Yasuhiro Funatsu

Changes in extractive components and microbial proliferation during fermentation of fish sauce from underutilized fish species and quality of final products

To make use of underutilized fish species and produce high-quality condiments substitutable for those of mammalian origin, fish sauces were produced on a small industrial scale from three fish species, the flyingfish Cypselurus agoo agoo, the small dolphinfish Coryphaena hippurus, and the deepsea smelt Glossanodon semifasciatus, using salt and koji mold. During 180 days of fermentation, the pH decreased to approximately 4.5 and total nitrogen and free amino acids increased to approximately 2 g/100 mL and 6000 mg/100 mL, respectively. Halophilic and extreme halophilic bacterial counts dramatically increased from 106 to 108 colony forming units/mL between days 14 and 30 and decreased the reafter. In the final products, the pH and salt concentration decreased to between soy sauce and a Vietnamese fish sauce, Nuoc mam. The total amino acid and organic acid contents were almost the same as those of Nuoc mam and soy sauce. Sensory evaluation found these products to have lower smell, saltiness, and bitterness, and higher sweetness and umami taste than Nuoc mam. During fermentation, the histamine content increased in one or two of three fermentation tanks for each fish species. As a result, the histamine content of the final products was higher than that in Nuoc mam.

Effects of soy sauce koji and lactic acid bacteria on the fermentation of fish sauce from freshwater silver carp Hypophthalmichthys molitrix

The effects of soy sauce koji and the lactic acid bacterium, Tetragenococcus halophilus, were studied on the fermentation of fish sauce prepared from Chinese silver carp. The fish sauce prepared without koji and the lactic acid bacterium contained low levels of organic materials, total nitrogen, and organic acids. The use of koji was effective in increasing these qualitative parameters and further improved the amino acid score of the fish sauce. Addition of T. halophilus had an effect on lowering the pH value during the initial period of fermentation when the soy sauce koji was also supplemented. In contrast, T. halophilus-like bacteria were found to be predominant for all tanks fermented under the different starting conditions. Although it was not examined whether the T. halophilus-like bacteria observed after fermentation were the same as the starter-bacterium or not, it was suggested that T. halophilus plays an important role in the successful fermentation of silver carp fish sauce. Sensory evaluation conducted with Japanese and Chinese panelists also suggested the superiority of the use of koji for fermentation of silver carp fish sauce.

Extractive components of fish sauces from waste of the frigate mackerel surimi processing and a comparison with those of several asian fish sauces

Abstract Extractive components of a fish sauce (WS) prepared from wastes of frigate mackerel, which was processed into surimi, was compared with those of a fish sauce (MS) prepared in the same manner from the minced meat of frigate mackerel, and several Asian fish sauces (nampla, nuoc mam, patis and yeesui). Comparisons of free amino acids and bound amino acids were different with different samples. The major organic acid in WS and MS was lactic acid and that in yeesui was acetic acid. As sugar and sugar alcohol components, erythritol, arabitol, and mannitol were detected in WS and MS and sucrose in nampla and nuoc mam. The results of a taste panel test showed that the elemental taste factors of WS as well as those of MS and nuoc mam were well harmonized and thus tasted mellow. On the other hand, yeesui had a straight salty and peculiar taste.

Gelation Characteristics of Heat-Induced Gels Mixed Meat with Fish Proteins

The aim of this study was to make a comprehensive assessment of the quality of fish surimi (FS) from scale-eye plaice (SP) and surimi-like products from culled hen and FS from sand eel (SE) and Arabesque greenling (AG), which are regarded as low-valued food resources. The thermal gelation properties of a variety of the gels mixed meat with fish proteins were investigated by the use of the rheological and protein chemistry approaches, and the obtained results are as follows: (1) SP surimi has advantages such as high whiteness and suwari phenomenon at low temperature. (2) A variety of heat-induced gel products were able to produce with different mixing ratios of ground culled hen (GCH) and FS regardless of adding egg albumen powder (EAP). (3) Disulfide bond (S-S bond) was related to an improvement in gel properties of the directly heated gel mixed FS with GCH by addition of EAP. In particular, cleavage of myosin heavy chains in the gels, which have a high mixing ratio of SE surimi, was inhibited by addition of EAP. (4) AG can be used as ingredients of heat-induced gel products mixed fish with hen, while SP is inappropriate for the product because of syneresis phenomenon by use of microbial transglutaminase as a reagent for gelation. These findings revealed that adequate understanding of gel-forming ability of FS could be essential to improve gel properties of the heat-induced gels mixed meat with FS.

Acid-induced denaturation of carp myofibrillar Ca-ATPase in connection with KCl concentration.

Denaturations of carp myofibrils and myosin induced by changing pH and KCl concentration were studied. Myofibrils and myosin suspension was mixed with maleate-NaOH buffer to set the pH between 4.81 and 6.14 in the presence of various concentrations of KCl (0.1-1.0M) and stored at 2°C. The first order rate constant (KD) for inactivation of Ca-ATPase caused by the above treatment was then estimated. It was thus found that the KD of myofibrillar Ca-ATPase increased with lowering the pH as well as with increasing KCl concentration. On the other hand, the KD of myosin Ca-ATPase remained practically unchanged with changing the KCl concentration but increased with lowering the pH, in the same manner as in the case of myofibrils, In addition, the KD of myosin Ca-ATPase agrecd closely with that of myofibrillar Ca-ATPase in the presence of 1.0M KCl. These results strongly suggested that the actin part of carp myofibrils was denatured by acid treatment in the presence of 1.0M KCl, and lost its protective activity against thermal inactivation of myosin Ca-ATPase.