The Comprehensive Utilization Of High Temperature Walnut Meal

High temperature walnut meal(HTWM), the by-product of walnut procession, is a kind of high quality plant protein resource due to its high crude protein content which is as high as 20-30%. This article focused on the processing and utilization of HTWM, including polyphenols extraction, proteins extraction and their optimization. Based on it, this paper also researched on anti- gout activity of polyphenols and walnut peptide milk formulation containing extracted proteins above. These theories and methods could provide guidance for the application of high temperature walnut meal.We chose ethanol as a solvent to get polyphenols from HTWM and then investigated on the effects of polyphenols extraction rate and xanthine oxidase(XOD) inhibitory activity through 4 factors, including ethanol concentration, solid- liquid ratio, extraction temperature and extraction time. By orthogonal experiments, we established the optimum extraction conditions: ethanol concentration was 80%, ratio of liquid to material was 20:1, extraction temperature was 80 ℃ and extraction time was 4 h. According to these conditions, the IC50 was of 0.2205 ± 0.0078 mg / m L, indicating a strong XO D inhibitory activity. The type of XOD inhibition for extract product was determined to be a mixed inhibition type in these further studies.After extracting polyphenols, we focused on protein in the remaining walnut meal. By using response surface analysis, the best protein extraction technology was found, containing that p H=11, extracted time=2 h, liquid to solid ratio=18: 1, extraction temperature=52 ℃, and walnut meal protein extraction rate was 64.52 ± 0.56% according to above condition.In order to highly hydrolysis extracted protein, several enzymes were used in the hydrolysis to test the protein recovery and ORAC value, including papain, pepsin, Flavourzyme, Alcalase2.4L, trypsin and complex protease. The result showed that trypsin was the best in this comparison. Further response surface methodology indicated the best process was enzyme substrates ratio=2.48%, liquid ratio=10.64:1, reaction time=14 h, reaction temperature=52.15 ℃. Under above conditions, the protein recovery and O RAC value of hydrolysates were 66.12 ± 0.71% and 1565μmol Trolox equivalent / g Peptide respectively.Besides, according to the optimized enzymatic condition, we prepared walnuts hydrolysate and its powder which would add to the walnut peptide milk. The solid- liquid ratio, skimmed milk powder, sugar and whipped were shown to be the important ones in walnut milk flavor by Plackett-Burman(PB) design analysis. The walnut milk flavor was further optimized by Response Surface Methodology(RSM) and the optimal formula for walnut milk was solid- liquid ratio=10.34%, skimmed milk powder=10.11%, sugar=9.31%, creamer=1.58%. Under the optimized recipe, sensory score was for 86.26.In order to maintain the system stability of walnut milk, different types of chelating agents and thickeners were added to walnut milk to reach the lowest value of precipitate rate. The result showed the best stability was adding 0.06% hexametaphosphate and 0.06% CMC(sodium carboxymethyl cellulose).