Siriporn Riebroy

Changes in composition and functional properties of proteins and their contributions to Nham characteristics

Changes in composition and functional properties of proteins during fermentation of Nham, a Thai-fermented sausage, were studied. An alkaline-soluble fraction constituted a major protein component of Nham. The amount of each protein fraction in Nham varied, depending on the fermentation time. As fermentation proceeded, the progressive decrease in sarcoplasmic and myofibrillar protein fractions was accompanied by an increase in the alkaline-soluble fraction and non-protein constituents (P<0.05). Slow pH lowering to pH 4.6 during fermentation as a result of bacterial growth and accumulation of lactic acid affected the molecular conformation of the muscle proteins and resulted in changes in protein functional properties. The acid produced resulted in changes in solubility, water-binding capacity, textural properties, and color characteristics. Proteolysis of Nham proteins occurred during fermentation, resulting in increases in TCA-soluble peptides and free α-amino acids, which may contribute to the taste and aroma of Nham.

Bleeding of Farmed Atlantic Cod: Residual Blood, Color, and Quality Attributes of Pre- and Postrigor Fillets as Affected by Perimortem Stress and Different Bleeding Methods

The main objectives of the study were to (a) assess the effect of perimortem stress on blood drainage, (b) compare the efficiency of gill cutting and direct gutting as bleeding methods, and (c) compare pre- and postrigor filleting strategies for presence of residual blood in Atlantic cod fillets. Anesthetized cod had significantly higher drainage of blood compared to stressed fish. Nevertheless, the visual assessments of residual blood were not affected by stress or bleeding method. Some minor, but significant, differences between pre- and postrigor fillets were found. Stressed fish were initially less light in color than those unstressed, but after ice storage there was no noticeable difference. However, initially, the largest difference in fillet color was due to different bleeding methods. Fillets cut from fish subjected to gill cutting were lighter and less red in color than those bled by direct gutting. After 7 and 21 days of storage, the color differences observed in fresh and salted fillets, respectively, were mainly due to the different rigor status when they were filleted, indicating that fillets cut postrigor were superior to fillets cut prerigor. Prerigor filleting resulted in lower water holding capacity after ice storage in anesthetized, direct gutted cod.

Physicochemical Characteristics of Glucosamine from Blue Swimming Crab (Portunus pelagicus) Shell Prepared by Acid Hydrolysis

A series of 20 new biologically active derivatives of 2-{4, 5-(substituted diphenyl)-4H-1,2,4-triazol-3-ylthio}acetyl chloride has been synthesized, with the aim to investigate antimicrobial, free radical scavenging activity. All the synthesized compounds were characterized by spectroscopic data and elemental analysis. The final compounds were tested for antibacterial activity against Gram-positive bacteria: Staphylococcus aureus MTCC 3160, Bacillus subtilis MTCC 441; Gram-negative bacteria: Escherichia coli MTCC 443, and, for antifungal activity, against Candida albicans MTCC 227 and Aspergillus niger MTCC 281, taking ciprofloxacin as antibacterial and fluconazole as antifungal standard drugs. Compound 7a 6 was found to be the most effective antibacterial (MIC = 3.12 µg/ml), and compounds 7a 2 and 7d 1 (MIC = 3.12 and 6.25 µg/ml) had the most effective antifungal effects on the selected strains, as compared to the standard drugs. The results of antioxidant studies revealed that compound 7b 1 was found to be most active antioxidant, with 40.4±0.687 µg/ml, and compounds 7b 3 , 7d 7 , and 7d 4 also showed promising free radical scavenging activity, as compared with the standard drug ascorbic acid.