Pigmented maizes: Anthocyanin profile and content

In recent years, countries such as Bolivia, Germany, China, the U.S.A. and Mexico have increasingly focused on the growth and development of pigmented maize cultivars and hybrids. Pigmented maize cultivars produce kernels of multiple colors, and are included among the 346 described races of maize. These pigments can include yellow, black, purple, blue, red and orange, as well as other less common shades. The blue-red coloration of pigmented maize is caused by the high concentrations of phenolic compounds called anthocyanins, included of the flavonoids group. These chemical compounds are contained in the pericarp, the aleurone layer and between the endosperm of the grain. Anthocyanins give a pigmented color to maize products and add nutraceutical value (antioxidant capacity). Anthocyanins are present as heterosides, and their structures are based in the aglycone form (C3-C6-C3 backbone). Attached to the aglycone, are hydroxyl and methoxyl substituents in different positions, which can yield a molecule named anthocyanidin. Only six anthocyanidins are found in fruits and vegetables. Anthocyanidins can be linked to sugars especially glucose, galactose, rhamnose and various other disaccharides and trisaccharides. Anthocyanins can be acylated by the acylation of sugar residues with organic acids, such as aliphatic or cinnamic acids. The most common analysis applied to study the profile and content of anthocyanins is HPLC, generally coupled to UV, DAD, MS, or HSCCC (high-speed counter-current chromatography). In this chapter, the anthocyanin contents of some colored maize grains are described along with their anthocyanin profiles. According to several profile analyses performed by different research groups, the main anthocyanins contained in blue and purple maize cultivars are cyanidin 3-glucoside, cyanidin 3- galactoside, pelargonidin 3-glucoside, malvidin 3-glucoside, peonidin 3-glucoside and some malonyl acylated derivatives. Furthermore, it has been reported that purple and blue maize cultivars from China and Mexico have the highest anthocyanin contents, at up to 3,045 mg·kg ^-1. Pigmented maize kernels can be used to obtain a variety of natural colorants but are mainly used to produce foods that preserve the original anthocyanin contents in order to provide additional health benefits for consumers.