Recent Salmonella outbreaks involving chocolate and peanut butter demonstrate the risk of contamination even in low-moisture foods, and the importance of effective sanitation systems in food production and processing facilities. Chocolate, peanut butter and other high-fat food processing environments often use alcohol-based sanitizers in place of water-based sanitization due to the immiscibility of water and fats; however, this poses a challenge due to the flammability of cleaners such as isopropanol, which requires that equipment be cooled down before cleaning and results in significant processing downtime. A team led by University of Massachusetts Amherst researchers recently showed that an oil-based sanitation system could serve as an alternative for dry sanitization, offering an effective way to kill Salmonella without the use of water or highly-flammable compounds.
The researchers tested varying concentrations of different organic acids and medium-chain fatty acids in peanut oil to assess their effectiveness against the Salmonella enterica serovar Enteritidis dried on stainless steel surfaces. The team also varied treatment time and temperature to identify the most effective oil-based sanitization procedure. Acid concentrations ranged from 50 to 500 mM and treatment temperatures ranged from 20 to 45°C. Confocal microscopy and transmission electron microscopy were among the methods used to examine each formulation’s effectiveness at damaging and killing Salmonella cells.
The team found that acetic acid in peanut oil was the most effective sanitizer, causing a 4.4 log reduction in S. Enteritidis at 500 mM and 45°C, the authors wrote. Even at 50 mM, 100 mM and 250 mM acetic acid, the combination showed increased cell membrane damage compared to untreated controls, with treatment efficacy increasing with concentration, temperature and treatment time. However, the treatment became less effective when the bacteria was dessicated at a lower relative humidity. Overall, the study showed that acidified oils present a robust and cost-effective alternative to dry sanitation methods in facilities processing high-fat, low-moisture foods, the authors concluded. This study was published in Applied and Environmental Microbiology.
“To our knowledge, using oils as a carrier of organic acids is a novel approach to delivering antimicrobial compounds against food-borne pathogens,” said lead author Lynne McLandsborough, a professor of food science at University of Massachusetts Amherst. “[Oil-based systems] would enable more frequent cleaning, boosting the safety of these products.”