated fruits and single hot water treatment Whereas, the C* values increased more rapidly in non-treated fruits (from 31.16 to 44.32) Otherwise, maintaining C* value of Sta-Fresh 10.0% treatment showed only a slight increasing except for day 6

*

*

18

Yellowing of lime fruits occurs rapidly at ambient temperatures At 25oC, lime turns yellow within 3 or 4 days of storage In this study, the result was similar to what

was reported in another study (Kaewsuksaeng et al., 2015) Yellowing also was

reflected by a decline in the hue angle of the lime fruits The treatment of HWD and coating by 10.0% Sta-Fresh could maintain higher hue angle value than other treatments during storage Furthermore, the increased in L* value and Chroma (C*) was also inhibited markedly in the combination of HWD and 10.0% Sta-Fresh The

color values of lime peel agreed to those reported in other studies on lime (C

aurantifolia Swingle cv Paan) (Opio et al., 2015; Ohnmar Win et al., 2006)

3.1.2 Weight loss percentage

HWT 50oC 5min,StaFresh 5.0%

HWT 50oC 5min,StaFresh 10.0%

Weight loss is a quality parameter that is associated with the physiology of fruit during storage In this experiment, the percentage of weight loss increased with no sinigficant difference among all samples on day 3 until last day of storage (Figure 8) Both day 1 and 2 were shown to have a significant difference between the fruits surface coating with various Sta-Fresh concentration and the fruit non-treated with Sta-Fresh Nonetheless, all of the combined treatments were slightly more effective than the non-treated fruits and hot water treatment in retarding the weight loss except for that of the treatment of Sta-Fresh 10.0% which increased highest after 6 days of

**

**

19

storage Whereas, both Sta-Fresh 1.0% and 5.0% showed similar increased with storage, but Sta-Fresh 5.0% had a slightly lower weight loss than other treatment until the last day of storage Overall, the result in this study showed fluctuation in weight loss during 6 days of storage at room temperature, with seemingly no clear effect observed in the progress of storage of lime fruit

The loss of water was the most obvious physical change occurring in citrus fruits after harvest This resulted in wilting or shriveling of the fruit accompanied by accompanying a decrease in weight and volume This type of change affected only the appearance of the fruit and rendered it generally unattractive, although it may be accompanied by chemical or physiological changes which cause a loss of flavor and aroma (Miller, 1946) Hence, reducing water loss from fruit during storage or ripening

can help to maintain the quality of fruit (Chien et al., 2007) In this study, the

percentage of weight loss were increased without a significant difference among treatments Compared to the previous findings, the results agreed with the effect of postharvest ethanol vapor treatment delayed chlorophyll degradation and maintained

the quality of Thai lime (C aurantifolia Swingle cv ‘Paan’) fruit (Opio et al., 2015)

The heat treated combined with edible coating were more effective than both treatments of untreated and HWD The combination of hot water dipping and 5.0% Sta-Fresh could retard the percentage of weight loss

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3.2 Experiment 2: Effect of hot water treatment combined with various chitosan concentration on de-greening of lime during storage

Postharvest handling of sour lime (C aurantifolia Swingle) is important to

maintenance quality characteristics Especially, maintenance of the green color in the

peel of lime is a desirable quality attribute during storage (Pranamornkith et al., 2005)

In reality, green peel of lime reduced quickly after harvest Whereas, consumer prefer

green limes because of their greater aroma compound (Srilaong et al., 2011) This

study investigated the efficacy of hot water treatment combined with chitosan coating

on de-greening of lime on 6 days of storage period

3.2.1 Effect of hot water treatment combined with various chitosan concentration

on color change in lime fruit peel

Figure 9 Visual peel color changes in lime fruit when non-treated and treated with hot water (HWT) at 50oC for 5 minutes and combined with various Chitosan concentration under room temperature

In this present study, hue angle values decreased during storage in the all of the samples, whereby the fruits change color from green to yellow (Figure 9) There was

no significant difference among all treatments over storage time (Figure 10) Nevertheless, the result showed clearly that the combined treatment with Chitosan 0.5% decreased more rapidly than others (from 118.21 to 108.82) Whereas, HWT also

21

showed a slight change during storage, but it is still smaller than Chitosan 1.0% Overall, HWT with 1.0% Chitosan retained the high hue angle value (from 119.04 to 114.92)

HWT 50oC 5min, Chitosan 1.0%

HWT 50oC 5min, Chitosan 2.0%

HWT 50oC 5min,Chitosan 1%

HWT 50oC 5min,Chitosan 2%

The result showed in the graph (Figure 11) indicated an increasing L* values in all samples The L* values corresponded with the appearance of color in lime fruit as the period progressed (Figure 9) The chitosan 0.5% treatment had not only higher L*

22

values but increased more rapidly than other treatments Furthermore, the treatment of non-treated and chitosan 2.0% had smaller L* values than chitosan 0.5% treatment In contrast, the L* values increased slowly in both samples treated with chitosan 1.0% and single HWT during storage

Fruit surface color measurement showed that a* values of peel decreased most of the samples in over storage time except for that of the hot water treatment combined with chitosan 0.5% There was no significant difference among all treatments during storage Nevertheless, the treatment combined with Chitosan 2.0% increased a* value (from -15.60 to 14.62) slightly Whereas, the treatment combined with Chitosan 1.0% decreased continuously (from -15.39 to -17.07) during storage Overall, the changing

of a* value was minimized with the combination of Chitosan 2.0% (from 14.57 to 15.46)

-All treatments increased in b* value of peel without a significant difference over storage time (Figure 13) However, the result showed that the increase was more rapid

in both the non-treated fruits and Chitosan 0.5% treatment On the contrary, both the treatment with single hot water and chitosan 1.0% were more effective in preserving

23

the b* value than other treatments The overall results showed that the combination of hot water with chitosan 1.0% could maintain a better b* values than single hot water treatment

HWT 50oC 5minChitosan 1.0%

HWT 50oC 5minChitosan 2.0%

Chlorophyll degradation is an integral part of senescence which is correlated to

the postharvest quality of fruits, particularly the color quality (Zhang et al., 2008) For

acidic fruits like lime, degreening or yellowing is undesirable during storage It is critical to note that the value in use of lime strongly depends on the green color of the peel (Pranamornkith, 2009) In this study, the changes in hue angle of peel declined markedly in the treatment of HWD combined with 1.0% chitosan during storage Likewise, the changes in color parameters of lime fruit such as L* a* b* and C* were evaluated The data also indicated that the combination of HWD and 1.0% Chitosan coating were more effective in controlling degeening as compared to other treatments Similarly, the effectiveness of HWT combined with Chitosan coating in quality of

fresh-cut mangoes and pineapple have been demonstrated (Chailoo et al., 2011; Djioua

et al., 2010) Furthermore, the result also agreed with the research of biochemical and

physiological changes during storage of chlorophyll degradation in lime (C

aurantifolia Swingle cv ‘Paan’) (Ohnmar Win et al., 2006).

3.2.2 Weight loss percentage

HWT 50oC 5min Chitosan 1%

HWT 50oC 5min Chitosan 2%

In this experiment, changes in weight loss are shown in Figure 14 The graph indicated an increased in percentage of weight loss in all treatments during storage There were no considerable difference among treatments Nevertheless, the result showed that weight loss increased rapidly in HWT Whereas, HWT combined with

Chitosan 1.0% was more effective in retarding weight loss than other treatments

As has been noted before, HWT at 50oC for 5 minutes could be a useful method

to delay chlorophyll degradation and to maintain postharvest quality in mature green lime during storage at 25oC (Kaewsuksaeng et al., 2015) Similarly, heat treatment

could reduce Chlorophyll degradation due to the suppression of chlorophyll degrading

enzyme activities (Yamauchi et al., 2002) In addition, application of chitosan coating

effectively increased the postharvest quality and shelf life of citrus (Murcott tangor)

(Chien et al., 2007) Chitosan coating retarded weight loss and the decline in sensory quality and suppressed the increase in activities of PPO and POD (Jiang et al., 2004)

Moreover, the study indicated that Sta-Fresh and SFE coating could extend the shelf

life of mango fruits by 5 days longer than without surface coating (Kaewchana et al.,

2003)

The effect of hot water treatment and edible coating to fruit quality not only showed in the single treatment but the result was also expressed in the combined treatment such as the effect of HWD for 5 minutes at 50oC and 0.6g methanol vapor

25

effectively was evaluated (Opio et al., 2015) Furthermore, the combination of 0.5%

chitosan and HWT at 50oC for 5 minutes after 60 days of storage life showed good

result in comparison to other treatments (Chailoo et al., 2011) Likewise, the study of

combined effects of 50oC for 30 minutes and 0.5% chitosan improved the

antimicrobial effect on the quality of fresh-cut mangoes (Djioua et al., 2010)

The effects of hot water and the edible coating have been demonstrated on the quality

of fruits Although, the combination of HWD and 1.0% Chitosan was the best treatment in retarding the percentage of weight loss in this study but no different pattern of variation among treatments

A key focus in this study was on the influence of lime essential oil (lime EO) which is one of the most important flavoring oils Lime EO consists of a mixture of volatile components basically terpenes (75%), oxygenated compounds (12%), and

sesquiterpenes (3%) (Gamarra et al., 2006) Firstly, the flash point of lime EO is 50oC (122oF, 323K) which means that the temperature of HWT could extract lime EO, and covered the entire surface of the fruit Secondly, the structure of lime EO might be a barrier of linkage between chitosan and cell surface of lime, but it could be an advantage with Sta-Fresh because it is a vegetable oil Thirdly, there are many benefits

from lime EO such as flavor enhancer, antioxidant, and antimicrobial agent (Gamarra

et al., 2006; Cruz-Valenzuela et al., 2016)

3.3 Experiment 3: Effect of hot water treatment combined with edible coating and modified atmosphere packaging on yellowing of lime fruit

From experiments 1 and 2, it was expressed that the combination of heat treatment and edible coating surface effectively delayed the breakdown of chlorophyll

In order to evaluate the influence of combined treatments on the quality of lime fruit, the study continued in combination with modified atmosphere packaging and stored at

13oC for 20 days

Treatment 2: Non-heat treated + polyethylene (PE) bags

Treatment 3: Non-heat treated + Active bags

Treatment 5: HWT + Sta-Fresh + Active bags

Treatment 6: HWT + Chitosan + PE bags

Treatment 7: HWT + Chitosan + Active bags

For the non-heat treated fruits, the changes in hue angle values decreased slightly during the first 16 days of storage Furthermore, the non-heat treated fruits kept in active bags retained higher hue values (118.35) than fruits sealed in PE bags (117.18) and fruits without packaging (115.95) A 20 days of storage, the hue angle in non-heat treated fruits reduced rapidly than heat treated fruits except for that of the treatment of Sta-Fresh sealed in PE bags The hue angle values showed a sharp reduction (P<0.01) in the treatment of Sta-Fresh sealed in PE bags (102.82) whereby the treatment has the lowest rates of hue values over the storage time Whereas, the combination of hot water and Chitosan coating sealed in PE bags showed slight declined in the hue angle values during storage (116.41).

** **

**

The fruit surface color measurement showed that L* values increased continuously in all treatments during storage (Figure 18) It is associated with yellowing of fruit peel in Figure 15 There was no markedly changes on first 4 days of storage, but there were significant difference (P<0.01) among treatments starting from day 8 The result indicated that the non-heat treated fruits had almost higher L* values than heat treated fruit during storage except for the heat treated fruits sealed in PE bags At 20, the L* values increased sharply (P<0.01) in non-heat treated fruits as compared to heat treated combined with surface coating fruits In addition, the L* value for fruits without packaging increased more rapidly than other samples It peaked on day 8 (51.42) and 16 (54.22) In contrast, the HWT combined with Sta-Fresh coating sealed in active bags were more effective in controlling the L* value than the other treatments

In Figure 19 below, a* values changed significantly (P<0.01) in the limes of HWT and Sta-Fresh sealed in PE bags which the treatment increased more rapidly (from -16.58 to -9.33) than other treatments In contrast, the result showed a decrease

in a* values in the non-heat treated fruits and the HWT combined with surface coating

**

**

**

*