Submitted to: Subtropical Technology Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: September 15, 2007
Publication Date: October 18, 2007
Citation: Luzio, G.A., Cameron, R.G. 2007. Suspension properties of pectins deesterified using pectin methylesterase. Subtropical Technology Conference Proceedings. 58:20. 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 and crosslink to form gels. Pectins having such blocks of unesterified galacturonic acid are said to be "calcium sensitive." Calcium sensitivity affects rheology, such as yield stress and storage modulus and is an important functional property of pectins in suspension applications such as pulp suspension in citrus drinks. 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. More recent work indicates that calcium/pectin ratios are important for optimizing storage modulus and recovery of storage modulus. This data together with a discussion of requirement for recovery of storage modulus for suspension will be discussed.