Parâmetros de processo e conteúdo de compostos fenólicos em amora-preta (Rubus spp.), da cultivar Tupy, submetida à desidratação osmótica.

Abstract

Several studies have shown correlation between phenolic compounds and antioxidant activity in blackberry (Rubus spp.).This fruit has a short postharvest life due to a fragile structure and high respiratory rate, there for ether elevance investigating processing techninques in order to extend its shelf-life. Cultivar Tupy, developed by Empresa Brasileira de Pesquisa Agropecuária, in Pelotas, RS, produces fruit with commercially desirable characteristics for the Brazilian market, such as low acidity and attractive size when compared to other cultivars such as Guarani or Brazos. In this context, the present work had the objective of evaluating the effects of imersion time and osmotic solution temperature on mass transfer e phenolic content in blackberry cv. Tupy, pre-treated by freezing or with sodium hydroxyl desolution. Waterloss was lower than 5 % in samples without pre-treatment kept in osmotic solutions at 30 °C, while samples p re-treated with sodium hydroxyl desolution was up to 21 % of waterloss at the same temperature. Sodium hydroxyl pre-treated samples kept at 45 °C osmotic solutions had water losses varying from 18 to 43 %, 2 to 3 times higher than the losses observed in untreated fruit. Samples in osmotic solutions at 60°C with sodium hydroxyl t reatment and without treatment yielded 31 to 46 % waterloss. Pre-frozen samples yielded from 35 to 49 % of waterloss. Underall studied conditions, phenolic content of dehydrated products was lower in pre-treated samples (frozen, or NaOH) than in non-treated. In addition, freezing promoted higher losses. Osmotic treatment resulted in changes in the phenolic contentof samples; catechin content increased while epicatechin and gallotannins decreased.