Studies On Simultaneous Aqueous Extraction Of Peanut Oil And Protein

Aqueous extraction (AE) and enzymatic alkali extraction (EAE) processes suitable for peanut were studied. AE is a process which can simultaneously extract oil and natural protein from oil seeds. EAE which was founded on the basis of AE, can increase the oil yield by the hydrolysis of enzyme added in the aqueous phase.First, influences of milling-pretreatment on EAE of peanut oil and protein were firstly investigated. The average volume particle size of peanuts could be 28μm with minitype hammer mill, and the value was stable while being further milled. The oil and protein would increase when being moderately milled. When the particle size reached 28μm, further milling would result in the increasing of the emulsion stability, and lead to the reduction of oil and protein. Then, extraction efficiencies of peanut oil and protein, and protein productions'qualities of AE and EAE were compaired.The free oil yields were close which getted by AE (87.3%) and three different EAE(Alcalase EAE,Alcalase-Flavorzyme EAE,Flavorzyme EAE) processes (87%-89%) combined to the freeze-thaw demulsification approache. Emulsification during AE process was prominent, while the hydrolysis by enzymes could reduse the quantity of emusion during AE.The protein yield of AE was 90.6%, while the yields of EAE were less than 80%. Protein hydrolyzates by Alcalase EAE were strongly bitter while the protein prodution by AE was acceptable. The hydrolysis of flavorzyme (2.8% E/S, at suitable pH and temperature for 4 h) could wipe out the bitter, while it would increase the economic and time cost.The contents of main compositions were basically the same, and the protein contents were 68%. When pH value was higher than isoelectric point, the dissolubility of AE protein production was excellent which could be higher than 98%, and it's higher than Flavorzyme-EAE. The emulsibility, emulsion stability, foamability, water and oil binding capacity of AE protein production were far higher than Flavorzyme-EAE.Finally, solution was designed according to the merits and demerits of AE and EAE which was summarized from the studies above. AE was selected to be the main line of a process which could get 90% peanut protein and part of free oil, as the emulsion formed during AE process would be broken by the enzyme to release more free oil. And it was called"Enzyme assisted aqueous extraction (EAAE)". EAAE process was founded. Conditions of EAAE's two steps were optimized. The optimum conditions of first step were: solid-liquid ratio 1:5, 55℃, initial pH 9.0, after whipping for 30min, adjust pH to 9.0 again; after whipping for 5 h, 67% free oil could be got by centrifuge. The optimum conditions of enzymatic demulsification process were: solid-liquid ratio 1:5, 60℃, add 9000u/g Papain; after whipping for 4 h at natural pH, partical oil could be got by centrifuge. At the optimized conditions ,the free oil yield could be 88.5%. By HPLC, it was found that the proportion of high molecular weight protein consisted in the emulsion formed in AE was larger than that in emulsion treated by EDA or FDA. So, the main target of EDA or FDA was high molecular weight interface proteins of the emulsion.Compaired to the traditional squeezing and process, EAAE prosess is simpler, safe, solvent pollution-free, and can get the protein of higher quality. And compaired to the general enzymatic aqueous extraction (EAE), the amount of enzyme used in process is quite fewer, and its production of protein is more suitable for the extensive use in food industry. The enzymatic demulsification process is easy to operate and control the conditions, and also it costs less.