Effects of different drying methods on the structures and functional properties of phosphorylated Antarctic krill protein

Abstract

Antarctic krill protein (AKP) was extracted from Antarctic krill by an alkali dissolution‐isoelectric precipitation method and then it was phosphorylated with sodium tripolyphosphate. The phosphorylated Antarctic krill protein (P‐AKP) powder was obtained by spray‐drying (SD), freeze‐drying (FD), and hot‐air drying (AD), and the effects of these drying methods on the structures and functional properties of proteins were investigated. The P‐AKP powder dried by SD had the best sensory performance, and its particle size was much smaller than that of FD and AD. Scanning electron microscope displayed a uniform particle size of SD powder and the particles were uniformly dispersed. X‐ray diffraction analysis showed a higher crystallinity of SD sample than AD and FD. Differential scanning calorimeter analysis revealed that SD sample had the best thermal stability and less protein denaturation (ΔH = 210.80 J/g), followed by FD (ΔH = 80.48 J/g) and AD (ΔH = 73.94 J/g; P < 0.05). Fourier transform infrared showed that SD sample contained more protein secondary structure. Compared with SD, the phosphorylated group‐related chemical bonds in FD and AD samples were partially destroyed. SD sample had the highest protein solubility, oil absorption capacity, emulsifying, and foaming activities than FD and AD (P < 0.05). Although FD had the highest water absorption capacity, sample prepared with AD had the worst functional performance. Therefore, different drying methods used for preparation of the P‐AKP can affect its physicochemical and associated functional properties, and SD could be an appropriate drying method for the industrial mass production of P‐AKP powders with better functionalities. Practical Application The optimal drying method for preparing the phosphorylated Antarctic krill protein (P‐AKP) powder was proved to be spray‐drying (SD), because the physicochemical and functional properties were better for P‐AKP dried by SD than the other drying methods. Hence, SD was recommended for the industrial mass production of P‐AKP powders with better functionalities. This research can provide theoretical guidance for the further processing and utilization of P‐AKP, and offer technical reference for food processing and preservation.

Comparative study of two types of pre-extraction treatment (drying or non-drying) on physicochemical, structural and functional properties of extracted insect proteins from Tenebrio molitor larvae

“…Sulfhydryl content is an essential conformational aspect in many proteins, which affects the functional changes of proteins. Some processing methods, such as heating and high pressure, might cause changes and destruction of sulfhydryl content, which can significantly affect the functional properties of proteins ( Lin et al, 2020 ). The total sulfhydryl, free sulfhydryl, and disulfide bond content of samples are shown in Table 3 .…”

“…This phenomenon was mainly attributed to a higher temperature of the MD process during drying treatment, which significantly promoted the formation of disulfide bonds. Lin et al (2020) indicated that the higher drying temperature could enhance the extent of protein denaturation, which subsequently resulted in increased disulfide bond contents. Moreover, the low temperature or freezing stresses could also promote the occurrence of protein denaturation to different extents, which led to obviously higher disulfide bond contents of the FD group than ND group ( P < 0.05).…”

“…Another study reported that solubility was usually affected by its hydrophobic/hydrophilic balance, which depended on the amino acid composition of the protein and the degree of denaturation ( Santos et al, 2011 ). Therefore, combined with the results of surface hydrophobicity and amino acids, it was found that the MD group's poor solubility of protein was due to fewer hydrophobic residues, increased charge, electrostatic repulsion, and ionic hydration at different pH values ( Lin et al, 2020 ).

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“…8 , the WHC of the ND and FD groups had no significant differences ( P > 0.05), and the MD group had the lowest WHC value ( P < 0.05). The higher WHC of the ND group and the FD group might be due to lower loss of soluble protein and less protein denaturation, while the lower WHC of the MD group was attributed to the external moisture-resistant skin formed during the drying process ( Lin et al, 2020 ). There was no significant difference between the OHC of the MD group and the FD group ( P > 0.05), while the ND group had the highest OHC ( P < 0.05).…”

“…Compared with the MD and FD groups, the ND group had the highest FC and FS ( P < 0.05). Proteins with ideal foaming properties generally have high surface hydrophobicity and good solubility ( Lin et al, 2020 ). Therefore, in Table 3 and Fig.…”