Study On Preparation Of FOS By Garlic

Fructo oligosaccharides(FOS) are a new source of healthy sugar in the 21st century, which are difficult to digest and anti-caries and have functions of regulating intestinal balance, relieving constipation and diarrhoea, reducing blood lipid, enhancing immunity, promoting the absorption of trace elements.Garlic is an important edible and medicinal plant, which is widely cultivated in China. The content of garlic polysaccharide is more than 22%, which is miscellaneous fructan and mainly composed of inulin. So garlic is an good material for extracting fructo oligosaccharides (FOS).In this paper, the extraction, ingredients analysis and law of acid hydrolysis of garlic polysaccharide were studied systematically, and purification of FOS was explored preliminarily. The main contents and the conclusions were as follows:After extracting garlic oil and drying, garlic polysaccharide was prepared by hot water extraction, removing protein, small molecular saccharides, pectin and other impurities from garlic residues. In this paper, operating conditions of phenol-sulfuric acid method for determining garlic polysaccharide content were confirmed based on the contrast experiment, and the extraction process of garlic polysaccharide was optimized after investigating the effect of the extraction temperature, ratio of material to water, and time on extraction rate by single factor and the response surface method. The optimum operating conditions of phenol-sulfuric acid method for determining garlic polysaccharide content were the following:anhydrous glucose is used as reference substance, phenol solution concentration is 5%, phenol solution dosage is 1.0ml, concentrated sulfuric acid dosage is 5.0ml, placing for 20min in boiling water bath, cooling by flowing water, and the detection wavelength is 490nm. In the best operating conditions, the correlation coefficient(R2) of the standard curve for determination was 0.9993, the relative standard deviation (RSD) of sample determination was 2.47%, and the relative standard deviation (RSD) in reappearance experiments was 2.73%. The optimum parameters of garlic polysaccharide hot water extraction were as follows:extracting temperature is 75.3℃, the ratio of material to water is 1:30g/ml, and extraction time is 2.25h. The extraction rate of garlic polysaccharide was 61.45%. The effect degree order of the factors on polysaccharide extraction is:extraction temperature> extraction time> the ratio of material to water. The influences of each factor on the extraction rate of garlic polysaccharide are not simple linear.Component, structure and content of garlic polysaccharide were analyzed by thin-layer chromatography, infrared spectrometry and ultraviolet spectrophotometry methods. Thin-layer chromatography analysis results showed that the main component of garlic polysaccharide is fructose. Infrared spectrum analysis results showed that garlic polysaccharide is miscellaneous fructan, linked byβ-glucosidic bond. UV spectrophotometry results showed that the fructan content in garlic polysaccharide is 79.05%. UV spectrophotometry is simple, rapid and sensitive.It has good selectivity and accuracy, and is suitable for content determination of fructose in complicated substances.The law of acid hydrolysis of garlic polysaccharide was analysised, the influences of the kind of acid, pH value, substrate concentration and temperature on the hydrolysis process of garlic polysaccharide were studied and the hydrolytic dynamics model of garlic polysaccharide was established. The results showed that, the hydrolysis degree reduces when the pH value rise; The greater is substrate concentration, the lower is the hydrolysis degree at the same time, and the longer time is required to complete hydrolysis. When the pH value is two, and substrate concentration of garlic polysaccharide is mass concentration of four percent in hydrolisis lipid, the hydrolysis reaction is pseudo-first-order reaction in experiment temperature range (From forty to eighty centidegree). The hydrolysis rate at different time declines overall at each temperature, but only a little, which is relevant with the inhibition of products. As the temperature increases, the hydrolysis rate constant increases. It was found that the hydrolysis rate constant is much higher at eighty centidegree than seventy centidegree, and variation of the hydrolysis rate constant is exponential with temperature changes, which accordes with Arrhenius model generally. The Arrhenius model of acid hydrolysis of garlic polysaccharide is k=1.75×108exp(-7.78×104/RT). Then the relation between the hydrolisis degree and hydrolysis temperature and time is:HD=1-1/exp{[1.75×108exp(-7.78×104/ RT)]t}. Experiments had proved that using hydrochloric acid to hydrolysis garlic polysaccharide to prepare FOS is feasible.Nanofiltration separation technology of FOS was studied preliminarily, and two-stage nanofiltration and reverse osmosis separation method were adopted to separate the FOS solution into three different sections according to molecular weight differences. In the process of two stage nanofiltration membrane separation, the flux variation is very obvious:Firstly, higher multiples of material diluent, larger membrane flux. In the process of nanofiltration of the same membrane flux doesn't change very big overall, which showes that the nanofiltration membrane is relatively stable; Secondly, with the process of nanofiltration, membrane flux decreases a little. In treatment of lower concentration feed liquid, the attenuating range of membrane flux is more apparent. But the membrane flux as treating low concentration material liquid is generally larger than treating high concentration material liquid; Thirdly, higher pressure, larger membrane flux. At the same time, the flux attenuation rate is more and more obvious as the pressure increases; Forthly, higher the temperature, larger the flux. Fifthly, bigger the elution multiple, larger the membrane flux. At the start of elution, the flux changes little. But increasing trend of flux is weakening with the increasing of elution multiple. In the process of nanofiltration purification, the purification effect is obvious with the increasing of elution multiple. When the solution was eluted ten times, FOS in 90.03% purity was obtained at a 12.8% yield.