Estimation of Color of Durum Wheat. Comparison of WSB, HPLC, and Reflectance Colorimeter Measurements

Color is an important parameter involved in the definition of semolina and pasta quality. This character is mainly due to natural pigments (carotenoids) that are present at different levels in cereals and cereal products, due to botanical origin, growing conditions, distribution in the kernel, and technological processes. In food industries, color measurements are usually performed by means of automatic instruments that are rapid and safe, as alternatives to the chemical extraction methods. In this study, automatic measurements (CIE, color-space system L*, a*, b*), water-saturated butanol (WSB), and HPLC determinations have been applied to evaluate the carotenoid content in whole meals and respective semolina samples produced from wheat cultivated in the years 2001 and 2002. In whole meals, total carotenoids, determined by HPLC, were about 3.0 μg/g (2001) and 3.5 μg/g (2002) calculated on dry weight (dw) and about 3.0 and 3.2 μg/g dw in corresponding semolina samples. The b* values for the same period were 19.78 and 15.75, respectively, in raw materials and 20.03−21.67 in semolina. Results have confirmed lutein and β-carotene as the main components mainly responsible for the yellow color in wheat grains. The ability of the index b* to express natural dyeing was dependent on sample characteristics as demonstrated by the relationships found between this index and pigments, although the best correlation resulted between HPLC and WSB. Keywords: Carotenoids; HPLC; cereals; yellow index; WSB