Anthocyanin stability was assessed over temperatures ranging from 30 to 90 degrees C for seven products: blood orange juice [Citrus sinensis (L.) Osbeck]; two tropical highland blackberry juices (Rubus adenotrichus Schlech.), one with high content and the other with low content of suspended insoluble solids (SIS); and four roselle extracts (Hibiscus sabdariffa L.). The blackberry juice showed the highest content of anthocyanins with 1.2 g/L (two times less in the roselle extracts and 12 times less in the blood orange juice). The rate constant for anthocyanin degradation and isothermal kinetic parameters were calculated according to three models: Arrhenius, Eyring, and Ball. Anthocyanins in blood orange juice presented the highest rate constant for degradation, followed by the blackberry juices and roselle extracts. Values of activation energies were 66 and 37 kJ/mol, respectively, for blood orange and blackberry and 47-61 kJ/mol for roselle extracts. For the blackberry juices, a high SIS content provided only slight protection for the anthocyanins. The increasing content of dissolved oxygen, from 0.5 to 8.5 g/L, did not significantly increase the rate constant. For both isothermal and nonisothermal treatments, all three models accurately predicted anthocyanin losses from different food matrices.

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This study evaluated the effects of mechanical and enzymatic pretreatments on the extraction of anthocyanins and ellagitannins from blackberries. Continuous pressing yielded significantly higher turbidity values and content of anthocyanins and ellagitannins (P < 0.05) compared with discontinuous pressing. The use of enzymatic pretreatment also significantly increased the extraction of polyphenolic compounds (P < 0.05), in particular that of total ellagitannins, on average from 437 to 982 mg ellagic acid equivalents/100 g (dry basis) when using discontinuous pressing. When microfiltration was used, the content of ellagitannins and anthocyanins was found to be similar in both feed and permeate when discontinuous press was used to extract the juice, but a significant decrease of 34% (dry basis) was found in the concentration of ellagitannins when continuous pressing was used (P < 0.05). These results should be useful for future efforts to increase the extraction of polyphenolic compounds from fruits and vegetables.

Response surface methodology (Box‐Behnken design) was applied to assess and model effects of 3 factors, sweetener, low methoxyl pectin, and calcium content (each at 3 levels), on the overall acceptability of a blackberry (Rubus irasuensis Liebm.) jelly, as determined by 100 consumers. Jelly was produced using clarified juice, obtained from a cross‐flow microfiltration process. Results showed that the model fit was significant, and there was satisfactory correlation between actual and fitted values (R 2= 0.925 and adjusted R 2= 0.791). The model presented no significant lack of fit (P= 0.096). Sweetener level had a significant effect on overall acceptability (P≤ 0.05), but low methoxyl pectin and calcium levels did not. The statistical model was further used to optimize the factor levels for highest acceptability, in order to obtain a jelly that provided less than 8 calories per serving, making it possible to label the product as “low calorie.” The product is a good alternative for consumers who wish to diminish sucrose intake.