Effects of high-temperature cooking on the gamma-aminobutyric acid content and antioxidant capacity of germinated brown rice (Oryza sativa L.)

Abstract

Germinated brown rice (GBR) has a high gamma-aminobutyric acid (GABA) content and antioxidant capacity; however, the effects of high-temperature cooking on these characteristics are unclear. We investigated alterations in GABA content, antioxidant capacity, 15 proteinogenic amino acids, TP and reducing sugar content, and color of cooked GBR at 105°C to 135°C and at different times (40 to 90 min) at 105°C. The contents of GABA and 9 proteinogenic amino acids decreased via thermal decomposition with increasing cooking temperatures. The hydrophilic and lipophilic antioxidant capacities (DPPH and L-ORAC) were enhanced at temperatures >125°C. L-ORAC values were strongly associated with the glucose content and L*, a*, and b* values. Additionally, prolonged treatment time decreased the content of 12 amino acids but increased DPPH and L-ORAC. Our results on functional ingredients and activity are useful for both home cooking and manufacturing processes and may lead to the development of better-processed products.

Surface disinfection influences the antioxidant capacity and GABA content of saline‐treated brown rice (Oryza sativa L.)

“…Although soaking for 24 h has been reported to increase the antioxidant capacity of some BR varieties (Owolabi et al, 2018), the findings reported herein showed a reduction in antioxidant capacity compared with untreated BR (control group). This was consistent with the findings of our previous study (Toyoizumi et al, 2021).…”

“…DPPH radical‐scavenging activity was determined as described by Toyoizumi et al (2021). Briefly, 0.25 g of powdered samples were diluted fourfold with an 80% v/v acetone solution and extracted by stirring for 1 min at 25°C.…”

“…Extraction and determination of TP were performed as described by Toyoizumi et al (2021). TP content of the samples was determined using the Folin‐Ciocalteu method, with gallic acid (GA) as the internal standard.…”

“…Extraction and determination of amino acids were performed as described by Toyoizumi et al (2021). Briefly, samples were diluted tenfold with 0.1 M hydrochloric acid and extracted by ultrasound sonification for 10 min at 37°C.…”

Rice Bran Stabilisation and Oil Extraction Using the Microwave-Assisted Method and Its Effects on GABA and Gamma-Oryzanol Compounds

“…Toyoizumi et al [ 59 ] reported a decrease in the GABA content and most amino acids when cooking germinated brown rice at high temperatures (105 °C, 115 °C, 125 °C, and 135 °C) for 40 min. Therefore, there was a thermal decomposition of these compounds.…”