Storage of Yellowtail (Seriola quinqueradiata) White and Dark Muscles in Ice: Changes in Content of Adenine Nucleotides and Related Compounds

Changes in Metabolic Profiles of Yellowtail (Seriola quinqueradiata) Muscle during Cold Storage as a Freshness Evaluation Tool Based on GC-MS Metabolomics

We applied metabolomics to the evaluation of yellowtail muscle as a new freshness evaluation method for fish meat. Metabolites from yellowtail ordinary and dark muscle (DM) stored at 0 °C and 5 °C were subjected to metabolomics for primary metabolites based on gas chromatography-mass spectrometry (GC-MS). For the annotated metabolites, we created statistically significant models for storage time prediction for all storage conditions by orthogonal partial least squares analysis, using storage time as the y-variable. DM is difficult to evaluate using the K value method, the predominant existing freshness evaluation method. However, in the proposed method, the metabolic component profiles of DM changed depending on storage time. Important metabolites determined from variables important for prediction (VIP) values included various metabolites, such as amino acids and sugars, in addition to nucleic-acid-related substances, especially inosine and hypoxanthine. Therefore, metabolomics, which comprehensively analyses different molecular species, has potential as a new freshness evaluation method that can objectively evaluate conditions of stored fish meat.

Taste Evaluation of Yellowtail (Seriola Quinqueradiata) Ordinary and Dark Muscle by Metabolic Profiling

We performed metabolic profiling on yellowtail (Seriola quinqueradiata) muscle to develop an objective taste evaluation method for fish meat. Dark (DM) and ordinary (OM) muscle samples before and after storage were subjected to gas chromatography-mass spectrometry (GC-MS) analysis and taste measurements using an electronic tongue. The metabolites identified by the GC-MS analysis were treated as x variables, and the taste values obtained by the electronic tongue were treated as y variables. The relationships between the metabolites and taste attributes were evaluated by two-way orthogonal projections to latent structures (O2PLS) analysis. The O2PLS analyses were normalized in two ways, unit variance (UV) and pareto (Par) scaling. The O2PLS (UV) analysis produced 3+1+0 models in Autofit and this model was statistically significant with R²Y (0.73) and Q² (0.52) metrics. In particular, significant correlations were found between DM or OM and metabolite intensity and taste attributes, and strong associations were found between “sourness” and lysine, “irritant” and alanine and phenylalanine, “saltiness” and pantothenic acid, and “umami” and creatinine and histidine. The O2PLS (Par) analysis of DM generated significant predictive models for “acidic bitterness,” “irritant,” “saltiness,” “bitterness,” “astringency,” and “richness.” Among these, only “irritant” was affected by storage. This method was thus effective in evaluating the taste of yellowtail muscle.

Expeditious prediction of post-mortem changes in frozen fish meat using three-dimensional fluorescence fingerprints

The present study was conducted to characterize fluorophores in the fish body using three-dimensional fluorescence fingerprints (3D-FFs) and to utilize these 3D-FFs obtained from frozen horse mackerel (Trachurus japonicus) fillets to predict early post-mortem changes. Alive fish were sacrificed instantly, preserved in ice until 2 days, and then filleted, vacuum packed, and frozen. Subsequently, 3D-FFs of the frozen fillets were acquired using F-7000 aided with a fiber probe. Post-mortem freshness changes were tracked by measuring adenylate energy charge (AEC) values and nicotinamide adenine dinucleotide (NAD and NADH) content. Partial least squares regression models for predicting AEC values and NADH content in frozen fish meat showed good fittings, with R2 of 0.90 and 0.85, by utilizing eight and five excitation wavelengths, respectively, based on their fluorescence features acquired from standard fluorophores. This novel approach of 3D-FFs could be utilized as an efficient technique for at-line monitoring of frozen fish quality.

Quality changes of anchovy (Stolephorus heterolobus) under refrigerated storage of different practical industrial methods in Thailand

Quality changes of anchovy (Stolephorus heterolobus) muscle during 7 days of refrigerated storage with ice and without ice were studied using several indicators: changes of ATP degradation products, K-value, TVB-N, TMA-N, Lactic acid, biogenic amines, sensory and microbiological analysis. During 7-day of refrigerated storage with ice and without ice, K-value, TVB-N, TMA-N and D, L-lactic acids contents increased with longer storage time (p ≤ 0.05). Major biogenic amines found in anchovy muscle during refrigerated storage were cadaverine, agmatine and tyramine, followed by putrescine and histamine. Skin and external odour by sensory evaluation, progressive decreases were observed as refrigeration time progressed. Storage of anchovy with ice resulted in a better maintenance of sensory quality, better control microbial activity, and the slowing down of biochemical degradation mechanisms. This result introduces the use of refrigerated storage with ice as a practical preliminary chilling for anchovy during industrial processing.

Chemical, sensory and shelf life evaluation of sliced salmon treated with salts of organic acids

This study was carried out to evaluate the shelf life, chemical quality and sensory attributes of salmon slices treated by dipping in 2.5% aqueous solution of sodium acetate (NaA), sodium lactate (NaL), or sodium citrate (NaC) during refrigerated storage at 1 degrees C. The chemical analyses demonstrated significant reduction in K value, hypoxanthine (Hx) concentration, total volatile base nitrogen (TVB-N), and trimethylamine (TMA) in treated salmon slices when compared with the control. Sensory scores of treated salmon were in a typical category for appearance, juiciness and tenderness compared with the control. Only minor changes in the sensory attributes were recognized by few panellists in NaA- and NaL-treated samples. A shelf life of 12, 12 and 15 days has been estimated for salmon treated with NaL, NaC, and NaA, respectively, versus 8 days for control. The salts of organic acids can therefore be used as safe preservatives for fish under refrigerated storage.

Comparative quality assessment of cultured and wild sea bream (Sparus aurata) stored in ice

Comparative quality assessment of cultured and wild sea bream stored in ice for up to 23 days was achieved by the monitoring of sensory quality, levels of nucleotide, nucleotide breakdown products, and texture by a texturometer. The changes in sensory quality of both raw and cooked fish were assessed using the modified Tasmanian and Torry schemes, respectively. K and related values (freshness indicators), namely, K, K(i), G, P, H, and F(r), were calculated. Linear increases (r(2) > or = 0.99) in K, K(i), G, and P (and a decrease in F(r)) values for cultured sea bream and in the H value for wild sea bream with increasing storage periods were observed. The limit for acceptability of cultured and wild sea bream stored in ice was approximately 16-18 days (average K, K(i), G, and P values: approximately 35-40%; H values: approximately 5% for cultured and 10% for wild; and F(r ) values: approximately 65-70%). The texture of cultured and wild sea bream decreased throughout the storage period, and they were not significantly (p > 0.05) different until after day 16 when the wild sea bream was significantly softer than the cultured. The sensory score of both cultured and wild raw fish showed a good relationship with some freshness and texture indicators over the entire storage period (r(2) values > or = 0.99). These indicators were K, K(i), G, P, and F(r) values for cultured and H value for wild fish.

Spoilage and shelf-life extension of fresh fish and shellfish

Fresh fish and shellfish are highly perishable products due to their biological composition. Under normal refrigerated storage conditions, the shelf life of these products is limited by enzymatic and microbiological spoilage. However, with increasing consumer demands for fresh products with extended shelf life and increasing energy costs associated with freezing and frozen storage, the fish-processing industry is actively seeking alternative methods of shelf life preservation and marketability of fresh, refrigerated fish and at the same time economizing on energy costs. Additional methods that could fulfill these objectives include chemical decontamination, low-dose irradiation, ultra-high pressure, and modified atmosphere packaging (MAP). This review focuses on the biochemical and microbiological composition of fresh fish/shellfish, the spoilage patterns in these products, factors influencing spoilage, and the combination treatments that can be used in conjunction with refrigeration to extend the shelf life and keeping quality of fresh fish/shellfish. The safety concerns of minimally processed/MAP fish, specifically with respect to the growth of Clostridium botulinum type E, is also addressed.