Study On The Preparation Of Antioxidant Peptides With Peanut Meal By Microbial Solid State Fermentation

In this thesis, conditions of solid state fermentation with peanut meal by yeast, Aspergillusniger, Lactobacillus, Aspergillus oryzae and bacillus subtilis were studied. Under theoptimum conditions, preparation of antioxidant peptides and determination of antioxidantactivity were studied, respectively. Through membrane separation method for the separation ofdifferent molecular weight of peanut antioxidant peptides, studying the functional propertiesand physical and chemical properties of the antioxidant peptides had the vital significancefor peanut antioxidant peptides as additives used in the food.This thesis focused on the following seven parts:1. In the chapter one, the present situation of the use of the peanut and peanut meal,antioxidant mechanism and the main methods to prepare the peanut antioxidant peptides, theresults and status of microbial solid state fermentation were summarized.2. In the chapter two, Saccharomyces cerevisiae extracted from six strains of yeast wasused for fermentation. Solid state fermentation was used to investigate the effect ofexperimental factors including fermentation time, temperature, bacterial suspension volume andnutrient salt solution volume on the indexes including soluble nitrogen concentration, DPPHand hydroxyl free radicals scavenging rates. Results indicated that the soluble nitrogenconcentration of fermentation broth could reach10.74mg/mL, DPPH and hydroxyl freeradicals scavenging rates were93.57%and98.40%, respectively, under the followingoptimum conditions: addition of nutrient salt solution of10mL, brewing yeast liquid of3mL,fermentation temperature of30°C and fermentation time of60h.3. In the chapter three, Lactobacillus was used for solid state fermentation to investigatethe effect of experimental factors including fermentation time, temperature, bacterialsuspension volume and nutrient salt solution volume on the indexes including soluble nitrogenconcentration, DPPH and hydroxyl free radicals scavenging rates. Results indicated that thesoluble nitrogen concentration of fermentation broth could reach70.92mg/mL, DPPH and hydroxyl free radicals scavenging rates were95.00%and86.28%, respectively, under thefollowing optimum conditions: addition of nutrient salt solution of25mL, bacterial suspensionvolume of5mL, fermentation temperature of35°C and fermentation time of60h.4. In the chapter four, Aspergillus niger was used for solid state fermentation to investigatethe effect of experimental factors including fermentation time, temperature, bacterialsuspension volume and nutrient salt solution volume on the indexes including soluble nitrogenconcentration, DPPH and hydroxyl free radicals scavenging rates. Results indicated that thesoluble nitrogen concentration of fermentation broth could reach38.74mg/mL, DPPH andhydroxyl free radicals scavenging rates were81.22%and84.88%, respectively, under thefollowing optimum conditions: addition of nutrient salt solution of15mL, bacterial suspensionvolume of1mL, fermentation temperature of30°C and fermentation time of36h.5. In the chapter five, bacillus subtilis was used for solid state fermentation to investigatethe effect of experimental factors including fungus age, fermentation time, temperature,bacterial suspension volume, nutrient salt solution volume, water bath temperature and waterbath time on the indexes including soluble nitrogen concentration, DPPH and hydroxyl freeradicals scavenging rates. Results indicated that the soluble nitrogen concentration offermentation broth could reach123.36mg/mL, DPPH and hydroxyl free radicals scavengingrates were85.25%and89.85%, respectively, under the following optimum conditions: additionof nutrient salt solution of16mL, bacterial suspension volume of3.8mL, fermentationtemperature of45°C and fermentation time of41h.6. In the chapter six, Aspergillus oryzae was used for solid state fermentation to investigatethe effect of experimental factors including fungus age, fermentation time, temperature,bacterial suspension volume, nutrient salt solution volume, water bath temperature and waterbath time on the indexes including soluble nitrogen concentration, DPPH and hydroxyl freeradicals scavenging rates. Results indicated that the soluble nitrogen concentration offermentation broth could reach62.28mg/mL, DPPH and hydroxyl free radicals scavengingrates were86.00%and94.58%, respectively, under the following optimum conditions: additionof nutrient salt solution of26mL, bacterial suspension volume of5.3mL, fermentationtemperature of33°C and fermentation time of38h.7. In the chapter seven, preparation of antioxidant peptides by solid state fermentation with yeast, Aspergillus niger, Lactobacillus, Aspergillus oryzae and bacillus subtilis was studied andantioxidant activities were compared, respectively. Results indicated that the nature of theantioxidant peptides with yeast was more active and the functional properties and physical andchemical properties were determined. When the pH was smaller or larger, solubility, foamingability and emulsification were better. Foaming ability and emulsification were associated withprotein concentration.