Soybeanhasbeenoneofthemostimportantsourcesofvegetable-sourced proteins. Soybean protein isolate was isolated, characterized, transformed into methylated soybean protein (basic and hydrophilic nature) by esterification with methanol in the presence of hydrochloric acid (50 molar ratio), and tested for their antibacterial activity against pathogenic and spoilage bacteria. Alternatively, glycinin, basic subunit, and β-conglycinin were isolated from soybean protein and testedfortheirantimicrobialaction.Supplementingrawmilkwithesterifiedsoybean protein (0.5%) reduced the titratable acidity to 0.21, maintaining its pH at 6.4 after 8 days of cold storage compared to 4 days for untreated milk. Similar action was observed when raw milk was stored at room temperature for 10 h. Adding glycinin and the basic subunit to pasteurized milk inoculated with the three bacteria L. monocytogenes, B. subtilis, and S. enteritidis (ca. 5 log CFU/mL) could inhibit their propagation after 16–20 days storage at 4
C by 2.42–2.98, 4.25–4.77, and 2.57–3.01 log and by 3.22–3.78, 5.65–6.27, and 3.35–3.72 log CFU/mL, respectively. The antifungal activities of soy protein fractions glycinin and β-conglycinin against the pathogenic fungus Penicillium digitatum, either in vitro or in situ (postharvestorange fruit), wereevaluatedand comparedwith thefungicide rhizolax