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- Examination of Power Ultrasound and Organic Acid-based Hurdle Technology in the Reduction of Salmonella Enterica on Peaches and Apples
- Mathias, Hina Valida
Fresh produce includes fruit matrices like whole peaches and apples that are minimally processed and are a popular choice among different...
Show moreFresh produce includes fruit matrices like whole peaches and apples that are minimally processed and are a popular choice among different types of demographics because of their nutrition content and health benefits. However, there have been increasing pathogen outbreaks in these matrices over the past few decades, which are majorly rooted in cross contamination either due to poor handling pre and post processing or the insufficient reduction of the pathogen at processing by the applied hurdle technology. While chemical sanitizers are a popular option in the food industry, the awareness and demand for green consumerism and sustainability have created a need for research to determine the efficacies of organic acids and non-thermal technologies like power ultrasound in the reduction of different pathogens on different food matrices. This study focusses on the S. enterica reduction capabilities of three organic acids – citric, malic, and lactic alone and in combination with 40 kHz power ultrasound at 1, 2 and 5% for treatment times of 2, 5 and 10 min on whole yellow peaches and gala apples. Peaches and apples were spot inoculated with a four-strain cocktail of S. enterica, resulting in 9 log CFU/fruit. Post air drying for 1 h, the fruits were treated with water, 1, 2, or 5% citric, lactic, or malic acid for 2, 5 or 10 min with and without power ultrasound treatment at 40 kHz. The population of S. enterica on the fruits was enumerated before and after treatment. Three independent trials with triplicate samples were performed for each condition. Population differences were evaluated via Student's t-test and ANOVA; p<0.05 was considered significant. The initial level of inoculum ranged from 8.67 ± 0.41 to 8.20 ± 0.26 log CFU/peach and 7.28 ± 0.60 to 8.17 ± 0.37 log CFU/apple in peaches and apples, respectively. Water treatments showed pathogen reduction as high as 1.22 log CFU/peach and 1.02 log CFU/apple. Citric acid treatments on peaches showed significant pathogen reduction at higher time increments at 5% with a reduction of S. enterica as high as 2.24 log CFU/peach after 10 min. Malic acid showed the highest recorded log reduction in peaches at 5% and 10 min being 4.20 log CFU/peach (n=1/9, samples above the enumeration limit) and apples at 5% and 5 min being 3.71 log CFU/apple (n=4/9, samples above the enumeration limit) both in combination with an ultrasound. Lactic acid, unlike the other two organic acids, showed a pathogen reduction of over 3 log CFU/fruit at 2% after 10 min, with the highest pathogen reductions of 3.76 log CFU/peach and >3.62 log CFU/apple at 5% and10 min. There was no particular trend with significant enhancement of pathogen reduction either with time increment or the addition of ultrasound and varied with the varying acids, treatment conditions and fruit matrices.