Acid-induced gelation of bacterial single cell protein as compared to soy and milk proteins: the effect of protein concentration and temperature.

Single cell proteins offer a sustainable protein source for future populations, however their potential as main ingredients in food structuring is still unexplored. The aim of this study was to investigate how incubation temperature (20 or 40 °C) and concentration affect the acid-induced gelation of bacterial single cell protein (SCP), using glucono-δ-lactone as the acidulant. Furthermore, the influence of acidification rate on the structural development of SCP was evaluated in relation to conventional protein-rich ingredients (skimmed milk powder (Milk) and soy protein isolate (SPI)).
Despite significant variation in the compositions of the different proteins, all protein suspensions were prepared at 3.5% protein content. In both milk and SPI, the acidification rate was a key factor influencing the reorganization of protein networks during structure formation and the resulting gel characteristics. Conversely, this effect was not pronounced in SCP. The rheological measurements showed that temperature influenced the time required to reach the gelling point (tg) across all protein samples. In contrast to Milk and SPI, temperature had less impact on the pH at tg and on the structure velocity (dG*/dt/tg) of SCP. SCP gels maintained a moderate water-holding capacity and exhibited low gel strength, regardless of the temperature at which acidification occurred. Microstructure analysis revealed that SCP gels showed higher porosity compared to other samples. By increasing the SCP content (≥ 6.2% protein), the impact of temperature on gel strength and WHC was more pronounced. While SCP has potential as a structuring protein for non-dairy yoghurt, further studies are required to fully grasp its intricate structure, composition, and function.