Vitamin C and lutein content of northern highbush blueberry (Vaccinium corymbosum L.) juice processed using freezing and thawing

Juices produced on an industrial scale are largely devoid of pectin substances, and lack a significant part of their vitamins, carotenoids and polyphenols. In recent years, physical methods have been used for preliminary treatments prior to pressing, allowing the elimination of enzymatic treatment. This paper presents the results of a study on the effect of freezing and thawing, as a preliminary treatment, on the efficiency of pressing and on the quality of juice obtained from northern highbush blueberry. Preliminary treatment of pulp, consisting in its freezing and thawing, caused a notable (23.1%), but lower than that for enzymatic treatment (34.9%), increase in pressing efficiency relative to control samples. The highest content of lutein and vitamin C was obtained in juice acquired from pulp subjected to treatment consisting in its freezing and thawing prior to pressing. The application of enzymatic treatment caused a 26.9% increase in the content of juice extract, while the treatment consisting in freezing and thawing caused a 19.5% increase in the content of extract. Irrespective of the type of preliminary treatment applied, a degradation of l-ascorbic acid and an increase in the content of dehydro-l-ascorbic acid were observed in the juices produced. The method proposed permits the production of juices with health-promoting properties, due to the application of freezing as a preliminary treatment.