Vitamin D is a pro-hormone essential for bone health and calcium homeostasis( Reference Holick 1 ). Low levels of vitamin D impair calcium and phosphorus absorption, leading to poor mineralization of the skeleton. Vitamin D deficiency has become a major public health concern in the UK( Reference Mithal, Wahl and Bonjour 2 , Reference Lanham-New, Buttriss and Miles 3 ). Since not many food sources of vitamin D exist, it has been suggested that one strategy to improve vitamin D status is through the fortification of foods( Reference Itkonen, Skaffari and Saaristo 4 ). Mushrooms produce vitamin D2 when exposed to sunlight, and therefore may be an easy and inexpensive approach to fortifying food products( Reference Phillips, Ruggio and Horst 5 ), particularly for vegetarians. The aims of this study were to 1) develop a bread rich in vitamin D2 using sunlight exposed mushrooms, 2) to evaluate the effect of the duration of sunlight exposure on vitamin D2 content in 3 types of bread and 3) to analyse the acceptance of the product by the public.
Three varieties of two species of mushroom were used (Lentinula edodes and Agaricus bisporus). They were irradiated for 3 durations of exposure (30 minutes, 60 minutes and 90 minutes) and used to produce wholemeal breads with the same recipe (100 g mushrooms in each bread). Loaves of bread without mushrooms and with non-irradiated mushrooms were used as controls. Samples of 200 g of each type of bread were freeze-dried and sent to Campden BRI laboratories for vitamin D2 analysis. The sensory analysis was done in 51 participants and statistically analysed by SPSS.
Bread made with unirradiated mushrooms contained levels of vitamin D2 that were below the level of quantification (0·13 µg/100 g bread). Each type of mushroom showed an increased content of vitamin D2 which related to the duration of solar irradiation. Chestnut and Shitake mushrooms showed similar levels of increase of vitamin D2 levels with maximum levels at 90 mins (2·67 and 2·83 µg/100 g bread respectively). Highest levels of vitamin D were apparent in bread containing button mushrooms irradiated for 90 mins (5·19 µg/100 g bread).
The sensory analysis revealed that the breads made with chestnut and shitake mushrooms were preferred. In conclusion bread with mushrooms that have been irradiated with natural sunlight may offer a useful way to increase vitamin D2 in the diet.
