Physical characteristics and their relationship with surface-physical properties of Thai local beef during sous-vide processing

Abstract

In Thailand, local beef (Bos indicus) is preferred by most consumers since it is cheaper than imported beef; however, it has a tougher texture and requires a longer cooking time to make it palatable. The sous-vide cooking process has been found to improve food characteristics, especially the color and texture of meat. Therefore, sous-vide cooking was tested on Thai local beef using various cooking temperatures (60°C, 70°C or 80°C) for various cooking times (2–36 hr), after which the cooking loss, color and shear force of samples were measured. Cooked samples were also re-heated to simulate the preparation by the consumer and the re-heating loss was measured. Sous-vide cooking significantly (p<0.05) reduced cooking loss and lightness and resulted in higher yellowness and less redness compared to a raw sample. However, the lightness of the beef was not significantly (p>0.05) different at any of the cooking temperatures and times tested, whereas yellowness and redness depended on the cooking temperatures and times. Increasing the cooking temperature resulted in an increased shear force, while increasing the cooking time resulted in a significantly (p<0.05) decreased shear force. Cooking at higher temperatures for longer times significantly (p<0.05) increased the sous-vide cooking loss and decreased the re-heating loss. Image analysis of the surface texture showed that muscle fiber was at first clear and firm and then it shrank, with layering clearly visible during cooking. The coefficient of determination for the relationship between the fiber shrinkage area from images and the physical properties of color, cooking loss, re-heating loss and shear force were in the range 0.70–0.98 in all cases.