Study of moisture and salt transfers during salting of sardine fillets

Effect of Fishing Season and Size on the Physicochemical and Microbiological Characteristics of Salted Sardines (Sardina pilchardus)

Salting is the preferred method used by manufacturers to preserve the quality of fish. The aim of this study was to investigate the effect of size and fishing season on the physicochemical and microbiological characteristics of sardines. Two batches of sardines, caught, in winter and summer, were sorted according to size, salted, matured, and stored at 18°C. A control batch, consisting of sardines from the summer batch, was also prepared without subcutaneous fat. Various physicochemical and microbiological parameters were monitored during 12 weeks of maturation. The recorded values showed a decrease in pH, moisture content, and water activity (a measure of the water available for biological and chemical processes), while salt concentration increased. When comparing samples, the lowest values for histamine (94.3 and 48.3 mg/kg) and lipids (9.3 and 8.2%) were observed in the large and small sardines of the winter batch, respectively. In the summer batch, higher values were recorded for histamine (847.3 and 127.9 mg/kg) and lipids (14.5 and 8.6%) in the large and small sardines. Furthermore, the removal of fat in control of the summer batch resulted in lower histamine accumulation compared to the batch with fat. The microbiological parameters showed a decrease in the number of nonhalophile bacteria, while the number of halophile bacteria increased. This study showed a strong correlation between three important factors, fishing season, fish size, and histamine content, which can contribute to the successful salting of sardines and ensure the wholesomeness of the final product.

Influence of salt concentration on Kimchi cabbage (Brassica rapa L. ssp. pekinensis) mass transfer kinetics and textural and microstructural properties during osmotic dehydration

The effect of salt concentration (3%, 6%, and 9%) on the mass transfer kinetics of Kimchi cabbage during osmotic dehydration was investigated, including its influence on textural and microstructural properties and salt distribution. First, kinetics was analyzed using diffusion theory to determine the impact of the factors on moisture and salt transfer. Subsequently, using the Peleg, Azuara, Henderson-Pabis, and Page models, mathematical modeling of mass transfer (water loss and salt gain) was investigated. According to the statistical analysis, the Peleg model provided the best fit for the experimental results under the operating conditions. In addition, a novel viewpoint was proposed in which the salt content of Kimchi cabbage may be indirectly forecasted by monitoring solution salinity during osmotic dehydration. Higher salt concentration resulted in decreased hardness, gumminess, and chewiness in Kimchi cabbage. Scanning electron microscopy and energy-dispersive X-ray mapping images showed an intensification of moisture and salt transport with increasing salt content, which were confirmed using modeling studies. The results could be applied in the prediction of the target salinity of Kimchi cabbage during the salting process and could facilitate the improvement of final Kimchi product quality by producing salted Kimchi cabbage with uniform salinity.

Effects of Pulsed Pressure Curing on Beef Quality

The study was proposed to investigate the effects of pulsed pressure curing on the beef absorption of the curing solution, cooking loss, moisture content, centrifugal loss, salt content, sensory attributes, texture, microstructures and volatile compounds. Curing methods include the following four treatments: (1) control group 1-static curing (SC); (2) control group 2-vacuum curing (VC); (3) control group 3-pressurized curing (PC); and (4) treatment group-pulsed pressure curing (PPC). The acquired results revealed that pulsed pressure curing significantly boosts the curing efficiency and moisture content, decreases cooking loss in beef, brightens meat color, and enhances texture compared to static curing, vacuum curing, and pressurized curing. Additionally, centrifugal losses were not impaired, and sensory findings revealed that PPC significantly improved the saltiness of beef. TPA results showed that the springiness and cohesiveness of PPC were greatly increased, and hardness and chewiness were significantly reduced. Moreover, PPC significantly reduced the content of 1-octen-3-ol and 1-hexanol. Scanning electron microscopy (SEM) images documented that pulsed pressure curing can effectively increase the tenderness of beef. This study demonstrates that processed meat product efficiency and sensory attributes should be taken into account when selecting a curing technique, and the PPC technique has an advantage in both areas.

Mass transfer enhancement of tuna brining with different NaCl concentrations assisted by ultrasound

The influence of different NaCl concentrations (2.5, 5, 7.5 and 10% (w/w)) on the mass transfer kinetics of tuna during brining process with and without ultrasound assistance was evaluated. Results showed that an increase in NaCl concentration and the application of ultrasound accelerated the salt diffusion in the tuna muscle, and the highest yield was obtained in 5% brine concentration. Moreover, the kinetics parameters were significantly affected by the NaCl concentration and ultrasound application during brining. The values of the mass transfer kinetics parameters (k₁, k₂) for total and water weight changes decreased as NaCl concentration increased with and without ultrasound assistance during brining. In contrast, the higher the NaCl concentration, the higher the value of the salting kinetics parameters for salt weight changes. The application of ultrasound enhanced the salt effective diffusion coefficient (De) from 402.8% to 653.21% during the brining process, and the highest De was also found at 5% brine concentration. The application of ultrasound can improve the uniformity of salt distribution, enhance water holding capacity, reduce hardness and chewiness, but have no significant effect on color of tuna muscle.

Effect of a moderate electric field on the salting of Atlantic Salmon (Salmo salar): An experimental study and phenomenological understanding

Salting is one of the oldest methods of preserving food. The main limitation of salting is its extended processing time due to slow salt diffusion. A moderate electric field (MEF) can improve the mass transfer rate through electroporation. Regularly, mass transfer processes are modeled with Fick's second law. However, due to the anisotropic nature of food microstructures, it might be more appropriate to use an anomalous model. The main objective of this study was to search for a phenomenological explanation for salt and water diffusion in the salmon brining process coupled with MEF. Salmon fillets were cut into finite cylinders (0.025 × 0.025 m) and brined in two salt concentrations (6 and 24% w/w NaCl) at 6 °C for 20 h. MEFs were applied in the range of 0 to 2 V/cm. The salt and water contents of the salmon were measured during the process. Fick's second law and anomalous model based on fractional calculus were used to describe the diffusion phenomena. The results showed that an MEF tended to reduce the brining processing time and increase the salt content of salmon. This effect is predominantly due to an increase in the equilibrium salt concentration in the salmon tissue. Mathematical analysis shows that the anomalous diffusion model is more suitable for representing the brining process, exhibiting superdiffusion behavior (α > 1). An MEF accelerates the salt mass transfer into salmon tissue even at lower temperatures, significantly reducing the processing time. In addition, the diffusion process can be characterized with an anomalous model.

Mathematical modeling of thin layer microwave drying of Jaya fish (Aspidoparia jaya)

The effect of microwave power levels on the drying attributes of Jaya fish (Aspidoparia jaya) in a microwave dryer was investigated in this study. Microwave power levels of 100, 180, 300, and 450 W were used to dry 50 g of fish samples, and the drying kinetics were evaluated. Higher microwave power levels resulted in faster drying when increased from 100 to 450 W. The moisture ratio of fish during drying was calculated, and the data obtained were applied to 5 well known thin-layer mathematical models of drying, namely Approximate diffusion, Modified Henderson and Pabis, Two-Term, Logarithmic, and Midilli et al. model. Model constants and coefficients were calculated by nonlinear regression techniques. All the models were validated using statistical parameters namely; Coefficient of determination (R²), Root Mean Square Error (RMSE), Chi-square (χ²), and Standard Sum of Error (SSE). The Midilli et al. model gave an excellent fit to the experimental data of all the models evaluated. The effective diffusivity was calculated using Fick's diffusion equation, and the value varied from 1.40 × 10^-9 to 1.08 × 10^-8 m²/s. The activation energy and the diffusivity constant were found to be 4.656W/g and 1.22 × 10^-8 m²/s, respectively.

Effects of abdominal emptying and immersion in salt in different concentrations on fatty acids profile and spoilage indices of fish Kotr (Sphyraena jello) during freezing

Many studies showed that the nutritional value and the fish spoilage changed during handle and processing. In this research, 20 pieces of the Kotr fish were purchased from Behbahan market. After washing the fish, some as whole fish were frozen (sample A) and some were descaled and emptied and without salt frozen (sample B) and some were immersed in saltwater with 4% concentrations (sample C), 8% (sample D) and 12% (sample E) which then frozen. After 30 days of freezing, samples were transferred to the laboratory to measure fatty acids profile, spoilage indices, proximate composition, and microbial load. The results showed that the percentage of saturated fatty acids in whole fish was significantly lower than the other treatments. However, the percentage of omega-3, omega-6, and MUFA and PUFA fatty acids in different samples did not show a significant difference, but the ratio between DHA/EPA fatty acids changed significantly. Spoilage indexes in Sphyraena jello fillet had a significant difference in process methods. The amount of the indexes decreased with the addition of salt. The addition of salt and the abdominal emptying of S. jello resulted in a change in the fat content of the fish fillet, but did not a significant effect on protein, moisture, and ash content of fish fillet. The number of sycrophile bacteria in treatment A was 158 × 103 Cfu/g, which was higher than the other treatments. The lowest level was observed in salted 12% sample. It can be concluded that abdominal emptying and immersion of the Kotr fish in saltwater can lead to preserve the nutritional value and decrease the spoilage indices and increase the shelf life of the product.

Research on the quality changes of grass carp during brine salting

The research on the quality changes of grass carp during brine salting with 6%, 8%, and 10% salt additions was evaluated by chemical and physical indicators, as well as a sensory assessment and microbiological analysis. The NaCl content was proportional to salt addition and salting time. The increase of salt addition could lead to the increase of hardness and chewiness in which change trends were contrary to the pH within 24 hr. All K values were less than 10% during brine salting. The effect of 8% salt additions on free amino acids was relatively smaller. Higher levels of salt additions could inhibit bacterial growth. Combined with sensory assessment, equivalent umami concentration (EUC), and taste activity value (TAV) to analysis comprehensively, it was suggested that grass carp meat should be eaten at 4-8 hr of brine salting with 8% salt additions or processed for the next step, in which the grass carp meat had a better taste and quality.

Use of pomegranate peel and artichoke leaf extracts to improve the quality of marinated sardine (Sardinella aurita) fillets

Effects of pomegranate peel and artichoke leaf aqueous extracts on biochemical, microbiological and sensorial quality of sardine fillets was investigated during marination and storage for 90 days. Sardine fillets were marinated with 4% acetic acid, 10% NaCl and either 5% pomegranate peel extracts or 5% artichoke leaf extracts. The control sample was marinated with only 4% acetic acid and 10% NaCl. The antimicrobial activity of pomegranate peel and artichoke leaf extracts led to reduce total viable counts and total coliform during marination and storage. Samples marinated with pomegranate peel and artichoke leaves showed better oxidative stability and higher content of polyunsaturated fatty acids. Higher values of free fatty acids and histamine were found in control samples, whereas adding extracts of pomegranate peel or artichoke leaves significantly decreased total volatile basic nitrogen and trimethylamine during storage. Greater color and appearance scores were found for samples marinated with pomegranate peel and artichoke leaf extracts than the control samples.

Influence of ultrasound application and NaCl concentrations on brining kinetics and textural properties of Chinese cabbage

The effects of ultrasound application on the brining kinetics of Chinese cabbage leaves was evaluated at different NaCl concentrations (10, 15, and 20%) of the brine, and its influence on textural properties and salt distribution was also investigated. To identify the effects of these two factors on water and NaCl fluxes, the kinetics of transport was analyzed by taking the diffusion theory into account. The results showed that NaCl concentration and ultrasound application significantly affected moisture and NaCl transport. Based on Fick's equation, the NaCl effective diffusivities were enhanced upon ultrasound application during the brining process, increasing from 147.09 to 812.22%. With regard to the textural properties, a higher content of NaCl resulted in lower textural profile values. Moreover, ultrasound application significantly increased the cabbage hardness. Scanning electron microscopy and energy dispersive X-ray mapping images showed the intensification of NaCl transport brought about by ultrasound application and by the increase in NaCl content, which confirms the results of the modeling analysis. Therefore, ultrasound could be a potential technology for accelerating the brining process of cabbage. These results have direct implications for the quality management of kimchi products.

Convective Drying of Osmo-Treated Abalone (Haliotis rufescens) Slices: Diffusion, Modeling, and Quality Features

The focus of this research was based on the application of an osmotic pretreatment (15% NaCl) for drying abalone slices, and it evaluates the influence of hot-air drying temperature (40–80°C) on the product quality. In addition, the mass transfer kinetics of salt and water was also studied. The optimal time of the osmotic treatment was established until reaching a pseudo equilibrium state of the water and salt content (290 min). The water effective diffusivity values during drying ranged from 3.76 to 4.75 × 10−9 m2/s for three selected temperatures (40, 60, and 80°C). In addition, experimental data were fitted by Weibull distribution model. The modified Weibull model provided good fitting of experimental data according to applied statistical tests. Regarding the evaluated quality parameters, the color of the surface showed a change more significant at high temperature (80°C), whereas the nonenzymatic browning and texture showed a decrease during drying process mainly due to changes in protein matrix and rehydration rates, respectively. In particular, working at 60°C resulted in dried samples with the highest quality parameters.

Influence of the process parameters on osmotic dehydration of mapara (Hypophthalmus edentatus) fillet

The effects of temperature, time, pressure and brine concentration were assessed during osmotic dehydration (OD) of H. edentatus fillet. The response surface methodology (RSM) showed that using vacuum during the OD process did not cause a statistically significant change (p > 0.05) on the water loss (WL), solid gain (SG) and water activity (aw). The other factors showed a statistically significant effect (p ≤ 0.05) on at least one of these responses. Through RSM, the following condition could be defined for the OD process: brine concentration at 25 % NaCl, 25 °C, 120 min and atmospheric pressure. The Azuara model was shown to be effective in predicting the WL and SG kinetics during the OD process. The simplified solution of Fick's second law of diffusion for a slab geometry was used to calculate the average values of apparent diffusion coefficient (Deff), namely 4.73 × 10(-10) m(2)/s for WL and 1.33 × 10(-9) m(2)/s for SG.