Using germ-free rats and previously germ-free rats inoculated with a complex human flora (heteroxenic rats), the digestibility of new glucooligosaccharides (GOS) and the effect of the digestive flora on their fermentation were studied. The GOS were synthesized using a glucosyltransferase reaction and were composed of a mixture of mono-to heptasaccharides (degree of polymerisation (DP) from 1 to 7), with c(-1,6 and w1,2 linkages. In germ-free rats, two diets containing GOS (20 g kg-' diet and 40 g kg-' diet) were compared to a control diet containing sucrose. The extent of GOS digestion was about 20 % and the major component, DP 5, was almost fully resistant to the action of endogenous enzymes. In heteroxenic rats, only GOS (20 g kg-' diet) was compared to the control diet. Gaseous H, and CH, excretions measured in a respiratory chamber significantly increased by GOS fermentation (1.8 and 2.9 times, respectively, P < 0.001). As compared to the control group, there were no modifications of the pH, short-chain fatty acids (SCFA), and lactic acid concentrations in the caecum of rats fed with the GOS diet, but there were changes of the SCFA profile, ie butyric, isobutyric and isovaleric acid proportions significantly decreased (P < OOl), whereas the caproic acid proportion increased (P < 0.05). GOS appeared to be completely fermented. Changes in the gaseous excretion and in the SCFA profile suggest that the intake of a low amount of this new synthetised GOS led to some decrease in the proteolytic activity and in an enhancement of the glycolytic fermentation.Key words : glucooligosaccharides, bioavailability, fermentation, gnotobiotic rats. INTRODUCTIONoligosaccharides (like transgalactooligosaccharides) are totally indigestible in humans (Tanaka et a1 1988). With the aim of introducing non-dietary sweeteners inUsing an enzymic reaction catalysed by a glucosylthe human diet, synthetic oligosaccharides made of transferase from Leuconostoc mesenteroides which transfructose or galactose chains have been increasingly fers glucose molecules from sucrose (donor) onto maltose produced over the past 10 years. These oligosaccharides (acceptor) a new glucooligosaccharide (GOS) product have to be at least partially resistant to glycolytic was synthetised. This resulted in the release of fructose intestinal enzymes. It was shown in uitro and in uivo, that and in the synthesis of a mixture of GOS containing fructooligosaccharides (NeosugarB) are only partially approximately 18 % mono-, di-and trisaccharides, 18 % degraded by the endogenous glycosidases (Oku et a1 tetrasaccharides, 33 % pentasaccharides and 31 % hexa-1984; Tokunaga et a1 1989), whereas galactoand heptasaccharides (Paul et a1 1988). Glucosyltransferase is specifically characterised by the synthesis of

The effect of dietary protein on enzyme activity of pancreatic juice was studied in ten growing, castrated, Large White male pigs. Animals, fitted with permanent cannulas in the pancreatic duct and in the duodenum, were divided into two groups receiving either casein or rapeseed concentrate as a protein source. After a 15 d adaptation period to the experimental diet, the volume of pancreatic secretion was significantly higher, whereas the protein concentration was lower in the casein group compared with the rapeseed group. No statistical difference was observed in the daily protein output between groups. Total secreted activities of carboxypeptidase A (EC 3.4.17. l), and elastase (EC 3.4.21.36) were higher in the casein group during the nocturnal period, whereas total activities of trypsin (EC 3.4.21.4), chymotrypsin (EC3.4.21.1), carboxypeptidase B (EC3.4.17.2) and amylase (EC3.2.1.1) in pancreatic secretions during the post-prandial periods were increased by the ingestion of the rapeseed diet. It is concluded that the pancreatic enzyme secretion is sensitive to the nature of the protein ingested.

An in vitro enzymic method was used to study the kinetics of digestion of casein and rapeseed proteins. After a predigestion step with pepsin (EC 3 . 4 . 2 3 . I), the protein substrates were submitted to a 24 h hydrolysis either with pancreatin or pancreatic juices of pigs adapted either to casein or rapeseed diets and whose enzyme activities were different. After 3, 6 and 24 h of in vitro digestion, dialysates were collected and analysed for content of nitrogen, amino acids and low-molecular-weight peptides. For a long-term hydrolysis (24 h), overall digestibility of both substrates was not affected by the composition of pancreatic enzyme mixtures. However, at the beginning of hydrolysis a significant effect of pancreatic juices was observed, i.e. individual amino acid digestibility was generally higher when casein pancreatic juice was used for hydrolysis and their relative pattern of release was modified. For both substrates the proportion of amino acids released as low-molecular-weight peptides was not affected by the enzyme mixture used and made up about two-thirds of the total digested material. It is concluded that exocrine pancreatic adaptation to protein sources does not affect the total capacity of protein digestion. However, the changes in initial kinetics of release of amino acids are more dependent on the nature of the protein tested than on the composition of pancreatic enzyme mixtures.

Chez le porc adapté à la consommation d'un régime riche en son de blé (40 %), le volume de bile sécrété par 24 h est supérieur à celui enregistré chez l'animal qui ingère un régime sans son de blé (Payne, Juste et Corring, 1986). Les quantités de sels biliaires totaux sécrétés par 24 h ne sont, par contre, pas différentes (résultats non publiés). Afin de comprendre le ou les mécanismes impliqués dans la réponse biliaire, nous avons étudié l'évolution de la sécrétion biliaire du porc dès l'apparition de son de blé dans son alimentation. Parallèlement, le taux plasmatique de quelques peptides de régulation des sécrétions digestives a été déterminé.

Ten groups of 5 calves were used to study the changes of gastric (chymosin, pepsin, lysozyme), pancreatic (trypsin, chymotrypsin, elastase, carboxypeptidases A and B, lipase, colipase, phospholipase A2, amylase, ribonuclease) and intestinal (aminopeptidases A and N, alkaline phosphatase, lactase, maltase, isomaltase, sucrase) enzymes. The calves of one group were sacrificed at birth, whilst the