Characteristics of fermented seasoning sauces using Tenebrio molitor larvae

As edible insects have come to be used as a dietary source of protein, related studies have been carried out in various fields. A liquid fermented seasoning was prepared using Tenebrio molitor larvae by applying the soy sauce fermentation process. Meju, koji, and roasted rice flour were combined with a 23% brine to produce a sauce. Aspergillus oryzae and Bacillus licheniformis were used to ferment raw or defatted insect larvae, and the resulting material was used as an insect meju. The insect koji was prepared with defatted insects and A. oryzae. Six sauce samples, including soy sauce with two different ratios of ingredients (meju:koji:roasted rice flour=6:2:2 and 8:1:1) were prepared with raw T. molitor larvae (raw insect sauce), defatted larvae (defatted insect sauce), and soy (soy sauce) after 20days of fermentation at 25°C. No difference in the L value was observed among experimental groups, but the 6:2:2 ratio sauces generally had higher L values than did the 8:1:1 ratio sauces. The raw insect sauce showed the highest b value. The overall color change (ΔE) over time was not significant, but the value was high for the insect sauce. Browning tended to increase as fermentation continued in the soy and raw insect sauces. Browning of defatted insect sauce increased, but decreased sharply on day 20. Sample pH values were 5.70–6.19 on day 0 and 5.66–6.02 on day 20. No significant change in pH was observed among samples. Titratable acidity increased overall during fermentation. The 6:2:2 ratio sauces had higher total soluble solids, reducing sugars, and total sugars than did the 8:1:1 ratio sauces. Total nitrogen content of the sauces was 1.06–1.19% after 20days of fermentation. The 6:2:2 ratio sauces showed greater amino‑nitrogen content (0.26–0.32% on day 20) than did the 8:1:1 ratio sauces, indicating more efficient protein degradation. The percentage nitrogen degradation rates were higher for the insect sauces than for the soy sauce. Essential and nonessential amino acids, as well as amino acid derivatives, increased by 1.5–2 times during fermentation. The raw M6 insect sauce had the highest total free amino-acid content of 510.42mg/kg. Glutamic acid, alanine, aspartic acid, serine, isoleucine, lysine, phenylalanine, and valine contents were high in the sauces.