Cactus pear (Opuntia ficus-indica) fruit is a berry with a tasty pulp full of seeds that constitutes about 10-15% of the edible pulp. In Mexico, cactus pear is mainly consumed fresh, but also has the potential to be processed in other products such as juice. The objective of this study was to evaluate the effect of different ultrasound conditions at amplitude levels ranging (40% and 60% for 10, 15, 25 min; 80% for 3, 5, 8, 10, 15 and 25 min) on the characteristics of purple cactus pear juice. The evaluated parameters were related with the quality (stability, °Brix, pH), microbial growth, total phenolic compounds, ascorbic acid and antioxidant activity (ABTS, DPPH and % chelating activity) of purple cactus pear juices. The ultrasound treatment for time period of 15 and 25 min significantly reduced the microbial count in 15 and 25 min, without affecting the juice quality and its antioxidant properties. Juice treated at 80% of amplitude level showed an increased of antioxidant compounds. Our results demonstrated that sonication is a suitable technique for cactus pear processing. This technology allows the achievement of juice safety and quality standards without compromising the retention of antioxidant compounds.

The purpose of this research was to optimize the thermoultrasound conditions for blackberry juice using the response surface methodology and considering juice quality parameters and antioxidant capacity. With the exception of microbial growth, the response variables showed high correlation coefficients with the mathematical model (Radj>0.91). Thermoultrasound treatment inactivated all the evaluated microorganisms, and at the optimum conditions (50±1°C at 17±1min) it increased enzyme inactivation and antioxidant activity in comparison to pasteurized juice. The results demonstrated that thermoultrasound can be an alternative to pasteurization for the production of safe and high-quality juices with the added value of higher concentration of bioactive compounds and antioxidant capacity.

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Blackberry processing generates up to 20% of residues composed mainly of peel, seeds and pulp that are abundant in flavonoids. The objective of this study was to optimize the ultrasound conditions, in a closed system, for antioxidants extraction, using the response surface methodology. Blackberry (Rubus fructicosus) residues were analyzed for total phenolics, total anthocyanins, and antioxidant activity by ABTS and DPPH. The selected independent variables were ultrasound amplitude (X 1 : 80%-90%) and extraction time (X 2 : 10-15 min), and results were compared with conventional extraction methods. The optimal conditions for antioxidants extraction were 91% amplitude for 15 min. The results for total phenolic content and anthocyanins and antioxidant activity by ABTS and DPPH were of 1201.23 mg gallic acid equivalent (GAE)/100 g dry weight basis (dw); 379.12 mg/100 g¨dw; 6318.98 µmol Trolox equivalent (TE)/100 g¨dw and 9617.22 µmol TE/100 g¨dw, respectively. Compared to solvent extraction methods (water and ethanol), ultrasound achieved higher extraction of all compounds except for anthocyanins. The results obtained demonstrated that ultrasound is an alternative to improve extraction yield of antioxidants from fruit residues such as blackberry.

The objective of this study was to evaluate the effect of ultrasound (60 and 80% amplitude, 15 and 25 min) of blackberry juice on physicochemical (pH and total soluble solids), microbiological analysis (total plate count and Enterobacteria), and in vitro intestinal bioaccessibility of polyphenols and antioxidant activity (ABTS, DPPH). Ultrasound treatment caused a decrease of microbial count of blackberry juice and remained its physicochemical properties without change. The blackberry juice had a high antioxidant activity, however, after of the in vitro digestion process only 28% of total polyphenols were considered as intestinally bioaccessible, with the contribution of 30 to 60% of antioxidant activity in the bioaccesible fraction. The treatment at 80% amplitude for 15 min was the better treatment due it had an increase of bioaccessibility of polyphenols and antioxidant activity measured by ABTS. Our results showed that ultrasound treatment can preserve the blackberry juice without impairing to its antioxidant characteristics. Practical applications Blackberries are mostly consumed fresh but are also commercialized as individually quick frozen packs, bulk, frozen, seedless or seeded puree, freeze‐dried, juice, or concentrate. During fruit juices processing, thermal treatment and other conditions such as oxidation, light exposure, sugar addition, changes in pH, and temperature readily reduce the content of antioxidant compounds and its nutritional properties. Ultrasound is a non‐thermal processing technology with potential to replace the traditional thermal pasteurization, achieve microbial safety in fruit juices and remained its antioxidant properties of the blackberry juice.