School of Materials, University of Manchester, Manchester, M13 9PL, UK.
Norwich Medical School, University of East Anglia, Norwich, NR4 7UQ, UK.
Sci Rep. 2018 May 2;8(1):6865. doi: 10.1038/s41598-018-25130-3.
Pea seeds are widely consumed in their immature form, known as garden peas and petit pois, mostly after preservation by freezing or canning. Mature dry peas are rich in iron in the form of ferritin, but little is known about the content, form or bioavailability of iron in immature stages of seed development. Using specific antibodies and in-gel iron staining, we show that ferritin loaded with iron accumulated gradually during seed development. Immunolocalization and high-resolution secondary ion mass spectrometry (NanoSIMS) revealed that iron-loaded ferritin was located at the surface of starch-containing plastids. Standard cooking procedures destabilized monomeric ferritin and the iron-loaded form. Iron uptake studies using Caco-2 cells showed that the iron in microwaved immature peas was more bioavailable than in boiled mature peas, despite similar levels of soluble iron in the digestates. By manipulating the levels of phytic acid in the digestates we demonstrate that phytic acid is the main inhibitor of iron uptake from mature peas in vitro. Taken together, our data show that immature peas and mature dry peas contain similar levels of ferritin-iron, which is destabilized during cooking. However, iron from immature peas is more bioavailable because of lower phytic acid levels compared to mature peas.
豌豆种子在未成熟时被广泛食用，称为青豆和速冻豌豆，主要通过冷冻或罐装保存。成熟的干豌豆富含以铁蛋白形式存在的铁，但对于种子发育未成熟阶段铁的含量、形式和生物利用度知之甚少。使用特定的抗体和胶内铁染色，我们表明铁蛋白在种子发育过程中逐渐积累铁。免疫定位和高分辨率二次离子质谱（NanoSIMS）表明，含铁的铁蛋白位于含有淀粉的质体表面。标准烹饪程序会破坏单体铁蛋白和含铁形式。使用 Caco-2 细胞进行的铁吸收研究表明，与煮沸的成熟豌豆相比，微波处理的未成熟豌豆中的铁更具生物利用度，尽管消化物中可溶性铁的水平相似。通过操纵消化物中植酸的水平，我们证明植酸是体外从成熟豌豆中吸收铁的主要抑制剂。综上所述，我们的数据表明，未成熟的豌豆和成熟的干豌豆都含有相似水平的铁蛋白铁，而在烹饪过程中会被破坏。然而，由于与成熟豌豆相比，未成熟豌豆中的植酸水平较低，因此其铁的生物利用度更高。
