http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Characteristics of high-protein texturized products produced by a single-screw extruder
The effects of raw material composition (feed moisture, fat and corn starch levels) and process temperature on characteristics of high-protein extrudates produced by a laboratory-scale single-screw extruder from non-dehydrated beef, defatted soy flour, and corn starch were investigated using response surface methodology (RSM). Physical and rheological properties (expansion ratio, bulk density, shear force, Hunter color, water absorption) and microstructural properties of the extrudates were determined. The RSM results showed that certain ranges of feed moisture and corn starch and process temperature were required for minimum bulk density and shear force values for the extrudate. Increasing the feed fat level increased the product bulk density and decreased expansion ratio. Microstructural examinations revealed that the product with high expansion ratio, low bulk density, and low shear force tended to have well-developed air cells, continuous protein matrices, and smooth cell wall surfaces. Three selected products--a high-beef (29%) low-fat (2.96%) product, a low-beef (20%) low-fat (2.96%) product, and a high-beef (29%) high-fat (5%) product--were manufactured based on the RSM results. All three products showed overall palatability scores ranging from 5 ("slightly palatable") to 6 ("moderately palatable") on an 8-point scale. The high-beef low-fat product was softer than the low-beef low-fat product. Both low-fat products showed microstructures with well-developed large air cells and continuous protein matrices. Protein matrices and air cells were not fully developed in the high-beef high-fat product. The three products were higher in methionine and lysine than defatted soy flour. They also had higher percentages of stearic acid and oleic acid than defatted soy flour and higher percentages of linoleic acid than beef. The three products were microbiologically safe during 150 days of storage at 37°C. The extent of lipid oxidation in the three products during 210 days of storage at 37°C was evaluated by thiobarbituric acid (TBA) method, florescence assay, and measurement of conjugated dienes and trienes. TBA values were found to be unsuitable due to extensive crosslinking of malonaldehyde with other food components. Fluorescence intensity of each product increased steadily during storage, with the product of the highest fat level showing the highest fluorescent intensity among the three products throughout entire storage period. Changes in conjugated dienes and trienes during storage were not consistent, but the high-fat product had a higher concentration of conjugated dienes at each storage period than the low-fat products. The low-beef low-fat product had the lowest concentration of conjugated trienes at each storage period.
"Major subject: Food Science and Technology."