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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPACT OF EARLY DIETARY FACTORS ON CHILD DEVELOPMENT AND HEALTH Title: Influence of extrusion processing on procyanidin composition and total anthocyanin contents of blueberry pomace

Authors
item Khanal, Ramesh -
item Howard, Luke -
item Brownmiller, C -
item Prior, Ronald

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 31, 2008
Publication Date: March 15, 2009
Citation: Khanal, R.C., Howard, L.R., Brownmiller, C.R., Prior, R.L. 2009. Influence of extrusion processing on procyanidin composition and total anthocyanin contents of blueberry pomace. Journal of Food Science. 74(2):H52-H58.

Interpretive Summary: Blueberry juice processing by-products are a rich source of procyanidins, which comprise a group of compounds shown to possess numerous health benefits including, protection against coronary heart disease, type II diabetes, and obesity. Most of the procyanidins present in blueberry pomace, however, are large molecular weight compounds that are poorly absorbed and show weak bioactivity compared to the smaller molecular weight compounds. The objective of our study was to identify optimal extrusion variables to enhance the contents of smaller compounds at the expense of large molecular weight procyanidins. Extrusion of blueberry pomace increased the smaller compounds. The highest monomer content, obtained at 180 deg C and 150 rpm screw speed, was 84% higher than the non-extruded control. Significantly higher levels of dimer and trimer contents were also obtained under these conditions. Increases in monomer, dimer, and trimer contents apparently were the result of reduced polymer contents. Extrusion processing reduced total anthocyanins. These results demonstrate that extrusion processing can be used to increase bioavailable forms of procyanidins in blueberry pomace.

Technical Abstract: Blueberry juice processing by-products are a rich source of procyanidins, which comprise a group of compounds shown to possess numerous health benefits including, protection against coronary heart disease, type II diabetes, and obesity. Most of the procyanidins present in blueberry pomace, however, are large molecular weight compounds that are poorly absorbed and show weak bioactivity compared to the smaller molecular weight monomers and dimers. The objective of our study was to identify optimal extrusion variables to enhance the contents of monomers and dimers at the expense of large molecular weight procyanidin oligomers and polymers. Extrusion variables temperature (160 and 180 deg C) and screw speed (150 and 200 rpm) were tested using mixtures of blueberry pomace with decorticated white sorghum flour at a ratio of 30:70 and 45% moisture content. Extrudates were analyzed for procyanidin composition and total anthocyanin content. Extrusion of blueberry pomace increased the monomer, dimer, and trimer contents considerably at both temperature and screw speeds. The highest monomer content, obtained at 180 deg C and 150 rpm screw speed, was 84% higher than the non-extruded control. Significantly higher levels of dimer and trimer contents were also obtained under these conditions. Increases in monomer, dimer, and trimer contents apparently were the result of reduced polymer contents, which was approx. 40% lower for samples extruded at 180 deg C temperature and 150 rpm screw speed. Extrusion processing reduced total anthocyanin contents by 33 to 42% indicating that additional treatments are needed to retain the pigments. These results demonstrate that extrusion processing can be used to increase procyanidin monomer and dimers in blueberry pomace.

Last Modified: 10/23/2014