Submitted to: Journal of Agriculture and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 13, 2007
Publication Date: January 10, 2008
Citation: Fishman, M., Chau, H.K., Cooke, P.H., Hotchkiss, A.T. 2008. Global structure of microwave-assisted flash extracted sugar beet pectin. 2008. Journal of Agriculture and Food Chemistry 56(4):1471-1478. 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 sugar beet pectin in and from solution. Pectin is a polysaccharide found in sugar beet pulp, the remains from the extraction of sugar from sugar beets. In this work we developed a method of extracting pectin from pulp by heating it for 3 minutes at 60 'C rather than an hour or longer at 80 'C as done conventionally. Physical characterization revealed that we had extracted a higher quality pectin as indicated by its solution viscosity and molar mass than had been extracted heretofore from fresh sugar beet pulp. This material has potential to be a controlled release matrix for pharmaceuticals or as an emulsifier in foods or industrial products, 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, flash extracted pectins isolated from fresh sugar beet pulp. The objective was to minimize the disassembly and possibly the degradation of pectin molecules during extraction. We have characterized these pectins by HPSEC with light scattering, viscometric detection, and by atomic force microscopy (AFM). Generally 15 micrometer size column packing gave higher intrinsic viscosity, molar mass and polydispersity than 8 micrometer packing. Samples analyzed with 15 micrometer packing gave weight average molar masses that ranged from 532,000-1.2 million Daltons, radius of gyration from about 35-51 nm, polydispersity from 1.78-2.58 , intrinsic viscosity from about 3.00-4.30 dL/g and recovery ranged from 8.40-14.81% of dry weight. Chromatography revealed that a bimodal distribution of high molar mass spherical particles and lower molar mass coils was obtained. AFM images of pectin corroborated this conclusion and further revealed that these strands and spherical particles were integrated into networks. We have demonstrated that MAE of sugar beet pulp under moderate pressure and at relatively low temperature could extract under acid conditions high molar mass, moderate viscosity pectin in minutes rather than hours as is required by conventional heating.