Biofunctionality, colorimetric coefficients and microbiological stability of blackberry (Rubus fructicosus var. Himalaya) juice under microwave/ultrasound processing

The bio-functionality of blackberry juice has acquired great relevance in the food industry, since it reduces the risk of chronicdegenerative diseases due to its high content of antioxidant compounds such as polyphenols/anthocyanins. However, conventional thermal processing decreases the content of these compounds. Hence, alternative technologies -as microwaves and ultrasoundare currently in research. The objective was to determine the e_ect of thermal and microwave/ultrasound processing on the physicochemical properties, polyphenols and anthocyanins, antioxidant capacity and microbiological stability of blackberry juice. Results showed that pH and °Brix increased in microwave/ultrasound processed juice (MUJ) compared to conventionally pasteurized juice (FPJ and SPJ) and raw juice (CJ). MUJ showed good microbiological stability after 30 days of storage at 4 °C as well as conventionally processed juices (FPJ and SPJ); nevertheless, in MUJ increased color parameters (L* (a* / b*), ∆E*, H*, C*), content of polyphenols and anthocyanins (2665.97 mg GAE L⁻¹ and 427.49 mg C3G L⁻¹ respectively), as well as antioxidant bioactivity DPPH and FRAP (11.63 and 14.06 mM TEAC L⁻¹ respectively) were significant compared to other juices. Therefore, the microwave/ultrasound process might be used in order to obtain a functional beverage with high antioxidant capacity, safe for human consumption and preserving color characteristics after one month of storage.