Quantification of phytochemicals in Midwest adapted colored corn varieties, formulation of natural red food colorants, and evaluation of their thermal and storage stabilities
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[EMBARGOED UNTIL 05/01/2026] Colored corn varieties have been widely acknowledged for their relatively higher phytochemical contents. In addition, most of these bioactive compounds are concentrated in corn pericarp, a processing industry waste stream, which can be selectively processed for their efficient recovery. Due to the diverse industrial applications of phytochemicals such as natural food colorants, active food ingredients and health supplements, colored corn varieties can supplement the lower economic value of conventional yellow dent corn in the US. Eighteen varieties from the 2022 season, and fifteen varieties from the 2023 season of the Missouri colored corn breeding and adaptation program were dry milled and analyzed for their phytochemical contents and antioxidant properties. The mean pericarp yield for the varieties from 2022 was higher at 7.96% (dry basis, db) compared to 4.65% (db) for the varieties from 2020-2021. Based on their higher polyphenolic contents, six varieties were identified and further analyzed. The highest concentrations of total anthocyanins (TAC), phenolics (TPC), condensed tannins (CT) and total flavonoids (TFC) detected were 28.8 g cyanidin-3-glucoside (C3G)/kg, 53.1 g gallic acid (GA)/kg, 155.7 g epicatechin (EE)/kg and 13.7 g catechin (CT)/kg of pericarp, respectively. To sum up, the varieties from the 2022 season showed greater pericarp yield, higher concentrations of phytochemicals, and greater antioxidant properties, demonstrating the successful progression of the adaptation program. Whereas purple corn or Maiz morado was widely utilized as a parent during the 2020-2021 and 2022 seasons, several other colored corn varieties were explored during the 2023 season in quest of greater diversity. The mean pericarp yield at 6.15% (db) was higher than the varieties from 2020-2021 (4.65%, db) but less than those from 2022 (7.96%, db). Maximum concentrations of TAC, CT, TPC, and TFC in corn pericarp were 19.72 g C3G, 101.26 g EE, 44.32 g GAE and 8.29 g CE/kg of pericarp, respectively. Five phytochemical-rich varieties and a green and brown variety were selected for further analyses. Overall, the men CT, TAC, TFC and TPC concentrations for the five best varieties was 77.96 g EE, 12.41 g C3G, 4.32 g CE, and 27.80 g GAE/kg pericarp, respectively, which were lower than those from the previous breeding cycles. Maiz morado was identified to be the most important variety for further breeding efforts, while aiming for the highest phytochemical contents. This study marked another successful milestone in the quest of developing Midwestern US-adapted colored corn varieties. Polyphenols from purple corn pericarp were extracted in an aqueous solution and spray-dried to produce microencapsulates using four carrier materials, namely, maltodextrin (MD), gum arabic (GA), methylcellulose (MC), and skim milk powder (SMP) at three concentrations (1, 2, and 3%, respectively). The encapsulates were evaluated for their polyphenolic contents using spectrophotometric techniques and HPLC analyses, and their antioxidant properties were evaluated. Comparative analysis of structural characteristics, particle size distribution, zeta potential, water solubility index, water absorption index, and water activities (aw) of the samples confirmed the successful formulation of encapsulates. The microencapsulates with 1% coating material retained polyphenolic compounds and exhibited noteworthy antioxidant properties. The samples encapsulated with GA or MD (1%) demonstrated superior physicochemical, color, and thermal properties. This work demonstrated successful formulation of shelf stable natural red colorant powders from purple corn pericarp. Three anthocyanin-rich colorant powders were prepared using spray- and freeze-drying processes and exposed to elevated temperatures (50, 70, 90 and 121 °C). Relative thermal stability of C3G at 121 °C with corresponding t (1/2) values > 2 hr for all the three samples implied that purple corn pericarp anthocyanins can be effectively used as natural red food colorants in various food matrices, with high-temperature, short-time (HTST) treatments being the best options. Storage stabilities of powders were evaluated in a model beverage system at different temperatures, pH levels, and ascorbic acid concentrations over a period of seven weeks. Kinetic degradation analyses for storage stability demonstrated that these colorants were very stable against various environmental stressors. Overall, the purple corn anthocyanins demonstrated superior thermal and storage stabilities and can be effectively utilized as natural red food colorants in different matrices. Their wider adoption can help the US corn farmers, processors, food industry, and increasingly health-conscious consumers alike.
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Ph. D.