Degree Type

Dissertation

Date of Award

1988

Degree Name

Doctor of Philosophy

Department

Food and Nutrition

First Advisor

Jane A. Love

Abstract

Kinetic studies of thermal thiamin breakdown in phosphate-buffered model systems and ground pork were conducted over the temperature range 75 to 95°C in order to evaluate the effects of pH, processing temperature, water activity and different kinds of reducing sugars on thiamin stability. Semilog plots of thiamin retention versus heating time at 75, 85, and 95°C for model systems and ground pork gave straight lines with high coefficients of determination (r[superscript]2 = 0.95-0.99) for every combination of processing parameters, which indicated that the rates of thiamin degradation were adequately described by a first order reaction rate model. The Arrhenius activation energy values indicated that thiamin in pork (85-93 kJ/Mole) was less temperature dependent than that in aqueous buffered model systems (100-140 kJ/Mole). The relatively constant activation energy over the temperature range from 75 to 95°C, which was proved by high coefficients of determination (r[superscript]2 = 0.84-0.99), is an indication that the degradation pathway remained the same over the investigated range;Temperature was the most important factor influencing thiamin stability. At high temperatures and above neutral pH, thiamin was very unstable and easily destroyed during thermal processing. An increase in thiamin concentration retarded the thiamin degradation rate. Reducing water activity of the aqueous model to 0.90 by adding glycerol adversely affected thiamin retention. One of the main interests in this study was to confirm the effect of the browning reaction between thiamin and reducing sugars on thiamin breakdown. The order of increasing magnitude of their effect of the reducing sugars on thiamin breakdown was: xylose, fructose, glucose, and sucrose. This order matches the general findings in Maillard browning reaction studies in model systems using amino acids and reducing sugars.

DOI

https://doi.org/10.31274/rtd-180813-12233

Publisher

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

Copyright Owner

Eun Seung Lee

Language

en

Proquest ID

AAI8825413

File Format

application/pdf

File Size

107 pages

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