Abstract
Paddy, brown and polished rice grains, respectively, packaged with a plastic laminated film, were stored over a year in the water of Lake Biwa. The chemical and biological changes during the storage period were analyzed and compared with those of rice grains stored by the conventional method at an atmospheric temperature.
The water proofness of the laminated film under the grain storage conditions, i. e. in the water for a relatively long period, was proved to be highly satisfactory; increment in the moisture content of the grains after one year storage period was lesser than 0.5% in every case. Chemical composition of the grains stored in the water were almost similar to those of the grains in the store house of controlled low temperature. The under-water storage prolonged the storage life of the grains. Original freshness of the grains even after the prolonged under-water storage was evidenced by the facts that considerably higher biological activities such as germinative capacity, and catalase and peroxidase activities were detected for the grains stored in the water than those kept in the atmospheric conditions.
Palatability of the grains stored in the water was found satisfactory. Strength of stale-flavor as determined by the amount of volatile carbonyl compounds, rheological characteristics as measured by texturometric indices and cooking qualities as revealed on boiling, showed that the deterioration pro-ceeded in considerably lower rate for the grains stored in the water than those of the atmospheric storage. Cooking rice prepared from the grains stored in the water for the period of 7 months, as judged by 18 panels, were almost similar to those stored at controlled low temperature, in views of its appearance, aroma, taste, adhesiveness, hardness and overall remarks.
As to the atmosphere within the bags of the laminated film, carbon dioxide enriched one was found more effective than air one in preventing the changes in chemical compositions, in lowering the diminu-tion of peroxidase activity, and in retarding the development of stale-flavor.
