Concentrated Carbohydrate Solutions Research Articles

Hydrolysis and transgalactosylation catalysed by β-galactosidase from brush border membrane vesicles isolated from pig small intestine: A study using lactulose and its mixtures with lactose or galactose as substrates.

Enzymatic transgalactosylation, in different concentrated carbohydrate solutions, was investigated using brush border membrane vesicles (BBMV) from the pig small intestine. When lactulose was incubated with BBMV, the hydrolytic activity of the enzyme towards the disaccharide was observed to be very low compared to that towards the lactose, but the linkage specificity β-(1→3), previously observed in lactose solutions, was not significantly affected. As in the case of lactose, lactulose transgalactosylation by BBMV synthesizes the corresponding 3'-galactosyl derivative (β-Gal-(1→3)-β-Gal-(1→4)-β-Fru). Fructose released during lactulose hydrolysis was found to be good acceptor for the transgalactosylation reaction, giving rise to the synthesis of the disaccharide β-Gal-(1→5)-Fru. When incubating an 80/20 mixture of lactulose/galactose, the presence of galactose did not affect the qualitative composition of the transglycosylated substrate but enhanced the synthesis of β-Gal-(1→5)-Fru and decreased the synthesis of β-(1→3) glycosidic bonds. The marked tendency for synthesizing this linkage indicates that under hydrolytic conditions, β-Gal-(1→3)-Gal- and β-Gal-(1→5)-Fru glycosidic bonds would be preferentially digested.

Phototropic bending of intact and wounded potato shoots

Intact and wounded shoots of in vitro cultured potato were investigated in situ to determine how their phototropic (PT) bending capacity was affected by water availability and exogenous auxin supplementation. Wounding strongly decreased PT bending but it recovered upon supplementation of water, auxin or both. Intact shoots required neither water nor auxin, while shoot segments required both. Shoot cuttings required only water, while, like shoot segments, decapitated shoots had a strong requirement for auxin. Water supplementation was beneficial in all treatments and PT bending was not affected in cultures that were submerged in water for a short period. Sucrose and inorganic salts present in the medium strongly affected PT bending capacity of cultures, favouring combinations with lower concentrations of both. Sucrose alone strongly promoted PT bending up to a concentration of 5%. Osmotic shock induced by the addition of small volumes of highly concentrated carbohydrate solutions (sucrose, glucose or sorbitol) induced a rapid but transient decline in PT bending capacity. These results indicate that water availability is a major factor that affects PT bending in potato plantlets.

Dissecting the effects of concentrated carbohydrate solutions on protein diffusion, hydration, and internal dynamics.

We present herein a thorough description of the effects of high glucose concentrations on the diffusion, hydration and internal dynamics of ubiquitin, as predicted from extensive molecular dynamics simulations on several systems described at fully atomistic level. We observe that the protein acts as a seed that speeds up the natural propensity of glucose to cluster at high concentration; the sugar molecules thus aggregate around the protein trapping it inside a dynamic cage. This process extensively dehydrates the protein surface, restricts the motions of the remaining water molecules, and drags the large-scale, collective motions of protein atoms slowing down the rate of exploration of the conformational space despite only a slight dampening of fast, local dynamics. We discuss how these effects could be relevant to the function of sugars as preservation agents in biological materials, and how crowding by small sticky molecules could modulate proteins across different reaction coordinates inside the cellular cytosol.

Nutrition for endurance sports: Marathon, triathlon, and road cycling

Endurance sports are increasing in popularity and athletes at all levels are looking for ways to optimize their performance by training and nutrition. For endurance exercise lasting 30 min or more, the most likely contributors to fatigue are dehydration and carbohydrate depletion, whereas gastrointestinal problems, hyperthermia, and hyponatraemia can reduce endurance exercise performance and are potentially health threatening, especially in longer events (>4 h). Although high muscle glycogen concentrations at the start may be beneficial for endurance exercise, this does not necessarily have to be achieved by the traditional supercompensation protocol. An individualized nutritional strategy can be developed that aims to deliver carbohydrate to the working muscle at a rate that is dependent on the absolute exercise intensity as well as the duration of the event. Endurance athletes should attempt to minimize dehydration and limit body mass losses through sweating to 2–3% of body mass. Gastrointestinal problems occur frequently, especially in long-distance races. Problems seem to be highly individual and perhaps genetically determined but may also be related to the intake of highly concentrated carbohydrate solutions, hyperosmotic drinks, as well as the intake of fibre, fat, and protein. Hyponatraemia has occasionally been reported, especially among slower competitors with very high intakes of water or other low sodium drinks. Here I provide a comprehensive overview of recent research findings and suggest several new guidelines for the endurance athlete on the basis of this. These guidelines are more detailed and allow a more individualized approach.

Nutritional Considerations in Triathlon

Triathlon combines three disciplines (swimming, cycling and running) and competitions last between 1 hour 50 minutes (Olympic distance) and 14 hours (Ironman distance). Independent of the distance, dehydration and carbohydrate (CHO) depletion are the most likely causes of fatigue in triathlon, whereas gastrointestinal (GI) problems, hyperthermia and hyponatraemia are potentially health threatening, especially in longer events. Although glycogen supercompensation may be beneficial for triathlon performance (even Olympic distance), this does not necessarily have to be achieved by the traditional supercompensation protocol. More recently, studies have revealed ways to increase muscle glycogen concentrations to very high levels with minimal modifications in diet and training. During competition, cycling provides the best opportunity to ingest fluids. The optimum CHO concentration seems to be in the range of 5-8% and triathletes should aim to achieve a CHO intake of 60-70 g/hour. Triathletes should attempt to limit body mass losses to 1% of body mass. In all cases, a drink should contain sodium (30-50 mmol/L) for optimal absorption and prevention of hyponatraemia.Post-exercise rehydration is best achieved by consuming beverages that have a high sodium content (>60 mmol/L) in a volume equivalent to 150% of body mass loss. GI problems occur frequently, especially in long-distance triathlon. Problems seem related to the intake of highly concentrated carbohydrate solutions, or hyperosmotic drinks, and the intake of fibre, fat and protein. Endotoxaemia has been suggested as an explanation for some of the GI problems, but this has not been confirmed by recent research. Although mild endotoxaemia may occur after an Ironman-distance triathlon, this does not seem to be related to the incidence of GI problems. Hyponatraemia has occasionally been reported, especially among slow competitors in triathlons and probably arises due to loss of sodium in sweat coupled with very high intakes (8-10 L) of water or other low-sodium drinks.

Flavor Preferences Conditioned by Intragastric Polycose in Rats: More Concentrated Polycose Is Not Always More Reinforcing

LUCAS, F., A. V. AZZARA AND A. SCLAFANI. Flavor preferences conditioned by intragastric Polycose in rats: More concentrated Polycose is not always preferred. PHYSIOL BEHAV 63(1) 7–14, 1998.—Prior studies have obtained conditioned preferences for flavors paired with intragastric (IG) infusions of Polycose (hydrolyzed starch) at concentrations of 1–32% over a different flavor paired with IG water. The present study determined if rats would also learn to prefer a flavor paired with concentrated Polycose infusion over a flavor paired with a more dilute Polycose infusion. In Experiment 1, adult female rats were food-deprived and trained during alternating one-bottle sessions (30 min/day) to associate one flavored solution (the CS+8) with IG infusions of 8% Polycose, a second flavored solution (the CS+16) with IG infusions of 16% Polycose, and a third flavored solution (the CS−) with IG water infusions. In subsequent choice tests, the rats displayed similar preferences for the CS+8 and CS+16 over the CS−, but preferred the CS+16 to CS+8 in a direct choice test. A similar preference pattern was obtained in 22 h/day tests with the rats nondeprived. In Experiment 2, new rats were similarly trained and tested but with CS+16 and CS+32 solutions paired with 16% and 32% Polycose infusions, respectively. The rats preferred both CS+ solutions over the CS− solution in the short- and long-term tests. However, the CS+16 was preferred over the CS+32 by the food-deprived rats in the short-term tests. The two CS+ solutions were equally preferred in the long-term tests with food ad lib. These and other findings indicate that the postingestive reinforcing action of Polycose increases as concentration increases from 1% to 16% but does not increase further, and may actually decrease, at a 32% concentration. The rapid satiating effect of concentrated carbohydrate solutions may limit their reinforcing consequences.

Exogenous carbohydrate utilisation: Effects on metabolism and exercise performance

It is generally recognised that a decrease in carbohydrate availability can lead to the development of fatigue during prolonged exercise in humans. Administration of glucose or other carbohydrates before or during exercise has been shown to postpone fatigue, conserve muscle glycogen and improve performance. Carbohydrates can be categorised according to their ability to increase blood glucose concentration (known as glycaemic index) and by the extent they stimulate the release of insulin. The glycaemic index is reflected in the rate at which consumed carbohydrate is made available in the blood. Glucose is the only type of carbohydrate that can readily be oxidised by skeletal muscle for energy production. Gastric emptying is the primary factor limiting the rate of carbohydrate delivery to the blood and therefore influences the utilisation of exogenous carbohydrate ingested before or during exercise. Various methods have been used to assess the oxidation of exogenous carbohydrates during exercise. Peak rates of CHO oxidation during exercise have been reported between 0.4 and 1.0 g/min, and the rates of oxidation do not appear to be influenced to a major extent by the use of multiple drinking schedule in comparison with a single bolus schedule. Previous studies also suggest that the ingestion of fructose during exercise does not offer any additional benefits over ingestion of glucose or glucose polymer solutions of similar concentration. The hormones insulin, glucagon and adrenaline together with cortisol and growth hormone play key roles in the regulation of carbohydrate metabolism during exercise. Ingestion of moderately concentrated carbohydrate solutions (4–8%) enhances prolonged exercise performance and is appropriate for optimising energy and fluid delivery without causing adverse effects. The ergogenic effects of carbohydrate ingestion on performance during intermittent exercise such as competitive sports are less well established, although the evidence to date suggests diminished performance when carbohydrate are limiting.

A New Approach to the Kinetics of Colour Formation in Concentrated Carbohydrate Solutions

AbstractThe deduction of a kinetic model of colour formation, especially by the Maillard reaction, in heated concentrated carbohydrate solutions is described on the basis of systematic experimental studies. The main parameters of the colour formation are included such as reaction time, temperature, pH, amounts of sucrose, glucose, fructose, amino‐nitrogen and dry matter. The model is based on a three step first order consecutive reaction beginning with sucrose via glucose/fructose and dicarbonyl compounds to the colourants. The suitability of the model was tested on model experiments as well as on experiments with technical solutions in an evaporation station. It resulted in a good correspondence between measured and calculated colour values. The potentials of the model are discussed and the range of applications is pointed out.

The influence of beverage composition and gastrointestinal function on fluid and nutrient availability during exercise

In order to maximize fluid and/or carbohydrate availability during exercise, in which performance may be limited by one or the other, the composition and ingestion pattern of a beverage can be adjusted accordingly. As carbohydrate concentration increases, the rate of gastric emptying decreases. With more highly concentrated carbohydrate solutions, the net fluid absorption of water in the intestine is also reduced, although lower concentrations of glucose containing carbohydrates (∼3‐7%) actually can stimulate net intestinal absorption. Increasing the osmolality of a beverage can reduce the gastric emptying rate, but it has a more profound effect on gastric and intestinal secretions. Hyperosmolality increases secretions and as such decreases the rate of net absorption. Sodium inclusion in a beverage is warranted not only to offset losses (primarily from sweat) but, moreover, to promote fluid absorption in the intestine and to increase fluid retention. Recommendations include maintenance of fluid balance by ingestion of sufficient fluids, immediately prior to and during exercise, to restrict body weight losses to ≤1%. Somewhat more concentrated carbohydrate solutions may be ingested when the risk of hypohydration is low and performance is limited by carbohydrate availability. With increasing carbohydrate concentrations, at least up to 18%, there is a greater rate of carbohydrate passage through the gastrointestinal tract. When carbohydrate concentrations exceed 5%, the type of carbohydrate (mono‐ or disaccharides, long chain polymers, etc.) is important as the osmolality increases with increasing concentration and decreasing chain length. Thus, when concentrations of >8% are warranted, based on energy demands, there is an advantage to using glucose polymer solutions, owing to a decrease in gastrointestinal secretions and, hence, an increase in rate of net fluid absorption.

Correlating diffusion coefficients in concentrated carbohydrate solutions

AbstractThe diffusivities and the vapor‐liquid equilibrium coefficients of two organic components, 1‐hexanol and 2‐butanone, were measured in concentrated maltodextrin solutions using newly developed techniques. Accurate determination of these quantities required complete material balances of the two phases and control of the water concentration in the experimental cell. The diffusion coefficients of these solutes correlated with solution viscosity to the 1/2 power over a range of temperatures and concentrations. Other literature data for diffusion coefficients in concentrated malto‐dextrin and sugar solutions are shown to correlate with viscosity.

Effects of food deprivation on intake of solid and liquid sugars in the rat

In free-feeding rats, glucose at 0.025 M or 2 M evokes a vigorous bout of drinking. Powdered sucrose evokes more feeding than would occur without it, but powdered glucose does not. Food deprivation has little effect on intake of 2 M glucose, but it markedly augments intake of the powders, which rises to caloric-intake values higher than that of the 2 M solution. This occurs even if the powders are offered only after solution intake has come to an end and at a time when it would remain inhibited. We conclude: 1. Some sweet-tasting commodities will evoke ingestive behavior in free-feeding rats, but others, some of them even sweeter, will not. 2. Solid carbohydrates follow different laws from concentrated carbohydrate solutions, in that the former, but not the latter, rise with deprivation. Intake of powders must therefore be limited or satiated by different and more permissive mechanisms from the ones that limit solution intake.

Release of Feeding by the Sweet Taste in Rats: The Influence of Body Weight

Rats that are not deprived of water, or that are overhydrated artificially, drink sweet solutions with avidity. We show that intake of sweet solutions is sensitive to nutritional status, suggesting that the rats are treating the solutions as liquid diets and “eating” rather than drinking them. First, when rats are force-fed to mild obesity, intake of dilute and concentrated saccharin and carbohydrate solutions is progressively reduced. Secondly, when weight loss is forced by restricted feeding, intake of saccharin and dilute carbohydrate is elevated, but intake of concentrated carbohydrate solutions is not. Perhaps the postingestive effects of concentrated sugar solutions set a limit on ingestion, so that intake can be driven below that limit as weight is gained, but cannot rise above it as weight is lost.

Biochemical monitoring of patients on parenteral nutrition

For effective intravenous administration of nutrients such as carbohydrates, amino acids and electrolytes it is essential that the patients are monitored during this regime. Therefore, a number of patients were studied to determine what biochemical parameters were significantly altered during such infusions and thus required special attention. Most of the relevant information has been derived from one patient. This person was on parenteral nutrition for over 300 days and during this period he developed many problems which were directly associated with this regime. The data derived from this patient focused attention on certain biochemical parameters i.e. albumin, K+, BUN, phosphate and fluid balance which demonstrated significant variations during the infusion period. In particular, a pronounced hypophosphataemia developed when concentrated carbohydrate solutions were infused. For effective intravenous administration of nutrients such as carbohydrates, amino acids and electrolytes it is essential that the patients are monitored during this regime. Therefore, a number of patients were studied to determine what biochemical parameters were significantly altered during such infusions and thus required special attention. Most of the relevant information has been derived from one patient. This person was on parenteral nutrition for over 300 days and during this period he developed many problems which were directly associated with this regime. The data derived from this patient focused attention on certain biochemical parameters i.e. albumin, K+, BUN, phosphate and fluid balance which demonstrated significant variations during the infusion period. In particular, a pronounced hypophosphataemia developed when concentrated carbohydrate solutions were infused.