Evaluation of detection methods for Alicyclobacillus spp, aerobic mesophilic microorganisms and yeasts and moulds

Sammanfattning: For the fruit juice industry, control of microbial growth is important to keep a high quality and safety of products. Several kinds of microorganisms are important to consider. This project focused on Alicyclobacillus spp., a gram-positive, spore-forming, strictly aerob spoilage bacteria able to grow at low pH of 3-6 and the spores survive pasteurization of 86–96 degrees C and 2 min. The project also concerned mesophilic aerobic microorganisms and yeasts and moulds. Several methods for detecting and enumerating these microorganisms were evaluated. Methods from IFU (International Fruit and Vegetable Juice Association), NMKL (Nordic Committee on Food Analysis) and several in-house industry methods were used, as well as Compact Dry plates and the PCR-based Veriflow method. Due to issues with linearity and over growth of agar plates, few comparable results were achieved, and the results were based on other factors: Incubation time, theoretical recovery and simplicity. For Alicyclobacillus spp., the IFU method and the Veriflow method was deemed the most efficient in terms of time and specificity. For yeast and moulds, the in-house method shows the most promise due to the short incubation time and comparable results to the NMKL-method. For mesophilic aerobic microorganisms the NMKL method and Compact Dry TC was deemed the most efficient.