Effect of Sun-Drying-Induced Vitamin D Enhancement in Oyster Mushroom and Its Retention during Boiling in an Instant Soup Mix

Abstract

Vitamin D insufficiency remains a public health concern, particularly among populations with limited dietary sources of the vitamin. This study evaluated vitamin D enhancement in solar-dried oyster mushroom (Pleurotus ostreatus) powder and its retention after incorporation into an instant soup mix and boiling. Fresh oyster mushrooms were cleaned, cut into approximately 0.5 × 4 cm pieces, and dried in a solar dryer at 45–55 °C for 3 h. The dried material was ground into powder and used with solar-dried mushroom pieces in an instant soup formulation. For preparation, 20 g of the soup mix was reconstituted with 180 mL of water and boiled at 100 °C. Vitamin D was determined by high-performance liquid chromatography using an ergocalciferol standard and UV detection at 264 nm. The untreated mushroom powder contained 7.73 µg/g vitamin D, whereas the solar-dried powder contained 45.21 µg/g, representing an absolute increase of 37.48 µg/g and an approximately 5.85-fold enhancement. The boiled mushroom soup mix contained 3.73 µg/g vitamin D, with a reported retention of 82.52%. Corresponding vitamin D peaks were observed in chromatograms of the solar-dried powder and boiled soup mix. These findings indicate that solar drying enhanced the measured vitamin D content of oyster mushroom powder and that vitamin D remained detectable after boiling. Replicated analyses, statistical evaluation, and complete reporting of retention-calculation inputs are needed to confirm the findings.