Colorimetric detection of volatile organic compounds for shelf-life monitoring of milk

Abstract

Colorimetric nanosensors for monitoring food quality and shelf life providea an exciting development with obvious economic benefits. In this study, a colorimetric sensor based on silicon dioxide (SiO2) nanoparticles and Schiff's reagent to detect volatile organic compounds (VOCs) generated by the growth of spoilage bacteria in pasteurized whole milk stored at 7, 13, 15, and 19 °C was developed. Volatile organic compounds formed from microbial growth were detected using solid-phase microextraction (SPME) and gas chromatography. Volatile organic compounds levels were correlated with microbial growth (aerobic plate counts) and color change throughout the shelf-life period. Color changes due to VOCs generated by spoilage bacteria were detected at all storage temperatures except 7 °C. Nanosensor response correlated well with microbial growth in milk. Milk spoilage occurred at 32, 60, and 84 h at 19, 15, and 13 °C, respectively and could be detected colorimetrically. Color change, recorded as total color difference (ΔE) for the nanosensor, correlated well with aerobic plate counts (5.0–7.0 log10 CFU/mL) in milk (R2 = 0.81–0.96). This colorimetric sensor could be incorporated into food packaging to predict remaining shelf-life benefitting consumers as well as manufacturers and retailers and reducing food loss.