Five dietary fibre rich ingredients were used at 5%, 10% and 15% replacement levels in a white flour cereal base to produce an extruded cereal product. The inclusion of the dietary fibres into the flour bases had no significant effect on the expansion ratio of the products. However, the bulk density of the extruded products increased with inulin addition. The pasting properties of the raw flour and fibre base as well as the extruded products were altered with the incorporation of dietary fibre, with guar gum enriched products showing elevated peak and final viscosity readings. This appeared to be related to moisture manipulation and hence the regulation of gelatinisation. In vitro starch hydrolysis of the raw bases and the extruded samples illustrated that the extrusion process significantly increased the availability of carbohydrates for digestion. Additionally, the inclusion of dietary fibres in the raw bases significantly reduced the rate and extent of carbohydrate hydrolysis of the extruded products. As such the addition of dietary fibres to extruded products reduced the amount of readily digestible starch components of breakfast products, and increased the amount of slowly digestible carbohydrates.

Numerous in vitro carbohydrate digestion methods exist for analysis of the likely glycaemic properties of foods. Generally these methods encompass simulations of oral, gastric and intestinal digestion processes, but the way in which physiological conditions are implemented across methods differs considerably. Some differences are in the mode of comminution, inclusion and duration of a gastric digestion, and choice of amylolytic enzyme. Incubation temperature, pH, duration and stirring mode also differ between methods. Such differences, particularly the method used to mimic chewing, can have a substantial influence on the relative estimate of glycaemic potency for a given food. To achieve estimates of high predictive power, and global relevance, a validated, standardised in vitro digestion method must be developed. This article provides a systematic review of commonly used and referred to in vitro carbohydrate digestion methods. Methodological discrepancies between protocols are identified thus defining the route a systematic standardisation investigation should take.

The effect of beta-glucan-enriched barley on lipid profile was highly variable between subjects, and there was no evidence of a clinically significant improvement in CVD risk across this group of mildly hyperlipidemic men.

Two non-starch polysaccharides, guar gum and wheat bran, were used at 15% replacement level in a cereal base to produce an extruded breakfast cereal product from both wholemeal and high-ratio wheat flour mixes. The inclusion of the non-starch polysaccharides into the flour bases had no significant effect on the expansion ratio of the products. However, the product density and bulk density of the extruded products increased with guar gum and wheat bran addition. The pasting properties of the raw flour and polysaccharide base as well as the extruded products were altered with the incorporation of polysaccharides, with guar gum-enriched products showing elevated peak and final viscosity readings. This appeared to be related to moisture manipulation and hence the regulation of gelatinisation. In vitro starch hydrolysis of the raw bases and the extruded samples illustrated that the extrusion process significantly increased the availability of carbohydrates for digestion. Additionally, the inclusion of non-starch polysaccharides in the raw bases significantly reduced the rate and extent of carbohydrate hydrolysis. This potentially glycaemic reducing action was also evident in the extruded products where the incorporation of guar gum at 15% yielded a reduction of starch hydrolysis of 36% in the wholemeal base and 32% in the high-ratio white wheat flour base.

Glycemic impact, defined as "the weight of glucose that would induce a glycemic response equivalent to that induced by a given amount of food" (American Association of Cereal Chemists Glycemic Carbohydrate Definition Committee, 2007), expresses relative glycemic potential in grams of glycemic glucose equivalents (GGEs) per specified amount of food. Therefore, GGE behaves as a food component, and (relative) glycemic impact (RGI) is the GGE intake responsible for a glycemic response. RGI differs from glycemic index (GI) because it refers to food and depends on food intake, whereas GI refers to carbohydrate and is a unitless index value unresponsive to food intake. Glycemic load (GL) is the theoretical cumulative exposure to glycemia over a period of time and is derived from GI as GI x carbohydrate intake. Contracted to a single intake of food, GL approximates RGI but cannot be accurately expressed in terms of glucose equivalents, because GI is measured by using equal carbohydrate intakes with usually unequal responses. RGI, on the other hand, is based on relative food and reference quantities required to give equal glycemic responses and so is accurately expressed as GGE. The properties of GGE allow it to be used as a virtual food component in food labeling and in food-composition databases linked to nutrition management systems to represent the glycemic impact of foods alongside nutrient intakes. GGE can also indicate carbohydrate quality when used to compare foods in equal carbohydrate food groupings.