Desalination of fish sauce by electrodialysis: effect on selected aroma compounds and amino acid compositions

Fish sauce is an ingredient that exhibits unique flavor and is widely used by people in Southeast Asia. Fish sauce, however, contains a significant amount of salt (sodium chloride). Recently, electrodialysis (ED) has been successfully applied to reduce salt in fish sauce; however, no information is available on the effect of ED on changes in compounds providing aroma and taste of ED-treated fish sauce. The selected aroma compounds, amino acids, and sensory quality of the ED-treated fish sauce with various salt concentrations were then analyzed. The amounts of trimethylamine, 2,6-dimethylpyrazine, phenols, and all carboxylic acids except for hexanoic acid significantly decreased, whereas benzaldehyde increased significantly when the salt removal level was higher. The amounts of all amino acids decreased with the increased salt removal level. Significant difference in flavor and saltiness intensity among ED-treated fish sauce with various salt concentrations, as assessed by a discriminative test, were observed. PRACTICAL APPLICATION: Information obtained in this work can serve as a guideline for optimization of a process to produce low-sodium fish sauce by ED. It also forms a basis for further in-depth sensory analysis of low-sodium fish sauce.     

Effect of electrodialysis pretreatment on physicochemical properties and morphology of spray-dried-fish sauce powder

Fish sauce is a popular Asian food ingredient having specific flavor that gives pleasure to the senses of taste. However, fish sauce contains high-salt content, which is nowadays not desirable by health-conscious consumers. Recently, it has been shown that electrodialysis succeeds in reducing the salt content of fish sauce without affecting its important characteristics over a specific range of residual salt content. In this study the effect of electrodialysis pretreatment prior to spray drying to produce low-salt fish sauce powder, which is a more shelf-stable and convenient product compared with liquid fish sauce, was investigated. Product recovery, morphology and selected physicochemical properties, i.e., moisture content, water activity, hygroscopicity, as well as X-ray diffraction (XRD) patterns of the fish sauce powder were determined. The ED-treated-fish sauces of various salt contents (in the range of approximately 2–25% w/w) were spray dried at inlet drying air temperatures of 120–180 °C. It was found that the feed salt concentration and inlet air temperature had significant effects on all observed variables. This is due to the fact that the feed salt concentration strongly affected water removal from the ED-treated-fish sauce during spray drying, leading to significant alterations of the ED-treated-fish sauce powder properties.     

Modeling and Optimization of Electrodialytic Desalination of Fish Sauce Using Artificial Neural Networks and Genetic Algorithm

Electrodialysis (ED) has been proposed as a means to reduce sodium ion concentration in fish sauce. However, no information is so far available on the optimum condition to operate the ED process. Artificial neural network (ANN)-based models were therefore developed to predict the ED performance and changes in selected quality attributes of ED-treated fish sauce; optimum operating condition of the process was then determined via multi-objective optimization using genetic algorithm (MOGA). The optimal ANN models were able to predict the ED performance with R ²?=?0.995, fish sauce basic characteristics with R ²?=?0.992, and the concentrations of total aroma compounds and total amino acids, flavor difference, and saltiness of the treated fish sauce with R ²?=?0.999. Through the use of MOGA, the optimum condition of the ED process was the use of an applied voltage of 6.3 V and the maintenance of the residual salt concentration of the treated fish sauce of 14.3 % (w/w).     

Electrodialysis Desalination of Fish Sauce: Electrodialysis Performance and Product Quality

ABSTRACT:  Fish sauce has a unique, pleasant flavor, but contains high levels of sodium chloride, which is nowadays not desirable for health-conscious consumers. Although many researchers have attempted to solve this problem by substituting sodium with potassium in fish sauce, potassium-based products are still unsuitable for patients with kidney disease. Thus, electrodialysis (ED) desalination of fish sauce was carried out. The rate of salt removal, evolution of total soluble solids, and electrical conductivity of the electrodialysis-treated fish sauce were investigated. Moreover, the system performance in terms of yield, energy consumption, and current efficiency were examined. Density, viscosity, ion concentrations (that is, Na⁺, K⁺), total nitrogen, amino nitrogen, and color were investigated at various values of input voltage (6, 7, and 8 V) and remaining salt concentration (22%, 18%, 14%, 10%, 6%, and 2%[w/w]). The results indicated that an increase in the input voltage led to an increase in the rates of salt removal, electrical conductivity, and total soluble solids. The energy consumption increased whereas current efficiency and yield decreased significantly with an increase in input voltage and the salt removal level. Physicochemical properties of the treated fish sauce, in terms of the total soluble solids, density, viscosity, ion concentrations (that is, Na⁺, K⁺), total nitrogen, and color were significantly affected by the input voltage and the salt-removal level.     

Profiles of volatile compounds and sensory characteristics of Robusta coffee beans roasted by hot air and superheated steam

Although superheated steam (SHS) roasting has proved to be capable of improving selected quality of roasted Robusta coffee beans, impact of SHS roasting on aroma characteristics of the beans is not well understood. This study therefore aimed to investigate the effect of SHS roasting on aroma profiles and sensory characteristics of Robusta beans undergone SHS roasting at 190–250 °C; results were compared with those of beans roasted by hot air (HA). Sensory characteristics of selected samples were also compared with HA-roasted Arabica beans. Forty five aroma compounds were identified; most were fully developed in beans roasted at 230 °C and tended to degrade in beans roasted at 250 °C. SHS roasting led to more extensive formation of aroma compounds contributing to caramel note, while helped reduce formation of major contributors to spicy, roasty and burnt notes. SHS-roasted Robusta beans exhibited more resemblance to Arabica beans than their HA-roasted counterpart.     

Electrodialytic Removal of Nitrate from Pineapple Juice: Effect on Selected Physicochemical Properties,Amino Acids,and Aroma Components of the Juice

This study aimed at investigating the effect of nitrate removal from pineapple juice by electrodialysis (ED) on selected properties of the ED‐treated juice. Single‐strength pineapple juice with reduced pulp content was treated by ED to reduce the nitrate concentration to 15, 10, or 5 ppm. After ED, the removed pulp was added to the ED‐treated juice and its properties, including electrical conductivity, acidity, pH, total soluble solids (TSS), color, amino acids, and selected aroma compounds, were determined and compared with those of the untreated juice. ED could reduce the nitrate content of 1 L of pineapple juice from an initial value of 50 ppm to less than 5 ppm within 30 min. A significant decrease in the electrical conductivity, acidity, pH, TSS, and yellowness, but a significant increase in the lightness, of the juice was observed upon ED. Concentrations of almost all amino acids of the ED‐treated juice significantly decreased. The concentrations of 8 major compound contributors to the pineapple aroma also significantly decreased. Adding the pulp back to the ED‐treated juice increased the amino acids concentrations; however, it led to a significant decrease in the concentrations of the aroma compounds.     

Influences of Superheated Steam Roasting and Water Activity Control as Oxidation Mitigation Methods on Physicochemical Properties,Lipid Oxidation,and Free Fatty Acids Compositions of Roasted Rice

The feasibility of using superheated steam roasting and wetting to control the water activity in an optimal range to mitigate oxidation of roasted rice was evaluated. Changes in the bed temperature as well as rice kernel moisture content, water activity, and color were monitored during fluidized bed roasting with superheated steam and hot air at 170, 190, and 210 °C. Air‐roasted rice was rewetted to raise its water activity to 0.30 to 0.35. All the samples were analyzed for the total oil content, peroxide value (PV), thiobarbituric acid (TBA) value, and free fatty acids (FFA) content and compositions. Higher roasting temperatures, especially at 210 °C, led to a significant increase (P ≤ 0.05) in the total oil content of the roasted rice. Wetting led to a significant (P ≤ 0.05) decrease in the TBA value of the air‐roasted rice, although the total FFA content significantly (P ≤ 0.05) increased. Rice roasted in superheated steam at 210 °C exhibited significantly (P ≤ 0.05) lower PV and TBA value; their total FFA content also tended to decrease, which is desirable for a longer shelf life.