Effect of age and cut on the nutritional content of South African beef.

The physical composition and nutrient content of different age group carcasses and cuts of South African beef from equal fat classes were investigated. Carcasses from three different age groups and various fatness levels within each, were obtained on the commercial market. The physical composition of each right side cut (n=270) was assessed and analysed for raw nutrient content, while each left side cut was cooked prior to analyses. Physical composition of the carcass and cuts had the greatest effect on the difference between age groups, with meat and bone increasing with an increase in age. Protein increased (including eleven of the amino acids measured) and moisture content decreased with age in the cooked cuts. When physical composition was excluded, lysine and iron were higher and linoleic acid lower in older compared to younger animals, thus meat from older animals which is mostly consumed by people with severe iron-deficiency anaemia in the rural parts of South Africa, is adequate to meet this need. Lysine as one of the nine essential amino acids for adults, was higher in the C-age meat, contrary to belief that it is of inferior quality and can be recommended as part of a balanced diet. Palmitic acid (16:0) increased with age while Linoleic acid (18:2) decreased with age. Significant differences in fat content (subcutaneous and proximate), meat, moisture, various fatty acids (palmitic, stearic and oleic acids) and calcium were found between the different cuts. Hydroxyproline, glycine and some minerals discriminated the most between the different cuts within a carcass.

Characterisation of indigenous African cattle breeds in relation to meat quality traits.

Meat quality characteristics of two Sanga (indigenous) breeds (Afrikaner and Nguni), one indigenous composite breed (Bonsmara), one foreign composite breed (Santa Gertrudis) and two continental breeds (Brown Swiss and Pinzgauer) were compared. Means were adjusted for mean overall subcutaneous fat level (4.7%). Meat tenderness was then related to certain muscle characteristics. Shear force measurements indicated that Santa Gertrudis (SG) meat was significantly less tender than that of the two continental breeds and the three indigenous breeds (P<0.05). Pairwise linear correlations showed that differences found in background toughness (connective tissue) among breeds did not have a significant effect on tenderness. However, higher myofibrillar fragmentation indices, as well as lower white muscle fibre percentages for the three indigenous breeds, especially the two Sanga breeds, proved their potential to produce meat of comparable tenderness to that of continental breeds under specific slaughter and post-slaughter conditions.

Flavour- and tenderness-related quality characteristics of goat and sheep meat.

The quality characteristics of 27 Angora goats, Boer goats and sheep carcases were compared. Significant differences exist between the quality characteristics of sheep meat and Angora or Boer goat meat. Sheep meat has a more intense aroma, it is more tender, contains less fibrous tissue residue and the species flavour is more pronounced (typical) than that of Angora and Boer goat meat. In general, goat meat was found to be significantly different to sheep meat, the Angora to a lesser extent, however, than the Boer goat. This study confirms the fact that the meat of younger animals is more tender, contains less fibrous tissue residue and the species flavour is less typical than that of older animals. This was irrespective of whether it was obtained from sheep, Angora or Boer goat. With increasing fatness of carcases, the tenderness and species flavour of the cooked cuts increased significantly.

Cooking- and juiciness-related quality characteristics of goat and sheep meat.

Significant differences exist between the quality characteristics of meat obtained from 27 sheep, Angora and Boer goat carcases, when compared. Sheep meat showed greater drip loss than goat meat and was more juicy than that of Angora and Boer goat meat. In general, Angora goat meat was found to be more juicy than Boer goat meat. Drip loss increased significantly with increased animal age. Meat of younger animals (no permanent incisors) was more juicy (initial and sustained) than that of older animals (7-8 permanent incisors). This was irrespective of whether it was obtained from sheep, Angora or Boer goats and was confirmed by the expressible moisture measurements. Higher drip, evaporation and total cooking loss were reported when carcases had increased fat content. With increasing fatness of carcases, the juiciness of the cooked cuts decreased and the expressible moisture content of the meat increased.

Secondary sexual development (Masculinity) of bovine males: 1. Influence on carcass composition, cutability, economic value and certain muscles.

Differences in carcass composition, cutability, economic value of the carcass and distribution of certain muscle groups, between bulls with secondary sexual characteristics (bulls(+)), those without (bulls(-)), and steers were investigated. Two carcass mass groups (250-300 and 301-350 kg) were compared. Five carcasses of either mass group were studied within each sex condition group. Bulls(+) had a higher meat percentage (P < 0·05) than bulls(-) or steers. They also had a lower bone percentage than steers (P < 0·05), but non-significant differences were found between bulls(+) and bulls(-) for bone percentage. Significant differences (P < 0·05) between sex condition groups were found for percentages of hindquarter, as well as for distribution of high-priced cuts. Steers had the most favourable distribution and bulls(+) the least favourable. Bulls(-) were intermediate. Masculinity significantly (P < 0·05) influenced the distribution of the chuck, neck, brisket and hind shin cuts, whilst mass had a significant effect on the percentage hind shin and percentage thin flank. It was found that the M. rhomboideus was the only muscle of those studied that was significantly affected by masculinity and it was concluded that this muscle could be used as an indicator of the masculinity of the carcass. The economic values of the carcasses of steers, bulls without secondary sexual development and bulls with secondary sexual development differed non-significantly.

Secondary sexual development (Masculinity) of bovine males: 2. Influence on certain meat quality characteristics.

Differences in meat quality traits between bulls with secondary sexual development (bulls(+), n = 10), those without this development (bulls(-), n = 10) and steers (n = 10) were investigated. All animals had no permanent incisors (A-age group). Significant differences (P < 0·05) between bulls(+) and bulls(-) were found for the cooking loss percentage of the M. splenius (27·83% versus 31·11%, respectively), iron content of the M. splenius (56·02µg/g versus 49·43µg/g, respectively) and total collagen content of the M. splenius (3·74 versus 4·73 measured as Hyp N/Tot N x 1000, respectively). Drip loss of the wingrib cut (4·01% versus 5·18%, respectively) was also significantly different between bulls(+) and bulls(-). For the M. longissimus thoracis, no significant (P < 0·05) differences in any of the quality-indicating parameters investigated could be found. It is concluded that the M. splenius can be used as an indicator muscle for masculinity, based on meat quality attributes. This is supported by the correlation coefficients obtained between masculinity and the intramuscular collagen content of the M. splenius (r = -0·55) and the iron content of the M. splenius (r = 0·46). For all the other quality attributes investigated, non-significant (P > 0·05) differences between the three sex condition groups were found. It is concluded that the influence of masculinity on meat quality traits of young bulls is of little practical importance in a classification and grading system.

The influence of different centralised pre-packaging systems on the shelf-life of fresh pork.

The influence of different centralised pre-packaging systems (PVC, modified atmosphere packaging (MAP), 25% CO(2) and 75% O(2), vacuum skin packaging (VSP) and the mother bag concept, 100% CO(2)) on the shelf-life (0, 7, 14 and 21 days at 0°C) of fresh pork was determined using microbiological, colour, odour and acceptability characteristics. All the packaging treatments were equally efficient for the first 4 days of retail display. In the extended shelf-life study (7, 14 and 21 days) the mother bag centralised packaging system gave the most promising shelf-life results (21 days) and was also judged superior in terms of odour. Modified atmosphere packaging (14 days) and VSP (7 days) may be considered as other possible options.

A microbiological survey of fresh meat in the supermarket trade. Part 1: Carcasses and contact surfaces.

Sanitary conditions were monitored at eleven supermarkets (from two major chains, Sup groups A & B) in the South African butcher industry. The variables measured were the temperature of carcasses and environments, the muscle pH of carcasses and the microbiological status of carcasses and human or personal and equipment contact surfaces (chillers-three surfaces, delivery trucks-five surfaces, cutting rooms-16 surfaces). All supermarkets, except one, received beef carcasses, distributed by one of two wholesale organizations from the same abattoir. No consistency was found in the contamination level of different parts of carcasses at different supermarkets, although there was a tendency for fore quarters to be more contaminated than hind quarters. Chiller surfaces, delivery truck surfaces and equipment had significantly different microbial counts at the different supermarkets. Sup group B received carcasses with higher mean surface temperatures and microbial counts than those of the carcasses received by Sup group A, but the mean microbial count of equipment was lower than that encountered at Sup group A. The result was less contaminated meat at the supermarkets in Sup group B, illustrating how a combination of the microbial quality of carcasses received by such supermarkets, and the sanitary programme in operation at such supermarkets affects the contamination level of retail premises. It could furthermore be shown that personnel surfaces (hands and clothes) and equipment like saws and mincers are consistent contributors to contamination at the retail level of the meat industry.

A microbiological survey of fresh meat in the supermarket trade. Part 2: beef retail cuts.

An assessment was made of the microbiological quality of the final product (different retail cuts), produced by two different retail supermarket groups (A & B). The influence of sanitary conditions on the microbiological quality of the final product was evaluated, and the possible influences on shelf life were determined. Supermarket group A (Sup group A) received carcasses with significantly lower surface counts of micro-organisms than supermarket group B (Sup group B), while the latter had a more efficient overall sanitation programme than supermarket group A. Five cuts were monitored for the presence of total aerobic counts, psychrotrophic counts, lactobacilli, Enterobacteriaceae and numbers of Pseudomonadaceae present. A shelf life study was also executed by repeating these enumerations on the same meat samples after refrigerated storage at 5°C for 2 and 4 days, respectively. It is generally accepted that a good refrigeration or chilling regime will preserve the inherent meat quality, but in this study it was found that neither served as a guarantee of quality. The more stringent hygiene at retail level of Sup group B yielded consistently lower mean counts of the different bacterial groups for all the meat cuts monitored and, thus meat with an extended shelf life. The total count (at 30°C) on meat cuts was the highest, followed by the psychrotrophs, the Pseudomonadaceae the Enterobacteriaeae and the lactobacilli. Minced meat generally had the highest mean aerobic total microbial counts. This count on minced meat might be a suitable indicator for monitoring the overall sanitary condition of a retail premises. The results re-emphasized the multi-factorial complexity of fresh meat quality and shelf life. The microbial quality of the raw material (carcasses), the maintenance of the cold chain, sanitary condition of premises, equipment and personnel surfaces and general management practices are factors that collectively determine the microbiological quality of the product.

Effects of Exercise, Electrical Stimulation and Vacuum Packaging on Bacterial Counts and Tenderness of Fresh Beef Primal Cuts.

Two wholesale cuts, the silverside ( M biceps femoris ) and bolo, (outside round and clod) from 8 steers were used in this study. Four steers were artificially stressed and the right side of all carcasses was electrically stimulated. Primals were cut into 3 equal portions after 72 h post slaughter, chilling at approximately 4°C, and were vacuum packaged. No microbial differences (P>0.05) were found between primals within treatments. Primals from stressed carcasses had higher pH values (P<0.01) and psychrotrophic, lactobacillus, anaerobic and aerobic counts than from nonstressed carcasses. Lactobacilli did not dominate the microbial population. Electrical stimulation (ES) and the cuts used had an influence on shear force values (P<0.05). ES cuts were significantly more tender than controls. Results suggest that animals should be well rested before slaughter.

Evaluation of Three Carcass Surface Microbial Sampling Techniques.

Three carcass surface microbial sampling techniques were evaluated: a double swab, an excision and an agar sausage technique. In each instance, a sampling area of 6,42 cm2 was used. For the double swab technique, two sterile dry swabs were used. A sterile meat borer was used to cut out the area of 6,42 cm2 for the excision technique. For the agar sausage technique, 50-cm3 medical syringes were used to take impression plate samples. All the samples obtained with the different techniques were subjected to serial dilutions, whereafter they were spread-plated in duplicate on prepoured plates. Results of the study indicated that there was a significant difference (P<0,05) between the three techniques. The excision technique was the most reliable while the agar sausage technique had a higher coefficient of determination (r2 value) with the excision technique than did the swab technique.

Microbiology of Beef Carcass Surfaces.

In a survey at a local abattoir, agar sausage samples were taken at 10 carcass sites on each of 156 beef carcasses at different positions along the dressing line. The carcasses were selected to include all carcass types, viz. small (< 200 kg) and large (> 200 kg) as well as lean and fat carcasses. The 156 carcasses were divided into three groups of 52 carcasses each. Samples were incubated at three different temperatures to determine the aerobic count, mesophilic count and psychrotrophic count. Results of the survey showed that despite mean initial counts of 4,5-7,7 × 102, intermediate handling and the subsequent contamination that took place along the dressing-line, the final chilling process rendered carcasses with acceptable bacterial levels(< 2,5 × 102).

The influence of age, sex and breed of cattle on their muscle characteristics.

In order to gain more knowledge of the systematic changes occurring in meat tenderness and colour of different breeds and sexes of growing cattle, a number of characteristics were studied in five different muscles of Afrikaner and Friesland bulls and steers between birth and 24 months of age. Muscle collagen content of bulls was higher at birth than at all other ages and solubility of collagen decreased markedly between birth and 16 months of age. Shear force increased between 8 and 16 months, partially coinciding with the decrease in collagen solubility. Collagen content of muscles was higher in bulls than in steers and solubility decreased markedly between 12 and 16 months, only in the case of bulls. Afrikaner muscles were more tender than those of Frieslands and had a higher content and solubility of collagen. Pigment content was higher in Afrikaner than in Friesland muscles and increased steadily with age in all animals. The results show that the biological differences found to influence muscle characteristics were particularly those of age and breed of animal.