RESEARCH OBJECTIVES - LAY TERMS
In order to maintain and increase
the economic value of these commodities in this ever increasing competitive
world, their quality attributes need to be preserved during processing
operations. These factors include
color, flavor, and texture. A major
objective of my lab is the study of food texture as it is affected by the
interactions of its components and the effect of food processing operations on
these interactions. The measure of food
texture is a relatively new area which promises to offer a means to monitor and
improve the quality and value of processed foods. We are developing new measurement techniques which will provide
information on the nature of fundamental chemical interactions of constituents
and their effect on the overall texture of foods.
RESEARCH OBJECTIVES - FOR PEERS
The rheological properties of heat
induced whey protein gels was studied by dynamic oscillation rheometry at pH 7
and 12% (w/w) protein. For sample
temperatures below 60 Degrees Celcius, rheological properties were found to be completely
reversible. For sample temperatures
above 60 Degrees Celcius the rheological properties of the gels changed irreversibly. For temperatures below this transition
region, the interrelated effects of sample temperature and measurement on the
absolute value of the shear modulus and relative viscoelasticity were
completely correlated.
Similar rheological measurements
for rennetted milk gels have found that the cold storage of milk before gel
formation weakens gel strength. A
working hypothesis is that during cold storage Beta-casein is solubilized from the casein micelles and
either interferes with the enzymatic hydrolysis of k-casein or the aggregation of the micelles during
the gel formation process. In either
case, the results suggest that prolonged cold storage of milk may have a
significant effect on gel strength and consequently on cheese quality.
The Helical Screw Rheometer (HSR)
was evaluated for rheological measurements of fluid food suspensions. The HSR consists of a helical screw enclosed
in a tight fitting cylinder. Viscosity
measurements of standard Newtonian fluids using the HSR were found to correlate
well to measurements on a rotational rheometer with cone and plate
fixtures. Non-Newtonian food
suspensions were also measured and analyzed with a power law model. Although the rate indexes n were in
reasonable agreement, the consistency coefficients m from the HSR were 13 to
23% lower as compared to results with the cone and plate fixtures on the
rotational rheometer. These results
suggest that the HSR could be used as an on-line viscometer in processing
environments where the measurement of viscosity is often a critical control
parameter for product quality.
RECENT SIGNIFICANT FINDINGS/ACCOMPLISHMENTS
SELECTED PUBLICATIONS:
PROFESSIONAL AFFILIATIONS:
American Institute of Chemical Engineers
American Chemical Society
Institute of Food Technologists
HONORS AND AWARDS:
National Merit Scholar, 1980-1984
NSF Young Investigator Award, 1993-1998
Procter & Gamble Young Investigator Award, 1994-1999
Outstanding Teacher Award, Chemical Engineering, University of California, Davis, 1998
