Oxidation of Polyphenols in Phytate-Reduced High-Tannin Cereals:  Effect on Different Phenolic Groups and on in Vitro Accessible Iron

Abstract

After reduction of phytate with phytase, water slurries of two high-tannin cereal flours were incubated with polyphenol oxidase (mushroom tyrosinase), and the effects on different phenolic groups and on in vitro accessible iron were studied. Enzyme incubation was also performed after cooking, soaking, and germination of the cereals. Phytase incubation significantly decreased the phytate content, and incubation with polyphenol oxidase had a reducing effect on the total phenol content, as well as on the amount of catechol and resorcinol groups. The in vitro accessible iron increased when the cereals were incubated with phytase and polyphenol oxidase, and the highest accessibility of iron was obtained when the germinated samples were incubated. The results from this study imply that oxidation of polyphenols in high-tannin cereals, after reduction of phytate, may be used to increase the bioavailability of iron in foods prepared from these cereals.

Potential contribution of African green leafy vegetables and maize porridge composite meals to iron and zinc nutrition

“…Contamination iron, as was probably present in the pumpkin leaves, has been found to not be bioaccessible [29]. The amaranth-spiderplant, fortified maize porridge meal could provide the most bioaccessible iron, compared to all the other dishes and meals.…”

Health benefits of finger millet (Eleusine coracana L.) polyphenols and dietary fiber: a review

“…Total phenolics reduced during cooking of millet flours probably due to thermal degradation and also due to the changes in chemical reactivity or formation of insoluble complexes with food components such as proteins. Enzymatic treatments of untreated, cooked, soaked, germinated millet with phytase and tyrosinase for 24 h resulted in 20, 40, 26, 32% decrease of total polyphenols content and may be due to condensation of phenolic compounds (Matuschek et al 2001). Extrusion cooking is one of the most efficient and versatile food processing technologies that can be used to produce pre-cooked and dehydrated foods.…”

Effect of phytate and iron-binding phenolics on the content and availability of iron and zinc in micronutrients fortified cereal flours

“…The amounts of total phenolic compounds were determined by the Prussian blue method using acidified methanol (1 % HCl) as extraction solvent [4,5,18]. The ironbinding polyphenolic (catechols and galloyls) groups were determined by the modified ferric ammonium sulphate (FAS), using 50 % dimethyl-formamide in acetate buffer (pH 4.4) as extraction solvent [4,5,19].…”

“…[4,5,6,7]. Bioavailability of most fortificant iron (like ferrous fumarate) has been shown to be affected adversely by the inhibitory compounds of phytate and polyphenols [3].…”

“…However, they all contain appreciable high amounts of phytate compounds [4,5]. The iron content and its in vitro iron availability for absorption in different cereal flour fortified with micronutrients (under rural settings in Tanzania), have not being studied.…”