Effects of microbial transglutaminase and starch on the thermal gelation of salted squid muscle paste

ABSTRACT:   The addition of microbial transglutaminase (MTGase) to salted squid muscle paste greatly strengthened the elasticity of the thermal gel, which was produced by the preferential cross-linking of myosin heavy chains through a two-step heating process that consisted of setting at 40°C and subsequent heating to 80°C or 90°C. Starch increased the breaking strength of thermal squid gels, but decreased the deformation. Thus, the starch-added gels became harder and less elastic. Although, when both MTGase and starch were added to squid muscle paste, the changes in viscoelastisity and myosin cross-linking reaction were similar to those with MTGase alone during setting, the storage and loss moduli of the paste sharply increased with an increase in starch content above 70°C. Subsequently, the thermal gel texture became more brittle or breakable than gels prepared by setting with MTGase only.     

Changes in meat texture of three varieties of squid in the early stage of cold storage

ABSTRACT: The present study examined the changes in texture and protein components during cold storage of different squid varieties. Raw oval squid, Japanese common squid and arrow squid were sliced fresh and the muscles were stored at 4°C for 0, 4, 8, 12, 18, 24, 48 and 120 h. The rheological measurements, protein components and amounts of collagen were examined. The adhesiveness of each squid increased significantly in the early stage of cold storage. In all varieties, penetration decreased at 4 h, which is considered to be rigor mortis, then increased. The amounts of total collagen, 20°C water-soluble collagen and 70°C water-soluble collagen did not change significantly in each variety during cold storage. Sodium dodecylsulfate–polyacrylamide gel electrophoresis (SDS-PAGE) pattern showed that the 580 kDa component gradually disappeared up to 48 h. The correlations between the amounts of 580 kDa component and adhesiveness or firmness were high. Models of fit based on chemical kinetics accurately expressed the behavior of adhesiveness, firmness and penetration showing that 63.2% of adhesiveness changes occurred in 13–19 h and that 63.2% of firmness changes occurred in 18–24 h.     

Size selectivity of a trammel net for oval squid Sepioteuthis lessoniana

ABSTRACT:   The size selectivity of a trammel net for herded oval squid Sepioteuthis lessoniana in Tateyama Bay, Chiba Prefecture, was estimated by comparison between the mantle length frequency distributions of oval squid caught by a trammel net and by a set net. The measured mesh sizes of the inner net of the trammel net and of the final section of the set net were 85.3 and 11.3 mm, respectively. In the trammel net fishery where oval squid are herded into the net, most of the oval squid are caught in the bag-shaped inner net. Hence, the logistic function was employed for the size selectivity curve of the trammel net. The 'share each length's catch total' (SELECT) model was implemented for the estimation of the selectivity curve. The size selectivity r ( l ) of the trammel net for the oval squid was expressed as a logistic function of the mantle length l : r ( l ) = exp(−18.57 + 0.88  l )/[1 + exp(−18.57 + 0.88  l )]. From these logistic parameter estimates, the 50% selection mantle length and selection range ( L ₇₅– L ₂₅) were calculated as 21.07 and 2.49 cm, respectively. The selection probability of oval squid whose mantle girth was equivalent to the mesh perimeter of the inner net was 0.09. Accordingly, oval squid of a girth smaller than the mesh perimeter were likely to pass through the mesh to escape from the net.     

Suppression of fish meat softening by strict control of storage temperature

ABSTRACT:   Changes in meat firmness and structure of cultured yellowtail at several storage temperatures, from −1.5°C to 10°C, were compared. Firmness decreased less at −1.5°C and 10°C than at the other temperatures. During storage at temperatures from −0.5 to 4.0°C, expansion of intercellular space, which indicates weakening of the connecting force between muscle cells, began to increase after 8 h storage, and the ratio of space to the whole area increased by 3.4–4.9 times after 24 h of storage. However, at −1.5°C and 10°C, the increase of intercellular space was suppressed, and the ratio was 2.4–2.6 times, even after 24 h storage. Collagen fibrils connecting muscle cells disintegrated after 24 h storage at all storage temperatures. Conversely, in 10°C storage, the fine structure of muscle, except for collagen fibrils, was maintained better than at other storage temperatures. These findings indicate that −1.5 and 10°C storage could maintain fish-meat quality for longer periods than storage at −0.5, 1.0, or 4.0°C, the normal refrigeration temperature.     

Solubilization of type I and V collagens in Japanese flounder muscle during chilled storage

ABSTRACT:   The post-mortem changes of type I and V collagens in Japanese flounder muscle during chilled storage were examined. The muscle softened significantly within 12 h under chilled storage. Both type I and V collagens isolated by ion-exchange chromatographies showed no remarkable changes in band patterns even after 24 h of storage, suggesting that degraded collagen molecules may be removed from the collagen fraction by a conventional preparation method. In contrast, type I and V collagen molecules were detected by Western blotting with each specific antibody in a saline extract and gradually increased during chilled storage. These results suggest that both type I and V collagens may participate in the post-mortem softening of fish muscle.     

Possible degradation of type I collagen in relation to yellowtail muscle softening during chilled storage

ABSTRACT:   In this paper, the detection of type I collagen degradation during the softening phenomenon of yellowtail muscle, was examined. Acid soluble collagen was isolated from dorsal ordinary muscle at death and after 24-h chilled storage. In the abundant ratio of subunit components, an increase in β12 chain (5.4 points) and a decrease in components with molecular weights larger than γ chain (7.0 points) after 24-h chilled storage, was found. Type I collagen was detected in the alkali-soluble fraction by SDS-PAGE. Its amount calculated from hydroxyproline contents in alkali-soluble fraction was increased from 0.097 mg/g muscle to 0.155 mg/g muscle during 24-h storage. The increased alkali-soluble collagen (0.058 mg/g muscle) was about 1.4% of whole collagen. These results suggest that a slight decomposition of type I collagen of yellowtail muscle may occur and subsequently becomes alkali-soluble corresponding to postmortem softening.     

Effect of water temperature on gonadal development and emaciation of Japanese common squid <Emphasis Type="Italic">Todarodes pacificus</Emphasis> (Ommastrephidae)

ABSTRACT:   In this study, the site of spawning ground and the relationship between oceanographic conditions and gonadal development and emaciation of the Japanese common squid Todarodes pacificus were examined based on data from research cruises. The research cruises were conducted in the south-western part of the Sea of Japan and the East China Sea in the winter of 1999. Sea surface temperature (SST) ranged 12.7–23.2°C in the survey area. Mature females concentrated on the continental shelf of the East China Sea, suggesting a major spawning ground was formed in this area. Gonadal development of the collected squid was examined using ovary somatic index (OSI) and oviduct somatic index (ODSI) in females, and emaciation was examined using mantle muscle somatic index (MI) and hepatosomatic index (HSI). Mean OSI and ODSI increased with SST at the stations where SST was greater than 15°C, particularly where SST ranged between 15 and 18°C. In contrast, mean MI and HSI decreased with increase in SST at the stations where SST was above 15°C. These results indicate that female gonads develop rapidly at SST above 15°C, and at the same time adult squids tend to be emaciated at this temperature condition.     

Specific accumulation of heavy metals in squid collected from offshore Korean waters: preliminary results for offshore biomonitoring and food safety assessment

ABSTRACT:   Japanese common squid Todarodes pacificus collected from the East Sea/Sea of Japan were analyzed for cadmium, zinc and copper to elucidate the specific accumulation of heavy metals in various organs of squid of varying size and sex. There was no relationship between the size and sex of squid and the concentrations of heavy metals in various organs. Amongst organs, the liver contained the highest concentrations of all metals and the mantle had the lowest concentrations. In the liver and gills, concentrations of copper were higher than the other metals because of the existence of copper in hemocyanin in the blood. Cadmium showed the highest ratios (L/M) of the concentrations in the liver and in the mantle, even though cadmium in liver had lower concentrations than copper and zinc. This indicates that cephalopods constitute an important source of cadmium for cephalopod predators. The results show that the Japanese common squid is a useful bioindicator of metal pollution in offshore Korean waters.     

Preventive method of color deterioration of yellowtail dark muscle during frozen storage and post thawing

ABSTRACT:   The aim of this study was to develop a practical preventive method for color deterioration of sliced or filleted yellowtail muscle, especially of dark muscle, during frozen storage and post thawing. When the sliced meats were packaged in a vacuum with low oxygen permeable flexible films and then stored frozen below −40°C, no significant discoloration or browning of dark muscle was observed for 9 months or more. For higher temperature storage at −20°C or −30°C, nitrogen gas substituted packaging was a useful practical method for storing sliced meats for 6 weeks. In order to prevent color deterioration of sliced meats after thawing and subsequent storage at 0°C, the efficacy of materials of packaging was investigated. The most desirable result was obtained by using a film with oxygen permeability of 50–90 cm³/m² per 24 h.