Recently, the demand for commercial Hokkaido rice has been on the rise. Consumers are calling for the development of Hokkaido rice cultivars that are suitable for commercial use, in addition to the popular household varieties. In response, we have been developing new Hokkaido rice cultivars as well as evaluation methods to determine the suitability of these cultivars for commercial use.
1．Definition of suitability for commercial use
From 2009 to 2013, we visited 13 major commercial users of Hokkaido rice and conducted interviews to gain an understanding of the qualities considered essential in commercial rice. All the surveyed companies listed the following four processes in rice production: 1) commercial milling, 2) commercial cooking, 3) rice processing and molding, and 4) storage and distribution prior to consumption. The data demonstrated that in each process, the suitability of rice was evaluated based not only on taste and quality, but also on the unique commercial perspectives of economic efficiency and workability.
2．Development of a method to evaluate the suitability of Hokkaido rice for commercial use
Based on the results of the above survey, we identified the appropriate parameters to evaluate the suitability of commercial rice, as specified by actual consumers. We undertook the development of new evaluation methods that take into consideration economic efficiency (cooking yield) and workability (stickiness), aspects not previously considered. Addition of the parameters from the new evaluation method to the existing parameters of taste and quality is anticipated to make the assessment comprehensive and address the requirements of various commercial users, which include determining the amount of water to be added to achieve low stickiness (workability) and high cooking yield (economic efficiency). The ultimate goal is to select cultivars with reduced stickiness (workability), culminating in the selection of cultivars that have only moderate stickiness and little discoloration (taste and quality).
Grapes (Vitis spp) are a major fruit crop worldwide and are consumed as table grapes, wine, and raisins. Currently, the leading grape cultivars in the world are European (Vitis vinifera L.), and account for the majority of the worldwide production. European grapes, however, are highly susceptible to fungal diseases and to berry cracking when grown in wet climates. In eastern United States, breeders have attempted to improve the native American species through hybridization between European grapes and native species such as V. labrusca L. The interspecific hybrid cultivars derived from V. labrusca are classified asAmerican grapes (V. labruscana Bailey). In general, the fruit quality of European grapes is superior to American grapes for table and wine use. During the Meiji era, many European and American grape cultivars were introduced to Japan from foreign countries. However, the cultivation of European grapes failed due to severe diseases and berry cracking caused by Japan’s wet climate. As a result, American grapes such as ‘Campbell Early’, ‘Niagara’, and ‘Delaware’ were selected. Japanese grape breeders have developed many cultivars such as ‘Muscat Bailey A’, ‘Neomuscat’, ‘Kyoho’, ‘Pione’, ‘Kaiji’ and so on, using European and American cultivars as the parent stock. Recently, cultivation of ‘Shine Muscat’ has rapidly increased.
The way of use of grape is divided into two types, i.e. table grape (eat in raw) and wine grape. In Japan, table grape left unsold are used to process to wine in history. But the quality required for table grape and wine grape is completely different. To make good quality of wine, many attentions are paid in recent grape growing. Sugar content is very important because it is converted to ethanol by fermentation. Malic and tartaric acid content is also important for sourness of resultant wine. But these compounds can easily adjust in its concentration by adding to grape juice/must. Besides these compounds, aroma compounds affect greatly to the wine quality. Aroma compounds have volatility and easily escape from liquid phase during wine-making. This effect partially causes the difference between smell of grape and wine. From this point of view, aroma-precursors considered to be more important. Aroma precursor is converted to aroma compounds during fermentation. For example, glucosidic aroma compounds have weak in smell and difficult to evaporate because of its solubility to aqueous phase by the effect of glucose attached. Once the glucose moiety is hydrolyzed with glucosidase during fermentation, it is changed to aroma compounds and is smell. Amino acids in grape berry are assimilated by yeast, and produce higher alcohol. Amino acids have no smell in grape, but their amount and composition will affect wine quality. Other aroma compounds precursors are also taken account of their concentration in grape at harvest for good quality winemaking.