Effect of high‐intensity ultrasound soymilk pretreatment on the physicochemical properties of microbial transglutaminase‐catalyzed tofu gel

Abstract

Tofu prepared by conventional methods often has a bitter taste and poor water‐holding capacity (WHC). To improve the quality of the product, alternative processes must be developed. Herein, the effect of ultrasound pretreatment on the properties of soymilk and tofu gel derived thereof were investigated. Treatment of soymilk with ultrasound gave rise to a reduction in the particle size and an enhancement in the surface hydrophobicity, whereby optimum values were obtained after 15 min treatment. Subsequently, microbial transglutaminase (MTG) was added to ultrasound‐treated soymilk to promote the soy protein crosslinking. The gel strength, WHC, and nonfreezable water content of MTG‐catalyzed tofu gel obtained from treated soymilk increased with the extension of the ultrasound pretreatment time, whereas the free sulfhydryl content decreased because of the formation of disulfide bonds. Fourier transform infrared spectroscopy demonstrated variations in the secondary structure of MTG‐catalyzed tofu gel. Furthermore, soymilk's exposure to high‐intensity ultrasound pretreatment led to a tofu gel with a dense, homogenous, and stable network structure, as evidenced by scanning electron microscopy. Therefore, this study answers for the theoretical support of the industrial production of MTG‐catalyzed tofu gel from ultrasound‐treated soymilk. Practical Application High‐intensity ultrasound pretreatment improved the texture properties of MTG‐catalyzed tofu gel. The resulting MTG‐catalyzed tofu gel has potential application in industrial production.

Analysis of the gel properties, microstructural characteristics, and intermolecular forces of soybean protein isolate gel induced by transglutaminase

“…The The results of Wu et al (2015) have confirmed this, reporting that the gel structure of soybean protein was closely related to the protein solubility. Niu et al (2017) and Gao et al (2021) also confirmed the lower SH content was related to H 0 and denser microstructure. Moreover, Luo et al (2019) and Wu et al (2017) found that TGase could limit the hydrophobicity of the SPI gel network, resulting in higher thermal stability and deformation resistance, which is also consistent with the results of this study.…”

“…In this study, the ratios of FSH to TSH for SPI, 7S, and 11S treated by TGase were significantly reduced, indicating that the degree of unfolding in the tertiary structure of soybean protein was weak. This may be because TGase inhibited the expansion of protein molecules when inducing gel formation (Gao et al., 2021 ).…”

“…This exposes diverse functional groups between protein molecules and promotes the chemical bonding of adjacent protein molecules, resulting in the formation of a tertiary network structure gel (Nivala et al, 2021;Xu et al, 2021). TGasemodified soybean protein can improve its gel properties, hydrophobicity, solubility, and texture, resulting in a high yield, high quality, and appealing taste (Gao et al, 2021;Qin et al, 2016;Xu et al, 2021).…”

“…This exposes diverse functional groups between protein molecules and promotes the chemical bonding of adjacent protein molecules, resulting in the formation of a tertiary network structure gel (Nivala et al., 2021 ; Xu et al., 2021 ). TGase‐modified soybean protein can improve its gel properties, hydrophobicity, solubility, and texture, resulting in a high yield, high quality, and appealing taste (Gao et al., 2021 ; Qin et al., 2016 ; Xu et al., 2021 ). In addition, researchers have reported the effects of TGase from different sources (e.g., Streptomyces mobaraensis and Bacillus subtilis ) on the properties of SPI gel at different PH and temperatures (Liu et al., 2020 ).…”

Application of multi-frequency power ultrasound in selected food processing using large-scale reactors: A review

“… [127] High-intensity ultrasound Effect of ultrasound on microbial transglutaminase-catalyzed tofu gel The application of ultrasound improved the water holding capacity and a dense, homogenous, and stable network structure. [128] Pulsed electric field and high-power ultrasound Effect of ultrasound and Pulsed electric field combined method on E. coli, A. niger and B. pumilus, Studied method inactivated vegetative bacteria or fungal spores in emulsions with limited inactivation for bacterial spores. [129] High-intensity ultrasound (0, 200, 400 and 600 W) Effect of different ultrasonic power levels on microbial inactivation on prebiotic whey beverage.…”