Storage Life and Taste of Rice Unusually Long Term Stored at a Low Temperature

研究了超长期冷藏稻谷的品质变化。1976~1994年，在日本东京大学实验农场的同一块稻田里，采用固定种植方式，包括种植距离和施肥量，每年栽培和收获日本光头水稻。稻谷在充分成熟和晒干后进行联合收割。稻谷每年冷藏在3~5ﾟC的温度下，对稻米品质进行检测，包括糙米和精米的白度、水分含量、发芽率、脂肪酸、直链淀粉含量、近红外法测定的食味指数、稻米和小胚轴的真菌侵染率。从时间上看，发芽率在7年内几乎保持不变，约为80%以上，但在此之后立即迅速下降。贮藏10年后，发芽率降至零。虽然受冷藏的影响，脂肪酸一直保持在较低的水平，但随着储藏时间的延长，脂肪酸的含量逐渐增加。糙米的白度随储藏年限的增加而降低，而精米的白度变化趋势不明显。贮藏过程中受低温和相对潮湿环境的影响，水分含量增加。随着储藏年限的增加，米饭的口感明显变差。真菌感染百分率对其他评价因子无显著影响。活菌总数最初在10^7个/粒左右，随着储藏时间的延长，活菌总数逐渐减少。Iizuka和Itoh指定的所谓红色假单胞菌占活细菌总数的比例随着储存时间的推移而增加。

Quality changes of very long term cold stored paddy were examined. From 1976 till 1994, rice, cultivar NIPPON-BARE,had been cultured and harvested every year at the same paddy field of the Experimental Farm of the University of Tokyo, under a fixed cropping pattern including planting distance and fertilizer application. Paddy was combine harvested after sufficient ripening and sun drying. Paddy had been stored every year in a cold storage at the temperature of 3-5ﾟC.Qualities of rice, including whiteness of both brown and milled rice, moisture content, germination percentage, fatty acid, amylose percentage, taste index measured by SATAKE-TASTE ANALYZER by means of NIR method, percentage of fungi infected grain and microflola, were examined. Chronologically speaking, germination percentage had kept almost constant for 7 years about 80% or more, however, it decreased rapidly immediately after that period. After ten years storage, the germination percentage fell to zero. Although fatty acid had maintained relatively low value by the effect of cold storage, it increased gradually according to storage term lengthend. Whiteness of brown rice decreased as stored year increased, but that of milled rice did not show apparent trend. Moisture content increased by the influence of low temperature and relatively humid atmosphere in the storage. Taste of rice had significantly got worse as the storage year increased. Fungi infected percentage did not give significant influence on other evaluation factors. Total count of living bacteria was in the order of 10 ^7count/grain at first, and decreased as the storage time passed. Percentage of so-called Red Pseudomonas appointed by IIZUKA and ITOH,to the total living bacteria increased as the storage time passed.