Relationship among pH, generation of free amino acids, and Maillard browning of dried Japanese common squid Todarodes pacificus meat.

Relationship among pH, generation of free amino acids (FAAs), and Maillard browning was investigated in Japanese common squid during air drying at 40 °C to prevent its discoloration. In the surface color measurement, increase in the b* value which is an indicator for Maillard browning of the dried squid was mitigated at pH 4.0-6.0 and accelerated at pH 7.5-9.0. Adjusting the pH to 5.5 effectively suppressed increasing of the b* value (p < 0.05). Arginine (Arg) generation involved in the Maillard reaction, was inhibited in the dried squid at pH 5.5 (p < 0.05). Maillard reactivities between ribose and amino acids were lower at pH 4.0 than at pH 5.5 (p < 0.05). These results indicate that browning of the dried squid is significantly suppressed at pH 5.5. Moreover, suppression of Arg generation is more effective than weakening of Maillard reactivity between ribose and Arg, in mitigating Maillard browning of the dried squid at an acidic pH.

The effect of organic salts on the browning of dried squid products processed by air-drying.

To control discoloration of dried Japanese common squid (Todarodes pacificus) product, influence of 0-1% organic salts, including sodium gluconate (Na-gluconate), sodium citrate (Na-citrate), sodium phytate (Na-phytate), sodium benzoate (Na-benzoate) and sodium tartrate (Na-tartrate), on Maillard browning in the squid meat during air-drying was investigated. Changes in surface color of the dried squid were mitigated by the addition of organic salts. Organic salts also showed inhibitory effects on autolysis and generation of free amino acids (FAAs), especially arginine, in both the dried squid meat and the model solution. Moreover, Maillard reaction degree of the dried squid was decreased by using organic salts. The addition of 1% Na-citrate or 1% Na-phytate well suppressed the browning of the dried squid (p < 0.05). The results indicated that organic salts having strong chelating ability, including Na-citrate and Na-phytate, can prevent the browning of the dried squid product by inhibiting the generation of FAAs.

The influence of proteases on the browning of dried squid products processed by air-drying.

To clarify why mantle meat from Japanese common squid (Todarodes pacificus) dried products discolor dramatically when processed by air-drying, the role of endogenous protease(s) on browning during the processing of dried squid products was studied. The involvement of endogenous protease(s) in the generation of Free Amino Acids (FAAs) participating in the Maillard reaction was characterized. The browning and myosin heavy chain degradation during air-drying were obviously mitigated by the addition of metalloprotease inhibitors, especially EGTA and 1,10-phenanthroline, followed by serine proteinase inhibitor, especially PMSF. The amount of total FAAs in dried products increased by only 0.17% with the addition of 1,10-phenanthroline and 5.0% with added EGTA. In autolysis models, protein autolysis was almost completely inhibited by 1,10-phenanthroline. The addition of, 1,10-phenanthroline inhibited the increase in total FAAs including arginine (Arg), followed by EGTA and PMSF. The results indicated that endogenous metalloproteases and serine proteases might influence the generation of FAAs including Arg, and contribute to product discoloration during air-drying.

Mechanism study of high browning degree of mantle muscle meat from Japanese common squid Todarodes pacificus during air-drying.

Mantle meat from the Japanese common squid (Todarodes pacificus) browns more than other squid meats during air-drying. The factors contributing to the browning of Japanese common squid, long-finned squid (Photololigo edulis) and bigfin reef squid (Sepioteuthis lessoniana) were studied in boiled and raw meat both before and after air-drying. Dried raw meat from the Japanese common squid browned more than dried boiled meat (b(∗) value, from 4.7 to 28.5). The results from SDS-PAGE showed significant degradation of myosin heavy chain (MHC) suggesting that protease activity in raw Japanese common squid meat was higher than in the other two species. The concentration of arginine (1932.0mg/100g) and ribose (28.8µmol/g) in Japanese common squid meat was higher than in the other two species. These results suggest that high protease activity and high concentrations of arginine and ribose increase the browning discoloration of Japanese common squid during air-drying.