Microbial dynamics, alkaloid stability, and lactose degradation of poppy seed kefir during fermentation and cold storage

Adding poppy seeds to kefir significantly influences its microbiological profile and chemical composition. This study evaluated four kefir formulations: control, kefir spiked with low and high concentrations of opium alkaloids (OAs), and one with naturally contaminated poppy seeds. Samples were analysed during fermentation (0, 6, and 24 h) and following one week of cold storage. Key parameters were monitored, such as pH, microbial counts, carbohydrate fractions, organic acid profiles, and OA levels. Our findings reveal that kefir with poppy seeds exhibits distinct microbial dynamics, accelerated lactose degradation (with lactose levels dropping to as low as 0.3 g/100 g), and elevated production of lactic acid. Notably, while most OAs remained relatively stable throughout fermentation and storage, morphine levels decreased by over 50 % after cold storage. These results suggest that the intrinsic microbiota of poppy seeds enhances the fermentative process, improving lactose reduction and favouring the production of kefir more suitable for intolerant consumers. Furthermore, the importance of controlling OA levels to ensure food safety is highlighted. This study provides a solid basis for the development of functional fermented dairy products. • The addition of poppy seeds accelerates kefir fermentation and reduces lactose. • Lactose levels in kefir with poppy seeds drop to 0.3 g/100 g. • The microbiota of kefir and seeds impacts fermentation and product stability. • Opium alkaloids remain stable, but morphine can be decreased by up to 50 %. • This improved kefir is a promising option for lactose intolerant consumers.