Degree Type

Dissertation

Date of Award

1999

Degree Name

Doctor of Philosophy

Department

Food Science and Human Nutrition

First Advisor

Cheryll A. Reitmeier

Second Advisor

Lester A. Wilson

Abstract

Flavor is the most important factor limiting consumption of soy foods in Western markets. Soybean lines lacking one or several of the lipoxygenase isozymes involved in flavor have been developed. Sensory evaluation provides relevant information related to actual perception and also presents some challenges that must be addressed. Perception of flavor by people varies according to people's background. The use of terminology to describe the sensory attributes must be addressed. Also, the dynamism of the perceived intensity of some sensory attributes must be considered for evaluation of soy products;In the first part of this study, three groups of panelists from the U.S., Japan and China were trained to describe and compare soymilk or tofu made from lipoxygenase-free and normal lines. Soymilk made from lipoxygenase-free soybeans had less cooked beany aroma, less cooked beany flavor and less astringency. Panelists noted no differences between lipoxygenase-free and normal soybeans for milky flavor, wheat flavor, thickness, chalkiness or aftertaste. Tofu made from lipoxygenase-free soybeans had less cooked beany flavor than that made from normal soybeans. There were no differences in cooked beany aroma, raw beany aroma, raw beany flavor, wheat flavor, astringency, hardness, darkness or yellowness;The second part of the research comprised the description of the concept related to the 'beany' attributes. A panel of five judges was intensively trained to describe and evaluate different soymilks. Descriptors used to describe 'beaniness' were 'raw as hexanal' for flavor or aroma, 'grassy' flavor, and 'sweet as green floral' flavor. Significant differences (p < 0.01) were found among commercial soymilk and soymilks processed from normal or lipoxygenase-free soybean lines and lipoxygenase-free soybeans stored for 1 yr at 4°C;The third part of the study addressed the changes in perception with time for bitterness and beaniness in soymilk. Time intensity was used to evaluate the effect of sugar (0, 2.5% and 5%), temperature (25°C and 5°C) and soybean line (normal and lipoxygenase-free) on the intensity of bitterness and beaniness of soymilk. Temperature did not have any important effect on bitterness or beaniness. Total intensity of bitterness was significantly reduced by the use of lipoxygenase-free soybeans or addition of sugar to the 2.5% level. Beaniness maximum intensity was reduced with the combined effect of using lipoxygenase-free soybeans and 2.5% sugar.

DOI

https://doi.org/10.31274/rtd-180813-13454

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Ana Victoria Torres-Penaranda

Language

en

Proquest ID

AAI9940249

File Format

application/pdf

File Size

78 pages

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