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- Phytochemicals preservation in strawberry as affected by pH modulationPublication . Oliveira, Ana; Gomes, Maria Helena; Alexandre, Elisabete M. C.; Poças, Fátima; Almeida, Domingos P. F.; Pintado, ManuelaStrawberries purees 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 degrees 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 degrees C. and 185% for 23 degrees 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 degrees C) and lower pH (2.5) were the best condition for the preservation of polyphenols in pasteurized strawberry during a 90-day storage period.
- Changes in phenolic compounds during storage of pasteurized strawberryPublication . Oliveira, Ana; Almeida, Domingos P. F.; Pintado, ManuelaThis study aimed to establish mathematical models to describe changes in phenolics of pasteurized strawberry (Fragaria ×ananassa Duch.) during storage at 23 °C for 90 days. Freshly cut strawberries cubes were pasteurized for 5 min in a water bath at 90 °C following a heating time of 15 min. Antioxidant activity, total phenolics, total anthocyanins, and individual phenolic compounds were assessed immediately before or after pasteurization and at regular time intervals during storage. The results indicated that (1) pasteurization did not affect (P <0.05) the concentrations of total phenolics or total anthocyanins, but significantly reduced the concentrations of quercetin-3-rutinoside, kaempferol, and cyanidin-3- glucoside, and increased the concentrations of (+)-catechin, (−)-epicatechin, epigallocatechin gallate, quercetin-3- galactoside, and ellagic acid; (2) changes in antioxidant capacity, total anthocyanin, and individual compounds during storage were described by a pseudo-first-order model with the exception of total phenolic and specifically kaempferol and ellagic acid which followed zero-order kinetic models. Pelargonidin-3- glucoside degraded at the highest rate (k =0.07 day−1), followed by ellagic acid (k =0.004 day−1) and kaempferol (k = 0.003 day−1). The rate constants can be used to predict phytochemical changes in strawberry products during storage.
- Effect of modified atmosphere on polyphenols during storage of pasteurised strawberry puréesPublication . Oliveira, Ana; Alexandre, Elisabete M. C.; Coelho, Marta; Gomes, Maria Helena; Almeida, Domingos P. F.; Pintado, ManuelaThe minimum loss of processed fruit nutritional quality must been guaranteed during storage and the atmosphere can be a limiting step. Strawberry purees flushed with gas mixtures: 10 kPa O-2 + 90 kPa N-2, 100 kPa N-2 and air (78 kPa N-2 + 21 kPa O-2 + 0.03 kPa CO2) were stored for 90 days at 4 and 23 degrees C and revealed no effect in total antioxidant activity and in total phenolic content. The compounds (+)-catechin, (-)-epicatechin and quercetin-3-rutinoside were not affected by the atmospheres for both temperatures and ellagic acid was the exception within strawberry phytochemicals, where its concentration was higher for samples stored in air. Total anthocyanin content was better preserved when strawberry pur e was stored in 100 kPa N-2 at 4 and 23 degrees C, at which temperatures their levels decreased 24 and 77%, respectively. At 4 degrees C cyanidin-3-glucoside presented no significant differences between atmospheres. Pelargonidin-3-glucoside and pelargonidin-3-rutinoside decreased both 27% for 100 kPa N-2 and 45% for 10 kPa O-2 and air. All the individual anthocyanins were not affected by the atmospheres when stored at 23 degrees C. (C) 2014 Elsevier Ltd. All rights reserved.