Effect of domestication on the digestibility of maize proteins

Abstract: Corn is a staple food in many countries. To enhance its yield and accessibility, breeders performed selective breeding over the years to turn maize from its wild ancestor, teosinte, into its modern variety (Zea mays). However, we may have lost some important nutritional and health-beneficial bioactive compounds during the process. Therefore, our study aims to evaluate the potential changes in the gastrointestinal (GI) digestibility and quality of proteins among maize lines during domestication. 26 lines of modern maize (MM) and 25 lines each of teosinte and landraces were chosen. Semi-targeted GC-MS was performed on maize lines for primary metabolite-profiling followed by simulated GI digestions. Post-digestion, soluble protein, and peptide content were estimated by Lowry’s protein quantification protocol and Pierce Quantitative Fluorescent Peptide Assay kit, respectively.

The GC-MS analysis detected around 46 metabolites from a pool of 76 maize lines. MM and landraces exhibited high levels of glutamic acid, asparagine, and tyrosine. Levels of quinic acid, mucic acid, caffeic acid, stearic acid, and chlorogenic acid were high in teosinte. While 12 lines of teosinte had high peptide levels ( > 400 µg/mg), their peptide level varied from 516.90 µg/mg to 339.34 µg/mg. The peptide level of the landraces ranged uniformly from 425 to 304.015 µg/mg. The peptide level of the MM lines reached maximum at 502.54 µg/mg and minimum at 289.68 µg/mg. A higher peptide content can be correlated to better digestibility, but it is subject to further studies. The protein content of the digested teosinte lines and landraces ranged uniformly from 203.59 to 297.83 µg/mg and 140.14 to 205.91 µg/mg, respectively. Protein content in MM lines ranged from 189.26 µg/mg to 289.15 µg/mg. These data show a comparatively higher protein and peptide content in teosinte lines which might be lost. This work will promote maize as an innovative plant protein.