Production and characterization of fermented rice flour containing gamma-aminobutyric acid (GABA)
Abstract
Fermented foods provides therapeutical attributes beyond their basic nutritional value and are known to reduce disease risk. Broken rice was fermented using Enterococcus faecium NCIM 5593 and its fermentation characteristics was studied. Attempts were made to formulate gamma -aminobutyric acid (GABA) containing fermented rice flour (GFRF) by lactic acid fermentation. Fermentation enhanced the level of GABA and antioxidant phenolics. GFRF exhibited potential antioxidant capacity evaluated against DPPH (77.89±1.85 mg vitamin C equivalent/g dry matter) and ABTS (163.21±2.81 mg vitamin C equivalent/g dry matter) radicals. Fermentation significantly increased the levels of proteins and reduced carbohydrate content. Microstructure of GFRF was also influenced, where its starch granules where released from its enclosed structure after fermentation. In addition, fermentation enhanced the whiteness of the flour. This investigation shows evidence that fermentation modified the functionality of GFRF and can be used as a functional food ingredient. Further studies are directed towards studying the effect of GFRF extract to ameliorate neurotoxin induced oxidative dysfunctions and neurotoxicity in mice model.
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Introduction
Rice (Oryza sativa), being one of the most produced and consumed grains in the world, is a rich source of bioactive compounds, including many phenolic antioxidants (Mira et al., 2008; Zhang et al., 2010). One of the main byproducts of rice processing is broken rice. Broken rice is separated from head rice during rice milling process and is known to occur to approximately 1 to 13% of milled rice (Lee et al., 2011). Most broken rice is mainly used as animal feed and low-priced rice cakes as it is inadequate for regular consumption. One way of utilizing such broken rice is by fermentation process. It has been used to produce lactic acid (Nakano et al., 2012) and ethanol (Gohel and Duan, 2012) with high fermentation efficiency. It thus may serve as an important raw material for fermentation. Lactic acid bacteria (LAB) are industrially important microbes that are used world over. Consumption of lactic acid fermented foods is common in many Asian countries. Fermented foods offer an array of health benefits as they improve organoleptic quality. Fermentation also results in improved digestibility and nutritive value (Arici and Daglioglu, 2002). Health benefits from the fermented plant materials are usually direct, through interaction of ingested live microorganisms with the host (probiotic effect) or indirect as a result of the ingestion of microbial metabolites, which are synthesized during fermentation (biogenic effect) (Gobbetti et al., 2010). Cereal fermentation leads to improvement in product shelf life, nutritional value, and digestibility and significantly lowers antinutritional contents in the final products (Karovicova, 2007).
Gamma-aminobutyric acid (GABA) is a four carbon non-protein amino acid that acts as a major inhibitory neurotransmitter in central nervous system (CNS) (Kinnersley and Turano, 2000). Numerous studies have proclaimed the role of GABA as an antihypertension, anticancer, anti-inflammatory and hepatoprotection agents (Watanabe et al., 2006; Kang et al., 2011; Ali et al., 2013). These aspects have stimulated the interest to formulate GABA-containing natural product (Ali et al., 2013). Thus the purpose of the study was to formulate GABA containing fermented rice flour (GFRF) using a potent GABA producer, E. faecium NCIM 5593. The reason to enhance GABA levels by microbial fermentation is because of its varied health benefits: GABA promotes fat loss by the stimulation of human growth hormone production, increases sleep cycle by giving deeper rest, boosts immune system, lowers blood pressure, inhibits development of cancer cells and also assists in the treatment of anxiety disorders (Oh and Oh, 2014; Ito and Ishikawa, 2004). In addition, Ito and Ishikawa, (2004) suggested that GABA has preventive effects on Alzheimer’s disease and other cerebral related disorders, such as amnesia and dementia.