Fabrication of penicillin G portable microbiological test plate for on-farm antibiotic residues in milk

Antibiotic residues in animal-derived food products such as milk pose a potential health risk to consumers. A portable antimicrobial screening test plate was fabricated particularly for on-farm testing of milk. A cold-water soluble compound gelling agent composed of guar gum (GG) and konjac glucomannan (KG) was prepared and its properties were optimized for enhancing performance of the test plate. A ratio of 4:6 (GG:KG) showed improved gel strength, cohesiveness, transmittance, and water diffusion of the compound gel. Microbial colony number and size were also increased. The test plate displayed a minimum inhibition concentration of 4 µg/L penicillin G and clearer zone of inhibition. Detection time was also significantly reduced to approximately 9–15 h compared to the conventional agar plate method. The plastic film test plate with optimized compound gel demonstrated tremendous potential for detection of antibiotics in milk.