Degree Type


Date of Award


Degree Name

Master of Science


Food Science and Human Nutrition


Several specialty soy flours were used to make soymilk, tofu and doughnuts. Low lipoxygenase and low stachyose (LPLS)-, low lipoxygenase- and regular soy flours yielded 10-30% more soymilk and produced 50% less waste (okara) than soy chips, soy flakes, and soybeans, using the Takai Automated Soymilk and Tofu System (steam injection cooking). Use of soy flour reduced the soymilk processing time while producing good quality soymilk with 83.6-86.8% and 84.3-86.1 % solids and protein recoveries, respectively. Soymilk made from soy flours, chips and flakes had significantly less fat (0.54-1.04%) than soymilk made from the whole beans (1.45%). The lowest fat content was found in the LPLS-soy flour soymilk (0.54%). Despite better yield, tofu made from soy flour did not have a smooth texture (cracks) as did tofu made from other soy ingredients. Curds were incompletely formed with milky whey left behind after coagulation and pressing.;No significant difference in "beaniness" was found between all the soymilk samples, while the LPLS-tofu was rated as less beany than the flake tofu. When roasted full-fat soy flours of 30 and 44 PDI (protein dispersibility index) and defatted soy flours of 20 and 70 PDI were used to replace 30% nonfat dry milk and or eggs in doughnuts, the color, texture, moisture, fat and protein contents, fat absorption, and the sensory attributes of the doughnuts were very similar among all the samples including the control (no soy). With the exception of the full-fat low stachyose soy flour, other soy flours did not produce significant soy flavor and off-flavors in doughnuts (up to 10% soy flour addition). Although the defatted 70 PDI soy flour reduced the overall fat absorption by 40%, the doughnuts were less preferred by the panelists than doughnuts with full-fat soy flour added. Drier and less tender attributes occurred at the higher addition levels which could be the reasons for lower preference. The full-fat 44 PDI soy flour reduced the fat absorption by 13% (overall), while preserving the sensory attributes of doughnuts in this study.



Digital Repository @ Iowa State University,

Copyright Owner

Yuen-Ching Low



OCLC Number


File Format


File Size

130 pages