Utilization of plants and agri-food by-products as protein sources is considered a feasible approach to enhance the sustainability of food systems. Wheat germ is a by-product from the wheat milling industry that constitutes about 2.5–3.8% of the total seed weight. After oil extraction, defatted wheat germ (DWG) has >30% protein, but it is mainly utilized as animal feed rather than human food due to limited DWG-based food innovation (Zhu, Wang, & Guo, 2015). To explore its potential applications for human consumption, research efforts have resulted in the identification of various in vitro biological activities of defatted wheat germ protein hydrolysates (DWGPH), such as anti-adhesive activity against H. pylori, antioxidant, anticancer, and zinc-chelating activities (Karami, Peighambardoust, Hesari, Akbari-Adergani, & Andreu, 2019; Sun et al., 2020; Zhu et al., 2015). Bioactive compounds with anti-adhesive activity against pathogens have tremendous potential in preventing bacterial infection and as antibiotic alternatives (Sun & Wu, 2017). H. pylori is one of the most common pathogens (colonizing an estimated half of the world population) and categorized as a class I carcinogen by the World Health Organization (WHO) (Neshani et al., 2019). Our group recently demonstrated the anti-adhesive activity against H. pylori of Pronase-DWGPH, which indicated its potential as a value-added food ingredient for preventing H. pylori infection (Sun, Zhang, et al., 2020). The anti-adhesive mechanism is attributable to peptides functioning as receptor analogs in binding to H. pylori. Peptides with potential H. pylori-binding ability (n = 267) were identified from Triticum aestivum using shotgun peptidomic analysis (Sun, Zhang, et al., 2020).

In addition to biological activities, it has been demonstrated that peptides exerted techno-functional properties on food product formulations, such as emulsifying and emulsion-stabilizing properties (Lv et al., 2019; Mellinger-Silva et al., 2015; Tong et al., 2021). The emulsifying and emulsion-stabilizing properties of peptides depend upon their amphiphilic characteristics, which facilitate the adsorption of peptides to the oil-water interface and formation of a physical barrier to protect emulsion droplets from flocculation and coalescence by providing steric hindrance and/or electrostatic repulsions (Tong et al., 2021; Yesiltas et al., 2021). Besides, the secondary structures of peptides, such as α-helix and β-sheet, are crucial factors defining their emulsifying properties (Ricardo, Pradilla, Cruz, & Alvarez, 2021). Peptides as natural emulsifiers have attracted much attention which is driven by increasing consumer demand for clean label and sustainable food additives in food emulsions (Lv et al., 2019). Emulsifying peptides have been identified from various protein sources, such as potato, whey, and soy (Padial-Domínguez, Espejo-Carpio, Pérez-Gálvez, Guadix, & Guadix, 2020; Yesiltas et al., 2021).

Biological activities and techno-functional properties of bioactive peptides or protein hydrolysates can co-contribute to broadening their applications as functional food ingredients (Li-Chan, 2015; Nwachukwu & Aluko, 2021). Thus, the discovery of peptides with dual functionality (combination of both biological and techno-functional properties) is of great interest to food industries for novel functional food development in order to ensure their quality (appearance, taste, texture, and shelf life) and efficacy (health benefits). Recently, peptides with both emulsifying and antioxidant activities were discovered from potato proteins (García-Moreno et al., 2020; Salim & Gan, 2020). To the best of our knowledge, there is a dearth of information on the dual functionality of peptides with emulsifying property and anti-adhesive activity against bacterial infection. These dual functional peptides have potential to be used for developing novel emulsion-based functional foods such as bread, chocolate, ice cream, mayonnaise, and frozen desert. Thus, the objectives of this study were to i) apply amphiphilic scores for in silico prediction of emulsifying peptides from an anti-adhesive peptide database created by our group (with anti-adhesive potential against H. pylori) (Sun, Zhang, et al., 2020); ii) validate the emulsifying property and anti-adhesive activity in vitro; iii) investigate the effect of environmental stresses (pH, ionic strength, and thermal treatment) on their emulsifying properties; and iv) elucidate the possible anti-adhesive mechanism using molecular docking. Oil-in-water (O/W) macroemulsions are most commonly used in the food processing industrial sectors which were chosen as the emulsion type in this study (Sundarraj & Ranganathan, 2019).