Cameron Jose

This study evaluated the impact of high oxygen modified atmosphere packaging (MAP) in four different combinations, 80 % oxygen and 20 % carbon dioxide (MAP80), 40 % oxygen, 20 % carbon dioxide and 40 % nitrogen (MAP40(20CO2)), 40 % oxygen, 60 % carbon dioxide (MAP40(60CO2)), and vacuum skin packaging (VSP) under different retail display times (3 or 8 days) on the sensory scores of lamb meat. Untrained consumer sensory scores for overall liking, tenderness, juiciness and liking of flavour were assessed on the M. longissimus lumborum (loin) and M. semimembranosus (topside) of 144 lambs. In general, MAP40(20CO2) samples received higher sensory scores than MAP80 (P < 0.05). While the high carbon dioxide MAP mixture MAP40(60CO2) scored similar to MAP80 (P > 0.05). Therefore, MAP40(20CO2) minimised the detrimental effects on eating quality and is a viable alternative to the widely used MAP80. However, the highest eating quality scores were still obtained with VSP (P < 0.05).

Meat colour is an important attribute for consumer acceptance but there is an interval between colour grading and retail display. This experiment investigates the effect of time post-slaughter (5, 14 and 40 days) on colour and bloom depth (after 1 and 24 h) for beef carcasses graded AUS-MEAT colour 4 (MC 4). Sixteen carcasses were selected at grading, 8 carcasses were graded MC 4 and 8 as compliant colour (AUS-MEAT score 2 or 3). At 5 days post-slaughter, compliant loins had greater overall bloom depth and were more red than MC 4 loins. Bloom depth (24 h) increased with ageing time but reached maximum bloom at 14 days for both treatments. After ageing for 14 and 40 days, the bloom depth of MC 4 loin was no different to the 5 day aged compliant loins after 24 h on display. Colour at grading may not be a reliable measure of retail colour considering the changes post slaughter.

Hot boning (HB) is an economical processing technique often resulting in poorer meat quality and tenderness. This study tested a method of partial HB, where the short loin section was removed from the hot carcass and chilled, with the striploin remained in the skeletal system. Thirty six yearling Bos indicus steers carcasses were subjected to either low, high or no electrical stimulation and each side allocated to a cutting treatment of HB, partial HB and conventional (Achillies hung). Striploins were divided into 3 and aged for 5, 14 and 28 days. Warner Bratzler Shear force (WBSF) and sarcomere length were tested. Partial HB resulted in greater tenderization without aging compared to HB. However, optimized electrical stimulation was a requirement. Treatment did not influence sarcomere length. The study also tested the impact of Dry aging of HB striploins, which resulted in further increases in tenderness at 28 days of aging compared to wet aged product, reducing WBSF by 9 N.

This study investigated the effects of vitamin E, electrical stimulation, aging and packaging system on the colour stability of lamb meat. Eighty crossbred wether lambs, 6–8 months old were fed on either vitamin E or control pelleted diet for 31 days prior to slaughter. Half of the carcases from each group were electrically stimulated before being split longitudinally into 2. Each side was randomly allocated 1 of the 4 aging periods (5 days fresh, 10, 20 and 30 days CO2). Muscle samples were set for retail display, after the respective aging period, colour was measured over 96 h. Supplementing vitamin E nutritionally is likely to lengthen the shelf life of lamb products aged longer than 10 days. Muscle vitamin E concentrations > 3.0 mg/kg are required to increase the shelf life of lamb cuts aged for up to 30 days to 60 h. Medium voltage electrical stimulation did not have a detrimental effect on the display life of aged lamb meat.

The relationship between vitamin E supplementation rate and colour stability was investigated using 70 mixed sex 6-8 month old crossbred lambs. An initial group of 10 were slaughtered, while the remainder were fed a pellet ration containing either 30, 150, 275 or 400IU vitamin E/kg ration or on green pasture for 56days. After slaughter, carcases were halved; one side packed fresh (5days) and the other in CO2 (21days), both at 2°C. Five muscles were set for retail display for 96h. The oxy/metmyoglobin ratio was measured every 12h. Colour stability increased with increasing muscle vitamin E until an apparent maximum effect for vitamin E concentration (3.5-4.0mg α-tocopherol/kg tissue) was reached beyond which no further response was evident. This was reached within 3-4weeks (275IU treatment), and meat from these lambs should reach 60h retail display with a satisfactory surface colour. This effect was most apparent in aerobic muscle types and meat aged post slaughter.

A 4 × 3 factorial experiment (n= 8 pigs per treatment combination) was conducted with 96 female Landrace × Large White pigs to examine the required level of dietary vitamin E and optimum feeding duration before slaughter to maximise muscle vitamin E content in the Longissimus thoracis et lumborum (LTL) muscle. The respective factors were four dietary levels of vitamin E (supplemented as dl-α-tocopheryl acetate; 35, 300, 500, and 700 IU/kg) and three feeding durations (14, 28 and 42 days before slaughter). Vitamin E concentration in the LTL was maximised at 6 mg/kg, which was achieved by feeding a 700 IU vitamin E diet for 28 days before slaughter (P < 0.001). There was no further increase in the vitamin E content of the LTL by feeding the high vitamin E diet more than 28 days before slaughter.

Dark cutting is detrimental to meat quality and therefore is the major cause of carcass downgrades under the Meat Standards Australia grading system. This study quantified the variation between months in the incidence of dark cutting, in southern Australia. Four years of Meat Standards Australia grading data, from nine individual beef processors in Western Australia, South Australia, Victoria and Tasmania, was utilised for the analysis. The dataset contained 42162 slaughter groups, of 10 or more grass-fed cattle, which allowed for the percentage of dark cutters per slaughter group to be analysed. The interaction between month, year and state was significant (P < 0.001). The lowest risk of dark cutting for South Australia and Western Australia was in October (1.53% ± 0.75 and 6.96% ± 0.76) and November in Tasmania and Victoria (7.34% ± 0.9 and 5.27% ± 0.81) potentially when feed availability and quality is highest. The incidence of dark cutting was highest for all states during the period from February to June. Lower pasture availability and quality in combination with higher levels of stress due to extreme high or low temperatures during this time could all contribute to the higher incidences. The findings of this study show that procurement and management decisions made by cattle buyers, producers and processors need to change throughout the year to help mitigate the incidence of dark cutting carcasses and reduce financial loss.

The interaction between blood glutathione (GSH) and supplementation of selenium (Se, 2.5 mg/kg diet) on meat colour and fatty acids concentrations was studied. Forty eight Merino lambs selected for high blood GSH (HGSH) or low GSH (LGSH) concentration were used. They were fed individually with or without Se supplement for 8 weeks. There were interactions (P< 0.05) between GSH and Se on the colour stability (as w630 nm/w580 nm ratio) of m. longissimus (LD), m. semimembranosus (SM) and m. semitendinosus. Without Se supplementation the ratio was higher in HGSH than LGSH group. However, the difference was reduced with Se supplement. Polyunsaturated and n-3 fatty acids in SM and LD were higher in HGSH than in LGSH group (P< 0.05), and did not change with Se supplement. Se supplementation increased Se content in LD (P< 0.001) and the lungs (P< 0.05), but had no influence in the heart.

In the eyes of the consumer, a red surface color of lamb meat is desirable. This red color is caused by oxymyoglobin; however, under conditions of retail display this pigment slowly oxidizes and turns brown, deterring consumers. The antioxidant activity of both glutathione (GSH) and selenium has been suggested to slow myoglobin oxidation, thus improving color stability. The following experiment was designed to test the hypothesis that high muscle GSH will improve the color stability of lamb meat, and this effect of GSH will be further improved by supplementing animals with selenium. Forty-eight 12-month-old Merino wether lambs were selected from a flock for high (n = 24) or low (n = 24) GSH concentration in whole blood. Each GSH group was then randomly allocated into two selenium treatments (supplemented with or without 2.5 mg of selenium/kg for 8 weeks). The lambs were slaughtered, and samples were taken from m. semimembranosus (SM) and m. longissimus dorsi (LD) to measure muscle GSH, selenium, and vitamin E concentrations. Further samples were taken to measure color stability (as oxy/metmyoglobin ratio, reflectance at 630/580 nm) over 96 h of retail display. There was no effect of muscle GSH concentration or selenium supplementation on oxy/metmyoglobin ratio at 60, 48, or 30 h of retail display, with the only exception being the non-selenium-supplemented SM samples, which actually decreased in ratio as the muscle GSH concentration increased (P < 0.05). There was a poor correlation between blood and muscle GSH, with a correlation coefficient of 0.18 for the SM and 0.026 for the LD. Thus, it is apparent that neither GSH nor selenium improved the color stability of meat from merino lambs.

This study investigated the effect of computerised tomography imaging (CT scan), for carcase composition determination, on the oxy/metmyoglobin ratio, hue and L∗, a∗ and b∗ scores of M. longissimus dorsi from both beef and lamb. Beef and lamb M. longissimus dorsi were divided into four proportions and randomly allocated to one of the following treatments; CT 30 day aged; CT fresh; control 30 day aged; control fresh. Colour measurements were made over a 96 h retail display period. CT scan had little effect on the colour of both lamb and beef across all colour parameters. There was a small negative affect observed in CT aged samples (P < 0.05) for ratio, hue, a∗ and b∗ values, however these differences were so small that they are unlikely to impact upon the commercial shelf-life of the product. Other factors such as aging, species and vitamin E concentration play a much greater role in colour stability than CT. Aged M. longissimus dorsi clearly had a worse colour stability than the fresh packaged samples, while beef was a lot more colour stable than lamb. It appears that CT scan for the purpose of body composition determination will not have any commercially relevant impact on colour stability of both beef and lamb.