Seasonal changes in sugar contents of cabbages

Abstract

Cabbages are consumed mostly as salads in Japan. The sweetness is considered to be one of their most important factors for the quality. In the preliminary investigation, it was observed that their sweetness was varying with the growing seasons, as well as with the varieties and the places of production. To ascertain the seasonal changes in sweetness, and to find the relation between sweetness and sugar contents, the following studies were carried out.1. Cabbages of representative varieties in each season were obtained from Tokyo Central Wholesale Market, from June 1964 to May 1965.Contents of total and reducing sugars in the analyzed samples decreased from June to September, then increased gradually till March, and decreased again until May. But, some cabbages, which were harvested in midwinter, showed low levels in sugar content.The contents of non-reducing sugars were low during warm season, and were high during cold season. The ratio of reducing sugars/total sugars was over 0.9 in the former, and lower than 0.5 in the latter.2. On the field of Tokyo University, several cabbage varieties were planted four times from March to October 1966, and were harvested throughout one year since June 1966. The sugar contents of harvested cabbages varied with growing seasons. Their levels were low in warm season, and high in cold season, the same as in the case of above mentioned study. Low sugar contents were found in some wintered-over cabbages, too.3. Close relationships were existed between sugar contents in cabbages, and degrees of sweetness evaluated by organoleptic tests. The levels of sweetness were in proportion to the sugar contents as a rule, but, there were some exceptions. When the cabbages were suffered from cold injury on the field before harvested time, their taste became rather sweet notwithstanding low sugar levels. Further, if the leaves of cabbages were thick and firm, or containning bitterness, their taste was felt undesirable in spite of their high sugar levels.