Editor's Choice article for July 2025

‘Analysis of the reasons for reduced viscosity in ambient yoghurt’ by Hongfa Zhang, Chunping You and Yunqing Wang has been selected as the Editor's Choice article for the July 2025 issue of the International Journal of Dairy Technology.

The authors, from the State Key Laboratory of Dairy Biotechnology and associated institutions in Shanghai, China, present an investigation into an issue of growing concern for the ambient yoghurt sector: unexpected viscosity reduction during shelf life. Unless resolved, this has implications for consumer satisfaction and brand integrity.

Traditional microbiological methods failed to detect any obvious abnormalities in the affected products, prompting the researchers to devise a new approach to identify potential microbial causes. By developing a method involving NaOH-assisted separation of colloids and microbial cells, followed by microscopy and DNA sequencing, the authors were able to trace the issue to Geotrichum candidum, a starch-degrading fungus likely introduced via contaminated granulated sugar.

The study not only identified a root cause of product thinning that had eluded standard tests but also demonstrated how rapid, practical analytical techniques can support more reliable quality control in ambient dairy products. The authors' methodology—combining physical separation, universal genomic DNA extraction and internal transcribed spacer (ITS) sequencing—appears to provide a robust methodology for microbial traceability that may have broader applications in the dairy industry.

Importantly, the problem was resolved in subsequent production batches following improved heat treatment of the sugar, illustrating the practical impact of this research.