Effect of moisture, pressure, and temperature on enzymatic starch degradation of barley and sorghum grain

Frederick, H.M. and Theurer, B. and Hale, W.H. (1973) Effect of moisture, pressure, and temperature on enzymatic starch degradation of barley and sorghum grain. Journal of Dairy Science, 56 (5). pp. 595-601.

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Samples of barley and sorghum grains were processed by dry rolling, dry flaking, steam processing then flaking or pressure cooking than flaking. Dry grain with 7 to 9% moisture was passed through a roller mill. For dry flaking, the rollers were preheated to 77 deg C and set at 0.005 cm tolerance. Steam-processed grain was exposed to high-moisture steam in a commercial tempering chamber before flaking. Pressure-cooked grain was prepared in a closed cylinder with pressure applied by high-moisture steam. Grain was cooked for 1 or 5 min at pressure of 1.4 to 7.0 kg/cm2. All samples were air-dried and ground through an 80-mesh sieve before analysis. Total starch and water-soluble carbohydrate, measured as total reducing sugars or glucose, were estimated. Starch digestiblity was estimated in vitro by incubating the grains with a buffered homogenate of beef pancreas for 30 min at 40 deg . The combined effects of moisture, heat and pressure on enzymic degradation of starch in sorghum grain was studied by subjecting dry, steamed or soaked grain to different pressures in a hydraulic press. The plates were at room temperature in the first trial and at 98 deg in the second. Total starch content and starch digestibility were measured. Addition of water to the grain by soaking or steaming at atmospheric pressure did not greatly improve enzymic digestion of starch of either grain. Starch digestibility was increased by pressure in a hydraulic press or roller mill and the response was greater when the grain was moist. The greatest increase in starch digestion was with processes involving moisture, heat and pressure; all interactions between these were significant. Flaking the grain after steam processing or pressure cooking increased the digestibility of starch. The best cooking pressure for both grains, with flat flaking, was 4.2 kg/cm2. The critical pressure in a hydraulic press for increasing starch digestion in dry, steamed and soaked sorghum grain was 140 kg/cm2 with the pressure plates at room temperature. Heating the plates to 98 deg reduced the critical pressure for steamed or soaked grain, but not for dry grain. Starch digestibility in moist grain was increased by pressures of 35 and 140 kg/cm2

Item Type: Article
Author Affiliation: Department of Animal Science, University Arizona, Tucson 85721, USA
Subjects: Animal Husbandary
Crop Improvement > Seed Technology
Divisions: Sorghum
Depositing User: Ms K Syamalamba
Date Deposited: 24 Aug 2012 09:03
Last Modified: 24 Aug 2012 09:05
Official URL: http://dx.doi.org/10.3168/jds.S0022-0302(73)85225-...
URI: http://eprints.icrisat.ac.in/id/eprint/7511

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