Total and soluble beta-glucan content and effects of various treatments of barley grain on extractability and molecular characteristics of soluble beta-glucan were studied. Four types of hulless barley (normal, high amylose, waxy, and zero amylose waxy) from 29 registered and experimental genotypes were analyzed. For each, moisture, protein, amylose, 100 kernel weight, starch, beta-glucan (total and soluble), beta-glucanase activity, and slurry viscosity were determined. Significant differences in total beta-glucan were observed among the groups, with average values of 7. 49%, 6.86%, 6.30%, and 4.38% for high amylose, waxy, zero amylose waxy, and normal barley, respectively. The extractability of beta-glucan in high amylose barley was relatively low (20.6-29.7%) compared to that in normal (29.8-44.3%), zero amylose waxy (34.0-52. 5%), and waxy (36.7-52.7%) barley genotypes. Viscosity of barley flour slurries was affected by the content of soluble beta-glucans, beta-glucanase activity, and molecular weight of beta-glucans. Hydrothermal treatments (autoclaving and steaming) of barley had no effect on extractability of beta-glucans, but prevented enzymic hydrolysis of beta-glucans, and thereby substantially improved their molecular weight. The addition of enzymes (protease and esterase) during extraction and/or physical treatments (sonication) increased extractability of beta-glucans from barley.

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The aim of the present study was to determine if the consumption of barley tortillas varying in fibre and/or starch composition affected postprandial glucose, insulin, glucagon-like peptide-1 (GLP-1) or peptide YY concentrations. A double-blind, randomised, controlled trial was performed with twelve healthy adults. They each consumed one of five barley tortillas or a glucose drink on six individual visits separated by at least 1 week. Tortillas were made from 100 % barley flour blends using five different milling fractions to achieve the desired compositions. All treatments provided 50 g of available carbohydrate and were designed to make the following comparisons: (1) low-starch amylose (0 %) v. high-starch amylose (42 %) with similar b-glucan and insoluble fibre content; (2) low b-glucan (4·5 g) v. medium b-glucan (7·8 g) v. high b-glucan (11·6 g) with similar starch amylose and insoluble fibre content; and (3) low insoluble fibre (7·4 g) v. high insoluble fibre (19·6 g) with similar starch amylose and b-glucan content. Blood was collected at fasting and at multiple intervals until 180 min after the first bite/sip of the test product. Amylose and insoluble fibre content did not alter postprandial glucose and insulin, but high-b-glucan tortillas elicited a lower glucose and insulin response as compared to the low-b-glucan tortillas. The tortillas with high insoluble fibre had a higher AUC for GLP-1 as compared to the tortillas with low insoluble fibre, whereas amylose and b-glucan content had no effect. Results show that processing methods can be used to optimise barley foods to reduce postprandial blood glucose responses and factors that may influence satiety.

Effects of Processing on Oat β-Glucan PropertiesKilning and Flaking. Most of the oats used by the food industry are processed into groats, flakes, flour, or bran prior to incorporation in other food products or cooking by the enduser (e.g., porridge). Initial processing involves a heat-moisture treatment called kilning-the primary purpose of which is to inactivate lipase activity that leads to fat rancidity and decreased shelf life. In kilning and subsequent steaming and flaking processes other enzymes such as b-glucanase are also inactivated. As a result, kiln-dried oat groats, flakes, bran, and flour have virtually no endogenous enzyme activity (6). In our lab tests we found the b-glucan viscosity and MW of untreated oats (or "raw oats") to be dramatically lower than in the corresponding kilned material, which is consistent with inactivation of b-glucanase enzymes during the kilning process and suggests that this process is critical to the maintenance of b-glucan physicochemical properties. Table I shows how b-glucan viscosity increased with each subsequent heat-treatment step during primary oat processing (38). In his thesis study, Wang (38) also found variation between oat genotypes with respect to b-glucan physicochemical properties (Table I).Baking and Freezing. Studies testing the effects of baking and frozen storage on oat b-glucan properties have shown that both types of processing can cause a decrease in the MW, soluhttp://dx.

A set of 31 murine monoclonal antibodies was produced against (1-->3,1-->4)beta-d-glucan from oats (Avena sativa L.) chemically cross-linked to keyhole limpet hemocyanin. Monoclonal antibodies were tested for their cross-reactivity to related and unrelated polysaccharides. The antibodies reacted strongly to unmodified beta-glucan from oats and barley (Hordeum vulgare L.) and to lichenan from Icelandic moss, a polysaccharide with a structure similar to that of beta-glucan but which is not encountered in cereals. Cross-reaction to other polysaccharides tested was minimal at physiological levels. An enzyme-linked immunosorbent assay (ELISA) that could routinely detect and quantify nanogram levels of soluble beta-glucan extracted from the flour of oats or barley was designed with one of these monoclonal antibodies. The beta-glucan extraction procedure from ground oat and barley samples and the ELISA were both optimized for reproducibility, accuracy, and throughput, and results were compared to values obtained from an established, commercially available enzyme-based assay. Correlations between the two assays were consistently high (r (2) > 0.9), indicating that the ELISA presented in this paper is a valuable alternative for assaying beta-glucan levels in cereals and cereal products, both routinely and in preparations in which beta-glucans are present in nanogram amounts. Development of the extraction procedure for ELISA is discussed.

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Cereal Chem. 94(2):333-340