Abstract

Hydrosoluble soy extract (HSE) is nutritious and highly perishable, requiring it to be submitted to an adequate conservation method. Ultrasound combined with heat (thermosonication) can be an alternative capable of reducing the undesirable effects caused by the conventional thermal treatment in this product. The objective of this work was to evaluate the effect of thermosonication on the inactivation of the enzyme lipoxygenase (LOX) in HSE under 2 ultrasonic amplitude conditions (70 and 90%). Fresh and treated HSE samples were characterized in terms of color parameters, pH, soluble solids and total phenolic content. Temperature was the most important factor in reducing LOX residual activity (RA). Highest LOX inactivation condition (RA = 2.14%) occurred in the range of 90% ultrasonic amplitude at 83ºC for 3 min. In this condition, the specific acoustic energy (SAE) in thermosonicated sample was 596.7 mW/mL. Thermosonication has the potential to minimize the phenolic loses (Total Phenolic Content = 35.25 ± 0.25 mg/100 mL), when compared to heat treatment (Total Phenolic Content = 13.48 ± 0.06 mg/100 mL). Thermosonication has an interesting potential in maintaining the nutritional value of the HSE.

Key words: Hydrosoluble soy extract, enzyme inactivation, lipoxygenase, thermosonication, ultrasound.