Impact of storage temperature on the physicochemical properties and stability of oil-in-water emulsions under subzero isochoric cooling and conventional isobaric freezing

Authors: Atci, Sumeyye; Bilbao-Sainz, Cristina; MCGRAW, VALERIE - University Of California Berkeley; Williams, Tina; Wood, Delilah; McHugh, Tara; RUBINSKY, BORIS - University Of California Berkeley

Submitted to: Innovative Food Science and Emerging Technologies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/23/2025
Publication Date: 7/23/2025
Citation: Atci, S., Bilbao-Sainz, C., McGraw, V.S., Williams, T.G., Wood, D.F., McHugh, T.H., Rubinsky, B. 2025. Impact of storage temperature on the physicochemical properties and stability of oil-in-water emulsions under subzero isochoric cooling and conventional isobaric freezing. Innovative Food Science and Emerging Technologies. 104. Article 104129. https://doi.org/10.1016/j.ifset.2025.104129.
DOI: https://doi.org/10.1016/j.ifset.2025.104129

Interpretive Summary: Keeping food safe and fresh during storage is one of the biggest challenges in the food industry, especially when it comes to mixtures like oil-in-water emulsions, which are used in products like salad dressings, creams, and sauces. In our study, we tested a new cooling method called isochoric cooling (ICC), which uses high pressure and subzero temperatures, to see if it could help these emulsions last longer and stay safe from harmful microbes. In our study, we tested a new preservation technique called isochoric cooling (ICC), which combines high pressure with subzero temperatures, to see if it could extend the shelf life and safety of these emulsions. We prepared emulsions with two oil concentrations (10% and 20%) and stored them at both cold (4'°C) and room (22'°C) temperatures. Compared to traditional freezing and refrigeration, ICC-treated emulsions stayed free of harmful microbes—such as bacteria, yeast, and mold—for significantly longer (up to 12 weeks), while also maintaining better texture, appearance, and consistency. These findings suggest that ICC could offer the food industry a more effective and energy-efficient method to preserve sensitive products. Manufacturers of sauces, dressings, and other emulsion-based foods could particularly benefit by improving product quality, extending shelf life, and enhancing food safety.

Technical Abstract: This study investigated the effects of subzero isochoric cooling (ICC) on the stability and physicochemical properties of oil-in-water (o/w) emulsions (10% and 20% oil) during storage. Emulsions underwent ICC at -18 °C/170 MPa and conventional isobaric freezing (IBF) at -18 °C/0.1 MPa for 7 days, followed by storage at 4 °C and 22 °C. Control emulsions were also stored at these temperatures for comparison. Microbial count, microstructure, globule size, zeta potential, viscosity, color, and stability were analyzed after ICC/IBF and during storage. Our results indicate that ICC-treated emulsions maintained total aerobic microorganisms, yeast, and mold below the detection limit for 12 weeks at 4 °C (both oil levels) and 12 and 4 weeks at 22 °C for 10% and 20% emulsions, respectively. In contrast, microbial counts in control and IBF emulsions reached 8.1–10.4 log CFU/mL after 4 weeks at 4 °C and 8.7–9.5 log CFU/mL after 2 weeks at 22 °C. Additionally, while IBF emulsions exhibited increased globule size, viscosity, and yellowness over time, ICC emulsions showed no significant changes, indicating greater stability. These results indicate that IBF emulsions were unstable during the freeze-thaw process, as evidenced by a significant increase in mean globule diameter, apparent viscosity, and yellowness, along with a substantial rise in microbial counts during storage. Overall, our findings suggest that ICC at -18 °C/170 MPa significantly enhances the physical stability and microbiological quality of o/w emulsions compared to IBF. Additionally, 10% oil ICC emulsions remain stable for up to 12 weeks at both 4 °C and 22 °C, while 20% oil emulsions can be stored for 12 weeks at 4 °C and 4 weeks at 22 °C.