Development of industrial ultrasound system for mass production of collagen and biochemical characteristics of extracted collagen

•We designed a small-pilot and an industrial-scale ultrasonic extraction system.•Collagen extraction was increased by up to 2-fold compared to conventional methods.•Acetic acid required was 10-fold less in our method, compared with previous methods.•This system is environmentally friendly and cost-effective in collagen production. Collagen is a widely used material in food and cosmetic products, but it has high price because of complicated extraction process and low yields. In order to overcome these problems, a mass production system of collagen from fish skin has developed using an industrial scale of ultrasound extraction equipment. Collagen was extracted from flatfish skin using 0.05M acetic acid solution for a total of 3h in an ultrasound system and was collected by centrifugation. The collagen yields by this method were ∼31.3 and 46.2% after 1.5 and 3h, respectively, which were 1.5 and 2 times higher than those by the conventional method. The pepsin digestibility was examined to confirm whether the extract was native collagen. Despite pepsin treatment, the α1 (α3), α2, β chains of the collagen extracted by the industrial ultrasound system did not change, whereas gelatin were degraded almost completely and low molecular weight components were increased. In addition, the amino acid analysis result showed that the extract contained high contents of glycine, proline, and hydroxyproline, indicating that the extract has a typical collagen composition. Therefore, it was confirmed that the component extracted by the industrial ultrasonic system was native collagen.