The most important quality criteria of some homegrown black-currant varieties II. Dry matter, pectin, acid content, colour and formol value

Authors

• Taina Kuusi The State Institute for Technical Research, Laboratory for Food Research and Technology, Otaniemi

DOI: https://doi.org/10.23986/afsci.71646

Abstract

The quality properties of black-currant have been investigated in respect of 12 home-grown varieties. Samples were obtained from 6 localities over a period of 3 years. The properties studied were dry matter, pectin and its degree of esterification, acid content, colour strength, and formol value. As regards dry matter, the differences between the varieties were small. A high summer temperature diminished the dry matter values. Some variations existed between the varieties in respect of pectin. Thus Wellington XXX and X contained an abundant amount of pectin, whereas Brödtorp and Black of Lepaa contained little. A high summer temperature lowered the pectin content, but the degree of its esterification remained high. A corresponding effect was noted as a consequence of the degree of north latitude of the place of growth: the amount of pectin was increased and its degree of esterification was lowered towards the north. With respect to the acid content, differences were remarked among the varieties, corresponding approximately to results reported earlier in literature. As a rule, the acid content of the home-grown varieties is higher than the values so reported. Of weather factors, sunshine seems to exercise most influence on the acid content, the acid being increased by a lack of it. Similarly, differences among the varieties were found in colour strength. This property seems to bear a negative correlation to the berry size, since the colouring compounds are localized in the skin part of the berry. The colour strength depends markedly upon the summer temperature, as is evidenced by both the comparison of the different years, and that of the different localities. Slight differences in the formed value were noted between the varieties. However, this value depends substantially upon the degree of maturity; it falls during ripening, a fact which renders comparison difficult.