Nutrient reduces E.coli O157:H7 cells on beef meat by up to 90%
B-phenylethylamine (PEA) is found in trace amounts in chocolate and sold by health food companies, such as Forrest Health, Beyond a Century and Sports Nutrition Insider, for mood enhancement and to aid weight loss.
North Dakota State University, Fargo, researchers found that on beef meat pieces, PEA reduced the bacterial cell count by 90% after incubation of PEA-treated and E. coli-contaminated meat pieces at 10 °C for one week.
In three experiments, they narrowed down 95 carbon and nitrogen sources to PEA, which was most the successful at reducing the bacterial cell count of E. coli O157:H7 on beef meat.
Manipulate nutrients
The research aims to use bacteria nutrients, like PEA, to manipulate dangerous bacteria into behaving in less harmful ways, according to associate professor and researcher Dr Birgit Pruess.
Dr Pruess received a $358,750 grant through National Institutes of Health and funding from the North Dakota Board of Agricultural Research and Education and the North Dakota Beef Commission.
“One possibility to use PEA at-harvest would be as a carcass-decontamination treatment. While this may not be sustainable on a large scale, one could also use PEA as a treatment of the food contact surfaces to avoid cross-contamination of meat products,” said the researchers.
Effect of nitrogen and carbon sources
In the carbon sources for the effect on respiration/growth, acetoacetic acid (AAA) and dl-α-glycerol phosphate (magnesium salt) caused up to a 50% reduction and a 60% reduction in bacterial cell count and l-lyxose caused a 75% reduction in bacterial cell count.
In the nitrogen sources, d-mannosamine caused a 30% reduction in respiration/growth and an increase in bacterial cell counts.
dl-α-amino caprylic acid (ACA) caused a reduction of more than 70% in respiration/growth but no significant reduction in bacterial cell counts.
PEA was the best performer in bacterial cell counts, causing a reduction of more than 95%.
Small pieces of beef meat were then treated with dilutions of AAA and PEA, inoculated with E. coli O157:H7 and incubated for one week.
PEA treatment caused a 90% reduction in final bacterial cell counts at a concentration of 150 mg/ml and an 85% reduction at 70 mg/ml.
AAA treatment caused about a 50% reduction in bacterial cell counts at the two highest concentrations (70 and 150 mg/ml).
Biolfilm target
The research is part of Pruess' ongoing work on preventing biofilm formation.
NDSU Department of Veterinary and Microbiological Sciences said PEA also had minor effects on reducing the amount of E. coli biofilm in bacteria grown in the beef broth.
The NDSU researchers used fluorescence labeling to identify genes that will become targets of biofilm prevention.
The genes show up as green bacteria on images that a fluorescence microscope produces, said Priyankar Samanta, an NDSU doctoral student.
The first target, FlhD/FlhC, is a regulator of flagella, lashlike appendages that protrude from the body of certain cells and enable bacteria to swim in favorable environments.
Acetoacetic acid (AAA) caused a 75% reduction in biofilm amount but dl-α-glycerol phosphate and l-lyxose did not have effects on biofilm amount from the carbon sources.
d-mannosamine caused a 70% reduction in biofilm amounts and dl-α-amino caprylic acid (ACA) caused a reduction of more than 90%.
Future research should focus on other E.coli serotypes and treatment combinations, said the study.
Source: Meat Science, Volume 96, Issue 1, January 2014, Pages 165–171
Online ahead of print: doi.org/10.1016/j.meatsci.2013.06.030
“ß-phenylethylamine as a novel nutrient treatment to reduce bacterial contamination due to Escherichia coli O157:H7 on beef meat”
Authors: Ty Lynnes, S.M. Horne, B.M. Prüß
