Unlocking the potential of selenium (Se) bio-fortification and optimal food processing of barely grains on the alleviation of Se-deficiency in highland diets

Insufficient selenium (Se) intake was a concern among populations residing in the Se-deficient regions of China, particularly in the Tibetan Plateau. Enhancing the Se content in highland barley through cultivation and minimizing Se loss during food processing are crucial strategies to mitigate Se deficiency in highland diets. In this study, foliar and soil Se fertilizers were applied at varying doses (25, 50, 100 g/ha) enhancing the nutritional value of highland barley. Through the utilization of synchrotron X-ray fluorescence microscopy, Se was primarily observed to accumulate from the aleurone layer to the inner endosperm, while calcium (Ca), iron (Fe) and zinc (Zn) exhibited distinct accumulation hot spots in the testa, aleurone layer and crease region, respectively. However, the pearling processing caused the loss of certain micronutrients. Following the removal of pearling fractions P6 (which accounted for 17-20 % loss of grain weight), the maximum losses observed were as follows: Se (24.10 %), Zn (37.4 %), Fe (25.13 %), Ca (34.27 %), P (31.67 %), and free phenolic (28.13 %). Among the various thermal processing methods tested (stir-frying, microwave, atmospheric steam and high-pressure steam), there was minimal impact on the total Se content, although a significant degradation of free phenolic content was observed across all grains. Despite these processing effects, the Se content in Se-fortified highland barley grain remained within human-recommended levels at post-critical food processing conditions, suggesting the potential of Se bio-fortified highland barley for addressing Se inadequacy in highland diet.