Study On The Preparation Of Tea Seed Cake Protein And Its Functional And Digestion And Absorption Properties

Tea seed is the fruit of the Camellia plant of the Camellia family.The annual tea seed resource in China was about 1 million tons,which was mainly used for the extraction of edible oil.Although the usages of TSC as fertilizer,animal feed,fuel and tea saponin extraction have been reported,most of TSC was discarded as waste.Tea seed cake contains 10-13%protein,which is a high-quality protein source.As for TSC protein,previous researches have reported the optimization of the extraction process,however,there was little study focus on its functional structure.Therefore,it is of great significance to make the research on the functional and structural properties of TSC protein deeply with high added value.In this study,cold-pressed TSC was used as raw material to study the extraction method,structural and functional properties of tea seed cake protein.The main conclusions were as follows:(1)Clarify the extraction method of TSC protein.In the early stage of the experiment,the tea saponin in the TSC protein was removed from 15%to 0.078%.Then,the crude protein(TSCP)was extracted by alkali-dissolving and acid-precipitation method,which showed the optimal extraction process conditions were as follows:material-to-liquid ratio of 1:25,pH 10.5,temperature of 50?,and 75 min,the protein extraction rate was 81.60 ± 1.21%,the purity was 83.05 ± 0.98%.On the basis of alkaline extraction,the ultrafiltration membrane method was used to classify TSCP,and three components of>10 kDa(TSCP-1),3.5-10 kDa(TSCP-2)and<3.5 kDa(TSCP-3)were obtained,which respectively accounted for 56.57 ± 2.02%?9.42 ± 0.89%and 26.91 ± 1.26%of the crude protein,the purity was 88.23 ±2.07%,86.75 ± 1.06%and 84.79 ± 1.55%.The size exclusion chromatography(GPC)indicated that the molecular weights of TSCP-1 were concentrated in 506.95 kDa,97.80 kDa,49.24 kDa and 16.11 kDa,all of which were larger than 10 kDa.The molecular weight of TSCP-2 is concentrated 10 kDa and 3.50 kDa,and that of TSCP-3 was mainly concentrated in 3 kDa and 1 kDa.(2)Study on the physical and chemical properties of TSC protein.TSCP and the three components of ultrafiltration were used as raw materials,and compared with SPI.According to the results of amino acid composition analysis,it is found that there are 18 kinds of amino acids in TSC protein,and the variety was complete,and TSC protein is rich in Lys and Met.The results indicated that the thermal stability of SPI was better than TSC protein.The thermal stability from high to low was TSCP-1,TSCP-2,TSCP-3 and TSCP.TSCP-1 had good thermal stability(88.17?)and the smallest particle size.(3)Study on the structural properties of TSC protein.TSCP and the three components of ultrafiltration were used as raw materials,compared with SPI.The results of circular dichroism showed that the sum of ?-helix and ?-sheet content of TSC protein was greater than that of SPI,and TSCP-1 was the highest,which indicated that its protein structure was more orderly.The aromatic amino acids of TSCP-1 and TSCP-2 were less affected by pH(4)Study on the functional properties of TSC protein.TSCP and the three components of ultrafiltration were used as raw materials,compared with SPI.TSCP had the highest solubility,followed by TSCP-2,TSCP-1,TSCP-3 and SPI.SPI had the strongest water holding capacity(4.69±0.12 g/g),followed by TSCP-2(3.76 ± 0.17 g/g),and the TSCP-3 was the lowest(2.75 ± 0.07 g/g).TSCP-1 had the highest fat binding capacity(4.26 ± 0.12 g/g).TSCP had the strongest foaming ability.TSCP-1,TSCP-2 and TSCP-3 had lower foaming capacity,but had higher foam stability.TSCP and TSCP-2 had excellent emulsification ability.TSC protein had high LGC and poor gel forming ability.The apparent viscosity of TSC protein decreases with the increase of shear rate,which indicated that all samples had shear thinning or pseudoplastic behavior,which was much higher than SPI(5)Digestion and absorption in vitro of TSC protein.TSCP extracted by alkaline method and the three components of ultrafiltration were used as raw materials,compared with SPI.The results of simulated gastrointestinal digestion showed that TSCP had the highest degree of hydrolysis in the two digestive stages of the gastrointestinal tract.After digestion,the degree of hydrolysis reached 80.98%,while TSCP-3 had the lowest degree of hydrolysis in the two digestive stages of the gastrointestinal tract.After digestion,the degree of hydrolysis is only 26.82%.According to the result of degree of hydrolysis,the intestine was the main digestion site.In the pepsin digestion stage,the different components of TSC protein and SPI were hydrolyzed to a small extent.The trypsin digestion stage was mainly hydrolyzed from large molecular weight proteins into smaller molecular weight<1 kDa proteins.The results of the rat inverted small intestine absorption test showed that the jejunum is the main absorption intestine,followed by the ileum and duodenum.The absorption rate of protein digestion products in the jejunum from high to low is:SPI>TSCP-2>TSCP-1>TSCP-3>TSCP.SPI had the highest jejunal absorption rate of 9.73%,and TSCP had the lowest jejunal absorption rate of 5.12%.