Suppression of the formation of biogenic amines in mackerel mince by microbial transglutaminase

BACKGROUND

Microbial transglutaminase (MTGase) is an enzyme utilized in the food industry in many areas. In this study, the suppression effect of MTGase at various levels (0, 2, 5, 10 g kg(-1)) on the formation of biogenic amines in mackerel was determined during refrigerated storage of 8 days.

RESULTS

Mince added with 2 g kg(-1) MTGase showed the lowest formation of putrescine, cadaverine and tyramine throughout the storage. Histamine exceeded the consumable limit (500 mg kg(-1) ) after the 4th day, except for that containing 2 g kg(-1) MTGase. The formation of total volatile basic nitrogen and total free amino acid content were retarded and the pH value was unaltered by addition of MTGase. With increasing MTGase levels, the growth of total psychrophilic bacteria, mould, yeast and coliform bacteria was retarded. The sensory scores of mackerel mince increased as MTGase concentrations increased.

CONCLUSION

MTGase plays a role in maintaining the quality of mackerel mince during refrigerated storage. As a result of the present study, a new use for MTGase in the food industry is revealed. It will contribute especially in the field of development of products for consumers with allergic sensitivity.

The Effect of Washing, Microbial Transglutaminase, Salts and Starch Addition on the Functional Properties of Sardine (Sardina Pilchardus) Kamaboko Gels

The functional properties of kamaboko gels, produced from sardine surimi (SS), were evaluated based on three factors: (a) washing conditions, (b) absence or presence of microbial transglutaminase (MTGase), and (c) addition of CaCl2, MgCl 2, and NH4Cl. Fish gels prepared from sardine mince washed at pH 5.5 showed the highest L* values and whiteness index (WI). A similar trend was also observed for firmness. Addition of MTGase had a beneficial effect on the L* values and WI as well as on firmness and cohesiveness of kamaboko gels ( p<0.05). Fish gels containing CaCl2 or MgCl 2 were lighter and firmer compared to those containing NH4Cl ( p<0.05). Three transitions, using a differential scanning calorimeter (DSC), were observed during heating of surimi containing 50g/kg of unmodified wheat starch (UWS), occurring at 45.2 °C, 63.3 °C, and 71.4 °C and were substantially the same when UWS was added at higher concentrations ( p≥0.05). The thermal gelation of SS, studied with Dynamic Mechanical Analysis (DMA), occurred at three or four distinct stages named: gel softening, low temperature gelation, gel resolution, and high temperature gelation. The cooling process was found to be crucial in surimi gelation since it strongly contributed in the development of gel rigidity.

Characterization of the aroma of a wine from maccabeo. Key role played by compounds with low odor activity values

An extract from a dry young wine from Maccabeo was studied by aroma extract dilution analysis (AEDA), quantitative gas chromatography, and different sensory studies. In a first study, 53 different aroma compounds were quantified and used to prepare aroma models. 2-Methyl-3-furanthiol (FD = 16) and 4-methyl-4-mercaptopentan-2-one (FD = 2), could not be quantified and were not included in those models, which were not very similar to the original wine. Omission tests did not show the existence of impact compounds. In another set of experiments, selected aroma chemicals were added to the original wine, but in only in two cases (isoamyl acetate and gamma-nonalactone) was a positive effect noted, on banana and citric notes, respectively. After these discouraging results, 4-methyl-4-mercaptopentan-2-one and 2-methyl-3-furanthiol were quantified and included in the models. The concentration of the former was as low as 5 ng x L(-)(1) (odor threshold = 0.8 ng x L(-)(1)); however, its inclusion in the synthetic mixture had a significant effect, making it very close to the original wine. Its role was confirmed by omission tests. Results are briefly discussed.