Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/12/2010
Publication Date: 8/1/2010
Citation: Aabdulmalik,T.,Boyer,R.,Gurtler,J.,McKinney,J. 2010. Screening of Natural Antimicrobials for Inhibition of E.coli O157:H7 in a solidified apple juice medium [abstract].International Association of Food Protection 97th Annual Meeting. Anaheim,CA. p.1. Interpretive Summary:
Technical Abstract: Introduction: Naturally occurring antimicrobials such as plant extracts and essential oils have been used in the food industry for years. Due to increased consumer demand for minimally processed juices there has been increased interest in the use of novel antimicrobial compounds isolated from natural substances. Purpose: The purpose of this study was to evaluate ten naturally occurring compounds for their antimicrobial effect against Escherichia coli O157:H7 in a solidified apple juice medium. Methods: Spiral Gradient Endpoint software was used to determine stock concentrations for all compounds. Each of the ten antimicrobial compounds was spiral plated onto separate 15cm plates containing apple juice agar (AJA) to create a concentration gradient on the plate (AJA=plate count agar supplemented with 10% of Motts apple juice, glucose, 4.68% w/v; sucrose, 0.18%; and fructose 5.94%). An 8 log CFU/ml culture of E. coli O157:H7 CIDER (clinical isolate from apple cider outbreak) was then vertically streaked across the gradient and evaluated after incubation (37°C for 24 hours) to determine the minimum inhibitory concentration (MIC) of each compound. Results: The compounds exhibiting the most significant inhibition of E. coli O157:H7 were sorbic acid (MIC=55.91 mg/L) and cinnamic acid (MIC=59.96mg/L) (p < 0.05). Methyl paraben, ethyl paraben, butyl paraben, propyl paraben and eugenol had significantly lower antimicrobial effectiveness than sorbic acid and cinnamic acid. The least effective compound was diacetyl (781.78 mg/L), requiring an ending concentration nearly 3 times greater than any other compound. Significance: Two of the ten compounds evaluated had significant antimicrobial activity at low levels against E. coli O157:H7 and have potential to be added to a juice beverage to control pathogen growth. Future studies may address the additive or synergistic inhibitory effects of these antimicrobials.