MICROWAVE POTENTIAL FOR BLACKBERRY JELLY PROCESSING: EFFECT ON NUTRITIONAL AND SENSORY QUALITY

The purpose of this study was to evaluate the effect of microwave and microwave combined with vacuum on the nutritional and sensory characteristics of blackberry jelly, in order to verify if they are actually more viable methods of processing when compared to the traditional process in open pan. Blackberry jelly was processed in a conventional way (open pan) and in different microwave conditions, varying potency and presence/absence of vaccum. Following, the samples were evaluated regarding total phenolics, anthocyanin, ascorbic acid, antioxidant activity and sensory acceptance. It was verified that the processing methods studied did not influence the sensory characteristics of the obtained jelly, however, it was observed that the microwave processing, in particular low power microwave without vacuum, promotes smaller nutritional losses in the blackberry jelly. The jellies processed in low-power microwave without vacuum stood out from the others presenting the highest antioxidant activity by DPPH (2095.19 g f.w./g of DPPH) and ABTS method (21.81 μM trolox/g), the highest total phenolic content (504.58 mg GAE/100 g) and one of the highest ascorbic acid content (33.72 mg ascorbic acid/100 g). The jelly processed in high-power microwave without vacuum, stood out to have the highest antioxidant activity by the beta-carotene method (84.20% protection). In relation to the anthocyanins content, the jellies processed by vacuum microwave (low and high power) were highlighted because they presented the highest levels (16.25 and 15.03 mg of cyanidin equivalent 3 glucoside/100g, respectively). In summary, it was observed that microwave minimizes nutritional degradation and reduces the jelly processing time. This work serves as a preliminary study to microwave technique possibly be used and implemented by the food industries, producing higher quality products that meet consumer demand.