Natural fermented beverages exhibit high physicochemical complexity due to microbial activity, which makes quality control challenging when using conventional methods that are often destructive, time-consuming, and poorly suited to turbid media. This study evaluates the feasibility of the SLIPI-1p (Structured Laser Illumination Planar Imaging – single phase) method as a non-destructive optical tool for monitoring the fermentation of natural beverages. Four commonly consumed plant-based matrices were investigated: pineapple, orange, apple, and bissap (Hibiscus sabdariffa), all subjected to spontaneous fermentation over a ten-day period. The optical extinction coefficient μₑ was measured daily using the SLIPI-1p setup and compared with conventional physicochemical parameters, namely pH and soluble solids content (°Brix). The results show a systematic increase in μₑ throughout the fermentation process for all beverages studied. This increase is strongly correlated with the decrease in °Brix, reflecting sugar consumption, as well as with the reduction in pH associated with progressive acidification of the medium. Statistical analyses reveal strong linear correlations between μₑ and °Brix, with coefficients of determination reaching up to 0.99 depending on the beverage matrix. These findings demonstrate that the SLIPI-1p method is capable of reliably detecting the biochemical and structural transformations associated with fermentation, even in highly turbid media. The speed, robustness, and non-invasive nature of this approach offer promising prospects for the development of rapid optical quality control tools suitable for both artisanal and industrial contexts.