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Title: Physico-chemical characterization of alkaline soluble polysaccharides from sugar beet pulp

Author
item Fishman, Marshall
item Chau, Hoa - Rose
item Cooke, Peter
item Yadav, Madhav
item Hotchkiss, Arland

Submitted to: Food Hydrocolloids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/24/2008
Publication Date: 8/1/2009
Citation: Fishman, M., Chau, H.K., Cooke, P.H., Yadav, M.P., Hotchkiss, A.T. 2009. Physico-chemical characterization of alkaline soluble polysaccharides from sugar beet pulp. Food Hydrocolloids. 23:1554-1562.

Interpretive Summary: The need to increase utilization of low valued co-products derived from the processing of sugar beets has prompted us to investigate the structure of alkaline soluble polysaccharides (ASP) extracted from sugar beet pulp (SBP). SBP is derived from the remains of sugar beets after the extraction of sugar. In this work we developed a method of flash extracting ASP from pulp by heating it for 10 minutes at 100 deg C rather than an hour or longer as conventionally extracted ASP. Physical characterization has revealed that ASP have a structure that is distinct from another polysaccharide, pectin, which also is found in SBP. Preliminary studies have revealed that potentially, ASP are equal to or better than gum arabic as an emulsifier in food systems. This research should be of help to sugar beet growers and processors by increasing the demand and value of their by-products without increasing the cost of sugar to the consumer.

Technical Abstract: We have studied the global structure of microwave-assisted alkaline soluble polysaccharides (ASP) isolated from fresh sugar beet pulp. The objective was to minimize the disassembly and possibly the degradation of these polysaccharides during extraction. Prior to ASP microwave assisted-extraction (MAE), pectin was removed and isolated by MAE. Two sub fractions, ASP I and ASP II were isolated. ASP I had about the same ratio of anhydrogalacturonate (AGA) to neutral sugar (NS) by percentage weight (%wt) whereas ASP II had about twice as much AGA to NS by %wt. Unlike the sugar beet pectin isolated, the degree of methyl esterification of AGA in both ASP fractions was very low. Arabinose, was the most abundant neutral sugar followed by either rhamnose or galactose. High Performance Size Exclusion Chromatography with molar mass and viscometric detection revealed that both ASP fractions are about 100,000 Daltons in Mw and about 20 nm in Rgz. ASP I and ASP II had weight average intrinsic viscosities of 0.85 and 0.60 dL/g respectively and their Mark-Houwink exponents indicated that they are relatively compact in shape. Molar Mass distributions of ASP appeared to be bi-modal in shape. AFM images of ASP I revealed a bimodal distribution of small and large compact asymmetric subunits when a 0.1 microgram/mL air dried, aqueous solution was deposited on freshly cleaved mica and imaged. When the solution concentration was 25 micrograms/mL in ASP I, the subunits appeared to aggregate into skeletal structures whereas ASP II only formed compact asymmetric structures. Unlike AFM images of sugar beet pectin previously imaged, neither ASP I nor ASP II formed network structures at higher concentrations. Both ASP I and II were found to emulsify orange oil.