Assessment of water activity and molds and yeasts contamination in honey traded on São Paulo city - SP, Brazil

Abstract

Water activity - Aw (Aqualab 3TE - Decagon) and molds and yeasts counting were assessed in 60 honey samples traded on open-air markets, supermarkets and natural products establishments at Western region of São Paulo city. Water activity measures showed a mean value of 0.578, and 0.027 as standard deviation, being 0.489 and 0.661 the minimum and maximum values, respectively. Molds and yeasts counting (performed on culture containing 2 and 20% dextrose potato agar) presented the minimum, median and maximum values of <0.5x1; <0.5x1 e 3.9x10² CFU/g respectively on 2% dextrose agar, and <0.5x1; 0.5x10 e 3.9x10² CFU/g, respectively on 20% dextrose agar. No significant difference in mold/yeast counting on 2 and 20% dextrose agar was evidenced; although high rate of absence of mold and yeast growing was observed onto 2% dextrose agar. In conclusion, 59/60 (98.33%) samples presented low probability for fermenting process, as these honey specimens showed low counts of most and yeast (<15 CFU/g) and/or Aw (<0.61). Of 60 samples, only one (1.67%) showed a potential fermenting condition owing to the counting value of >100 CFU/g and Aw >0.61. Further studies should be carried out to investigate the culture medium osmolarity for quantifying and identifying molds and yeasts