A comparative study of flaxseed gum effect on Lactobacillus acidophilus genes expression, and textural, sensory, structural, and microbiological properties of synbiotic Iranian white cheese

Flaxseed gum (FG), a natural polysaccharide with prebiotic potential, may enhance probiotic functionality by modulating bacterial gene expression and improving viability in synbiotic dairy matrices. This study evaluated the effect of FG (2.5% and 5%) on Lactobacillus acidophilus gene expression, viability, sensory properties, texture, and microstructure in Iranian white cheese. Four functional genes were selected for their roles in amino acid biosynthesis, stress adaptation, metabolic regulation, and cell wall integrity. Gene expression was assessed on days 15 and 60 using real-time PCR, while bacterial viability was measured by PMA-qPCR and plate count methods. Significant differences in relative gene expression were observed across all treatments and both time points (day 15 and day 60), with distinct fold-change values for each gene. All gene expressions peaked on day 15 and declined by day 60, possibly due to adaptive stress responses or diminishing FG effect. On day 60, the FG 5% treatment exhibited the highest L. acidophilus viability (1.55 × 10⁷ CFU/g), outperforming both the control and other treatments, and highlighting its superior protective effect during cheese ripening. Sensory analysis revealed FG 5% had the highest general acceptance score, with textural and structural parameters (springiness, chewiness, and porosity) comparable to or improved over control. SEM and ImageJ analyses confirmed enhanced matrix cohesion, reduced porosity (7%), and finer fat dispersion (10 μm) in FG 5%. These findings show that FG may support probiotic viability and cheese quality, offering new insight into the molecular basis of probiotic survival and a promising strategy for developing functional dairy products.