2016 年 22 巻 5 号 p. 647-654
Maoberry (Antidesma bunius L.) juice is popularly consumed as a pasteurized juice because of its high levels of antioxidants. Although pasteurization is normally applied to extend the shelf life of fruit juices, this method damages the desired characteristics and antioxidant constituents of fruit juice products. Ultra-sonication is an alternative process to treat fruit juices without impairing their health benefits and consumer acceptance. This study is the first report on ultra-sonication effects on the physicochemical properties, bioactive components, antioxidant activities, and sensorial characteristics of maoberry juice. After ultra-sonication processing at a frequency of 20 kHz and amplitude levels between 20% and 80% for 30 min and when compared with fresh and heated (75°C, 30 min) juices, we found that the physicochemical properties viz. total soluble solids, pH, and viscosity of processed juices did not change. However, a noticeable effect on the color parameters of ultra-sonicated juices shown by decreased lightness and increased redness values was found. The highest chroma value (C*) and total different colors (ΔE) were observed in the heated one. Microbial count levels, polyphenol oxidase and peroxidase activities were low in all treatments, in particular thermally and 80% amplitude treated batches. Total anthocyanins and phenolic compounds increased in the ultra-sonicated maoberry juices treated at 60% and 80% amplitudes. The contents of ascorbic acid in maoberry juice decreased significantly at 80% amplitude and at 75°C. The antioxidant activities (DPPH and FRAP assays) of ultra-sonicated products still retained high levels with no significant difference from the fresh sample. The sensorial attributes of ultra-sonicated juice showed no difference from the control (fresh juice), but higher than the heated sample. In general, ultra-sonication technology could be an appropriate processing technique to maintain the desired quality attribute characteristics of maoberry juice.
