| Flax(Linum usitatissimum L.)is a common oil crop,and its planting area in China,second only to peanuts,rapeseed and soybeans.Flaxseed oil is rich in linolenic acid,and it also contains lipid concomitants those are beneficial to the human body such as cyclolinopeptides(CLs),phytosterols,squalene,and tocopherols.Among them,CLs are a class of hydrophobic cyclic peptides commonly found in flaxseed oil,composed of eight to nine amino acids,and have biological activities such as immunosuppression,anti-cancer,and anti-inflammatory.At present,the extraction methods of flaxseed oil were mainly cold pressing,hot pressing,aqueous enzymatic method and solvent extraction method.So which oil extraction method was suitable for flaxseed oil processing? After moderate refining,photosensitive pigments,phospholipid micelles,free fatty acids and other components could be removed,and the appearance,color and storage stability of products could be improved.However,what was the effect of refining on CLs?To fully develop flaxseed oil and improve the nutritional value of flaxseed oil,this project used different extraction methods to compare the nutritional components of flaxseed oil,and the changes of CLs in the refining process of flaxseed oil were investigated,playing a guiding role in flaxssed oil processing.According to the loss of CLs in the refining process,CLs were extracted from flax waste clay,and a flaxseed oil rich in CLs was developed through backfilling,and the digestion and absorption of flax CLs in vivo and in vitro were explored..The main findings were as follows:1.The effects of solvent extraction,hot pressing,cold pressing and aqueous enzymatic extraction on the quality of flaxseed oil were compared and analyzed.The results showed that the total content of CLs in the pressed oil(cold-pressed oil,504.04μg/g oil;hot-pressed oil,631.41 μg/g oil)was almost twice that of solvent-extracted oil and aqueous enzymatically extracted oil,cold-pressed flaxseed oil The content ofγ-tocopherol was higher(46.51 mg/100 g oil),but the oil yield of cold pressing flaxseed oil was only 22.2%,which was lower than that of aqueous enzymatic method,which is 30.3%.The phytosterol content of 347.56 mg/100 g oil was higher than that of pressed oil.Overall,cold-pressed flaxseed oil and aqueous enzymatic flaxseed oil both were light yellow,and had high content of squalene,but a low content of phospholipids,that could be consumed without refining.In conclusion,cold-pressed flaxseed oil could be served as a good source of CLs,while aqueous enzymatic extraction of flaxseed oil could retain more lipid concomitants and had a high oil yield.2.The effects of flaxseed oil refining(degumming,deacidification,decolorization,deodorization)on CLs were explored,and a rapid method of extracting CLs from flaxseed oil spent bleaching earth(FOSBE)was found.The results showed that after degumming,the contents of various CLs were lost to different degrees.With the increase of phosphoric acid concentration,the loss of total CLs increased,and CLs were detected in the degummed phospholipid micelles.Different concentrations and different types of alkali treatments would cause the loss of CLs.The more alkali added,the higher the loss rate of CLs,and the stronger the alkalinity,the higher the loss rate of CLs.After decolorization,the color of flaxseed oil became lighter,and decolorization had a greater impact on the removal of CLs.The longer the decolorization time was,the higher the loss rate of CLs.When decolorization was lasted for 50 minutes,the CLs had not been detected.The deodorization process also had an effect on CLs,and the removal rate of CLs decreased with the increase of deodorization temperature.CLs were extracted from the refined FOSBE through different solvents.In the single solvent extraction screening,anhydrous methanol and 95% ethanol had the highest extraction amounts of CLs from FOSBE,which were 2205.3 μg/g and 2203.96 μg/g,in the mixed group solvent extraction,the total amount of CLs extracted by n-hexane-95% ethanol was2929.98 μg/g.All in all,CLs were lost in oil refining,and FOSBE was a good source of CLs.3.Moderate precision processing was adopted to obtain CLs-rich flaxseed oil that met the national refined oil standard.The results of orthogonal optimization experiments showed that the degumming rate of flaxseed oil was 78.84%,and the retention rate of CLs was 74.91% according to the following condition,the amount of water added was 2%(w/w),the degumming temperature was 50 ℃,and the degumming time was lasted for 90 min.In the moderate decolorization experiment,the ratio of activated clay and activated carbon was 10:1,the addition amount was 0.5%(w/w),the decolorization temperature was 75 °C,and the decolorization time was 15 min.The degumming rate of flaxseed oil was 29.87%,and the CLs retention rate was89.6%.Finally,Matlab was used to evaluate the similarity.CLB,CL(A+P),and CLO were viewed as the main components of CLs,and the lost CLs in refining were added back.The final flaxseed oil product also met the national standard.This moderately refined flaxseed oil rich in CLs conformed to the concept of "precise and moderate processing of edible oils".4.The digestion and absorption characteristics of CLs through in vitro and in vivo experiments were conducted.Fistly,the simulated gastrointestinal digestion results in vitro showed that CLs were not hydrolyzed by pepsin and trypsin,and existed stably in the gastrointestinal tract,and in vitro Caco-2 cell absorption experiments showed that CLs were absorbed by Caco-2 cells.The content of CLs were detected at 6 h,12 h,and 24 h,the result showed that CLB and CL(A+P)were mainly detected,and the total absorption rates of CLs were 0.92%,1.94%,and 5.41%,respectively.The results of the in vivo rat absorption experiment found that the fragment ion peaks of CLs were not detected by LC-QTOF-MS in the blood of rats at0.5 h,1.5 h,3 h,and 6h,and in the liver of rats after gavage for 6h.CLs were also not detected.In a word,because the cyclic structure of CLs had a certain conformational constraint,their conformation had a certain stability relative to the linear peptide,so they were not hydrolyzed by proteases,and they might interacted with some carriers in vivo,such as apolipoprotein,so the extraction method of CLs in blood must be improved. |
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