Application of bromocresol purple nanofilm and laser light to detect mutton freshness

Optical waveguide gas sensor with bromocresol purple (BCP) nano-film (70–80 nm) composited with silicone deposited on surface of K+-ion exchanged glass slide was fabricated and applied to detect amine gases released during mutton spoilage to test mutton freshness with the help of laser light (632 m). Gas sensing measurements (output light intensity vs. time) proved its high selectivity and good sensitivity (0.01 ppm) toward amines among volatile organic compounds. The optimal fabricating condition (2600 rpm, 0.10% BCP, 5.17% silicone) was selected experimentally, displaying 1 s and 12 s response-recovery time toward gases released from mutton samples stored at 5 °C and 25 °C respectively. The sensing mechanism was explained by combination and competition of diffusion-reaction, considering deprotonating reaction of bromocresol purple molecules and molecular size of analyte gases in diffusion process. UV–vis spectroscopy was used to select the specific wavelength of laser light source in optical waveguide performance and to detect the total volatile basic nitrogen contents in mutton sample to confirm the practicability of as-prepared optical waveguide sensor in detecting mutton freshness. The fabricated sensor is able to detect 7.2 mg/100 g gases released from mutton decomposition, providing a simple, fast, and cheap method to detect meat freshness.