Reduction of salt in pork sausages by the addition of carrot fibre or potato starch and high pressure treatment

Reduction of salt in pork sausages by the addition of carrot fibre or potato starch and high pressure treatment Meat Science 92 (2012) 481–489 Contents lists available at SciVerse ScienceDirect Meat S.

Reduction of salt in pork sausages by the addition of carrot fibre or potato starch and high pressure treatment

Alberto Grossia,⁎ , Jakob Søltoft-Jensenb, Jes Christian Knudsena, Mette Christensena, Vibeke Orliena

a

Department of Food Science, Food Chemistry, Faculty of Life Sciences, University of Copenhagen, Denmark

b Danish Meat Research Institute — Danish Technological Institute, Roskilde, Denmark

a b s t r a c t

a r t i c l e i n f o

Article history:

Received 29 December 2011

Received in revised form 1 April 2012

Accepted 18 May 2012

Keywords:

Low salt sausages

Hydrostatic pressure processing

Uniaxial compression

Napping

Protein solubility

Dietary ingredients

The combined effect of high pressure processing (HPP) (400, 600 and 800 MPa) and carrotfibre (CF) and po-tato starch (PS) on low salt (1.2%) pork sausages was investigated and compared with high (1.8%) salt sau-sages Sausages had a marked increase in whitening with increasing content offibre or starch, pressure level, and process temperature The degree of redness was mainly affected by pressure level and heat treat-ment An importantfinding regarding salt reduction was that the use of starch or fibre had more impact on textural properties than the level of salt since Young's modulus and strain at fracture were mainly affected by formulation and HPP Water binding capacity of low salt sausages was improved to the same level as high salt sausages with HPP and addition of CF or PS particularly by the addition of PS which produced sausages with better sensory properties than CF The sensory analysis showed that this approach is promising for producing low salt sausages

© 2012 Elsevier Ltd All rights reserved

1 Introduction

Generally, consumers do not consider pork sausages as healthy

meat products due to a high level of fat and salt According to

Tuomilehto et al (2001), a high level of sodium chloride has shown

a negative impact on human health (Tuomilehto et al., 2001)

Reduc-tion of salt in meat products has therefore become an important

re-search area during the last decade (Desmond, 2006; Doyle & Glass,

(F.S.A., 2004) and theWorld Health Organization (2006), have

pub-lished advisory guidelines for daily salt intakes recommending about

a 50% reduction in the average salt intake per day However, in the

meat industry addition of various salts to meat products is commonly

used to improve food functionality and ensure food safety The

addi-tion of salts (commonly 1.5 to 2.5% of sodium chloride) to meat batters

improves gelation, water binding capacity, fat retention, and cooking

loss For health improvement, a variety of approaches have been

ap-plied to reduce the sodium content, among these are the substitution

of sodium chloride with other types of salt or newer processing

tech-niques (Desmond, 2006; Doyle & Glass, 2010) High pressure

process-ing (HPP) is one of the newer technologies that have shown great

potential for manufacturing meat products; indeed HPP offers a

valuable alternative to the thermal pasteurization Nowadays, indus-trial HHP equipment can reach pressures of 600 MPa, which is a highly effective treatment for decreasing of bacterial load and extending the safe shelf life of refrigerated processed meat product (Jofre, Aymerich, Grebol, & Garriga, 2009) The promising application of HPP treatment

is based on the pressure-induced increase in solubility of the myo fi-brillar proteins resulting in gelation and formation of the desired texture (Colmenero, 2002) HPP (100–300 MPa) was shown to induce

a significant increase in the penetration force of raw meat batter (Carballo, Fernandez, & Colmenero, 1996) However, the pressure-induced gelation ability of meat proteins, especially in sausages, de-pends on the type of meat (protein system), the type of additives, and quite importantly temperature, since muscle proteins are also characterized by being thermolabile Some studies have been per-formed on the interaction between HPP and salt level on the

function-al properties of various types of meat product including pork and chicken In these studies it was reported that HPP technology is a via-ble process that partially compensates for the reduction of salt levels

in meat product (Crehan, Troy, & Buckley, 2000; Jimenez-Colmenero, Fernandez, Carballo, & Fernandez-Martin, 1998; Sikes, Tobin, & Tume, 2009) Other studies have shown that the combination of HPP and different ingredients in the meat batters may improve or impair the functional properties of processed meat products ( Fernandez-Gines, Fernandez-Lopez, Sayas-Barbera, & Perez-Alvarez, 2005; Grossi, Soltoft-Jensen, Knudsen, Christensen, & Orlien, 2011; Hong, Min, Ko, & Choi, 2008; Trespalacios & Pla, 2007) The present authors have shown that HPP and incorporation of carrot dietaryfibre (CF) in a commi-nuted meat emulsion, result in a high order of network organization

⁎ Corresponding author at: Department of Food Science, Food Chemistry, Faculty of

Life Sciences, University of Copenhagen, Rolighedsvej 30 DK-1958 Frederiksberg C,

Denmark Tel.: + 45 3533 3547; fax: + 45 3528 3344.

E-mail address: atg@life.ku.dk (A Grossi).

0309-1740/$ – see front matter © 2012 Elsevier Ltd All rights reserved.

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Meat Science

j o u r n a l h o m e p a g e : w w w e l s e v i e r c o m / l o c a t e / m e a t s c i

leading to a harder texture and high water binding capacity (Grossi

et al., 2011)

The present study aims to investigate the combination of HPP and

addition of CF and/or potato starch (PS) for production of sausages

with reduced salt content by determining the effect of working

pres-sure, temperature, and formulation on the physical properties of pork

sausages

2 Materials and methods

2.1 Product manufacture

Sixteen batches of sausages were manufactured at the Danish Meat

Research Institute, Roskilde Denmark (DMRI) The raw material of all

the batches included (w/w) 56.2% of pork“topside” (semimebranosus;

2.2% fat, 75.3% water, 22.1% protein), 20% of loin fat (78.0% fat, 17.1%

water, 4.9% protein), 22% of water, 1% of sodium chloride (99.4%

NaCl and 0.6% NaNO3; 60 ppm NaNO3infinished product) and either

0.2% or 0.8% sodium chloride without sodium nitrite The sixteen

for-mulations differed in the content of salt, carrotfibre (CF; Hydrobind

LP, Bolthouse Farms Inc., USA, extracted, driedfibre portion of carrots)

and/or potato starch (PS; Superior potato starch, KMC, Denmark,

unmodified starch from potatoes) Ingredient levels were based on

screening results, recommendations from suppliers and specifically

for salt levels based on common low end commercial level and future

lowest possible end Acronyms were used to describe the different

recipes and the different letters of the acronym indicate the

concen-tration of the ingredients (seeTable 1a and b): 1.8% NaCl with 0.6%

NaNO2(S: high salt content), 1.2% NaCl with 0.6% NaNO2(s: low salt

content), 3.8% PS (P: high content), 2% PS (p: low content), 1.5% CF

(C: high content), and 0.5% CF (c: low content) All the ingredients

(temperature of raw material 2–4 °C) were mixed in a vacuum high

speed cutter (V30L, Kilia, Germany) at 2880 revs/min (3 min of cutting

time, followed by 20 rounds of backward knife rotation under full

vac-uum) until an end-point temperature of 12 °C of the emulsion was

reached The meat emulsions were stuffed on a vacuumfilling machine

(VF50, Handtmann, Germany) in poly amide casings (naloflex, Kalle,

Germany) of 60 mm in diameter and 140 mm in length (360 g each)

After manufacturing the raw sausages were kept at 4–5 °C for 18–24 h

until HPP

2.2 HPP and storage

The sausages were vacuum packed and submerged in the

pressuriz-ing chamber of a QUINTUS Food Processpressuriz-ing Cold Isostatic Press QFP-6

(Avure Technologies AB, Västerås, Sweden) with a pressure chamber

of 0.9 l and a maximum operating pressure of 1000 MPa, 6.7 MPa/s =

402 MPa/min The sausages were brought to an internal temperature

of 5 or 40 °C followed by HPP treatment at 400, 600, or 800 MPa for

5 min at the respective temperature After HPPt, all the sausages (4 for each formulation treatment) were stored at 5 °C in the dark for 5 days before analysis of colour and texture

Control sausages from all batches were: not HPP treated and heat treated at either 5 or 40 °C in a water bath until a core temperature equal to the water temperature was reached In addition, heat treated sausages to a core temperature of 72 °C were used to simulate normal cooking conditions for sausage production

2.3 Colour The internal surface colour of the sliced sausages was measured using a Konica Minolta Spectrophotometer CM-600d (illuminant D65 and a 10° standard observer) with an aperture size of 40 mm and the corresponding Colour Data Software CM-S100w SpectraMagict™

NX (Konica Minolta Sensing, Inc., Japan) The instrument was cali-brated with a white standard plate The values, expressed as CIE Lab L* (lightness), a* (redness), b* (yellowness), and reflectance spectra within the visual spectrum (400–700 nm in 10 nm intervals) were recorded Three sausages per formulation were sliced and colour mea-surements were performed on 5 different positions within the cross section of each sausage A total of 20 measurements per treatment were obtained

2.4 Uniaxial compression Rheological properties of sausages were assessed by uniaxial com-pression (Instron 5564 Universal Testing Machine, Instron Ltd., High Wycombe, UK) For each formulation treatment, measurements were made on eight slices cut from three sausages Samples were cylindrical

in shape (60 mm in diameter and 20 mm in height) The sample was compressed at a constant crosshead velocity of 50 mm/min Sample temperature was 5 °C The compression steel plates were lubricated with a small amount of oil During compression, the displacement (mm) and corresponding force (F) were recorded The displacement and force data were converted to Hencky strain (ε) and corresponding stress (σ) The stress (σ), during compression, was calculated as the force (F) divided by the cross sectional area (A) of the sample, and mul-tiplied by the height of the sample during compression (Ht) relative to the initial height (H0) of the sample:σ=(F/A)*(Ht/ H0), as described previously (Grossi et al., 2011) The Hencky strain (ε) was calculated

as follows:ε=ln (Ht/ H0), and the magnitude, i.e positive value, is provided as the result (Grossi et al., 2011) Young's modulus (E) was calculated from compression curves as the initial slope of stress versus strain Hencky strain at fracture (εf) was determined from thefirst local maximum at the compression curve

2.5 Water binding capacity Water binding capacity (WBC) was determined by centrifugation, and values were obtained as follows: 5 g of sausage was placed in a

50 ml centrifuge tube with 10 ml of distilled water After homogeni-zation (2 bursts of 10 s) using an Ultra turrax T25 (Janke & Munkel, IKA-Labortechnik), the suspension was centrifuged at 5000 ×g for

10 min at 15 °C The supernatant was decanted and the remaining pellet was weighed For all formulation treatments, WBC was deter-mined at least in quadruplets and expressed as percentage of initial weight:

WBC %ð Þ ¼ 1−weightstart−weightend

weightstart

 100:

Table 1

Representation of the sixteen different recipes a) Formulation with high content of salt

(1.8%) and b) formulation with low content of salt (1.2%) Bold (fibre and starch)

indi-cates the presence of carrot fibre and/or potato starch, and italic indicates the related

quantity (fibre: no, 0%; low c, 0.5%; high C, 1.5%; starch: no 0, 0%; low p, 2%; high P,

3.8%).

a)

Low salt content Carrot fibre

No 0 Low c High C

b)

High salt content Carrot fibre

No 0 Low c High c

2.6 Protein solubilisation

Each of the raw batches (treated at 0.1, 400, 600 and 800 MPa)

was homogenized in 0.6 M NaCl (1:4, v/v) at 4 °C The homogenate

was centrifuged at 20,000 ×g for 30 min and the resulting supernatant

was put aside whilst the pellet was re-extracted with 5 ml of 0.6 M

NaCl in phosphate buffer (3.38 mM Na2HPO4, 15 mM NaH2PO4; pH

7.5) homogenization solution, stirred for 1 h at 4 °C and centrifuged

The two supernatants were then pooled and used for analysis

The protein concentration of the solubilised fraction was

deter-mined by sodium dodecylsulphate polyacrylamide gel electrophoresis

(SDS-PAGE) following the method ofLaemmli (1970) The samples

were dissolved in SDS sample buffer to a protein concentration of

1 mg/ml (106 mM Tris HCl; 141 mM Tris Base; 2% LDS; 10% Glycerol;

0.51 mM EDTA; 0.22 mM SERVA Blue G250; 0.175 mM Phenol Red;

pH 8.5) boiled for 5 min and loaded onto Tris-acetate gels (Invitrogen,

3–8% polyacrylamide) and stained with 0.1% Coomassie brilliant blue

R-250 Following destaining, muscle proteins were identified by

com-paring relative mobilities to molecular weight standards (Bio-Rad)

run under the same conditions

2.7 Napping and ultraflash profiling

Sensory assessment by napping and ultra flash profiling (UFP)

was performed only on sausages HPP treated at 600 and 800 MPa

(400 MPa treated sausages were not sliceable) Sliceability was

evaluat-ed by peeling the casings off the cold sausages and slicing a 1 cm sample

using a sharp knife Ten sausages were selected for thefirst set of

senso-ry assessment (Napping 1): S0P, s00, sC0, s0p, and s0P treated at

800 MPa at 5 and 40 °C For the second set (Napping 2) the following

sausages were assessed: sCp, scP, and sCP treated at 600 and 800 MPa

at 5 and 40 °C

Napping, a newer, quick method for sensory assessment (not

demanding trained judges), was done in accordance with the

princi-ples described byPerrin et al (2008) The samples (slice of sausage)

were equilibrated at room temperature for 1 h prior to assessment

The samples were simultaneously presented to a panel of 10 sensory

assessors, who were requested to distribute the samples on a white

A3-paper (40 × 30 cm) according to texture and consistency (assessed

by visual inspection, appearance and touch, and texture) Samples

po-sitioned close to each other appeared identical and samples appearing

different were positioned distant from each other For each sample or

group of samples both X co-ordinate and Y co-ordinate were

consid-ered Immediately after napping the 10 judges performed UFP They

were asked to enrich their A3-paper by writing descriptive words

di-rectly on the paper to characterize the samples, which were different

or belonged to the same group regarding texture and consistency

The profiling words were collected and the 9 most frequent words

were chosen

2.8 Statistical analysis

Data from the napping and UFP analyses were analysed using

Procrustrean Multiple Factor Analysis in the software package R

ver-sion 2.9.2 (2009-08-24) and the package SensomineR verver-sion 1.10

(2009-10-02) with a modified function by Guillaume Le Ray, Delta,

Denmark

Statistical evaluation of all the data (except napping) was performed

using the procedure mixed in SAS (Ver 9.2, SAS Institute Inc., Cary, NC,

USA) The mixed procedure was applied to calculate least square means

(LSM) and standard error of the means (SE) The statistical model

in-cluded thefixed effect of HP treatment, fibre content, starch content,

salt content and temperature Interactions betweenfixed effects were

only included in the model when significant Differences between

fixed effect levels were considered significantly different if pb0.05

3 Results and discussion 3.1 Meat emulsion characteristics: texture, water binding capacity (WBC), myofibrillar protein solubility and colour

Addition of salt (sodium chloride) to processed meat products, during manufacturing is often used to obtain the desired texture as well as the desired water content in thefinal product One of the most important technological features in the production of processed meat products is to obtain high structural stability and hence high WBC and increased cooking yield It was reported that increasing WBC resulted in increased cooking yield originating from the in-crease in retained water (Funami, Yada, & Nakao, 1998) The addition

of dietaryfibre and HPP processing has a positive effect on WBC of processed meat products (Moller et al., 2011) containing 1.8% salt Hence to enable a reduction of salt content in sausages, the effect of addition of ingredients with functional properties and HPP treatment

on WBC was determined Sausages with low salt content (s00; 1.2%) had a significantly lower (pb0.05) WBC than sausages with high salt content (1.8%; S00, S0p, S0P) when HPP treated at 5 °C (Fig 1a)

or at 40 °C (Fig 1b) This is in accordance with previousfindings (Ruusunen & Puolanne, 2005) where it was suggested that sodium chloride increases the cohesiveness of the batter thereby improving the water retention

Salt concentration is also known to affect the solubility of myo fi-brillar meat proteins like myosin and actin, thereby affecting their ability to form a protein matrix Pressure is known to induce disrup-tion of hydrophobic and electrostatic interacdisrup-tions whilst enhancing

Fig 1 Water binding capacity (WBC) of sausages heat treated at 5 °C (a) and 40 °C (b) Black bars represent sausages HPP at 400 MPa, grey bars at 600 MPa and white bars (800 MPa) For definition of the formulation treatment acronyms, please consult

Table 1 a and b Error bars represent standard error of the means (SEM).

hydrogen bonding (Mozhaev, Heremans, Frank, Masson, & Balny,

1996) Hence, HPP has been applied to increase the solubility of

mus-cle proteins and hence improve the functional properties of certain

myofibrillar proteins (Sikes et al., 2009) On the other hand, it has

also been reported that HPP can induce protein denaturation and

thereby result in loss of solubility of the main myofibrillar proteins

(Lee, Kim, Lee, Hong, & Yamamoto, 2007) It is, thus, important to

in-vestigate the effect of HPP treatment and the two salt levels on the

protein solubility in the sausages As seen inFig 2, the different salt

concentrations (1.8% or 1.2%) affected the solubility of the myo

fibril-lar proteins in the same manner, and simifibril-lar marked decreases in the

main myofibrillar proteins bands were found Apparently, the HPP

ef-fect on protein solubility is superior to the salt efef-fect for the salt levels

used in the present study It can be speculated that the reduction of

myofibrillar protein bands is a result of denatured proteins forming

large molecular weight aggregates (thus not found in the molecular

weight separation range of SDS-page gels) or is a result of denatured

proteins forming insoluble aggregates (thus lost during the

centrifu-gation step in sample preparation) From these results we can

specu-late that the differences in WBC are due to salt concentration but also

are promoted by the effect of HPP on myofibrillar protein solubility

Addition of CF and/or PS to the low salt sausages increased the WBC

(Fig 1) However, WBC of sausages with low salt and high PS (Fig 1) did

not change significantly between 600 and 800 MPa treatments,

where-as sausages with low salt content and high CF showed a significant

increase in WBC between 600 and 800 MPa (pb0.05) This observation

can be explained by the fact that insolublefibre favours water binding

properties because water binds to insoluble polysaccharides by

hydro-gen, ionic and/or hydrophobic interactions (Pietrasik & Janz, 2010)

Previously,Moller et al (2011)showed that this phenomenon acts

synergistically with the effect of HPP Starch gelatinizes under pressure

in two steps,first a hydration of the amorphous parts of the starch gran-ules occurs followed by the swelling and distortion of the crystalline re-gion (Rubens, Snauwaert, Heremans, & Stute, 1999; Simonin, Guyon, Orlowska, de Lamballerie, & Le-Bail, 2011) The WBC results show that the combination of HPP and addition of functional ingredients improves the WBC of low salt sausages to the same level as high salt sausages and hence this technique has technological potential as a tool to produce low salt meat product

The instrumental measures of texture are Young's modulus and the strain at fracture.Fig 3shows the modulus of the sausages

treat-ed at 400, 600, or 800 MPa at 5 or 40 °C Young's modulus increastreat-ed with increasing pressure level for all sausages Sausages treated at

800 MPa had about 50% higher modulus value compared to the mod-ulus measured after treatment at 400 MPa (pb0.05) Texture of sau-sages containing PS or CF (irrespective of concentration level) was significantly affected (pb0.05) by pressurization than sausages with-out PS or CF (S00 and s00) which had the lowest modulus Indeed, the three treatments S00, S0p, and S0P had a high content of salt (1.8%) and differed in the PS content (0, 2, and 3.8%, respectively) and the ef-fect of starch on the Young's modulus value is clear; starch and pres-sure increased the hardness At the reduced salt content of 1.2% the same texture enhancing effect of starch and pressure is observed (comparing s00 with s0p and s0P inFig 3) Notably, when the PS level is 3.8% the effect of pressure is similar irrespective of salt level, seen as the same Young's modulus values (comparing S0P, s0P, and sCP inFig 3a and b) at all treatments (400, 600, and 800 MPa at 5

or 40 °C) The same impact on texture is also observed for sausages with added CF alone (comparing S00 with SC0 and Sc0 and s00 with sC0 and sc0,Fig 3), though sausages with low salt concentration

Fig 2 SDS-page electrophoresis of myofibrillar protein extract from sausages high

pressure treated at 0.1, 400, 600 and 800 MPa A clear decrease in solubility of the

main myofibrillar components is observed after HPP No difference in protein solubility

is observed in formulation treatment with high (S) and (s) low salt concentrations.

S = 1.8% NaCl; s = 1.2% NaCl 0 = indicates neither fibre nor starch and only serves to

fill up the code.

Fig 3 Young's modulus of the sausages (from Table 1 ) HPP at 5 °C (a) or at 40 °C (b) Black bars represent sausages treated at 400 MPa, grey bars at 600 MPa, and white bars at 800 MPa For definition of the formulation treatment acronyms, please

and addition of CF (sC0 and sc0) had lower Young's modulus values than sausages with PS (s0P and s0p) Surprisingly, upon addition of both starch andfibre (independent on concentration levels) no fur-ther texture improvement was found, thus fur-there was no synergistic effect of the starch andfibre

In general, the magnitude of Young's modulus increased more than two-fold when sausages were treated at 40 °C instead of 5 °C (Fig 3a and b, respectively) This result was expected since myofibrillar pro-tein denaturation is more extensive at moderate high temperature and high pressure compared to the denaturation induced by high pressure treatment alone The high moduli at 40 °C may be explained

by a high level of protein denaturation, which promotes protein aggre-gation and formation of a protein matrix with high gel strength The strain at fracture represents the relative deformation when a material begins to fracture A small strain at fracture indicates that the material is brittle and a high strain at fracture is usually recorded

in an elastic material.Fig 4a and b shows that the strain at fracture of the sausages increased with increasing pressure at both treatment

Fig 4 Hencky strain of sausages heat treated at 5 °C ( Fig 3 a) and 40 °C ( Fig 3 b) Black

bars represents sausages HPP at 400 MPa, grey bars at 600 MPa and white bars 800 MPa.

For definition of the formulation treatment acronyms, please consult Table 1 a and b.

Error bars represent standard error of the means (SEM).

Table 2

a) L* colour values (average with standard deviation) of sausages either heat treated to a core temperature of 5 or 40 °C and following pressurization at 400, 600 or 800 MPa for

5 min For each formulation treatment and high pressure treatment and temperature, different letters represent significant differences (pb0.05) b) a* colour values (average with standard deviation) of sausages either heat treated to a core temperature of 5 or 40 °C and following pressurization at 400, 600 or 800 MPa for 5 min For each formulation treatment and high pressure treatment and temperature, different letters represent significant differences (pb0.05) P = potato starch (3.8%); p = potato starch (2%); C = carrot fibre (1.5%); c = carrot fibre (0.5%).

a)

L* values Sausage formulation

Temperature HP

5 (°C) 400 MPa 63.29 ± 0.11 a 64.55 ± 0.21 b 62.72 ± 0.18 d 63.87 ± 0.11 bc 64.82 ± 0.32 b 64.96 ± 0.25 b 64.83 ± 0.27 b

600 MPa 64.14 ± 0.22 bc 65.03 ± 0.27 b 63.42 ± 0.22 c 64.31 ± 0.24 b 65.10 ± 0.26 bd 64.98 ± 0.22 b 65.22 ± 0.2 bd

800 MPa 65.02 ± 0.31 bd 67.69 ± 0.31 e 64.51 ± 0.32 b 67.25 ± 0.18 e 67.63 ± 0.3 e 67.80 ± 0.16 e 67.76 ± 0.24 e

40 (°C) 400 MPa 65.19 ± 0.15 a 65.98 ± 0.23 ab 64.52 ± 0.11 c 64.47 ± 0.22 c 65.62 ± 0.34 a 65.96 ± 0.14 ab 65.83 ± 0.21 ab

600 MPa 66.14 ± 0.23 ab 67.83 ± 0.31 e 65.82 ± 0.28 ab 66.31 ± 0.28 ab 67.78 ± 0.25 e 67 87 ± 0.22 e 68.17 ± 0.19 e

800 MPa 67.64 ± 0.32 e 69.23 ± 0.21 f 66.85 ± 0.19 ab 67.26 ± 0.14 e 68.97 ± 0.18 ef 69.08 ± 0.29 f 69.17 ± 0.27 f b)

a* values Sausage formulation

Temperature HP

5 (°C) 400 MPa 7.56 ± 0.16 a 6.68 ± 0.11 b 7.84 ± 0.18 a 6.86 ± 0.08 b 6.70 ± 0.15 b 6.77 ± 0.14 b 6.69 ± 0.19 b

600 MPa 6.91 ± 0.13 b 6.38 ± 0.19 c 6.93 ± 0.11 b 6.46 ± 0.21 c 6.27 ± 0.13 c 6.48 ± 0.11 c 6.22 ± 0.14 c

800 MPa 6.19 ± 0.09 c 5.99 ± 0.13 cd 6.35 ± 0.11 c 5.87 ± 0.16 cd 5.75 ± 0.14 d 5.55 ± 0.19 d 5.67 ± 0.21 d

40 (°C) 400 MPa 6.86 ± 0.11 a 6.13 ± 0.18 b 6.94 ± 0.13 a 6.15 ± 0.16 b 6.25 ± 0.12 b 6.17 ± 0.05 b 6.15 ± 0.21 b

600 MPa 6.31 ± 0.18 b 5.58 ± 0.17 c 6.53 ± 0.12 b 5.65 ± 0.15 c 5.77 ± 0.13 c 5.75 ± 0.15 bc 5.61 ± 0.19 c

800 MPa 5.85 ± 0.12 c 5.13 ± 0.09 d 6.31 ± 0.17 b 4.94 ± 0.18 d 5.05 ± 0.11 d 5.15 ± 0.12 d 5.12 ± 0.11 d

Fig 5 Reflectance spectra of the sausages (from Table 1 ) treated at 800 MPa at 40 °C For definition of the formulation treatment acronyms, please consult Table 1 a and b.

temperatures, though for some sausages treated at 40 °C the strain at

fracture is lowest at the highest pressure level Especially, sausages

with a high content of PS have very low strain at fracture values

com-pared to other sausages, in agreement with the higher modulus

values (Fig 3) The strain at fracture is consistent with the Young's

modulus (Fig 3), that is a high modulus value represents a hard

tex-ture result and a low fractex-ture value indicates a more brittle textex-ture

Atfirst sight, colour is one of the main meat product attributes

that influence consumer's acceptance Overall, the colour attributes of

processed meat products are among others influenced by the meat

pigments and meat structural proteins and their degree of denaturation due to processing techniques In comminuted meat products, the colour

is also affected by the fat content, size of fat globules, water content, and the homogeneity of the cutting surface of the product (Grossi et al., 2011; Pietrasik & Janz, 2010) Previously we showed that the addition

of CF to high fat sausages did not affect the colour of the meat product (Grossi et al., 2011) A general tendency, as seen inTable 2, is that the L* value increases with increasing content offibre or starch, pressure level, and process temperature This can be explained by water content and matrix changes Addition of CF or PS to the meat emulsion increases

Fig 6 (a) Plot from Procrustrean Multiple Factor Analysis of Napping positioning from Napping 1 First dimension explains 46.57% of the variation, second dimension explains 17.27% of the variation Circles indicate significance levels (pb0.05) (b) Plot from Procrustrean Multiple Factor Analysis of the 11 most used ultra-flash profiling terms First dimen-sion explains 46.57% of the variation, second dimendimen-sion explains 17.27% of the variation The first number of the codes refers to formulation treatments: 3, high salt with high potato starch content, S0P; 4, low salt with no ingredients, s00; 5, low salt, with high carrot fibre, sC0; 7, low salt and low potato starch, s0p; 8, low salt and high potato starch, s0P The

the WBC (Fig.1) and the increased WBC in combination with the added

non-meat ingredients (fibre and starch) may have a diluting effect on

the meat pigment and structural proteins, thus resulting in more

reflected light and a whiter appearance On the contrary, the sausages

with low or high salt content and withoutfibre and starch (S00 and

s00 inTable 2andFig 1) had the lowest water binding capacity and

the lowest lightness values

Lightness values increased upon increased pressure level and

pres-sure temperature suggesting an important influence of the matrix

changes on lightness of the product Upon pressurization, severe

changes in protein conformation take place, and in meat systems

es-pecially the changes in pigment and structural proteins will affect

the whiteness The impact of conformational or chemical changes of

myoglobin on the colour changes is still not clarified Thus, the whit-ening effect is suggested to result from denaturation of myosin and possible aggregation thereby changing the ability of the meat to ab-sorb and/or reflect light (Supavititpatana & Apichartsrangkoon, 2007) The degree of redness was mainly affected by pressure level and temperature and to a lesser degree by the type and amount offibre and starch Sausages HPP treated at 800 MPa had a lower a* value than sausages treated at 400 or 600 MPa, and pressurization at 40 °C further decreased the redness Sausages without fibre and starch (S00 and s00) had a significantly higher a* value compared to the other sausages at same pressure and temperature These results sug-gest that the red colour is more affected by light scattering properties than any pressure-induced changes of myoglobin because redness

Fig 7 (a) Plot from Procrustrean Multiple Factor Analysis of Napping® positioning from Napping 2 First dimension explains 58.95% of the variation, second dimension explains 13.39% of the variation Circles indicate significance levels (pb0.05) (b) Plot from Procrustrean Multiple Factor Analysis of the 13 most used ultra-flash profiling terms First dimen-sion explains 58.95% of the variation, second dimendimen-sion explains 13.39% of the variation The first number of the codes refers to formulation treatments: 9, low salt with high carrot fibre and low potato starch content, sCp; 10, low salt with low carrot fibre and high potato starch content, scP; 11, low salt, with high carrot fibre and high potato starch

seems to depend on whether the sausages contain hydrocolloids or

salt

A significant decrease in yellowness (b*) was only found upon

pres-surization at 600 or 800 MPa at 5 or 40 °C, and is suggested to be

in-volved in the grey–brown colour simultaneously with the lower a*

value (Carlez, Veciananogues, & Cheftel, 1995)

at 800 MPa Usually, the reflectance curve of meat based samples is

characterized by the maxima around 540 and 580 nm of

oxymyo-globin However, in meat systems containing nitrite salt it is more

like-ly that nitrosomyoglobin is responsible for the red colour The

apparent reflectance maximum at 510 nm and minimum at 570 nm

seen in the reflectance curve of the sausages (Fig 5) indicate that

the red colour corresponds to nitrosylmyochromogen Moreover,

as no spectral changes in the reflectance curves (around 500 nm)

between non-pressurized and pressurized sausages are observed, it

is suggested that it is not related to the severe changes in pigment

component (results not shown) As seen in Fig 5, sausages with

salt as ingredient (S00 and s00) result in the lowest level of the

reflectance curves compared with sausages containing CF and/or PS

Interestingly, reducing salt content did not affect the reflectance

curve in pressurized sausages in the presence of hydrocolloids like

PS and CF

Hence, the detected colour changes are probably related to changes

in texture, such as denaturation, aggregation of myofibrillar proteins

and WBC

3.2 Sensory assessment: napping and ultraflash profiling

Fig 6shows the Napping 1 results of sausages s00, sC0, s0P, s0p,

and S0P (Table 1) HPP treated at 800 MPa at 5 or 40 °C Clearly,

when the sausages contain PS, the positioning is affected by the

tem-perature at which HPP is performed Thus, sausages containing PS in

high (Fig 6, codes 3 and 8) and low (Fig 6, code 7) levels are

posi-tioned significantly further to the left at 40 °C compared to 5 °C and

to other sausages The UFP analysis showed that those sausages

were characterized by beingfirm and gummy-like, whereas sausages

containing PS and HPP treated at 5 °C were characterized by being

ho-mogeneous However, all other sausages were characterized by being

fatty,floury, creamy, soury, and sticky Notably, reducing the salt

con-tent in the sausages with high amounts of PS (Fig 6, codes 3 and 8)

did not affect the positioning and the sensory attributes upon HPP

treatment at 40 °C, indicating that the salt content was not important

for the sensory perception of these sausages Contrary to the

fibre-rich sausages the treatment temperature did not significantly affect

the positioning of sausages containing CF (Fig 6, codes 4 and 5)

Hence, it seems from this study that addition of PS results in sausages

with a more appealing texture than addition of CF

In Napping 2 the sausages containing low salt, a combination of

starch andfibre and HPP treated at 600 or 800 MPa at 5 or 40 °C were

evaluated It was found that the positioning of the sausages differed

significantly according to treatment temperature Thus, HPP at 40 °C

resulted in a different texture than at 5 °C This is in agreement with

results from Napping 1, since all the samples in Napping 2 contain PS

Furthermore, a tendency towards different positioning of sausages

HPP treated at 600 MPa compared to 800 MPa was observed (Fig 7)

Sausages HPP treated at 40 °C are characterized by being gummy-like,

firm, dry, compact and gritty Samples treated at 5 °C are creamy, sticky,

slimy, soft,floury, and fatty However, an overall conclusion on the

attri-butes that characterize pressure level in these sausages was not

possi-ble This might be due to the fact that the combined effect of mild

temperature treatment (40 °C) and HPP (at 600 MPa or 800 MPa)

may lead to a higher formation of chemical cross-links and protein

de-naturation, compared to low temperature treated sausages (5 °C) at

both 600 and 800 MPa

4 Conclusion The salt content of pork sausages could be reduced from 1.8 to 1.2% salt by addition of hydrocolloids (either carrotfibres or potato starch) and subsequent HPP at 600 MPa without negative effects on water binding capacity, colour and texture Mild heating (40 °C) acts synergistically with HPP improving even further meat emulsion char-acteristics Finally, sausages containing potato starch had better sen-sory quality than thefibre-rich sausages

Acknowledgement The authors wish to thank the Danish Ministry of Food, Agriculture and Fisheries forfinancial support through the projects entitled “New Gourmet pork products obtained through molecular understanding of alternative pig breeds and high pressure technology” (project no 3304-FVFP-08-K-21-04) Thanks are expressed to personnel from the Danish Meat Research Institute Ms Ann-Britt Frøstrup and Mr Jens P Teilmann for their invaluable technical assistance and Ms Camilla Bejerholm for discussion of napping and UFP data

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