Rui Duan

Characterisation of acid-soluble and pepsin-solubilised collagen from jellyfish (Cyanea nozakii Kishinouye)

Annual outbreaks of the Jellyfish (Cyanea nozakii Kishinouye) in the waters of the Yellow Sea and the East China Sea are regarded as a nuisance. Thus, utilizing this jellyfish species is of great significance to reduce harm to fisheries and marine environments. The yield of the acid-soluble collagens (ASCs) from the C. nozakii umbrella was 13.0% (dry weight) and that of the pepsin-solubilised collagens (PSCs) was 5.5% (dry weight). The SDS-PAGE patterns of the ASCs and PSCs differed from that of type I collagen, which indicate the presence of (α1)3. The denaturation temperature (Td) of the collagens was approximately 23.8°C. Fourier transform infrared spectroscopy proved that the ASCs and PSCs retained their helical structures and the As, Pb, and Hg content of the collagens, detected by ICP-MS, were considerably lower than the national standards. The results suggest that collagens isolated from C. nozakii can potentially be used as an alternative source of collagen for use in various applications.

The functional properties and application of gelatin derived from the skin of channel catfish (Ictalurus punctatus)

The objective of this work was to extract gelatin from skin of channel catfish (Ictalurus punctatus) and to study its functional properties and application in ice-cream and beer. SDS-PAGE patterns showed that channel catfish gelatin (CCG) had more high molecular weight components (β and γ chains) than had calf bone gelatin (CBG). The viscosity of CCG was 42mPa.s at 10°C, which was three times more than that of CBG. Compared to CBG, CCG presented higher emulsion capacity and stability, as well as higher foaming stability. CCG conferred the ice-cream samples and beer with better mouth feel and clarification effect, respectively. The results indicated that CCG had great potential to be utilized in the food industry.

Three types of proteinases in Japanese common squid Todarodes pacificus hepatopancreas as studied by using carp myofibrils as substrate

Three types of proteinases, namely cysteine, metallo, and serine proteinases, were found in squid hepatopancreas by studying the inhibition spectra using carp myofibril as substrate. The cysteine, metallo, and serine types showed the highest activities at 50, 35, and 40°C, respectively. The optimal pHs were 5, 7, and 9 for the cysteine, metallo, and serine types, respectively. When assayed at 20°C and pH 7.5, the metallo type showed the highest activity. The metallo type was characterized by a high selectivity in the digestion of myosin. Among the three enzymes, the cysteine type was found to be the most stable against thermal and acid treatments. Heat-treated myofibrils were more susceptible to the cysteine and serine types, but less susceptible to the metallo type. Acid treatment of myofibrils also enhanced the digestibility by the cysteine type. The results indicated that the cysteine type seemed to be the most suitable enzyme to produce peptides from denatured myofibrils by their random digestion.

Analysis and improvement of stability of pepsin-solubilized collagen from skin of carp (Cyprinus carpio)

Pepsin is widely used for the extraction of pepsin-solubilized collagens (PSC) from many resources. PSC-A and PSC-P were prepared from carp skin using 0.1 mol L−1 acetic acid and 0.02 mol L−1 Na2HPO4 (pH 7.2) as the dialysis solution, respectively. SDS-PAGE patterns showed PSC-A and PSC-P as type I collagens, as well as acid soluble collagen (ASC). When incubated at 40°C, no degradation was observed for ASC, but PSC-A and PSC-P were degraded into short peptides, showing lower stability than ASC. The results indicate that pepsin remaining in the PSCs resulted in their degradation, which was confirmed by the inhibition using pepstatin. This research revealed the behavior of the remaining pepsin in pepsin-solubilized collagens and an approach to the PSC stability improvement was proposed. Chromatography profiles showed that new PSC prepared by the improved method had almost the same stability as ASC.