Studies On The Extraction Of Phenolic Compounds From Sesame Seed Meal And The Hydrolysis Of Sesame Protein By Subcritical Water

Sesame seed meal as a by-product of the processing sesame oil, contains high nutritional value which riches in a lot of protein(about 50%) and sesame lignan compounds. But now the utilization of sesame seed meal is very low and lack of added value. The method for extracting nutrients from sesame seed meal is mainly organic reagent extraction which not only inefficient but also the reagent is pollution and needed for recycling. Subcritical water as a new extraction method is not only possessing high extraction efficiency but also can avoid the harm of organic reagents. Meanwhile, the characteristic of high ion product makes it can be used as an acid-base catalyst for the hydrolysis of natural macromolecules. In this study, the extraction of phenolic compounds in sesame seed meal was studied and the extraction conditions was optimized. We determined the antioxidant activities of the extract and studied the hydrolysis of sesame protein by subcritical water.The protein content, total sugar content, ash content, fat content and water content in sesame seed meal were measured by national standards, which were 44.91±2.32 g/100g、11.54±0.00 g/100g、11.14±0.01 g/100g、6.78±0.33 g/100 g and 4.68±0.07 g/100 g. Through single factor experiments, the effect of material liquid ratio、extraction time and extraction temperature on the phenolic compounds in the extract was determined. The total phenolic yield was highest when the material liquid ratio was 2%(w/v) which was 28.85±0.28 mg/g, while the total flavonoids yield was highest at the ratio of 1% which was 2.43±0.06 mg/g. The total phenolic yield was at the peak in the extraction time of 20 min and the value was 27.13±0.19 mg/g, while the total flavonoids yield was at the peak in the extraction time of 15 min and the value was 2.93±0.02 mg/g. The total phenolic yield was highest when the extraction temperature was 220℃ and the value was 45.30±0.28 mg/g, while the total flavonoids yield was at the peak in the extraction temperature was 200℃ and the value was 3.96±0.14 mg/g. The sesamol yield was at the peak in the extraction temperature of 180℃ and the value was 0.20 mg/g. Optimize the orthogonal test of total phenols and flavonoids yield, the optimum extraction condition of total phenols yield is: extraction temperature 220℃、extraction time 15 min、materialsolvent ratio 1%, the optimum extraction condition of flavonoids yield is: extraction temperature 220℃、extraction time 5 min、material-solvent ratio 2%. The yield of total phenol and total flavonoids was quite low using ethanol and hot water to extract sesame seed meal.The result of the antioxidant activities of sesame seed meal extract by subcritical water extraction was: DPPH free radical scavenging ability and FRAP ferrous reduction ability was at the peak in extraction temperature of 220℃ and the value were 24.24±0.45 mg-VC/g-sample and 8.24±0.03 mmol/L, while hydroxyl radical scavenging ability was at the peak in extraction temperature of 200℃ and the value was 33.29±0.95 mg-VC/gsample. The DPPH free radical scavenging of extract by ethanol and hot water was quite low.The material liquid ratio、treatment time and treatment temperature influence the degree of protein hydrolysis. The protein yield was highest when the material liquid ratio was 1%(w/v) which was 62.01±0.17 mg/g, while the degree hydrolysis was highest at the ratio of 2% which was 2.29±0.06%. The protein yield was at the peak in the treatment time of 10 min which was 38.11±0.54 mg/g while the hydrolysis degree was highest at the time of 25 which was 5.46±0.12%. The protein yield was at the peak in the treatment temperature of 180℃ and the value was 32.51±0.40 mg/g. The degree hydrolysis was highest in the treatment temperature of 220 ℃ and the value was 7.65±0.04%. By determining the molecular weight of the extract by gel filtration chromatography, the large molecules gradually break down into small molecules with the increase of the temperature; By determining the molecular weight of the protein by tricine-SDS-PAGE, the molecular weight of the protein gradually increased in the range of 120℃~160℃ while the molecular weight decreased in the range of 180 ℃ ~220 ℃.To study the influence of temperature on the contents of free amino acids in the extract, for the study of 17 kinds of amino acids, except lysine was not detected, other amino acids were detected. At the same time, we anlysis the amino acid sequence of the protein hydrolyzed peptide using MALDI-TOF/TOF and the sequence of the sesame small peptide was obtained.