J Babol

Free range rearing of pigs with access to pasture grazing — effect on fatty acid composition and lipid oxidation products

The influence of free-range rearing, RN genotype and sex on different pig meat quality traits, including intramuscular fatty acid composition and levels of lipid oxidation products, were studied. A total of 60 Hampshire crossbred pigs were reared outdoors for two months with access to green feed, while 60 others were kept indoors, in a 120-m(2)-large pen, throughout the rearing period. From these 120 animals a subsample of 44 animals was chosen for meat quality analysis. Of the three factors studied, the RN genotype had the largest influence on basic technological meat quality traits, whereas the rearing conditions and sex had limited effects. However, outdoor rearing resulted in higher levels of polyunsaturated fatty acids in the intramuscular fat (P=0.026) and in an increased level of vitamin E (P=0.030) compared with the pigs that had been reared indoors. The sex and RN genotype of the animals also had an effect on the fatty acid profile: females had higher levels of unsaturated fatty acids (P=0.003) as well as lower levels of saturated fatty acids (P=0.011) than castrated males. Carriers of the RN(-) allele expressed a higher sum of omega-3 fatty acids (P=0.047) and C22:5 (P=0.012) than did the non-carriers. In a storage study where meat from free-range and indoor reared pigs was stored for 3 months at-20°C, it was shown that the lipid oxidation product malondialdehyde was formed at increased levels in animals that had a higher lean meat percentage than others, i.e. females that were carriers of the RN(-) gene and that were reared outdoors.

The effect of age on distribution of skatole and indole levels in entire male pigs in four breeds: Yorkshire, Landrace, Hampshire and Duroc.

High skatole and to a lesser degree indole levels in some entire male pigs result in occurrence of off-flavor in meat, called boar taint. In this study, plasma samples from 117 Yorkshire, 134 Landrace, 184 Hampshire and 75 Duroc entire male pigs collected at different ages were analyzed for skatole and slightly fewer samples for indole concentrations. For each breed, a distinct age-related distribution of plasma skatole levels was observed. Skatole levels were increased at approximately 180-200 days of age, reaching very high levels is some individuals. Afterwards, the levels decreased; in Yorkshire and Landrace at approximately 240-260 and in Hampshire and Duroc at 310-360 days of age. The decrease of skatole levels was also observed in samples collected from 15 Landrace boars at two different ages: 16.8 μg/L (SD=17.36) vs. 5.9 μg/L (SD=3.48, p=0.016) in samples taken at the mean age of 210 and 314 days, respectively. Indole levels showed similar age- and breed-related variations to skatole. At the time of increased skatole concentrations (age from 180 to 360 days, depending on breed) 25.5% of Yorkshire, 31.6% of Landrace, 20.3% of Hampshire and 61.1% of Duroc entire male pigs had skatole levels above 12.6 μg/L of plasma, which corresponds to the threshold level of 0.20 μg/g of fat that is used for selecting tainted carcasses. The results indicate that increased levels of skatole in entire male pigs are related to puberty and taking skatole measurements at that age could be advantageous when considering genetic selection to reduce boar taint level in entire male pigs. Breed differences should be also taken into account.

Muscle lipids, vitamins E and A, and lipid oxidation as affected by diet and RN genotype in female and castrated male Hampshire crossbreed pigs

The objectives of this study were to investigate the polar and neutral lipid fatty acid composition, content of retinol, α-tocopherol, γ-tocopherol and level of oxidation of the pig muscle (M. longissimus dorsi). Female and castrated male Hampshire crossbreeds were produced in two systems. One group was raised indoors with a more polyunsaturated diet and the other raised outdoors with a more saturated diet. The level of polyunsaturated fatty acids in muscle was higher in the indoor females compared with the outdoor females, indoor castrated males and outdoor castrated males. The increased level of polyunsaturated fatty acids in the muscle, which was accompanied by a relatively low content of α-tocopherol, increased the susceptibility to lipid oxidation in the form of MDA (malondialdehyde) in the indoor female pigs. Finally, the level of polyunsaturated fatty acids in the polar lipids was affected by the RN genotype, and this difference was dependent on sex. In conclusion, diet has a major effect on the fatty acid composition and oxidation stability in pork muscle, but additional factors such as sex and RN genotype might also contribute.

Factors affecting the level of boar taint in entire male pigs as assessed by consumer sensory panel

A sensory study was conducted to determine consumer responses to meat from entire male pigs in order to evaluate different factors involved in causing boar taint, including 16-androstene steroids, skatole, size of accessory sexual glands and live weight. Pork chops from 33 entire Yorkshire male pigs were divided into three groups according to the levels of 16-androstene steroids in salivary glands, high (H; 56-114 μg/g), medium (M; 35-55 μg/g) and low (L; 26-6 μg/g), and were distributed among 59 families. Pork chops from gilts were used as control (C). The families were asked to rate liking of cooking aroma, flavour and texture, and overall liking. Consumer ratings were best related to the size of bulbourethral gland and salivary gland, followed by the levels of 16-androstene steroids in salivary gland. Meat from the L group received similar ratings to the C group, except the ratings for texture and overall liking were better than the C group. M samples were liked similarly to C, with the exception of some samples that had high fat skatole levels and which were liked less. H samples were liked less than C. The samples evaluated at the beginning of the experiment were liked more than those evaluated afterwards indicating sensitization of consumers to boar taint. The results indicate that levels of 16-androstenes in salivary glands can be used to estimate boar taint due to 16-androstenes; however, skatole measurements also need to be included. In addition, consumers are sensitive to some other maturity-related factors, which need to be considered when estimating the levels of boar taint. The effect of sensitization of consumers to boar taint requires more study.

Effect of rearing system on muscle lipids of gilts and castrated male pigs

The objective of this study was to investigate the polar and neutral lipid fatty acid composition of pig muscle as influenced by rearing conditions and sex. A total of 120 Hampshire crossbreeds were divided in two groups, one reared free-range in a strip grazing fashion and one reared indoors in a large pen (120 m(2)). Free-range rearing produced a more unsaturated fatty acid composition (M. biceps femoris) in the neutral lipids, although the effect was small. In the polar lipids the effect of rearing condition was sex dependent. In the muscle of free-range gilts, there was a higher level of C18:2 n-6, compared with indoor gilts, indoor castrates, and free-range castrates. Moreover, muscle of gilts irrespective of rearing condition, had a higher level of the C⩾20 polyunsaturated fatty acids in the polar lipids (16.75 and 14.60, respectively). Thus, we suggest that the difference between castrates and gilts with respect to fatty acid composition in the polar lipids, might be affected by rearing condition.

Meat quality, microbiological status and consumer preference of beef gluteus medius aged in a dry ageing bag or vacuum

This study investigated meat quality and consumer preference after ageing beef gluteus medius in a water vapour-permeable dry-ageing bag or in vacuum for 14 days. Higher ageing and trim losses but lower thawing loss, cooking loss and water content were found in samples aged in dry ageing bags compared to those aged in vacuum. Samples aged in dry ageing bags had higher total bacteria and yeast counts but lower lactic acid bacteria counts than those aged in vacuum, both before and after trimming. Meat aged in dry ageing bag was more tender and juicier and overall preferred by consumers compared with samples aged in vacuum. Female participants outperformed the males in detecting differences in palatability. No differences were found in pH, smell, shear force, colour, Enterobacteriaceae, and mould counts. Thus, by using a dry ageing bag, it is possible to produce dry-aged meat in a more controlled condition without negative effects on sensory or other quality attributes.

A comparative study of beef quality after ageing longissimus muscle using a dry ageing bag, traditional dry ageing or vacuum package ageing

The objective of this study was to investigate beef quality of longissimus muscle after ageing in dry ageing bags, traditional dry ageing or vacuum for 8 or 19 days. Lower ageing weight loss, odour score and microbial growth were found in meat aged in dry ageing bags than after traditional dry ageing. The sensory panel detected no differences for most of the sensory attributes between samples using the two dry ageing methods, except for the odour of the cutting surface. The dry-aged steaks had more umami and butter fried meat taste compared with vacuum-aged steaks. Ageing time affected most of the sensory traits in this study, which improved as ageing time increased from 8 to 19 days. In a consumer test, meat aged for 21 days in dry ageing bags was preferred than the samples aged in vacuum. This may be due to the higher tenderness and juiciness obtained during storage in dry ageing bags than meat aged in vacuum.