Rapid Gamma-Aminobutyric Acid Production and Shelf-Life Extension of Cooked Germinated Rice Using Ultrasonically Activated Nano-Lime Oil Vapor

Abstract

A short-time process to activate a high level of gamma-aminobutyric acid (GABA) in rice grains is needed to quickly produce healthy rice products as functional foods for treating malnutrition. This study investigated the effects of nano-lime oil vapor (0.001%) generated by an ultrasonic device on accelerating GABA production in germinated brown rice and on reducing pathogenic bacteria in cooked germinated rice. The process included exposure to nano-lime oil vapor, soaking in nano-lime oil, water vapor, and a control treatment before a 48-hour germination period. Nano-lime oil vapor significantly reduced the time required for GABA production from 42 hours to 6 hours, achieving the highest GABA content (86 mg/100g). It also increased reducing sugars (48 mg GE/g), total flavonoids (461 ± 0.07 mg QE/100g), ABTS (4.02 ± 0.01 mg TEAC/g), and FRAP (13.5 ± 0.00 mg Fe²⁺/g) activity. The treated rice showed surface wrinkling, which enhanced GABA content and high levels of bioactive compounds with antioxidant activity. These compounds were linked to reduced microbial growth in cooked rice, extending its shelf life to at least 5 days compared to 1 day for the control. This technique effectively reduces GABA production time, making it suitable for quickly producing ready-to-eat cooked brown rice.