Soybean cultivation has a long history and is widely practiced worldwide. Natural soy protein isolate (SPI) primarily consists of two globulin fractions, 11S and 7S, commonly referred to as glycinin and β-conglycinin [1]. Compared to other plant proteins, SPI exhibits multiple functional properties, including high solubility, water-holding capacity, emulsifying ability, and foaming performance, making it suitable for plant-based ice cream applications. However, natural SPI differs significantly from milk proteins in structure and functionality, limiting its ability to effectively stabilize fat globules and promote the controlled partial coalescence required for desirable ice cream texture, as achieved using milk proteins. Consequently, natural SPI typically serves only as a partial substitute for milk proteins in ice cream formulations. Excessive incorporation adversely affects overrun, hardness, taste, and flavor of ice cream. The limitation arises because natural plant proteins consist of multiple subunits arranged in compact structures, which restrict functional performance and limit effective application in food systems [2]. To address these functional limitations, current research commonly applies physical, chemical, and enzymatic modification techniques to systematically enhance key functional properties, including solubility and emulsifying capacity, by targeting molecular structure and plant protein conformation. This approach broadens their application potential within food systems [3]. Modified proteins effectively promote partial coalescence of fat globules. The resulting fat network progressively displaces proteins surrounding air bubbles and individual fat globules, forming a stable foam matrix. Compared to systems stabilized solely by individual fat globules and proteins, this network exhibits superior bubble performance stabilization [4]. Yan et al. [5] report that incorporating modified SPI into ice cream improves overrun, melting rate, and hardness. Hei et al. [6] demonstrate that heat-treated and TG cross-linked SPI reduces the supercooling point and enhances freeze-thaw stability in plant-based ice cream, contributing to a more delicate texture.

Ohmic heating (OH) is an emerging food processing technology that generates heat via the Joule effect. Unlike conventional heat conduction systems, OH provides direct volumetric heating, accelerating the process and promoting uniform temperature distribution. Electric field intensity (EFI) <1000 V/cm during OH is classified as a moderate electric field (MEF) treatment. The non-thermal effects of MEF serve as a potential mechanism for modifying protein interactions, altering final protein properties while minimizing excessive coagulation or complete denaturation of protein structure [7]. Compared to other non-thermal technologies, including high-pressure processing, ultrasonic and cold plasma treatments, OH is suitable for continuous production, significantly reduces energy consumption per unit, and better preserves heat-sensitive nutrients and flavor compounds. Moreover, OH offers low equipment costs, high safety, and minimal secondary pollution. Consequently, OH-treated products exhibit higher quality than those with conventional heating techniques [8]. During OH, MEF induces the polarization of SPI, disrupting hydrophobic interactions that stabilize its spatial structure and causing partial protein extension. This exposes hydrophobic groups and increases protein surface hydrophobicity. Under these conditions, SPI exhibits markedly improved solubility, foaming capacity, and emulsifying ability, enhancing its suitability for ice cream production [9]. Li et al. [10] report that OH treatment significantly alters the structural and functional properties of soymilk proteins relative to conventional heating treatment. As a result, OH treatment of soymilk effectively shortens heating time and enhances nutritional value. Similarly, Oliveira et al. [11] demonstrate that OH treatment reduces aggregation of lactoferrin molecules compared to conventional heating, resulting in improved lactoferrin emulsification.

While MEF effects on SPI have been well reported by Wang et al. [12], studies linking protein structural changes to fat globule destabilization in ice cream remain limited. Therefore, this study aims to investigate the effect of MEF treatment on SPI structural and functional properties at varying EFI (3, 6, 9, 12, and 15 V/cm) and to compare these results with those of unmodified SPI. Furthermore, modified SPI was used as a substitute for milk protein in ice cream production to evaluate the mechanisms by which protein structure and adsorption properties influence fat globule destabilization and overall product quality. These findings could help provide a solid theoretical foundation and practical guidance for developing high-quality plant-based ice cream while supporting sustainable practices in the food industry.