Tumbling of intact muscle foods has been widely applied toprocessed meats using brine solution. However, the use of tumbling withoutbrine on fresh beef muscles has not been fully examined. Therefore, this studyaimed to evaluate fresh beef tumbling on meat quality and proteolytic featuresof loin (longissimus lumborum)muscles. Moreover, interactions with the duration of postmortem aging wereinvestigated. Loins (n=9) at 7d postmortem were sectioned and allocated among twotumbling (T) treatment groups at 60 (T60) or 90 (T90) minutes, as well as a non-tumbledcontrol (T0) group. After treatment, sub-sections were made and divided among0d, 7d, or 14d of further aging. Meat quality was assessed by shear forcevalues, water-holding ability, and color attributes. The extent of proteolysiswas determined by quantification of desmin and troponin-T, myofibrilfragmentation index (MFI), and transmission electron microscopy. An interactionbetween fresh beef tumbling and aging duration was observed in shear forcevalues (P=0.032). At 0d, muscles fromT90 exhibited lower shear force (21.6 N) compared to T0 (34.8 N) and T60 (24.7N) groups. Muscles from T60 and T90 groups maintained lower shear force than T0controls at each respective aging duration.Higher cooking loss (P=0.011) but notpurge loss (P=0.412) was observed in theT60 and T90 groups compared to T0. Shear force results were supported by higherMFI in T60 and T90 groups than T0 controls (P<0.001), as well as the disappearance of intact troponin-T withfurther aging (P=0.009). Transmissionelectron microscopy supported increased initial tenderness would owe primarily tophysical disruptions to myofibrillar structure, though fresh beef tumbling may facilitateproteolysis with further aging.

Tenderness is an important sensory attribute to the overall eating experience of beef. Identifying novel methods to ensure consistent tenderness, especially in inherently tough cuts, is critical for the industry. This study investigated if tumbling without brine inclusion could be an effective method to improve the quality and palatability attributes of beef longissimus lumborum (LL) and semitendinosus (ST) steaks. Furthermore, interactions with postmortem aging were evaluated to determine how tumbling might affect protein degradation and muscle ultrastructure. At 5 d postmortem, pairs of LL and ST muscles from beef carcasses (n = 16) were bisected, vacuum packaged, and tumbled for 0, 40, 80, or 120 min. Sections were divided and subsequently aged an additional 0 or 10 d at 2 °C. Tumbling for any duration improved instrumental tenderness of LL (P < 0.001) but not ST (P > 0.05) steaks, regardless of aging time. Tumbling exacerbated moisture loss in both muscles shown by greater purge and cooking losses (P < 0.05). Myofibrillar fragmentation was induced through tumbling in both muscles (P < 0.001), which was supported by transmission electron microscopy images. Tumbling for 120 min followed by 10 d of aging resulted in less abundant intact troponin-T in both LL and ST (P < 0.05), as well as less intact desmin in ST (P < 0.05); however, calpain-1 autolysis was not affected by tumbling (P > 0.05). No effects of tumbling, aging, nor the interaction were found for the content and solubility of collagen (P > 0.05). Consumer panelists (n = 120/muscle) rated LL steaks tumbled for any duration higher for tenderness and overall liking compared to control steaks (P < 0.05). For ST, significant interactions were found for consumer liking of tenderness and juiciness. In general, tumbling without subsequent aging resulted in poorer juiciness than non-tumbled (P < 0.05), while at 10 d no differences in juiciness were found between treatments (P > 0.05). For ST steaks that were aged 10 d, 120 min of tumbling resulted in greater tenderness liking than non–tumbled steaks (P < 0.05). These results suggest that tumbling would result in myofibrillar fragmentation and may benefit the degradation of myofibrillar proteins; however, there would be negligible impacts on collagen. Accordingly, tumbling without brine inclusion alone may be sufficient to improve tenderness and overall liking of LL steaks, while combined tumbling with subsequent postmortem aging would be necessary to improve tenderness liking of ST.

The objective of this study was to evaluate the effects of photoperiod on meat quality, oxidative stability, and metabolites of broiler fillet (M. Pectoralis major) muscles. A total of 432 broilers was split among 4 photoperiod treatments [hours light(L):dark(D)]: 20L:4D, 18L:6D, 16L:8D, and 12L:12D. At 42 days, a total of 48 broilers (12 broilers/treatment) was randomly selected and harvested. At 1 day postmortem, fillet muscles were dissected and displayed for 7 days. No considerable impacts of photoperiods on general carcass and meat quality attributes, such as carcass weight, yield, pH, water-holding capacity, and shear force, were found (p > 0.05). However, color and oxidative stability were influenced by the photoperiod, where muscles from 20L:4D appeared lighter and more discolored, coupled with higher lipid oxidation (p < 0.05) and protein denaturation (p = 0.058) compared to 12L:12D. The UPLC–MS metabolomics identified that 20 metabolites were different between the 20L:4D and 12L:12D groups, and 15 were tentatively identified. In general, lower aromatic amino acids/dipeptides, and higher oxidized glutathione and guanine/methylated guanosine were observed in 20L:4D. These results suggest that a photoperiod would result in no considerable impact on initial meat quality, but extended photoperiods might negatively impact oxidative stability through an alteration of the muscle metabolites.

Long photoperiods are used in the broiler industry to maximize animal performance, though the impact on meat quality remains poorly understood. The current study evaluated the impact of photoperiod on functional/physicochemical properties and oxidative stability of meat through broiler processing. Ross 308 broilers (n = 432) were randomly assigned to 4 photoperiod treatments (hours in L = light, D = dark): 20L:4D, 18L:6D, 16L:8D, or 12L:12D with 6 pens per treatment. At 42 D of age, 2 broilers per pen (n = 12 per treatment) were harvested under standard conditions. Broiler tenderloin ( M. Pectoralis minor ) and leg muscles were removed at 1 D postmortem and frozen/stored at −40°C. After 24 h thawing at 2°C, the samples were deboned, ground, and formed into patties in 3 independent batches. Photoperiod had no impact on pH, water-holding capacity, textural profile, meat emulsion activity index, and thiol content ( P > 0.05). The patties from 12L:12D and 16L:8D had lower CIE b∗ (yellowness) values than 18L:6D and 20L:4D ( P < 0.05), whereas 12L:12D had lower chroma (color intensity) values than other treatments ( P < 0.05). The meat from 20L:4D exhibited lower sarcoplasmic protein solubility than other treatments ( P < 0.05), whereas both 20L:4D and 18L:6D exhibited lower total protein solubility than 12L:12D ( P < 0.05). Higher transmission values (indication of protein denaturation) were observed in 20L:4D than in other treatments ( P < 0.05), whereas 12L:12D also maintained lower values than both 18L:6D and 16L:8D ( P < 0.05). There was an interaction ( P < 0.05) between photoperiod and display storage on 2-thiobarbituric acid reactive substances values, where the patties from 12L:12D maintained less lipid oxidation compared with the patties from other treatments. Results of this study suggest photoperiod has limited impact on meat quality attributes, though rearing broilers with a 12L:12D lighting schedule may be beneficial in reducing protein denaturation and improving lipid stability.

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