Talanta 68 (2006) 1505–1511 Durum wheat adulteration detection by NIR spectroscopy multivariate calibration Marina Cocchi a,∗ , Caterina Durante a , Giorgia Foca a , Andrea Marchetti a , Lorenzo Tassi a , Alessandro Ulrici b a Dipartimento di Chimica, Universit` a di Modena e Reggio Emilia, via Campi 183, 41100 Modena, Italy b Dipartimento di Scienze Agrarie, Universit` a di Modena e Reggio Emilia, via Kennedy 17, 42100 Reggio Emilia, Italy Received 3 March 2005; received in revised form 1 July 2005; accepted 4 August 2005 Available online 15 September 2005 Abstract In the present work, we explored the possibility of using near-infrared spectroscopy in order to quantify the degree of adulteration of durum wheat flour with common bread wheat flour. The multivariate calibration techniques adopted to this aim were PLS and a wavelet-based calibration algorithm, recently developed by some of us, called WILMA. Both techniques provided satisfactory results, the percentage of adulterant present in the samples being quantified with an uncertainty lower than that associated to the Italian official method. In particular the WILMA algorithm, by performing feature selection, allowed the signal pretreatment to be avoided and obtaining more parsimonious models. © 2005 Elsevier B.V. All rights reserved. Keywords: NIR spectroscopy; Multivariate calibration; PLS; WILMA; Wavelet transform; Durum wheat adulteration 1. Introduction NIR spectroscopy is nowadays a widespread technique used in many fields of analytical chemistry, including the quality control of foodstuffs [1–4]. In comparison with other analytical techniques, such as classical wet analysis, its advantages are essentially rapidity, cheapness and the fact of being a non-destructive method. Furthermore, in the last two decades, the application of NIR spectroscopy as routine quality control analysis has gradually increased thanks to the possibility of its on-line implementation [5–8]. In the field of cereal analysis, NIR spectroscopy in associa- tion with chemometrics has been used since the late seventies [9], being successful in modelling many quality variables, such as protein, moisture, dietary fibre contents, and wheat hardness [10–16]. More recently, the applications of NIR spectroscopy on cereals have been focused on the predic- tion, only partially successful, of functional and technological parameters, such as flour yield, percentage of damaged starch, ∗ Corresponding author. Tel.: +39 059 2055029; fax: +39 059 373543. E-mail address: cocchi.marina@unimore.it (M. Cocchi). water absorption, dough development, time extensibility and loaf volume [9,12]. However, to our knowledge, an interesting composition- related aspect of wheat has not yet been considered. Wheat for human feeding can be essentially distinguished in two species, i.e., durum wheat (Triticum durum) and bread wheat (Triticum aestivum), which are characterized by different chemical and physical properties that give rise to different quality, nutritional contribution and, consequently, commer- cial value of the final products [17–20]. Italian law establishes that pasta can be made only by durum wheat semolina and water [21]. The addiction of bread wheat flour is an adul- teration that leads to a product with a scarce resistance to cooking and therefore of lower quality. However, since the accidental contamination of semolina with bread wheat dur- ing harvesting, transport or storage remains possible, it is allowed the presence of bread wheat flour in percentages not higher than 3% [22]. The problem of durum wheat adulter- ation with common bread wheat is of particular interest in the Italian, French and Spanish markets, where semolina is the only allowed constituent for pasta, while in the north Euro- pean countries both bread and durum wheat are allowed. 0039-9140/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2005.08.005