Subcritical Butane Extraction Of Macadamia Nut Oil And Purification Of Polysaccharide From Macadamia Nut Defatted Flour

Macadamia nut is the distinctive production in tropic, and it contains high amounts of oil with rich nutrition. At present, most of macadamia nuts in domestic were sold in its original fruit, and it was deficient in the deep processing and theoretical research about its oil and by-products. For the purpose to further develop the oil and by-product processing, the subcritical butane method for oil extraction in macadamia nut was investigated. Besides, the isolation, purification and structural analysis of polysaccharide extracted from defatted macadamia nut flour were studied.Firstly, the oil was extracted by subcritical butane, and the effects of different factors such as extraction temperature, extraction pressure, extraction time, the ratio of material to solvent and the extraction times on the extraction yield were optimized. Meanwhile, hot-press, cold-press and hexane extraction were compared by the changes of the physical-chemical properties and fatty acid profile.Furthermore, the polysaccharide from the macadamia nut defatted flour was extracted by hot water, and the supernatant was precipitated by stepwise alcohol. Protein removal rate and polysaccharide loss rate were used to evaluate the effectiveness of Sevag’s method, TCA method, alkaline protease method and alkaline protease-Sevag’s method. Then the preliminary deproteinized polysaccharide was loaded onto DEAE-Sepharose Fast Flow and Superdex 200 column respectively for further purification.Ultimately, the purity and the molecular weight were determined by UV scan and HPGPC, the monosaccharide compositions was determined by HPLC, combine with IR and NMR to investigate the structure characteristics.The main conclusions were as follow:(1) The optimum macadamia nut oil extraction yield was 80.7%, when the macadamia kernel were extracted by 1:5 g/m L subcritical butane at the temperature of 35℃ for 4 times, and 15 min each time.(2) The subcritical butane extraction method had more advantages than hot-press, cold-press and hexane extraction, and the quality of the oil were good so that most of the refining process could be omitted. The macadamia oil contained abundant amounts of oleic acid(56.50%), palmitoleic acid(16.85%), palmitic acid(8.90%) and stearic acid(3.97%).(3) The alkaline protease-Sevag’s method was the best way for removing protein in crude polysaccharide extracted by hot water, and the the optimum condition was using 1%(v/v) alkaline protease, hydrolyzing 3h at the temperature of 50℃, followed by Sevag’s method. A protein removal rate of 92.3% and a polysaccharide loss rate of 39.9% were achieved under such conditions. Then, the preliminary deproteinized polysaccharide could be completely purified by collecting the main eluting peak of DEAE-Sepharose Fast Flow and Superdex 200 clomn. The pure polysaccharide, named MIPS2 a, had no nucleic acid, protein or pigment characteristic absorption showed in UV scan.(4) MIPS2 a was pure with the molecular weight of 463.8k D, and the monosaccharide composition was determined as rhamnose, glucuronic acid, galacturonic acid, and arabinose with a molar ratio of 0.32:0.29:0.83:0.80. The IR and NMR analysis suggested that MIPS2 a had the normal characteristic of polysaccharide and the monosaccharide composition was identical with HPLC analysis.