28 巻 (2017) 4 号 p. 289-297
The relationship between rice storage conditions and the physicochemical and sensory properties of cooked rice was investigated. Both polished rice （90％ yield） and brown rice were stored in the following conditions: （i） 37℃ and 75％ relative humidity （RH） for 30 and 80 days; （ii） at room temperature （22.2-27.5℃, 31.3-53.9％ RH） for 180 days from May to November. Treated samples of brown rice storage were polished at 90％ yield after storage. The increase in fat acidity levels after storage was larger in polished rice storage than in brown rice storage, whereas the increase in reducing sugar levels after storage was larger in brown rice storage than in polished rice storage. After storage for 80 days at 37℃ and 75％ RH, the hardness of cooked rice increased, and the stickiness decreased. In addition, compared with the control cooked rice sample, rice quality worsened, hardness increased, and stickiness decreased remarkably after refrigerating cooked rice at 4℃ for 16 h. The peak temperature of gelatinization for rice flour, obtained using DSC, increased after storage but that for rice starch was comparable regardless of storage conditions. This suggests an increase in interactions between rice starch and other ingredients during storage. Sensory evaluation of cooked rice stored at 37℃ and 75％ RH suggested that polished rice storage was better than brown rice storage in terms of aroma and taste. In contrast, after storage at room temperature, it was suggested that brown rice storage was better than polished rice storage in terms of appearance and taste.