Green aroma is widely present in fruits such as strawberries, bananas and apples, tree leaves, tea leaves and vegetables, etc., and plays an important role in aroma and taste. In the perfume industry reproduction of aroma or taste of natural products is an important subject. Thus, it is essential to utilize substances having the green aroma.
The main components of the green aroma are said to be aliphatic aldehydes and alcohols. At present chemically synthesized compounds such as n-hexanal, n-hexanol and hexene-3-ol are utilized. The green aroma in natural products is not represented by one or two synthetic substances, but is complicated. In order to obtain more natural green aroma, further research and development are necessary. In recent years health and fitness has gained popularity and it is increasingly desired to obtain flavors using only natural products which have been considered as safe. In regard to the green aroma, natural substahces are required. However, there are few substances having an excellent green aroma. Therefore, development of such substances is now required.
Until now, investigations have concentrated on a method for removing soybean odor including green aroma during the processing of soybeans into foods. The present inventors have considered utilizing the mechanism of generation of green aroma in soybeans for the production of such aroma. That is, it was thought that in processing raw soybeans to produce soybean milk, if they were ground at low temperatures, their odor including green aroma would be generated and the milk would be inferior in quality, so, during the traditional processing the soybeans were ground at high temperatures which cause inactivation of enzymes in the soybeans. Therefore, investigations were not substantially made on how strong the green aroma was when it is generated while supplying air or oxygen.
The present inventors have found that the green aroma is generated when raw soybeans are ground in the presence of oxygen within the temperature range not causing inactivation of enzymes in the raw soybeans and then stirred in a fermentor while supplying air or oxygen. Further, they have found that the green aroma can be strengthened by adding higher unsaturated fatty acids which are considered to be precursors of the green aroma. Furthermore, it has been found that the green aroma components formed vary according to the types of fatty acids added. It has been confirmed that introduction of natural fats and oils as an unsaturated fatty acid source is effective in increasing the green aroma. It is considered that in the green aroma generation reaction lipase present in the soybeans participates, and it has been found that if lipase is added alone or together with the fatty acids, triglycerides in the fats and oils are positively decomposed and the formation of the green aroma component can be increased.