RESUMEN
Beneficial health effects are attributed to the wide array of polyphenols such as anthocyanins present in berries. Blackberries have been improved genetically to be cultivated in different climate such as Brazil. Thus, distinctive cultivars were created. However, antioxidant properties of these have not been evaluated. This study aimed to investigate the availability of phenolic compounds in Brazilian cultivar blackberries (cv. Xavante) after processing into purées, coulis and jam changes during storage. Physicochemical, total phenolic compounds (TPC), anthocyanins and antioxidant activity of frozen and processed food products were evaluated. The pH values of jam and frozen pulp increased to a greater extent during storage. Pureé A (70 °C for 20 min) showed the highest value for lightness and redness on day 1 with a decrease after 30 days of storage. Redness values decreased to a greater extent for purée A, indicating less stable product over time whereas coulis presented optimal stability shown by the smaller color difference value. No differences in TPC were observed for frozen pulp, purée A, purée B, and coulis. Significantly lower amount of TPC was present in the jam indicating degradation of phenolic compounds upon heating and concentration process involved in jam making. An increase in antioxidant activity (ABTS assay) was observed in processed products after storage, which might be related to the development of new compounds with greater antioxidant activity. Therefore, processing of blackberries into food products is an alternative to prolong the accessibility of those fruits without extensive loss of antioxidant activities.
RESUMEN
Grape extracts can be added to milk to produce cheese with a high concentration of polyphenols. Four commercial extracts from whole grape, grape seed, and grape skin (2 extracts) were characterized and added to milk at concentrations of 0, 0.1, 0.2, and 0.3% (wt/vol). The effect of grape extracts on the kinetics of milk clotting, milk gel texture, and syneresis were determined, and model cheeses were produced. Whole grape and grape seed extracts contained a similar concentration of polyphenolic compounds and about twice the amount found in grape skin extracts. Radical scavenging activity was directly proportional to the phenolic compounds content. When added to milk, grape extracts increased rennet-induced clotting time and decreased the clotting rate. Although differences were observed between the extracts, the concentration added to milk was the main factor influencing clotting properties. With increasing concentrations of grape extracts, milk gels showed increased brittleness and reduced firmness. In addition, syneresis of milk gels decreased with increasing concentrations of grape extracts, which resulted in cheeses with a higher moisture content. The presence of grape extracts in milk slightly increased protein recovery in cheese but had no effect on fat recovery. With whole grape or grape seed extracts added to milk at 0.1% (wt/vol), the recovery coefficient for polyphenols was about 0.63, and decreased with increasing extract concentration in milk. Better polyphenol recovery was observed for grape seed extracts (0.87), with no concentration effect. Commercial extracts from whole grape, grape seed, or grape skin can be added to milk in the 0.1 to 0.3% (wt/vol) concentration range to produce cheese with potential health benefits, without a negative effect on cheese yield.