| In recent years,the annual consumption of edible vegetable oil in China has exceeded 40 million tons,but the self-sufficiency rate is only 30%,and the gap is huge.Under the condition of not competing for land with grain,it is an important measure to improve the use of woody oil and minor oil.Oilsha beans are one of the small oils that have been vigorously promoted in my country,which is included in the "National Planting Structure Adjustment Plan(2016-2020)".Cyperus esculentus is one of the small-scale oilseeds vigorously promoted in China,and it is a recommended crop variety listed in the "National Planting Structure Adjustment Plan(2016-2020)".In recent years,the research on the oil-making technology and quality analysis of Cyperus esculentus has gradually increased,but there are few studies on the influence of Cyperus esculentus quality on its crude oil quality and the influence of different crude oil quality on the oil refining process.At the same time,because of the unique component characteristics of Cyperus esculentus,its oil flavor is obviously different from other common oils,but there are few reports on the volatile flavor components and sensory evaluation of Cyperus esculentus oil.However,in order to meet the needs of the industrialization development of Cyperus esculentus oil processing,it is necessary to study the refining of Cyperus esculentus oil and the development of product flavor and comprehensive quality.Therefore,this paper takes Cyperus esculentus with different quality as raw materials to extract Cyperus esculentus crude oil,analyzes the influence of different raw materials on the quality of Cyperus esculentus crude oil,then different quality Cyperus esculentus crude oil are refined,compares and studies the influence of different Cyperus esculentus raw materials on the quality of its crude oil,and the influence of crude oil quality on the refining process effect and the comprehensive quality of the final product.In order to provide support for the development of processing technology and product development of Cyperus esculentus oil.(1)Twelve Cyperus esculentus oil samples were prepared with different quality Cyperus esculentus beans(high-quality beans,moldy beans and their corresponding peeled beans)as raw materials by different methods(leaching,cold pressing and hot pressing).The quality index,nutrient content and oxidation stability of the oil samples were tested and analyzed,and the effects of raw material quality and oil preparation methods on the comprehensive quality of Cyperus esculentus oil were studied.The results showed that Cyperus esculentus was rich in total sugar and polyphenols,with the total sugar content of45.6%～46.6% and polyphenols content of 824.73 mg/kg ～ 936.20 mg/kg.After peeling,the crude protein and fat content of Cyperus esculentus increased slightly,the crude fiber content decreased obviously,and the crude protein content increased from 4.1%～4.7% to 4.8% ～ 5.4%.The crude fat content increased from 22.18%～23.10% to 23.34% ～ 25.47%;The crude fiber content decreased from 16.0%～22.8% to 4.7% ～ 7.4%;No aflatoxin-B1 harmful substance was detected in Cyperus esculentus and Cyperus esculentus oil,whether Cyperus esculentus was moldy or not.Then,the comprehensive quality of these Cyperus esculentus crude oils were analyzed.The results showed that the acid value and peroxide value of high-quality Cyperus esculentus crude oils were 1.2～3.1 mg/g and 0.01～0.11 g/100 g respectively,and the acid value and peroxide value of moldy Cyperus esculentus crude oils were 24.1 ～29.6 mg/g and 0.02 ～ 0.24 g/100 g respectively.Cyperus esculentus oil is rich in unsaturated fatty acidoleic acid,accounting for more than 73.99%.The sterol content range of high-quality peeled Cyperus esculentus oil is 209.24 to 251.04 mg/100 g,and that of mildewed Cyperus esculentus oil ranges from 142.17 to 200.20 mg/100 g.Peeling is beneficial to increase the sterol content in Cyperus esculentus oil.The vitamin E content of high-quality Cyperus esculentus is207.04～251.18 mg/kg,and that of moldy Cyperus esculentus oil is 169.16 ～249.81 mg/kg;The content of phospholipid is 148.13 ～ 5027.31 mg/kg;The oxidation induction time of different Cyperus esculentus oil is squeezed oil(1.4～2.19 h),hot squeezed oil(2.33～3.27 h)and leached oil(29.47～39.77 h).The results showed that the quality of Cyperus esculentus oil was greatly influenced by the quality of raw materials,so it was necessary to prevent Cyperus esculentus oil from deteriorating as much as possible during its storage.(2)The volatile components of different Cyperus esculentus oil(cold pressing and hot pressing)were detected and analyzed,and the characteristics and key volatile components of Cyperus esculentus oil were identified.The results showed that 10 types of 242 compounds were detected in 6 Cyperus esculentus oils from 3 producing areas,and there were 18 components.The relative concentration of volatile substances in cold pressed of Cyperus esculentus oil is 20227.61 μg/kg in sample 1,and that in hot pressed oil is 22347.29μ g/kg;The relative concentration of volatile substances in cold pressed Cyperus esculentus oil is59,329.46 μ g/kg in sample 2,and the concentration of volatile substances in hot pressed oil is71,886.64 μ g/kg.The concentration of volatile substances in cold pressed Cyperus esculentus oil is 68699.15 μg/kg in sample 3,and that in hot pressed Cyperus esculentus oil is 70059.60μg/kg.Due to the different producing areas,the concentrations of volatile substances in Cyperus esculentus oil samples are also different.The concentration of volatile compounds in hot-pressed oil is obviously higher than that in cold-pressed oil by different extraction processes in the same producing area.The main volatile components in Cyperus esculentus oil are aldehydes,accounting for 18.95%～55.35%,followed by alkanes(19.27%～40.60%)and esters(0.76%～27.90%),and the content of heterocyclic compounds is 0.82%～7.4%.The content of alcohols is 0.82% ～ 7.27%;the content of olefins is 0.49% ～ 3.94%;the content of acids is 0 ～ 13.41%;the content of ketones is 0.17% ～ 3.0%;the content of phenolic is1.65%～17.87%.Besides the above substances,it also contains other volatile substances,with the content of 0.37%～5.51%.Combined with odor activity value and principal component analysis,it was found that the key volatile compounds in cold-pressed and hot-pressed Cyperus esculentus oil were trans-2,4-decadienal,2-n-pentylfuran,2-Undecen-1-al,nonanal,trans-2-decadienal,hexanal,heptanal and octanal.In addition,3-ethyl-2,5-dimethylpyrazine was only detected in hot-pressed Cyperus esculentus oil,and it was one of the key volatile compounds in hot-pressed Cyperus esculentus oil.Compared with the key volatile components of common aromatic oil peanut oil,it is found that the key volatile components in peanut oil are also aldehydes and pyrazines,but the content of pyrazines is slightly higher than that of aldehydes,which is opposite to that of Cyperus esculentus oil.(3)Two crude oil samples of Cyperus esculentus with different qualities were completely refined,and the refining process effect of Cyperus esculentus oil with different qualities and the influence of refining on the comprehensive quality of Cyperus esculentus oil were compared and analyzed.The results showed that although the acid value(KOH)of Cyperus esculentus crude oil was obviously different(2.03 mg/g and 12.21 mg/g,respectively),the acid value(KOH)and peroxide value(both 0.01 g/100 g)after refining were significantly better than LS/T 3259—2000.During the refining process,the fatty acid composition and content of Cyperus esculentus oil did not change obviously,but the triglyceride content in glyceride composition increased(from 98.46% and 97.68% to 98.74% and 98.06%respectively),but the change was not significant.The sterol content decreased from 220.21 and 253.44 mg/kg to 175.14 and 182.33mg/kg,respectively,and the loss rates were 20.47%and 28.06%,respectively.The polyphenol content decreased from 26.38 mg/kg and 88.65mg/kg to 8.45mg/kg,respectively,and was not detected.The vitamin content decreased from225.91 and 177.33 mg/kg to 180.01 and 13.09 mg/kg,respectively,and the loss rates were20.32% and 92.62%,respectively.The phospholipid content decreased from 6874.10 and312.29 mg/kg to 88.61 and 88.28 mg/kg respectively,and the removal rates were 98.71% and71.73% respectively.After refining,the quality indexes of Cyperus esculentus oil with different oil quality can meet the requirements of the industry,but the beneficial accompanying products of Cyperus esculentus oil with high acid value lose a lot in the refining process.(4)The phospholipids in different Cyperus esculentus oil were pretreated by direct injection of total fat and solid phase extraction of amino,High performance liquid chromatography-evaporative light scattering(HPLC-ELSD)and binary gradient elution were used to detect and analyze the composition of phospholipids,which provided data support for the subsequent research and development of Cyperus esculentus phospholipids.The results showed that the content of phospholipids in Cyperus esculentus oil was 0.46% and 1.25%respectively.Compared with the fatty acid of Cyperus esculentus oil,the palmitic acid content of the phospholipid increased obviously,from 12.39% to 22.53% and 14.55% to 21.40%.The oleic acid content decreased obviously,from 74.61% to 59.82% and from 71.63% to 58.59%.And the content of linoleic acid and linolenic acid increased from 8.85% to 14.62% and 9.58%to 16.10%,and the content of linolenic acid increased from 0.37% and 0.37% to 0.41% and0.47%.The phospholipid composition of Cyperus esculentus oil was detected and analyzed.It was found that the phospholipids in Cyperus esculentus oil were mainly composed of phosphatidylcholine(PC)and phosphatidylethanolamine(PE).Among them,PC content is the highest,with PC content in Cyperus esculentus oil being 0.24% and 1.13%,and PE content in Cyperus esculentus oil being 0.10% and 0.23%.The relative content of phospholipids is calculated by normalization method,and PE content in phospholipids is 2.64% and 21.79%.The content of phospholipid is 33.54% and 53.40%. |
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