Characterization of physicochemical and rheological changes in corn flake processing
Abstract
The ultimate goal of this research was to develop a fundamental understanding of the corn flaking process and determine how processing conditions (i.e. tempering) affect the final product in terms of quality and starch fragmentation. With the assistance of a cereal company, studies were designed and performed to show the effects of cooking, drying, tempering, and milling on corn flaking grits during the corn flaking process. The development, application, and verification of a novel rheometry device to monitor and measure the mechanical properties of a single corn grit during the processes of cooking, drying, and tempering was used in this study. It was proposed from this work that this method may find suitable applications in industrial online/at-line systems due to its non-invasiveness, little to no modification of testing samples, and its ability to obtain quick and instantaneous measurements. The process of tempering corn flaking grits was more thoroughly investigated with the novel rheometry device and mechanisms were identified that were shown to promote a reorganization of structure after gelatinization. State diagrams of the viscoelastic properties of corn flaking grits during the process of tempering were obtained and shown to be affected by moisture, temperature, and time. Tempered grit rheology was shown to greatly influence the milling process in terms of flake thickness, process-induced fragmentation, and glass transition temperatures (Tg) of the milled flakes prior to toasting. A relationship with Tg and overall product quality in terms of percent water uptake of the cereals and sensory quality characteristics was also obtained. The quality of the finished food was assessed through sensory evaluations, as well as, a new developed procedure related to the concept/measurement of bowl-life. Additionally, the effect of storage and the mechanisms involved in the aging of toasted flakes were investigated.
Degree
Ph.D.
Advisors
Campanella, Purdue University.
Subject Area
Food science|Agricultural engineering
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