Effect of ultrasound treatment on physical and textural properties of refrigerated and freeze thawed beef

The aim of this research was to investigate the effect of ultrasound (US) treatment on physicochemical and textural characteristics of beef. US treatment was applied at two frequencies of 60 and 40 KHz for two times of 15 and 30 minutes. After that the meat pieces were held for 8 days at refrigerator temperature and their physical and chemical properties were evaluated during 1, 4 and 8 time intervals. US treatment caused to decrease pH and water holding capacity. Cooking loss was increased and storage loss (at 4 °C) and freeze thawing loss were decreased after US treatment and the sample treated by 40 KHz for 30 min exhibited the highest change in this parameters. The US treatment had no significant effect on water holding capacity of beef (p>0.05). The effect of US treatment on hardness of meat was dependent on applied frequency, time of treatment and storage time. The sample treated at 40 KHz for 15 min at day of 4 had the lowest hardness. Microscopy images indicated that the structure of myofibrils is changed and the space between muscle fibers increased after US treatment and by decreasing of frequency and increasing of US time, the change of myofibrils was increased. By considering all parameters, using of 40 KHz for 30 min had the best effect on quality attributes of beef and thus it is able to be used as an effective treatment after slaughter.