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Keywords:

  • jam;
  • sugar content;
  • pectin methyl esterase;
  • transacylation

Abstract

BACKGROUND: Pectin methyl esterase (PME) has been postulated to catalyse the transacylation reaction between pectin molecules. The present study aimed to prove the occurrence of this reaction. The feasibility of applying PME-catalysed transacylation between high-methoxy pectin molecules in making fruit jam with reduced sugar content was also investigated.

RESULTS: PME treatment increased the turbidity and particle size in pectin solution and the molecular weight of pectin, while it decreased the number of methoxy ester linkages and the intensity of the CH3 absorption peak in the Fourier transform infrared spectrum without changes in the number of total ester linkages in pectin molecules. These findings support the occurrence of PME-catalysed transacylation between pectin molecules. Higher values of hardness, gumminess and chewiness were found in a jam containing PME-treated citrus pectin (10 g L−1) and sugar (350 g L−1) as compared with either a jam containing untreated citrus pectin (10 g L−1) and sugar (350 g L−1) or strawberry jam containing pectin (10 g L−1) from the fruit and sugar (650 g L−1).

CONCLUSION: The demand for sugar in jam making can be greatly reduced by the use of PME-treated high-methoxy pectin. Copyright © 2012 Society of Chemical Industry