Food functionalities and bioactivities of protein isolates recovered from skipjack tuna roe by isoelectric solubilization and precipitation

Abstract

Four roe protein isolates (RPIs) from skipjack tuna were prepared using isoelectric solubilization (pH 11 and 12) and precipitation (pH 4.5 and 5.5) (ISP) at different pH points to evaluate their physicochemical and functional properties and in vitro bioactivities. Moisture (<6.3%) and protein (71%–77%) content were maintained. Sulfur, sodium, phosphorus, and potassium were the major elements, and glutamic acid and leucine were the prevalent amino acids (12.2–12.8 and 9.6–9.8 g/100 g protein, respectively) in RPIs. RPI‐1 showed the highest buffering capacity at pH 7–12. RPIs and casein showed similar water‐holding capacities. At pH 12, RPI‐1(pH 11/4.5) showed the highest solubility, followed by RPI‐3(pH 12/4.5), RPI‐2(pH 11/5.5), and RPI‐4(pH 12/5.5) (p < .05). Oil‐in‐water emulsifying activity indices of RPI‐1 and RPI‐3 significantly differed. At pH 2 and 7–12, pH‐shift treatment improved the food functionality of RPIs, which was superior to positive controls (casein and hemoglobin). RPI‐1 showed ABTS+ radical scavenging (102.7 μg/ml) and angiotensin‐converting enzyme inhibitory activities (44.0%).

Pea protein isolate characteristics modulate functional properties of pea protein–cranberry polyphenol particles

“…Pea protein isolates within the same manufacturing lines have very similar SDS-PAGE profiles; however, there are some differences between the Nutralys and VegOtein lines, likely a result of the difference in protein preparation techniques between the manufacturers (Figure 5a). This same observation has been made in related studies; protein extraction method seems to impact the SDS-PAGE profiles the most, and further protein processing impacts the secondary structure of proteins but the amino acid sequence (primary protein structure) remains the same (Cha et al, 2020;Ma et al, 2018;Wang et al, 2018).…”

“…Many different extraction techniques can be used to produce protein‐rich products, and previous experiments have shown that the choice of extraction technique (for example, alkaline extraction–isoelectric precipitation, salt extraction‐dialysis or micellar precipitation) produces protein products of significantly different composition and physiochemical properties (Stone et al., 2015). Even slight differences in protein isolate processing, such as adjusting the amplitude or temperature in ultrasound treatments or different pH during isoelectric purification, can result in solubility differences among related protein products (Cha et al., 2020; Ma et al., 2018). Our data also suggest that the different methods of extraction employed by the manufacturers have the largest impact on solubility—resulting in the observed differences between VegOTein and Nutralys samples—and that further processing and modifications to generate the different grades (for example, the N, MA, P80 and P85 grades within the VegOTein line) have less significant impacts.…”

“…However, extrapolating these interactions to processed protein isolates would be inaccurate as the protein isolate manufacturing process subjects proteins to many different operations including thermal, enzymatic, and chemical treatments. The resulting protein preparations have structures significantly altered from their native state and do not even resemble their denatured state, but rather have new physicochemical properties of commercial interest such as improved solubility, heat stability, gelling, or emulsifying ability (Barac et al., 2015; Cha et al., 2020; Ma et al., 2018; Wang et al., 2018).…”

Profiles of sturgeon protein prepared by two methods and the correlation between protein fractions and functional properties

“…The FC and FS were determined following the procedure of Cha et al . (2020) with minor modification. A volume of 50 mL of 1% protein solution (w/v) was homogenised for 3 min at 10000 rpm and immediately transferred to a 100 mL cylinder.…”

The Emulsion Properties of Chicken Liver Protein Recovered through Isoelectric Solubilization/Precipitation Processes

“…Over the past few years, ISP has been extensively considered as an efficient technology to modify the functional properties of protein [ 9 ]. It is recognized as an eco-friendly and low-cost technique for industrial application in order to extract protein and improve the emulsifying properties in fish [ 10 ], muscle-based products [ 11 ], and goose liver [ 12 ]. During the ISP process, proteins undergo partial unfolding and then refolding because of the extreme acid or base conditions, leading to changes in the protein conformation and structure, and thus affecting the processing properties of the protein, especially the emulsifying properties.…”