A Novel Genetic Algorithm-Based Optimization Framework for the Improvement of Near-Infrared Quantitative Calibration Models

The global fishmeal production is used for animal feed, and protein is the main component that provides nutrition to animals. In order to monitor and control the nutrition supply to animal husbandry, near-infrared (NIR) technology was utilized for rapid detection of protein contents in fishmeal samples. The aim of the NIR quantitative calibration is to enhance the model prediction ability, where the study of chemometric algorithms is inevitably on demand. In this work, a novel optimization framework of GSMW-LPC-GA was constructed for NIR calibration. In the framework, some informative NIR wavebands were selected by grid search moving window (GSMW) strategy, and then the variables/wavelengths in the waveband were transformed to latent principal components (LPCs) as the inputs for genetic algorithm (GA) optimization. GA operates in iterations as implementation for the secondary optimization of NIR wavebands. In steps of the variable's population evolution, the parametric scaling mode was investigated for the optimal determination of the crossover probability and the mutation operator. With the GSMW-LPC-GA framework, the NIR prediction effect on fishmeal protein was experimentally better than the effect by simply adopting the moving window calibration model. The results demonstrate that the proposed framework is suitable for NIR quantitative determination of fishmeal protein. GA was eventually regarded as an implementable method providing an efficient strategy for improving the performance of NIR calibration models. The framework is expected to provide an efficient strategy for analyzing some unknown changes and influence of various fertilizers.

Natural products with preservative properties for enhancing the microbiological safety and extending the shelf-life of seafood: A review

Seafood is highly perishable, presenting a rapid loss of its quality soon after capture. Temperature is the critical parameter that impacts on seafood shelf-life reduction, allowing the growth of foodborne pathogens and spoilage microorganisms. In recent years, the search by additional methods of preserving seafood has increased, able to ensure quality and safety. Several natural preservatives have highlighted and gained considerable attention from the scientific community, consumers, industry, and health sectors as a method with broad action antimicrobial and generally economical. Natural preservatives, from different sources, have been widely studied, such as chitosan from animal sources, essential oils, and plant extracts from a plant source, lactic acid bacteria, and bacteriocins from microbiological sources and organic acid from different sources, all with great potential for use in seafood systems. This review focuses on the natural preservatives studied in seafood matrices, their forms of application, concentrations usually employed, their mechanisms of action, factors that interfere in their use and the synergistic effect of the interactions among the natural preservatives, with a focus for maintenance of quality and ensure of food safety.

Predictive Modeling of the Effect of ε-Polylysine Hydrochloride on Growth and Thermal Inactivation of Listeria monocytogenes in Fish Balls

This study aimed to evaluate the effect of ε-polylysine hydrochloride (ε-PLH) on the growth and thermal inactivation kinetics of Listeria monocytogenes in fish balls. Samples, supplemented with ε-PLH (0, 150, or 300 ppm, w/w), were inoculated with a three-strain cocktail of L. monocytogenes and incubated at constant temperatures of 3.4, 8, 12, or 16 °C for growth studies, or heated at 60, 62.5, 65, or 67.5 °C for thermal inactivation tests. The growth curves were fitted to the Huang primary model, and the Huang and Ratkowsky square-root models (SRM) were used as the secondary models to evaluate the effect of temperature on bacterial growth. The survival during heating was analyzed with a log-linear model. The results showed that, while the lag time of L. monocytogenes was affected by both ε-PLH concentration and temperature, the specific growth rate was unaffected by ε-PLH. Under the same temperature, a 10-time in increase of the lag time would be expected for every 565 ppm in the increase of ε-PLH concentration. Using the Ratkowsky SRM, the estimated nominal minimum growth temperature was -2.04 °C, while the minimum growth temperature was 0.29 °C when estimated with the Huang SRM. Validation at 10 °C showed that the Huang primary model, in combination with either the Huang or Ratkowsky SRM, could accurately predict the growth of L. monocytogenes. On the other hand, the thermal resistance of the pathogen was significantly reduced by increase in temperature or ε-PLH. The thermal z value of L. monocytogenes was 5.78 °C, and the ε-PLH z value was 1642 ppm. The results of this study showed that the combined application of ε-PLH and temperature can be used to control L. monocytogenes in fish balls and to improve food safety and reduce risks to public health.

Quality changes and shelf-life extension of ready-to-eat fish patties by adding encapsulated citric acid

BACKGROUND

Citric acid is commonly used as a flavoring and preservative in food and beverages. The effect of adding citric acid directly or encapsulated (each at 1 and 2 g kg^-1 ) on the quality and shelf-life of ready-to-eat sea bass patties was evaluated during storage at 4 °C in vacuum skin packaging.

RESULTS

Microbial growth and total basic volatile nitrogen were maintained at relatively low levels up to 8 weeks of storage. With respect to oxidative stability, the addition of encapsulated citric acid minimized secondary oxidation values more efficiently than its direct addition, regardless of the concentration. This is in agreement with the decreased fishy odor observed in those patties containing encapsulated citric acid. Accordingly, sensory analysis showed that the addition of encapsulated citric acid at 1 g kg^-1 resulted in lower scores in fish aroma compared to that of the control. Sourness is dependent on the amount of citric acid added, regardless of the form (direct or encapsulated).

CONCLUSIONS

The form of citric acid addition, rather than the amount of citric acid added, caused changes in texture. Therefore, the use of encapsulated citric acid represents a suitable strategy that is of great interest in the seafood industry. © 2017 Society of Chemical Industry.

Microbial chitosan as a biopreservative for fish sausages

Processed fish products are worthy sources to supply man with his main nutritional needs, but they are extremely susceptible to quality loss during storage. Microbial (fungal) chitosan is a bioactive polymer that has numerous applications in health promoting fields. Fungal chitosan was extracted from the grown mycelia of Aspergillus brasiliensis (niger) to investigate its potential role as antimicrobial, preservative and quality improvement agent, in processed fish sausages from Nile tilapia (Oreochromis niloticus). The produced chitosan had a molecular weight of 29kDa, deacetylation degree of 91% and solubility of 99% in acetic acid solution. Fish sausages supplementation with 1.5% chitosan resulted in sharp reductions of microbial load (Total aerobic microorganisms, coliforms, yeast & molds, E. coli, Enterobacteriaceae and Staphylococcus aureus) during cold storage, at 4°C for 28days. Sensory attributes were notably enhanced in stored chitosan-supplemented sausages, especially the odor and taste characteristics. Captured micrographs, of exposed S. aureus to chitosan, exhibited vigorous morphological alterations after 4h, and complete cell lysis after 8h of exposure period. A. brasiliensis chitosan, however, could be strongly recommended, as a supplement for Nile tilapia fish sausages, to maintain microbiological quality and enhance sensory attributes of the product during storage.