Colour changes of fillets of rainbow trout (Oncorhynchus mykiss W.) fed astaxanthin or canthaxanthin during storage under controlled or modified atmosphere

Effect of Oscillating Magnetic Fields (OMFs) and Pulsed Electric Fields (PEFs) on Supercooling Preservation of Atlantic Salmon (Salmo salar L.) Fillets

Salmon, rich in protein and omega-3 fatty acids, has a short shelf life of 1 to 3 days when stored at 2 to 8 °C. Freezing, used for long-term preservation, often results in ice crystal formation. Ice crystals can cause structural damage, leading to cell wall rupture, which can affect the texture and cause nutrient loss. Ultimately, this process reduces the overall quality of the salmon. Supercooling, which cools food below its freezing temperature without forming ice crystals, offers an alternative. This study investigated the effects of oscillating magnetic fields (OMFs) and pulsed electric fields (PEFs) on ice crystal formation during salmon supercooling. The results showed that using OMFs and PEFs in supercooling reduced the storage temperature of salmon, maintaining a similar thiobarbituric acid reactive substances (TBARS) value to that of frozen and refrigerated samples. There was no significant difference in meat color between the fresh and frozen samples, and drip loss weight was comparable between the fresh and supercooled samples. The microbiological counts were the lowest in the supercooled samples compared to the frozen and refrigerated ones. These findings suggest that supercooling storage with OMFs and PEFs can mitigate quality degradation in salmon typically associated with freezing.

Study on the physicochemical indexes, nutritional quality, and flavor compounds of Trichiurus lepturus from three representative origins for geographical traceability

Trichiurus lepturus (hairtail) is an important economic component of China's marine fishing industry. However, due to the difficulty in identifying the appearance of hairtail from different geographical distributions, hairtails with geographical indication trademarks were imitated by general varieties. In this study, the texture characteristics, color, basic nutrients, amino acids, mineral, fatty acids, and volatile flavor substances were used as indicators for multivariate statistical analysis to determine whether three origins of hairtails from the habitats of Zhoushan (East China Sea, T.Z), Hainan (South China Sea, T.N), and Qingdao (Yellow Sea, T.Q) in the market could be distinguished. The findings revealed that there were significant differences in amino acids composition, mineral composition, fatty acid composition in lipids, and volatile flavor substances among the hairtails of three origins (P < 0.05), but no differences in color, texture, protein content. T.Z had moisture, crude fat, essential amino acids (EAA), flavor amino acids (FAA), unsaturated fatty acids (UFA), and docosahexaenoic acids and dicosapentaenoic acids (ΣEPA + DHA) contents of 74.33, 5.4%, 58.25 mg⋅g-1, 46.20 mg⋅g-1, 66.84 and 19.38%, respectively, and the contents of volatile alcohols, aldehydes and ketones were 7.44, 5.30, and 5.38%, respectively. T.N contains moisture, crude fat, EAA, FAA, UFA and ΣEPA + DHA as 77.69, 2.38%, 64.76 mg⋅g-1, 52.44 mg⋅g-1, 65.52 and 29.45%, respectively, and the contents of volatile alcohols, aldehydes and ketones as 3.21, 8.92, and 10.98%, respectively. T.Q had the contents of moisture, crude fat, EAA, FAA, UFA, and ΣEPA + DHA 79.69, 1.43%, 60.9 mg⋅g-1, and 49.42 mg⋅g-1, respectively. The contents of unsaturated fatty acid and ΣEPA + DHA were 63.75 and 26.12%, respectively, while the volatile alcohols, aldehydes, and ketones were 5.14, 5.99, and 7.85%, respectively. Partial least squares-discriminant analysis (PLS-DA) multivariate statistical analysis showed that volatile flavor compounds could be used as the most ideal indicators for tracing the source of hairtail. In conclusion, the findings of this study can distinguish the three hairtail origins using some basic indicators, providing ideas for hairtail geographical identification.

Application of soluble gas stabilization technology on ready-to-eat pre-rigor filleted Atlantic salmon (Salmo salar L.)

Abstract

The demand for high‐quality, convenient, and sustainable salmon products represents a potential for value‐added product development and novel packaging solutions. Soluble gas stabilization (SGS) technology, which applies dissolved CO₂ in the product before packaging, represents a novel approach to retain product quality and prevent microbiological deterioration during cold storage of pre‐rigor filleted salmon loins.

The present study aimed to examine the solubility of CO₂ in salmon loins as affected by rigor status. In addition, the effect of predissolved CO₂ on the overall quality of pre‐rigor vacuum‐packed Atlantic salmon (Salmo salar L.) was investigated during storage at 4°C. The CO₂ pretreatment was conducted, exposing loins to 100% CO₂ for 18 h at 4°C (the control group was kept in air at 4°C) before repackaging and storage for 15 days.

Dissolved CO₂ in the muscle (equilibrium achieved four days post packaging) was slightly higher in pre‐rigor than post‐rigor salmon loins (p_equilibrium = 0.006). Moreover, the overall spoilage (Hvalue) and microbiological stability of salmon fillets stored in SGS‐vacuum were significantly improved compared to vacuum‐packed loins (p < 0.05).

The results demonstrate that SGS technology can maintain the overall quality of pre‐rigor vacuum‐packed salmon loins without introducing the high gas‐to‐product volume ratio recognized by modified atmosphere packaging. Thus, the application of SGS technology on pre‐rigor loins can lead to higher economic gain and environmental benefits due to the reduced amount of required packaging material and reduced food waste.

Practical Application

CO₂ can be dissolved in pre‐rigor salmon loins before vacuum packaging to increase product shelf life during cold storage.

Changes in Volatile Composition of Cape Hake Fillets under Modified Atmosphere Packaging Systems during Cold Storage

Fresh ready-to-cook fish fillets are susceptible to loss of freshness and accumulation of off-odour due to accelerated microbial spoilage. Suboptimal storage temperature and packaging conditions accelerate this process, limiting the economic potential. This study investigated the effects of modified atmosphere packaging (MAP) and storage temperature (0 °C and 4 °C) on the volatile compounds (VOCs) of Cape hake (Merluccius capensis) fish fillets as a predictor of shelf life and quality. Fresh Cape hake fillets were packaged under active modified atmosphere (40% CO2 + 30% O2 + 30% N2) and passive modified atmosphere (0.039% CO2 + 20.95% O2 + 78% N2) with or without an absorbent pad and stored at 0 °C and 4 °C for 12 d. The results obtained demonstrated that changes in VOCs and concentration were significantly (p < 0.05) influenced by MAP conditions, storage temperature and duration. A total of 16 volatiles were identified in the packaged Cape hake fillets: 4 primary VOCs and 12 secondary VOCs. The spoilage VOCs identified include tri-methylamine (TMA) (ammonia-like), esters (sickeningly sweet) and sulphur group (putrid). The concentration of secondary VOCs increased continuously during storage. Active-MA-packaged fillets performed better and had lower TMA values of 0.31% at 0 °C on day 12 in comparison to 7.22% at 0 °C under passive on day 6. Ethyl acetate was detected in passive-MA-packaged fillets stored at 0 °C on day 3, and the levels increased to 3.26% on day 6, while active-MA-packaged fillets maintained freshness. This study showed that in conjunction with TMA, VOCs such as esters and sulphur-related compounds could be used as spoilage markers for Cape hake fish fillets.

Dietary Effects of Carotenoid on Growth Performance and Pigmentation in Bighead Catfish (Clarias macrocephalus Günther, 1864)

This study investigates the effects of supplemental carotenoid pigments on growth and color performance in bighead catfish (Clarias macrocephalus). Two experiments were undertaken to determine the appropriate types, feed duration, and dose of astaxanthin (As), canthaxanthin (Ca), and xanthophyll (Xa) pigments individually and in combination. In the first experiment, fish were fed with one control diet (basic diet), six experimental diets comprised of three diets of As, Ca, and Xa at a 100 mg/kg rate of supplementation, respectively, and three diets combinations of As + Ca, As + Xa, and Ca + Xa at a supplement rate of 50 mg + 50 mg/kg. The results showed no significant difference in weight gain (WG), specific growth rate (SGR), survival rate (SR), and feed conversion ratio of fish among treatments (p > 0.05) after 6 weeks. The L* (Lightness) and a* (redness) values in the Xa diet were significantly lower than other treatments, while b* (yellowness) was significantly higher than in the control and others treatments (p < 0.05). These values peaked after 4 weeks and remained stable until the end of the experiment. Consistently, the highest muscle carotenoid content (16.89 ± 0.60 mg/100 g) was found in the fish fed with the Xa diet. The Xa diet was selected for the second experiment. This experiment consisted of four Xa supplemented diets at rates of 25, 50, 75, and 100 mg/kg and a basal diet without any Xa supplementation. The results showed that there was no difference in the SGR or SR of fish fed various Xa levels (p > 0.05). Fish fed the Xa diet of 75 mg/kg were the most preferred by consumers for the natural “yellowness” of muscle. Thus, the results suggested that additional carotenoid pigments did not affect the growth performance of fish. Farmers and feed producers could utilize Xa at an optimal dose of 75 mg/kg to enhance color performance in the market size of bighead catfish for at least 4 weeks prior to harvest.

Applying Fourier Transform Mid Infrared Spectroscopy to Detect the Adulteration of Salmo salar with Oncorhynchus mykiss

The aim of this study was to evaluate the potential of Fourier transform infrared (FTIR) spectroscopy coupled with chemometric methods to detect fish adulteration. Muscles of Atlantic salmon (Salmo salar) (SS) and Salmon trout (Onconrhynchus mykiss) (OM) muscles were mixed in different percentages and transformed into mini-burgers. These were stored at 3 °C, then examined at 0, 72, 160, and 240 h for deteriorative microorganisms. Mini-burgers was submitted to Soxhlet extraction, following which lipid extracts were analyzed by FTIR. The principal component analysis (PCA) described the studied adulteration using four principal components with an explained variance of 95.60%. PCA showed that the absorbance in the spectral region from 721, 1097, 1370, 1464, 1655, 2805, to 2935, 3009 cm⁻¹ may be attributed to biochemical fingerprints related to differences between SS and OM. The partial least squares regression (PLS-R) predicted the presence/absence of adulteration in fish samples of an external set with high accuracy. The proposed methods have the advantage of allowing quick measurements, despite the storage time of the adulterated fish. FTIR combined with chemometrics showed that a methodology to identify the adulteration of SS with OM can be established, even when stored for different periods of time.

Biscuits fortified with micro-encapsulated shrimp oil: characteristics and storage stability

Characteristics and storage stability of biscuits fortified with micro-encapsulated shrimp oil (MSO) were determined. The addition of MSO increased spread ratio, whilst decreased the thickness of biscuit. The highest hardness of biscuit was obtained with addition of 9 or 12% MSO. Biscuit surface showed higher redness and yellowness when MSO was incorporated (p < 0.05). The addition of MSO up to 6% had no adverse effect on biscuit quality and acceptability. When biscuits added with 6% MSO were stored under different illumination conditions (light and dark), lipid oxidation in all samples increased throughout the storage of 12 days. Light accelerated lipid oxidation of biscuits as evidenced by the increases in both peroxide values and abundance of volatile compounds. No marked change in EPA, DHA and astaxanthin contents were noticeable in biscuit fortified with MSO after 12 days of storage. Therefore, the biscuit could be fortified with MSO up to 6% and must be stored in dark to assure its oxidative stability.

Effect of the antioxidants composition in diet on the sensory and physical properties of frozen farmed Coho salmon (Oncorhynchus kisutch)

BACKGROUND

Great attention has been paid to the antioxidants present in farmed fish feeds, with the replacement of synthetic antioxidants by natural ones being a main objective. In the present study, Coho salmon (Oncorhynchus kisutch) was fed a conventional diet that was enriched with different kinds of antioxidants: synthetic antioxidants (butylated-hydroxy toluene and ethoxyquin; diet I), a tocopherols-rich mixture (diet II) and a tocopherols-rosemary extract mixture (diet III). A comparative study of the sensory and physical changes observed in the corresponding frozen products was undertaken.

RESULTS

After 18 months at -18 °C, fish previously fed on diet I showed higher putrid and rancid odours and rancid taste scores, while lower mean typical odour and taste values were attained. Dripping and expressible moisture values obtained for diet II-fish were lower when compared with their counterparts belonging to the diet I; additionally, microstructure analysis revealed that Z-lines integration was better preserved in fish corresponding to diets II and III.

CONCLUSION

Diet II has been recognised as being the most profitable to be employed to maintain the sensory and physical properties of the frozen product when long-term storage is considered. Further research is to be continued to optimise the natural antioxidants profile.

Tomato quality in controlled atmosphere storage, modified atmosphere packaging and cold storage

Effects of controlled atmosphere storage (CAS) and modified atmosphere packaging (MAP) in comparison with conventional cold storage on qualitative properties of green-mature harvested tomato were evaluated. Qualitative properties included firmness, redness value (a*), hue angle, Total Soluble Solids (TSS) content, Titratable Acidity (TA) and TSS/TA. Under CAS and MAP conditions, gas composition was 5 kPa O2 and 3 kPa CO2. Results showed that the ability of CAS and MAP to retard the ripening process was more than cold storage. With regard to maintaining texture and colour, CAS treatment was the best and MAP was better than cold storage. Although amongst storage treatments, the maximum value of TSS was observed in cold storage, its decreasing trend in CAS was slower than that in cold storage. Additionally, MAP and especially CAS slowed down the diminishing trend of TA in tomatoes.