Concentration and Desalination of Protein Derived from Tuna Cooking Juice by Nanofiltration

Abstract

Tuna cooking juice is a co-product of tuna canning industry. It riches in protein, currently used for production of feed meal as well as protein hydrolysate. The finish products are usually in the form of concentrate, produced by evaporation process. However, evaporation is energy consumable process and the salt content level of the concentrate is often over the standard, thus required additional process for lowering salt content e.g. crystallization. The use of membrane technology, therefore, is of interest, since it required less energy and footprint compared with evaporation and is also able to reduce salt content of the concentrate. The aim of this study were to employ and select the membrane filtration process, and optimize the operating condition for protein concentration and desalination of tuna cooking juice. The results indicated that nanofiltration (NF) was more suitable than the ultrafiltration (UF) process, regarding the ability in protein recovery and desalination. The NF performance was evaluated in terms of permeation flux and protein and salt retentions. The protein and salt rejections of NF were 96 % and 5 %, respectively. The permeate flux(J) increased as transmembrane pressure (TMP) or cross flow rate (CFR) increased and the highest flux was obtained at TMP of 10 bar and CFR of 800 L/h. Operating with batch mode, the permeate flux was found to decrease as protein concentration increased, and at volume concentration factor about 4, the protein concentration  about 10% while salt removal was aproximately 70 % of the initial value. This work clearly showed that NF was successfully employed for concentration and desalination of protein derived from tuna cooking juice.