The Acid and Alkaline Solubilization Process for the Isolation of Muscle Proteins: State of the Art

Abstract

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.

Effects of NaCl on water characteristics of heat-induced gels made from chicken breast proteins treated by isoelectric solubilization/precipitation

“…However, they also demonstrated that the ISP process increased the surface hydrophobicity and exposed the reactive-SH groups in the myosin head (Kristinsson & Hultin, 2003a). For this reason, the refolding phenomenon in the myosin head in the ISP process as caused by pH contributes to the gel strength of recovered proteins (Nolsøe & Undeland, 2009;Raghavan & Kristinsson, 2008). Additionally, Raghavan and Kristinsson (2008) reported that the ISP-treated myosin from catfish exhibited higher hydrophobicity when NaCl was added after refolding than the control did.…”

“…In addition, the ISPC-gels with 1% NaCl and the CON did not differ in terms of hardness and chewiness. The conformation of muscle proteins is changed by ISP, which modifies properties (Kristinsson & Hultin, 2003b;Nolsøe & Undeland, 2009). The comprehensive disruption of muscle structure by ISP may also be important in aligning proteins for gel formation during heating, thus reducing NaCl demand to induce the same effect (Chang, Feng, & Hultin, 2001;Wright & Lanier, 2005).…”

“…The relative amount of secondary structure of protein prior to heating had a great significant influence on the centrifugal loss (Liu, Zhao, Xiong, Xie, & Qin, 2008). The conformation of ISP-recovered proteins is not equivalent to that of native proteins (Nolsøe & Undeland, 2009). In conventional meat processing, the effects of NaCl content (0%, 1%, and 2.5%) on the secondary structure of muscle proteins before heating were studied by Herrero, Carmona, López-López, and Jiménez-Colmenero (2008).…”

“…In addition, ISP recovers much protein while retaining its nutritional value Thawornchinsombut & Park, 2007;Yongsawatdigul & Park, 2004). Gels containing 2% NaCl that were prepared in this manner displayed better functional attributes than those produced conventionally (Nolsøe & Undeland, 2009;Tahergorabi, Sivanandan, & Jaczynski, 2012;Yongsawatdigul & Park, 2004). Kim and Park (2008) noted that NaCl negatively influences the gelation of Alaskan pollock proteins isolated by ISP.…”

Recovery of anchovy(Engraulis anchoita)and whitemouth croaker(Micropogonias furnieri)proteins by alkaline solubilisation process

“…With the growing awareness that marine resources are fi nite, numerous efforts are underway to improve the utilization of species of low commercial value (NOLSOE & UNDELAND, 2009). Obtaining fi sh protein isolates is an alternative method to diversify and improve the use of these species.…”