Nils Georg Asp

Food properties affecting the digestion and absorption of carbohydrates

Carbohydrate foods differ considerably in their effects on postprandial glucose and insulin responses. Qualitative differences among starchy foods are particularly intriguing because of the dominance of starch in human diets. This paper focuses on food properties in cereal (eg, pasta, bread, Arepas, and porridge) and legume products (eg, red kidney beans and lentils) that affect metabolic responses to starch. Studies in healthy subjects have found that postprandial blood glucose and insulin responses are greatly affected by food structure. Any process that disrupts the physical or botanical structure of food ingredients will increase the plasma glucose and insulin responses. The glycemic responses to bread products were reduced by the use of ingredients with an intact botanical or physical structure or a high amylose content or by enrichment with viscous dietary fiber. However, the important of a moderate increase in the amylose-amylopectin ratio and the naturally occurring levels of viscous cereal fiber is less clear. The rate of starch digestion in vitro was shown to be a key determinant of metabolic responses to most products. Assuming the sample preparation mimics chewing, in vitro enzymic procedures can be used to facilitate ranking. One such procedure, based on chewed rather than artificially disintegrated products, was recently developed and correlates well with glycemic and insulinemic indices for several starchy foods.

Oligosaccharide formation during hydrolysis of lactose with Saccharomyces lactis lactase (MaxilactR): Part 1—Quantitative aspects

Abstract The formation of oligosaccharides during hydrolysis of lactose with Saccharomyces lactis lactase (MaxilactR) was followed at different lactose concentrations. The amount of oligosaccharides formed increased with the lactose concentration and had its maximum value (5–13% by weight of total sugar) when about 65–75% of the sugar was hydrolysed to monosaccharides. The oligosaccharides were hydrolysed on prolonged incubation with active enzyme.

Protein nutritional value of extrusion-cooked wheat flours

Abstract The effect of extrusion cooking on the protein nutritional value of wheat flour and whole-grain wheat flour was studied. Amino acid analysis showed lysine retention between 63 and 100%. The retention was positively affected by an increase in feed rate, and negatively by an increase in screw speed. The prominent lysine damage under severe conditions was probably due to formation of reducing carbohydrates through hydrolysis of starch. The loss of other amino acids was small. The BV of extruded wheat flours was significantly reduced in the products showing the most prominent lysine loss. However, no effect was seen in TD. In contrast, a decrease in BV of extruded whole-grain flour was accompanied by a significant reduction in TD. Extrusion cooking of wheat starch did not affect the nitrogen balance in rats given casein/starch diets containing raw or extruded starch.

Oligosaccharide formation during hydrolysis of lactose with Saccharomyces lactis lactase (Maxilact®): Part 2—Oligosaccharide structures☆

Abstract The oligosaccharides produced during the hydrolysis of lactose with Saccharomyces lactis lactase were isolated and structurally analysed. Six oligosaccharides with two to four monosaccharide units were studied. All were linear and had one or two galactosyl residues linked β-(1 → 6)- to glucose, galactose or lactose. Thus, in addition to lactose hydrolysing activity, the enzyme has transglycosylation activity with high specificity for formation of β-(1 → 6)- galactosidic linkages.

Oligosaccharide formation during hydrolysis of lactose with Saccharo myces lactis lactase (Maxilact®)—Part 3: Digestibility by human intestinal enzymes in vitro☆

Abstract Practically all the oligosaccharides produced during enzymatic hydrolysis of lactose with Saccharomyces lactis lactase are formed by attachment of galactosyl residues in β-(1 → 6) linkages. The activity of human small-intestinal β-galactosidase on these substrates was less than 10% of the activity on lactose which has its galactosyl moiety in a β-(1 → 4) bond. Therefore, ingested disaccharides will pass undigested through the small intestine into the large bowel, where bacterial degradation takes place. This explains the gastrointestinal discomfort after oligosaccharide ingestion described in another paper (unpublished).

Nutritional value of lactose-hydrolysed milk: protein quality after some industrial processes

The nutritional protein quality of lactose-hydrolysed milk after some industrial processes was studied with N balance experiments on growing rats.Ultra-high-temperature sterilization and evaporation at 25 °C did not influence the nutritional value significantly, whereas spray-drying under conditions usually used for ordinary milk gave a considerable reduction in protein quality. This was caused mainly or entirely by loss of biologically availabe lysine.

Digestibility of collagenous fermented sausage in man.

The digestibility of the protein of a fermented collagenous sausage was studied in three patients with ileostomies with small bowel resections. The patients were given four ordinary meals each day with a total protein content of about 64g, half of which was derived from collagen. Pigskins from 6-month old scalded pigs were used as the collagen source. A fermented sausage, based on meat, was used as a reference and the patients with ileostomies served as their own controls. Urine was collected from two patients. The true nitrogen digestibilities were found to be 71-79 % for the collagenous diets and 69-85 % for the reference diets. Hydroxyproline digestibilities (apparent and true) for the collagenous diet periods were similar: 70-82 %. This indicated that collagen was digested to the same extent as other proteins. Amino acid patterns of ileal excreta distinctly differed for each of the two periods, further confirming that all the protein was not absorbed. Elevated excretion of hydroxyproline in the urine after ingestion of the collagenous sausage was found, mainly as peptide bound hydroxyproline, but accounted for about only 2% of the ingested hydroxyproline. It was concluded that collagenous fermented sausage is as digestible as a reference sausage based on meat even without prior heat treatment.