The fungal problem in thermal processed beverages

Fungal spoilage of thermally processed beverages by heat-resistant moulds (HRM), heat-sensitive moulds (HSM) and yeasts is a widespread problem for the beverage and juice industries. These beverages and juices can be classified as hot-filled and aseptically-filled or cold-filled. Since they are heat-processed, both groups can be spoiled by heat-resistant microorganisms such as the HRM. These fungi produce ascospores that can not only survive the heat treatment given to these beverages but also be activated and grow in the product during storage. These ascospores have been found in several ingredients such as sweeteners, juice concentrates, juice purees and powders, pectin, protein powders, vitamin powders, and so on. Hot-filled beverages can incur additional spoilage due to the activation of ascospores of HRM found in the empty PET bottles or in the beverage processing environment. Hot-filled as well as cold-filled or aseptically filled beverages can also be environmentally contaminated by heat-sensitive fungi causing several types of spoilage. HSM and yeasts may be introduced to the processing facilities through ingredients, air, water and packaging and potentially contaminate the beverages. The eradication of some of these microorganisms from the equipment presents a big challenge since they are involved in biofilm formation which protects them from the effect of sanitizers. This manuscript provides a short review of the fungal problems in thermal processed beverages including the sources of contamination as well as spoilage prevention and highlights the need for further research in this field.