| Glutamine (Gln) is regarded as a conditionally essential amino acid. In addition to the element of proteins and peptides, it plays an important role in the maintenance of acid-base balance, regulation of immune function as well as the raw material of substance and energy metabolism for the specific organ, tissue and cell. But the use of glutamine in nutrition physiological is limited due to the instability and low solubility. Glutamine-peptide is often used to overcome the shortcomings of glutamine. At present, synthetic Ala-Gln and Gly-Gln are mainly used, but the price is too high. It is an economic and effective way to prepare glutamine-peptides from the glutamine-rich plant protein by limited hydrolysis. The study on enzymolysis of defatted soymeal to prepare glutamine-rich peptides which has biological activity as soy protein is a glutamine-rich protein.The experiment was designed by Central Composite Design and the experimental data was regressed using SAS9.2 system as the degree of hydrolysis (DH) was used as the index. The optimum parameters were obtained by monadic operator of regression equation. The results indicated that: the optimum enzymatic hydrolysis conditions of trypsinase were: pH 7.83, temperature 50℃, added enzyme amount 4920U/g, the volume of solution to the weight of defatted soymeal was 12mL/g, hydrolysis time 3.7h, in this condition, the resulted DH was 12.79%, glutamine content was 5.92μmol/mL. As the optimum enzymatic hydrolysis conditions of Protamex were: pH 6.74, temperature 50℃, added enzyme amount 2859U/g, the volume of solution to the weight of defatted soymeal was 12 mL/g, hydrolysis time 10h, in this condition, the resulted DH was 15.72% . Dual-enzyme combination were used in order to enhance the DH, the optimum enzymatic hydrolysis conditions were pH 7.5, temperature 50℃, the volume of solution to the weight of defatted soymeal was 12 mL/g, hydrolysis time 10h, added enzyme amount of trypsinase was 4920U/g and the added enzyme amount of Protamex was 2859U/g. The trypsinase and Protamex were added at the same time with the result DH was 21.80%.The shorter of peptide chain, the more easily absorbed of glutamine peptide by body. It is showed by the results that the ratio of glutamine-peptide molecular weight distribution over 1000 has decreased from 28.64% to 8.63%, as the ratio of molecular weight below 1000 has increased gradually from 71.36% to 92.37% while the DH has increased from 6.76% to 22.02%. Protamex and trypsin were used as dual-enzyme combination of hydrolysis, the freeze-dried hydrolysates was obtained as glutamine peptide in crude with the DH of glutamine peptide is 22.02%, the yield is 70.82% based on glutamine, protein content 56.67%, moisture content 4.73%.Five fractions were obtained after the initial separation of glutamine peptide in crude by Sephadex gel G-15 (1.6×100 cm) column chromatography, with fraction 1, fraction 2, fraction 3 are the three major components. The Gln content of fraction 1, fraction 2 and fraction 3 was 8.6532%, 5.8114% and 5.7377%, accounting to the total Gln content of Gln peptide in crude was 64.60%, 12.31% and 22.66%, respectively. The effective glutamine of glutamine peptide in crude was concentrated in fraction 1; the molecular weight distribution of fraction 1 was concentrated in the 132 to 1000.With high temperature sterilization of 121℃and the storage stability test of glutamine peptide with different conditions, It is showed that the glutamine peptide has good thermal stability, can withstand high temperature sterilization, the most effective method for the storage of glutamine peptide is at 4℃in the form of solid, the rate of Gln decomposition was 2.8709% after three months. The rate of Gln decomposition was 8.1561% <10% after 85℃accelerated test for 6 weeks, so glutamine peptide has good storage stability.
|
PDF Full Text Request