The effect of thermal and freeze drying on the content of organic acids and flavonoids in fruit of European cranberry (Oxycoccus palustris Pers.)
The present paper shows the results of a study on the effect of freeze and thermal drying on the content of organic acids and flavonoids in fruit of European cranberry (Oxycoccus palustris Pers.). They indicate a significant effect of drying conditions on the content of the above mentioned active compounds. In lyophilized fruit, distinctly more organic acids but less flavonoids were found than in fruit dried at a temperature of 35–400C. The largest relative differences were observed in the case of ascorbic acid. Its content in the fruit dried at high temperature, compared to the lyophilized material, was lower by a mean value of 5 mg/100 g of dry matter (DM), that is, by 42% on the average. With regard to the other organic acids (quinic, citric and malic acids), the average difference was 0.9–2.1 g/100 g DM (14–17%). The mean flavonoid content in the thermally dried fruit was larger by 34 mg/100 g DM (converted into hyperoside) and 24 mg/100 g (converted into quercetin), that is on average by 19% as compared to freeze-dried samples.