ARS | Publication request: Functional analysis of block deesterified citrus pectins

Submitted to: Florida State Horticultural Society Meeting
Publication Type: Abstract Only
Publication Acceptance Date: March 15, 2007
Publication Date: May 10, 2007
Citation: Luzio, G., Cameron, R. 2007. Functional analysis of block deesterified citrus pectins. Florida State Horticultural Society Meeting. Abstract No. HP21.

Technical Abstract: After removal of soluble sugars and other compounds by washing, citrus peel is largely composed of pectin, cellulose and hemicellulose. In order to utilize the greatest amount of citrus peel product, it would appear reasonable that one or all three of these polysaccharides be converted to a useful material. One of the components, pectin is relatively easy to modify using enzymes and has great utility in the food industry and other applications. Thus it appears reasonable to focus on the use of pectin for the maximum utilization of fruit peel for new products from peel. During deesterification, the ester groups on the pectin can be removed in a random or blockwise manner with enzymes. When the ester groups are removed in a sequential manner, they are referred to as being deesterified in a "blockwise manner," as blocks of unesterified galacturonic acid units are created. The unesterified galacturonic acid units formed by blockwise deesterification are highly reactive to divalent cations such as calcium. Pectins having such blocks of unesterified galacturonic acid are said to be "calcium sensitive." Calcium sensitivity affects rheology, such as yield stress, and is an important functional property of pectins for use in applications which require suspension, metal ion binding or water absorption. Yield stress behavior can be important for pulp stabilization in citrus drinks while providing low viscosity for acceptable mouth feel. Pectins, with a high degree of esterification (DE) were demethylated with a monocomponent preparation of a pectin methylesterase PME isolated form citrus fruit tissue and with an unpurified fraction of PME from papaya to a DE of 55%. Rheology and calcium sensitivity measurements on one of these pectins had indicated that both block number and block size needed to be considered for crosslinking with calcium ion. The calcium sensitive properties of pectins are typically measured by calcium sensitive pectin ratio (CSPR) assay and a new improved assay was developed and reported herein to facilitate analysis. Comparisons are made for properties of rheology and CSPR for pectins which have been deesterified with different enzyme preparations.