Assessment of commercial lamb meat quality by British and Spanish taste panels

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.SO309-1740(97)OOOltO-6

Meat Science, Vol. 48, No. l/2, 91-100, 1998 0 1997 Elwier Science Ltd All rights reserved. Printed in Great Britain 0309-1740/98 $19.00+0.00

ELSEVIER

Assessment of Commercial Lamb Meat Quality by British and Spanish Taste Panels C. Safiudo,“* G. R. Nute,b M. M. Campo,a G. Maria,a A. Baker,b I. Sierra,a M. E. Ense@ & J. D. Woodb “Department of Animal Production, University of Zaragoza, 50.013 Zaragoza, Spain bDivision of Food Animal Science, University of Bristol, Langford BS18 7DY, UK

(Received 14 May 1997; revised version received 30 June 1997; accepted 3 July 1997)

ABSTRACT Trained sensory panels in Britain and Spain assessed loin meat from commercial lambs purchased in Spain, which included Welsh lamb (imported from Britain) and two Spanish breeds (Merino and Rasa Arugonesa). The British panel also assessed British lamb purchased in local butcher shops and supermarkets. Sensory panels. in each country, received meat from the same lambs and used their local methods of cooking and assessment. Spanish panels used unstructured line scales to measure lamb odour intensity, tenderness, juiciness, IambJIavour intensity and two hedonic scales ofJIavour liking and overall liking. The British panel used 8 point category scales with the same attributes. Results from both panels in objective parameters were in agreement, hence showing that different trained sensory panels may arrive at the same conclusion. However, when panellists were allowed to make hedonic judgements (preference), the British panel preferred British lamb and the Spanish panel preferred Spanish lamb. This finding has important consequences for lamb producers who export their lambs and demonstrates that the underlying reasons for different preferences should be investigated. Production variables are discussed in relation to their influence on Iamb eating quality and us a way to tailor lamb eating quality attributes familiar to consumers in the importing country. 0 1997 Elsevier Science Ltd. All rights reserved

INTRODUCTION

The meat of small ruminants, especially lamb and mutton, comprises a large proportion of protein foods and commercial inter-change occurs in many areas of the developed world. Its quality depends on an array of factors including feed type, age of weaning and slaughtering, castration policy, adult size, maturity, processing and post-mortem ageing. These factors vary regionally, especially between northern European and Mediterranean countries and domestic and export markets (Kilkenny, 1990). To encourage further development of the European Union lamb industry, it is essential that lamb farmers know how the characteristics of national lamb products are perceived *To whom correspondence should be addressed; e-mail: [email protected] 91

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by consumers in target markets of other EU countries. This is especially important when cooking and cultural backgrounds differ among consumers. Applying this knowledge could be a way to develop the sheepmeat market, since lamb farmers would have information to meet the requirements of their customers. Field et al. (1983) were the first to emphasize the link between cultural background and food acceptability. They found that consumers in the USA (a country with low lamb consumption per capita) dislike lamb odour and flavour, while those in New Zealand (with a much higher level of lamb consumption) find these attractive. Subsequent works, each using national panels, have analyzed the influence of these different geographical sources in meat sensorial quality (Jeremiah, 1988; Saimdo et al., 1992). Also, Griffin et al. (1992) evaluated meat sheep palatability in the USA using two sensory panels, one composed of assessors from various cultural backgrounds and the other with native assessors. But, only meat produced under USA conditions was assessed. At present there is little information about the assessment of the same lambs, produced in different countries, by the corresponding national panels, using their local cooking methods. This was the aim of the present stidy. MATERIALS

AND METHODS

LNllbS

Thirty-two commercial lamb carcasses were studied. Twenty-four were purchased in Spain and eight in England. In Spain, all lambs were light carcass males (range 104J11.5 kg cold weight) bought in commercial markets: eight Spanish Merino (ME), eight Rasa Aragonesa (RA) and eight British export carcasses (BE). The ME were bred in an extensive system in south-western Spain. After weaning they were stabled and fed ad libitum with concentrate and cereal straw until slaughter at 80-90 days. The RA, a rustic medium wool breed from north-eastern Spain, were produced in an intensive-housed system, weaned and kept on concentrate ad libitum and cereal straw until slaughter at 80-90 days. The BE were Welsh lamb wethers kept on an extensive diet (pasture). They were slaughtered at 5-6 months in Britain and sent, refrigerated, to Spain. The carcass weight and shoulder composition of these lambs are shown in Table 1. In England, eight ‘early lambs’ (range 16.5-l 8.5 kg cold carcass weight) were purchased (BP) around Easter from traditional butchers and supermarkets in the North Somerset TABLE 1

Carcass Weight and Shoulder Composition Lmnb type

Half carcass weight (g) Shoulder weight (g) Muscle weight (g) Bone weight (g) Fat weight (g) Other tissues (g) Disection losses (g)

in Three Types of Light Lambs. Means and Standard Errors

Spanish Merino breed (ME)

Mean 5401 997-6 641.7 1955a 122.5b 21.5 16.4

SE 148.91 291.11 19.71 4.71 13.42 2.09 2.15

Rasa Aragonesa breed (RA)

Mean 5311 996.8 632.7 192.9a 135.3b 22.3 13.6

SE 92-52 20.11 16.59 5.11 14.00 1.97 2.31

British export (BE)

Mean 5235 986.6 603.6 177.4b 161.8a 25.3 18.5

n= 8 in each lamb type. Values in the same row with different letters are significantly (within trait) (p < 0.05).

SE 16664 33.23 29.54 8.01 15.63 1.54 3.03 different

Assessment of commercial lamb meat qualityby British and Spanish tastepanels

93

area. Lambs had been suckled and given concentrate to aid early growth and then finished on early season grass.

Sampling Ageing time (at 3°C) was 3 days post-slaughter for ME and RA and 3 days post-purchase for BE. Loin joints were obtained, vacuum packed, blast frozen and kept at -20°C until tasted. Left side loins remained in Spain and right ones were sent to England. Samples from BP carcasses were vacuum packed and blast frozen on the day of purchase and stored at -20°C. Only right loins were tasted in England. Spanish panel Before cooking, samples were thawed for 24 hr and m. longissimus lumborum (LD) was then removed, trimmed of all fat. The epimysium was left intact. A trained taste panel of 11 panellists assessed lamb odour intensity, tenderness, juiciness, flavour intensity, flavour quality and overall appraisal on a scale of 1 to 100. The left end of the scale (= 1) was labelled: non odour, extremely tough, extremely dry, no flavour, dislike extremely flavour and dislike extremely; the right end (= 100) was labelled: very strong lamb odour, extremely tender, extremely juicy, very strong flavour, like extremely flavour and like extremely. Panel training was broadly in line with those methods stated in IS0 8586-l (1993) with additional methods specifically for meats. LD was grilled until the internal temperature reached 70°C which is normal in Spanish cooking conditions, and then it was cut in 20mm slices. The samples were served hot and each trio (ME, RA, BE) was randomly evaluated within each panel (88 judgements). British panel The entire loin joints were thawed for 24 hr before cooking and tasted by a 10 member trained panel. The same attributes used in Spain were evaluated using an 8 point category scale. Entire joints were cut in 20mm slices and then cooked under conventional grill conditions to an internal temperature of WC, which is normal in British cooking conditions. Only LD was assessed. The four lamb types (ME, RA, BE, BP) were randomized within each panel session (80 judgements). A place for unsolicited comments was also provided. Data analysis Data were analyzed using the GLM procedures of the SAS package (SAS, 1985) with the model: y = xb + e, where y was a N x 1 records, b denoted the fixed effect (lamb type) with an association matrix x and e denoted residual effects. Data from Britain and Spain were analysed separately. RESULTS

AND DISCUSSION

General results The influence of weight, age, fatness, breed, diet or production system have been previously studied (Cramer et al., 1970; Kemp et al., 1981; Field et al., 1983; Notter et al., 1991; Bosman et al., 1994) but rarely in light lambs as in the present study.

94

Overall, there is some confusion about the influence of plane of nutrition or fatness on lamb meat characteristics. Lambs on low energy diets (such as British lambs in this study) are usually fed forages and lambs on high energy diets (such as Spanish lambs in this study) are usually fed grain. Therefore, there is a confounding effect since energy level and feed-type can not be separated. Age effect is also present and difficult to isolate. In this study significant differences were found, between British and Spanish lamb meat, for all sensory characteristics (Table 2). On average, and in accordance with results obtained in similar works in Spain (Saiiudo et al., 1992) and Britain (Dransfield er al., 1979), the meat was comparatively tender and juicy and the flavour had a medium intensity. Odour and flavour intensity Odour and flavour are important aspects of meat quality, sometimes used as a determining criteria in the acceptance or rejection of the product, especially in lamb and mutton meats (Mottram, 1994). These quality criteria are affected by more factors than any other (Rhodes, 1971; Notter et al., 1991), which adds more complications in interpretation. Both panels rated odour and flavour intensities of British meat higher (~~0.05) than Spanish meat. This is in agreement with our previous results (Safiudo et al., 1992), where flavour intensity from British light lamb was also higher than Spanish lamb (75.3 vs 68.3, on an l-100 point scale). In the current study, odour intensity differed between meats (~~0.01) by 13.0% in the British panel and 9.1% (p
Spanish Merino breed (ME)

Rasa Aragonesa breed (RA)

British export (BE)

Early British purchase (BP)

Mean

SE

Mean

SE

Mean

SE

Mean

SE

2.83’ 51.956

0.20 2.14

2.69b 58.47b

0.16 1.34

4.03” 67.34”

0.21 1.99

3.58”

0.21 -

6.21” 72.52”

0.14 2.06

5.306 58.46b

0.14 1.64

6.45a 69.32”

0.15 2.06

6.05a -

0.14

5.18” 64.05”

0.12 2.01

513”b 61.69n

0.12 1.39

5.05”b 45.1 lb

0.14 2.23

4.776 -

0.13

3.036 63.55b

0.17 1.94

3.176 58.20c

0.16 1.23

4.45” 73.72”

0.19 1.82

3.91”

0.18

3.346 5779”

0.17 1.72

3.356 59.42”

0.15 1.13

4.52” 33.146

0.20 1.85

4.03”

0.20

3.496’ 59.48”

0.16 1.92

3.43’ 57.82”

0.15 1.34

4.14” 32.01b

0.20 2.01

4.096

0.19

Lamb odour intensity

British panel Spanish Panel Tenderness British panel Spanish panel Juiciness

British panel Spanish panel Lamb flavour intensity

British panel Spanish panel Flavour quality

British panel Spanish panel Overall appraisal

British panel Spanish panel n=88

for Spanish panel and n=80 for British panel. Values in the same row with different letters are significantly different (within trait) (p < 0.05). The British panel used 8 point category scales. The Spanish panel used 100 mm line scales.

Assessment of commercial lamb meat quality by British and Spanish taste panels

95

The higher odour and flavour intensities of the British lamb showed that meat of older lambs had superior odour or flavour scores than meat of younger animals (Crouse et al., 1981). On the other hand, production system and feed-type (grass vs concentrate) probably had more influence on our results than energy level. A higher plane of nutrition, such as in the Spanish system, produces fatter carcasses and more flavoured meat (Crouse et al., 1983; Schiinfeldt et al., 1993), which is true only when animals are slaughtered with a similar grade of maturity. But, in our samples, British lambs were older and consequently fatter. Nevertheless, the relationships between fatness and flavour rest in controversy, probably because many confounding factors are implicated. Fatty acid composition should also be considered. The differences between ME or RA (breed effect) and between the British carcasses (weight and breed, main effects) were not significant in the British or Spanish panels. This could indicate the secondary importance of breed or weight in odour and flavour intensity, as compared to age or production system. This concurs with the findings of Dransfield et al. (1979), Solomon et al. (1980) and Crouse et al. (1981, 1983), who report that breed does not need to be considered by the lamb industry to make production management decisions related to flavour. Also, it is possible that our differences in weight may not have been great enough to modify meat flavour (Kemp et al., 1976; Webb er al., 1994; Saiiudo et al., 1996). Tenderness Tenderness is a predominant quality criteria of red meat (Wheeler and Koohmaraie, 1994), although probably more so in beef than in lamb meat. For both panels, RA was significantly (p < 0.05) less tender than ME and British lamb. Similar differences between RA and British meat have been observed previously (Safiudo et al., 1992). In the current study the difference between RA meat tenderness and ME and British meat tenderness was, on average, 11.7% (p < 0.01) in the British panel and 12.5% (p < 0.01) in the Spanish panel. No significant differences were found between ME and British carcasses or between BE and BP lambs. There was no substantial evidence from these results to suggest that production system, weight or age, significantly affected tenderness. This also confirms the large variability in the findings of other authors regarding production system effects. Thus, although meat from lambs fed low energy diets was evaluated to be less tender than meat from lambs fed high energy diets (Rhodes, 1971; Summers et al., 1978; Kemp et al., 1981), other work shows that grazing lambs had more tender meat than those lambs fed with concentrate (Notter et al., 1991). On the other hand, British lamb is generally considered to be tender and less tough than other meats (Wood and Fisher, 1990). This is probably due to an adequate fatness and chilling rate, which are important factors in determining eating quality. Thus, the higher tenderness of British lamb, in comparison with RA, could be related to its higher fatness level and adequate protection from cold shortening and to differences in ageing time (Jaime et al., 1993). One or more days may have elapsed from slaughtering to freezing in the British animals in comparison with the Spanish lambs, since more time was required for transport and distribution. It is accepted that lamb meat tenderness increases after 72 hr storage (Wheeler and Koohmaraie, 1994). Also, it is possible that RA had comparatively a low collagen solubility, especially in this weight range. Safiudo et al. (1996) found higher toughness in carcasses of 10.22 kg (as in this study) than in carcasses of 8.07 or 13.42 kg. The higher tenderness of ME lambs, in comparison with RA, could be explained by their high average daily gain (animals that had showed compensatory growth), which

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produces an increase in soluble collagen. This has been demonstrated in beef (Aberle et al., 1981), and we have also detected a positive effect of this compensatory growth in lamb palatability traits (Saiiudo et al., 1992). Juiciness Both panels scored juiciness higher for Spanish lamb than for British lamb. This agrees with our previous findings (Safiudo et al., 1992). These differences were statistically significant (p < 0.01) in the Spanish panel (17.8%) and between ME and BP in the British panel (p < 0.05), which judged Spanish meat to be only 3.0% more juicy than British meat. Our results agree with other findings that show that breed or weight effects are not important in juiciness, and that juiciness is slightly higher in younger lambs. However no explanation was given for these findings (Mendenhall and Ercanbrack, 1979; Bosman et al., 1994). Rhodes (1971) and Touraine et al. (1984) found that juiciness from animals fed high energy diets tended to have superior scores than meat from animals fed low energy diets. These differences were attributable to differences in fatness. In the current study, British carcasses were fatter than Spanish carcasses. Therefore, differences in marbling do not seem important in explaining differences in juiciness. Previous findings have shown that older animals have meat with lower water-holding capacity (WHC) than younger animals (Safiudo and Sierra, 1982; Hawkins et al., 1985). This could have contributed to the lower juiciness of British meat. Flavour quality and overall appraisal Consumer preferences of lamb carcasses have not been completely defined and literature is scarce. Cultural background or sensory habit (sensorial adaptation to specific colours, textures, flavours, etc.) could be an important aspect of acceptability. In the United States, lamb is considered more undesirable in odour than other meats, while in Spain the first criteria for lamb purchase (53%) is its agreeable odour and flavour (Laajimi, 1991). In the British panel British meat flavour was considered 21.8% (p < 0.01) more acceptable than Spanish lamb flavour, and the overall appraisal of British lamb was, on average, 22.6% higher (p < 0.01). In the Spanish panel, the Spanish lamb flavour and overall acceptability were 43.4% and 45.4% (p < 0.01) more acceptable than British lamb flavour and acceptability. Thus, the British panel preferred (p < O-01) British meat and the Spanish panel preferred (p < 0.01) Spanish meat. This agrees with our previous findings, in which Spanish panels and consumers preferred young lambs from intensive production systems rather than imported lambs from Britain or NZ, with higher flavour intensity (Safiudo et al., 1989, 1992). Several works have found an influence of breed, diet or fatness on acceptability. In general, the breed effect is not considered important, except when woolly or hair breeds are compared (Webb et al., 1994). On the other hand, diet or fatness effects are disputed because, although most of them indicate that meat from lambs fed with concentrate or higher fatness received more desirable scores (Kemp et al., 1976; Summers et al., 1978; Melton, 1990) there is a convincing wealth of information indicating that lamb flavour is not associated with fatness (Paul et al., 1964) and that diet does not appreciably affect palatability (Crouse et al., 1978). A few studies have indicated that flavour desirability is associated with lamb fatness, but were conducted when consumers preferred fat meat, as suggested by Field et al., (1983). With the results of the current study a new interpretation could be made: acceptability depends on the panel’s previous knowledge of product or consumption habits. Comparable results were found by Griffin et al. (1992). They did not

97

Assessment of commercial lamb meat quality by British and Spanish taste panels

find differences in flavour intensity, juiciness and tenderness scores between domestic versus foreign panels for loin chops, but overall palatability was lower for the domestic panel, which was less familiar with small ruminant meats than the foreign panel. The relationship between consumption habits, or knowledge of the product, and acceptability could be understood by considering the unsolicited comments of British assessors (no space for comments was provided in the Spanish panel). A total of 33 adjectives were used but only 19 were used twice or more within each lamb type (Table 3). Of these 19 adjectives, three (livery, greasy/fatty and venison) comprised 82.9% of the comments about British meat. However in the Spanish meat, 10 or 11 adjectives were needed to arrive to a similar percentage of comments. This could be due to the difficulty in describing a new and unknown product. At least some of the judges found the British meat more ‘greasy/fatty’ (Hofstrand and Jacobson, 1960) and also more like ‘livery and venison’, probably because it came from older animals with stronger odour and flavour (Jeremiah, 1988). Liver-like flavour was also the off flavour most often indicated by Rhee et al. (1990) and gamey, similar to venison, the second (Crouse et al., 1983). Surprisingly, Spanish meat was considered more ‘metallic’ than British meat, although the British meat was darker because of its higher age and subsequently had a higher iron content. A higher iron content could have consequences for odour and flavour; since haem iron can act as a catalyst for lipid oxidation (Rhee, 1988) with consequent effects on taste (Young et al., 1993). Finally, the British panel did not find higher foreign odour for the British meat.

Unsolicited

Comments

TABLE 3 given by British Assesors to Grilled Lamb Loins from Four Different Sources Lamb type

Adjectivef Livery Greasy/fatty Metallic Acidic Odd Venison Skatole Beef Pork/bacon Bitter Urine/kidney Rubber Plastic Sweet Raw Minty Sticky Dish cloth Barbecue Number of descriptors

Spanish Merino Rasa Aragonesa British export Early British Totals breed (ME) breed (RA) purchase (BP) (BE) 12 8 7 5 5 3 4 3 6 4 -

1

9 13 8 7 6 7 4 6 3 2 3 2

26 22 2 4

2 13

-

2 2 13

“Used two or more times within each lamb type.

5

25 18 3 2 3 6

2 3 -

-

6

8

72 61 20 18 14 11 10 8 8 8 6 6 3 3 2 2 2 2 2 19

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C. Sariudo et al.

Since adjectives are highly subjective, they were only presented to aid future research and the development of a more descriptive profile of flavour. In general it is possible to conclude that British and Spanish commercial lambs are two different products. The similarity between the results of the British and Spanish panels with regards to odour and flavour intensity, tenderness and juiciness confirms the efficiency of sensory analysis and its high comparative value. The differences between the British and Spanish panels in flavour and overall acceptability showed that these parameters depend upon the preferences and culinary habits of the test panel.

ACKNOWLEDGEMENTS We are grateful to the Consejo Regulador de Ternasco de Aragon for supporting this work and to S. Hughes, G. Fursey, B. Panea and J. J. Pardos for their technical assistance.

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