Maria Helena Gomes

Phytochemicals preservation in strawberry as affected by pH modulation

Strawberries purées are incorporated in foods and subjected to pH modulation according to the expected final food matrix. The effect of pH on strawberry polyphenols stored at 4 and 23 °C for 90 days was evaluated. Total antioxidant activity and total phenolics content were only affected by time according to a first order model. The pH 4.5 induced higher decrease in (-)-epigallocatechin gallate (71% and 79%) and quercetin-3-glucoside (29% and 36%), for both storage temperatures. For pH 2.5 and 3.0, ellagic acid increased 84% for 4 °C and 185% for 23 °C. Anthocyanins concentration changes along storage were well described by first order model. The pH value of 2.5 presented the lower kinetic constant rate where cyanidin-3-glucoside, pelargonidin-3-glucoside and pelargonidin-3-rutinoside had a k=0.04, 0.05 and 0.03 day(-1). Lower storage temperature (4 °C) and lower pH (2.5) were the best condition for the preservation of polyphenols in pasteurized strawberry during a 90-day storage period.

Bioactive phytochemicals in apple cultivars from the Portuguese protected geographical indication “Maçã de Alcobaça:” Basis for market segmentation

ABSTRACT Phytochemical composition and antioxidant activity of eight apple (Malus domestica) cultivars (“Casa Nova,” “Fuji,” “Golden Delicious,” “Granny Smith,” “Jonagored,” “Reinette Grise,” “Royal Gala,” and “Starking”) from the “Maçã de Alcobaça” protected geographic indication, Portugal, were characterized to support market segmentation based on phytochemical content. Total phenolics, flavonoids, and anthocyanin contents, individual polyphenols and antioxidant activity were assessed in the flesh and skin of fruit at the ripe stage. A market segmentation of apple cultivars based on these bioactive phytochemicals is proposed. Fruit eaten with the peel can be segmented in three classes: (1) the flavonoid-rich “Starking,” “Reineta,” “Galaxy,” “Casa Nova,” Jonagored;” (2) the quercetin-rich “Fuji,” “Galaxy,” “Casa Nova;” and (3) flavonol and procyanidin-rich “Starking,” “Reinette,” “Jonagored,” “Casa Nova.” When apples were peeled before consumption, two phytochemical classes were proposed: (1) the flavonoid-rich “Reinette” and “Casa Nova,” and the (2) chlorogenic acid-rich “Reineta,” “Casa Nova,” and “Starking.”