Abstract: The aging degree of rice has a direct influence on its eating quality, and the requirements for the aging degree of rice during processing vary according to the form of final products. In order to determine the correlation indexes and threshold intervals of rice suitable for the processing of cooked rice and rice noodles and to establish a rapid method to identify the eating quality of cooked rice and rice noodles, this study measured the biochemical and gelatinization properties of rice with different aging degrees stored under accelerated conditions and evaluated the eating quality attributes of cooked rice and rice noodles made from aged rice. The data obtained were analyzed by principal component analysis (PCA), cluster analysis (CA) and stepwise regression (SR). The aging degree of rice was detected using acid-base indicators and L*, a* and b* were recorded. Finally, the color was restored by image processing software to develop a colorimetric card for rapidly identifying the eating quality of cooked rice and rice noodles based on rice grain quality. The results showed that the regression equation between the comprehensive score of cooked rice (Y) and its fatty acid content (X) was Y = 7.729 − 0.236X. Based on Y, the quality of cooked rice could be divided into excellent (Y ≥ 2.361), medium (− 1.039 ≤ Y < 2.361), and poor (Y < − 1.039) and the corresponding thresholds for fatty acid contents were X ≤ 23 mg/100 g, 23 mg/100 g < X ≤ 37 mg/100 g, and X > 37 mg/100 g, respectively. The regression equation between the comprehensive score (Y) and fatty acid content (X) of rice noodles was Y = − 17.030 + 1.021X − 0.015X2. Likewise, the quality of rice noodles could be divided into 3 grades: excellent (Y ≥ 0.244), medium (− 1.589 ≤ Y < 0.244), and poor (Y < − 1.589), and the corresponding thresholds for fatty acid contents were 31 mg/100 g ≤ X ≤ 37 mg/100 g, 37 mg/100 g < X ≤ 45 mg/100 g, and X > 45 mg/100 g, respectively. The colorimetric card based on fatty acid content allows direct identification of the suitability of rice for the processing of cooked rice and rice noodles, which will providing a basis and guidance for the processing of rice grains.

Key words: rice; cooked rice; rice noodles; fatty acid content; eating quality