Study On Bitterness Mechanism Of Enzymatic Hydrolysate Of Soybean Isolate Protein And Debittering Methods

Soybean Peptides (SP) were prepared from soybean protein isolates by using Alcalase. The relations between Degree of Hydrolysis (DH) and distribution of Molecular Weight (MW), as well as the bitterness of peptides, were studied. The peptides were separated by gel filter chromatography according to the size of MW, and then the bitterness of the separated peptides was determined by sensory evaluation. The result showed that the MW of Soybean Protein Hydrolysates (SPH) decreased with an increase in DH. When DH reached about 25%, the MW of most SPH ranged from 500 to 1000 daltons. The bitter peptides had the same range of MW as the above. The masking method was applied to debitter SPH. Organic acids, acidic amino acids, sweet agents, and I~3 梒lcyodextrin showed a great effect on masking the bitterness, and sugar with acids had a better debittering effect. Effects of pH valve, temperature and dosage of adsorbents(active carbon and polystarene adsorptive resin) on debittering of SPH were investigated systematically. The PH value 5.0, 55拁C and 3.5% of powder active carbon was the best combination of parameters, under which, the bitterness of SPH could be removed mostly. The polystarene adsorptive resin had some effect on debittering, but subsequently application of ?cyclodextrin could remove the bitterness completely after use of polystarene absoptive resin. 2梑utanol showed a very good debittering effect. The bitterness of SPH could be eliminated with 50% (v/v) of 2梑utanol. However, special attention should be paid to security of 2梑utanol. The precipitation at isoelectrie point for SPH and soybean protein solution was studied. The precipitation amount of the soybean protein solution was seven times as high as that of SPH. After removal of the precipitation, the bitterness of SPH decreased slightly. The relation between DH & the bitterness of SPH was studied. With the increase in DH, the bitterness increased rapidly to a maximum, and subsequently dropped gradually. Flavorzyme, a exopeptidase, had a significant effect on debittering, and could drop the bitterness value rapidly & dramatically.