Enhancement of fish sauce quality by application of nanofiltration

Abstract

This paper focused on application of nanofiltration (NF) for improving fish sauce quality by enhancement of content of nitrogen compounds. Three kinds of NF membranes, including NF99, Desal DK and NTR7250, were investigated into separation capacity of total nitrogen (TN), amino nitrogen (AN) and NaCl from fish sauce. The influence of pretreatment of fish sauce by ultrafiltration (UF) on fish sauce quality was also investigated. Desal DK membrane exhibited the good performance for NF of fish sauce. UF pretreatment improved the rejections, except NaCl, and permeate flux. The NF of UF pretreated fish sauce with Desal DK membrane was also carried out at 40 bar of operating pressure. At 3.21 of concentration factor (CF), comparing to raw fish sauce, content of TN and AN increased by 2.21 and 2.11 times, respectively; whereas, content of NaCl increased approximately 5%. Results indicate that NF is a potential method for improvement of fish sauce quality. Hermia's model was applied to interpret the fouling phenomenon occurring in NF of UF pretreated fish sauce. The results showed that the best fit to experimental data corresponds to cake layer formation model. The excellent fitting between the experimental and calculating data for enhancement of fish sauce by NF was observed.