Study On The Changes Of Nutritional Value During Solid State Fermentation For Almond Skin

Almond skin is red or brown seed coat of almond. Almond skin has rich nutrition, which has become the food ingredients or animal feedstuff.Plant Polyphenols are important composition in almond skin. The existence of amygdalin in almond skin is the source of bitterness and toxicity.That limited the usage of almond skin as a feedstuff.In this paper, the safety indicator amygdalin was determined in almond skin, and detoxification process research was followed. The study of extraction of almond skin polyphenol and its biological activity were discussed. Since the use of solid state fermentation technology to produce the almond skin protein fermentation feed, the kinetics and interrelation between the nutritive compositions were established. The semi-in vivo method (ruminal degradability experiment) for almond skin and its fermentation products were studied for evaluating its nutrition. The main results were as follows:1)With Ultraviolet spectrometry, the maximum absorption wavelength was determined at219run, and the calibration curve was linear in a certain range (r2=0.9992). With the standard of amygdalin solution as reference, amygdalin contents in samples were measured. Based on this method, the single factors and orthogonal optimization were used for the detoxification of soaking. The results were as follows:0.1%citric acid soaking reagent,8hours for smoking,70℃soaking temperature, the rate of solid to liquid1:15(g/ml), the rate of detoxification was76%.2)Th technology e optimization of extraction of almond skin polyphenol, and its antibacterial and anti-oxidative capacity for almond skin polyphenol were also studied.The results shows:the optimum conditions for total polyphenol extraction from almond skin were:twice ultrasonic treatments,20min ultrasonic period, the ratio of solid to liquid as1:15and60%ethanol solution were the optimum conditions.After optimization,the polyphenol extract amount was30.24mg GAE/g. The antibacterial capacity sequence of three pathogenic bacteria was E.coli> S. aureus>S. typhmurium. The almond skin polyphenol had the free radical scavenging activity for DPPH and ABTS, the IC50were27.778μg GAE/ml,84.964μg GAE/ml separately.3) The solid state fermentation of almond skin was processed with complex bacteria(Aspergillus niger, Saccharomy cescerevisiae and Bacillus subtilis). The results were:the true protein content was highest when the ratio of three strains was2:1:1. The most optimal components of fermentation substrates were almond skin10g, bran1.5g, urea0.2g, ammonia sulfate0.2g, mono-potassium phosphate0.1g, magnesium sulfate0.01g. The optimized fermentation conditions of almond skin were:Fermentation temperature30℃; the ratio of material to liquid1:1.6(w/v); inoculums volume13%; fermentation period4days.During the process of solid state fermentation, the contents of biomass and true protein content increased significantly (P<0.05). While the contents of non-protein nitrogen, cellulose, semi-cellulose, EE, amygdalin and tannin decreased significantly(P<0.05).The contents of biomass, TP, non-protein nitrogen, EE, cellulose, hemicellulose model had significant correlation with fermentation kinetics (P<0.05). The predicted values of fermentation kinetics were fit with the experimental values.The fermentation kinetics model can describe the fermentation process.Microbial fermentation had the function of elimination of antinutritional factors.4)The changes of almond skin nutrients in animal metabolism. Investigation of the nutrient degradation rule of almond skin and its fermented feedstuff was studied.Three Dorper×Han crossbred male sheep fitted with permanent rumen fistula were selected to estimate DM, OM, CP, NDF and ADF ruminal degradability in situ. The results showed as follows:After fermentation, the nutrient levels of almond skin improved. The effective degradabilities of DM, OM and NDF of two kinds of almond skins had no significant differences(P>0.05). The effective degradabilities of CP and ADF of fermented almond skins improved significantly compared with raw almond skin (P<0.05). Solid state fermentation could improve the nutrient level of almond skin for ruminants.