Standardization of Processing and UV-B Irradiation Parameters for Button Mushroom (Agaricus bisporus) Chips

Edible mushrooms are highly perishable due to their high moisture content¹, which favors microbial growth and rapid deterioration. However, they are also valuable sources of ergosterol, a precursor of vitamin D₂ that can be converted through UV-B irradiation⁴. Combining dehydration and UV-B irradiation offers an opportunity to develop shelf-stable mushroom products with enhanced nutritional potential. Therefore, this study aimed to standardize Paris mushroom chip processing, including slicing, dehydration, browning control, and UV-B exposure times. Organic Paris mushroom samples were purchased from a retail store in the town of Rio de Janeiro. Four cutting instruments were evaluated: conventional knife, egg slicer, meat slicer, and professional mandolin. The slices were arranged on trays with silicone mats, without overlap, and dehydrated at 60 °C for 6 hours. Moisture content and water activity were determined using infrared moisture analyzers (MOC63u - Shimadzu) and water activity meters (LabStart-aw - Novasina), respectively. To assess the effect of blanching, the slices were immersed in boiling water for 3 minutes, cooled in ice water for 3 minutes, and dried with paper towel before dehydration. Uniformity, crispness, and browning were evaluated qualitatively. Before dehydration, the sliced mushrooms were irradiated with UV-B using a CL-1000 Ultraviolet Crosslinker, and the exposure times required to achieve doses of 0.5, 1.0, 1.5, and 2.0 J/cm² were determined. The following results were obtained using this methodology. The instruments produced slices from 3.5 to 8.0 mm. The mandolin was selected for producing thinner (3.5 mm) and uniform slices that resulted in crispier chips. Initial moisture content and water activity were 92.3% and 0.94, respectively, which were reduced to 9.9% and 0.30 after 6 hours of dehydration, potentially contributing to reduced deterioration and microbiological growth². The slices subjected to blanching showed less apparent browning compared to non-blanched slices, suggesting inactivation of enzymes that promote enzymatic browning and oxidize bioactive compounds, such as polyphenoloxidase³, potentially contributing to the preservation of the antioxidant properties of the mushroom chips. The time for the Crosslinker to reach the dose that best optimizes vitamin D production, 1.5 J/cm², was 5 minutes and 30 seconds, significantly shorter than what Roberts and collaborators⁴ required (25 to 54.4 minutes, depending on irradiance). These preliminary results found that this standardized processing protocol enabled the production of uniform, crispy Paris mushroom chips with reduced moisture content, water activity, and apparent browning. Additionally, the UV crosslinker reduced the irradiation time required to achieve the target UV-B dose, compared with previous studies. Future steps include quantitative texture and color analyses, sensory evaluation, microbiological analyses, and targeted metabolomic analysis to assess vitamin D enrichment in UV-B-irradiated mushrooms.

Funding/Acknowledgments: UNIRIO, CAPES, FAPERJ, CNPq, LABAS/UFF, LABAL/UFF, LABBIO/UNIRIO, LABMUT/UERJ