Study of the Pseudo-equilibrium During Osmotic Dehydration of Apples and Its Effect on the Estimation of Water and Sucrose Effective Diffusivity Coefficients

The study of the equilibrium is needed not only for modeling of the osmotic process as a unit operation but also for a better understanding of the mass transfer mechanisms involved in this kind of systems. A true equilibrium state usually takes very long time to achieve; therefore, a pseudo-equilibrium state is often employed. Experimental pseudo-equilibrium states for water loss and solid gain during the osmotic dehydration of apple slices (5?×?50?×?50?mm³) at different osmotic syrup concentrations (30%, 40%, 50%, and 60% (w/w) of sucrose) were evaluated. Four empirical mathematical methods (Slopes, Azuara, Zugarramurdi and Lupín, and Equal concentration) were used in order to calculate the pseudo-equilibrium values obtained and then to compare them against to the experimental ones. Additionally, the effective diffusion coefficients for water and sucrose were calculated by using those pseudo-equilibrium values. Experimental pseudo-equilibrium values increased with concentration of the osmotic syrup, ranged between 24% and 56% for water loss and 11% and 28% for solid gain; the predicted pseudo-equilibrium values followed the same trend. The decreasing order of accuracy for pseudo-equilibrium values and effective diffusion coefficients, among the methodologies evaluated, was Equal concentration method > Azuara method > Slopes method > Zugarramurdi and Lupín method. Although the Equal concentration method has no theoretical accuracy, it is independent of the kinetic data presenting a higher advantage over the other three mathematical methods evaluated.     

Equilibrium water and salt contents of sardine sheets during osmotic dehydration

Our objectives were to experimentally determine the equilibrium water and salt contents and compare the performance of prediction according to the models of Zugarramurdi and Lupín, and Azuara et al. for osmotic dehydration of sardine sheets using brine at different concentrations (0.15-0.27 g NaCl/g) and temperatures (32-38 °C). The high regression coefficients (R²>0.92) indicated the acceptability of both models for determining the equilibrium contents. The coefficients of determination and the modulus of mean relative errors for both models indicated that Zugarramurdi and Lupín model could be advantageous in estimating the equilibrium water and salt contents. Multiple comparison of means showed that equilibrium water and salt contents predicted by the model of Zugarramurdi and Lupín were lower than those by the Azuara et al. model, at all concentration and temperature conditions. The values differed by 9.4-46.9% for equilibrium water content and by 3.5-44.1% for equilibrium salt content.     

Mass transfer kinetics during osmotic dehydration of bananas (Musa sapientum,shum.)

Osmotic dehydration is used widely to partially remove water from plant tissues by immersion in a hypertonic solution. In this work, the influence of temperature (25–55 °C), sugar concentration (30–60%) and salt concentration (0–10%) of the osmotic solution was investigated during osmotic dehydration of banana (Musa sapientum, shum.). Mass transfer kinetics were modelled according to Peleg’s equation. Kinetic parameters were evaluated using response surface methodology. Peleg’s equation showed to be suitable for modelling the water removal and solute uptake. Initial rate of water loss and water concentration at equilibrium were influenced by linear factors of the three independent variables. Initial rate of sucrose uptake and sucrose uptake at equilibrium were affected by all factors and interactions. Initial rate of salt uptake and salt concentration at equilibrium showed a positive correlation with temperature and NaCl concentration and a negative correlation with sucrose concentration.     

Ripening of salted anchovy (Engraulis anchoita): development of lipid oxidation, colour and other sensorial characteristics

BACKGROUND: Changes in lipids are in general associated with quality deterioration, though earlier studies in anchovy indicate that the volatile compounds of importance to the characteristic flavour could be generated by lipid oxidation. The aim of the present paper was to study the changes in the fatty acid composition and the lipid oxidation of Engraulis anchoita during ripening and their relationship with the development of the typical sensorial characteristics. RESULTS: As a result of ripening, polyunsaturated fatty acids decrease from 4.27 to 2.42 and 2.00 g kg^?1 fatty acids in gutted fish and fillet, respectively. The most affected class of fatty acids was the n‐3 fatty acids, especially docosahexaenoic acid. Moreover, saturated fatty acids were the most stable to the process. 2‐Thiobarbituric acid reactive substances (TBARS) increased throughout ripening, and the use of fillets instead of gutted fish reduced this value. The a* value was the parameter most modified, showing a marked increase which correlates with the acquisition of a uniform pink colour. Sensory analysis did not show development of off‐odour or undesirable changes in colour during ripening. CONCLUSION: As a result of ripening, the fatty acid profile was modified and an increment of TBARS was observed. However, these changes did not lead to deterioration in the quality of the product. Copyright © 2010 Society of Chemical Industry     

Evaluation of the mechanical properties and diffusion coefficients of osmodehydrated melon cubes

The objective of this work was to evaluate the influence of osmotic agents, their concentration and temperature, on the mass transfer kinetics and mechanical properties of osmodehydrated melon cubes. Samples were immersed in a hypertonic solution of sucrose or maltose up to 8 h under controlled temperature and agitation. Water loss, sugar gain and mechanical properties were analysed throughout the process. Mass transfer kinetics was modelled according to Peleg and Fick equations. Higher water loss, lower sugar uptake and stress at rupture values more similar to fresh fruit were observed in samples treated with maltose solutions. Peleg’s model showed the best adjustment to all the experimental data, however the k₁ and k₂ parameters did not show a clear trend with the solution concentration or temperature increase. The effective diffusivity obtained using Fick’s equation varied from 3.93 × 10^?9 to 6.45 × 10^?9m² s^?1 for water loss and from 7.57 × 10^?10 to 3.14 × 10^?9m² s^?1 for sugar gain.     

Gutted and Un-Gutted Sea Bass (Dicentrarchus Labrax) Stored in Ice: Influence on Fish Quality and Shelf-Life

The sensory characteristics, chemical freshness indicator contents, and microbial counts (total aerobe, psychrotrophic bacteria, H₂S-producing bacteria, and Pseudomonas spp.) of whole un-gutted and gutted sea bass stored in ice were compared. Results of this study indicated that the acceptability quality of whole and gutted sea bass as determined by sensorial data is 11 days, respectively. No significant differences (p > 0.05) were found in the level of sensory score between whole and gutted sea bass samples. Total volatile basic nitrogen (TVB-N) values showed no significant increase for whole and gutted sea bass during storage. Trimethylamin (TMA-N) values of whole and gutted sea bass increased very slowly, reaching final values of 3.94 and, 3.38 mg/100g, respectively (day 13). Development of initial decomposition (after 7 days) occurred when bacterial counts were > 4 log CFU/g. Microbial counts showed a significant increase for whole and gutted sea bass during storage. Significant differences (p < 0.05) were found in the microbial counts between whole and gutted sea bass samples. This difference, may be attributed either to gutting procedures, which most probably were the cause of cross-contamination of fish or to the significantly higher fish flesh surface area exposed to environmental microbial contamination in the case of gutted fish.     

Efficacy of Sanitized Ice in Reducing Bacterial Load on Fish Fillet and in the Water Collected from the Melted Ice

ABSTRACT: This study investigated the efficacy of sanitized ice for the reduction of bacteria in the water collected from the ice that melted during storage of whole and filleted Tilapia fish. Also, bacterial reductions on the fish fillets were investigated. The sanitized ice was prepared by freezing solutions of PRO-SAN^® (an organic acid formulation) and neutral electrolyzed water (NEW). For the whole fish study, the survival of the natural microflora was determined from the water of the melted ice prepared with PRO-SAN^® and tap water. These water samples were collected during an 8 h storage period. For the fish fillet study, samples were inoculated with Escherichia coli K12, Listeria innocua, and Pseudomonas putida then stored on crushed sanitized ice. The efficacies of these were tested by enumerating each bacterial species on the fish fillet and in the water samples at 12 and 24 h intervals for 72 h, respectively. Results showed that each bacterial population was reduced during the test. However, a bacterial reduction of < 1 log CFU was obtained for the fillet samples. A maximum of approximately 2 log CFU and > 3 log CFU reductions were obtained in the waters sampled after the storage of whole fish and the fillets, respectively. These reductions were significantly (P < 0.05) higher in the water from sanitized ice when compared with the water from the unsanitized melted ice. These results showed that the organic acid formulation and NEW considerably reduced the bacterial numbers in the melted ice and thus reduced the potential for cross-contamination.     

Effects of perimortem stress on farmed Atlantic cod product quality: a baseline study

The potential effects of handling stress on the product quality of farmed Atlantic cod were studied in a controlled experiment (fish anesthetized with metomidate or isoeugenol, or subjected to stress by chasing for 30 min). For comparison, stress and fillet quality was also studied for commercially slaughtered farmed cod (fish sampled from waiting cage, after pumping and stunning with carbon dioxide, and after bleeding and chilling). Baseline values for stress-related parameters (blood chemistry, muscle high-energy phosphates and inosine monophospate, initial pH, muscle twitches, and rigor mortis) of rested Atlantic cod have been established. Since our stress bout showed that this species was not easily excitable, we were less convinced that we actually did study the other extreme, namely, exhausted fish. Nevertheless, the present data from the commercial slaughter of cod suggested that our stress bout was of adequate magnitude to represent potential poor handling routines. Our results consistently showed largely no differences between treatments, and that perimortem handling stress did not cause inferior flesh quality. This suggested that farmed cod can be processed with little risk of reducing product quality (quality index, fillet water content, water-holding capacity, ultimate pH, adenosine triphosphate-related degradation products and K-value, skin and fillet color, water and salt-soluble proteins, hardness, and gaping). For better maintenance of skin appearance after storage, the importance of storing the gutted cod on the belly, avoiding direct contact between skin and crushed ice, is demonstrated.     

Modelling the effect of temperature and lipid content on anchovy (Engraulis anchoita) salting kinetics

The effect of initial lipid content and temperature on the salting behaviour of anchovy (Engraulis anchoita) was studied. For this purpose brining of anchovy with variable initial lipid content (2.69–7.76 g 100 g⁻¹) was performed at temperatures between 5 and 35 °C. The obtained results indicate that initial mass transfer rate increased with brining temperature. Moreover, mass transfer rate was inversely related to the initial lipid content. In order to explain the dependence of the mass transfer rate on these variables two novel mathematical models were proposed. It was determined that both, salt gain and water loss rate constants depend on initial lipid content, whereas temperature only affects constants for salt transfer. In addition, salt gain constants depend linearly with initial lipid content and inversely with brining temperature. On the other hand, water loss rate constant was a function of the initial lipid content, fitting to a quadratic equation.     

Modelling of the feed-to-fillet transfer of ethoxyquin and one of its main metabolites,ethoxyquin dimer,to the fillet of farmed Atlantic salmon (Salmon salar L.)

ABSTRACT

Ethoxyquin (EQ) is an antioxidant supplemented to feed ingredients, mainly fish meal, which is currently under re-evaluation for use in the food production chain. EQ is partly metabolized into several metabolites of which the ethoxyquin dimer (EQDM) accumulates most in the farmed fish fillet. In this study, the feed-to-fillet transfer of dietary EQ and EQDM in Atlantic salmon fillet was investigated, and a physiologically based pharmacokinetic (PBPK-) two-compartmental model was developed, based on experimental determined EQ and EQDM uptake, metabolism, and elimination kinetics. The model was verified with an external data-set and used to simulate the long term (>1.5 years) EQ and EQDM feed-to fillet transfer in Atlantic salmon under realistic farming conditions such as the seasonal fluctuations in feed intake, growth, and fillet fat deposition. The model predictions showed that initial EQDM levels in juvenile fish are the driving factor in final levels found in food-producing animals, while for EQ the levels in feed, and seasonal variations were the driving factor for food EQ levels.     

Mass transfer evaluation of ultrasonic osmotic dehydration of cherry tomatoes in sucrose and salt solutions

In order to elaborate dehydration and osmotic equilibrium characteristics of cherry tomatoes and to analyse the applicability of Peleg model in prediction of equilibrium moisture content and the methodology of Crank’s solution to Fick’s diffusion law in calculation of effective diffusivity, cherry tomatoes were osmotically treated in ternary solution (water, sucrose and NaCl) with or without ultrasound at 30 °C. Results indicated that, a time cumulative effect of ultrasound occurred about 30 min for water loss (WL), while for sugar gain it happened after 45 min, which made the dehydration efficiency index best at the ultrasonic power of 150 W for 40 min. As a function of salt content, the equilibrium WL followed well the first order exponential decay model, and the equilibrium salt content followed well the second order polynomial. A great relative error (29.13%) between the practical determination and the predicted value indicated that Peleg model was not suitable for prediction of equilibrium moisture content. A great truncation error (865%) occurred when moisture effective diffusivity (6.66 × 10^?9 m² s^?1) was calculated with Crank’s solution to Fick’s diffusion law by letting n = 1 as compared to that (0.77 × 10^?9 m² s^?1) by letting n = 100.     

A comparison of techniques for preparing fish fillet for ICP-AES multielemental analysis and the microwave digestion of whole fish.

Four catfish fillet homogenate treatments before multielemental metal analysis by simultaneous inductively coupled plasma/atomic emission spectroscopy were compared in triplicate. These treatments were: nitric acid wet-ashing by Parr bomb digestion; nitric acid wet-ashing by microwave digestion; tetramethylammonium hydroxide/nitric acid wet digestion; and dry-ashing. The tetramethylammonium hydroxide/nitric acid method was imprecise (coefficients of variation > 20%). The dry-ashing method was fast and sensitive but had low recoveries of 50% for spiked Pb and Al and was not as precise as the Parr bomb or microwave treatments. The Parr bomb method was the most precise method but was less sensitive than the microwave method which had nearly the same precision. The microwave method was then adapted to homogenates of small whole fish < or = 3 cm in length. The whole fish homogenate required more vigorous digestion conditions, and addition of more acid after the evaporative step because of the presence of less oxidizable and acid-soluble components than fillet. The whole fish homogenate was also more heterogeneous than catfish fillet. A quality assurance protocol to demonstrate homogenate uniformity is essential. The use of a non-specialized microwave oven system allowed precise results for fillet and whole fish homogenates.     

Uptake, elimination, and relative distribution of perchlorate in various tissues of channel catfish

This study was undertaken to determine the kinetics of uptake and elimination of perchlorate in channel catfish, Ictalurus punctatus. Perchlorate--an oxidizer used in solid fuel rockets, fireworks, and illuminating munitions--has been shown to effect thyroid function, causing hormone disruption and potential perturbations of metabolic activities. For the uptake study, catfish were exposed to 100 mg/L sodium perchlorate for 12 h to 5 d in the laboratory. Perchlorate in tissues was analyzed using ion chromatography. The highest perchlorate concentrations were found in the head and fillet, indicating that these tissues are the most important tissues to analyze when determining perchlorate uptake into large fish. To calculate uptake and elimination rate constants for fillet, gills, G-I tract, liver, and head, fish were exposed to 100 ppm sodium perchlorate for 5 days, and allowed to depurate in clean water for up to 20 days. The animals rapidly eliminated the perchlorate accumulated showing the highest elimination in fillet (Ke = 1.67 day(-1)) and lowest elimination in liver (Ke = 0.79 day(-1)).     

不同贮藏温度下鲐鱼生物胺变化的研究

为探究不同温度和预处理对鲐鱼生物胺含量变化的影响,用高效液相色谱法分析了整鱼和去内脏鱼在不同贮藏温度下8种生物胺以及总生物胺含量的变化,结果发现,鲐鱼中主要的生物胺为组胺、腐胺、尸胺、酪胺。随着温度的升高,鲐鱼中总生物胺含量的增加迅速变快。在0、4、10、15、20、25和30 ℃贮藏1 d后,整鱼中总生物胺的积累量分别为40.34、93.44、107.95、73.39、119.99、4649.90、6446.43 mg/kg。在0、4、10、15、20、25和30 ℃贮藏条件下,整鱼中组胺的含量超过国家规定的高组胺鱼类安全限量(400 mg/kg)的时间分别为12、5、4 d和48、36、15、14~16 h,-18 ℃贮藏6个月,组胺积累量仅为13.45 mg/kg。另外,去内脏能减少生物胺的生成,在-18、0、4、10、15、20、25和30 ℃贮藏条件下,去内脏后总生物胺最终积累量减少程度分别为14.22%、39.79%、13.83%、29.06%、22.60%、13.56%、26.13%、21.26%。因此,低温冷冻和去内脏处理能够有效控制鲐鱼中生物胺的生成,防止腐败。本研究为有效控制鲐鱼生物胺的产生提供了参考依据。     

Comparison of Peleg and Azuara et al. models in the modeling mass transfer during pile salting of goat sheets

Application of the Peleg and Azuara et al. models for describing mass transfer during pile salting of goat sheets using different mixtures of NaCl, KCl, CaCl₂ and MgCl₂ was investigated The high coefficient of determination (R² > 0.97 and R² > 0.95 for Peleg and Azuara et al. models, respectively) and the modulus of mean relative errors (MRE < 10% for both models) indicated the acceptability of both Peleg and Azuara et al. models for predicting both moisture loss and salt uptake. The equilibrium moisture and salt contents were estimated using Peleg rate constants and Azuara et al. model parameters. Equilibrium moisture (x_w) and salt contents (x_s) varied from 0.522 to 0.860 g water/g db and from 0.311 to 0.352 g NaCl/g db respectively. Multiple comparison of means showed that x_w and x_s predicted by the Peleg model were lower than those estimated by the Azuara et al. model. The values differed by 1.86–13.6% for x_w and by 1.13–10.57% for x_s.     

Quality assessment of whole and gutted sardines (Sardina pilchardus) stored in ice

The quality and shelf life of whole ungutted and gutted sardines ( Sardina pilchardus ) stored in ice were studied. The changes in the fish were investigated by sensory assessments, chemical analyses and microbiological analyses. The sensory scores of uneviscerated and gutted sardines stored in ice at +4 °C were 7 days. The chemical indicators of spoilage, total volatile basic nitrogen and trimethylamine values of gutted sardine increased very slowly, whereas for whole ungutted samples higher values were obtained reaching a final value of 15.03–29.23 mg per 100 g and 2.36–4.16 mg per 100 g, respectively (day 9). Peroxide and thiobarbituric acid values remained lower for whole ungutted sardine samples until day 9 of storage, whereas for gutted fish were higher. The level of histamine exceeded the legal limit in whole ungutted sardine after 7 days of storage in ice, during which sardines were rejected by the sensory panel. Mesophilic aerobic bacteria count, H₂S-producing bacteria, sulphide reducing anaerobe Clostridias, Enterobacteriaceae count of whole ungutted sardine samples are higher than gutted sardine samples during the storage. Psychrotrophic bacteria counts of the two groups were not different. The limits of microbiological data were not exceeded throughout the storage in both the groups' samples.     

Effects of Freezing on Quality of Cold-smoked Salmon Based on the Measurements of Physiochemical Characteristics

ABSTRACT: How the quality of cold-smoked Atlantic salmon ( Salmo salar ) is affected by freezing the raw fish as whole fish, as gutted fish, and as fillets before smoking, and by freezing the finished product after smoking was studied. Freezing before smoking resulted in increased product yield and water content, but softer texture and increased K-value. Freezing reduced the content of astaxanthin but increased the lightness and the color intensity of the flesh. Gaping increased when the fish was frozen as fillets before smoking. Freezing only after smoking led to fewer changes in quality than freezing before smoking, whereas refreezing the finished products had little additional effect on quality.     

Toxicokinetics and carry-over model of α-hexabromocyclododecane (HBCD) from feed to consumption-sized Atlantic salmon (Salmo salar)

A two-compartmental model for the kinetics of carry-over of the brominated flame retardant α-hexabromocyclododecane (HBCD) from feed to the fillet of farmed harvest-sized Atlantic salmon (Salmo salar L.) was developed. The model is based on a fat compartment for storage of the lipophilic α-HBCD and a central compartment comprising all other tissues. Specific for this model is that the salmon has a continuous growth and that fillet contaminant levels are explained by both the fat and the central compartments. The uptake and elimination kinetics are obtained from experimental data where consumer sized (start weight approximately 1 kg) Atlantic salmon was fed α-HBCD spiked feed (280 ± 11 μg kg(-1)) for 2 months followed by a depuration period of 3 months. The model was used to simulate the HBCD feed-to-fillet transfer in Atlantic salmon under realistic farming conditions such as the seasonal fluctuations in feed intake, growth and fillet fat deposition. The model predictions gave fillet concentrations of 0.2-1.8 μg kg(-1) depending on the level of fish oil inclusion in the salmon diets when using fish oil with high POP background levels. Model simulations show that currently farmed Atlantic salmon can contribute to a maximum of 6% of the estimated provisional food reference dose for HBCD.     

SEASONAL CHANGES IN PROXIMATE COMPOSITION OF ANCHOVY AND STORAGE STABILITY OF ANCHOVY OIL

Changes in proximate composition of anchovy were investigated during the catching season from October to March. In addition, stability of anchovy oil depending on storage temperature and time were studied. During the recent study, water, fat, protein and ash content of anchovy varied between 65.9–74.0%, 9.0–15.3%, 12.8–16.4% and 1.7–2.2%, respectively. The anchovy oil stored at 4C was found to be unacceptable for consumption at the end of the 90th day of storage according to peroxide, acid, unsaponifiable matter and thiobarbituric acid values. An identical sample stored at − 18C was acceptable for 120 days of storage, but eventually became unacceptable after that.

PRACTICAL APLICATIONS

Anchovy has a great economic importance for the Turkish fishery industry. Approximately 42% of the annual catch of anchovy is used in fish meal and oil production in Turkey ( SIS 2002 ). Therefore, the proximate composition of anchovy and seasonal changes have fundamental importance for consumers, manufacturers and wholesalers, because it is important for consumers to know what they eat, for manufacturers to figure out how they manage long storage stability for their products, and for wholesalers to buy equivalent of their payment. An important issue that has attracted attention of the manufacturers is the storage life of fish oil. Therefore, the results presented in this study are expected to be useful for the fish oil industry in Turkey or even in other countries processing anchovy into fish oil.