Title page for ETD etd-07072009-150815


Type of Document Master's Thesis
Author Futch, Jonathan
Author's Email Address jfutch2@tiger.lsu.edu
URN etd-07072009-150815
Title Altering Sweet Potato Starch Functionality by Amino Acids and pH Treatments
Degree Master of Science (M.S.)
Department Food Science
Advisory Committee
Advisor Name Title
Joan King Committee Chair
Subramaniam Sathivel Committee Member
Zhimin Xu Committee Member
Keywords
  • sweet potato
  • starch
Date of Defense 2009-06-23
Availability unrestricted
Abstract
The sweet potato is a vegetable containing high levels of different vitamins and minerals, needed to protect the body against disease. This study focused on starch found in the Beauregard and Evangeline sweet potatoes and observed the effect of pH and amino acid additives altering the functionality of starch. These modifications of the Beauregard and Evangeline sweet potato starches will also be done to determine if an increase in resistant starch and slowly digestible starch is found.

Beauregard and Evangeline starches had similar gelatinization temperature and the two starches required the same amount of energy to gelatinize. In Freeze-dried Beauregard starch, peak temperature decreased with pH treatments and pH10 decreasing peak temperature to 68.7C. Histidine at pH10 decreased peak temperature to 69.7C. In Evangeline freeze-dried starch, histidine significantly decreased peak temperature, especially at pH10 for one hour (73.17C) compared to native. In Beauregard oven-dried starch, the control significantly lowered peak temperature compared to the native. pH3 and 10 were significant in lowering peak temperature of the starch. Lysine and histidine were significant amino acids in decreasing peak temperature. In Evangeline oven-dried starch, histidine at pH3 and pH10 were significant for decreasing peak temperature compared to the native starch.

Positively charge amino acids along with pH treatments caused significant alterations in pasting properties of both Beauregard and Evangeline sweet potato starches. Oven-dried starch was more responsive to changes in pasting characteristics than freeze-dried sweet potato starch. Evangeline oven-dried sweet potato starch, histidine lowered breakdown and with the addition of pH10 treatment breakdown decreased even further, increasing its stability to shear during cooking.

There was a trend towards increased RS with amino acids added at pH3 or pH10 versus pH3 or pH10 alone, especially for lysine and histidine. Freeze-dried Beauregard starch SDS showed large increases with pH3 for 1 hour and lysine and histidine at pH3 for 1 hour. SDS content increased in oven-dried Beauregard starch the most with arginine at pH3. Freeze-dried Evangeline starch SDS content increased the greatest with histidine at pH3. SDS content increased the greatest with lysine at pH3 for oven-dried Evangeline starch.

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