Author
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Lawton Jr, John |
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Submitted to: American Association of Cereal Chemists Meetings
Publication Type: Abstract Only Publication Acceptance Date: 8/25/1996 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Starch-based films containing starch fractions with higher than normal levels of amylose indicate that their films' mechanical properties have more stability in their percent elongation after aging than films containing normal levels of amylose. Aging studies were conducted for starch-based films to further clarify this phenomenon. Films contained 41% starch, 41% poly(vinyl alcohol), 15% glycerol, and 3% poly(ethylene-co-acrylic acid) on a dry basis. The amylose- amylopectin ratio of the starch fraction of the starch-base films was varied. The ratio was varied either by using maize varieties with different amylose contents or by adjusting the ratio with pure amylose and waxy cornstarch. Amylose content of the starch in the films ranged from close to 100% to close to 0%. Films were aged before testing ranging from 7 to 168 days. Films were stored at 50% relative humidity and 21 deg C before testing. Besides mechanical testing, films were monitored by differential scanning calorimetry and X-ray diffraction during aging. Films made with normal cornstarch had an initial %E that was much greater than films made with high amylose cornstarch (288, 156%, respectively). After aging for 168, days %E dropped to 98 %E for films made with normal cornstarch, whereas, films made with high amylose cornstarch was virtually unchanged at 144 %E. |
