The acid and alkaline solubilisation process for the isolation of muscle proteins: State of the art

Journal article, 2009

The acid and alkaline solubilization processes for isolating muscle protein from ground fish raw materials are investigated by scrutinizing the literature. Following an introduction to the processes, with some underlying chemistry, patents related to the acid and alkaline solubilization process are described together with previously patented methods for processing of protein isolates. Focus is then placed on comparing a range of factors important in fish muscle protein isolation between the acid and alkaline solubilization processes, and classic washing-based surimi technology. The factors addressed were: protein yield, gel quality, color, lipid reduction, lipid oxidation, microbial stability, and frozen storage stability. A long series of studies made with different fish/shellfish species have been used for this purpose. Certain results are summarized in table form (protein yields, gel strength, and whiteness), others only in text form. From this part of the review, it is obvious that the acid process often has certain advantages (e.g., protein yield) and the alkaline process other ones (gel strength, whiteness, lipid removal, lipid oxidation, and total microbial count). Thus, the choice of method depends on the application. It is clear that most species respond differently to acid and alkaline solubilization, which is why the two methods are initially compared. In a section about new processing attempts, the use of the acid and alkaline methodology for isolating proteins from whole fish/shellfish and fish by-products is reviewed together with attempts to recover waste water proteins and attempts to modify the process. Tentative uses of the new protein isolates, e.g., as coatings, protein brines, and emulsifiers are finally described together with some conclusions and future opportunities for the acid and alkaline processes.