New beverage based on grapes and purple-fleshed sweet potatoes: Use of non-standard tubers

Grapes and sweet potatoes are two different plant species that have distinct bioactive composition and the use of both in a non-alcoholic mixed beverage may be an interesting source of phytochemicals. Physicochemical and sensory characteristics, profile of phenolic compounds and biogenic amines of mixed juices of grapes ('BRS Violeta', 'BRS Cora' and 'Bordo') and purple-fleshed sweet potato ('JNRX12') (0, 10 and 30%) were determined. The beverage with sweet potato had high antioxidant activity attributed to the phytochemical compounds (e.g. anthocyanins, gallic acid, catechin, tryptophan, melatonin, serotonin and dopamine). Low levels of unwanted amines (histamine, tyramine, putrescine and cadaverine) were detected, showing that their consumption is safe. Purple-fleshed sweet potato had high levels of desirable amines, mainly melatonin, making the addition of sweet potato attractive for enriching beverages. The color, texture and sensory aspects were similar in whole grape juice and in mixed juices. Juices from 'BRS Violeta', with or without sweet potato showed high levels of bioactive compounds but were the least appreciated. The overall appearance and aroma of juices elaborated from 'BRS Cora' or 'Bordo' grapes had similar acceptance, regardless of the addition of sweet potato. Beverages from 'BRS Cora' and 30% purple-fleshed sweet potato are the most interesting mixture due to tryptophan and melatonin contents. Mixed juices of grapes and sweet potatoes (10% and 30%) are viable options for the use of tubers outside the commercial standard, as they add interesting bioactive compounds to beverages and please the consumer.