1: Br J Nutr 1995 Sep;74(3):289-302
Determination of digestible energy values and fermentabilities of dietary
fibre supplements: a European interlaboratory study in vivo.
Livesey G, Smith T, Eggum BO, Tetens IH, Nyman M, Roberfroid M, Delzenne
N, Schweizer TF, Decombaz J
Institute of Food Research, Norwich Laboratory, Norwich Research Park,
Colney.
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.
PMID: 7547845, UI: 96046390