Comparison of different methods for determining the extent of myofibrillar fragmentation of chilled and frozen/thawed beef across postmortem aging periods.

To evaluate different methods for the determination of postmortem myofibrillar fragmentation, three protocols were compared: fragmentation index method (FI) after drying the filtrate residue at room temperature for 10 min (FIroom) or at 105 °C for 12 h (FIoven); and myofibrillar fragmentation index (MFI) by the absorbance method. Beef Longissimus thoracis steaks (n = 34) were randomized into two treatments (frozen/thawed and unfrozen) and aged for 0, 7, 14 or 21 days. An interaction (P < 0.05) between method and treatment, method and aging and treatment and aging was found. FIroom was the best to detect a difference in fragmentation at all aging days. In addition, FIroom and FIoven both detected the tenderization process that occurs by freezing while the MFI method did not, yet all three methods were similarly related to tenderness as measured by shear force. It is suggested that FIroom is the most effective method (time, cost) to indicate myofibrillar fragmentation, under the conditions imposed herein.

Using microwave cooking to evaluate tenderness and its relationship to sensory analysis.

This study evaluated a microwave (Mw) cooking method for determining beef toughness using the Warner-Bratzler slice shear force (WBsSF) protocol. Longissimus thoracis muscles were aged for 1, 10, 19, and 28 days at 4C. They were then either cooked on a clam-shell grill until reaching an internal temperature of 72C, in a Mw for 100 s at maximum power (Mw100) or for 140 s at 60% of maximum power (Mw60). Cooking loss and shear force (SF) values were higher in Mw samples than in grilled ones. SF assessment by grill and Mw100 were able to discriminate tenderness by aging times in the same way as the sensory panel. The SF measured in a grilled sample had higher repeatability (R = .74) and correlation with sensory scores (r = -.79) than Mw100 (R = .61; r = -.62) and Mw60 (R = .51; r = -.53). Mw100 can be considered as an appropriate alternative for the WBsSF protocol. PRACTICAL APPLICATIONS: Tenderness is the most important attribute for consumers. Many studies have evaluated tenderness in meat and different protocols for cooking. This work was intended to optimize and evaluate the use of the microwave as a cooking method for shear force determination, against a standard protocol and establish the correlation to sensory tenderness.

Microwave as a rapid cooking method for beef tenderness evaluation.

Semitendinosus (ST) muscle steaks were grouped according to three locations (proximal, middle, and distal end), grilled to endpoint temperature of 71C or cooked for 20, 30, 40, 50, or 60 s in a microwave oven (Mw). The location did not affect (p > .05) the cooking loss (CL) or shear force (SF) values. The CL increased (p < .05) with longer microwave cooking times, but only the Mw40 samples did not differ (p > .05) from the grill samples. None of the microwaves' SF values were different (p > .05) from the grill values, with treatments Mw30 to Mw50 showing moderate repeatability (R = 0.51-0.60) and Mw30 and Mw60 showing higher correlations (r > .71) with grill values. Cooking beef strips with a microwave is a potential method for tenderness evaluation, but requires additional study to evaluate and optimize this application in different muscles and for comparison to sensorial data. PRACTICAL APPLICATIONS: The work was intended to evaluate the possibility of using a microwave oven for cooking meat to be used in objective measurement protocols for meat tenderness and to optimize the conditions for this purpose. The use of a standardized microwave procedure allows a dramatic reduction in analysis time and may reduce error variance due to nonuniform cooking procedures.

Comparison of Warner-Bratzler shear force values between round and square cross-section cores for assessment of beef Longissimus tenderness.

The objective of this experiment was to determine whether there is a difference between Warner-Blatzler shear force values of round (WBSF) and square (WBsSF) cross-section cores for assessment of beef tenderness. To compare the effect of core sampling, Longissimus thoracis muscles were obtained from 43 beef carcasses at 1, 14, and 28days postmortem. For each sample, tenderness was assessed by a trained sensory panel and by WBSF and WBsSF techniques. There was a strong and linear relationship (R2=0.77) between WBSF and WBsSF, but the average shear force of square cores were (P<0.05) greater than those of round cores. The WBsSF had greater repeatability (R=0.85 vs 0.81) and explained slightly more of the variation in sensory panel perception of beef tenderness (76% vs 74%) than WBSF. The results indicate that WBsSF seems to be a more precise method of measuring shear force, being little more sensitive for detecting tenderness differences than WBSF.

Freezing, thawing and aging effects on beef tenderness from Bos indicus and Bos taurus cattle.

The objective of this study was to determine the effects of freezing prior to aging on the meat tenderness of young Nellore and Aberdeen Angus bulls. Samples of the longissimus thoracis muscle were submitted to two treatments: conventional aging and freezing (-20°C for 40 days) followed by thawing and aging periods. The meats were evaluated after 0, 7, 14 and 21 aging days (1°C). Freezing increased (P<0.05) purge, cooking loss and total exudate loss throughout aging. Nellore meats had greater total exudate loss and shorter sarcomere lengths (P<0.05). Freezing increased proteolysis during aging in the meats of both breeds, but reduced shear force was found (P<0.05) only in Aberdeen Angus meats and only at time zero. These results suggest that the meat tenderizing process by freezing prior to aging may contribute to meat tenderness in the first weeks of aging, but it is dependent on the animal breed.

Comparison of Warner-Bratzler shear force values between round and square cross-section cores from cooked beef and pork Longissimus muscle.

This study was conducted to investigate the effect of core sampling on Warner-Bratzler shear force evaluations of beef and pork loins (Longissimus thoracis et lumborum muscles) and to determine the relationship between them. Steaks of 2.54 cm from beef and pork loins were cooked and five round cross-section cores and five square cross-section cores of each steak were taken for shear force evaluation. Core sampling influenced both beef and pork shear force values with higher (P<0.05) average values and standard deviations for square cross-section cores. There was a strong and linear relationship (P<0.01) between round and square cross-section cores for beef (R(2)=0.78), pork (R(2)=0.70) and for beef+pork (R(2)=0.82) samples. These results indicate that it is feasible to use square cross-section cores in Warner-Bratzler shear force protocol as an alternative and potential method to standardize sampling for shear force measurements.