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- Matuschek, Erika, 1974, et al.
(författare)
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Oxidation of polyphenols in phytate-reduced high-tannin cereals: Effect on different phenolic groups and on in vitro accessible iron
- 2001
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Ingår i: Journal of Agricultural and Food Chemistry. ; 49:11, s. 5630-5638
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Tidskriftsartikel (refereegranskat)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.
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| 2. |
- Towo, Elifatio E, 1962
(författare)
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Phenolic content in cereals and legumes. Influence of processing and effect on in vitro availability
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Iron deficiency anaemia is highly prevalent in Tanzania, and one of the major causes is the low bioavailability of iron in the plant food staple diet. Cereals and legumes contain large amounts of compounds that inhibit iron absorption, e.g. phytate and phenolic compounds including phenolic groups such as galloyls (trihydroxyl) and catechols (ortho-dihydroxyl). Several processing methods are also known to reduce the amount of phenolic compounds, but little is known about their effect on specific phenolic groups. Dephytinization has been shown to increase the bioavailability of iron from several cereals, but this treatment alone is not sufficient to increase the bioavailability in high-tannin grains. This study was conducted to determine and characterize the amount of phenolic compounds in some cereals and legumes commonly consumed in Tanzania and to study the effect of traditional processing methods in combination with polyphenol oxidase on phenolic groups and on in vitro available iron.Total phenols, resorcinols and potential iron-binding phenolic groups (galloyls and catechols) were determined in the food grains using different colorimetric methods. Grains were subjected to community processing methods including dehulling, soaking, cooking, germination or fermentation. Phenolic compounds were oxidized by incubating phytate-reduced cereal slurries with polyphenol oxidase (PPO) or adding PPO during the fermentation processes. The in vitro available iron was measured as iron solubility at physiological conditions. The methods used for the determination of phenolic compounds were reproducible and the sum of different phenolic groups correlated to the amount of total phenols (r2 = 0.97; p
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| 4. |
- Towo, Elifatio, 1962, et al.
(författare)
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Fermentation and enzyme treatment of tannin sorghum gruels: Effects on phenolic compounds, phytate and Fermentation and enzyme treatment of tannin sorghum gruels: Effects on phenolic compounds, phytate and in vitro accessible iron
- 2006
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Ingår i: Food Chemistry. - : Elsevier BV. - 0308-8146 .- 1873-7072. ; 94:3, s. 369-376
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Tidskriftsartikel (refereegranskat)abstract
- The presence of polyphenols and phytate in cereal products has been. shown to interfere with the bioavailability of minerals such as iron. In the present study, we added enzymes (wheat phytase and mushroom polyphenol oxidase) during fermentation of tannin sorghum gruels prepared from flour with or without addition of 5% flour of germinated tannin-free sorghum grains (power flour), and investigated the effects on phenolic compounds, phytate and in vitro accessible iron. Assayable phenolic compounds were significantly reduced by fermentation, with high reductions observed in gruels with added enzymes. Fermentation of the gruels with addition of enzymes reduced (on average) total phenols by 57%, catechols by 59%, galloyls by 70% and resorcinols by 73%. The phytate content was significantly reduced by fermentation (39%), with an even greater effect after addition of power, flour, (72%). The largest reduction of phytate (88%) was, however, obtained after addition of phytase. The in vitro accessible iron was 1.0% in the sorghum flour and it increased after fermentation with power flour and/or with enzymes. The highest in vitro accessibility of iron (3.1%) was obtained when sorghum was fermented with addition of power flour and incubated with phytase and polyphenol oxidase after the fermentation process.
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