A shortcourse entitled Rheological Analysis ofFoods: Theory and Practice was conducted by theNorth Carolina State University Department ofFood Science in Raleigh, North Carolina duringMay 30 – June 2, 2000. This was the sixth foodrheology shortcourse hosted by North CarolinaState University and was sponsored in part by theSoutheast Dairy Foods Research Center. Generallectures, hands-on laboratory exercises, as wellas group discussions of practical applications andcase studies were used to convey the funda-mental concepts of food rheology.

The shortcourse instruction was provided bya group of university and industry food rheologyexperts. C. R. Daubert, E. A. Foegeding, and T. C.Lanier of North Carolina State University and M.A. Drake of Mississippi State University werejoined by E. K. Chamberlain of Kraft Foods, Inc. toprovide lectures, instruct laboratory exercises,and lead group discussions.

The course was directed towards basicresearch and product development scientists inindustry, academia, and government concernedwith the rheological and textural analysis offoods. Seventeen representatives of industry andacedemia, along with several graduate studentsfrom North Carolina State University, participat-ed in the shortcourse. Representatives of foodprocessors, hydrocolloid companies, ingredientsuppliers, and research institutions attended theshort course to learn how rheological propertiesrelate to food quality, stability, process design,and formulation.

The shortcourse attendees arrived in Raleighon Tuesday evening. In conjunction with regis-tration, a welcome and social period was held. Theparticipants received their course materials and

had a chance to meet the instructors and fellowparticipants. The course began Wednesday morn-ing with an introduction and discussion of thecourse objectives by C. R. Daubert and E. A.Foegeding. The first lecture, by E. A. Foegeding,provided an overview of the analysis of foods fromthe perspectives of biological, polymer, and mater-ial sciences. T. C. Lanier then presented a lectureexplaining fundamental and empirical rheologi-cal properties of foods. Following the first two lec-tures, a group discussion answered questions anddiscussed practical situations with the partici-pants. From this discussion, the participants real-ized that although empirical measurements havea place in industry, the mechanisms governingflow behavior are better understood via funda-mental rheological techniques. C. R. Daubert gavethe last lecture of the morning, presenting theprinciples of steady shear methods for fluids anda description of various fluid behaviors encoun-tered in food rheology.

The afternoon session began with a fluidrheology laboratory, where the participantslearned to determine Newtonian viscosity ofcorn oil, apparent viscosity of salad dressing,yield stress of ketchup, and temperature-depen-dent viscosity of honey. The laboratory alsodemonstrated the advantages and disadvan-tages of different viscometers, rheometers, andrheological attachments. Following the labora-tory, E. K. Chamberlain gave a lecture on the prac-tical applications of fluid rheograms anddescribed particular industry cases where rheo-logical solutions have been used. For example, acase study was discussed that revealed theimportance of temperature control in rheologi-cal measurements. In the last lecture of the after-

146 Applied RheologyMay/June 2000

A Recap of Rheological Analysis of Foods: Theory and Practice

Raleigh, North Carolina, USAMay 30th - June 2nd, 2000

ConferenceReport II

Figure 1 (left): C.R. Daubert discusses

geometries used in steadyshear fluid rheology.

Figure 2: E.A Foegeding and P.J. Luck

explain calculations used forketchup yield stress

determination.

Bilder 14.02.2001 10:11 Uhr Seite 146

This is an extract of the complete reprint-pdf, available at the Applied Rheology websitehttp://www.appliedrheology.org

This is an extract of the complete reprint-pdf, available at the Applied Rheology websitehttp://www.appliedrheology.org

noon, C. R. Daubert presented the principles oflarge strain rheology of solids, including adetailed analysis of torsion testing. After a recapof the first day’s topics, the participants had din-ner at Raleigh’s famous Angus Barn.

The second day started with laboratory exer-cises about compression and torsion fracture.The participants were introduced to compressiontesting of hotdogs, torsion testing of hotdogsand cheese, and failure characterization ofcheese using the vane method. The concept of atexture map was introduced to relate the impor-tance of stress and strain of materials at fracture.After the laboratory discussion, the morning con-tinued with two lectures. T. C. Lanier provided atalk on how fundamental fracture data can beused to optimize product development andingredient formulation. C. R. Daubert thenexplained the concept of viscoelasticity and thebasics of small amplitude oscillatory rheology.

Thursday afternoon started with a lectureon small strain testing of viscoelastic food mater-ials. The focus was on the fundamentals ofdynamic shear, step strain, creep and recoveryexperiments, and results interpretation. A vis-coelasticity laboratory was then offered todemonstrate the principles from the lecture. Theparticipants examined low and full fat cheesesusing a stress controlled rheometer to performcreep recovery tests and used a strain controlledrheometer to conduct a relaxation experiment.In addition, the participants learned to examinethe mechanical spectra of foods. E. A. Foegedingdiscussed the application of small strain experi-ments and how these tests may be used to studyand quantify the structure and behavior of foodsystems. Particular attention was given to the

147Applied RheologyMay/June 2000

subject of gel point determination. E. A. Foeged-ing discussed with the participants the difficultyin finding the gel point for protein gel systems,and techniques used for gel point determination.The last lecture of the afternoon was given by M.A. Drake. Dr. Drake described the aspects of sen-sory analysis and how it can be used to evaluatethe textural attributes of foods. The evening con-cluded with dinner and a comedy performanceat Charlie Goodnight’s Comedy Club.

The final day of the shortcourse started witha sensory analysis laboratory in which M. A. Drakeexplained the aspects of three types of sensoryanalysis scales. The class then applied these scalesto evaluate rate and smoothness of melt forchocolate chips, bite-pull and toothstick oflicorice, as well as firmness and cohesiveness ofcheeses. E. A. Foegeding offered the final lectureof the course, speaking about correlationsbetween sensory and rheological data. C. R.Daubert provided a review of the course and pre-sented the participants with a NCSU rheologyshortcourse t-shirt and a certificate of comple-tion.

The rheology shortcourse will be offeredagain in May 2001. For more information visitwww4.ncsu.edu/unity/users/c/cdaubert/www/short_course/ or contact C.R. Daubert atchris_daubert@ncsu.edu.

J. J. Resch and C. R. DaubertNorth Carolina State UniversityDepartment of Food ScienceRaleigh, NC 27695/7624USAx1.919.513.2092chris_daubert@ncsu.edu

Figure 3 (left): M.A. Drake prepares theparticipants to evaluate the sensory texture of chocolate chips.

Figure 4: Shortcourse participantsand instructors gather for a group photograph.

Bilder 14.02.2001 10:11 Uhr Seite 147

This is an extract of the complete reprint-pdf, available at the Applied Rheology websitehttp://www.appliedrheology.org

This is an extract of the complete reprint-pdf, available at the Applied Rheology websitehttp://www.appliedrheology.org