Effects of Acid and Alkali Treatment on the Properties of Proteins Recovered from Whole Gutted Grass Carp (Ctenopharyngodon idellus) Using Isoelectric Solubilization/Precipitation

Abstract

The objective of this study was to investigate the properties of proteins from whole gutted grass carp using isoelectric solubilization/precipitation. The solubility of grass carp muscle protein was the lowest at pH 5 and the highest either at pH 3 or 12. The acid and alkali treatments could significantly increase the protein yield and decrease the fat content, while the alkali treatment led to higher protein yield than the acid treatment. The gels from protein isolates from alkali treatment or surimi from conventional water washing had higher breaking force and deformation than those of acidic treatment. The storage modulus (G′) indicated that the grass carp muscle proteins underwent denaturation during acid and alkali treatments. Protein isolates from both alkali and acid treatments showed the similar rheological patterns. This study showed that the acid or alkali treatments may be used to produce surimi from grass carp using isoelectric solubilizaion/precipitation. Practical Applications Isoelectric solubilization/precipitation may be used to recover more proteins from freshwater fish to increase yield for making surimi‐based seafood byproducts.

Preparation of protein powder from the liver of Yellowfin tuna (Thunnus albacores): a comparison of acid- and alkali-aided pH-shifting

“…This indicated that more pH-shifting. Figure 1 shows the solubility of tuna liver protein at different pH values, which was in accordance with a similar study in fish (Chen et al, 2016).…”

“…When the pH increased or decreased, the solubility increased, and the highest solubility was found at a pH of 2.0 or 12.0. This was due to the protein turning to positive or negative when the pH was away from the isoelectric point, and further led to the enhancement of electrostatic repulsion and hydration (Chen et al, 2016). According to the above results, the optimal pH in the protein solubilization process of Acid-pH or Alkali-pH was 2.0 or 12.0, respectively, and the optimal pH in the isoelectric precipitation process was 5.5.…”

A Comparative Functional Analysis of Pea Protein and Grass Carp Protein Mixture via Blending and Co-Precipitation

“…As can be seen in Figure 3, the solubility of Co, BL, PPI, and CPI was significantly pH dependent, with solubility exhibiting a U-shaped curve. The minimum solubility was observed at pH 5.0 because the isoelectric point (PI) of globulin is 4.5 and the isoelectric point of myofibrillar protein is 5.3, which is consistent with other studies of PPI [38], CPI [39], and soy-fish mixed protein [14]. When the pH deviates from the isoelectric point, solubility significantly increases because an increase in net charges on the protein surface reinforces the intermolecular electrostatic repulsive force, which promotes ion-dipole interaction between proteins and water molecules [40].…”

Squalene from Fish Livers Extracted by Ultrasound‐Assisted Direct In Situ Saponification: Purification and Molecular Characteristics

“…Consequently, the optimal amount of KOH required during U‐DS was lower than that of the conventional process but was higher than the molar concentration required for saponification (1:57 w/w), which was computed based on the average molecular weight of total fatty acids (863.47 g mol −1 ) as determined by gas chromatography (Muhammed et al, ). The excess catalyst participated in the denaturation and solubilization of proteins (Chen et al, ) and also in saponification of free fatty acids (Nagappan et al, ). In addition, the cavitation effect is known to enhance protein denaturation as well as saponification of fatty acids (Chemat et al, ; Ivanovs and Blumberga, ).…”