The evaluation of chilli hotness using amperometric capsaicin biosensor-based enzyme that was immobilized covalently to the surface of modified acrylic microspheres is the first of its kind presented in this work. The immobilization of enzyme covalently to the surface of microspheres via succinimide groups prevented the leaching of the enzyme. The enzymatic reaction between horseradish peroxidase-capsaicin in the presence of hydrogen peroxide, which was mediated by vinyl ferrocene, enabled the current measurement at a low potential (0.22 V). Besides, the pungency level of the chilli that was proportional to the capsaicin concentration was measured using this method. This biosensor gave a linear response range towards capsaicin from 0.75�24.94 ?M (R2 = 0.992) with a detection limit at 0.39 ?M. Moreover, the relative standard deviation (RSD) for reproducibility study was 8.2% (n = 7). Therefore, this biosensor was successfully applied for evaluation of chilli hotness in chilli sample, as well as in comparison with a standard method that employed the HPLC method. � 2016 Elsevier B.V.

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.

The fabrication of an optical biosensor based on stacked immobilisation of 3-methyl-2-benzothiazolinone hydrazone (MBTH) in sol-gel/butyl acrylate hybrid film and horseradish peroxidase (HRP) in chitosan film for capsaicin detection was studied. The optimum volume ratio of sol-gel to butyl acrylate was 1:0.5 (v/v). Peroxidase was immobilised in chitosan film deposited on top of the hybrid sol-gel/butyl acrylate film containing MBTH. The reaction between capsaicin and MBTH in the presence of HRP and hydrogen peroxide as oxidative agent was studied. The finding indicated that HRP catalysed the oxidative coupling reaction between MBTH and capsaicin thus producing red-coloured azo-dye compounds that could be observed at the wavelength of 505 nm. The colour intensity of the product was found to increase in proportion to the capsaicin concentration after 20-30 s of exposure. The linearity of the biosensor towards capsaicin was in the concentration range of 0.2-4.0 mM with detection limit of 0.17 mM. Relative standard deviation (RSD) values of reproducibility were 5.57-6.33%. The developed biosensor correlated well with the standard method, HPLC for the determination of capsaicin concentration in real samples.� 2013 Elsevier B.V. All rights reserved.