Uso de espectroscopia no infravermelho médio e análise discriminante por quadrados mínimos parciais na determinação de adulterações em óleos de andiroba, prímula e rosa mosqueta

Abstract

Vegetable oils and fats are the products obtained from the glycerides of fatty acids of vegetable species and are widely employed in various branches of industry i.e: food, cosmetic, pharmaceutical, among others. Throughout the industries, the cosmetics industry is a highly dynamic market with the launch of new products at an accelerated rate. In recent years, new concepts are also emerging as is the case of cosmeceuticals and nutricosmetics oils. These facts increase the demand for certain oils, therefore, producers and traders may adulterate authentic oils, with lower valued oils, in order to increase profits and attend the demand for the products, thus becoming a major concern for regulatory agencies. In the cosmetics market, great emphasis is given to Andiroba oil, Rosehip and Evening Primrose, especially for therapeutic properties resulting in a high valuation. In this context, the present work was developed with the purpose to evaluate the viability of Mid-infrared Spectroscopy measurements combined with the method of Discriminant Analysis by Partial Least Squares to detect possible adulterations in Andiroba (Carapa guianensis), Evening Primrose (Prímula veris ou Oenothera biennis) and Rosehip (Rosa moschata ou Rosa rubiginosa) oils. Forty samples were used for each of the authentic oils, for the Andiroba oil 192 samples were adulterated with corn oil (96 samples) and soybean oil (96 samples) prepared in the following proportions: 5%, 10%, 15% and 20% (m/m) with 24 samples for each concentration of adulterant. While for the Evening Primrose and Rosehip oils, were made 288 adulterations with corn oil (96 samples), Soybean oil (96 samples) and sunflower oil (96 samples) in the same proportions as andiroba oil: 5%, 10%, 15% and 20% (m/m). The samples were analyzed by Mid-infrared spectroscopy - MIR associated with the chemometric method Discriminant Analysis by Partial Least Square - PLS-DA in order to discriminate the authentic of the adulterated samples. They were built 3 PLS-DA models, one for each type of oil study. All developed models showed high sensitivity and specificity with values equal to 100% (highest rating), i.e all samples were classified correctly independently of type of adulterant oil, in either the training set and test set. Thus, the employed methodologies can be applied to monitoring the product of Andiroba, Primrose and Rosehip oils and their blends adulterated with soybean, corn and sunflower oils. The methodologies can be used in analysis in-situ.