Recent Advances in Minimal Heat Processing of Fish: Effects on Microbiological Activity and Safety

Applying innovative technological interventions in the preservation and packaging of fresh seafood products to minimize spoilage - A systematic review and meta-analysis

Seafood, being highly perishable, faces rapid deterioration in freshness, posing spoilage risks and potential health concerns without proper preservation. To combat this, various innovative preservation and packaging technologies have emerged. This review delves into these cutting-edge interventions designed to minimize spoilage and effectively prolong the shelf life of fresh seafood products. Techniques like High-Pressure Processing (HPP), Modified Atmosphere Packaging (MAP), bio-preservation, and active and vacuum packaging have demonstrated the capability to extend the shelf life of seafood products by up to 50%. However, the efficacy of these technologies relies on factors such as the specific type of seafood product and the storage temperature. Hence, careful consideration of these factors is essential in choosing an appropriate preservation and packaging technology.

Selenium in Infants and Preschool Children Nutrition: A Literature Review

Selenium (Se), an essential trace element, is fundamental to human health, playing an important role in the formation of thyroid hormones, DNA synthesis, the immune response, and fertility. There is a lack of comprehensive epidemiological research, particularly the serum Se concetration in healthy infants and preschool children compared to the estimated dietary Se intake. However, Se deficiencies and exceeding the UL have been observed in infants and preschool children. Despite the observed irregularities in Se intake, there is a lack of nutritional recommendations for infants and preschool children. Therefore, the main objective of this literature review was to summarize what is known to date about Se levels and the risk of deficiency related to regular consumption in infants and preschool children.

Mild processing of seafood-A review

Recent years have shown a tremendous increase in consumer demands for healthy, natural, high-quality convenience foods, especially within the fish and seafood sector. Traditional processing technologies such as drying or extensive heating can cause deterioration of nutrients and sensory quality uncompilable with these demands. This has led to development of many novel processing technologies, which include several mild technologies. The present review highlights the potential of mild thermal, and nonthermal physical, and chemical technologies, either used alone or in combination, to obtain safe seafood products with good shelf life and preference among consumers. Moreover, applications and limitations are discussed to provide a clear view of the potential for future development and applications. Some of the reviewed technologies, or combinations thereof, have shown great potential for non-seafood products, yet data are missing for fish and seafood in general. The present paper visualizes these knowledge gaps and the potential for new technology developments in the seafood sector. Among identified gaps, the combination of mild heating (e.g., sous vide or microwave) with more novel technologies such as pulsed electric field, pulsed light, soluble gas stabilization, cold plasma, or Ohmic heat must be highlighted. However, before industrial applications are available, more research is needed.

Effects of Vacuum Frying on the Preparation of Ready-to-Heat Batter-Fried and Sauced Chub Mackerel (Scomber japonicus)

Chub mackerel (CM) is a commercial fish in Korea, owing to its availability and nutritional values. This study aimed to develop a ready-to-heat (RTH) Korean preparation of CM, known as Godeungo gangjeong. We utilized vacuum frying technology to fry the CM and evaluated its quality. Conventional frying with a deep fryer was performed in parallel to assess the superiority of the vacuum fryer. We optimized the frying conditions of vacuum frying (VBF) and deep frying (DBF) using response surface methodology. At optimum conditions of 95 °C for 7 min 42 s, VBF produced better sensory, chemical, and microbial properties than DBF at 190 °C for 5 min 30 s. The nutritional values, including amino acid and fatty acid contents, were investigated and found to be higher in VBF than in DBF. Sensory properties also showed better scores on VBF than DBF, especially in appearance, aroma, taste, and overall acceptability. The VBF produced lower volatile basic nitrogen (VBN), thiobarbituric acid reactive substances (TBARS), and total bacterial count (TBC) than DBF. The findings confirmed that vacuum frying is a better option to produce RTH Godeungo gangjeong, since it provides less oxidation and maintains the product quality. Using the Arrhenius approach, the product was concluded to preserve both quality and safety for 9 months of storage at −18 °C.

Diversity and Antimicrobial Activity towards Listeria spp. and Escherichia coli among Lactic Acid Bacteria Isolated from Ready-to-Eat Seafood

Biopreservation is a food preservation technology using microorganisms and/or their inherent antimicrobial metabolites to inhibit undesirable microorganisms. The aim of the present study was to explore the diversity and antimicrobial activity of lactic acid bacteria (LAB) strains (n = 99) isolated from ready-to-eat (RTE) seafood (cold-smoked salmon (CSS), gravlax, and sushi) towards two strains of Listeria monocytogenes (CCUG 15527, F11), Listeria innocua (CCUG 15531) and Escherichia coli (CCUG 38079). The LAB strains were assigned to five different genera (Carnobacterium spp., Lactobacillus spp., Leuconostoc spp., Weissella spp., and Enterococcus sp.) by sequencing a 1150 bp stretch of the 16S rRNA gene. A significant association between the seafood source and the distribution of LAB genera was found (p < 0.001), of which Leuconostoc spp. were most prevalent in sushi and Carnobacterium sp. and Lactobacillus sp. were most frequently isolated from CSS and gravlax. Antimicrobial activity among the LAB was significantly affected by LAB genera (F= 117.91, p < 0.001, one-way ANOVA), product of origin (F = 3.47, p < 0.05), and target (F = 4.64, p = 0.003). LAB isolated from sushi demonstrated a significantly higher antimicrobial effect than LAB from CSS and gravlax (p < 0.05). In general, a significantly higher antimicrobial activity was found towards Listeria spp. than E. coli (p < 0.05). However, Leuconostoc spp. demonstrated similar antimicrobial effects towards E. coli and Listeria spp., except for L. monocytogenes F11 being more sensitive (p < 0.05). This study suggested that seafood-derived LAB strains could be selected for technological application in RTE seafood systems.

Monitoring Thermal and Non-Thermal Treatments during Processing of Muscle Foods: A Comprehensive Review of Recent Technological Advances

Muscle food products play a vital role in human nutrition due to their sensory quality and high nutritional value. One well-known challenge of such products is the high perishability and limited shelf life unless suitable preservation or processing techniques are applied. Thermal processing is one of the well-established treatments that has been most commonly used in order to prepare food and ensure its safety. However, the application of inappropriate or severe thermal treatments may lead to undesirable changes in the sensory and nutritional quality of heat-processed products, and especially so for foods that are sensitive to thermal treatments, such as fish and meat and their products. In recent years, novel thermal treatments (e.g., ohmic heating, microwave) and non-thermal processing (e.g., high pressure, cold plasma) have emerged and proved to cause less damage to the quality of treated products than do conventional techniques. Several traditional assessment approaches have been extensively applied in order to evaluate and monitor changes in quality resulting from the use of thermal and non-thermal processing methods. Recent advances, nonetheless, have shown tremendous potential of various emerging analytical methods. Among these, spectroscopic techniques have received considerable attention due to many favorable features compared to conventional analysis methods. This review paper will provide an updated overview of both processing (thermal and non-thermal) and analytical techniques (traditional methods and spectroscopic ones). The opportunities and limitations will be discussed and possible directions for future research studies and applications will be suggested.

Spectroscopic Techniques for Monitoring Thermal Treatments in Fish and Other Seafood: A Review of Recent Developments and Applications

Cooking is an important processing method, that has been used since ancient times in order to both ensure microbiological safety and give desired organoleptic properties to the cooked food. Fish and other seafood products are highly sensitive to thermal treatments and the application of severe heat can result in negative consequences on sensory and nutritional parameters, as well as other quality attributes of the thermally processed products. To avoid such undesired effects and to extend the shelf life of these perishable products, both the heat processing methods and the assessment techniques used to monitor the process should be optimized. In this review paper, the most common cooking methods and some innovative ones will first be presented with a brief discussion of their impact on seafood quality. The main methods used for monitoring heat treatments will then be reviewed with a special focus on spectroscopic techniques, which are known to be rapid and non-destructive methods compared to traditional approaches. Finally, viewpoints of the current challenges will be discussed and possible directions for future applications and research will be suggested. The literature presented in this review clearly demonstrates the potential of spectroscopic techniques, coupled with chemometric tools, for online monitoring of heat-induced changes resulting from the application of thermal treatments of seafood. The use of fluorescence hyperspectral imaging is especially promising, as the technique combines the merits of both fluorescence spectroscopy (high sensitivity and selectivity) and hyperspectral imaging (spatial dimension). With further research and investigation, the few current limitations of monitoring thermal treatments by spectroscopy can be addressed, thus enabling the use of spectroscopic techniques as a routine tool in the seafood industry.

Experimental analysis and modeling of ultrasound assisted freezing of potato spheres

In recent years, innovative methods such as ultrasound assisted freezing have been developed in order to improve the freezing process. During freezing of foods, accurate prediction of the temperature distribution, phase ratios, and process time is very important. In the present study, ultrasound assisted immersion freezing process (in 1:1 ethylene glycol-water solution at 253.15K) of potato spheres (0.02 m diameter) was evaluated using experimental, numerical and analytical approaches. Ultrasound (25 kHz, 890 W m(-2)) was irradiated for different duty cycles (DCs=0-100%). A finite volume based enthalpy method was used in the numerical model, based on which temperature and liquid fraction profiles were simulated by a program developed using OpenFOAM® CFD software. An analytical technique was also employed to calculate freezing times. The results showed that ultrasound irradiation could decrease the characteristic freezing time of potatoes. Since ultrasound irradiation increased the heat transfer coefficient but simultaneously generated heat at the surface of the samples, an optimum DC was needed for the shortest freezing time which occurred in the range of 30-70% DC. DCs higher than 70% increased the freezing time. DCs lower than 30% did not provide significant effects on the freezing time compared to the control sample. The numerical model predicted the characteristic freezing time in accordance with the experimental results. In addition, analytical calculation of characteristic freezing time exhibited qualitative agreement with the experimental results. As the numerical simulations provided profiles of temperature and water fraction within potatoes frozen with or without ultrasound, the models can be used to study and control different operation situations, and to improve the understanding of the freezing process.

Rapid and non-destructive determination of drip loss and pH distribution in farmed Atlantic salmon (Salmo salar) fillets using visible and near-infrared (Vis-NIR) hyperspectral imaging

Drip loss and pH are important indices in quality assessment of salmon products. This work was carried out for rapid and non-destructive determination of drip loss and pH distribution in salmon fillets using near-infrared (Vis-NIR) hyperspectral imaging. Hyperspectral images were acquired for salmon fillet samples and their spectral signatures in the 400-1700nm range were extracted. Partial least square regression (PLSR) was used to correlate the spectra with reference drip loss and pH values. Important wavelengths were selected using the regression coefficients method to develop new PLSR models, leading to a correlation coefficient of cross-validation (rCV) of 0.834 with root-mean-square errors by cross-validation (RMSECV) of 0.067 for drip loss and a rCV of 0.877 with RMSECV of 0.046 for pH, respectively. Distribution maps of drip loss and pH were generated based on the new PLSR models using image processing algorithms. The results showed that Vis-NIR hyperspectral imaging technique combined with PLSR calibration analysis offers an effective quantitative capability for determining the spatial distribution of drip loss and pH in salmon fillets.

The effect of ultrasound irradiation on the convective heat transfer rate during immersion cooling of a stationary sphere

It has been proven that ultrasound irradiation can enhance the rate of heat transfer processes. The objective of this work was to study the heat transfer phenomenon, mainly the heat exchange at the surface, as affected by ultrasound irradiation around a stationary copper sphere (k=386W m(-1)K(-1), C(p)=384J kg(-1)K(-1), ρ=8660kg m(-3)) during cooling. The sphere (0.01m in diameter) was immersed in an ethylene glycol-water mixture (-10°C) in an ultrasonic cooling system that included a refrigerated circulator, a flow meter, an ultrasound generator and an ultrasonic bath. The temperature of the sphere was recorded using a data logger equipped with a T-type thermocouple in the center of the sphere. The temperature of the cooling medium was also monitored by four thermocouples situated at different places in the bath. The sphere was located at different positions (0.02, 0.04 and 0.06m) above the transducer surface of the bath calculated considering the center of the sphere as the center of the reference system and was exposed to different intensities of ultrasound (0, 120, 190, 450, 890, 1800, 2800, 3400 and 4100W m(-2)) during cooling. The frequency of the ultrasound was 25kHz. It was demonstrated that ultrasound irradiation can increase the rate of heat transfer significantly, resulting in considerably shorter cooling times. Higher intensities caused higher cooling rates, and Nu values were increased from about 23-27 to 25-108 depending on the intensity of ultrasound and the position of the sphere. However, high intensities of ultrasound led to the generation of heat at the surface of the sphere, thus limiting the lowest final temperature achieved. An analytical solution was developed considering the heat generation and was fitted to the experimental data with R(2) values in the range of 0.910-0.998. Visual observations revealed that both cavitation and acoustic streaming were important for heat transfer phenomenon. Cavitation clouds at the surface of the sphere were the main cause of heating effect. The results showed that closer distances to the transducer surface showed higher cooling rates. On the other hand, despite having a bigger distance from the transducer, when the sphere was located close to the gas-liquid interface the enhancement factor of heat transfer was higher. Ultrasound irradiation showed promising effect for the enhancement of convective heat transfer rate during immersion cooling. More investigations are required to demonstrate the behavior of ultrasound assisted heat transfer and resolve the proper way of the application of ultrasound to assist the cooling and/or freezing processes.

Evaluation of thermal inactivation of Escherichia coli using microelectrode ion flux measurements with osmotic stress

AIMS

To elucidate the potential use of microelectrode ion flux measurements to evaluate bacterial responses to heat treatment.

METHODS AND RESULTS

Escherichia coli K12 was used as a test bacterium to determine whether various heat treatments (55-70°C for 15 min) affected net ion flux across E. coli cell membranes using the MIFE™ system to measure net K(+) fluxes. No difference in K(+) fluxes was observed before and after heat treatments regardless of the magnitude of the treatment. Applying hyperosmotic stress (3% NaCl w/v) during flux measurement led to a net K(+) loss from the heat-treated E.coli cells below 65°C as well as from nonheated cells. In contrast, with E. coli cells treated at and above 65°C, hyperosmotic stress disrupted the pattern of K(+) flux observed at lower temperatures and resulted in large flux noise with random scatter. This phenomenon was particularly apparent above 70°C. Although E. coli cells lost the potential to recover and grow at and above 62°C, K(+) flux disruption was not clearly observed until 68°C was reached.

CONCLUSIONS

No changes in net K(+) flux from heat-stressed E. coli cells were observed directly as a result of thermal treatments. However, regardless of the magnitude of heat treatment above 55°C, loss of viability indicated by enrichment culture correlated with disrupted K(+) fluxes when previously heated cells were further challenged by imposing hyperosmotic stress during flux measurement. This two-stage process enabled evaluation of the lethality of heat-treated bacterial cells within 2 h and may be an alternative and more rapid method to confirm the lethality of heat treatment.

SIGNIFICANCE AND IMPACT OF THE STUDY

The ability to confirm the lethality of thermal treatments and to specify minimal time/temperature combinations by a nonculture-dependent test offers an alternative system to culture-based methods.