Effect of ultrasonic, thermal and enzymatic treatment of mash on yield and content of bioactive compounds in strawberry juice

Strawberries are rich in bioactive compounds that may be of health importance. The technological process often significantly reduces the content of such compounds in the product. The study aimed to compare the effect of enzymatic, ultrasonic and thermal mash treatment on the content of ascorbic acid, anthocyanins, phenolic compounds and the antioxidant activity of strawberry juice. In addition, the effect of increased temperature assisting ultrasonic mash treatment and the use of a vacuum for a short period to remove air from the mash during pectinolysis was investigated. A significant increase in the efficiency of juice pressing was obtained for enzymatic treatment (by 40%), thermal and thermosonication (16%). It was found that the applied methods yield different results depending on the tested compounds. In the case of anthocyanin, the most effective method was thermosonication, which contributed to a 40% increase in their content. The enzymatic and thermal methods resulted in a two-fold increase in the content of phenolic compounds. The antioxidant activity of the juice from the treated mash (regardless of the method used) was significantly higher than samples from the untreated mash. A significant correlation (r = 0.77) was noted between antioxidant capacity and non-anthocyanin phenolic compound content in the tested juices.