A Study of Some Important Vitamins and Antioxidants in a Blackcurrant Jam with Low Sugar Content and Without Additives

Abstract

Blackcurrant (Ribes nigrum) jam was manufactured with the aim of producing a jam with a low sugar content, and without any additives. Four temperatures were investigated, namely 60°, 76°, 92° anad 97°C. Processing time varied between 1-20 min. After processing, the highest content of ascorbic acid was found in the jam processed at 97°C for 1 min, which contained 63.3 ± 2.6 mg ascorbic acid/100 g jam. At all combinations investigated more than 60% of the original amount of ascorbic acid was retained after manufacturing and packaging. The jam made at 92°C was stored in a shelf-life study for 13 months. The jam was then stored at 8°C, ambient temperature and at 37°C. At ambient temperature the jam was stored both in dark and in daylight, at 8°C and at 37°C the jam was stored in dark. After 13 months of storage, at 8°C, 60% of the amount of ascorbic acid and 29% of the amount of anthocyanins were retained. In the jam stored at higher temperatures less of both was retained. The ß-carotene in the jam was found to be stable throughout the whole shelf-life study. Exposure to light did not have any effect on any of the components studied. The degradation of anthocyanins was best described by a second-order reaction and the activation energy was determined to be 90 kJ/mol. A jam of blackcurrant may be considered as a good source of vitamins and antioxidants after one year, if certain precautions concerning manufacture and storage conditions are taken.