Owing to the increasing environmental concerns and requirements for high-quality foods, edible films and coatings (based on proteins, polysaccharides, natural phenolic active substances, etc.) are being developed as effective alternatives to traditional plastic packaging. Gelatin is extracted from collagen. It is an ideal material for food packaging due to its versatile advantages such as low price, polymerization, biodegradability, good antibacterial and antioxidant properties, etc. However, gelatin film exists poor waterproof and mechanical properties, which limit its developments and applications in food packaging. Previous studies show that pure gelatin can be modified by adding active ingredients and incorporating them with bio-polymers to improve its mechanical properties, aiming to achieve the desirable effect of preservation. This review mainly shows the preparation and molding ways of gelatin-based edible films and the applications of gelatin modified with other biopolymers. Furthermore, this review provides the latest advances in gelatin-based biodegradable packaging and food applications that exhibit outstanding advantages in food preservation.

Volatile compounds in fresh and dried eels were investigated. Electronic nose (E-nose), headspace solid-phase microextraction combined with gas chromatography–mass spectrometry (HS–SPME–GC–MS), and relative odor activity value (ROAV) were applied to distinguish odors between fresh and dried eels. Results showed that E-nose could effectively distinguish the aroma among fresh eels, eels dried under 35°C and 12°C, and different drying methods had a significant influence on nitrogen oxides and methane in volatile compounds of dried eels. Total 37 and 28 volatile compounds detected in dried and fresh eel, respectively, were remarkably different. Relative odor activity values (ROAV) identified hexanal, nonanal, benzaldehyde, octanal, and 1-octen-3-ol as key flavor compounds in both fresh and dried eels. However, a serial of compounds, including 2-ethylfuran, 2,3-octanedione, (E, Z)-2,6-nonadienal, D-limonene, and 2-Zn-pentylfuran, added the sweet and meaty flavor of dried eel and neutralized the original strong grassy and fishy taste of fresh eel, primarily led to the difference in their odors.

Acid soluble collagen (ASC) from scales of croceine croaker (ASC-C) was successfully isolated with the yield of 0.37% ± 0.08% (dry weight basis), and characterized as type I collagen on the basis of amino acid analysis and electrophoretic pattern. The antioxidant hydrolysate of ASC-C (ACH) was prepared through a two-stage in vitro digestion (4-h trypsin followed by 4-h pepsin), and three antioxidant peptides (ACH-P1, ACH-P2, and ACH-P3) were further isolated from ACH using ultrafiltration, gel chromatography, and RP-HPLC, and their amino acid sequences were identified as GFRGTIGLVG (ACH-P1), GPAGPAG (ACH-P2), and GFPSG (ACH-P3). ACH-P1, ACH-P2, and ACH-P3 showed good scavenging activities on hydroxyl radical (IC₅₀ 0.293, 0.240, and 0.107 mg/mL, respectively), DPPH radical (IC₅₀ 1.271, 0.675, and 0.283 mg/mL, respectively), superoxide radical (IC₅₀ 0.463, 0.099, and 0.151 mg/mL, respectively), and ABTS radical (IC₅₀ 0.421, 0.309, and 0.210 mg/mL, respectively). ACH-P3 was also effectively against lipid peroxidation in the model system. The antioxidant activities of three collagen peptides were due to the presence of hydrophobic amino acid residues within the peptide sequences. The collagen peptides might be used as antioxidant for the therapy of diseases associated with oxidative stress, or reducing oxidative changes during storage.

Type 2 diabetes mellitus (T2DM) is a complex metabolic disease threatening human health. We investigated the effects of Tegillarca granosa polysaccharide (TGP) and determined its potential mechanisms in a mouse model of T2DM established through a high-fat diet and streptozotocin. TGP (5.1×10³ Da) was composed of mannose, glucosamine, rhamnose, glucuronic acid, galactosamine, glucose, galactose, xylose, and fucose. It could significantly alleviate weight loss, reduce fasting blood glucose levels, reverse dyslipidemia, reduce liver damage from oxidative stress, and improve insulin sensitivity. RT-PCR and western blotting indicated that TGP could activate the phosphatidylinositol-3-kinase/protein kinase B signaling pathway to regulate disorders in glucolipid metabolism and improve insulin resistance. TGP increased the abundance of Allobaculum, Akkermansia, and Bifidobacterium, restored the microbiota abundance in the intestinal tracts of mice with T2DM, and promoted short-chain fatty acid production. This study provides new insights into the antidiabetic effects of TGP and highlights its potential as a natural hypoglycemic nutraceutical.

Cryoprotective saccharides are widely accepted antifreeze additives that reduce thawing loss, maintain texture, and retard protein denaturation in frozen seafood. In this study, the inhibition effects of carrageenan oligosaccharides and xylooligosaccharides on ice-crystal growth in peeled whiteleg shrimp were investigated and compared with sodium pyrophosphate treatment during frozen storage, especially the interactions between oligosaccharide molecules and ice crystals. The tissue microstructural results demonstrated that the fibers of shrimp muscle tissues from carrageenan oligosaccharide- and xylooligosaccharide-treated groups were arranged in a more tighter manner than those with sodium pyrophosphate treatment after 8 weeks of storage, which indicated that soaking in oligosaccharide solutions prior to freezing markedly slowed the damage caused to muscle tissues by large ice crystals. Ice-growth inhibition might play an important role in the cryoprotection of frozen shrimp. Furthermore, molecular docking and molecular dynamics (MD) simulations confirmed that oligosaccharides were generally close to the ice surface and embedded in ice layers via hydrogen bonds or hydrophobic or electrostatic interactions. The oligosaccharide–basal ice complex (ice-crystal structure) was partially destroyed, and some dislocation and disaggregation were observed around the oligosaccharide molecules. Thus, the incorporated oligosaccharides suppressed the growth of ice crystals, providing protection from freeze-induced damage. Overall, by comparing the experimental results to those from the MD simulations, a significant positive correlation existed between the oligosaccharides and ice-growth inhibition in shrimp muscle. These findings help better understand the cryoprotective mechanisms of oligosaccharides in frozen shrimp, and these two oligosaccharides may be potentially used as ice-growth inhibitors in seafood to maintain better quality during frozen storage.