Elsevier

Meat Science

Volume 60, Issue 2, February 2002, Pages 125-132
Meat Science

Dietary manipulation of muscle long-chain omega-3 and omega-6 fatty acids and sensory properties of lamb meat

https://doi.org/10.1016/S0309-1740(01)00113-9Get rights and content

Abstract

The effects of dietary manipulation of muscle long-chain omega-3 fatty acids (FA) on sensory properties of cooked meat in second cross ([Merino×Border Leicester]×Poll Dorset) wether lambs were evaluated. Lambs fed dietary supplements of fish meal (FM, Exp. 1) and fish oil (FO, Exp. 2) showed moderately (P<0.01) and markedly (P<0.001) increased muscle long-chain omega-3 FA content compared with those fed the basal diet of lucerne chaff and oat chaff. Protected canola seed (PCS, Exp. 1) significantly (P<0.001) increased omega-6 FA content of the longissimus muscle. In each of the 2 experiments (1 and 2), after being fed experimental diets for 6 weeks lambs were slaughtered at a commercial abattoir. At 24 h post-mortem (PM) the semitendinosus and biceps femoris muscles were removed from animals and stored at −20°C until evaluation of sensory properties using experienced panel members. The muscle samples were stored for 3 (Exp. 1) and 12 (Exp. 2) months then removed, thawed and cooked for sensory evaluation. The meat samples were cooked under standardized conditions in a convection microwave at 180°C (20–25 min) to an internal temperature of 75°C. Cooked samples were tested for flavour, aroma, juiciness and overall palatability. The significant increase in muscle long-chain omega-3 with FM (Exp. 1 and 2) and FO (Exp. 2) or omega-6 FA with PCS (Exp. 1) were not detrimental to sensory panel evaluations of flavour or aroma of cooked meat when compared with the basal diet. However, meat from FM (Exp. 1) had lower juiciness and FO (Exp. 2) had lower overall palatability. Protected sunflower meal protein with FO (Exp. 2) significantly lowered ratings for flavour, juiciness and overall palatability. Lamb meat with increased levels of long-chain omega-3 FA can be produced without altering the sensory quality (flavour or aroma) of the cooked meat.

Introduction

Meat, poultry and fish products are widely sought for their distinctive and highly valued flavours. Meat consumption and consumer appraisal of meat products are influenced by the flavour/aroma (odour) contributed by volatile compounds from modified fatty acids (FA) in meat during cooking and/or development of rancid substances, due to lipid oxidation during storage of meat. Deviations from normal flavour are not uncommon in meat and fish products, however, result in lower preference by consumers (Gray, Gomaa, & Buckley, 1996). Among sheep meat characteristics, flavour and aroma (odour) are the most important sensory properties affecting consumption of lamb (Young, Berdague, Viallon, Rousset-Akrim, & Theriez, 1997). These characteristics may originate from feed-derived substances in lipid or non-lipid compounds or from oxidative off-flavours, which develop during storage of meat.

Pearson, Gray, Wolzak, and Horenstein (1983) reported the development of off-flavours or odours (rancidity) was a serious problem during storage of meat products. Oxidative rancidity of muscle systems begins shortly after slaughter and involves the production of a complex mixture of aldehydes, ketones and alcohols (Morrissey, Buckley, Sheehy, & Monahan, 1994), which continue to increase in intensity until the meat product becomes unacceptable to consumers (Gray et al., 1996). However, Young et al. (1997) demonstrated all aldehydes and ketones were not associated with rancid odour but saturated aldehydes, like hexanal, have classically been associated with development of rancidity in lamb meat.

Other reports have indicated meat lipids are responsible for development of species flavours, such as those permitting the recognition of pork, beef or lamb. Such species-common properties are attributed to the formation of volatile compounds such as unsaturated aldehydes, fatty acids, methyl ketones and saturated aldehydes, particularly during cooking (Brennand and Lindsay, 1982, Dwivedi, 1975). Present research has improved the nutritional value of lamb by significantly increasing long-chain omega-3 FA content through dietary manipulation (Ponnampalam et al., 2001a, Ponnampalam et al., 2001b). In the research reported here, we have investigated the effect of altered muscle polyunsaturated fatty acid (PUFA) content on flavour, aroma, juiciness and overall palatability of lamb as assessed by a sensory panel.

Section snippets

Materials and methods

For the experiments reported here, the animal management, dietary treatments and slaughter procedures have been reported previously (Ponnampalam et al., 2001a, Ponnampalam et al., 2001b). In brief, crossbred ([Merino×Border Leicester]×Poll Dorset) wether lambs were brought in from late-spring pasture and were randomly allocated to individual pens and housed indoors for six and 6-week experimental periods in Exp. 1 and 2, respectively. All lambs used in the experiment had been ear-tagged and

Results

The fat content and FA profiles of diet and muscle have been reported in previous publications (Ponnampalam et al., 2001a, Ponnampalam et al., 2001b). In the present study, only FA composition of phospholipid (PL) fraction in LT muscle is reported, since PL in muscle are considered to be responsible for major effect on sensory properties of meat through lipid oxidation (Buckley et al., 1989). The effects of dietary supplements on the FA composition in PL of muscle LT observed in Exp. 1 (stored

Discussion

The aim of the present study was to evaluate the effect of dietary manipulation of muscle PUFA, particularly long-chain omega-3 FA, on sensory properties of cooked lamb meat. Although it would have been preferable for samples taken from the same LT muscle were used for all measurements, but due to the small lamb muscle size and several other measurements that were being taken, alternative muscles were used. Although fibre types between muscles were quite different, major differences in fat

Conclusions

The substantial increase in long-chain omega-3 FA observed with fish products (FM and FO) and in omega-6 FA observed with PCS in LT muscle did not adversely affect the flavour, aroma or overall palatability of cooked lamb meat. This may have been due to a species effect associated with development of sensory properties during cooking or due to the dietary (nutritional) background associated with the enrichment of vitamin E in the muscles. Feeding sunflower meal protein together with fish oil

Acknowledgements

This research was partially funded by the University of Melbourne, Australia and Meat and Livestock Australia Pty. Ltd. Protected feed supplements were kindly provided by RUMENTEK Industries, Australia. Authors would like to thank Mr. Andre Thalan for his technical support during slaughter of animals and muscle sample preparation.

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