|Chung, Okkyung - RETIRED-USDA|
|Park, Seok Ho|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: April 21, 2008
Publication Date: January 1, 2009
Citation: Chung, O.K., Ohm, J., Ram, M.S., Park, S. 2009. Wheat Lipids. In: Khan, K. and Shewry, P.R., editors. Wheat Chemistry and Technology. 4th edition. St. Paul, Minnesota: AACC International, Inc. p. 363-390. Technical Abstract: This article is a chapter of a book entitled “Wheat: Chemistry and Technology”, the 4th edition, K. Khan and P.R. Shewry (eds.), to be published in 2007 following the 3rd edition, Y. Pomeranz (ed.), published in 1988 by AACC International Inc., St. Paul, MN. The chapter covers the subject area of wheat and wheat flour lipids. Lipids in wheat or wheat flour are a minor constituent, and yet they play major roles in wheat production, storage, processing, products, nutrition, and consumer acceptance of finished goods. Many researchers have paid close attention to the area of quantification and composition of lipids in wheat kernels, their structural parts as well as the processed product, i.e., milled flour. Especially, the role of lipids in wheat products’ quality has been studied extensively using the techniques of defatting flour and reconstituting the removed lipids back to the defatted flours in the mid 1960’s to the 1980’s. Those research efforts were mainly concentrated in “free lipids,” easily extractable lipids with relatively nonpolar solvents, which would not disrupt the bonding between lipids and other constituents such as proteins or others. The roles of free lipids in breadmaking have been well documented, and found that polar lipids, especially glycolipids, in free lipids are bread loaf volume enhancers. Then, in the late 1970’s to the beginning of the 1980’s, most lipid research workers referred to wheat or flour lipids as just non-starch lipids, since starch lipids present inside starch granules cannot be extracted by any solvent at the ambient temperature. Thus, the terminology of wheat lipids or flour lipids is greatly dependent on the extraction conditions, including the solvents, extracting temperature, moisture contents, or extraction and quantification methodology. In addition, as lipids are unevenly distributed in wheat structural parts, lipid content and compositions are also affected by milling practice, i.e. flour extraction rate, various milled stream, etc. Furthermore, the wheat growing-environment, as well as the genetic background, results in variations in lipid contents and composition. A very complex subject is dealt with in this chapter. It begins with an overview: brief nomenclature, classification, and chemical structures of simple and complex lipids; and recent advances made in lipid extraction and quantification methodologies, such as supercritical fluid extraction (SFE), solid phase extraction (SPE), accelerated solvent extraction (ASE), near infrared (NIR) spectroscopy, etc. Then, the chapter was followed by lipid content and composition in various wheat fractions and the comparison of lipids in different wheat classes and varieties within the same classes. The last major section included functional roles of wheat lipids including: the nutritional roles; roles as wheat quality index; and the functional roles in processing and final products quality; i.e. bread-, cookie-, cake-, spaghetti-, noodle-, and extruded products. The main emphasis was on the breadmaking area with extensive reviews on defatting and reconstituting studies, wheat lipid variations vs. breadmaking quality, interactions of wheat lipids and proteins in breadmaking, and multiple interactions with shortening in bread formulas. It ended with suggested future works and about 250 reference citations, of which about 60% (one-half since 2000) was published after the 3rd edition of the book “Wheat: Chemistry and Technology,” which was printed in 1988.