Impact of UV‑C Light Treatment on the Vitamin D Content and Quality of Bread

Abstract

Vitamin D deficiency is a global health concern linked to various chronic diseases. Although food fortification is a promising solution, its implementation remains limited by processing losses, matrix inconsistency, and clean-label trends. Certain foods, including mushrooms and yeast-containing bakery products, naturally contain provitamin D₂ (ergosterol), which can be photoconverted into vitamin D₂ by ultraviolet (UV) light. While UV-based vitamin D₂ enrichment has been extensively studied in mushrooms, its application in bread remains largely unexplored. This study investigated UV-C irradiation as a biofortification strategy for white and whole wheat bread, evaluating the effects of UV-C dose (0.50 and 2.00 kJ/m²) and dose rate (0.03 and 0.13 kJ/m²·min) on vitamin D₂ content and bread quality attributes. Optimized UV-C parameters enabled a novel strategy to increase vitamin D₂ content in bread without compromising the quality. UV-C treatments resulted in varying vitamin D₂ levels in bread, depending on the dose and dose rate, whereas control bread did not contain any detectable vitamin D₂. The highest vitamin D₂ content was obtained when the 2.00 kJ/m² dose was applied at 0.03 kJ/m²·min dose rate, although this treatment altered odor and taste. However, other treatments increased vitamin D₂ without compromising the quality. The optimal treatment of 2.00 kJ/m² dose at 0.13 kJ/m²·min dose rate achieved the best balance between vitamin D₂ enrichment and sensory acceptability. Under the optimal conditions, a 14 g serving of UV-C treated white bread and a 15.5 g serving of whole wheat bread provided 27 and 37% of the recommended dietary allowance (RDA) for vitamin D, respectively. Thus, UV-treated bread represents a valuable and practical source of plant-based vitamin D for consumers, particularly for vegetarians or vegans.

1

Flowchart of the experimental procedure.

2

Pore structures of the white (top) and whole wheat bread (bottom) samples.

3

Effect of UV-C treatment on the sensory properties of white (A) and whole wheat (B) bread samples. LD-LDR: low dose (0.5 kJ/m²) at low-dose rate (0.03 kJ/m²·min), LD-HDR: low dose (0.5 kJ/m²) at high-dose rate (0.13 kJ/m²·min), HD-LDR: high dose (2.0 kJ/m²) at low-dose rate (0.03 kJ/m²·min), HD-HDR: high dose (2.0 kJ/m²) at high-dose rate (0.13 kJ/m²·min).