| Flaxseed,one of the oldest oil crop,has attracted much attention because of its rich nutrients.Whole flaxseed contains fat(30%-41%),dietary fibre,aminophenol,peptides and other ingredients.Flaxseed oil is an excellent source of α-linolenic acid with typical levels of55% in the oil.Studies have shown that α-linolenic acid has a positive role in reducing the risk of heart disease and cardiovascular disease.Sesame paste is very popular among consumers because of its unique aroma of roasted sesame and roast.Its unsaturated fatty acids are mainly oleic acid and linoleic acid,but the content of linolenic acid is very low.This study is devoted to the development of a new type of sesame paste with higher α-linolenic acid content and consumer preference.Firstly,we estimated the effect of microwave and conventional oven heating on the quality of flaxseeds.Secondly,effect of addition of flaxseed flour on quality(basic components,lipid,protein,the volatile compounds and consumer acceptance)and storage stability(lipids,volatile aldehyde,ketone compounds)of sesame paste were studied.Finally,the changes of the nutrients in the flaxseed-sesame paste during digestion were analyzed by simulating the digestive system in vitro.The main research contents and results are as follows:(1)This study was to evaluate the effects of microwave and conventional oven heating on the amount of hydrogen cyanide,oil and protein properties,and volatile compounds of flaxseed.All the heating treatments effectively reduced the contents of hydrogen cyanide.Notably,oven heating at 150 °C for 30 min increased the peroxide value by more than 10 folds,while microwave heating at 860 W for 8 min only caused slight increase at the similar color.In addition,SDS-PAGE showed that the oven heating at 150 °C caused a more prominent decrease in the intensity of the 40-60 k Da and 22.0-30.0 k Da bands than microwave heating at 860 W.Furthermore,both oven heating at 150 °C and microwave heating at 860 W remarkably increased the kinds and amounts of the volatiles,such as pyrazines,alkanes,aldehydes,which could be due to Maillard reaction and lipid oxidation.Based on above analysis index,principal component analysis(PCA)was performed to further analysis comprehensive quality of flaxseeds,indicating microwave heating(860 W for 8 min)and oven heating(150 °C for 30 min)of flaxseeds showed similar properties.Collectively,the results indicated the feasibility of microwave treatment as an alternative to the conventional oven heating to process the flaxseeds.(2)The addition of flaxseed was evaluated in terms of their effects on the fatty acid profile,rheological characteristics,texture,the volatile profile and sensory perception of sesame paste.With the increase in the amount of flaxseed,the α-linolenic acid content of the sesame paste increased significantly.When the addition amount was 20 g/100 g,the α-linolenic acid content was 10.49%,which was significantly higher than that of sesame paste(0.28%).The addition of flaxseed did not change the characteristics of the pseudoplastic fluid of sesame paste,but the viscosity increased at the same shear rate.The addition of flaxseed will increase the hardness,cohesion and viscosity of sesame paste.Wi th the increase in the amount of flaxseed,the content of pyrazine,aldehyde,alkane,alcohol,and pyrrole compounds in the sample increased significantly.The results of the sensory evaluation of sesame paste using principal component analysis found that the samples with 5 g/100 g and 10 g/100 g of flaxseed were similar in aroma to sesame paste,with a strong flavor of fried nuts,oils,fried sesame and smear sex.The sample with 20 g/100 g of flaxseed has a slightly more pleasant burnt aroma than sesame paste.Fishy and grassy flavors are distributed in flaxseed paste.Sensory evaluation acceptance test results show that when the addition amount of flaxseed is 5 g/100 g,10 g/100 g,and 20 g/100 g,the acceptance of the sample is directly similar that of sesame paste,but the addition amount of flaxseed is 40 g/100 g is lower than that of sesame paste.(3)This study reports the effects of addition of flaxseed on the lipid oxidation,quality of aldehyde and ketones of sesame paste during storage.Studies have shown that the addition of flaxseed increases lipid oxidation during the storage of compound sesame paste,which is mainly manifested by higher acid value and malondialdehyde content.The content of volatile aldehydes and ketones produced by lipid oxidation increased significantly with the increase of storage time and the addition of flaxseed.Using cluster analysis,it is found that when the amount of flaxseed is 5 g/100 g and 10 g/100 g within 60 days of storage,the lipid oxidation degree and the content of volatile aldehydes and ketones of the samples are close to those of sesame paste;When the addition amount of flaxseed was 20 g/100 g,the overall quality of the sample was slightly lower than that of sesame paste,but it was significantly higher than the quality of the sample with the addition amount of flaxseed 40 g/100 g.(4)The changes of lipid,protein,polyphenolic compounds and antioxidant activity of the complex flaxseed tahini during simulated digestion were studied.The results showed that the contents of free fatty acids,small molecular peptides and free amino acids increased gradually with digestion.The confocal laser scanning microscopy(LSCM)showed that the lumps of protein indicated by the oil droplets gradually disintegrated and dissolved in water,and the particle size of the oil droplets gradually increased.The polyphenols were gradually released and the content of water-soluble polyphenols was significantly higher than that of fat-soluble polyphenols.The gradual dissolution of nutrients in the digestive juice results in a significant change in the antioxidant properties of the digestive juice.Based on the comprehensive analysis,the compound flaxseed-tahini has potential higher nutritional value. |
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