Study On The Seeds Proteins And Aqueous Extracts Of Cake From Torreya Grandis

Torreya grandis seeds can be regarded as high-quality resources due to their abundant protein content and a great number of fatty acids.As the increasing yield of T.grandis seeds,chal enges of the industrial application of these seeds have emerged.However,there are few reports on the research of seeds protein and the utilization of cakes after cold pressed process as well as the components differences between varieties of T.grandis.In order to utilize them effectively,it is necessary to understand the composition,characteristics and possible application of proteins and cakes from T.grandis seeds.Based on these,this paper has focused on the physicochemical and functional properties of seeds proteins,the nutritional values of T.grandis cakes and the antioxidant activities of aqueous extracts from different cakes,aiming to provide theoretical basis for the industrial application of the protein and extracts from T.grandis seeds.The main contents were as follows.Firstly,the compositions of the Dazinai seeds proteins were studied according to the method of Osborne protein classification and the method of extracting proteins was determined.The results showed that albumin was the main component of these proteins,which accounted for more than 90% of the total protein extracts.In addition,the proportions of globulin,glutelin and prolamin were less than 5%.It`s economically feasible to extract the protein by using the aqueous solution.Further studies of these proteins indicated that the molecular weights of albumin(31~37 kDa,20~21 kDa and 10 kDa),globulin(30~37 kDa,29 kDa and 20~21 kDa)and glutelin(30~37 kDa and 10 kDa)were different.The protein fraction A of 30~37 kDa from albumin was prepared well and it indicated that fraction A consisted of at least nine different peptide fragments by analyzing the mass spectrum.And peptide fragments with the sequences could effectively match six proteins from Taxaceae.In the secondary structure of protein fraction A,the ?-helix content was 45.26% and the sum of ?-helix and ?-sheet was 61.68%,indicating the proportion of ordered structure in fraction A was high as well.Furthermore,the compositions and physicochemical properties of four proteins were studied in detail.The results showed that there were differences in the properties of the proteins between the different T.grandis cultivars.Overall,all the protein extracts had rich essential amino acid with about 41.06% and the first limiting amino acid was tryptophan.The molecular weights of protein extracts were mostly about 30~37 kDa and 20~21 kDa.Proteins displayed excel ent thermal properties with the denaturation temperature of about 91.50°C and the enthalpy exceeding 9.20 J/g.The surface hydrophobicity values of proteins were general y higher than 540 and the ?-potential ranged from 25 to-10 mV at the different conditions of pH 2.2~8.0.In addition,the differences of cultivars were that there was a protein fraction of about 10 kDa in Dazinai protein and two fractions with similar molecular weights of 20~21 kDa in Panan protein,the denaturation temperatures of Shengzhou 1 and Dazinai protein were up to 93.60°C and the surface hydrophobicity of Dazinai protein(982)was the highest.Meanwhile,the functional properties of four protein extracts were studied.The results demonstrated that the functional properties were related with the T.grandis cultivars.The solubility values of Shengzhou 1 and Dazinai proteins were 90%,higher than that of Huangshan and Panan protein(about 80%)at weakly acidic/alkaline and neutral conditions.Emulsifying activitives of Shengzhou 1(44.6 m~2/g)and Dazinai protein(43.6 m~2/g)were excel ent and comparable to soybean protein(44.0 m~2/g),followed by Panan proteins(42.0 m~2/g)while Huangshan protein had the lowest performance(36.1 m~2/g).The foaming capacities of T.grandis proteins were as follows: the foaming ability of Dazinai and Panan proteins were about 15% while that of Huangshan and Shengzhou 1 protein were 20% and 25%,respectively.They were all lower than the foaming ability of soybean protein(30%).However,the foaming stability values of Shengzhou 1 and soybean protein were about 75%,higher than those of the other three proteins(about 60%).Although their in-vitro digestibilities were slightly low(55~60%),protein extracts had good oil holding capacity of approximate 3 g/g which were higher than that of soybean protein(2.5 g/g).Finally,the preliminary study on the utilization of cold pressed cakes was carried out.The results showed although there was a certain content of proteins(16.47~26.24%),the extraction rate of cake proteins was less than 8%,which reduced the utilization of proteins.Then,nutritional values and antioxidant activity of aqueous extracts of the cakes were explored.The results indicated that the constituent contents of all extracts were different,but they contained high contents of phenolics and polysaccharide(3.17~5.61% and 23.74~32.38%,respectively)as well as mineral elements,such as K(52.7×103~79.2×103 mg/kg),Mg(8.4×103~13.2×103 mg/kg)and Ca(732.2~935.1 mg/kg).All aqueous extracts exhibited favourable antioxidant abilities for their antioxidant capacities were approximate 60.0 mmol Trolox equivalent/100 g,the inhibition rates on ABTS·+ cationic radicals rose to about 80% and the levels of Fe3+-Fe2+ reducing activity could be up to 0.450 at the concentration of 3.5 mg/mL.In conclusion,proteins from different T.grandis cultivars exhibited high essential amino acid contents,excel ent thermal property and solubility.Dazinai displayed advantageous emulsifying and Shengzhou 1 showed excel ent emulsifying and foaming abilities,indicating that these two seeds proteins could be used in the food industry.Varieties of cakes aqueous extracts with good antioxidant abilities and nutritional components,had potential to be used in beverages and food system to provide special taste and better nutrients.