Influence of pHu on the physicochemical, biochemical and sensory parameters associated with meat quality of Bos indicus cattle

Author(s)

Iliani Patinho

• Document type: Doctoral Thesis
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2023-10-11

Examining board members

Carmen Josefina Contreras Castillo; Daniel Silva Antonelo; Luis Artur Loyola Chardulo

• Advisor: Carmen Josefina Contreras Castillo

Abstract

The global beef industry is geared towards meeting the demands of the consumer market, which is becoming increasingly informed and demanding in terms of meat quality. As a result, this thesis discusses the significance of the final muscle postmortem pH (pHu), widely used as a predictor of beef quality. The study was structured into three chapters. The first chapter aimed to uncover the unknown pathways behind protein changes and propose a robust list of biomarkers for the dark-cutting condition in beef. Results showed that the temporal proteomic profile identified 251 different proteins between high and normal pHu at 30 minutes (n = 33), 9 hours (n = 181), and 44 hours (n = 37) postmortem. Twenty-three proteins overlapped across postmortem times and could be suggested as candidate biomarkers for dark-cutting development. The second chapter investigated the decline in pH of Longissimus thoracis (LT) muscles at different sampling times: 0.5 h, 3 h, 6 h, 9 h, 24 h, and 44 h postmortem. Results indicated significant values for normal and intermediate pH ranges (P<0.01), showing reduction over postmortem time. Polyacrylamide gel electrophoretic analysis (SDS-PAGE) quantified molecular weights of proteins, and among six postmortem times, only three (0.5 h, 6 h, and 44 h) showed significant differences (P<0.05) between pH ranges. Moreover, high pHu exhibited the lowest shear force values in both experiment 1 (34.23N) and experiment 2 (37.48N). There seems to be an association between desmin and lower shear force values, positively contributing to beef tenderness. For HSP90, the normal and intermediate pH was associated with higher expression levels of HSP90. HSP27 showed postmortem time interaction with a higher relative intensity percentage at 9 h. The balance between Bax and Bcl-2 is not fully understood, but results suggest that cytochrome C release from the mitochondria might have been promoted by Bcl-2 at normal pH at 0.5 h and 9 h postmortem. Concerning caspase-3, caspases were observed to be activated immediately after animal exsanguination, showing higher expression levels in the early postmortem period, decreasing over time. Finally, the third chapter evaluated the physical and chemical properties, descriptive sensory profile, and acceptability of beef samples using two pHu groups: intermediate and normal. The study found that samples with intermediate pHu exhibited considerably higher juiciness (P<0.05) compared to normal pHu. Both beef samples were similarly assessed by CATA (Check-all-that-apply) analysis and deviated from the ideal beef profile. Additionally, results showed differences in relative deoxymyoglobin levels due to the ageing time, higher at 3 days than at 28 days and, more importantly, in samples with intermediate pHu (P<0.05). The color parameters L*, b*, chroma (C*), and oxymyoglobin were significantly influenced (P<0.05) by both pHu category and ageing time. These study results unveiled the primary findings regarding beef quality parameters and could be utilized by the industrial sector as strategies to mitigate the effects of pHu on beef production. (AU)

• FAPESP's process: 19/26026-2 - Influence of ultimate pH on the physicochemical and biochemists parameters associated tenderness of the meat of Bos indicus cattle
• Grantee: Iliani Patinho
• Support Opportunities: Scholarships in Brazil - Doctorate