C. Z. Alvarado1and A. R. Sams2
1Texas Tech University, Animal and Food Sciences, Lubbock, TX, USA
2Texas A&M University, Poultry Science, College Station, TX, USA
To evaluate the relationship of slow chilling to pale, soft, and exudative (PSE) meat, 48 male turkeys were processed and chilled at 0, 10, 20, or 30°C for either 45 or 90 minutes prior to deboning.
Temperature, pH, color, gel strength, cook loss, expressible moisture, and precipitated phosphorylase were determined on the fillets. Through 105 minutes post mortem (PM), the four temperature treatments produced significantly different breast muscle chilling rates. The 30°C - treated carcasses had a more rapid muscle pH decline, lower ultimate pH, paler color, higher drip and cooking losses, and weaker gel strength than fillets from the carcasses treated at 0°C for shorter periods. Phosphorylase precipitation also increased in samples treated with a slower chilling rate.
Achieving a breast muscle temperature of less than 36°C by 60 minutes PM and 28°C by 90 minytes PM may reduce the PSE-like characteristics.
Introduction
Postmortem factors such as chilling regimes can influence the development of PSE meat (Honikel and Fischer, 1977; Offer, 1991). Studies in turkeys have indicated that postmortem temperatures of 30 to 37°C accelerated postmortem metabolism (Khan and Frey, 1971). McKee and Sams (1998) also found that holding carcasses at elevated temperatures of 40°C accelerated postmortem glycolysis and resulted in pale meat with increased drip loss and cook loss when compared to carcasses chilled at 0°C. Alvarado and Sams (2002) found that color, water holding capacity, texture, and product integrity are negatively affected in slow chilled turkey carcasses. The objectives of this research were to evaluate the relationships between muscle chilling rates, protein denaturation, and the development of PSE meat.
Material and Methods
A total of 48 turkey toms (22.5 wks) were processed in each of two trials. Feed was withdrawn 12 hours prior to processing, but the birds had access to water until 2 hr prior to conventional processing. Following evisceration, the carcasses were immersion chilled in 0, 10, 20, or 30 for either 45 (60 minutes PM) or 90 min (105 minutes PM) prior to deboning.
Temperature, pH, L* value, gel strength, cook loss, and phosphorylase were determined. The data was subjected to ANOVA and means were separated using Duncan's multiple range test with a significance level of P< 0.05.
Results and discussion
Through 105 minutes PM, the four temperature treatments produced significantly different breast muscle chilling rates with the higher chilling temperatures resulting in higher breast muscle temperatures. In birds exhibiting PSE meat, there was a rapid pH decline early PM. The carcasses chilled for 45 min at 20 and 30°C and those chilled for 90 min at 30°C had significantly lower pH than those chilled at 0°C (Tables 1, 2). Carcasses with a breast muscle temperature of approximately 36°C or higher (45 minutes chilled) or approximately 28°C or higher (90 minutes chilled) reached an ultimate pH earlier PM, indicating a faster rate of rigor development as compared to more rapidly chilled carcasses (Figure 1, 2).
At 60 minutes post mortem, the carcasses chilled at 30°C had significantly higher L* values indicating lighter fillets than the carcasses chilled at 0°C (Table 1). At 105 minutes PM, carcasses chilled at 10, 20, and 30°C had significantly higher L* values than those chilled at 0°C (Table 2). The effect of carcass temperatures on L* value indicate that at 60 minutes PM, there was an increase in L* value between 35 and 36 C (Figure 3). At 105 min PM, there was a significant increase in L* values of fillets having a muscle temperature of 28°C or higher indicating lighter fillets (Figure 4). Carcasses chilled in 30°C for 60 minutes had increased cook loss, decreased gel strength, lower ultimate pH, and a higher amount of precipitated phosphorylase compared to the other treatments (Table 1).
Since low pH and high carcass temperatures early PM can lead to increased protein precipitation, a decrease in protein solubility will decrease the strength of heat induced gels which can cause sliceability problems in cooked whole muscle products. When chilled for 90 minutes, the lowest ultimate pH along with an increase in precipitated phosphorylase was achieved in carcasses chilled at 30°C (Table 2). Also, L* value was significantly lower in carcasses chilled at 0°C for 90 minutes compared to the remaining groups and cook loss and gel strength were also decreased. Therefore, the results of this study indicate that there is a relationship between chilling time and temperature with 30°C chilling temperatures for 45 and 90 minutes resulting in pale, soft, and exudative meat. Therefore, processors should chill turkey carcasses rapidly early postmortem to prevent poor meat quality problems. Achieving a breast muscle temperature of less than 36°C by 60 minutes PM and 28°C by 90 minutes post mortem may reduce the PSE-like characteristics.
References
Alvarado, C. Z. and A. R. Sams. 2002. The role of carcass chilling rate in the development of pale, exudative turkey pectoralis. Poult. Sci. 81:1365-1370.
Honikel, K. O. and C. Fischer. 1977. A rapid method for detection of PSA and DFD porcine muscles. J. Food Sci. 42:1633-1636.
Khan, A. W. and A. R. Frey. 1971. A simple method for following rigor mortis development in beef and poultry. Can. Inst. Food Technol. 4:139-142.
Lee, Y. B., G. L. Hargus, J. E. Webb, D. A. Rickansrud, and E. C. Hagberg. 1979. Effect of electrical stunning on post mortem biochemical changes and tenderness in broiler breast muscle. J. Food Sci. 44:1121-1128.
McKee, S. R. and A. R. Sams. 1998. Rigor mortis development at elevated temperatures induces pale exudative turkey meat characteristics. Poult. Sci. 77:169-174.
Offer, G. 1991. Modeling of the formation of pale, soft, and exudative meat: effects of chilling regime and rate and extent of glycolysis. Meat Sci. 30:157-184.
From Proceedings of the "XVI European Symposium on the Quality of Poultry Meat" and the "X European Symposium on the Quality of Eggs and Egg Products", Saint-Brieuc Ploufragan, France.
