A review of studies on the production of protein concentrate from the wastes of fish processing industries by the pH shift method

When fish is mechanically processed on a commercial scale, usually between 45 and 55% of its weight is discarded as waste. This amount of waste from aquatic processing contains a large number of nutrients, including protein with high nutritional quality, which, despite its need, is not properly used. In order to optimally use this category of materials and also optimally use underutilization fish, several technologies including the pH shift method were taken into consideration. This method, which is based on the dissolution of the raw material in acid and base (alkali), consists of two stages. In the first stage, the pH of the raw material is reduced or increased by using the corresponding acid or base. This causes the muscle proteins to be charged together and then dissolve in the aqueous medium, and the second stage includes the precipitation of the proteins up to their isoelectric point. The protein obtained from this technique has higher nutritional and functional properties than other conventional techniques for producing protein concentrates such as surimi. This article intends to describe the principles of the pH shift process and the recovery of concentrated protein in this way, the advantages and disadvantages of both acid and alkaline methods and its comparison with the conventional (surimi) processing method, which ultimately the nutritional and functional properties of this process. It is discussed in detail.