Identification of Odor Volatile Compounds and Deodorization ofPaphia undulata Enzymatic Hydrolysate

Unfavorable fishy odour is an inevitable problem in aquatic products. In the present study, headspace solid-phase mi- croextraction gas chromatography mass spectrometry （HS-SPME-GC-MS） analysis of volatiles from untreated samples and three deodorized samples （under the optimal conditions） ofPaphia undulata enzymatic hydrolysate revealed that the compounds contrib- uting to the distinctive odor were 1-octen-3-ol, n-hexanal, n-heptanal, 2,4-heptadienal, and 2,4-decadienal, whereas n-pentanal, n-octanal, n-octanol, benzaldehyde, 2-ethylfuran and 2-pentylfuran were the main contributors to the aromatic flavor. The deodoriz- ing effects of activated carbon （AC） adsorption, yeast extract （YE） masking and tea polyphenol （TP） treatment on a P. undulata en- zymatic hydrolysate were investigated using orthogonal experiments with sensory evaluation as the index. The following optimized deodorization conditions were obtained： AC adsorption （35 mg mL-1, 80℃, 40 rain）, YE masking （7 mgmL l, 45 ℃, 30 min） and TP treatment （0.4mgmL-l, 40℃, 50min）. AC adsorption effectively removed off-flavor volatile aldehydes and ketones. YE masking modified the odor profile by increasing the relative contents of aromatic compounds and decreasing the relative contents of aldehydes and ketones. The TP treatment was not effective in reducing the odor score, but it significantly reduced the relative content of alde- hydes while increasing that of alkanes. It is also notable that TP effectively suppressed trimethylamine （TMA） formation in a P. un- dulate hydrolysate solution for a period of 72 h.

Preparation of enzymatic hydrolysate using edible fungi by-products of soup seasoning:Effect of different enzymes on enzymatic hydrolysis

Edible fungi residuals are by-products from the preparation process of edible fungi hot pot soup seasoning.Enzymatic hydrolysate was prepared by cellulase(Cel),papain(Pap)and neutral protease(Nep)as well as their combination,and the reducing sugar content,the degree of hydrolysis(TDH),color,antioxidant capacity,inorganic elements and flavor of enzymatic hydrolysate were evaluated.The properties of enzymatic hydrolysate produced by compound enzymes were better than that of single enzyme,especially for the compound of enzymes Cel and Pap.The reducing sugar of enzymatic hydrolysate prepared by the combination of Cel and Pap increased 6.98 times and with TDH reached 25.80%±1.28%.In addition,edible fungi by-products after enzymatic hydrolysis exhibited yellowish-brown color with higher antioxidant capacity and little change of the volatile flavor.Enzymatic hydrolysate possessed a high retention rate of Na and Mg in the raw material,and there was no potential harm caused by excessive heavy metals(Cd,Pb,As).

PURIFICATION OF L-METHIONINE AND N-ACETYL-D-METHIONINE FROM THE MIXTURE OF ENZYMATICALLY DEACYLATED N-ACETYL-DL-METHIONINE

N-acetyl-D-methionine, NaAc and the remains of N-acetyl-L-methionine dramatically affect the purification of L-methionine when purified from the mixture of enzymatically deacylated N-acetyl-DL-methionine, leading to a low yield conventionally. Here, this paper reports a successful separation and purification of both L-methionine and N-acetyl-D-methionine by an H ion-exchange column. The pH, L-Met concentration and the ratio between the content of sodium cation and the ion-exchange capacity were optimized to obtain the maximum yield. Experimental results indicate that, under the optimized conditions, the yields of L-methionine and N-acetyl-D-methionine can reach as high as 85% and 75%, respectively.

Establishment of two-dimensional gel electrophoresis for soybean protein isolate and its application

To optimize the conditions for the establishment of two-dimensional gel electrophoresis(2-DE)of soybean protein isolate(SPI),we investigated Ampholine mixture,anodic and cathodic electrolytes,loading amount of sample,acrylamide concentration,p H gradient and gel staining method in twodimensional gel electrophoresis to optimize the protein imaging conditions in two-dimensional gel.The results of mixed-level design experiments showed that Ampholine,loading amount and gel staining method had significant effect(P<0.05)on 2-DE of SPI.The optimal conditions were Ampholine mixture(pH 3–10+pH 5–7 or pH 4–6+pH 5–7),loading amount of 2 mg sample and silver staining.Although the acrylamide concentration of the gel,the p H gradient,the anodic and cathodic electrolyte solutions had significant statistical effects on the protein separation degree,the complexity of the protein composition and the visibility of the gel images were more inclined to the 12%gel,the 3–10 pH gradient and the H3PO4/NaOH electrolyte.According to the established conditions,the hydrolyzed products of SPI emulsion were determined by 2-DE,and the dynamic changes of protein in the process of enzymatic hydrolysis were described.

Study on the Effect of Enzymolysis Condition on the Browning of Chinese Chestnut Serosity

In this study,with chestnut as a raw material,the effects of enzymolysis time,enzymolysis temperature and enzyme amount on hydrolysis process were investigated. The optimal reaction conditions were obtained by single factor and response surface experiment as follows： enzymolysis time of 75 min,enzymolysis temperature at 58 ℃ and enzyme amount of 7 U/g. Under these conditions,the browning degree of chestnut serosity was 1. 228.

Effect of proteases on water-soluble and fat-soluble aroma precursors of goat visceras protein hydrolysate

This study investigated the action of proteolytic enzymes in the production of goat viscera hydrolysates,and their flavoring potential.The study focus the production of flavor precursor molecules and the formation of volatile compounds resulting from four hydrolysis treatments:HA-Alcalase®,HF-Flavourzyme®,HN-Neutrase®,and HFN-Flavourzyme® and Neutrase®.The highest degree of hydrolysis (26.74%),number (23 volatiles) and concentration of volatile compounds (274.0 μg/L) were obtained with the action of Alcalase.The main classes of volatile compounds identified in hydrolysates included acids,aldehydes,pyrazines,terpenes and Streacker aldehydes.Amino acids,sugars and fatty acids were identified with higher concentrations in HF and HFN hydrolysates due to the low participation of these precursors in the formation of volatile compounds.Therefore,the use of Alcalase in the proteolysis of goat viscera stood out compared to other enzymes,providing impacting aroma compounds,such as pyrazines,for meat flavor.