Effects Of Aspergillus Oryzae Fermentation On Physicochemical Properties And Antioxidant Activity Of Sesame Meal

Sesame(Sesame,Sesamum indicum L.)is one of the four major oil crops in China.Sesame meal is a by-product of sesame press oil.It contains about 5%crude fat,20%carbohydrate,45%protein,1.5%potassium,3%phosphorus and other mineral elements.At present,sesame meal has not been deeply utilized and exploited,which is a serious waste of sesame high-quality protein resources.Therefore,the sesame meal,which is the by-product of sesame oil processing,is used as the experimental raw material.After a series of different processing methods,we hope to find an effective and in-depth development method of sesame meal resources,which makes the addition of sesame meal products worthy of improvement and has broad application prospects and important practical significance.Based on the deep development and utilization of sesame meal,the sesame meal was fermented by pure Aspergillus oryzae NCUF414 in solid state,and the changes of main physical and chemical indexes,antioxidant properties and volatile flavor substances in the fermentation process were analyzed and compared,so as to provide theoretical basis for the development of high value-added sesame fermentation products.The main conclusions are as follows:(1)Taking Aspergillus oryzae NCUF414 preserved in laboratory as an evaluation index,the factors such as salt addition,fermentation time,fermentation temperature and material-liquid ratio were optimized.The optimum technological conditions for producing high content amino acid nitrogen paste from pure Aspergillus oryzae Fermented sesame meal were obtained as follows:fermentation temperature was 29?,fermentation time was 12 days,material-liquid ratio was 1:0.7.Under these conditions,the content of amino acid nitrogen in sesame meal sauce was 1.5328 g/100 g.The fermentation time is greatly shortened.(2)During the solid-state fermentation of sesame meal by Aspergillus oryzae,the ash content of the system increased slightly,reaching 10.720 g/100 g.The contents of crude fat and reducing sugar decreased.The final contents were 0.727 g/100 g and 0.736 g/100 g.The total acid content,protein content,free amino acid content and amino acid nitrogen content gradually increased to 0.0675 g/100 g?44.465 g/100 g?74.546 mg/g and 1.5328 g/100 g,the content of polypeptide and the activity of acidic protease increased first and then decreased.The final content was 16.936 g/100 g and 579.003 U/100 g,respectively.The spore number of Aspergillus oryzae increased to 8.42×109/g.5-hydroxymethyl furfural was producGd during fermentation.With the prolongation of fermentation time,the content of lignans in sesame meal increased gradually.The highest levels of sesamin,sesamolin and sesamol were 202.05±2.51 ?g/g?192.17±4.5?g/g?85.04±11.83 ?g/g.The texture parameters of fermented sesame meal sauce showed that with the extension of fermentation time,the hardness and adhesiveness of the sauce increased first and then decreased,the adhesion of sauce continued to increase.The sauce was suitable for stickiness.(3)The aroma of sesame meal sauce is due to its various volatile components.The aroma of sesame meal sauce is not a single compound,but a synergistic effect of multiple volatile components in quantity.A total of 94 volatile compounds were identified by GC-MS analysis in different fermentation stages.Among them,5 ketones,5 acids,8 esters,2 sulfur-containing heterocycles,5 oxygen-containing heterocycles,25 olefins and their derivatives,4 phenolic ethers,10 aldehydes,15 alcohols and 15 nitrogen-containing heterocycles were detected.With the prolongation of fermentation time,more kinds of volatile components were found in the reaction system.Esters were not detected before(0 d)fermentation,and 3-4 new esters could be formed during the fermentation process.The number of aldehydes,ketones,phenols,sulfur-containing heterocycles,oxygen-containing heterocycles and nitrogen-containing heterocycles increased from one(0 d)to four(12 d),and hydrocarbons and their derivatives remained at a high level,with the lowest 12(6 d)reaching 17(2 d,10 d,12 d).Alcohols increased to 9(12 d)from 4(0 d)before fermentation.(4)DPPH radical scavenging rate,ABTS+free radical scavenging capacity and FRAP iron reduction capacity showed a gradual upward trend,the highest reached 49.46±0.19%?1135.27±3.06?TE/g?106.87±1.77mgFeSO4/100g,indicating that Aspergillus oryzae Fermented sesame meal sauce had excellent antioxidant properties.