Optimization of bioactive components of three varieties of germinated rice using the rotatable central composite design (RCCD) of the response surface methodology (RSM)
Abstract
Gamma-aminobutyric acid (GABA) is one of the bioactive compounds required for nervous health of man especially that of the elderly. GABA is an inhibitory neurotransmitter in plants and animals. It is present in paddy rice at levels too low for an active functionality in a health food. Germination of paddy rice varieties could increase the concentration of GABA to levels required for human health. GABA is a non-protein amino acid, it is applied to relieve or prevent non-communicable diseases in man especially among the elderly. Synthetic has failed to meet the ideal requirement of a good supplement; affordability, safety and availability and renewability. The work was done to improve the content of GABA in Sesalin, Mars, and Vara rice varieties through germination process. The three rice varieties (X ), were obtained 1 from Ini Local Government Area of AkwaIbom State, Nigeria. Germination of the brown rice was done under the environmental conditions of germination time(X ), steeping time(X ), and temperature of steeping water (X ). The rotatable 2 3 4 central composite design (RCCD) of the response surface methodology was deployed (RSM)for the study to identify terms of the models which exhibited optimum levels of GABA concentration, sensory and market attributes of the germinated brown rice (GBR). The experiment revealed that rice variety, steeping time, germination time and their interactions synergistically influenced the germination process. The model of GABA was significant (p<0.05), R2=0.8722 and mean value =16.03µg/100g of the samples. The models for colour, taste and general acceptability of the samples were not significant (p>0.05), but the response surface plots exhibited some effects on the parameters. Optimization process showed that Vara 44 rice variety, sprouting time of 91.42 hr, 0.023 hr, and steeping water temperature of 37oC produced 906.64ug/100g, 4.53, 4.19, and 7.07 of GABA, colour, taste, and general acceptability of the GBR respectively at 92.80% desirability. More studies are needed using higher values of the independent variables to obtain higher levels of the study responses and education of the consumers on the health benefits of GABA.
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Introduction
Gamma-aminobutyric acid is a major inhibitory neurotransmitter in plants and animals. It is a non-protein ammino acid needed for the maintenance of good nervous health in the mammalian subjects (Magali et al., 2016).GABA acts by sending chemical message through the brain and the nervous system, therefore communicating with the brain cells. GABA may also inhibitor reduce the activity of the neurons or nerve cells. It plays an important role behavior, cognition, and the body response to stress. According to Crawford, (1994) and Thitinunsomboon, et al., (2013) GABA may also inhibits the proliferation of cancer cells, blood pressure regulation. Lower-than-normal levels of GABA in the brain are linked to schizophrenia, depression anxiety and sleep disorders especially among the elderly. GABA supplements taken alone or in combination with other ingredients are marketed widely and used for the management and treatment of depression, anxiety, and insomnia. Synthetic GABA products can induce toxicity depending on the source, abuse, especially through self-medication practices and adulteration (Mie, et al., 2016). Unlike the synthetic counterpart, the plant source of GABA is affordable, safe, cheaper and renewable. This work is seeking plant source of GABA.
Traditionally, one major source of GABA is the brown (unpolished) rice. Its presence is the intact brown rice is at levels, which are too low to support normal human (Totayava, 2014). Germination process can improve the nutrients composition, physiochemical, and functional characteristics of raw, germinated and fermented legume, grains and seed flour (Ijarotimi et al., 2013). According to Totayava, (2014), graded levels of environmental factors like moisture, germination, darkness, and stimuli such as heat shock and cold shock could induce germination and increase rate of synthesis of GABA and concentration in brown rice. Mustapha et al., (2013) and Totayava, (2014) respectively reported that sprouting promotes phytochemical contents of cereals. Germinated rice, which was steeping in water in graded time and temperature of the steeping water, increased the content of GABA (Finney, 2020). However, according to Chaiyasut et al., (2017), excessive soaking rice samples led microbial enrichment, sufficient soaking retarded germination and failed to improve phytochemical content of the samples. Bown, et al., (2006); Chaiyasut et al., (2017); Fengfeng et al., (2013) independently reported that germination time of paddy rice played a critical role in the multiplication of the nascent bioactive chemical compounds in paddy rice. However, paddy rice cannot germinate without the presence of water at appropriate steeping water temperature Chaiyasut et al., (2017).
The UN Food and Agriculture Organization, Corporate Statistical Database (FAOSTAT) (2018) reported that rice sthe seed of the grass species Oryza sativa (Asian rice) or Oryzaglaberrima (African rice). As a cereal grain, it is the most widely consumed staple food for a large part of the world’shuman population, especially in Asia and Africa. It is the agricultural commodity with the third-highest worldwide production (rice, 741.5 million tonnes in 2014), after sugarcane (1.9 billion tonnes) and maize (1.0 billion tonnes).
Due to the high prevalence of acceptance and consumption of rice, it poses as a suitable candidate in food fortification and enrichment nutrition programme especially for the vulnerable group of the world population (Jirapa, et al., 2014 and Nathalie and John, 2013). The study optimized GABA levels, colour, taste, and general acceptability in the three varieties of brown rice; Sesalin, and Mars, Vara 44 (X ), under the influence of controlled sprouting time(X ), steeping water time(X ) and 1 2 3 temperature of steeping water (X ) using the central composite design (RCCD) of the response surface methodology (RSM). 4 The design has superior advantages over the one-factor-at-a-time (OFAT) counterpart.
Conclusion
The present study confirmed that sprouting and sprouting time could increase the concentration of gamma-amino butyric acid in paddy rice irrespective of variety. The absence of moisture inadequate levels cannot induce germination. The brown rice that originated from the experiment showed lower acceptability due to strangeness of the product, hence organoleptic parameters. Education of the target population on the function of GABA and the need to accept the product may lead to higher acceptability irrespective of poor hedonic levels. It is recommended that important of brown rice and related health products should be restricted to encourage local production.