The impact of steeping, germination and hydrothermal processing of wheat (Triticum aestivum L.) grains on phytate hydrolysis and the distribution, speciation and bio-accessibility of iron and zinc elements. (30th October 2018)

• Record Type: Journal Article
• Authors: Lemmens, Elien; De Brier, Niels; Spiers, Kathryn M.; Ryan, Chris; Garrevoet, Jan; Falkenberg, Gerald; Goos, Peter; Smolders, Erik; Delcour, Jan A.
• Is Part Of: Food chemistry. Volume 264(2018)
• Page Start: 367
• Page End: 376
• Publication Date: 2018-10-30
• Subjects: Wheat -- Phytase -- Phytate -- Steeping and germination -- Hydrothermal processing -- Minerals -- Bio-accessibility -- Chemical speciation; Food -- Analysis -- Periodicals; Food -- Composition -- Periodicals; 664
• DOI: 10.1016/j.foodchem.2018.04.125
• Languages: English
• ISSNs: 0308-8146

Abstract

Highlights: Germinating wheat at 15 °C for 120 h only leads to a 15% phytate breakdown. Processing germinated wheat at 50 °C, pH 3.8 and 24 h degrades 95% of phytate. Fe is oxidized and no longer bound to phytate after such processing. As a result, iron bio-accessibility forcefully increases from 8% to 34%. Abstract: Chelation of iron and zinc in wheat as phytates lowers their bio-accessibility. Steeping and germination (15 °C, 120 h) lowered phytate content from 0.96% to only 0.81% of initial dry matter. A multifactorial experiment in which (steeped/germinated) wheat was subjected to different time (2–24 h), temperature (20–80 °C) and pH (2.0–8.0) conditions showed that hydrothermal processing of germinated (15 °C, 120 h) wheat at 50 °C and pH 3.8 for 24 h reduced phytate content by 95%. X-ray absorption near-edge structure imaging showed that it indeed abolished chelation of iron to phytate. It also proved that iron was oxidized during steeping, germination and hydrothermal processing. It was further shown that zinc and iron bio-accessibility were respectively 3 and 5% in wheat and 27 and 37% in hydrothermally processed wheat. Thus, hydrothermal processing of (germinated) wheat paves the way for increasing elemental bio-accessibility in whole grain-based products.