A novel sensor based on bead-counting of purple sweet potato tapioca pearl for freshness monitoring of shrimp

•Purple sweet potato (PSP) tapioca pearl as a colorimetric pH sensor was developed.•The change in color of the PSP tapioca pearl correlated with the change in pH of beverages.•PSP tapioca pearl was sensitive to ammonia and pH changes.•Various tapioca pearls stacked in a pipette tip was used as a distance based colorimetric sensor.•The bead counting concept was used to monitor the freshness of shrimp.