Effects of powdered activated carbon, diatomaceous earth and β-cyclodextrin treatments on the clarity and volatile compounds of tilapia (Oreochromis niloticus) skin gelatin

Research progress of fishy odor in aquatic products: From substance identification, formation mechanism, to elimination pathway

Fishy odor in aquatic products has a significant impact on the purchasing decisions of consumers. The production of aquatic products is a complex process involving culture, processing, transportation, and storage, which contribute to decreases in flavor and quality. This review systematically summarizes the fishy odor composition, identification methods, generation mechanism, and elimination methods of fishy odor compounds from their origin and formation to their elimination. Fishy odor compounds include aldehydes (hexanal, heptanal, and nonanal), alcohols (1-octen-3-ol), sulfur-containing compounds (dimethyl sulfide), and amines (trimethylamine). The mechanism of action of various factors affecting fishy odor is revealed, including environmental factors, enzymatic reactions, lipid oxidation, protein degradation, and microbial metabolism. Furthermore, the control and removal of fishy odor are briefly summarized and discussed, including masking, elimination, and conversion. This study provides a theoretical basis from source to elimination for achieving targeted regulation of the flavor of aquatic products, promoting industrial innovation and upgrading.

Mastering the art of taming: Reducing bitterness in fish by-products derived peptides

Processed fish by-products are valuable sources of peptides due to their high protein content. However, the bitterness of these peptides can limit their use. This review outlines the most recent advancements and information regarding the reduction of bitterness in fish by-products derived peptides. The sources and factors influencing bitterness, the transduction mechanisms involved, and strategies for reducing bitterness are highlighted. Bitterness in peptides is mainly influenced by the source, preparation method, presence of hydrophobic amino acid groups, binding to bitter receptors, and amino acid sequence. The most widely utilized techniques for eliminating bitterness or enhancing taste include the Maillard reaction, encapsulation, seperating undesirable components, and bitter-blockers. Finally, a summary of the current challenges and future prospects in the domain of fish by-products derived peptides is given. Despite some limitations, such as residual bitterness and limited industrial application, there is a need for further research to reduce the bitterness of fish by-products derived peptides. To achieve this goal, future studies should focus on the technology of fish by-products derived peptide bitterness diminishment, with the aim of producing high-quality products that meet consumer expectations.

Effects of acetic, malic, and citric acids on the large deformation behaviors of fish gelatin gels

This research was aimed to quantify the effects of acetic acid, malic acid, and citric acid (0, 0.5, 1.0, and 2.0 g/100 g H2 O) on the stress-strain responses of fish gelatin (FG) gels (2, 4, and 6.67 g/100 g H2 O) under uniaxial compression up to 68% of deformation. The first-order Ogden model fitted quite well for the compression responses of FG gels (R2  = 0.9909-0.9997). Protons from the acids played a key role on weakening the FG gel structures (gel rigidity, μ, decreased 11%-27%), as the μ values and pH values of FG gels were linearly correlated (R2  = 0.8240-0.9748), regardless of the acid type. The addition of an acid also resulted in a significant increase (p < .002) in the strain hardening capacity (α) of gels with 2 g FG/100 g H2 O. Both μ and α values of FG gels with higher gelatin concentrations were less affected by an acid partly due to their stronger buffering effects. The μ and α values of FG gels as affected by acids could not be fully explained based upon the pH changes, implying that the effects of acetate, malate, and citrate ions on the gel structure could not be ignored.

Effect of β-cyclodextrin deodorization on the volatile chemicals and functional properties of three types of gelatins

The exploration of deodorization is important for the application of gelatin in food industry. In this work, the effect of β-cyclodextrin (β-CD) deodorization on the volatile chemicals and functional properties of three types of gelatins (commercial porcine skin gelatin, cold water fish skin gelatin, and Chinese longsnout catfish skin gelatin) were studied. The results suggested the odors of commercial gelatins were significantly less than home-extracted gelatins. The β-CD deodorization efficiency was dependent on both β-CD concentration and volatile chemical. (E)-2-Octenal (C8H14O), 1-octen-3-ol (C8H16O), 2-pentyl-furan (C9H14O), and hentriacontane (C17H36) could be deodorized at low β-CD concentration (even at 2 mg/mL). The best β-CD deodorization concentration for 66.7 mg/mL of Chinese longsnout catfish skin gelatin was 30 mg/mL. β-CD addition could not change the gel forming ability and emulsion activity of gelatins, whereas it had different and concentration-dependent effects on the emulsion stability of gelatins. β-CD addition had no obvious effects on the droplet sizes, droplet coalescence and liquid-gel transition behaviors, but had different effects on the creaming of the emulsions stabilized by three types of gelatins. The encapsulation of β-carotene did not significantly change the droplet trimodal size distribution and liquid-gel transition of fish oil-loaded emulsions. However, β-carotene might delay the droplet coalescence. The creaming stability of β-carotene/fish oil-loaded gelatin/β-CD-stabilized emulsions was dependent on the gelatins, β-CD, and β-carotene. Finally, the β-carotene retention in the emulsions was dependent not on β-CD addition but on the nature of the gelatins. These results provided useful information to understand the molecular deodorization behaviors and explore the deodorization of emulsifiers for food emulsions.

Repurposing fish waste into gelatin as a potential alternative for mammalian sources: A review

Mammalian gelatin is extensively utilized in the food industry because of its physicochemical properties. However, its usage is restricted and essentially prohibited for religious people. Fish gelatin is a promising alternative with no religious and social restrictions. The desirable properties of fish gelatin can be significantly improved by various methods, such as the addition of active compounds, enzymes, and natural crosslinking agents (e.g., plant phenolics and genipin), and nonthermal physical treatments (e.g., ionizing radiation and high pressure). The aim of this study was to explore whether the properties of fish gelatin (gel strength, melting or gelling temperature, odor, viscosity, sensory properties, film-forming ability, etc.) could be improved to make it comparable to mammalian gelatin. The structure and properties of gelatins obtained from mammalian and fish sources are summarized. Moreover, the modification methods used to ameliorate the properties of fish gelatin, including rheological (gelling temperature from 13-19°C to 23-25°C), physicochemical (gel strengths from ∼200 to 250 g), and thermal properties (melting points from ∼25 to 30°C), are comprehensively discussed. The relevant literature reviewed and the technological advancements in the industry can propel the development of fish gelatin as a potential alternative to mammalian gelatin, thereby expanding its competitive market share with increasing utility.

Effects of deodorization by powdered activated carbon, β-cyclodextrin and yeast on odor and functional properties of tiger puffer (Takifugu rubripes) skin gelatin

The study investigated odor, physiochemical and functional properties of tiger puffer skin gelatin (TPSG) deodorized by powdered activated carbon (PAC, 0.5%), β-cyclodextrin (βCD, 3%) and yeast fermentation (YEF, 1%). Sensory test and electronic nose analysis exposed that three treatments lowered fishy odor intensity, coincided with decreased categories and levels of volatile compounds. Amide I, II and B of group βCD were shifted to lower wavenumber and amplitudes of amide bands in group YEF were much lower than those of others. Gel strength of group βCD and YEF declined, coincided with their higher relaxation time (component T₂₂ and T_2b) (p < 0.05). Marked decreases in gelling and melting temperature were found in group βCD. Emulsion activity index of group YEF decreased (p < 0.05) while emulsion stability index of all deodorized groups increased (p < 0.05). Different from uneven clusters with large size emulsion droplets in control, a homogenous system with small size droplets was observed in group YEF. PAC filtration increased clarity and lowered b* value (p < 0.05), but βCD treatment greatly decreased clarity (p < 0.05). Results suggest that YEF and βCD treatment deteriorated physical and functional properties of TPSG. Nevertheless, PAC filtration reduced fishy odor without compromising physiochemical and functional properties and is recommended for TPSG deodorization.