BRT PhD Student and Project Manager Jan Staš will be defending his PhD thesis on September 09, 2025!

 

Title: “In vitro growth-inhibitory effect of plant-derived products against beverage-spoiling microorganisms”

Date: 9th September 2025

Time: 10:00am

Location: Faculty of Tropical AgriSciences, Room 313

Fruit juices may look fresh and delicious on the outside, but behind the scenes, acid-loving yeasts can cause spoilage long before the “best before” date. Traditionally, this problem has been managed with synthetic preservatives. However, with more consumers seeking natural “clean label” products, the food industry faces the challenge of keeping juice fresh without artificial additives. In this context, Jan’s research developed a new laboratory method that tests natural antimicrobial compounds directly in real juice rather than artificial lab media. Using this approach, the study identified plant-based substances that effectively combat spoilage yeasts.

 

Alongside this innovation, Jan and his team adapted the MTT colourimetric viability assay for use in opaque juice matrices, enabling rapid and sensitive assessments of yeast inhibition in cases where standard turbidity methods are unsuitable. The results revealed that pterostilbene, a compound found in plants such as blueberries, showed outstanding antifungal activity, while essential oils from lemongrass and fingerroot also proved highly effective and are already locally available in many tropical countries. Conversely, extracts from certain mangrove species did not emerge as promising low-cost options for juice producers in tropical regions.

 

The findings of this research open new opportunities for the development of natural, safe and effective methods to keep juice fresh, and delicious, for longer, contributing to the shift towards healthier and more sustainable food preservation practices.