| Accompanying with the change of the human’s concept of consumption and daily diet, the proportion of baking, quick-frozen and Fried food are increased. Consumption of hydrogenated vegetable oils grows rapidly, which leads to risk of consumer heart and circulatory system. Therefore, structuring liquid oil into organic gelled semi-solid status(gel oil) and using it as a substitute of hydrogenated vegetable oil to solve the former problem have important economic and social significance. This study concentrated on the synthesis and purification of mannitol dioctanoate which is a kind of medium-chain dialkanoate of low-calorie sugar and fatty acids. We added the purification product into the liquid vegetable oils to prepare the gelation oil and study the properties of the gelled oil. In addition, we tried to use it as a substitute for hydrogenated vegetable oils in the production of ice cream.The mannitol dioctanoate was synthesized and identification. Solubility of mannitol and esterification ratio of mannitol esters were taken into consideration to select appropriate solvent and enzyme. It was found that the acetone and Novozym 435 were suitable for the experiment, respectively. Mannitol diester was separated and purified by two different methods. They included water/n-hexane, diethyl ether(7:3, v/v) extraction, and the method of silica gel column. The method of silica gel column chromatography to separate and purify the mannitol ester: n-hexane/ethyl acetate/methanol(1:2:2, v/v), 3 min per test tube. The product was continuely purified by semi-preparation high performance liquid chromatography, which was identified as 1, 6-di-O-octanomannitol by MS, FT-IR and, 1H and 13 C NMR. External standard method was used for quantitative analysis of mannitol diester. The highest yield of mannitol diester was 69%, which was achieved in the optimized reaction conditions: molar ratio of octanoic acid to mannitol was 3:1, concentration of lipase was 5 mg/mL, content of mannitol was 0.05 mmol/m L, 60 mg/m L 4 ? molecular sieves, condensation for 72 h at 50°C.The organogels were prepared. The purified mannitol diester was applied to vegetable oils to prepare the gel oils. Effects of gelators and processing conditions on the physical properties of organogels were investigated. Results showed that the mannitol diester has good gelling effect in different plant oils. In the five kinds of common vegetable oils(Soybean oil, rapeseed oil, sunflower oil, corn oil, olive oil), the minimum gelator concentrations varied from 1.3 to 2.5%(w/w). The hardness and SMP of organogels increased with the content of gelator. Soybean oil was used as a model vegetable oil for studying the optimal condition structuring efficiency by the rheological parameters. The optimized preparation of organogel conditions: mannitol octanoic acid ester content was in 10%(w/w), heating temperature of 130°C, the condition of stirring speed was 720 r/min. The storage stability study of gel oil showed that OSI values of different oils were relatively stable, and acid value and peroxide value changed little. With the course of storage time, the physical properties(hardness, the oil line, rheological) tended to be more stable.The properties of organogels by mannitol diester and its application in ice cream were studied. Research on crystallization morphologies and crystallization behavior was carried out on organogels prepared with 10%(w/w) of gelator. The crystallization morphologies of organogel showed micro fibre, and microscopic particles constantly cascading formed dense fibrous structure. In the process of preparation, the cooling rate has a great influence on the crystal morphology. In the cooling rate of 10°C/min, clusters of fibrous crystals were observed by PLM. The crystal density and crystallization rate also improved greatly. The prepared gel oils were used in ice cream products. Expansion rate and melt resistance of ice cream were 79.14% and 26.73%, which were in normal product category. |
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