No abstract

Pacific whiting protein solubility was significantly affected as the pH shifted away from the isoelectric point (pH 5.5). The highest breaking force of gels was measured for fish proteins treated at pH 11, while high deformation values were obtained at pH 2 and 11. Sodium dodecylsulfatepolyacrylamide gel electrophoresis revealed that fish proteins were highly degraded by acid or alkali treatment. High activity of cathepsin B-like enzyme was detected from acid-aided fish proteins. Strong cathepsin L-like activity was found in fish proteins treated at pH 10.5, corresponding well to the lower breaking force and deformation. Disulfide bonds were thought to contribute to the high texture value of fish proteins treated at pH 11.KEY WORDS: acid-aided processing, alkali-aided processing, fish proteins, pH.

Relatively higher protein recovery was obtained in acid-aided processing. Solubility was lowest at pH 5 and gradually increased up to pH 11.0. A sharp increase in solubility occurred at alkaline pH between 9.5 and 11.0 and at acidic pH between 3.0 and 1.5. Cathepsin B and L showed higher activities in acid surimi than conventional surimi. Acid-aided surimi did not show Ca-and Mg-ATPase activity and also had lower surface hydrophobicity and sulfurhydryl contents than conventional surimi. Acid processing resulted in low breaking force, possibly due to the activity of retained cathepsin L enzymes. Myosin heavy chain (MHC) and actin were degraded in acid processing and produced major bands right below MHC and actin.

The potential of Tetragenococcus halophilus as a starter culture for flavor improvement in fish sauce fermentation was elucidated. Four strains of T. halophilus isolated from fish sauce mashes were inoculated to anchovy mixed with 25% NaCl with an approximate cell count of 10(6) CFU/mL. The α-amino content of 6-month-old fish sauce samples inoculated with T. halophilus was 780-784 mM. The addition of T. halophilus MRC10-1-3 and T. halophilus MCD10-5-10 resulted in a reduction of histamine (P < 0.05). Fish sauce inoculated with T. halophilus showed high contents of total amino acids with predominantly high glutamic acid. Major volatile compounds in fish sauce were 2-methylpropanal, 2-methylbutanal, 3-methylbutanal, and benzaldehyde. T. halophilus-inoculated fish sauce samples demonstrated the ability to reduce dimethyl disulfide, a compound contributing to a fecal note. The use of T. halophilus for fish sauce fermentation improves amino acid profiles and volatile compounds as well as reduces biogenic amine content of a fish sauce product.

The sausage samples were made from pork with spent laying hen breast surimi. The samples were divided into 4 groups [sausage made from pork (control) and sausage made from pork with 20% (T1), 40% (T2), and 60% (T3) of spent laying hen breast surimi]. In proximate compositions, the moisture and ash contents of the control were higher than sausage containing spent laying hen surimi samples in all storage periods. The pH and cooking loss were higher in T3 compared with other sausage samples. However, there was no significant difference in water-holding capacity among the sausage samples, whereas shear force was significantly higher in T2. In meat color, sausage containing spent laying hen surimi samples (T1, T2, and T3) have shown to have higher lightness (L) compared with control, and redness (a) was significantly higher in control and T1. Total amino acid content and essential amino acids were increased in sausage containing spent laying hen surimi samples at 0 d of storage. In fatty acid composition, saturated fatty acid was higher in control than sausage containing spent laying hen surimi samples. Thiobarbituric acid reactive substances value was lower in sausage containing spent laying hen surimi samples than control at 2 and 4 wk of storage. Cholesterol content was lower in control compared with sausage containing spent laying hen surimi samples. In sensory evaluation, most test items were not significantly different among the sausage samples although tenderness was higher in T2 and T3 at 0 d of storage.

Accumulative alcohol hangovers cause liver damage through oxidative and inflammatory stress. Numerous antioxidant and anti-inflammatory reagents have been developed to reduce alcohol hangovers, but these reagents are still insignificant and have limitations in that they can cause liver toxicity. Oyster hydrolysate (OH), another reagent that has antioxidant and anti-inflammatory activity, is a product extracted through an enzymatic hydrolysis process from oysters (Crassostrea gigas), which can be easily eaten in meals. This study was aimed at determining the effects of OH on alcohol metabolism, using a single high dose of ethanol (EtOH) administered to rodents, by monitoring alcohol metabolic enzymes, oxidative stress signals, and inflammatory mediators. The effect of tyrosine-alanine (YA) peptide, a main component of OH, on EtOH metabolism was also identified. In vitro experiments showed that OH pretreatment inhibited EtOH-induced cell death, oxidative stress, and inflammation in liver cells and macrophages. In vivo experiments showed that OH and YA pre-administration increased alcohol dehydrogenase, aldehyde dehydrogenase, and catalase activity in EtOH binge treatment. In addition, OH pre-administration alleviated CYP2E1 activity, ROS production, apoptotic signals, and inflammatory mediators in liver tissues. These results showed that OH and YA enhanced EtOH metabolism and had a protective effect against acute alcohol liver damage. Our findings offer new insights into a single high dose of EtOH drinking and suggest that OH and YA could be used as potential marine functional foods to prevent acute alcohol-induced liver damage.

Fish protein isolate were recovered from frozen small croaker using pH shift. The partial enzymatic hydrolysates were fractionated as soluble and insoluble parts. They were dried using the drum dryer and their functional properties were examined. The total nitrogen content of the enzymatic hydrolysates ranged from 12.9% to 13.7%. The degree of hydrolysis of precipitates was 18.2% and 12.2% for croaker hydrolysates treated with Protamex 1.5 MG (Bacilllus protease complex) and Flavourzyme 500 MG (endoproteases and exoproteases, Aspergillus oryzae), respectively. The TCA supernatant, after centrifugation of hydrolysates, contained numerous peptides ranging from 100 to 4000 daltons. The solubility of the supernatants was higher than that of the precipitates at 0% to 3% NaCl and pH 2 to 10. The precipitate of Flavourzyme-and Protamex-treated hydrolysates showed a high emulsion activity index value compared to egg white and bovine plasma protein. In addition, the highest emulsion stability was observed for Protamex-treated precipitate hydrolysates. Emulsion stability of Protamex-treated precipitate hydrolysates was comparable to those of protein additives (egg white, bovine plasma protein, and soy protein concentrate). Water and fat binding capacity of precipitates were higher than those of supernatant. The results indicate that precipitate hydrolysate from undersized croaker can be used in processed muscle foods as a functional and nutritional ingredient.

The whole genome sequences of Helicobacter pylori strain 26695 have been reported. Whole cell proteins of H. pylori strain 26695 cells were obtained and analyzed by two-dimensional electrophoresis, using immobilized pH gradient strips. The most abundant proteins were shown in the region of pI 4.0-9.5 with molecular masses from 10 to 100 kDa. Soluble proteins were precipitated by the use of 0-80% saturated solutions of ammonium sulfate. Soluble proteins precipitated by the 0-40% saturations of ammonium sulfate produced similar spot profiles and their abundant protein spots had acidic pI regions. However, a number of soluble proteins precipitated by more than 60% saturation of ammonium sulfate were placed in the alkaline pI regions, compared to those precipitated by 40% saturation. In addition, we have performed an extensive proteome analysis of the strain utilizing peptide MALDI-TOF-MS. Among the 345 protein spots processed, 175 proteins were identified. The identified spots represented 137 genes. One-hundred and fifteen proteins were newly identified in this study, including DNA polymerase III beta-subunit. These results might provide guidance for the enrichment of H. pylori proteins and contribute to construct a master protein map of H. pylori.