Monitoring sodium caseinate and whey protein isolate interaction with mild preheat treatment using ultrasound spectroscopy and confocal laser scanning microscopy

• Published in: Colloids and surfaces, B, Biointerfaces B, Biointerfaces, 2024-09, Vol.241, p.114016, Article 114016
• Main Authors: Yuno-Ohta, Naoko, Hoshi, Yuuka, Shimazaki, Mashiro, Ohta, Hiroyuki, Hori, Koichi
• Format: Article
• Language: English
• Subjects: Confocal laser scanning microscopy; Mild preheat treatment; Scanning electron microscopy; Sodium caseinate; Ultrasound spectroscopy; Whey protein isolate
• ISSN: 0927-7765; 1873-4367; 1873-4367
• DOI: 10.1016/j.colsurfb.2024.114016

Ultrasound spectroscopy and confocal laser scanning microscopy (CLSM) methods were developed to visualize the interaction between sodium caseinate (SC) and whey protein isolate (WPI) with a mild preheat treatment (57°C, 10 min) followed by adding glucono-δ-lactone (GDL). Ultrasonic velocity changes during incubation at 25°C after adding GDL for four kinds of mixtures (no-treated SC plus no-treated WPI, preheated SC plus no-treated WPI, no-treated SC plus preheated WPI and preheated SC plus preheated WPI) were monitored. The results reveal that the mild preheating treatment of the proteins affected the timing of the increase in compressibility of each system. CLSM observation with individualized dyes which have different maxima of excitation and emission wavelengths, showed the preheated SC plus no-treated WPI mixture had a slightly coarse structure and the highest correlation coefficient, suggesting the highest colocalization of the SC and WPI among the four kinds of mixed-protein systems. Furthermore, the scanning electron microscopy (SEM) observation suggests that there are some differences among the gels, namely, preheated WPI leads to the formation of developed three-dimensional gel networks with filamentous structures, whereas SC promotes the formation of cluster-like crowded networks composed of more fine aggregated particles instead of developed filamentous structures. These results demonstrated that although SC is known as a heat-stable protein, pretreated SC could lead to an increase of the collaboration with WPI in the presence of GDL. This finding anticipated the possibility creating a food material with another texture using a milk-protein mixed system. •The effects of mild preheat treatment on whey or sodium caseinate were investigated.•Ultrasound spectroscopy and confocal scanning microscopy were used.•Pretreatment of sodium caseinate (SC) led collaboration of proteins in gelation.•The preheated SC gelled with a fine clustered network with no-heated whey protein.