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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOPING PROCESSING INTERVENTION TECHNOLOGIES

Location: Food Safety and Intervention Technologies

Title: Inactivation of an E.coli 0157:H7 and Salmonella composite on fresh strawberries by varying antimicrobial washes and vacuum perfusion

Authors
item Gurtler, Joshua
item Bailey, Rebecca
item Jin, Zhonglin
item Fan, Xuetong

Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 2, 2014
Publication Date: N/A

Interpretive Summary: Twenty-seven antimicrobial washes were used to remove E. coli O157:H7 and Salmonella enterica from strawberries. Vacuum perfusion was used to draw sanitizers into porous tissues. Four treatments inactivated greater than 99.9 percent of bacteria, including (a) 1 percent acetic acid + 1 percent hydrogen peroxide, (b) 30 ethanol + 1 percent hydrogen peroxide, (c) 90 ppm peracetic acid, and (d) 1 percent lactic acid + 1 percent hydrogen peroxide. Two additional treatments inactivated greater than 99.5 percent of bacteria: (a) 40 percent ethanol, and (b) 1 percent each of phosphoric + fumaric acids. Eight treatments reduced 90 – 99.5 percent of bacteria. Vacuum perfusion did not enhance inactivation of bacteria. Results from this study provide decontamination options for retail operations just prior to serving strawberries to customers.

Technical Abstract: A 2011 outbreak of hemorrhagic colitis, which resulted in the death of two individuals, was associated with contaminated strawberries. A study was conducted to identify antimicrobial washes effective at inactivating E. coli O157:H7 and Salmonella enterica from the surface of fresh whole strawberries during two-minute immersion washes. Twenty-seven antimicrobial treatments were tested. Vacuum perfusion was applied to strawberries during chlorine and peracetic acid treatments to promote infiltration of sanitizer into porous strawberry tissue. Strawberries were inoculated to 7.1 log CFU/strawberry with a seven-strain bacterial composite, consisting of three strains of E. coli O157:H7 and four serovars of Salmonella enterica. Berries were air-dried for two hours and immersed in circulating antimicrobial solutions for 120 seconds at 22 degrees C. Four treatments inactivated greater than 3.0 log CFU/strawberry, including (a) 1 percent acetic acid + 1 percent H2O2, (b) 30 ethanol + 1 percent H2O2, (c) 90 ppm peracetic acid, and (d) 1 percent lactic acid + 1 percent H2O2. Two additional treatments that inactivated 2.8 log CFU/strawberry were (a) 40 percent ethanol, and (b) 1 percent each of phosphoric + fumaric acids. Eight treatments reduced 2.0-2.6 log CFU/strawberry. Five treatments inactivated less than 1.45 CFU/strawberry, including (a) 1 percent citric acid, (b) 1 percent lactic acid, (c) 1 percent acetic acid, (d) 0.5 percent each of acetic + citric acids and (e) 0.5 percent each of acetic + lactic acids. The use of vacuum perfusion with 200 ppm chlorine or 90 ppm peracetic acid did not inactivate greater populations of pathogens as did the same treatments without vacuum perfusion. Fourteen treatments inactivated no more pathogens than did sterile deionized water. Results from this study provide some options for end-point decontamination of strawberries for retail operations just prior to serving to customers.

Last Modified: 11/24/2014
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