Rice starch properties affect the retention of 2-acetyl-1-pyrroline in raw rice during cooking and the release of 2-acetyl-1-pyrroline from cooked rice after cooking

Abstract

2-Acetyl-1-pyrroline (2-AP) is the major aroma compound in fragrant rice. However, it declines upon cooking and its release could be interfered with the starch matrix. This study was conducted to evaluate the relation between 12 fragrant Japonica rice varieties’ starch properties and 2-AP retention during cooking (RT_2-AP) and the matrix effect hampering 2-AP release from cooked rice utilizing Partial Least Squares Regression (PLSR). Results showed that rice varieties with elevated levels of relative crystallinity, gelatinization enthalpy, and a wider gelatinization temperature range exhibited higher RT_2-AP. It suggested that rice varieties with starch structure maintained higher integrality upon cooking could retain more 2-AP. Meanwhile, greater stickiness of cooked rice was associated with a more severe matrix effect. Leached materials controlled the release of 2-AP from cooked rice. Factors of the leachate (the solid content, leached amylopectin content, leached amylopectin weight, and the proportion of short chains of leached amylopectin) that contributed to the formation of a more viscous coated layer led to greater difficulties for 2-AP release from cooked rice. Results revealed the relationship between the apparent properties of rice and 2-AP retention and release upon cooking, which could benefit the aroma enhancement of cooked rice in the future.