1Junior College at Mishima, Nihon University, 2-31-145 Bunkyou-cho, Mishima, Shizuoka 411-8555, Japan
2School of Life Science and Technology, Institute of Science Tokyo, 4259-B65 Nagatsuta cho, Midori-ku, Yokohama City Kanagawa Pref., Japan
3Phytolipid Technologies Co., Ltd., Yokohama City Kanagawa Pref., Japan
We have presented about differences of the mixed gel from whey protein isolate and sodium caseinate in the presence of glucono-δ-lactone (GDL) with or without heat-treatment at the 16 th IHC. In this time, we would like to mention about effects of mild preheat treatment of each protein on the property of mixed protein gel to clarify the roles of each protein in the mixed systems1).
Ultrasound spectroscopy and confocal laser scanning microscopy (CLSM) methods were developed to visualize of interaction between sodium caseinate (SC) and whey protein isolate (WPI) with mild pre heat-treatment (57°C, 10 min) followed by adding GDL. Ultrasonic velocity changes during incubation at 25°C after adding GDL for four kinds of mixtures (pre-heated SC plus pre-heated WPI, pre-heated SC plus no-treated WPI, no-treated SC plus pre-heated WPI and no-treated SC plus no-treated WPI) were monitored. The changes in gradient of velocity of each mixture was characteristic with each other. These results suggest that the mild pre heat-treatments of the protein effect the timing of increase of compressibility of each system. CLSM observation with individualized dyes which has different maxima of exciting and emission wavelengths showed pre-heated SC plus no-treated WPI mixture has slightly coarse structure and the highest correlation coefficient which suggests 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, pre-heated WPI leads the formation developed three-dimensional gel networks with filamentous structure from aggregated particles, whereas, SC promotes the formation of crowded networks like a cluster composed from more fine aggregated particles instead of developed filamentous structure. These results demonstrated that although SC is known as a heat-stable protein, pre-treated SC could lead to more increase of the collaboration with WPI in the presence of GDL, this finding expected a possibility to create a food material with new texture of in food using milk protein mixed system.
1) Colloids and Surfaces B: Biointerfaces 241 (2024) 114016