Çeşitli yetiştirme ortamlarının mikro filizlerin şiga toksin üreten escherichia coli (Stec) ve jenerik escherichia coli kontaminasyonu için değerlendirilmesi / Evaluation of various growing media for shiga toxin-producing escherichia coli (Stec) and generic escherichia colicontamination of microgreens

Abstract

Nowadays, consumers' demand for healthy and fresh foods has been increasing. Raw seed sprouts have gained worldwide popularity due to their healthier and higher nutrient content. As a new class of seed sprouts, microgreens are immature seedlings of crops consumed raw including lettuce, radish, pea, and etc. When microgreens are contaminated with pathogenic microorganisms, they pose a health risk. Pathogen bacteria can pass to microgreens from seed, irrigation water and growth medium. In this study, the contamination of shiga toxin producing Escherichia coli O157:H7 and generic Escherichia coli were evaluated for lettuce and radish microgreens grown in peat and perlite watered by spray and bottom irrigation. Lettuce and radish seeds were grown in nalidixic acid resistant E. coli strains inoculated peat and perlite media. Survived cell concentrations were counted in the edible and inedible parts of the grown microgreens. Survival of E. coli strains was also investigated in growth media and plant nutrient solution. In this study, the population of E. coli O157:H7 in the edible portion of radish microgreens grown was found in ranges of 4.48-4.70 log CFU/g in peat and 5.82-6.07 log CFU/g in perlite. While E. coli O157:H7 was not detected in edible parts of lettuce in peat medium, E. coli O157:H7 populations were detected between 1.55 and 1.83 log CFU/g in perlite. Pathogenic E. coli was found to be in higher populations in radish compared to lettuce, perlite compare to peat and, edible parts of plants compared to inedible parts. Irrigation type did not affect the cell population transferred to the edible portion of microgreens (P>0.05). At the end of day 28, E. coli O157:H7 showed similar survival trends to generic E. coli, but the population was significantly lower in perlite and plant nutrient solutions (P<0.05). Based on these results, microgreens can survive long enough and in high level that would cause a risk for food safety when the plant growth environments are contaminated with E. coli bacteria. E. coli can transfer from contaminated growth medium to the edible portion of microgreens. Risk reduction strategies need to be developed to reduce contamination in microgreens grown in perlite and prevention of E. coli O157:H7 contamination to microgreens should be the main objective.