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- Björck, I., et al.
(författare)
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Formation of enzyme resistant starch during autoclaving of wheat starch : Studies in vitro and in vivo
- 1987
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Ingår i: Journal of Cereal Science. - 0733-5210. ; 6:2, s. 159-172
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Tidskriftsartikel (refereegranskat)abstract
- The formation of in vitro resistant starch (RS) during autoclaving and freeze-drying of wheat starch suspension was evaluated. A substantial amount of starch, up to 8% (dry weight basis), was rendered resistant to amylases during heat-treatment unless solubilised in KOH, whereas freeze-drying had only marginal effects. Heat-treated wheat starch was incorporated into test diets to provide different levels of RS (0–5 %). The digestibility of starch was measured in vivo through balance experiments in normal rats and in rats treated with Nebacitin to suppress hind-gut fermentation. RS remained essentially undigested also in vivo. However, like certain types of dietary fibre, RS was readily metabolised (80–92 %) by the hind-gut microflora. Starch analysed with an enzymic method, in vitro accessible starch (AS), seemed to correspond to starch digestible in vivo. The in vivo digestibility of AS was close to 100 % whether Nebacitin was present or not. Energy utilisation decreased significantly with increasing level of RS in the diet. The biological value of dietary protein increased with increasing intake of RS in normal rats whereas no effect was noted in animals treated with Nebacitin. We conclude that RS formed during heat-treatment should be regarded as an easily fermentable dietary fibre component.
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| 2. |
- Björck, Inger, et al.
(författare)
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On the digestibility of starch in wheat bread - studies in vitro and in vivo
- 1986
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Ingår i: Journal of Cereal Science. - 0733-5210. ; 4:1, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- The digestibility of starch in white wheat bread was studied. Raw wheat starch and raw wheat flour were used as reference materials. The extent of digestion and absorption in vivo was evaluated through balance experiments in rats given test diets with and without addition of the antibiotic, Nebacitin, to reduce the fermentation in the hind-gut. As judged from a high faecal recovery of dietary fibre constituents in rats fed a wheat flour diet with Nebacitin, this drug significantly reduced the microbial activity in the hind-gut. Only minute amounts of starch could be detected in faeces of rats whether Nebacitin was present or not, indicating that pure wheat starch as well as starch in wheat bread and raw wheat flour was almost completely digested and absorbed in the rat small intestine. However, during baking, a fraction of the starch (0·6%–0·9%, dry basis) was rendered resistant to enzyme digestion in vitro unless solubilised in KOH. This modified starch fraction also remained undigested in vivo, but was readily metabolised by the hind-gut microorganisms, thus having physiological properties similar to those of dietary fibre. It is therefore recommended that resistant starch formed during baking (i.e. that rendered resistant to enzymic digestion as measured in vitro) should be regarded as dietary fibre rather than as dietary starch.
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| 3. |
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| 4. |
- Nyman, Margareta, et al.
(författare)
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Fermentation of dietary fibre in the intestinal tract of rats - a comparison of flours with different extraction rates from six cereals
- 1985
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Ingår i: Journal of Cereal Science. - 0733-5210. ; 3:3, s. 207-219
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Tidskriftsartikel (refereegranskat)abstract
- The fermentation of dietary fibre in wheat, rye, barley, sorghum, rice and maize was investigated in balance experiments with rats. Two different extraction rates, 100% and approximately 65%, were investigated for each cereal grain. In the case of maize, whole maize, and dehulled maize that had been ground and sieved so that it contained mainly endosperm, were investigated. Except for sorghum, dietary fibre in low-extraction flours was fermented to a greater extent than that in whole-grain flours. The sugar monomer compositions of the fibres at low and high extraction rates were similar for wheat and rye, but their susceptibilities to fermentation by bacterial enzymes were quite different. This indicates that a high proportion of soluble fibre and a low content of lignin improves the fermentability of the fibre. Further, barley, rice and sorghum fibre in refined flours, all of which consisted mainly of non-lignified glucans, were fermented more extensively when the proportion of soluble fibre was high. Addition of cellulose to diets containing wheat flour did not change the susceptibility of the wheat fibre to bacterial fermentation. Starch was demonstrated in faeces from rats fed wheat, sorghum and whole-grain rye flours. This starch represented 17–61 % of the total faecal glucan, but constituted less than 1% of the starch intake.
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