| In this paper, soluble dietary fiber (SDF) was prepared by Trichoderma viride fermentation by using apricot pulp as raw material. Based on the single factor experiments, a four-factor and three-level response surface methodology was applied to optimize the fermentation conditions affecting the extraction rate of SDF. The optimum fermentation conditions were listed:crude enzyme volume,9.59 mL/g; fermentation temperature,43℃; initial pH,5.36; and fermentation time,6.47 h. Under these conditions,15.69% yield was obtained and its relative error with the predicted theoretical value (15.87%) was 1.14%. It revealed that the quadratic source is reliable and feasible.Based on the single factor experiments, a four-factor and three-level orthogonal experiment was applied to optimize the decolouration conditions of insoluble dietary fiber (IDF) from apricot pulp residua. The optimum decolouration conditions were listed: decolourizer regents, H2O2; decolouration time,2.0 h; concentration of decolourizer regent, 3.0%; decolouration temperature,50℃; pH value of decolouration,10.0. The degree of importance of the factors is listed:decolouration temperature > pH > decolouration time> concentration of decolourizer regent.The results of the proximate composition of apricot pulp flour (APF) and soluble dietary fiber isolate, stored under ambient condition are presented. The total dietary fiber for SDF isolate was 84.0%whereas, APF had 43.1% only. After fermentation isolation, most of protein and fat of APF had already been reduced, which also demonstrated the above extraction conditions. The raise content of Ca and Fe showed that the nutritional value of SDF was improved to some extent as well. Its physicochemical properties were characterised by thermal gravimetric analysis (TGA), sanning electron microscope (SEM) and x-ray diffraction (XRD). The results showed that apricot pulp dietary fiber had good thermo stability; the surface of SDF showed poriferous and lax structure. On the contrary, that of IDF showed dense and smooth structure; the crystal structure types of them belonged to Cellulose I.The antioxidant activities of apricot pulp SDF which was prepared by two different methods were compared in this research. The antioxidant activity of apricot pulp SDF was investigated by four antioxidant assays, which contained total reductive ability, scavenging ability for DPPH radical (DPPH·), hydroxyl radical (·OH), and superoxide anion radical (O2-·). The results show that the two different SDF had certain antioxidant activity, and their antioxidant ability increased with the growth of SDF content.At the same time, there were some differences in their infrared spectrum, because of the different hydrolyzing degrees.The anti-diabetic effect of apricot pulp SDF on rat models of diabetes was investigated. Both of blood glucose level and body weight were significantly changed in apricot pulp SDF-treated groups compared with the diabetic group (p< 0.01) after intragastric administration 28 days. In addition, SDF elicited inhibitory effects on α-glucosidase activity with an IC50 of 17.458 mg/mL. After 4 weeks of administration, the blood glucose level of low-dose, middle-dose, and high-dose diabetes rats were decreased 36.3%,36.5%,39.0%, respectively. These results implied that apricot pulp SDF relieved the symptoms of diabetes rats.In this study, the crude polysaccharide (APPS) from the fruiting bodies of apricot (Armeniaca sibirica L. Lam.) was isolated and fractionated by ultrafiltration and Sephadex G-75 gel chroma to graphy. The hypoglycemic activities of all fractions were determined by α-glucosidase inhibitory activity in vitro. The fraction APPS 1-2 showed the best activity with an IC50 of 6.06 mg/mL. The properties and chemical compositions of this fraction were analyzed with high-performance liquid chromatography, gel permeation chromatography-eighteen angle laser light scattering instrument, UV spectroscopy, infrared spectroscopy, and NMR spectroscopy (1H). The results demonstrated that APPS1-2 was a neutral glycoconjugate with a molecular weight of 25.93 kDa. It comprised rhamnose, glucose, mannose, and galactose, with a relative molar ratio of 1.342.01:0.48:0.35. The backbone of APPS1-2 may consist of rhamnose and glucose, but its branches may consist of mannose and galactose. The IR and UV spectrum of APPS 1-2 revealed the typical characteristics of heteropolysaccharide.1HNMR spectrum showed that APPS 1-2 contained a-configurations. |
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