Bacterial control and structural and physicochemical modification of bovine Longissimus dorsi by ultrasound

A multifactorial study to evaluate the effect of three ultrasound intensities (16, 28 and 90 Wcm^-2), two sonication times (20 and 40 min), and two storage times (0 and 7 days at 4 °C) on physicochemical properties, microbiological counts, and microstructure of bovine Longissimus dorsi was performed. The results showed that ultrasound (US) did not modify luminosity (P = 0.42), redness (a*, P = 0.45), or yellowness (b*, P = 0.94). However, the hue angle increased with US treatment and during storage (P = 0.04), showing an important degradation in the color of meat treated with 16 Wcm^-2. The pH and shear force decreased during storage at 4 °C (P = 0.01). Although US did not have any significant effects on the tenderness of the meat, the interfibrillar areas increased drastically in samples treated with 16, 28 and 90 Wcm^-2 (P < 0.0001). US was effective in controlling mesophilic and psychrophilic bacteria during storage at 4 °C when intensities of 90 Wcm^-2 were used (P < 0.0001), whereas decontamination of coliform bacteria was efficient independently of ultrasonication intensity, as long as a long sonication time (40 min) was used.