Biological Hydrolysis Of Corn Gluten And The Characteristics Of Products

The corn gluten meal (CGM) contains50%-70%corn proteins. The poor water-solubilityof corn protein limits its application in food and other industries. If the corn gluten wasmodified, the solubility and other function can be improved. The modifying of high substrateconcentration CGM needs little equipment capacity and high equipment utilization, so theefficiency of enzymolysis is better. Also, its useing value and comprehensive utilization ratecan be enhanced by modifying of high concentration of CGM, and which could providetheoretical basis and process parameters for industrialization of corn bioactive peptides.Based on the pre low substrate concentration, high substrate concentration of CGM is theobject of this study. The conditions of single enzyme-hydrolysis and dual-enzyme complexhydrolysis of CGM were studied in this paper, and fermentation process of high concentrationof CGM based on Bacillus natto (the original strain) was established.After alkali treatment, removal of starch and high temperature steam cooked of highsubstrate concentration of CGM by alkaline protease Alcalase, flavor protease Flavourzymeand composite protease Protamex, the optimum conditions of enzymatic hydrolysis within theexperimental range were determined, and molecular weight distribution of peptides in thehydrolyzate was determined by gel filtration chromatography. The optimum conditions ofCGM hydrolysis by Alcalase enzyme were as follows: substrate concentration of13.5%(w/v),enzyme concentration of2.5%(w/w),68°C, pH8.3and reaction time210min. Under theseconditions, the degree of hydrolysis of the hydrolyzate was28.81%, soluble protein contentwas31.69mg/mL, antioxidative activity was547.83U/mL, conversion rate of protein was36.92%and molecular weight distribution of peptide was between894.80Da~261.33Da. Theoptimum conditions of CGM hydrolysis by Flavourzyme were as follows: substrateconcentration of15%(w/v), enzyme concentration of2%(w/w),47°C, pH6.2and reactiontime120min. Under these conditions, the degree of hydrolysis of the hydrolyzate was12.59%,soluble protein content was10.64mg/mL, antioxidative activity was367.65U/mL, conversionrate of protein was11.61%and molecular weight distribution of peptide was between1228.29Da~234.11Da. The optimum conditions of CGM hydrolysis by Protamex enzymewere as follows: substrate concentration of13.5%(w/v), enzyme concentration of3.5%(w/w),58°C, pH6.8and reaction time180min. Under these conditions, the degree of hydrolysis ofthe hydrolyzate was13.18%, soluble protein content was32.36mg/mL, antioxidative activity was244.82U/mL, conversion rate of protein was21.37%and molecular weight distribution ofpeptide was between914.49Da~251.71Da.Using dual-enzyme complex hydrolysis of CGM, the results showed that, compared tosingle-enzyme complex hydrolysis, the efficiency of enzymatic hydrolysis could be enhancedsignificantly, and the sequence of enzyme had a great impact on hydrolysis. CGM washydrolyzed by Alcalase and Flavourzyme, flavourzyme and Protamex, Protamex and Alcalase,the degree of hydrolysis of the hydrolyzate were27.11%,26.95%and19.76%, and solubleprotein contents were50.33mg/mL,40.32mg/mL48.85mg/mL, antioxidant activity were634.35U/mL,576.79U/mL and593.21U/mL, and protein conversion rates were56.49%,28.53%and50.89%respectively, which were improved significantly compared to the singleenzyme hydrolysis. The effect is nearly to the enzymatic hydrolysis of the low concentrationsubstrate.Based on Bacillus natto as the original strain, UV mutagenesis was carried on, a mutantstrain NP-9-4with high degradation ability of CGM was obtained then through by separationplate method screening and shake flask rescreening,. The conditions of high concentration ofCGM fermentation by NP-9-4strain were optimized, and the optimum fermentationconditions were pH7.0, inoculum of3.33%(v/v), temperature32°C, shake flask speed200r/min, incubation time42h. Under this condition, the soluble protein content offermentation liquor was12.84mg/mL and antioxidative activity was328.55U/mL. At thesame time, the decolorization and milling of CGM fermentation liquor were studied. And thebest decolorization conditions of activated carbon were as followed: amount of activatedcarbon0.63%(w/v), temperature78.85°C, treating time23.55min, the fermentation liquordecolorization rate and protein recovery rate were49.30%and89.18%respectively. Bestmilling conditions were: entered wind temperature115°C, feed speed5mL/min, centrifugalatomizer speed25000r/min, and under these conditions, soluble protein recovery rate ofpeptide powder and water content were5.28%and89.22%respectively.