Durum Wheat Lipoxygenase Activity and Other Quality Parameters that Affect Pasta Color

Abstract

Pasta yellowness is affected by different factors, the most important of which are intrinsic to the quality of semolina (natural carotenoid pigments, protein, ash, and lipoxygenase [LOX] activity) and processing conditions. Because all the parameters involved in pasta color are under the control of varietal and environmental factors, the role of the genotype, environment, and the interaction between genotype and environment on color expression were studied. Although the analysis of variance showed the genotype‐by‐environment interaction to be significant, a nonorthogonal analysis attributed a higher weight to genotype on parameters directly involved in color expression: β‐carotene content, yellow index, and LOX activity. Furthermore, the loss of pigments and yellow index after milling and processing was evaluated and correlated with all the parameters involved in the determination of final pasta color. The phase mainly responsible for pigment loss was pasta processing. A decrease of 16.3% in semolina β‐carotene content during pasta processing versus a 7.9% loss during milling was determined. The isoenzymatic forms LOX‐2 and LOX‐3, active at the pH of dough, were responsible for the loss of color in pasta products. Simple correlations and the linear multiple regression corroborated this finding. Hydroperoxidation activity at pH 6.6, bleaching activity, and ash content were responsible for 87% (R2 adjusted) of total variance, with each variable accounting for 57, 61, and 22% of the variation, respectively. This confirms that LOX activity is the main factor involved in the loss of color, while a secondary and lesser role can be seen for ash content. Therefore, a high pigment content, located in the interior of the whole grain, and a lower LOX activity in semolina must be the selection characteristics by which breeding programs obtain a bright yellow pasta.