Improved sensitive fluorescent/visible dual detection count plate for mold and yeast in food

Abstract An improved sensitive fluorescent/visible dual detection count plate for mold and yeast was designed to improve the mold and yeast detection efficiency and guarantee food security. The effect of substrate, co-solvent and nonionic surfactant on mold and yeast count plate detection performance was investigated. LAP/lipase as extracellular dual-enzyme system hydrolyzed 0.2 mg/mL of 5-bromo-4-chloro-3-indolyl phosphate disodium salt and 4-nitrophenyl phosphate disodium salt hexahydrate and released chromophores p-nitrophenol, and dehydroindigo dimer to chromogenic colony. Detection was achieved by recording the chromogenic mold and yeast colony-forming units (CFU). Moreover, 4 μL/mL of co-solvent water-ethanol was used as fluorescent sensitizer for colonies, while 0.1 % Tween-20 (w/v), 0.1% Tween-80 (w/v) and 0.1% TritonX-100 (w/v) facilitated growth rate and obvious expression of extracellular dual enzyme system LAP/lipase. Counting results of the fluorescent/visible count plate (34 h) have not significantly different from the national standard GB 4789.15-2016 agar plate (5 days) (P>0.05). Results of fluorescent/visible count plate for the detection of mold and yeast in actual food samples were 97.5 % and 98.6 % in accordance with the results of the national standard method. This work provided a convenient, rapid, and sensitive detection of mold and yeast.