Accelerated aging by microwave heating and methods to distinguish aging of rice.

Aim: To study the impact of microwave heating (950 and 1,400 W for 72 s) in accelerating the aging process in selected rice varieties, namely IR‐50, Sona masuri, and RNR‐15048 (Rajendranagar variety) stored as brown and polished form. Methods: The impact was investigated by comparing the efficiencies of two existing chemical methods, namely bromothymol blue indicator (Method‐1) based on the indicator color change with respect to changes in rice pH followed by peroxidase enzyme color reaction (Method‐2) using test tube (spectrophotometer at 470 nm) and single‐grain tests (96‐well plate microplate reader at 386 nm) paralleled with in vitro enzyme assessment for fresh‐aged indices calculation during 6 months of storage. Results: The results revealed the maximum R2‐value of 0.993 (brown rice) and 0.963 (polished rice) at 1,400 W for 72 s in RNR‐15048 in single grain test (Method‐1) followed by a maximum R2‐value of 0.976 in brown rice of Sona masuri at 950 W for 72 s and 0.941 in polished rice of RNR‐15048 at 1,400 W for 72 s in single‐grain test (Method‐2). Conclusion: Among the above methods, Method‐1 was found to be more profound in obtaining the consistent results and can be highly recommended for both stake holders and rice processing agencies due to low cost, ease in chemical preparation, and color changes can be easily distinguishable during storage. Practical Applications: Aging is one of the important and prudent steps in rice grain. Aged rice fetches more price in the market than fresh rice due to improved aroma, texture, and taste after cooking. Accelerated aging requires less storage space and time compared to natural aging. Identification of the aging process in rice grains is a challenging task. Bromothymol blue indicator based on pH change in rice grains due to increase in free fatty acids and peroxidase enzyme color change due to peroxidase enzyme (EC.1.11.1.7) depletion during storage helps to identify the rice aging through fresh‐aged index calculation. Among both the methods, Bromothymol blue indicator is one of the cost‐effective methods for quick identification of rice aging based on indicator color change. This method helps the farmers and other rice processing sectors to distinguish the aged rice from fresh grains as it is cheap, ease in chemical preparation, and affordable. [ABSTRACT FROM AUTHOR]