Effects of Fish-Derived Biological Preservatives on Cold Storage of Grass Carp ( Ctenopharyngodon idellus ) Fillets

Shelf-Life Extension of Refrigerated Turbot (Scophthalmus maximus) by Using Weakly Acidic Electrolyzed Water and Active Coatings Containing Daphnetin Emulsions

This research was to investigate the effect of weakly acidic electrolytic water (WAEW) treatments combining with the locust bean gum (LBG) and sodium alginate (SA) active coatings, containing daphnetin emulsions on microbiological, physicochemical, and sensory changes of turbot (Scophthalmus maximus) during refrigerated storage at 4°C for 24 days. Results showed that WAEW, together with LBG-SA coatings containing daphnetin emulsions treatments, could significantly lower the total viable count (TVC), H₂S-producing bacteria, pseudomonas spp., and psychrotrophic bacteria counts, and inhibit the productions of off-flavor compounds, including the total volatile basic nitrogen (TVB-N), inosine (HxR), and hypoxanthine (Hx). Furthermore, the treatments also prevented textural deterioration, delayed water migration, and had higher organoleptic evaluation results. Therefore, WAEW, together with LBG-SA coatings, containing daphnetin emulsions treatments, had the potential to improve the quality of turbot during refrigerated storage.

Application of Gelatin Incorporated with Red Pitaya Peel Methanol Extract as Edible Coating for Quality Enhancement of Crayfish (Procambarus clarkii) during Refrigerated Storage

China is one of the largest producers of red pitaya in the world and responsible for disposal of the huge amount of peel generated as a waste. The objective of this research was to evaluate the effect of the addition of red pitaya peel extract (RPPE, 1.0%, 2.0%, or 3.0% (w/v)) and 0.1% ε-polylysine (ε-PL) to a fish gelatin edible coating on the preservation of deshelled crayfish (Procambarus clarkii) during refrigerated storage. The physicochemical and water migration of the samples were determined during 8-day storage. Deshelled crayfish packaged in edible coatings exhibited significantly (p<0.05) lower values for total volatile basic nitrogen (TVB-N), K value maintenance, and free amino acids (FAAs). This study shows that application of an edible coating incorporated with RPPE and ε-PL is an effective strategy in retarding the quality deterioration in deshelled crayfish during storage.

Coating Effects of ε-Polylysine and Rosmarinic Acid Combined with Chitosan on the Storage Quality of Fresh Half-Smooth Tongue Sole (Cynoglossus semilaevis Günther) Fillets

The study was to evaluate the effects of chitosan-based coating combined with rosmarinic acid (RA) with different concentrations of ε-polylysine (ε-PL) on flavor retention and sensorial properties of half-smooth tongue sole fillets during storage at 4 °C. Results showed that chitosan-based coatings combined with ε-PL and RA contributed to the reduction of off-flavor compounds, such as total volatile base nitrogen (TVB-N), trimethylamine (TMA), and ATP-related compounds, and accumulation of free amino acids (FAAs). Nineteen volatile organic compounds were analyzed by gas chromatography-mass spectrometer (GC/MS) during storage, including seven alcohols, six aldehydes, and six ketones. The coating treated fresh half-smooth tongue sole (HTS) fillets significantly reduced the relative content of off-odor volatiles, such as 1-octen-3-ol, propanal, hexanal, and octanal. According to sensory evaluation results, chitosan-based coating combined with ε-PL and RA was an effective way to maintain quality of HTS fillets during refrigerated storage.

Identification of the Dominant Microbial Species of Spoiled Crisp Grass Carp ( Ctenopharyngodon idellus C. et V.) and Grass Carp ( Ctenopharyngodon idellus) Fillets during Cold Storage by Culture-Independent 16S rDNA Sequence Analysis

A new freshwater cultivation species, crisp grass carp (CGC; Ctenopharyngodon idellus C. et V.) has a special texture and is popular with consumers; thus, we should pay close attention to its storage conditions and bacterial degradation. CGC and grass carp (GC; Ctenopharyngodon idellus) were commercialized as fillets and subsequently stored at 4 and 8°C. Microbial growth parameters (total viable counts, psychrotrophic bacteria, and Pseudomonas spp.), physicochemical data (pH and total volatile base nitrogen), and sensory analysis were monitored during the storage period. Dominant microorganisms were identified using a 16S rDNA clone library and restriction fragment length polymorphism (RFLP) analysis after the fillets had spoiled completely. The results showed that Pseudomonas spp. lagged behind the psychrotrophic population and the total viable counts initially and increased more rapidly after storage for 2 days. Total volatile base nitrogen contents were found to increase with storage time in both species, coinciding with ongoing microbial change. The pH results obtained for both species during storage showed an overall increase at the end of storage. Sensory evaluation showed a shelf life of 3 and 6 days for both species at 8 and 4°C, respectively. RFLP analysis of the 16S rDNA clone library revealed that there were seven and five distinct RFLP pattern groups in the microflora of the spoiled CGC and GC fillets, respectively. Through RFLP patterns and 16S rDNA sequencing from the clones, it was determined that CGC fillets stored at 4°C were dominated by Pseudomonas spp. at the point of sensory rejection, whereas GC fillets were dominated by populations affiliated with Pseudomonas sp., Acinetobacter sp., and Aeromonas sp.