Abstract
Food spoilage and its contamination with yeast and mold is a serious problem of food industry. Despite the high fat content, mayonnaise is an attractive substrate for food spoilage microorganisms. The aim of this study was to develop a method for yeast identification in mayonnaise and to test commercially available mayonnaises for the presence of these contaminating microorganisms. Based on the sequencing of intergenic regions ITS1 and ITS2, we identified a yeast microorganism that causes mayonnaise spoilage. We found that DNA sequences were more than 99% identical to the GenBank DNA sequences from Pichia kudriavzevii. We developed a specific to P. kudriavzevii TaqMan probe and primers. The reaction conditions were optimized regarding to the components concentration and temperature cycle. The minimum amount of P. kudriavzevii DNA that could be detected by developed method was 50 fg. The minimal number of P. kudriavzevii cells that could be detected by developed method without pre-enrichment was 50. We tested verified method with DNAs from microorganisms of different taxonomic groups that were obtained from three collections of microorganisms. Finally, we analyzed 20 different brands of mayonnaise from 14 producers and 10 different brands of mayonnaise sauce from seven producers. We determined the Cq parameter that characterizes transition of the fluorescence curve to the logarithmic phase and, therefore, correlates with the extent of sample contamination with P. kudriavzevii yeast. P. kudriavzevii was detected in six analyzed samples of mayonnaise and one sample of mayonnaise sauce.
Highlights
Food spoilage and its contamination with pathogenic microorganisms is a serious problem of food industry
We found out that all sequences were more than 99% identical to the deoxyribonucleic acid (DNA) sequences from P. kudriavzevii
The sequenced fragments were analyzed using the data from the Boldsystem that confirmed that the identified microorganism was P. kudriavzevii
Summary
Food spoilage and its contamination with pathogenic microorganisms is a serious problem of food industry. Often, contaminating agents are eukaryotic microorganisms, such as yeast and molds. Microbial contamination is very common for the products with a high fat content, e.g., mayonnaises. Despite the high fat content, Among potential sources of microbial contamination are eggs, because egg yolk is one of the main mayonnaise ingredients. Bacteria, such as Escherichia coli, Shigella spp. and yeasts, such as Candida albicans (Lee et al 2017), and Coxiella burnetii (Tatsumi et al 2006) were found in eggs; for the latter, the identification method using real-time PCR has been developed
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