| Peanut is one of the main oilseed-crops in China. For by-product after extract peanutoil, peanut cake was used as feeds, but its value for resources hasn't been fully utilized inthe past. The protein and oil in cold press peanut cake is main components. A treatingtechnique, enzymatic hydrolysis method, is developed and used to isolate peanut proteinand oil from cold press peanut cake at the same time. All the basic characteristics in thecourse of peanut cold-pressing, physical and chemical properties of product, preparationand purification of polypeptides, the processing technology and properties of peanutsuperfine powder were studied, results are as follows:1. Study on synchronous extracting peanut protein and peanut oilfrom cold pressed peanut cake by aqueous enzymatic hydrolysis1.1 Study on the basic characteristics of cold-pressing process of peanutDuring the processes of cold pressing on the whole peanut kernels and the brokenones, many relative factors, such as oil yielding pressure, oil yielding strain, and oilyielding efficiency, stress-strain relations and actual compress ratio, etc., were studied.Two empirical formulas were set up to express the relations between oil yieldingefficiency and pressure, stress and strain etc. And the theoretical model for calculatingactual compress ratio has also been brought forward.1.2 Synchronous extraction of protein and peanut oil from cold-pressedpeanut cakes by aqueous enzymatic hydrolysisIn this study, the aqueous enzymatic technique was applied to obtain both the peanut protein and the peanut oil from cold pressed cake at the same time. The cold-pressedpeanut cake was ground with water to get a peanut mash. Adjusted the pH value of thedispersed phase, it was hydrolyzed enzymatically by neutral protease and isolated bycentrifugation, emulsified oil and protein were obtained. Then emulsified oil was furtherseparated through demulsification and got peanut oil. The enzymatic hydrolysis test assingle factor, i.e, pH, temperature, duration time and applied amount of protease, wasconducted. To obtain the optimum conditions of the hydrolysis with neutral protease, amethod as response value by hydrolysis degree was adopted to conduct response surfaceanalysis. The results showed that optimum conditions were as follows: applied weight ofenzyme, 6500u/g, hydrolysis time,2.5 h, temperature, 50℃and pH, 6.7. Theproduction temperature of cold-pressed peanut cake is≤60℃, with the product of≥55% protein content and 0.27% residual oil content.And the purityof protein hydrolysateis 89.94%, and the result rate of protein, 48.85%.1.3 Study on the physical and chemical properties of peanut proteinhydrolysatesFunctional properties of peanut protein hydrolysates and alkaline extracted proteinhave been studied in this paper. The functional properties of peanut protein hydrolysatehas improved dramatically compare with the alkaline extracted protein, its emulsifyingability increased by 11.1%; emulsive stability,by 37.3 %; water-holding capacity, by34.0%; oil sorption , by 0.039(g/g) and foaming ability , by1.324(g/g), therefore, peanutprotein hydrolysate is very suited to the needs of meat products and dairy processing.But foaming stability of peanut protein hydrolysates is slightly weaker than one ofalkaline extracted protein and dropped by 4.6%. This is probably that the low viscosity ofpeanut protein hydrolysates reduced the intensity of liquid membrane, so that the foamingstability of peanut protein hydrolysate was down.1.4 Analysis of properties of peanut oil extracted by aqueous enzymaticmethod By comparing and the components of fatty acid and it's the physical and chemicalproperties, it is found that the peanut oil made by aqueous enzymatic is almost the samewith ones by aqueous extraction peanut oil and/or cold-pressed peanut oil. The qualitiesof these products measure up to the national standards GB 1534-2003. The quality ofpeanut oil is better, and the oil yielding efficiency. This method could avoid theassociation with other organic solvents, to guarantee the edible security of peanut oil.2. Preparation and purification of peanut polypeptidesIn this study, neutral protease AS1.398 was used to enzymatically hydrolyze peanutprotein to produce polypeptides. The choice of factors, such as enzyme preparations andthe process parameters were studied as a systimaematic works. The optimum extractingcondition was attained by orthogonal experiments,i.e., pH, 7.0; temperature, 42℃;dosage of enzyme action (enzyme/substrate), 6500u/g;treatment time, 8h and ratio ofraw material to solvent, 1:8 (w/v).Polypeptide was extracted from peanut peptides and then isolated by ultrafiltration with5kd of hollow fiber to collect fractions (≤5kd), and then 2 active peaks were obtained byglucan gel chromatographic. The purity of them were identified by urea-containingSDS-PAGE gel electrophoresis, molecular weights were 6.5KD and 2KD respectively.Use the ultrafiltration to collect fractions(≤3kd), 1 active peaks were obtained byglucan gel chromatographic, molecular weights was 2KD.In order to understand the primary structure of polypeptides, technique of pre-columnderivatization was used for amino acids analysis.3. Properties of peanut superfine powder and its processingtechnologyPeanut superfine powder from cold-pressed peanut cake have more changes inproperties due to their granules were fine, therefore Peanut superfine powders have goodwhiteness and pasting property. The granules of peanut raw powder are mostly existedmore than 100 meshes, at same time, these granules are also greater than the standard flour (120 meshes), while peanut superfine powder (＜140 meshes) is smaller than thelatter. Due to friction angle(56.7°) of superfine powder is great therefore peanutsuperfine powder is poor in mobility,. Analysis of the pasting property of peanutsuperfine powder shows that the gelatinizing temperature is lower than common peanutpowder, with complete gelatinization and slow retragradation. So peanut superfinepowder from cold-pressed peanut cake can be used to replace wheat flour to preparevarious foods.
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