Assessing Food Safety Risks in Homemade Fermented Beverages: A Case Study with Quinoa Rejuvelac

Spontaneous fermentation processes can promote uncontrolled microbial growth and increase the risk of foodborne contamination, making the characterization of artisanal beverages essential for consumer safety. This study investigated the microbial composition of quinoa-based rejuvelac, a homemade fermented drink often perceived as a functional food, with the objective of identifying potential microbiological hazards associated with its preparation. High-throughput sequencing of the 16S rRNA V3-V4 region was combined with shotgun metagenomics to profile bacterial communities and recover metagenome-assembled genomes. The analysis revealed a strong dominance of Pseudomonadales, mainly Pseudomonas, Acinetobacter, Enterobacter and Burkholderiales, while lactic acid bacteria typically responsible for stable and safe fermentations were not detected. Shotgun metagenomics recovered medium- to high-quality genomes from Burkholderiaceae and Clostridiales, supporting the overrepresentation of non-beneficial taxa and indicating deviations from expected fermentation microbiota. These results show that the spontaneous preparation of rejuvelac may favor bacterial groups associated with environmental contamination rather than fermentative pathways, underscoring the importance of hygiene practices, controlled starter cultures and monitoring strategies to mitigate microbiological risk. The study highlights the need for improved safety standards in artisanal fermented foods to prevent unintended microbial contamination and protect consumers.