Marine gelatin is one of the food proteins used in food and non-food products, offering desirable functionalities such as gelling, thickening, and binding. Jellyfish has been chosen for this gelatin research, in view of the benefits of its main collagen protein and lower fat content, which may reduce the amounts of chemicals used in the preparative steps of gelatin production. To date, the lack of identified proteins in gelatin has limited the understanding of differentiating intrinsic factors quantitatively and qualitatively affecting gel properties. No comparison has been made between marine gelatin of fish and that of jellyfish, regarding protein type and distribution differences. Therefore, the study aimed at characterizing jellyfish gelatin extracted from by-products, that are i.e., pieces that have broken off during the grading and cleaning step of salted jellyfish processing. Different pretreatment by hydrochloric acid (HCl) concentrations (0.1 and 0.2 M) and hot water extraction time (12 and 24 h) were studied as factors in jellyfish gelatin extraction. The resultant jellyfish gelatin with the highest gel strength (JFG1), as well as two commercial gelatins of fish gelatin (FG) and bovine gelatin (BG), were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results show that the jellyfish gelatin (JFG1) extracted with 0.1 M HCl at 60°C for 12 h delivered a maximum gel strength of 323.74 g, which is lower than for FG and BG, exhibiting 640.65 and 540.06 g, respectively. The gelling and melting temperatures of JFG1 were 7.1°C and 20.5°C, displaying a cold set gel and unstable gel at room temperature, whereas the gelling and melting temperatures of FG and BG were 17.4°C, 21.3°C, and 27.5°C, 32.7°C, respectively. Proteomic analysis shows that 29 proteins, of which 10 are types of collagen proteins and 19 are non-collagen proteins, are common to all BG, FG, and JFG1, and that JFG1 is missing 3 other collagen proteins (collagen alpha-2 (XI chain), collagen alpha-2 (I chain), and collagen alpha-2 (IV chain), that are important to gel networks. Thus, the lack of these 3 collagen types influences the inferior gel properties of jellyfish gelatin.

The use of by-products of salted jellyfish for gelatin production offers valuable gelatin products rather than animal feed. Several washes or washing machines have reported removing salt in salted jellyfish. However, the green ultrasound technique has never been reported for the desalination of salted jellyfish. The objectives were to determine how effectively the raw material’s salt removal was done by combining the traditional wash and then subjected to the ultrasonic waves in a sonication bath for 20–100 min. For gelatin production, the ultrasonicated jellyfish by-products were pretreated with sodium hydroxide and hydrochloric acid, washed, and extracted with hot water for 4, 6, and 8 h. Results showed that the increased duration of ultrasound time increased the desalination rate. The highest desalination rate of 100% was achieved using 100 min ultrasonic time operated at a fixed frequency (40 kHz) and power (220 W). The jellyfish gelatin extracted for 4, 6, and 8 h showed gel strengths in 121–447, 120–278, and 91–248 g. The 80 min ultrasonicated sample and hot water extraction for 8 h (JFG80-8) showed the highest gel yield of 32.69%, with a gel strength of 114.92 g. Still, the 40 min ultrasonicated sample with 4 h of extraction delivered the highest gel strength of 447.01 g (JFG40-4) and the lower yield of 10.60%. The melting and gelling temperatures of jellyfish gelatin from ultrasonicated samples ranged from 15–25°C and 5–12°C, which are lower than bovine gelatin (BG) and fish gelatin (FG). Monitored by FITR, the synergistic effect of extended sonication time (from 20–100 min) with 4 h extraction time at 80 °C caused amide I, II, and III changes. Based on the proteomic results, the peptide similarity of JFG40-4, having the highest gel strength, was 17, 23, or 20 peptides compared to either BG, FG, or JFG100-8 having the lowest gel strength. The 14 peptides were similarly found in all JFG40-4, BG, and FG samples. In conclusion, for the first time in this report, the improved jellyfish gel can be achieved when combined with traditional wash and 40 min ultrasonication of desalted jellyfish and extraction time of 4 h at 80 °C.

Gelatin gummy jelly is a chewable snack with attractive synthetic colour and flavour. The use of natural carotenoid colourant, found in Gac aril or pulp, potentially benefits consumer health. The objectives of this study were to formulate gummy prototypes designed with varying levels of gelatin, sucrose, and glucose syrup, to vary the addition of whey protein concentrate (WPC) and freeze-dried (FD) Gac aril and pulp to the selected prototype, and to investigate changes in coloured WPC-mixed gelatin gummy during storage. The prototype containing gelatin, sucrose, and glucose syrup at 10, 50, and 40%, respectively, was selected based on its hardness, gumminess, and chewiness values. The addition of WPC (0.75%) to the selected prototype increased the values of hardness, springiness, and gumminess but reduced the values of cohesiveness and chewiness. Coloured WPC-mixed gelatin gummy with blends (0.5 g/100 g) of FD Gac aril and pulp at a ratio of 75:25 appeared yellow-orange and received the highest acceptance score. The quality of coloured WPC-mixed gelatin changed to a dull colour and a softer texture gel during storage. Therefore, Gac-coloured WPC-mixed gelatin gummy improvement for colour and texture qualities should be of concern for shelf-life stability.

Due to its excellent biocompatibility and ease of biodegradation, jellyfish gelatin has gained attention as a hydrogel. However, hydrogel produced from jellyfish gelatin has not yet been sufficiently characterized. Therefore, this research aims to produce a jellyfish gelatin-based hydrogel. The gelatin produced from desalted jellyfish by-products varied with the part of the specimen and extraction time. Hydrogels with gelatin: glutaraldehyde ratios of 10:0.25, 10:0.50, and 10:1.00 (v/v) were characterized, and their cefazolin release ability was determined. The optimal conditions for gelatin extraction and chosen for the development of jellyfish hydrogels (JGel) included the use of the umbrella part of desalted jellyfish by-products extracted for 24 h (WU24), which yielded the highest gel strength (460.02 g), viscosity (24.45 cP), gelling temperature (12.70 °C), and melting temperature (22.48 °C). The quantities of collagen alpha−1(XXVIII) chain A, collagen alpha−1(XXI) chain, and collagen alpha−2(IX) chain in WU24 may influence its gel properties. Increasing the glutaraldehyde content in JGel increased the gel fraction by decreasing the space between the protein chains and gel swelling, as glutaraldehyde binds with lateral amino acid residues and produces a stronger network. At 8 h, more than 80% of the cefazolin in JGel (10:0.25) was released, which was higher than that released from bovine hydrogel (52.81%) and fish hydrogel (54.04%). This research is the first report focused on the production of JGel using glutaraldehyde as a cross-linking agent.

By-products of the marine industry have gained attention for producing valuable food ingredients like gelatin, which might benefit food applications and decrease food waste. Gelatin is the only protein-based food hydrocolloid, mainly used for gelling, viscosity, or emulsifying in the food industry. So far, a number of researchers have reported that by-products of salted jellyfish can produce jellyfish gelatin. The quality of jellyfish gelatin gel depends on several factors including hydrochloric acid pretreatment, extraction temperature, and extraction time. However, the functional properties such as foaming and emulsifying of jellyfish gelatin are not well understood. This research was aimed at investigating the hydrochloric acid pretreatment effect of extraction times (12, 24, and 48 h) at 60 °C on the resulting gelatin's yield, physical, and functional properties. Results showed that jellyfish gelatin's yield, gel strength, and viscosity significantly increased with increasing extraction times. Jellyfish gelatin yields were 2.74-14.07%. The gel strength of jellyfish gelatin extracted for 48 h (325.97±2.84 g) was higher than that of jellyfish gelatins extracted for 12 h (210.46±3.97 g) and 24 h (261.60±3.25 g). All jellyfish gelatins can form gels at 4 °C. Viscosity values of jellyfish gelatin were 23.00-24.50 centipoise. The foaming capacity and foaming stability of jellyfish gelatin were 12.28-17.54% and 10.52-15.78%, respectively. The emulsification activity index of jellyfish gelatin was 13.11-13.30 m²/g, and the emulsification stability index was 39.19-56.42%. As a result, varied gelatin extraction periods influenced jellyfish gelatin's physical and functional properties, indicating that the extended extraction time of 48 h delivered the jellyfish gelatin that can be used as a foaming and emulsifying agent. Therefore, turning the jellyfish by-products into food ingredients like gelatin would increase product values and potential uses in the food and medical applications.