This study evaluated the effects of dietary probiotic supplement and postmortem storage on meat quality of chicken breast during retail display. A total of 35 birds were randomly obtained from 3 feeding groups (control without probiotic supplement, 250 ppm Sporulin, and 500 ppm PoultryStar). The probiotic supplement had no influence on feed conversion ratio and body weight gain, as well as body weight at 29 and 44 d (P > 0.05). After slaughter, each side of the breast muscles (M. Pectoralis major) was assigned to either one d or 5 d of postmortem storage. Probiotic supplement had no influence on the rate of pH decline of chicken breast muscles during the initial 6 h postmortem (P > 0.05). No interactions between probiotic supplement and postmortem storage on meat quality were found (P > 0.05). Postmortem storage decreased drip loss from 25.30 to 18.05% (P < 0.05). Probiotics-fed chicken groups, particularly PoultryStar treatment, had a higher myofibrillar fragmentation index than the control group (P < 0.05). However, shear force values were not affected by the probiotic treatments. Decreases in color and lipid stabilities of breast muscles were found during display (P < 0.05), but were not affected by the probiotic supplement (P > 0.05). Our result suggests that probiotic supplement had no adverse impacts on proteolysis and oxidative changes during 5 d postmortem display storage.

Abstract. High pre-rigor muscle temperature has negative consequences on quality and has been predominantly studied in the excised longissimus muscle of beef and lamb carcasses. There is little data on other muscles, the application in whole carcasses or potential amelioration techniques such as stretching. This study evaluated the effects of electrical stimulation, high pre-rigor temperature and stretching of lamb sides on quality traits and protein denaturation in four leg muscles [gluteus medius (GM), rectus femoris (RF), semimembranosus (SM) and semitendinosus (ST)]. Twenty lamb carcasses were used with two electrical stimulation treatments (stimulated or non-stimulated, +/À) and two pre-rigor temperature treatments (chilled at 2 C directly after slaughter, or held in 37 C water for 4.5 h before transfer to a 2 C chiller) applied. One side of each carcass was suspended from the Achilles tendon, whereas the other side was stretched by allowing the leg to drop and tying it to the ribs. Electrical stimulation did not influence the different traits except for pH fall post slaughter and myosin denaturation. Stretching resulted in greater muscle and sarcomere lengths for the GM, SM and ST, but a decrease in sarcomere length for the RF. For the non-stretched GM and SM, the 37 C treatment resulted in tougher meat at 1 and 8 days post mortem compared with the 2 C treatment. In contrast, the stretched 37 C treatment resulted in more tender meat for the GM, SM and ST at 1 day post mortem compared with the 2 C treatment. For all muscles, the 37 C treatment resulted in a decrease in the waterholding capacity (increased purge, surface exudate and cooking losses). The magnitude of this effect was generally diminished by stretching for the GM, SM and ST, but for the RF, (which was not stretched by the treatment) this effect was reversed. The 37 C treatment resulted in paler meat (increased L*-values) for the GM, SM and ST relative to the 2 C treatment. The observed effects of the 37 C treatment on water-holding capacity and colour could be explained by the effects of this treatment on indicators of protein denaturation (sarcoplasmic protein solubility and myofibrillar ATPase activity), which were decreased for the GM, SM and ST. The response to both temperature and stretching varied between the muscles, due to different anatomical location and also due to postulated differences in the fibre types. In conclusion, pre-rigor stretching of lamb sides can counteract the negative effects of high early postmortem temperature on tenderness and water-holding capacity for those muscles that are stretched as a result of this hanging method.

Abstract. This study evaluated effects of high pre-rigor temperature and duration and suspension of lamb sides on quality traits and protein denaturation in two muscles [semimembranosus (SM) and longissimus thoracis et lumborum (LTL)]. Twenty-four lamb carcasses, within each of 3 slaughter days, were used to assign eight carcasses to one of four pre-rigor temperature treatments: chilled at 2 C directly after slaughter, or held at 37 C in water for 1.5, 3.0 or 4.5 h before transfer to a 2 C chiller. At~15 min post slaughter, one side of each carcass was suspended from the Achilles tendon, whereas the other side was suspended by the aitch bone and the leg tied down to the ribs. The sides subjected to aitch bone hanging had an increased sarcomere length in the SM, but decreased sarcomere length in the LTL. For the LTL, the time of exposure to high pre-rigor temperature had a significant effect on measures of protein denaturation and related meat quality traits such as purge and colour, although tenderness (shear force) after 2 days of aging was not affected. For the SM, the high temperature treatment also resulted in increase in measures of protein denaturation and thus negatively influenced meat quality traits such as purge, colour and shear force after aging. However, these effects on purge and shear force in the SM were significantly mitigated by the aitchbone hanging treatment. The results of the present experiment indicate that pre-rigor aitchbone hanging of muscles can counteract the negative effects of high pre-rigor temperature on both water loss and meat tenderness.