Elisabeth Wisker

Digestibility of energy, protein, fat and non-starch polysaccharides in mixed diets: Comparative studies between man and the rat

The apparent digestibility of energy, protein, fat and non-starch polysaccharides (NSP) of low and high dietary fibre (DF) mixed diets were studied in three series of experiments with man and the rat. Low DF diets were used as control diets in each experimental series and the DF level was increased by adding fruits and vegetables (Study 1), citrus fibre concentrate (Study 2) and insoluble barley fibre (Study 3). In Study 3 the high DF diet was fed at two protein levels. There was in most cases good agreement between the digestibility of energy between man and the rat, with the digestibility of energy of the low DF control diets of 0.941-0.950 in man compared with 0.933-0.952 in the rat and of the high DF diets of 0.897-0.931 in man and 0.865-0.920 in the rat. The biggest difference in digestible energy between the two species was found for the diet enriched with fruits and vegetables (0.032 absolute units) and citrus fibre concentrate (0.025 absolute units). Apparent digestibility of protein was slightly lower in man than in the rat for all diets in Studies 1 and 2. In Study 3, however, apparent digestibility of protein was consistently lower in man than in the rat with differences in absolute digestibilities between the two species varying from 0.023 (high DF/high protein) to 0.071 (high DF/low protein). The digestibility of fat was the same in man and in the rat in all but the high DF diet of Study 2. The rat appears to have a lower capacity to digest fibre polysaccharides than man and the digestibility of NSP was consistently lower in the rat than in man. The biggest difference between the two species was found for the diets in Study 2 where the digestibility of NSP in man was measured to be 0.774-0.885 compared with only 0.501-0.517 in the rat. For the other diets the differences in NSP digestibility were 0.077-0.137 absolute units. In spite of some differences between man and the rat in their ability to digest nutrients the various diets are ranked in the same order by the two species.

Fermentation of non-starch polysaccharides in mixed diets and single fibre sources: comparative studies in human subjects and in vitro.

The present study investigated whether the extent of fermentation of NSP in human subjects could be predicted by an in vitro batch system. Fibre sources studied were five mixed diets containing different amounts and types of fibre and three single fibre sources (citrus fibre concentrate, coarse and fine wholemeal rye bread). Fermentation in human subjects was determined in balance experiments in women who were also donors of the faecal inocula. In vitro fermentations were performed with fibre residues prepared from duplicates of the fibre-containing foods consumed during the balance trials. Fermentation of total NSP in vivo was between 65.8 and 88.6% for the mixed diets and 54.4, 58.0 and 96.9% for the coarse and fine wholemeal rye breads and the citrus fibre concentrate respectively. For the mixed diets and the citrus fibre concentrate, mean differences between the extent of NSP degradation after 24 h in vitro incubation and that in vivo were between -0.7 and 5.0%. Differences were significant for one diet (P < 0.05). For the wholemeal rye breads, the fermentation in vitro exceeded that in vivo significantly, but the magnitude of the difference in each case was small and without physiological importance. Particle size of breads had no influence on the extent of NSP degradation. These results indicate that the in vitro batch system used could provide quantitative data on the fermentation in vivo of NSP in mixed diets and some single fibre sources. An in vitro incubation time of 24 h was sufficient to mimic the NSP degradation in vivo.

Short-chain fatty acids produced in vitro from fibre residues obtained from mixed diets containing different breads and in human faeces during the ingestion of the diets.

It was studied whether the type of bread (i.e. a low-fibre wheat-rye mixed bread and coarse or fine wholemeal rye bread) either as part of a diet or alone, had an influence on the short-chain fatty acids (SCFA) produced during in vitro fermentation. Fermentation substrates were dietary fibre residues obtained from diets and breads. In addition, it was investigated whether the faecal SCFA pattern in the inoculum donors, who ingested the experimental diets, could be predicted by in vitro fermentation. Yields of SCFA in vitro were 0.51-0.62 g/g fermented polysaccharide. In vitro, the molar ratios of butyrate were higher for the two high-fibre diets containing coarse or fine wholemeal bread than for the low fibre diet containing wheat-rye mixed bread; the difference was significant for the coarse (P < 0.01), but not for the fine bread diet (P = 0.0678). The coarse wholemeal bread alone produced a higher molar ratio of butyrate than the fine wholemeal bread (P < 0.05) and the wheat-rye mixed bread (P < 0.01). Ingestion by the inoculum donors of the diets containing wholemeal bread led to higher faecal butyrate ratios (molar ratios: coarse bread diet 19.6, fine bread diet 17.7) compared with the wheat-rye mixed bread-containing diet (14.9), but the differences between the diets were not significant. For the diets investigated, there were no significant differences between faecal and in vitro SCFA patterns.

FIBRE-MEDIATED PHYSIOLOGICAL EFFECTS OF RAW AND PROCESSED CARROTS IN HUMANS

Fibre-mediated physiological effects of raw and processed carrots were investigated in twenty-four young women under strict dietary control in two randomized crossover studies. For 3 weeks between 405 and 688 g of either raw frozen, blanched or canned carrots (first study), or raw or raw frozen carrots (second study) were consumed in addition to a low-fibre basal diet. Carrots provided 15 g dietary fibre (DF)/d. Total DF intake was 16.0 to 19.0 g (control periods) and 31 to 34 g (experimental periods). Faecal bulking effects of raw and processed carrots were similar (between 2.4 and 3.7 g additional stool/g carrot fibre in the diet). Faecal excretion of dry matter, fibre, and protein also increased significantly during carrot consumption. Fermentability of carrot fibre constituents was high (91-94%) and independent of processing, in spite of differences in the distribution of soluble and insoluble fibre and in the texture of raw and processed carrots. There was no effect of either type of carrot on serum total and high-density-lipoprotein-cholesterol or on faecal bile acid excretion.

Particle size of whole meal rye bread does not affect the digestibility of macro-nutrients and non-starch polysaccharides and the energy value of dietary fibre in humans

The effect of particle size of whole meal rye bread on the apparent digestibility of macro-nutrients, non-starch polysaccharides (NSP) and energy, the energy value of rye NSP and on faecal weight was studied in balance experiments in seven young women. The whole meal breads were prepared from one single batch of rye milled to two different particle sizes (coarse bread: 50% of particles > 2 mm, 90% > 1 mm; fine bread: 86% of particles < 0.5 mm, 58% < 0.2 mm). Two diets containing either coarse (350 g day-1) or fine (377 g day-1) whole meal bread and a low fibre control diet were consumed for 3 weeks each in a 3 X 3 cross-over design. Relative to the low fibre control diet, digestibility of protein, NSP and energy was significantly lower for the diets containing the whole meal breads. Digestibility of fat was the same for all diets. Partial digestible energy value for each g of NSP from coarse and fine whole meal rye bread was calculated to be -3 +/- 7 and 1 +/- 5 kJ, respectively. There were no differences between coarse and fine whole meal rye bread in the effects on the parameters measured with the exception on faecal wet weight, which was higher for the coarse bread diet.

Contribution of barley fiber to the metabolizable energy of human diets

Abstract The metabolizable energy (ME) of a low fiber diet and of a high fiber diet supplemented with 15 g dietary fiber (DF) from a barley fiber concentrate was determined in balance experiments in 12 young women. The ME of the diets was also calculated by energy assessment procedures. Total daily intake of DF was 22.5 g with the low fiber diet and 38.6 g with the high fiber diet. The addition of barley fiber decreased the digestibility of dietary energy (95.0 vs. 92.7 %) and NSP (83.2 vs. 65.4 %) significantly, whereas the digestibility of nitrogen and fat was not affected. The partial digestible energy value of the barley fiber was calculated to be 3 kJ (0.8 kcal)/g. This value is above the energy value calculated for whole grain fiber, but lower than that for fiber from mixed diets. The ME of the experimental diets could best be estimated by the equations of Southgate and of Livesey and by a modification of the British energy assessment procedure.

Effects of a fiber concentrate from citrus fruits in humans

Abstract Ten female subjects consumed a fiber concentrate made from citrus fruits under strict dietary control in a randomized cross over study comprising 2 experimental periods each of 4 wk duration. The citrus fiber concentrate contained 68.6 g total dietary fiber per 100 g, half of which was soluble. The fiber preparation was incorporated into various fiber free or low fiber foods in an amount providing 24 g total dietary fiber daily. The control diet contained these foods but without added fiber. Total dietary fiber intake was 21.2 and 45.1 g/d during the control and the high fiber diet periods, respectively. When the control diet was fed, mean total serum cholesterol levels remained stable, whereas high density lipoprotein (HDL)-cholesterol was reduced by 6.5% after 4 wk. When the citrus fiber was consumed for 4 wk, both serum total and HDL-cholesterol levels were decreased significantly by 10.6 and 14.5%, respectively. The addition of citrus fiber to the diet increased fecal wet and dry weight by 1.5 and 0.2 g, respectively, per gram of additional fiber. Fecal excretions of both energy and nitrogen were increased due to the intake of citrus fiber, whereas fecal fat was not affected. The additional fiber source was fermented completely. The partial digestible energy value of the citrus fiber was calculated to be 12 kJ (2.9 kcal)/g.

Einbeziehung der Ballaststoffe in die Berechnung des Brennwertes von Lebensmitteln

The metabolizable energy (ME) of 16 diets containing various amounts and sources of dietary fibre was calculated by different energy assessment procedures and determined experimentally in balance studies in humans. ME was calculated by the German procedure (§35 LMBG; 4/9/4) and by the British procedure (4/9/3.75). In addition, both calculation procedures were modified to take into account the energy value of dietary fibre. Dietary fibre was multiplied by an energy conversion factor of 1 or 2 kcal/g, respectively. The best agreement between measured and calculated ME was obtained when a conversion factor of 1 kcal/g fibre (German procedure) or of 2 kcal/g (British procedure) was used.ZusammenfassungDer nach verschiedenen Verfahren berechnete physiologische Brennwert von 16 Kostformen mit unterschiedlichen Ballaststoffgehalten und -trägern wurde mit den Werten verglichen, die in Bilanzuntersuchungen am Menschen experimentell bestimmt wurden. Der Brennwert wurde nach dem deutschen Verfahren nach § 35 LMBG (4/9/4) und nach dem britischen Verfahren (4/9/3.75) berechnet. Beide Methoden wurden zusätzlich modifiziert, um die Energie der Ballaststoffe zu berücksichtigen. Ballaststoffe wurden mit 1 bzw. 2 kcal/g berechnet. Die beste Übereinstimmung von berechnetem und experimentell bestimmtem physiologischen Brennwert wurde erreicht, wenn Ballaststoffe mit 1 kcal/g (deutsches Verfahren) bzw. mit 2 kcal/g (britisches Verfahren) bewertet wurden.The metabolizable energy (ME) of 16 diets containing various amounts and sources of dietary fibre was calculated by different energy assessment procedures and determined experimentally in balance studies in humans. ME was calculated by the German procedure (section 35 LMBG; 4/9/4) and by the British procedure (4/9/3.75). In addition, both calculation procedures were modified to take into account the energy value of dietary fibre. Dietary fibre was multiplied by an energy conversion factor of 1 or 2 kcal/g, respectively. The best agreement between measured and calculated ME was obtained when a conversion factor of 1 kcal/g fibre (German procedure) or of 2 kcal/g (British procedure) was used.

Caloric value and content of dietary fiber of cereals, flours, and breads

A new method for the determination of the caloric values of foods is proposed. To date it had been suggested that with an increase in the dietary fiber content of foods the intestinal absorption of proteins and fats is reduced. This has to be revised in the light of recent experimental results. The new method leads to higher energy values for fats and proteins whereas for carbohydrates lower figures are obtained. This leads to considerable deviation in the energy content of foods from the values in present tables, especially for foods rich in dietary fiber.

[A method for the determination of tartrazine in candies and pudding mixes (author's transl)].

The use of food additives is viewed increasingly from a critical point of view. In some countries, stronger regulations with limitations for the use of synthetic coal-tar dyes are planned or exist already. For that reason, a quantitative method for the determination of tartrazine (E 102) is needed for supervision of food quality. A method is described using as its steps extraction of the dyestuffs from the samples, chromatography on silicagel plates and automatically recorded densitometry. In candies amounts of up to 285 mg tartrazine/kg and in pudding mixes up to 1223 mg tartrazine/kg were found.SummaryThe use of food additives is viewed increasingly from a critical point of view. In some countries, stronger regulations with limitations for the use of synthetic coal-tar dyes are planned or exist already. For that reason, a quantitative method for the determination of tartrazine (E 102) is needed for supervision of food quality. A method is described using as its steps extraction of the dyestuffs from the samples, chromatography on silicagel plates and automatically recorded densitometry. In candies amounts of up to 285 mg tartrazine/kg and in pudding mixes up to 1223 mg tartrazine/kg were found.ZusammenfassungKritische Ansichten zur Verwendung von Lebensmittelzusätzen werden zunehmend vertreten, sie betreffen auch das Gebiet der Lebensmittelfarbstoffe. Einige Länder sind dazu übergegangen, Höchstmengen für den Gebrauch synthetischer Lebensmittelfarbstoffe festzusetzen. Für das hier untersuchte Tartrazin besteht in diesen Ländern die Notwendigkeit des quantitativen Nachweises in der Lebensmittelüberwachung. Eine hierfür geeignete Routine-Methode mit einer Extraktion der Farbstoffe aus dem Probenmaterial, einer dünnschichtchromatographischen Trennung auf Kieselgel und der densitometrischen Auswertung wird beschrieben. Die Anwendbarkeit und Zuverlässigkeit des Verfahrens wird geprüft. In den Untersuchungen werden bei Süßwaren bis zu 285 mg Tartrazin/kg, bei Puddingpulvern bis zu 1223 mg Tartrazin/kg (das entspricht etwa 60 mg/kg Pudding) nachgewiesen.