Improvement of nutritional characteristics and other health benefits of processed maize food products

Butts-Wilmsmeyer, Carolyn J.

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Description

Title

Improvement of nutritional characteristics and other health benefits of processed maize food products

Author(s)

Butts-Wilmsmeyer, Carolyn J.

Issue Date

2016-07-07

Director of Research (if dissertation) or Advisor (if thesis)

Bohn, Martin

Doctoral Committee Chair(s)

Bohn, Martin

Committee Member(s)

• Kolb, Fred
• Juvik, Jack
• Lipka, Alex
• Mumm, Rita

Department of Study

Crop Sciences

Discipline

Crop Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Phytochemicals
• Nutrition
• Plant Breeding
• Maize

Abstract

Maize is one of the world's most important and abundant cereal crops. It also contains phytochemicals which are beneficial to human health. This presents an opportunity to breed for maize food products which possess high levels of these beneficial phytochemicals. However, maize grain is not consumed directly. Before consumption, the grain must be processed. Due to the physical, chemical, and thermal stresses encountered during processing, the fate of various phytochemicals is unknown. Similarly, it is unknown if all maize genotypes respond to processing stresses in the same manner or if some genotypes are more resistant to changes in the concentrations of beneficial phytochemicals than others. Should some maize genotypes exhibit an ability to resist changes in phytochemical content during processing, it may be possible to breed for healthier processed maize food products. However, if beneficial phytochemicals are lost during processing, then it may be more effective to breed for all-natural food additives which can be extracted from the whole grain and used to fortify processed food products. From a breeding perspective, variability must exist for a trait to be improved. Also, it is helpful if the germplasm evaluated is representative of that which is most likely to be processed into maize food products so that direct conclusions can be made. Twelve inbreds consisting of ten ex-PVPs and two public lines were selected for this study. These inbreds are genetically representative of the maize germplasm grown in the US Cornbelt and, consequently, maize which is used in the making of processed food products. These inbreds were crossed using a half-diallel design to create 66 F1 hybrids. The parental inbreds and their hybrids (N = 78 entries) were evaluated together and grown in a Resolvable Incomplete Block Design with three replications for three years. One pound (454 g) of grain was harvested from each plot and set aside for phytochemical analysis. Most beneficial phytochemicals were relatively easy to measure using wet-lab chemistry or Fourier Transform Infrared Spectroscopy (FTIR), but the insoluble-bound hydroxycinnamic acids were difficult to quantify using standard extraction protocols. Therefore, at the onset of the project, a high-throughput method for the extraction of insoluble-bound hydroxycinnamic acids was developed (Chapter 1). The overall concentration of the insoluble-bound and soluble hydroxycinnamic acids, tocopherols, unsaturated fatty acids, and protein were measured at the whole kernel level in all inbreds and a subset of the hybrids to determine which phytochemicals in which genotypic variability was present. Only the insoluble-bound hydroxycinnamic acids and soluble cinnamic acid showed considerable genotypic variability and high concentrations (Chapter 2). The hydroxycinnamic acids were selected as candidate phytochemicals for improvement, and both the insoluble-bound and soluble hydroxycinnamic acids were measured in subsequent portions of the project. All inbreds and a subset of the hybrids (N = 7) used in this study were then processed into ready-to-eat breakfast cereals using laboratory scale techniques. The processing stages at which the hydroxycinnamic acids significantly changed concentration were identified. The concentrations of all candidate phytochemicals were analyzed at each of these processing stages (Chapter 3). Most phytochemicals showed a large and significant change in concentration due to processing. Also, there was a significant interaction between the genotype and the processing stage that resulted in a change of rank among the genotypes tested. Therefore, it would be impossible to use the phytochemical concentration at the whole kernel level to predict the phytochemical concentration in the final processed food product. Next, the possibility of extracting hydroxycinnamic acids from maize and using the extracts as all-natural food additives was examined (Chapter 4). The insoluble-bound hydroxycinnamic acid content of all hybrids and inbreds used in this study was measured. Genetic variance components were calculated, and the broad- and narrow-sense heritabilities were estimated. Two particular insoluble-bound hydroxycinnamic acids, namely ferulic acid and p-coumaric acid, were identified as having both relatively high concentrations in maize and high heritabilities. As such, the overall finding of this study was that insoluble-bound ferulic acid and p-coumaric acid concentrations in maize grain could be improved through selection. Also, the most efficient method of increasing the concentration of beneficial phytochemicals in processed food products is through the use of all-natural food additives. Another consideration in regards to breeding is high-throughput phenotyping. In addition to the different wet-lab techniques that were optimized in this study, the potential of measuring ferulic acid content and p-coumaric acid content using NIR was examined (Chapter 5). Correlation coefficients among phytochemical traits and agronomic, ear, and cob traits were calculated to determine if indirect selection might be possible. NIR methods proved to be inaccurate, and the correlations between the beneficial phytochemicals and the agronomic, ear, and cob traits were not strong enough to build a reliable prediction model for indirect selection. Therefore, the phenotyping approach which will most likely be successful is high-throughput wet-lab chemistry to measure the overall concentration of ferulic acid and p-coumaric acid in maize. Furthermore, this phenotyping should be conducted at the whole kernel processing stage because the most feasible means of increasing the ferulic acid and p-coumaric acid content of maize food products is via the extraction of hydroxycinnamic acids from the whole kernel for later use as all-natural food additives.

Graduation Semester

2016-08

Type of Resource

text

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Copyright 2016 Carolyn Butts-Wilmsmeyer

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