Rapid enumeration of low numbers of moulds in tea based drinks using an automated system

Area of Science:

• Food Science
• Microbiology
• Analytical Chemistry

Background:

• Aseptically prepared cold tea drinks lack preservatives, increasing the risk of microbial contamination.
• Heat-tolerant fungal spores (conidia and ascospores) can survive pasteurization, posing a health concern.
• Rapid detection of fungal contamination is crucial for ensuring the safety of these popular beverages.

Purpose of the Study:

• To develop a rapid and accurate method for detecting low numbers of fungal conidia and ascospores in tea-based drinks.
• To assess the efficiency of fluorescent staining combined with an automated counting system for fungal enumeration.

Main Methods:

• Fungal conidia and ascospores were inoculated into green and oolong tea samples.
• Samples were filtered through 0.8 μm nitrocellulose membranes to concentrate fungal propagules.
• Germinating fungi on membranes were fluorescently stained and counted within 90 seconds using an automated system (MGS-10LD).

Main Results:

• The method successfully detected very low fungal concentrations (as low as 1 CFU/100ml).
• Detection of all tested mould strains was achieved within 24 hours, significantly faster than conventional 72-hour plate counts.
• Automated counts showed high correlation (r² = 0.986) with conventional methods for slow-growing fungi.

Conclusions:

• The combined fluorescent staining and automated counting method provides rapid and accurate detection of fungal contamination in tea drinks.
• This technique is effective for both fast- and slow-growing fungi, offering a valuable tool for microbiological quality control.
• The method is applicable to tea-based and potentially other types of beverages.