乙醇水溶液提取玉米胚芽油的工艺优化

为了解决水酶法提取玉米胚芽油生产成本高、提取时间长的缺点,该文采用乙醇水溶液作为提取剂提取玉米胚芽油。通过对粒径、料液比、温度、乙醇体积分数、p H值和时间等条件对油在油相、水相和渣相中分布的研究发现,物料粒径和乙醇体积分数对提高清油得率具有显著(P0.05)的影响,而提取时间对清油得率的影响最小(P0.05)。在单因素试验的基础上通过正交试验,得出乙醇水溶液提取玉米胚芽油的最佳工艺参数为:物料细粉4次(此时粒径为49.18μm)、料液比1∶7 g/m L、温度70℃、乙醇体积分数30%、p H值9.0、提取时间2 h。在该条件下,清油的得率为94.05%±0.32%,水相含油量为3.49%±0.77%,渣相含油量为2.55%±0.82%。分析乙醇水溶液提取的玉米胚芽毛油酸价、过氧化值和含水率等指标发现,该毛油的质量优于国标规定的玉米原油,并且和压榨一级成品油指标接近,只需要经过简单精炼就可以达到食用油要求。研究结果为乙醇水溶液工业化生产玉米胚芽油提供参考。

Process optimization for extraction of corn germ oil by aqueous ethanol

Corn germ is a kind of byproduct of the wet milling and alcohol industry of corn, which is substantial. Corn germ (dry) contains 35%-56% oil, with linoleic acid (C18:2) being the predominant fatty acid (49%-61.9%). The tocopherol content of corn germ is the highest in all vegetable oils. Corn germ is a cost-effective resource for healthy nutritious oil. In recent years, aqueous enzymatic extraction of corn germ oil has been researched widely. However, this method has the disadvantages of consuming expensive enzyme and long production cycle. In order to reduce the production cost and shorten the extraction time of aqueous method on corn germ oil extraction, the diluted ethanol extraction method was developed in present study based on the consideration that the ethanol added into water was beneficial for demulsifying the emulsion in the homochromous process of oil extraction. Ethanol is a non-toxic and efficient emulsion splitter which has been used in vegetable oil recovery. The product of aqueous ethanol extraction (in appropriate concentration) is directly the free oil rather than the highly emulsified cream after centrifugation. The internal demulsification mechanism is that the diluted aqueous ethanol solution can change the local micro-environment of emulsion and collapse the structure of orderly water molecular around emulsion drops. This method can simplify the follow-up steps and shorten the total production time. Simultaneously, moderate pretreatment was employed to enhance free oil yield further. The research investigated the influence of particle size, solid-liquid ratio, incubation temperature, ethanol concentration, pH value and time for extraction on the oil content of free oil phase, water phase and sediment phase. The result showed that particle size and ethanol concentration made the most contribution to enhancing free oil yield, and extraction time had the minimal impact. The optimal conditions of this aqueous extraction method were: finely ground 4 times (the particle size was 49.18μm), solid-liquid ratio of 1:7 g/mL, incubation temperature of 70℃, ethanol concentration of 30%, system pH value of 9.0 and incubation time of 2 h. Under the optimal conditions, the free oil yield reached 94.05%±0.32%, the residual oil content in water and sediment phase was 3.49%±0.77% and 2.55%±0.82% respectively. Through determining the quality indices such as acidity, peroxide value and water content of crude corn germ oil extracted by aqueous ethanol solution, it could be concluded that the quality of extracted crude corn germ oil was superior to the national standard of crude corn oil, and similar to the first grade pressed corn oil under the national standard. The crude oil extracted by aqueous ethanol solution only needs a simple refining to reach the demand of intake, instead of the “five-step refining” (degumming, depickling, decoloring, dewatering and deodorizing). It can not only simplify the processing, but also preserve the micro nutrients like phytosterol and tocopherol to the greatest extent. Aqueous ethanol extraction method is an efficient and suitable method of extracting corn germ oil, with the peculiarity of mild conditions, simple operations and superior products. Hence, it can be concluded that aqueous ethanol technology has a good applying prospect in oil production industry.