Pasta brownness:: An assessment

Pasta colour is an essential factor in assessing pasta quality. It results from a desirable yellow component, an undesirable brown component and, under some drying conditions. a red component. The cause of pasta brownness is complex and its biochemical and technological basis is still a matter of controversy. This paper is a comprehensive review of the literature data in the light of results which have been recently obtained in our laboratory. Pasta brightness (L) is an indicator of the attenuation of the light reflected by pasta samples. Brownness is usually defined as 100-L, and brownish pasta is characterised by a low L value and a dominant wavelength in the 578 nm region. The contributions of cultivar and location to the variance of L are about 15% and 65%, respectively. Within the same cultivar, L decreases when the protein and ash contents increase but the basis of these relations ari not known. Pasta brownness is the result of an inherent brownness of the endosperm (the dominant parameter in the case of semolina scarcely contaminated by the peripheral parts of the grain), of the degree of purity of the semolina and of Maillard reactions when pasta are dried at high temperature. Inherent brownness of semolina could be due to a water-soluble copper protein (Matsuo's brown protein) and/or to the action of oxidising enzymes which would take place during grain maturation. The brown colour of spaghetti increases sharply with the ash content of the milling streams. Whether such brownness results from the inherent brownness of milling streams or from the action of polyphenol oxidase is not known. Kneading and extrusion of pasta have no significant effect on brownness. The formation of brown 'melanoidin' pigments due to the development of Maillard reactions is related to the reducing-sugar content of pasta and the drying parameters. Recommendations for future research are given, which include further genetic and physicochemical investigations of Matsuo's brown protein, the evolution of polyphenoloxidase activity during durum wheat grain maturation and the relationship between pasta brownness and the PPO activity of milling streams. (C) 2000 Academic Press.