We analysed the effect of adding rosemary and tocopherol extracts, two natural antioxidants, on the colour stability of paprika stored at different temperatures and degrees of relative humidity. Any possible synergistic effect of their joint use was also investigated. The experimental data concerning colour loss, as determined by the ASTA 20.1 method, fitted first-and second-order kinetics, which provided the rate constants of colour loss and half-lives of the samples. The first finding concerned the antagonistic effect between storage temperature and humidity. The antioxidants had a clear protective effect on colour stability in all the conditions assayed, the superior effect of one or the other depending on the storage temperature. A synergistic effect of both antioxidants at temperatures between 25 and 40°C was evident. The experimental data referring to colour loss for most of the storage conditions assayed fitted second-order kinetics best.

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The colour loss occurring in a paprika made from the dehydrated fruits of pepper, Capsicum annuum L. var. Ocal (control), was compared with the colour lost by a similar paprika submitted to an industrial sanitation process involving water vapour. The heat treatment resulted in a considerable greater loss of colour when the paprika was stored at 25°C in different relative humidities (0, 23, 57 and 75%) compared with the control paprika. The study also analysed the effect of adding a natural antioxidant (rosemary extract at 1%) to the heat-treated product. In this case, colour stability increased significantly in all the conditions assayed; the lower the humidity, the greater the increase in stability.