The Use of Lactic Acid Bacteria to Control the Growth of Foodborne Pathogens on Fresh-Cut Fruits and Sprout Vegetables

<p>Growing consumer awareness of the health benefits associated with fruits and vegetables and demand for easy to prepare products has prompted the development of a wide variety of minimally processed fruits and vegetables. Minimally processed fruits and vegetables are often peeled, cut, or diced which compromise the produces’ natural protective barriers, exposing a nutrient rich medium and providing an ideal environment for the growth of microorganisms, including foodborne pathogens. The germination conditions of sprout vegetables consisting of relatively high temperatures and humidity, low light and abundance of nutrients are also conducive to the proliferation of foodborne pathogens. Recent outbreaks and recalls indicate additional measures are needed to improve food safety and maintain the integrity of the food industry.</p> <p>The objective of this research was to evaluate the efficacy of Lactic Acid Bacteria (LAB) against <em>E. coli </em>O157:H7, <em>L. monocytogenes, </em>and <em>Salmonella </em>spp. on apple slices and alfalfa sprouts and it’s influence on product quality. Apple slices inoculated with <em>E. coli </em>O157:H7, <em>L. monocytogenes, </em>and <em>Salmonella </em>spp. (each at 10⁴CFU/g) were treated with <em>Lb. plantarum</em> alone and in combination with <em>Pediococcus acidophilus </em>and <em>P. pentosaceus </em>(LPP)<em> </em>(10⁷CFU/g) while alfalfa seeds were inoculated with <em>L. monocytogenes</em> and <em>Salmonella </em>spp. (each at 10¹ CFU/g and 10³CFU/g) and treated with LPP (10⁷ CFU/g). The growth of the microorganisms on the apple slices was assessed during five and seven days of storage at 4^◦C and 20^◦C, respectively. Growth on alfalfa seeds was reported during five days of sprouting at 20^◦C. Populations of LAB were maintained between 7.0 log CFU/g and 8.0 log CFU/g throughout storage and sprouting on the sliced apples and alfalfa seeds, respectively.</p> <p>Although LAB had no significant effect on pathogen populations on apple slices during storage at 4°C (p > 0.05), populations were significantly different at 20°C (p < 0.05). Populations of <em>L. monocytogenes</em> in the presence of <em>Lb. plantarum</em> and LPP were 1.84 log CFU/g and 2.84 log CFU/g less than the controls after five days of storage at 20°C (p < 0.05). Populations of <em>E. coli </em>O157:H7 in the presence of <em>Lb. plantarum </em>and LPP were 1.83 log CFU/g and 1.86 log CFU/g less than the control after one and three days of storage, respectively. Finally, populations of <em>Salmonella </em>spp. were 0.86 log CFU/g less than populations in the absence of LPP after three days of storage.</p> <p>LPP had a significant effect on the growth of <em>L. monocytogenes </em>and <em>Salmonella </em>spp. on alfalfa seeds (p < 0.05). After five days of sprouting, populations of <em>L. monocytogenes </em>at an initial concentration of 10¹CFU/g and 10³CFU/g on seeds treated with LPP were approximately 4.5 log CFU/g and 1.0 log CFU/g less than the untreated seeds, respectively. Populations of <em>Salmonella </em>spp. at an initial concentration of 10¹CFU/g and 10³CFU/g were 1.0 log CFU/g less than the control.</p> <p>Overall, on apple slices the combination of <em>Lb. plantarum </em>with <em>P. acidophilum </em>and <em>P. pentosaceus</em> demonstrated greater efficacy than <em>Lb. plantarum</em> alone and reduction of <em>L. monocytogenes</em> by <em>Lb. plantarum</em> and LPP was greater than <em>Salmonella </em>spp. and <em>E. coli </em>O157:H7 on apple slices and alfalfa seeds, alike. LAB had a minimal effect on the quality of the apple slices and alfalfa seeds. LAB could be an effective strategy in reducing pathogen populations at abusive temperatures and germination conditions without influencing the quality of minimally processed fruit and vegetables.</p>

Name thesis:degree_name

MS in Agriculture - Food Science and Nutrition

Discipline thesis:degree_discipline

Food Science and Nutrition

Year dc:date.available

2016

Author dc:creator

• Rossi, Franca Gabriela

Contributors dc:contributor

• Amanda Lathrop

• Alfalfa sprouts
• biological control
• Escherichia coli O157:H7
• fresh-cut apple slices
• Pediococcus pentosaceus
• Pediococcus acidophilus
• Lactic Acid Bacteria (LAB)
• Lactobacillus plantarum
• Listeria monocytogenes
• Salmonella spp.
• Food Microbiology

Identifier

10.15368/theses.2016.39

OAI identifier oai:identifier

oai:digitalcommons.calpoly.edu:theses-2721