Effects of ultrasound pretreatment at different powers on flavor characteristics of enzymatic hydrolysates of cod (Gadus macrocephalus) head

To make better use of cod head (Gadus macrocephalus), a by-product of fish processing, the effects of ultrasound pretreatment on the enzymatic properties and volatile compounds of cod head enzymatic hydrolysates were investigated. The results demonstrated that ultrasound pretreatment at 150-600 W had a positive effect cod head enzymatic hydrolysates. The soluble peptides content of the enzymatic hydrolysates reached the highest value of 5.31 ± 0.16 mg/mL at the ultrasound power level of 450 W, and the content of peptide molecules < 3-kDa was up to 93.96%. The type and relative content of volatile compounds, especially aldehydes, alcohols, and ketones, also increased with the increase the ultrasound power. The electronic tongue results indicated that ultrasound pretreatment reduced bitterness and astringency. The electronic nose results indicated that the hydrogen- and alkane-containing odor components in the hydrolyzed liquid after ultrasound pretreatment differed significantly from conventional enzymatic hydrolysates. In conclusion, ultrasound pretreatment may be applicable as a suitable technology to assist enzymatic hydrolysis of the cod head, and as such, promote the utilization of fish by-products.