Resumo Uma vez que o sistema calpaína é central para o amaciamento da carne e dada a importância da atividade de calpastatina na determinação da maciez de bifes de bovinos Bos taurus indicus, o objetivo do presente estudo foi determinar se a expressão do gene de μ-calpaína (CAPN1), calpastatina total (CAST T), e suas variantes (CAST I e II) foi induzido pela inclusão de vitamina D3 na dieta. Os animais receberam nenhuma ou 2 × 106 UI dose de vitamina D3 por 2 ou 8 dias antes do abate, e foram submetidos a diferentes condições durante o confinamento: exposição solar ou sombreamento artificial. Bifes do Longissimus lumborum foram fabricados e submetidos a maturação por 1, 7, e 21 dias post-mortem e posteriormente usados para determinação da força de cisalhamento e do índice de fragmentação miofibrilar. Vitamina D3 não influenciou a abundância de RNAm, exceto para maior abundância de transcritos de CAST II em animais que foram suplementados por 8 dias antes do abate. Foi encontrada associação negativa entre a abundância de CAST II e a força de cisalhamento. Essa contradição revela uma importante modulação da expressão do sistema calpaína resultado da suplementação com vitamina D que pode ser importante na determinação de estratégias para melhorar a maciez da carne.

ABSTRACT The calpain system is the central player for meat tenderization and the calpastatin activity plays an important role in beef tenderness of Bos taurus indicus cattle. This study investigated whether dietary vitamin D3 induced gene expression of μ-calpain (CAPN1), total calpastatin (CAST T), and their variants (CAST I and II). Animals received none or 2 × 106 IU of vitamin D3 for either 2 or 8 days before slaughter and were submitted to different conditions during feedlot: sun exposure or artificial shade. Steaks from Longissimus lumborum were fabricated, aged for 1, 7, and 21 days post-mortem, and later used for the analyses of shear force and the myofibrillar fragmentation index. Vitamin D3 did not influence mRNA abundance; however, it induced a greater CAST II transcript in animals supplemented 8 days before slaughter. There was a negative association between CAST II abundance and the shear force, which revealed an important modulation of the calpain system expression due to vitamin D supplementation. This result is an important tool for strategies to improve beef tenderness.

ABSTRACT: Bos taurus indicus temperament is variable and affects beef tenderization. Our objective was to investigate temperament and performance of non–castrated Nellore and identify groups based on Longissimus lumborum (LL) pH decline as well as beef characteristics produced by those groups. We investigated 94 animals with a subset of carcasses (n = 24) selected based on LL pH at 24 h postmortem (pm) to represent two groups: resistant to pH decline (> 5.8 called pH–Res; n = 10) and normal (< 5.7 called pH–Nor; n = 14). Steaks were fabricated from the LL muscle and randomly assigned to aging (2, 7, 14, and 21 days). Sarcomere length, cooking loss, myofibrillar fragmentation index (MFI), and Warner–Bratzler shear force (WBSF) were determined. Data on temperament were investigated in a multivariate approach, while beef data were compared between groups using the analysis of variance. Rectal temperature at the beginning of the finishing phase and total weight gain were greater and related to animals in the pH–Res group (p < 0.01 and p = 0.03, respectively). Temperature and pH decline curves, sarcomere length, and cooking loss revealed that pH–Res produced beef with lower quality compared to the pH–Nor group. Results for MFI and WBSF did not show differences between groups within each time pm; however, overall steaks from pH–Res were tougher (p = 0.06). Incidence of LL pH between 5.8 and 5.9 at 24 h pm did not compromise the tenderization rate or extension; however, it affected the water holding capacity in this population of Nellore cattle.

RESUMO Foram avaliados os efeitos do encurtamento normal (NS) e encurtamento pelo frio (CS) no comprimento do sarcômero, força de cisalhamento pelo Warner-Bratzler (WBS) e no processo de amaciamento analisado pelo índice de fragmentação miofibrilar (MFI). Os músculos Bicep femoris de dez ovinos oriundos do cruzamento Dorper x Santa Inês, foram aleatoriamente designados para: 1) NS: resfriamento do músculo na carcaça por 24 horas na câmara fria a 4°C (NS) 2) CS: resfriamento rápido, em banho de gelo, do músculo removido a partir da carcaça imediatamente após o abate (CS). Comprimento de sarcômero foi determinado nas amostras coletadas 24 horas após o abate e WBS e MFI nos períodos de maturação (1 ou 10 post mortem), em cada tratamento. Os valores de WBS da carne para 1 e 10 dias foram maiores (P <0,05) para CS (4,90 ± 0,42 e 3,73 ± 0,42 kgf, respectivamente) que para NS (4,07 ± 0,36 e 2,98 ± 0,38 kgf, respectivamente). Houve correlação negativa para WBS e comprimento do sarcômero (r = −0,59 e r = −0,69, P <0,05) nos dias 1 e 10 de post-mortem. Além disso, foram observadas correlações positivas entre MFI e comprimento do sarcômero (r = 0,46 e r = 0,48, P <0,05) nos dias 1 e 10, respectivamente. Esses resultados apontam para um impacto negativo do encurtamento do sarcômero no processo de amaciamento de carne em músculo do pernil de cordeiros.

SUMMARY This study evaluates the effects of Normal Shortening (NS) and Cold Shortening (CS) in sarcomere length, Warner-Bratzler shear force (WBS) and tenderization process examined by Myofibrillar Fragmentation Index (MFI). The Biceps femoris muscle from ten Dorper x Santa Inês lambs was randomly assigned to 1) NS = cooling of the muscle in the carcass for 24 hours in a cold room at 4°C; or 2) CS = rapid cooling, in ice bath, of the muscle removed from the carcass immediately after slaughter. Sarcomere Length (SL) was determined in the collected samples 24 hours after slaughter and WBS and MFI in the aging periods (1 or 10 days post-mortem). The WBS value of the meat for 1 and 10 days were greater (P<0.05) for CS (4.90 ± 0.42 and 3.73 ± 0.42 kgf, respectively) than NS (4.07 ± 0.36 and 2.98 ± 0.38 kgf, respectively). There were negative correlations between WBS and SL (r= −0.59 and r=−0.69, P< 0.05) at 1 and 10 postmortem, respectively. Furthermore, there were positive correlations for MFI and SL (r= 0.46 and r=0.48, P< 0.05) at days 1 and 10, respectively. These results point to a negative impact of sarcomere cold shortening in the sheep meat tenderization process in the hindlimb muscle.

Perception of color and its relationship to water holding capacity are important for defining the yield and quality of the pork production process. The aim of this study was to identify the relationship among color measurements taken at various anatomical positions in the cross-sectional surface of pork loin steak, and measurements of fluid exudation and its glucose concentration, as well as the impact on these attributes due to plasma glucose at slaughter. Two assays were conducted sequentially: i) investigation of the surface color parameters at different anatomical positions in the pork loin cross-section and their relationship to general exudation; and ii) the effect of plasma glucose levels on surface color variables, drip loss and glucose exudate concentration in three anatomical regions in the steak. The L* value of the ventro-lateral region, in the first assay, had the highest correlation with average steak drip loss at all anatomical points, exudation increasing proportionally between 48 and 72 h. The hue angle was also positively correlated with drip loss and lightness. The drip loss was greater when the animals had high plasma glucose, especially in the intermediate and lateral regions of the steak surface. The intermediate region presented greater lightness and lower redness. The plasma and glucose exudate concentrations, potential indicators of the muscle glycolytic metabolism, were related to color and drip loss. These variables can be influenced by the anatomical region inside the muscle, impacting the ability to retain water, two-toning occurrence and overall pork loin quality.