Chemical and microbial analyses of squid muscle (Loligo plei) during storage in ice

Effects of curing concentration and drying time on flavor and microorganisms in dry salted Spanish mackerel

This study investigated the quality changes of dry salted mackerel during curing and drying process and the relationship between flavor substances and microorganisms. The results showed that the thiobarbituric acid reactive substances (TBARS) values increased gradually with the increase of salt concentration and treatment time. The total volatile base nitrogen (TVB-N) values and total viable counts (TVC) values showed the same trend. Under 3% condition, the TVB-N values exceeded the standard and was not suitable for consumption. A total of 61 volatile flavor substances were identified by Gas chromatography-ion mobility spectrometry (GC-IMS), among which aldehydes contributed the most. Staphylococcus and Cobetia were the most abundant by High-throughput sequencing (HTS). There was significant correlation between TOP15 microorganisms and TOP20 flavor substances. Staphylococcus and Cobetia were positively correlated with 13 volatile flavor substances, which contributed to the formation of flavor in naturally fermented Spanish mackerel.

Squid industry by-product hydrolysate supplementation enhances growth performance of Penaeus monodon fed plant protein-based diets without fish meal

The poor growth of aquatic animals fed with diets containing high plant proteins has been attributed to low diet acceptability and feed value. Supplementation of protein hydrolysate, with high contents of free amino acids and soluble low molecular weight peptides, may increase the acceptability and feed value of a plant protein-based diet. In the present work, squid processing by-products were enzymatically hydrolyzed and used as a supplement in a plant protein-based diet, without fish meal, of Penaeus monodon to fully maximize the utilization of this marine resource. The hydrolysate was incorporated at 0, 0.5, and 1% levels in P. monodon diets containing 0 and 10% fish meal levels. Growth, digestive enzyme activities, muscle growth-, gut pro-inflammatory and immune-related gene expressions, and muscle morphometric measurements were evaluated as biological indices in an 8-week feeding trial. The squid by-product hydrolysate produced in the present study contains 90.25% protein, 5.84% lipid, and 3.91% ash, and has a molecular weight of 3.76 kDa. Supplementation at 1% hydrolysate in the experimental shrimp diet without fish meal resulted in the highest growth performance associated with increased feed intake, efficient feed and nutrient conversion and retention, enhanced digestive enzyme activities, upregulation of muscle growth- and immune-related genes, and suppression of the gut pro-inflammatory gene. The growth promotion is also linked with a significant increase in muscle mean fiber area, which suggests hypertrophic growth in shrimp. Generally, the supplementation of 1% squid by-product hydrolysate supported the growth of P. monodon fed on a plant protein-based diet without fish meal.

Rapid and non-destructive freshness evaluation of squid by FTIR coupled with chemometric techniques

BACKGROUND

Freshness is an important quality of squid with respect to determining the market price. The methods of evaluation of freshness fail to be widely used as a result of the lack of rapidity and quantitation. In the present study, a rapid and non-destructive quantification of squid freshness by Fourier transform infrared spectroscopy (FTIR) spectra combined with chemometric techniques was performed.

RESULTS

The relatively linear content change of trimethylamine (TMA-N) and dimethylamine (DMA-N) of squid during storage at 4 °C indicated their feasibility as a freshness indicator, as also confirmed by sensory evaluation. The spectral changes were mainly caused by the degradation of proteins and the production of amines by two-dimensional infrared correlation spectroscopy, among which TMA-N, DMA-N and putrescine were the main amines. The successive projections algorithm (SPA) was employed to select the sensitive wavenumbers to freshness for modeling prediction including partial least-squares regression, support vector regression (SVR) and back-propagation artificial neural network. Generally, the SPA-SVR model of the selected characteristic wavenumber showed a higher prediction accuracy for DMA-N (R² _P  = 0.951; RMSE_P  = 0.218), whereas both SPA-SVR (R² _P  = 0.929; RMSE_P  = 2.602) and Full-SVR (R² _P  = 0.941; RMSE_P  = 2.492) models had a higher predictive ability of TMA-N.

CONCLUSION

The results of the present study demonstrate that FTIR spectroscopy coupled with multivariate calibration shows significant potential for the prediction of freshness in squid. © 2021 Society of Chemical Industry.

Quality changes of sous-vide cooked and blue light sterilized Argentine squid (Illex argentinus)

The present work was carried out to investigate the quality changes and shelf life of blue light (Blu-ray) irradiated sous-vide cooked (SVC) Argentine squid (Illex argentinus) during storage at 0, 5, and 10 °C. Sensory evaluation, color, shear force, lipid oxidation levels, total viable counts (TVC), and psychrophilic bacterial count were used to study the changes in storage quality of SVC squid at different temperatures. Results showed that the high-quality endpoints of Blu-ray irradiated Argentine squid were 360, 144, and 72 h, and the shelf-life endpoints were 504, 240, and 120 h during storage at 0, 5, and 10 ℃, respectively. The redness values of irradiated squid did not differ significantly (p >0.05) during the storage, the brightness and yellowness values of irradiated squid showed an increasing trend, and the sheer force initially increased and then decreased. The thiobarbituric acid reactive substance of each squid stored at low temperature increased with the extension of the storage period, indicating that they exhibited fat oxidation with the extension of the storage period. The TVC and the number of Psychrobacter species increased with the storage period. The correlation analysis suggested that TVC and Psychrobacter count as indicators of quality changes in Argentine squid during low-temperature storage were in good agreement with sensory scores (R2 >0.9). Additionally, our results showed that Blu-ray sterilization played a positive role by inducing photosensitive oxidation and decreasing TVC and the total number of Psychrobacter than the control group during storage of SVC squid after Blu-ray irradiation. This study provides a theoretical basis for applying Blu-ray sterilization in aquatic product processing.

Development of a colorimetric sensor array for squid spoilage assessment

The aim of this work was to develop and evaluate a rapid, easy-to-use optoelectronic system for the shelf-life assessment of squid in cold storage. For this purpose, an optoelectronic nose was designed, which consisted of an array containing six sensing materials prepared by combining different dyes and two inorganic supports (aluminium oxide and silica gel). Samples were packaged with the colorimetric array and kept in cold storage for 12 days. Squid spoilage was monitored simultaneously by the colorimetric array and by the physico-chemical and microbial analyses during storage. Samples exceeded the acceptability limits for microbial counts on the third day. PCA analysis carried out with CIELab showed that the colorimetric array was able to discriminate between fresh squid fit for consumption and spoiled squid. The statistical models obtained by PLS, with the optoelectronic nose, successfully predicted CO2 and O2 content in the headspace as well as microbial growth.

Study of chemical properties and evaluation of collagen in mantle, epidermal connective tissue and tentacle of Indian Squid, Loligo duvauceli Orbigny

The chemical composition and evaluation of Indian squid (Loligo duvauceli) mantle, epidermal connective tissue and tentacle is investigated in this current study. It is observed that squid mantle contains 22.2% total protein; 63.5% of the total protein is myofibrillar protein. The unique property of squid myofibrillar protein is its water solubility. Squid mantle contains 12.0% total collagen. Epidermal connective tissue has highest amounts of total collagen (17.8%). SDS-PAGE of total collagen identified high molecular weight α-, β- and γ- sub-chains. Amino acid profile analysis indicates that mantle and tentacle contain essential amino acids. Arginine forms a major portion of mantle collagen (272.5 g/100 g N). Isoleucine, glutamic acid and lysine are other amino acids that are found in significantly high amounts in the mantle. Sulphur containing cystine is deficit in mantle collagen. Papain digest of mantle and epidermal connective tissue is rich in uronic acid, while papain digest, collagenase digest and urea digest of epidermal connective tissue has significant amounts of sialic acid (25.2, 33.2 and 99.8 μmol /100 g, respectively). PAS staining of papain digest, collagenase digest and urea digest also identify the association of hexoses with low molecular weight collagen fragments. Histochemical sectioning also emphasized the localized distribution of collagen in epidermal and dermal region and very sparse fibres traverse the myotome bundles.

ATPase inhibitor based luciferase assay for prolonged and enhanced ATP pool measurement as an efficient fish freshness indicator

The nucleotide degradation pathway in somatic cells leads to the accumulation of products such as hypoxanthine and inosine, which are commonly used as fish and meat freshness indicators. Assays based on these molecules cannot differentiate the postmortem time over a short period of time (5-10 h). Further, quantification of these degradation products is cumbersome, costly and time-consuming. For the proposed assay, optimal concentrations of 30 and 2 mM, respectively, for the ATPase inhibitors sodium orthovanadate and EDTA were found. Further, it was observed that a firefly luciferase based assay could enhance the sensitivity levels up to 165-fold at 30 °C. In addition, it was observed that the sensitivity for ATP assay was enhanced up to 60-fold even after 12 h. The limit of detection for the ATP assay was 1 pM, unlike other conventional methods, which are sensitive only up to micromolar levels. Moreover, as little as 0.044 g fish fillet was required for the assay, and no time-consuming sample preparation was necessary. Luminescence of prolonged duration was observed in harvested fish kept at -20 °C in comparison with fish kept at 4 and 30 °C, which reflects the shelf life of fish preserved at lower temperatures.

Relationship between tissue structural collapse and disappearance of flesh transparency during postmortem changes in squid mantles

This study evaluated the relationship between squid flesh transparency and muscle tissue microstructure. Squid mantle muscle was stored at 4 degrees C after being transported for 2 h by 4 different transportation methods used commonly in Japan (Group 1: live squid packed in ice-cold seawater; Group 2: live squid packed at 4 degrees C; Group 3: squid killed immediately after harvest and packed at 4 degrees C; Group 4: live squid packed in a fish tank containing seawater). Parameters of muscle tissue transparency were measured by an image analysis of digital images of squid muscle tissue. The mantle muscle tissue was observed under a transmission electron microscope to determine the postmortem structural changes at the cellular level. The ATP content of muscle tissue and rupture energy of squid flesh were also measured. As a result, the transparency of squid flesh and the ATP content of the muscles showed the same pattern of change in degree as time passed. The values of these parameters were highest in the group of squid killed immediately followed in order by those transported live, the refrigerated squid, and squid stored in ice-cold seawater. The mantle muscle tissue started to lose its transparency when the ATP in the muscle tissue started to decline. Disintegration of squid muscle tissue structure at the cellular level during storage under refrigeration for 24 h (4 degrees C) was observed in all methods of transportation. This suggested that destruction of the squid muscle tissue structure by autolysis is remarkably fast. The muscle tissue structure disintegrates due to decomposition of the muscle proteins, and muscle transparency is lost because the entire muscle develops a mixed coarse-minute structure.