Browsing by Author "Marais, Schutz"
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- ItemMeat quality of electrically stimulated game under variable harvesting conditions in South Africa(Stellenbosch : Stellenbosch University, 2013-03) Marais, Schutz; Hoffman, Louwrens C.; Simmons, N. J.; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences.ENGLISH ABSTRACT: In South Africa, game species are harvested throughout the year under variable circumstances, presenting a wide range of temperatures and environmental conditions. The latter can include extremely cold (night harvesting – winter < 5°C) or extremely hot temperature conditions (day harvesting – spring > 35°C). These unique harvesting conditions can negatively affect the game meat quality. Electrical stimulation (ES) has become an important intervention in commercial abattoirs to maintain or improve the meat quality. Electrical stimulation was originally applied to prevent cold shortening (CS) of muscles (i.e. cold induced toughening of muscles) in extremely cold conditions (< 10°C), but ES is also applied to accelerate ageing and to decrease the variation in the quality of meat products. When ES of carcasses is combined with the use of post rigor rapid chilling techniques, it can be extremely beneficial to both the supplier and consumer of game meat. Unfortunately, limited research is available on the use of ES on African game carcasses. The objective of this study was therefore to investigate the effect of ES on the meat quality of South African game carcasses. The latter consisted of two trials: the aim of the first trial was to investigate the effect of ES on the meat quality of commercially harvested springbok M. longissimus dorsi (LD) during night harvesting conditions; and the aim of the second trial was to investigate the effect of ES and rigor temperature treatment (5°C and 39°C) on the meat quality of blesbok LD muscles over time. For the first trial, 35 springbok were harvested during commercial night harvesting operations. Electrical stimulation was applied on 16 springbok within 45 minutes post mortem, while 19 were non ES animals and therefor used as the control. The pH decline was recorded in the LD muscles until rigor, after which general meat quality analyses (pH, tenderness, cooking loss, purge loss and colour) were performed on days 2, 5 and 21 post mortem. The ES muscle samples had lower (P ≤ 0.05) initial pH values compared to the non ES samples, however, the pH decline profiles and ultimate pH values (pHu) were similar for both ES and non ES samples. For each time point and both genders, no differences (P > 0.05) were present in the mean muscle tenderness of the ES and non ES muscle samples. The purge and cooking losses did not differ (P > 0.05) between treatments for days 2 and 5, although on day 21 the storage purge losses were 5.20% ± 0.31 (ES) compared to 4.30% ± 0.31 (non ES). The retail colour stability and regression of the colour measurements over time also did not differ (P > 0.05) between treatments. However, the ES samples had a higher rate of increase in colour sharpness (chroma regression data) (0.567 ± 0.108) compared to the non ES samples (0.224 ± 0.099). It was postulated that ES did not enhance the desired meat quality attributes i.e. tenderness, due to various external factors (animal age, stress and time post mortem prior to stimulation) which could have resulted in varying results. In the second trial, 20 mature male blesbok were harvested of which 10 animals were ES within 45 minutes post mortem and 10 non ES animals were used as control specimens. Meat quality analyses (pH, colour, purge loss, cooking loss and tenderness) were also performed during this trial on days 0 (rigor), 1, 2 and 5 post mortem. Electrical stimulation decreased the initial pH decline as well as the time to the onset of rigor mortis. The mean pH of the 5°C ES (5.75 ± 0.07) and non ES muscle samples (5.98 ± 0.06) at rigor, were lower (P ≤ 0.05) compared to the ES (5.55 ± 0.14) and non ES samples (5.37 ± 0.03) at 39°C. At 5°C, the ES muscle samples (80.34 ± 5.64) were more tender (P ≤ 0.05) compared to the non ES samples (101.95 ± 4.59) at rigor, although no differences (P > 0.05) were present for days 1, 2 and 5. All of the 39°C ES muscle samples (rigor, 57.05 ± 5.20; day 1, 48.37 ± 3.68; day 2, 46.06 ± 3.56 and day 5, 39.94 ± 3.46) were more tender (P ≤ 0.05) than the non ES samples (rigor, 79.37 ± 9.48; day 1, 74.41 ± 5.40; day 2, 75.52 ± 7.11 and day 5, 66.18 ± 6.14). Electrical stimulation was therefore only successful at increasing the tenderness of the 5°C muscle samples at rigor, but ES was very effective at increasing the tenderness of the samples for each time point at the higher temperature treatment (39°C). The water holding capacity (WHC), cooking loss percentages and bloomed meat surface colour of the blesbok LD muscles were unaffected (P > 0.05) by ES. At each time point the 39°C muscle samples had lower (P ≤ 0.05) mean WHC compared to the 5°C samples. The mean purge losses were higher (P ≤ 0.05) in the non ES (7.13% ± 0.30) compared to the ES (4.89% ± 0.32) muscle samples. However, the mean purge losses were higher in the 39°C (7.31% ± 0.30) compared to the 5°C (4.67% ± 0.29) muscle samples. Additionally, the mean purge losses increased (P ≤ 0.05) over time (day 1, 4.63% ± 0.41; day 2, 5.91% ± 0.34 and day 5, 7.47% ± 0.39), which will possibly have negative affects on consumer perception of blesbok meat quality. The mean cooking loss percentages were higher (P ≤ 0.05) in the 39°C (26.93% ± 1.04) compared to the 5°C (21.33% ± 1.29) muscle samples at rigor, although the opposite was true for days 2 and 5 (5°C: day 2, 28.06% ± 0.67 and day 5, 27.72% ± 0.57; 39°C: day 2, 25.60% ± 0.56 and day 5, 25.65% ± 0.72). All of the 39°C bloomed colour measurement values were higher (P ≤ 0.05) compared to the 5°C samples and the former stayed more or less constant over time. Although the 5°C colour measurement values improved over time, it never reached similar values to that of the 39°C samples. The use of ES under commercial game harvesting conditions requires further investigation; since the expected positive effects on the meat quality parameters were not found to be conclusive in this study. Extremely high temperatures during the harvesting of South African game species will negatively affect most of the meat quality attributes of blesbok LD muscles, while extremely low temperatures will most probably only have a negative affect on muscle tenderness. The application of ES may hold great benefits for the South African game industry, but further research is essential to endorse the application of ES on game species and to manage the factors affecting its effectiveness during different harvesting conditions.