High uptake of citrus essential oil-loaded zein particles into E. coli tuned by the wet-crosslinked folic acid

• Published in: Food hydrocolloids 2023-09, Vol.142, p.108856, Article 108856
• Main Authors: Yang, Feilong, Zhao, Chengying, Feng, Liping, Wang, Yanqi, Ma, Mengyu, Fogliano, Vincenzo, Zheng, Jinkai, Madadlou, Ashkan
• Format: Article
• Language: English
• Subjects: Biopolymer; Covalent bond; E. coli; Plant protein; Protein modification
• ISSN: 0268-005X
• DOI: 10.1016/j.foodhyd.2023.108856

Zein particles are increasingly used for encapsulation and delivery of hydrophobic bioactive. Conjugation of zein with multi-carboxylic acids by the alkali-catalysed and wet amidation process causes zein crosslinking and enables tuning the characteristics of zein particles. However, little is known about how the conjugation is associated with the crosslinking mode, i.e., intra and/or intermolecular crosslinks. In this study, folic acid (FoA) was conjugated with zein via the wet method, and citrus essential oil (CEO) was encapsulated within the constructed zein-FoA particles. Infra-red spectroscopy and nuclear magnetic resonance analysis indicated amide bond formation between zein and FoA showing that the content of primary amino groups in zein particles decreased due to conjugation. The mole fraction of FoA in the particles (χFoA) was measured as an index of conjugation extent and even though it did not exceed ∼0.1, conjugation influenced several characteristics of the particles. The contents of α-helix and β-turn structures decreased, and that of β-sheets increased with increasing χFoA. We hypothesized based on ζ-potential and hydrodynamic diameter results, as well as gel electrophoresis that conjugation with FoA caused formation of only intramolecular crosslinks at χFoA ≤ 0.035, but it additionally resulted in intermolecular crosslinks at χFoA ≥ 0.037. Conjugation with FoA at χFoA 0.091 resulted in an improvement of the zein particles biological performance. It caused an increase (∼30%) in the particle uptake by E. coli cells, as well as the magnitude of CEO delivery into the bacteria cells compared with non-conjugated particles. [Display omitted] •Folic acid was successfully conjugated with zein via a simple food-grade technique.•The crosslinking mode between folic acid and zein rely on the amount of folic acid.•Folic acid conjugation clearly increased β-sheets compositions in zein particles.•Folic acid conjugation improved the internalization of zein particles into E. coli.•Folic acid-conjugated zein particles achieved efficient CEO delivery into E. coli.