Dissecting Rice Pearl Character, an Important Added Value in High-Quality Temperate Mediterranean Japonica Cultivars

Rice holds an important sociocultural meaning in Europe, and especially in the gastronomy of its Mediterranean regions, as it is used for world-famous recipes such as Risotto in Italy and Paella in Spain. Paella is prepared with highly appreciated pearled (white-core) rice cultivars such as Bomba or Montsianell, while Risotto is prepared with white-belly Carnaroli cultivar among others. Pearled rice grains have a limited and enclosed translucent zone which is physicochemically different from stress-induced chalky grains present in any rice cultivar at a low rate, and whose opaque area covers at least three quarters of the grain surface. We have studied for the first time the physicochemical aspects of grains from pearled white-belly, white-core and crystalline rice grains of Mediterranean japonica rice cultivars in comparison with their defective stress-induced chalky grains in order to shed some light on their differences. Spanish Bomba and Montsianell white-core (pearled) cultivars have similar physicochemical behaviours but are clearly different from white-belly Carnaroli cultivar. Furthermore, their pearled fractions differ in some traits from stress-induced chalkiness, especially in terms of amyloplastic integrity, relative amylose content and relative storage protein content. This study establishes some physicochemical differences between white-belly, white-core and stress-induced defective chalky grains and will guide future studies to unravel this much-appreciated pearl character in the Mediterranean gastronomy.