Capsaicin determination in chilli fruit using a new solid-state sensor based on reflectance transduction

The component that is responsible for pungency taste of the chilli is capsaicin. Chilli hotness is proportional to the capsaicin concentration, which can be determined based on the colour changes of Gibbs reagent when reacting with capsaicin in an alkaline medium. Immobilisation of Gibbs reagent onto silica nanoparticles (approximately 80 nm in size) was carried out to construct a new optical sensor for the direct and rapid determination of capsaicin in chilli fruits. The optical sensor was based on a clear colour change of the sensor from white to blue when exposed to capsaicin. A good response was found towards capsaicin concentrations in the range of 25.0-300.0 ?M with detection limit of 18.6 ?M in an alkaline medium of pH 10. The results were reproducible with a good relative standard deviation (RSD) in the range of 2.3-5.3%. Silica nanoparticles as a matrix of immobilisation for Gibbs reagent enhanced the sensor performance in terms of response time (30 s), sensitivity, and detection limit compared to immobilisation matrix such as XAD beads evaluated in this study. The presence of small amount of interfering compounds in the chilli fruit had no significant effect on the sensor response. The optical capsaicin sensor was successfully developed and applied to the chilli samples and demonstrated comparable results with the HPLC standard method. Copyright � 2016 American Scientific Publishers All rights reserved.