Abstract:

In the present study, minced squid meat was used as the fermentation substrate for Bacillus natto to improve the
application value of squid minced meat. The effects of liquid-solid ratio (1:2–1:5), glucose concentration (0.5%–3.5%),
initial pH (6.0–9.0), fermentation time (24–96 h) and fermentation temperature (27–42℃) on the amino nitrogen content
of fermented broth were evaluated. Using one-factor-at-a-time method, the fermentation time and temperature were
selected as 72 h and 37 ℃, respectively. Subsequently, three variables including solid to liquid ratio (m/V), initial pH and
glucose concentration were optimized by response surface methodology based on Box-Behnken design using the amino
nitrogen content of fermented broth as the response. The optimal conditions for solid to liquid ratio, initial pH and glucose
concentration were determined as 1:1.2, 8.8 and 3.13%, respectively. Experiments carried out under these conditions led to
an amino nitrogen content of 2.457 mg/mL. Moreover, amino acid composition analysis demonstrated that the fermented
squid minced meat was rich in glutamic acid (84.141 mg/g), aspartic acid (49.480 mg/g) and glycine (49.425 mg/g). These
amino acids were responsible for umami and sweet taste characteristics with total content of 39.05%. The total essential
amino acid concentration was 149.320 mg/g, accounting for 31.86% of all determined amino acids. In addition, the relative
molecular weight distribution indicated that the fermented squid minced meat was composed of polypeptides, small peptides
and free amino acids.

Key words: minced squid meat, Bacillus natto, fermentation, response surface methodology, amino acid composition, relative molecular weight distribution