Abstract/Details

A new insight into the phase transition processes of food starches


2006 2006

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Abstract (summary)

Starch displays a unique thermal behavior, when heated in water, known as gelatinization. None of the theories documented in literature adequately explain the exact mechanisms of structural changes that occur in starch granules during gelatinization process. In this study, seven native starches, three modified starches, three resistant starches, and starch isolated from alkaline-cooked corn masa were examined to determine their phase transition behavior using light microscopy, scanning electron microscopy, differential scanning calorimetry, high-performance size exclusion chromatography, and X-ray diffraction. Starch polymers rearrange or reorganize at temperatures below the onset of the differential scanning calorimetric endotherm. This polymer rearrangement and subsequent granular restructuring that occur before complete granular disintegration is different from annealing. Analysis of modified starches revealed that cross-linking restricted or delayed these internal structural changes, and hydroxypropylation prevented the granular crystalline structure to a certain extent during phase transition. The resistant starches were more resistant to structural changes than other starches within the temperature range studied. The results concluded that starch gelatinization process is different from previously hypothesized direct order-to-disorder phase transition. It was found that starch granules heated in excess water undergo structural reorganization in the amorphous region before complete phase transition occurs. The nature and extent of these structural changes depend on starch type and the intensity of the hydrothermal treatment.

The phase transition associated granular structural changes also occur in starch containing foods. Alkaline cooked corn masa was used as a model system to study starch phase transition in food. The proteolytic enzyme thermolysin (EC 3.4.24.27) was used successfully to isolate starch from alkaline cooked corn masa. The isolated starch was analyzed to determine the nature and degree of starch phase transition that occurred during the masa production process. It was found that starch granules could morphologically remain intact while losing their structural order when they underwent phase transition during alkaline cooking while "trapped" in the protein matrices of masa.

Indexing (details)


Subject
Food science
Classification
0359: Food science
Identifier / keyword
Biological sciences; Food starches; Gelatinization; Phase transition; Starches
Title
A new insight into the phase transition processes of food starches
Author
Ratnayake, R. M. Wajira Srinanda
Number of pages
222
Publication year
2006
Degree date
2006
School code
0138
Source
DAI-B 67/02, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9780542562679
Advisor
Jackson, David S.
University/institution
The University of Nebraska - Lincoln
University location
United States -- Nebraska
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3208078
ProQuest document ID
305276426
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/305276426
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