Analytical Aspects of Total Starch Polarimetric Determination in Some Cereals

Starch is the most important digestible polysaccharide present in foods and feeds. The starch concentration in cereals cannot be determined directly, because the starch is contained within a structurally and chemically complex matrix. Fine grinding and boiling in dilute HCl are preparative steps necessary for complete release of the starch granules from the protein matrix. Starch can be determined using simple and inexpensive physical methods, such as density, refractive index or optical rotation assessment. The polarimetric method allows the determination even of small starch contents due to its extremely high specific rotation. For more accurate results, the contribution of free sugars is eliminated by dissolution in 40% (V/V) ethanol. The influence of other optically active substances, which might interfere, is removed by filtration/clarification prior to the optical rotation measurement

Effect of Heat Treatment and Digestive Enzymes on Cereal Water-Retention Capacity

Thermal treatment of cereal grains affects carbohydrate and micronutrient content and bioavailability. Water-retention capacity (WRC) is an important index for the effects of fiber in the diet and the metabolic activity of fiber along the gut. This study evaluated the effect of thermal treatment and digestive enzymes on wheat and barley WRC. Ground wheat and barley samples were heated for different time periods at 150ºC before in vitro gastric and intestinal digestion. WRC values in heat treated wheat and barley are at higher levels as compared to the values of untreated cereals. WRC in barley ranged from 1.026 g water/g DM (untreated) to 1.36 g water/g DM (heated at 150ºC for 15 minute). The increase was much lower in heat treated wheat, from 0.973 g water/g DM up to 1.03 g water/g DM at 5 minutes heating time

Glucose Release During in Vitro Digestion of Wheat

The research investigated the dynamics of released glucose from whole wheat flour during in vitro gastric and intestinal digestion. Two experiments were conducted. Experiment 1 (gastric digestion) was an enzymatic hydrolysis with a pepsin solution at pH 2.0 and 37°C for 120 minutes. In experiment 2, first step was followed by the hydrolysis with the multi-enzyme pancreatin (intestinal digestion), at pH 6.8 and 37°C for 4 h. The released glucose (RG) and the refractive index (RI) were determined from the supernatant obtained after centrifugation. Experiments showed an initial increase in the glucose released from 1 g wheat up to 0.472 mg/mL after 1 h of gastric digestion, then followed by decrease. The lowest value was recorded after 2 hours of gastric digestion (0.332 mg/mL). The concentration of the reducing sugars increased throughout the intestinal digestion from 0.549 mg/mL up to 1.990 mg/mL, as a result of starch hydrolysis to dextrins, maltose and then to glucose. The high positive correlation between RG and RI suggests that RI may be used as a simple and rapid method for estimating the released glucose during in vitro digestion

Helical sorbent microtrap for continuous sampling by a membrane and trap interface for on-line gas chromatographic monitoring of volatile organic compounds

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Glucose Release During in Vitro Digestion of Barley

The dynamics of released glucose (RG) and refractive index (RI) in the supernatant obtained during in vitro gastric and intestinal digestion of whole barley flour was studied. The in vitro digestion consisted of a two-step enzymatic procedure: (1) initial simulation of gastric digestion using pepsin and (2) simulation of small intestine digestion using multi-enzyme pancreatin. Experiments on 1 g barley flour showed an initial increase in RG concentration up to 0.379 mg / mL at one hour from the onset of gastric digestion, then a decrease in concentration, reaching the lowest value in 2 hours of gastric digestion (0.126 mg/mL). The concentration in reducing sugars increased throughout the intestinal digestion from 0.422 mg/mL up to 2.824 mg/mL, as a result of starch hydrolysis to dextrins, maltose and then to glucose. RI can give information on the amount of glucose released during digestion due to the high positive correlation found between RG and RI (r = 0.761)