Abstract
The spice paprika (Capsicum annuum and frutescens) is used in a wide variety of cooking methods as well as seasonings and sauces. The oil, paprika oleoresin, is a valuable product; however, once removed from paprika, the remaining spent product can be used to adulterate paprika. Near-infrared (NIR) and Fourier transform infrared (FTIR) were the platforms selected for the development of methods to detect paprika adulteration in conjunction with chemometrics. Orthogonal partial least squares discriminant analysis (OPLS-DA), a supervised technique, was used to develop the chemometric models, and the measurement of fit (R2) and measurement of prediction (Q2) values were 0.853 and 0.819, respectively, for the NIR method and 0.943 and 0.898 respectively for the FTIR method. An external validation set was tested against the model, and a receiver operating curve (ROC) was created. The area under the curve (AUC) for both methods was highly accurate at 0.951 (NIR) and 0.907 (FTIR). The levels of adulteration with 100% correct classification were 50–90% (NIR) and 40–90% (FTIR). Sudan I dye is a commonly used adulterant in paprika; however, in this study it was found that this dye had no effect on the outcome of the result for spent material adulteration.
Highlights
Paprika is a spice best known for its use in a wide variety of cooking methods for both flavour and colour
The NIR spectra of 100% paprika and spent material show that there is a clear distinction between the bands that correspond to oil, C-H bonds, (4100–4400 cm−1, 5350–6000 cm−1 ) and the water band
Following the raw data collection of the spent and paprika samples, the authentic paprika samples were randomized so as to prevent a group of similar products from similar suppliers being grouped together. They were split into a training set for use in the model development (n = 104) and test set for use in the validation set (n = 30). This allowed a separate set of authentic samples to be used for external validation of the methods, to the procedure explained by Riedl et al [39]
Summary
Paprika is a spice best known for its use in a wide variety of cooking methods for both flavour and colour. It can be found in a variety of foods, including seasonings and sauces [1]. The characteristic reddish colour is due to the presence of carotenoids [1] Spices such as paprika are often the target for food fraud as they are valuable commodities, and fraudsters aim to deceive consumers into thinking they are buying authentic and safe spices [3]. Different forms of adulteration in paprika has been found to include substitution adulteration with waste or inferior products, falsely declared origin [5] and addition adulteration with the use of illegal dyes such as the commonly found Sudan I and IV according to the
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