酸性浸润干燥辅助低水耗水代法提取亚麻籽油工艺

Technology for aqueous extraction of flaxseed oil with method of lower water consumption by pretreatment of acidic moisture-conditioning plus drying

为解决传统水代法提取亚麻籽油过程中乳状液生成过多,耗水量大等问题,该文在低料液比1:2.5 kg/L的条件下,探究了水代法提取亚麻籽油的工艺。结果表明,酸浸润预处理通过影响亚麻蛋白的溶解度,有效提高水代法中的清油得率,由未处理时的18.95%±0.91%提升至83.27%±0.67%。水代法提取亚麻籽油的工艺优化结果为:pH值9.0、温度50℃、料液比1∶2.5 kg/L、提取时间2 h。在此条件下,清油得率为82.88%±0.30%。在水代法提油后的水相中添加50%原料质量的纯水重复提取渣相后,渣相残油率从3.97%±0.11%降至2.09%±0.04%。剩余乳状液经木瓜蛋白酶破乳后,总清油得率为93.44%±0.29%。水代法得到的亚麻籽油各项指标均符合一级成品亚麻籽油标准。该研究为亚麻籽油的高效提取提供了一种新的思路。

Aqueous extraction processing(AEP) is an environmentally friendly method to extract oil from various plants at a moderate temperature. However, the AEP alsohave several limitations. Firstly, the cream can be inevitably produced to form a sort of highly stable oil-in-water emulsiondue to the adoption of water, stirring and centrifugation during processing. The formed emulsion become difficult to break completely, resulting in a huge challenge for the AEP performance. Secondly, the water that used in AEP normally serves as an extraction medium, but the usage of excessive water can result in the formation of thick suspension, which making it hard to directly release free oil. In general, the ratio of seed to water 1:5 kg/L or even higher was mostly chosen as the optimal ratio to eliminate the thick suspension as well as stable cream. However, the substantial consumption of water increased the treatment cost of subsequent wastewater after processing. A modified aqueous extraction of flaxseed oil was investigated using a low consumptionof water under acidic wetting and drying, in order to enhance the AEP extracted yield of free flaxseed oil,while decrease the consumption of enzyme and water. The results showed that the yield of free oil was improved significantly due to the solubility effects of flaxseed protein under the pretreatment of acidic moisture-conditioning plus drying. In untreated flaxseed kernels, the free oil yield was only 18.95% ± 0.91%, while71.29% ± 1.87% of the extracted oil went preferentially into the cream fraction. By contrast, the free oil yield increased to83.27%±0.67% with the pretreatment of acidic moisture-conditioning plus drying. There was a vast increase in the amount of protein distribution in sediment phase under the pretreatment(from 33.34% ± 0.34% to 60.25% ± 0.44%), while the protein distribution in aqueous phase consequently decreased from 66.74±1.04% to 39.78%±0.66%. Processing conditions of aqueous extraction were also optimized by single-factor experiments, and the optimal parameters were obtained as follows: the extraction temperature was 50 ℃, pH value was 9.0, the ratio of flaxseed to water was 1: 2.5 kg/L, extraction time was twohours. The recovery of free oil was achieved 82.88%±0.30% under the optimum conditions. Due to the increase of protein content in sediment phase and low flaxseed to water ratio of 1:2.5 kg/L, a part of oil was entrapped in sediment phase, which limited the further improvement of total oil yield. The sediment phase was further extracted by the aqueous phase plus deionized water, wherethe quality of deionized water was 50% quality of raw materials. The oil that distributed in sediment phase decreased from 3.97%±0.11% to 2.09%±0.04%after the second extraction. Subsequently, different enzyme and freezethaw were used to treat the demulsification of residual emulsion.The total yield of free flaxseed oil was 93.44%±0.29% after the residual emulsion was demulsified with papain. After detecting the characteristic value of flaxseed oil from aqueous extraction processing and pressing extraction, the experiment came to a conclusion:There were no significant differences that observed on therefractive index, iodine value, conjugated diene value and conjugated triene value. Although the peroxide value of flaxseed oil by aqueous extraction processing was slightly higher than that by pressing extraction,it still well below the maximum value of cooking oil(10 mmol/kg).These findings demonstrate that the proposed pretreatment with low water consumption under acidic moisture-conditioning plus dryingis suitable for the aqueous extraction of flaxseed oil. Therefore,this presented study can provide a promising technology for the extraction of flaxseed oil, where can increase the free oil recovery, while reduce the water consumption and the amount of enzyme.