Effect of thermosonication on microorganisms, the antioxidant activity and the retinol level of human milk.

Abstract

In order to reduce the degradation of naturally-occurring components by conventional heat treatment, alternative processing techniques have been studied to preserve the nutritional properties of processed foods, such as thermosonication. This study evaluates the application of thermosonication for the inactivation of pathogenic microorganisms, and its effect on antioxidant activity and retinol level in donated human milk. We evaluate the effect of thermosonication on Staphylococcus aureus, Escherichia coli, and Salmonella spp. microorganisms in human milk by analyzing the effect of time and temperature of the thermosonication on these microorganisms using a central composite rotatable design. Also evaluated the effects of thermosonication (60 °C/4 min) on antioxidant activity using DPHH (2, 2-diphenyl-1-picrylhydrazyl) free radical and ABTS (2,2′-azino-bis 3- ethylbenzothiazoline-6-sulfonic acid) scavenging methods and on the retinol level in human milk and compared them to the effects of holder pasteurization (62.5 °C/30 min) in vitro. For this evaluation, a pool of the 10 human milk samples was made and distributed 40 mL, from this pool, for two interventions (holder pasteurization and thermosonication) and one control (untreated milk). Both in thermosonication and non-ultra-sound heat treatments, the microorganism counts tended to remain stable at lower temperatures, with the most significant and continuous reductions in thermosonication observed at the points of inflexion of the curves of the adjusted models: at 53.7 °C, 52.0 °C, and 60.9 °C for S. aureus, E. coli, and Salmonella, respectively. Thermosonication also promoted greater decimal reductions of the microorganisms analyzed than heat treatment at 60 °C, 48 °C, and 65 °C for S. aureus, E. coli, and Salmonella, respectively. Holder pasteurization significantly reduced the antioxidant activity when compared to the control, while thermosonication increased it. Retinol level remained stable following both pasteurization and thermosonication. This study could be used to encourage further studies to fill in the remaining gaps for this type of processing on human milk.