Submitted to: Journal of Food Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/14/2005
Publication Date: 6/15/2005
Citation: Li, S.Q., Zhang, H.Q., Jin, Z.T., Turek, E.J., Lau, M.H. 2005. Elimination of lactobacillus plantarum and achievement of shelf stable model salad dressing by pilot scale pulsed electric fields combined with mild heat. Journal of Food Science. 6:125-133. Interpretive Summary: Pulsed electric field (PEF) has been demonstrated effective to inactivate vegetative bacterial, especially in fluid juices and beverages. This study explores the feasibility of using PEF to produce a shelf stable salad dressing product. A model salad dressing formulated by Kraft Foods were processed by PEF treatment and PEF followed with mild heat treatment. While PEF treatment resulted in more than 7-logs of reduction to Lactobacillus plantarum, a very heat resistant spoilage bacterium, it only resulted in microbial shelf stability under refrigerated condition. PEF plus a mild heat, however, produced shelf stability at room temperature. This method may result in improved product quality and extended shelf life for salad dressing and similar products.
Technical Abstract: Model salad dressing inoculated with Lactobacillus plantarum 8014 was subjected to pulsed electric fields (PEF)-only processing and PEF followed by a mild heat treatment. More than 7-log inactivation was achieved by using PEF-only processing at 34 kV/cm for 45.7 microseconds with minimal heat contribution. Samples for shelf life evaluation were aseptically packed in 4-oz HIPS/EVOH/PE cups using a Benco system. The PEF treated samples were stable at 4C for the 8-week evaluation period. However, L. plantarum in the samples treated with PEF-only grew up to more than 109cfu/ml in one week at room temperature. PEF processing at 31.8kV/cm for 45 microseconds followed by a mild heat processing at 67.2 to 73.6C for 24 s resulted in a shelf stable product with an initial L. plantarum load of 3.7'103 cfu/ml. No L. plantarum 8014 recovered in the model salad dressing at room temperature for at least one year.