Determinants of wheat noodle color

Noodles are a leading food in the world, and color is a key determinant of consumer acceptance. In this review the two prominent forms of wheat noodles are considered: white salted and alkaline. Many of the preparation and evaluation strategies are the same for both, with prominence placed on 'brightness' (L*) or a lack of discoloration (ΔL*), and the absence of 'specks.' All raw noodles darken over time. Increasing the protein content of flours almost always translates into darker noodles. Greater discoloration is also associated with higher flour extraction rates, higher ash contents, and higher starch damage. Increasing storage time, dough water absorption, and temperature all often lead to greater discoloration. There is a large range in noodle color variation, and much of this variation is associated with genetics. Consequently, much research has been devoted to methods of screening germplasm, either as whole seeds, meals, flours, or noodle sheets. Polyphenol oxidase (PPO) is a primary culprit in noodle discoloration and has guided much of the research on noodle color. It is now possible to select germplasm with very low levels of PPO through the use of efficacious phenotype screens and the use of molecular markers. The success of this research has provided the opportunity to select wheat breeding lines with nil PPO activity, and to combine favorable alleles at multiple PPO loci. Yet, when noodles are prepared, we continue to observe discoloration. As our ability to minimize PPO activity increases, this 'non-PPO' discoloration has become more important. Perhaps the 'holy grail' is a noodle that never discolors, and has the 'perfect' level of a* (redness, zero?) and b* (yellowness/creaminess). Published 2018. This article is a U.S. Government work and is in the public domain in the USA.