Temperature-dependency on the inactivation of Saccharomyces pastorianus by low-pressure carbon dioxide microbubbles

Microbubbles in Food Technology

Microbubbles are largely unused in the food industry yet have promising capabilities as environmentally friendly cleaning and supporting agents within products and production lines due to their unique physical behaviors. Their small diameters increase their dispersion throughout liquid materials, promote reactivity because of their high specific surface area, enhance dissolution of gases into the surrounding liquid phase, and promote the generation of reactive chemical species. This article reviews techniques to generate microbubbles, their modes of action to enhance cleaning and disinfection, their contributions to functional and mechanical properties of food materials, and their use in supporting the growth of living organisms in hydroponics or bioreactors. The utility and diverse applications of microbubbles, combined with their low intrinsic ingredient cost, strongly encourage their increased adoption within the food industry in coming years.

Determination of the Lethal Injury on the Inactivation of Saccharomyces pastorianus Cells by Low-pressure Carbon Dioxide Microbubbles

To clarify the lethal injury related to the inactivation of Saccharomyces pastorianus cells by low-pressure carbon dioxide microbubble (CO₂MB) treatment, surviving number, leakage of nucleic acids and proteins, fluorescence polarisation (FP) of the cell membrane, activity of alkaline phosphatase (AP), intracellular pH (pH_in), mitochondrial membrane potential (MMP), cell surface hydrophobicity (CSH) and oxidative stress of S. pastorianus treated with CO₂MB at various temperatures were measured. The number of surviving S. pastorianus cells decreased below the detection limit after CO₂MB treatment at temperatures of 40, 45 and 50 ℃, inducing a 2-log reduction at 35 ℃. The S. pastorianus cells treated with CO₂MB at temperatures above 40 ℃ showed an increase in FP and leakage of nucleic acids and proteins. The AP in S. pastorianus cells treated with CO₂MB at a temperature of 35 ℃ was also activated but inactivated at temperatures above 40 ℃. Furthermore, the decrease in pH_in and MMP and the increase in CSH of S. pastorianus were caused by CO₂MB treatment at temperatures above 35 ℃. Oxidative stress in S. pastorianus cells was also increased by CO₂MB treatment without warming but decreased at temperatures above 35 ℃. Our results lead us to infer that the type of cell injury in S. pastorianus induced by CO₂MB treatment differed from that caused by the treatment temperature and that the lethal injury was enzyme inactivation.

High-Pressure Carbon Dioxide Used for Pasteurization in Food Industry

The demand for safe, high-quality food has greatly increased, in recent times. As traditional thermal pasteurization can significantly impact the nutritional value and the color of fresh food, an increasing number of nonthermal pasteurization technologies have attracted attention. The bactericidal effect of high-pressure carbon dioxide has been known for many years, and its effect on food-related enzymes has been studied. This novel technology has many merits, owing to its use of relatively low pressures and temperatures, which make it a potentially valuable future method for nonthermal pasteurization. For example, the inactivation of polyphenol oxidase can be achieved with relatively low temperature and pressure, and this can contribute to food quality and better preserve nutrients, such as vitamin C. However, this novel technology has yet to be developed on an industrial scale due to insufficient test data. In order to support the further development of this application, on an industrial scale, we have reviewed the existing information on high-pressure carbon dioxide pasteurization technology. We include its bactericidal effects and its influence on food quality. We also pave the way for future studies, by highlighting key areas.