The influence of varying degrees of adhesion as determined by mechanical tests on the sensory and consumer acceptance of a meat product

Meat Science 28 (1990) 141-158

The Influence of Varying Degrees of Adhesion as Determined by Mechanical Tests on the Sensory and Consumer Acceptance of a Meat Product Andrew W. J. Savage, Susan M. Donnelly, Paul D. Jolley, Peter P. Purslow & Geoffrey R. Nute AFRC Institute of Food Research, Bristol Laboratory, Langford, Bristol BSI8 7DY, UK

(Received 18 July 1989; accepted 30 October 1989) A BSTRA CT The adhesion between meat pieces in meat products, varied by the addition of different concentrations of a crude myosin solution, was measured by a trained sensory panel and by two instrumental tests: tensile adhesive strength (TAS) and punch and die. A consumer trial was used to find which let'el of adhesion was preferred. Results from the sensory panel showed that the adhesion could be detected as highly significant ( P < 0.001) differences in three tactile measurements and in the two eating qualities, ease of fragmentation and rubberiness. TAS measurements gave larger differences between treatments than punch and die, and had very high correlations with ease of fragmentation and crumbliness on cutting. The small consumer study revealed no overall preference for any one product. Hence, although differences in adhesion between meat pieces in a meat product are detectable subjectively and can be measured objectively by TAS tests, preference for any particular strength varies between individuals.

INTRODUCTION

Reformed or restructured meats are meat products made of pieces of meat bound together to resemble the texture and appearance of whole muscle. These products may be categorised according to the size of the constituent meat pieces (Sheard & Jolley, 1988); at one extreme, sectioned and formed products (e.g. reformed ham, beef roasts) are made up from relatively large muscle chunks, while at the other extreme chopped and shaped products are 141 Meat Science0309-1740/90/$03"50 © 1990 Elsevier Science Publishers Ltd, England. Printed in Great Britain

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made from relatively small meat pieces. Adhesion, or binding, between meat pieces in the vast majority of such products is brought about by thermal gelation of protein present on their surfaces. Adhesion is important for two reasons. Firstly, the pieces have to be bound together so that the product can be manipulated without falling apart; for example, hams usually need to be sliced or carved and restructured steaks need to remain intact after cooking and during serving. Secondly, bind may affect the texture of the product as a whole, so that during eating the influence of bind on texture may be important. In the case of sectioned and formed meats bind may have less effect on texture because of the comparatively small number of adhesive junctions and the texture of the whole muscle pieces will predominate. However, in the case of chopped and shaped products with small pieces, eating will break many junctions and the adhesion between these could be very important in determining overall texture. Much work has been done on the factors that affect restructuring processes (e.g. Booren et al., 1981a, b). Although sensory and instrumental tests have been used to assess the effect of factors on eating quality, no work has looked directly at the effect of solely altering the adhesion between meat pieces on the acceptability of the products. The closest approach to this has been the work of Ford et aL (1978) who examined the binding of restructured steakettes made with added myosin and/or sarcoplasmic protein with different salt levels and performed objective and subjective assessments. They found a highly significant (P < 0.001) correlation between a sensory panel assessment of adhesion and single junction breaking strength and a less significant (P<0.01) correlation with cooked steakette breaking strength. They found no significant correlation between adhesion and overall acceptability. However, their main aim was to examine the potential of obtaining good adhesion with a low salt level, and their results for correlations of adhesion with objective measurements and overall acceptability are based on results from only three treatments with any one salt level, and in the case of single junction breaking strength only the products from two of the three treatments could be measured. It is also likely that the different salt levels used alter the nature of the meat pieces, so affecting quality attributes other than just the adhesion between meat particles. The question of whether a stronger bind results in a more acceptable product is open and requires testing. It is sometimes assumed that greater cohesion means a more acceptable product; for example, Chesney et al. (1978) and Popenhagen and Mandigo (1978) used taste panels to assess product cohesion on an hedonic scale, but discuss results in terms of greater or less--rather than better or worse----cohesion. The tacit assumption of a

Influence o f adhesion on acceptance of a meat product

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positive relationship between the product cohesion and acceptability may not be valid. The aims of this work were to investigate the sensory detection of adhesion in meat products that differ solely in their level of adhesion and to relate this to two objective instrumental tests: tensile adhesive strength (TAS) and punch and die (frequently used to measure compressive properties of meat products (e.g. Jones et al., 1985)). Previous Work in this laboratory (Donnelly & Purslow, 1987; Purslow et al., 1987) has used TAS measurement as a well founded basic test to assess adhesion in model systems. The acceptability of different levels of adhesion is determined, in order to establish whether a stronger bind gives a more acceptable product.

MATERIALS A N D METHODS

Preparation of crude myosin solution Crude myosin was prepared using a method similar to Perry (1955). Forequarter muscle (22-24 kg) from an 18-month-old heifer obtained within 1.5 h of slaughter was trimmed of surface fat and connective tissue and minced through a 4 mm plate of a pre-cooled mincer. Sixty litres of chilled 0"3M NaC1, 0"IM NaH2PO4, 0"05M Na2HPO4 solution (all food grade, NaC1 from New Cheshire Salt Works Ltd, Northwich, Cheshire: all phosphates kindly donated by Albright and Wilson) was added to approximately 18 kg of the minced muscle in a meat tumbler (Model CN 140, Lescha, West Germany) and the mixture agitated gently for 1 h at I°C. The mixture was centrifuged (2000 x g,,ax for 10 min at 4-7:C) and the supernatant filtered through a nylon sieve until 501itres was obtained. Fourteen volumes of chilled deionised water were added and the precipitated crude myosin was left to settle overnight. The clear supernatant was discarded and the remaining suspension centrifuged at 2000 x gmaxfor 15 min. The pellet was concentrated by re-centrifuging at 11 500 x ga, for 10min and analysed for protein using the Kjeldahl method (assuming protein = 6-25 x nitrogen). Five solutions, each of 800 g, were prepared by suitable dilution of the crude myosin (to 0%, 1.75%, 3.5%, 5-25% or 7% protein) in a solution of 3% NaC1 and 1% sodium tripolyphosphate. Solutions were used within 1 day of preparation.

Preparation of meat products Chilled de-membraned muscles (67.5 kg) from steer chuck and blade were obtained from a local boning plant and blast frozen at -30°C. The frozen

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blocks were bandsawn into sticks approximately 3.5cm x 3.5cm crosssection, and the sticks randomly assigned to three replicate processing batches. The meat was held at - 2 0 ° C until required. The meat from each processing replicate was randomly divided into five treatment groups and thawed prior to use by holding for 1 week at + I°C. Each treatment was prepared by mincing the thawed meat (at -0-1 to + 1.0°C) through a 10 mm plate of a pre-cooled mincer followed by mixing 4 kg mince with 800 g of the appropriate crude myosin solution for 1.5 min in a mixer (Stalberk, Team Equipment, Oxted, Surrey), the solution being added during the first 30 s ofmixing. Each mixture was formed by pressing in a D-mould (of the sort commonly used in ham manufacture) and blastfrozen at - 30°C overnight. Patties were produced from the moulded meat by bandsawing into 1 cm slices and stored at -20°C. Each treatment will be referred to by the concentration of crude myosin in the adhesive solution used to form the patties.

Cooking Samples of all treatments were cooked from frozen under a commercial grill (Falcon, Glynwed Foundries Limited, Falkirk, Scotland) on the third shelf from the top with the grill set on the 'high' power setting. Samples were cooked in rows, randomly assigned to treatment, and turned every 3 min and cooked to an internal temperature of 70°C as measured by a thermocouple probe.

Sensory assessment Samples were rated by ten assessors (all women) who had previously been selected for their basic taste acuity, and had previous experience of texture profiling. Three training sessions were held in which all treatment types were presented. After each session, assessors discussed the attributes of the samples. At the third session, assessors agreed a fixed profile which contained eight descriptors and two hedonic scales; one an attempt to elicit information on whether they liked the way in which a sample broke down in the mouth (acceptability of fragmentation) and the other concerned with how much they liked a sample (overall acceptability of texture). These scales are shown in Table 1 and were assessed on 100 mm unstructured line scales with anchor points at the extremes of each scale. Ratings were the distance (mm) from the left anchor point. Samples were presented in randomised order as a quintet at nine sessions. The first three sessions contained samples made from the first processing

Influence of adhesion on acceptance of a meat product

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TABLE 1 Line Scales used in Sensory Profiling Descriptor

Anchor points

Tactile Firmness on cutting Crumbliness on cutting Fibrous particles on cutting

Nil Nil Nil

Extreme Extreme Extreme

Eating Rubberiness Ease of fragmentation Degree of comminution Tenderness Moistness

Non-rubbery Cohesive Coarse Extremely tough Dry

Rubbery Readily separating Fine Extremely tender Wet

Hedonic Acceptability of fragmentation Overall acceptability of texture

Very poor Very poor

Very good Very good

Lines were each 100mm long with an anchor point description at each end. batch, the second group of three sessions contained samples made from the second processing batch and the final group o f three sessions contained samples from the last processing batch. Consumer trial Members of the scientific staff o f the laboratory were asked to rate how m u c h they liked a sample overall and its texture. The scales were 100 m m unstructured line scales and the ratings measured from the left anchor point, with the left anchor point labelled 'dislike extremely', the right anchor point labelled 'like extremely' and a central label 'neither like nor dislike'. A total of 55 people took part in the test which was conducted in a taste panel room. There were five separate sessions; four o f the sessions were completed by 12 assessors at a time and the fifth session was completed by seven assessors. Only samples from the third processing batch were used. Instrumental tests Tensile m e a s u r e m e n t s

Measurements were made on samples cooked as for sensory profiling, one from each treatment at each panelling session. The samples were allowed to cool to r o o m temperature. Eight 1 cm cubes were cut from each one and struck to SEM stubs with cyanoacrylate glue

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Andrew W. .L Savage et ai.

(type 409, Loctite). Care was taken to remove surface moisture so that a strong bond was formed between meat and stub. Even with care here, some of the stronger samples failed at the glue. These were examined and, if undamaged, were retested in order to avoid inadvertently testing the weakest samples in any one treatment. Meat failure occurred, on such retests, always at a higher stress than the original glue failure. Samples were pulled apart at 10mm/min on an Instron model 6022 Universal testing machine using pneumatic clamps to grip the stubs (Donnelly & Purslow, 1987; Purslow et al., 1987). Tensile adhesive strength (TAS) was measured as the breaking load divided by the the initial cross-sectional area. Three commercial products were cooked and tested as described above (except that only three samples of each type of product were used) to see how the TAS of the experimental meat products compared with the range of binding strengths found in commercial products. These products were selected as examples of the extremes of the frozen sector of the UK retail market according to declared meat content and purchase price. Two of the products were flaked and formed, one having a minimum meat content of 60%, the other 95%. The third product was sliced and formed, and had a 94% meat content. Punch and die measurements Measurements were made on raw and cooked samples using a punch and die attached to a Stevens Compression Response Analyser (C. Stevens and Son (Weighing Machines) Ltd) and using a method similar to Jones et al. (1985) with punch diameter of 1.95 cm and a clearance of 0-02 cm. A crosshead speed of 100mm/min was used. Three samples (one raw, two cooked) of each treatment were tested at each panelling session. Raw samples were removed from the freezer on the day before the test, their thickness measured and then thawed at 2°C. The order in which the samples were tested was randomised. Two samples per treatment were cooked as described above and one kept in an oven at 55°C before testing whilst the other was allowed to cool to room temperature to examine the effect of cooling. Immediately before testing, the thickness of the cooked samples was measured and three holes punched in each sample. The brownest side of the cooked samples was always placed uppermost. Punch strength (PS) was calculated from peak force and thickness (Jones et al., 1985) using

PS =

Peak force DT (Pa)

where D was the diameter of the punch (m) and T was the thickness of the sample before testing (m).

Influence o f adhesion on acceptance o f a meat product

147

Chemical analysis Samples from each treatment from the first and second batches were taken for chemical analysis. For each treatment, four raw samples were homogenised and duplicate assays performed on the mixture, and another four samples were cooked (as described before), homogenised separately and duplicate assays performed on each sample. Fat and moisture contents were determined using a CEM meat analysis system (Bostian et al., 1985). Protein was determined by the Kjeldahl method using a Buchi nitrogen system assuming protein = N × 6.25. Collagen was estimated (in duplicate on a bulked sample of the four cooked samples) from measurements of hydroxyproline made by the British Standard method (British Standard Methods of Test for Meat and Meat Products, 1979) taking collagen hydroxyproline x 7.14. Ash was determined after combustion of the sample in a muffle furnace at 550°C. Sodium chloride was determined according to a standard method (Official Standardised and Recommended Methods of Analysis, 1973).

Statistical analysis Analysis of variance (ANOVA) was used to determine significant differences between treatments with level of added myosin and assessors as treatment factors and panel as a blocking factor for the trained sensory panel data. Consumer trial data were analysed using ANOVA with level of added myosin as a treatment factor. The instrumental data were analysed using ANOVA with level of added myosin as a treatment factor and batch and panel as blocking factors. Chemical analysis data on raw samples and collagen data on cooked samples were analysed using ANOVA frith level of added myosin as a treatment factor and batch as a blocking factor. Chemical analysis data on cooked samples were analysed similarly except position on the grill was an additional treatment factor. All correlations were calculated using 45 pairs of means (five treatments x nine panels) for each correlation. RESULTS

Sensory assessment Sensory profiling The effect of level of added myosin on sensory attributes is shown in Table 2. All tactile qualities were highly significantly (P < 0.001) affected by the level of added myosin with products generally getting firmer, less crumbly and apparently having fewer fibrous panicles with increasing amount of added myosin. The 0% treatment was much more crumbly than the others.

Andrew W. J. Savage et al.

148

TABLE 2 Effect of Added Myosin on the Sensory Attributes of Meat Products

Added myosin 0% Tactile Firmness on cutting Crumbliness on cutting Fibrous particles on cutting Eating Rubberiness Ease of fragmentation Comminution Tenderness Moistness Hedonic Acceptability of fragmentation Overall acceptability of texture

1.75% 3"5% 5.25%

.VR

Isd

7%

50-5 35.0

57.5 17.1

61"0 14.1

64.5 11-3

68.7 8'5

21"3"** 50-0***

4-2 4.1

26.2

20-4

18.1

18-2

15.6

10.4"**

3.5

49.3 61.0 48.5 60.4 50.3

48.9 55.7 50"6 61.6 57.9

53"6 50'6 50-6 60-7 58-1

59.4 43.7 47.3 56.4 58"8

60-0 43.4 49.6 56.4 56" 1

10"8"** 26.2*** 1-01" 4.17** 4.34**

4-5 4.2 4.0 3"5 4.7

59.9

63.7

62.3

56-4

58-6

6.06*

3"3

57.7

62"8

63-9

60.2

58'6

4.54***

3"5

Values are means. VR--variance ratio, degrees of freedom = 4; 392. ~ - - n o t significant at 5% level. *--significant at 5°/, level. **--significant at 1% level. ***--significant at 0-1% level. Isd--least significant difference, for significant differences between treatments at the 5'/0 level. TABLE 3 Correlations between Tactile and Eating Qualities with Hedonic Attributes

Acceptability of fragmentation Firmness on cutting Crumbliness on cutting Fibrous particles on cutting Rubberiness Ease of fragmentation Degree of comminution Tenderness Moisture *--significant at 5% level. **--significant at 1% level. ***---significant at 0-1% level.

- 0.153 0-123 0-015 - 0.460"* 0.485*** 0-434** 0.657***: -0-036

Overall acceptability of texture - 0-053 - 0.214 -0-280 - 0.323* 0-094 0-321" 0-637*** 0-313"

149

Influence of adhesion on acceptance of a meat product

Of the eating qualities, only the degree of comminution assessment was not significantly different between treatments. The 5.25% and 7% treatments were more rubbery than the other three treatments. Ease of fragmentation decreased with increasing added myosin, except for 5-25% and 7% treatments which were similar. The 0%, 1-75% and 3.5% treatments were more tender than 5.25% and 7% treatments. The 0% treatment was much drier than the others. Acceptability of fragmentation showed no clear trend with myosin content, but there were individual differences between the treatments at the 5% significance level. Products with 3-5% crude myosin had the most acceptable texture. Correlations between the tactile and eating qualities with hedonic attributes (Table 3) showed tenderness had the highest correlation with both hedonic measurements. Ease of fragmentation was significantly correlated with acceptability of fragmentation (P < 0-001), although the agreement was low (r = 0"485). C o n s u m e r trial

Table 4 shows the effect of the concentration of added myosin on consumer liking of meat products. Added myosin had no effect on consumer liking of texture or their overall liking of the product. For both texture and overall liking the 0% treatment received the lowest score and the 1.75% treatment received the highest. Figure 1 shows the proportion of consumers who rated a particular meat product highest. For texture liking 26% rated the 1.75% sample highest, whereas for overall liking 30% rated the 7% sample highest. Instrumental Testing

Table 5 shows mean tensile adhesive strength (TAS) and punch and die strength (PS) values for samples with different levels of added myosin. PS values for raw samples were much lower than PS values for cooked samples. TABLE 4 Effect of Added Myosin on Consumer Liking of Meat Products Added myosin

Texture liking Overall liking

0%

1.75%

3"5%

5.25%

7%

51 48

56 53

54 50

54 51

52 51

Values are means. VR--varianc¢ ratio. dr---degrees of freedom. *°--not significant at the 5% level.

VR

df

0-56"" 0-43*"

4; 270 4; 269

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Andrew IV. J. Savage et al.

u) Z 0 0

~1 TEXTURELIKING • OVERALL LIKING

0

1.75

3.5

5.25

7

ADDED MYOSIN (%)

Proportions (%) of consumer panel who rated a particular meat product highest. For texture liking four consumers gave equal highest ratings to more than one product. For overall liking two consumers gave equal highest ratings to more than one product.

Fig. 1.

T h e o n l y set o f PS m e a s u r e m e n t s that were significantly affected by level o f a d d e d m y o s i n were m e a s u r e m e n t s o n c o o k e d samples tested at r o o m t e m p e r a t u r e . In b o t h sets o f p r o d u c t s tested a f t e r c o o k i n g the 0 % t r e a t m e n t s h a d slightly h i g h e r PS values t h a n the 1.75% t r e a t m e n t s . T h e two m e a s u r e m e n t s t h a t were highly significantly ( P < 0.001) affected by level o f a d d e d m y o s i n are s h o w n graphically in Fig. 2. T A S m e a s u r e m e n t s s h o w e d g r e a t e r d i s c r i m i n a t i o n between a d d e d p r o t e i n levels t h a n PS values. TABLE 5 Effect of Added Myosin on Objective Assessments of Adhesion Objective test

TAS (Pa.104) PS (Pa.104) Raw PS (Pa.104) Cooked, tested at 55°C PS (Pa. l04) Cooked, tested at room temperature

Added myosin

VR

Isd

0%

1"75%

3"5%

5"25%

7%

1"97 1-35

3"08 1-51

4"86 1-46

5"01 1"52

6"31 1'52

3.35

3.17

3.31

3"38

3"58

2"52"

3.14

3.07

3.10

3"32

3"63

8"79*** 0"23

70"4*** 0"59 0"63" 0"26 0"27

Values are means. VR--variance ratio, degrees of freedom -- 4; 32. *'--not significant at 5% level. ***--significant at 0.1% level. Isd--least significant difference, for significant differences between treatments at the 5% level.

Influence o f adhesion on acceptance o f a meat product

151

TAS

A

•

o

•I -

5

4

PS

Z ,,i n.

2.

i

i

i

i

i

0

1.75

3.5

5.25

7

ADDED MYOS4N(%)

Fig. 2.

Effect of level of added myosin on TAS and PS cooked, tested at 55~'C. Values are means, error bars are + 1 standard error of each mean.

The TAS values of two of the commercial products were between the TAS of the 0% and 1.75% treatments with the third product (the cheapest) having a TAS lower than the 0% treatment (Table 6).

Correlation between sensory data and instrumental data Table 7 shows the correlations between sensory and instrumental data. The sensory attribute most highly correlated with TAS was crumbliness on cutting, and this was also the highest correlation between a sensory and an instrumental measurement (r = -0"737). The highest correlation between an eating quality attribute and an instrumental measurement is between ease of fragmentation and TAS ( r = - 0 " 6 8 2 ) . The relationships between ease of fragmentation and overall acceptability of texture with TAS are shown in Fig. 3. There were no significant correlations between hedonic ratings and instrumental measurements and no significant correlations between PS on TABLE 6 Mean TAS of Three Commercial Products

Flaked and formed, 60*/. meat Flaked and formed, 95°/. meat Sliced and formed, 94*/0 meat

TAS (Pa.lO4)

Standard error

Number o f observations

I'06 2-47 2"66

O'lO O" 14 O" I8

23 24 24

152

Andrew W. J. Savage et al. TABLE 7 Correlations of Sensory Measurements with Instrumental Measurements

Firmness on cutting Crumbliness on cutting Fibrous particles on cutting Rubberiness Ease of fragmentation Degree of comminution Tenderness Moisture Acceptability of fragmentation Overall acceptability of texture Tensile adhesive strength

Tensile adhesive strength

Punch strength, raw

Punch strength, cooked, tested at 55~C

Punch strength, cooked, tested at room temperature

0.678*** -0-737***

0-261 -0-234

0-358* -0-147

0.467*** -0-352*

-0-643*** 0.464** -0.682*** 0.042 -0-369* 0.325*

-0.074 0' l I l -0.152 0.116 -0.127 -0.101

-0-283 0.507*** -0-239 -0-086 -0.377** -0.171

-0-290* 0.403** -0-470*** 0.117 -0.407** -0.184

-0-194

-0.004

-0"173

-0.277

0-061 --

0.115 0"251

-0.237 0.303*

-0.204 0"480***

*--significant at 5% level. **--significant at 1% level. ***--significant at 0.1% level. 70-

er

60

OVERALLACCEPTABILITY OFTEXTURE

o ¢o

¢,n ..J u.i z a.

50

EASEOF FRAGMENTATION 40

!

i

!

l

i

i

2

3

4

5

6

7

TAS (1~.104)

Fig. 3.

Relationship between ease of fragmentation and overall acceptability of texture with

TAS. Values are means.

153

Influence of adhesion on acceptance of a meat product

raw p r o d u c t s a n d s e n s o r y attributes. PS o n c o o k e d p r o d u c t s tested cold was m o r e significantly c o r r e l a t e d with firmness a n d ease o f f r a g m e n t a t i o n t h a n PS o n c o o k e d p r o d u c t s tested hot; the o p p o s i t e is true for rubberiness. T h e highest c o r r e l a t i o n b e t w e e n the two i n s t r u m e n t a l m e t h o d s was between T A S and PS o n c o o k e d samples, tested at r o o m t e m p e r a t u r e (r = 0"480).

Analytical data and cooking data T a b l e 8 shows the c h e m i c a l analysis o f raw a n d c o o k e d samples. T h e r e were no significant differences in raw c o m p o s i t i o n b e t w e e n t r e a t m e n t s . T h e effect o f a linear increase in the level o f a d d e d m y o s i n was n o t clear f r o m the a n a l y s e d p r o t e i n d a t a p r o b a b l y because the e x p e c t e d differences in overall p r o t e i n levels were o f the same o r d e r as the a c c u r a c y o f the p r o t e i n assay. A f t e r cooking, there were significant differences in protein, fat and m o i s t u r e with level o f a d d e d myosin. As the a m o u n t o f a d d e d m y o s i n increased, the

TABLE8 ChemicalAnalysisofRawand CookedSamples Added myosin

VR

lsd

17"16 17-50 17"36 17.52 17.74 3.00 2.65 2.78 2.74 2.91 77.77 77.93 77'45 77-18 76.64 1'36 1'30 1"33 1"31 1'29 0'61 0.62 0"61 0-60 0-61 0-72 0-47 0-63 0-83 0-66

2.06"' 0-16"' 2.78"~ 0.43"' 0"19"' 4-27"'

0-58 1"37 1-20 0-17 0-06 0.25

31.07 29.40 29.03 27.98 29.29 5-46 4.97 4-39 3-83 4.12 59.61 62"38 63-19 64.29 62.88 1'74 1'72 1'77 1.78 1.77 0.74 0'76 0"77 0"76 0.75 1.36 1.18 1.09 1.07 1.21

4-88"* 8.03°** 6'01 °* 0-50"' 0.94"' 1.39"

1.49 0-69 2-11 0- I 1 0-03 0-39

0%

1"75% 3"5% 5"25%

7%

Raw samples

Protein (%) Fat (%) Moisture (%) Ash (%) Sodium chloride (%) Collagen (%) Cooked samples

Protein (%) Fat (%) Moisture (%) Ash I%) Sodium chloride (%) Collagen (%)

Values are means. VR--variance ratio, degrees of freedom = 4; 4 for data on raw samples and collagen data on cooked samples and 4; 19 for other data on cooked samples. "'--not significant at 5% level. **--significant at 1% level. ***--significant at O-1% level. Isd--least significant difference, for significant differences between treatments at the 5% level.

Andrew IV. J. Sa~,age e t

154

al.

46

44 42 ¸

¢n 0

40-

38-

8

~

36-

'

34-

32

~ 0

, 1.25

i 3.5

~ 5.25

7

MYOSIN (%)

Fig. 4.

Effect of level of added myosin on cooking loss. Values are means of data for all cooked samples, error bars are ___1 standard error of each mean.

percentage of protein and fat decreased and the percentage of moisture increased. The effect of level of added myosin on the cooking loss is shown in Fig. 4. There was a marked decrease in cooking loss as the amount of added myosin increased, and this was clearly observed during the cooking as a large a m o u n t of fluid coming from samples with lower amounts of added myosin, and especially those with no added myosin. There was a large variation in cooking loss within any one treatment attributable to a large variation in temperature from the front to the back of the grill. Cooking loss was reduced from about 44% to 34% as the protein concentration in the crude myosin adhesive solution was increased. Reduction in cooking loss was most marked when the added protein concentration was raised from 0% to 1.75%. The decreased cooking loss with increasing amount of added myosin, together with the chemical analysis of cooked products suggests that the composition of the cooking loss is richer in moisture and poorer in fat and protein than the meat products.

DISCUSSION The sensory panel were clearly able to detect differences in attributes relating to adhesion between the five experimental meat products. The differences follow a general pattern that may be expected; firmness on cutting increases with increasing myosin concentration, crumbliness on cutting and ease of

Influence of adhesion on acceptance of a meat product

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fragmentation on eating decrease with increasing myosin concentration, and low to medium concentrations of myosin were perceived as more tender than products with higher levels of added myosin. All these effects may be explained on the basis of increasing added myosin levels producing a more coherent and firmer product. It is less easy to rationalise why changes in added myosin concentration should affect the perceived fibrousness of particles on cutting, or moistness. However, it is fair to conclude that, by altering the concentration of added myosin between the five products, differing levels of adhesion or bind have been achieved which can easily be discriminated sensorily, as well as instrumentally. Two interesting further points arise from the sensory analysis. The first concerns the increase in perceived rubberiness with increasing added myosin concentration. In meat processing it is common experience that overmixing results in a rubbery product due, it is believed, to increasing myosin extraction from the mixed meat pieces, so forming a more concentrated binding gel. Our findings, that increasing added myosin concentration does indeed result in increased rubberiness, support this view. The second point is that, although moistness significantly varied across the five treatments, only those with 0% added myosin differed from the others. This may be due to the added myosin in the other four treatments serving to form a water-holding gel and so reducing the water loss on cooking (Fig. 4). Having established that the different level of added myosin produced discernibly different products, the consumer acceptability trial allows us to relate sensorily perceived differences in adhesion to product acceptability. The consumer trial showed no significant differences for either liking of texture or overall liking (Table 4). There is no clear agreement between texture liking and overall liking, and no clear pattern of liking of texture and overall liking with added protein level. Given that people were discriminating between the products and the results are not essentially random, this could be due to preferences being averaged out, by some people liking weakly bound products with others preferring strongly bound products (Nute et al., 1988). Support for this interpretation may be obtained from the answers to the hedonic questions asked of the sensory panel. Figure 5 shows how consistently three of the ten panellists, chosen as examples of people with different preferences, rated a particular product highest for overall acceptability of texture. One panellist consistently rated highest the products with lower amounts of myosin (Panellist 1, Fig. 5), whilst another rated highest the products with higher amounts of myosin (Panellist 3, Fig. 5). No individual product was preferred by everybody. Taking the result of the sensory panel and the consumer acceptability trial together, this suggests that, although differences in bind can easily be perceived, the assumption that an increase in adhesion gives a better product is not valid.

Andrew W. J. Savage

156

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I~1 PANELUST 2 17 PANELLIST 3 2o

8

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Fig. 5. Histograms of proportion (as %) of occasions that individual paneilists rated a particular product highest, or equal highest, for overall acceptabilityof texture. TAS showed the largest difference between the added myosin treatments of the instrumental tests used. TAS varied almost linearly with increasing amount of added myosin, in agreement with the results obtained by Siegel and Schmidt (1979) who demonstrated a linear relationship between binding strength and level of crude myosin in a model system. The punch and die test did not discriminate between these products as well (Fig. 2) despite being highly significantly (P < 0.001) correlated with TAS (Table 6). One possible explanation for the similarity in punch and die measurements made on cooked products is that a hard crust had formed on the products during cooking under the grill. This crust may be of equal strength in each case and also the strongest part of the cooked product. If the crust had been removed, or if a gentler method of cooking had.been used, greater differences in PS between treatments may have been observed. Calculations of PS from the punch and die test using the formula given in the materials and methods above, assumes that the peak load is due to shear failure around the walls of a cylindrical plug displaced by the punch, i.e. it is calculated as a shear strength. These observations on the possible role of the hard crust on a product being involved in the resistance to penetration of a product indicate that this assumption should be questioned and critically examined in future work. TAS was most highly correlated with the tactile attribute crumbliness on cutting (r = -0-737) and the eating quality attribute ease of fragmentation (r = -0-682). TAS measurements would therefore seem to be good predictors for assessing these adhesion-related aspects of textural quality. The TAS

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range of the commercial products was at the low end of the range of TAS for the experimental products. Although the commercial products were chosen as extremes of price and meat content, they do not necessarily represent the full range of TAS values obtainable from commercial products. Punch and die tests on cooked products tested cold gave more differences between treatments than when tested hot. This could be due to an increase in stiffness of the heat-set myosin gel at the colder temperature. In conclusion, we have shown that differences in bind between meat products are detectable by a sensory panel using both tactile and eating quality assessments. Ease of fragmentation was the highest discriminator between treatments and was highly correlated with TAS measurements which were more discriminating than punch and die tests. Neither extremes of strong or weak bind were preferred (as assessed by the consumer study), but results from the sensory panel suggest that differences in individual preferences were responsible for this lack of trend overall. Hence, control of binding strength is important for product consistency but different sectors of the population prefer different levels of bind.

ACKNOWLEDGEMENTS The authors wish to thank Miss R. C. Higman and Mr R. G. Davison for performing all the chemical analyses and Mr C. B. Moncrieff for help and advice with the statistical analyses. REFERENCES Booren, A. M., Mandigo, R. W., Olson, D. G. & Jones, K. W. ( 1981a). J. Food Sci., 46, 1665. Booren, A. M., Mandigo, R. W., Olson, D. G. & Jones, K. W. (1981b). J. Food Sci., 46, 1673. Bostian. M. L., Fish, D. L., Webb, N. B. & Arey, J. J. (1985). J. Assoc. Off. Anal. Chem., 68, 876. British Standard Methods of Test for Meat and Meat Products (1979). BS 4401, Part 11, Determination ofL (-)-hydroxyproline content (reference method). BSI London. Chesney, M. S., Mandigo, R. W. & Campbell, J. F. (1978). J. Food Sci., 43, 1535. Donnelly, S. M. & Purslow, P. P. (1987). Meat Sci., 21, 145. Ford, A. L., Jones, P. N., MacFarlane, J. J., Schmidt, G. R. & Turner, R. H. (1978). J. Food Sci., 43, 815. Jones, R. C., Dransfield, E., Robinson, J. M. & Crosland, A. R. (1985). J. Text. Stud., 16, 241. Nute, G. R., MacFie, H. J. H. & Greenhoff, K. (1988). In Food Acceptability, ed. D. M. H. Thomson, Elsevier Applied Science, London, p. 377.

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Official Standardised and Recommended Methods of Analysis (1973). (2nd edn), ed. N. W. Hanson, The Society for Analytical Chemistry, London, p. 155. Perry, S. V. (1955). In Methods in En'.ymology, Vol. 2, ed. S. P. Colowick & N. O. Kaplan, Academic Press, New York, p. 582. Popenhagen, G. R. & Mandigo, R. W. (1978). J. Food Sci., 43, 1641. Purslow, P. P., Donnelly, S. M. & Savage, A. W. J. (1987). Meat Sci., 19, 227. Sheard, P. R. & Jolley, P. D. (1988). In Food Technology International Europe 1988, ed. A. Turner, Sterling Publications Limited, London, p. 129. Siegel, D. G. & Schmidt, G. R. (1979). J. Food Sci., 44, 1686.