Effect of aging on endosperm characteristics and processing functionality of sorghum and corn /
Accelerated aging at 500C significantly affected the
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1996.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=739363481&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Accelerated aging at 500C significantly affected the physical, chemical, and processing properties of sorghum and corn. Aging caused associations between starch granules/protein matrix/cell walls. During aging, floury areas of the endosperm became more like cornous endosperm; corneous areas developed strong associations causing the endosperm to fracture through endosperm cells and starch granules instead of between the endosperm cell walls, which is common for non-aged corn. During aging, albumins and globulins decreased; proteins requiring a reducing agent and/or an alkaline pH for solubilization increased. Starch solubility at 850C decreased in aged materials; pasting and gelatinization properties were significantly restricted by aging. Treating aged samples with a reducing agent prior to extraction partially reversed the solubility trend implying that protein oxidation reactions were partially responsible for decreased starch functionality. Starch solubility at 1200C was not influenced by aging. Aged meal extrudates were less expanded and had greater bulk density than the control meals. Starch was more damaged and more soluble at 650C in extrudates from aged materials than in control meal. Viscosities were higher in control extrudates because starch damage was not as severe during extrusion. At low extrusion moistures, aged meals required more energy to melt, which caused increased torque, SME, and zone 1 temperatures. At higher extrusion moistures, fewer differences were seen because the extra water aided melting of the material and decreased friction. Aging of corn decreased pericarp removal, nixtamal moisture, and cooking losses when evaluated at shorter cooking times and lower cooking temperatures. These changes would be most evident to dry masa flour manufacturers because nixtamal for dry masa flour is cooked less than nixtamal for fresh masa.Aging of grain during storage significantly affected extrusion and alkaline cooking properties. The differences were particularly evident during extrusion with limited feed moisture or nixtamalization using short cooking times or lower cooking temperatures. These observations may explain why processors notice differences in extrudate properties when corn meals with comparable size, shape, and other characteristics are extruded into snacks and breakfast foods. |
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| Item Description: | Vita. "Major Subject: Food Science and Technology". |
| Physical Description: | xiv, 89 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 76-80. |