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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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| 3. |
- Livesey, G, et al.
(författare)
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Determination of digestible energy values and fermentabilities of dietary fibre supplements : a European interlaboratory study in vivo
- 1995
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Ingår i: British Journal of Nutrition. - 0007-1145. ; 74:3, s. 289-302
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Tidskriftsartikel (refereegranskat)abstract
- The performance of methods to determine energy conversion factors for dietary fibre (DF) supplements and fermentability (D) values of their non-starch polysaccharides (NSP) was investigated. Heats of combustion, digestible energy (DE) and D values were determined on five DF supplements in five European laboratories on five separate occasions. In each instance the DF supplements were fed to juvenile male Wistar rats at two doses, 50 and 100 g/kg basal diet, for 3 weeks with food and faeces collected in the 3rd week. Among-laboratory variations in heats of combustion (delta Hc) were < 2%. DE values (kJ/g dry weight) at the upper and lower doses respectively were: 10.4 and 9.9 for a high-methoxyl apple pectin, 9.5 and 9.4 for a sugar-beet DF supplement, 12.2 and 12.7 for soyabean DF supplement, 3.8 and 4.0 for maize bran, and 0.3 and 0.3 for Solka-floc cellulose. Variations among laboratories, among occasions and among animals were < 1, < 2 and < 2.5 kJ/g respectively. The among-occasion: among-laboratory variance ratio for DE was 0.5, suggesting the method performed equally well in all laboratories. There was no evidence of learning of fatigue or fatigue in the performance of the method. D values were also independent of dose and at the high and lower doses were: pectin 0.92 and 0.95, sugar-beet NSP 0.68 and 0.68, soyabean NSP 0.86 and 0.88, maize bran 0.17 and 0.18, cellulose 0.07 and 0.06. Among-laboratory variance tended to increase with decreasing fermentability and ranged from 0.03 to 0.18. The DE and D data were not significantly different from a previously proposed relationship DE = 0.7 x delta Hc x D, where delta Hc is the heat of combustion of the supplement. We conclude that while the among-laboratory variation in the D of difficult-to-ferment NSP is too large for the reliable prediction of energy value the method for the direction determination of DE is both reproducible and repeatable, that DE is independent of dosage of DF supplement up to 100 g/kg diet, and that it is safe to discriminate between energy values with a precision of 3 kJ/g. The conversion of both DE and D to net metabolizable energy for the purpose of food labelling, tables and databases is described.
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