A study of some important vitamins and antioxidants in a blackcurrant jam with low sugar content and without additives

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 degrees, 76 degrees, 92 degrees and 97 degrees C. Processing time varied between 1-20 min. After processing, the highest content of ascorbic acid was found in the jam processed at 97 degrees 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 degrees C was stored in a shelf-life study for 13 months. The jam was then stored at 8 degrees C, ambient temperature and at 37 degrees C. At ambient temperature the jam was stored both in dark and in daylight, at 8 degrees C and at 37 degrees C the jam was stored in dark. After 13 months of storage, at 8 degrees 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 beta-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.