Functional and Nutritional Quality of Protein and Lipid Recovered from Fish Processing by-Products and Underutilized Aquatic Species Using Isoelectric Solubilization / Precipitation

Abstract

The isoelectric behavior of food proteins has been well characterized in the food science literature. The isoelectric point (pI) of a protein is a pH at which the protein maintains a zero net electrostatic charge. In this state, protein-protein hydrophobic interactions overcome protein-water electrostatic interactions and the minimum solubility of proteins results. Consequently, several food science laboratories have begun active research on the application of the pI to recover functional muscle proteins, particularly fish myofibrillar proteins. Fish stocks are declining and several fisheries are currently over-exploited and may collapse by mid century. Fish processing by-products are considerable and include heads, frames, viscera, and etc. By-products are land-filled, ground-and-discarded or otherwise diverted from human consumption. By-products retain ample muscle proteins and oil. The oil contains omega-3 fatty acids. Due to the lack of commercially available technology to recover proteins and lipids from fish processing by-products or underutilized aquatic species, this tremendous resource is currently unavailable for human consumption. Fish proteins and oil from otherwise low-value by-products can be recovered using isoelectric solubilization/precipitation with recovery yields of approximately 90%. Recovered proteins and oil retain functionality and nutritional value for human food products. This article reviews the fundamental biochemical principles of food proteins and lipids as well as their structure and interaction with water in relation to the isoelectric behavior. Additionally, the most recent developments regarding application of isoelectric solubilization/precipitation to recover functional and nutritious proteins and oil from fish processing byproducts and underutilized aquatic species are addressed.

A review: Protein isolates recovered by isoelectric solubilization/precipitation processing from muscle food by-products as a component of nutraceutical foods

“…Therefore, technologies facilitating more efficient use of natural resources to fulfill human nutritional needs are required. The terms "offal," "waste," and "by-products" (sometimes referred to as "co-products") are used frequently and interchangeably to describe the secondary products generated as a result of muscle food (seafood, meat, and poultry) processing and may include both edible and inedible materials left over following processing of the primary product (Gehring, Davenport, & Jaczynski, 2009). Unfortunately, "offal" and "waste" often conjure up negative connotations because these terms imply that those materials have no value and need to be disposed of.…”

“…Unfortunately, "offal" and "waste" often conjure up negative connotations because these terms imply that those materials have no value and need to be disposed of. On the other hand, the terms "by-product" or "co-product" imply that there could be some value in the secondary products and, if they are recovered properly, they could be valuable (Gehring et al, 2009). Therefore, the food industry and scientific literature should refer to these materials as "by-products" or "co-products" instead of "offal" or "waste" so that the negative consumer bias towards value-added products made using these materials would be minimized.…”

Gelation Properties of Spent Duck Meat Surimi‐Like Material Produced Using Acid–Alkaline Solubilization Methods

“…ACS or ALS/isoelectric precipitation efficiently recovers nutritious proteins from sources that are difficult to process using conventional technology. The high efficiency and recovery rate possible with this process may yield proteins with increased functionality and oxidative stability compared with those recovered using conventional technology (Kelleher and Hultin 2000; Gehring and others 2009). Thus, isoelectric solubilization/precipitation may provide an efficient way to better process underutilized protein resources.…”

Nutritional properties of spent duck surimi-like material prepared by conventional and acid–alkaline solubilization methods

“…The alkaline and acid solubilization processes separated protein properly from other unwanted fractions, such as lipid and other impurities (e.g. bones, scale, skin, insoluble proteins) (Gehring et al 2009), thereby concentrating the proteins in the ACDS and ALDS samples. In contrast, the acid -alkaline solubilization method recovered both the sarcoplasmic protein that was not removed completely in the washing step and the additional fraction of myofibrillar protein (Kristinsson and Liang 2006), which led to the higher protein content of the ACDS and ALDS samples.…”

“…Meanwhile, conventionally processed surimi-like material had the highest gel strength among all samples. Gehring et al (2009) reported that proteins recovered through isoelectric solubilization/precipitation can be used directly or as the main ingredient in human food products. The proteins recovered by such processes are called surimi or surimi-like material.…”