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Degradation kinetics of beetroot pigment encapsulated in polymeric matrices
Author(s) -
Serris George S,
Biliaderis Costas G
Publication year - 2001
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.864
Subject(s) - degradation (telecommunications) , kinetics , betanin , betalain , glass transition , chemistry , maltodextrin , polymer , pigment , reaction rate constant , absorbance , sorption , chemical engineering , materials science , organic chemistry , adsorption , chromatography , telecommunications , physics , quantum mechanics , computer science , engineering , spray drying
Kinetic studies on the degradation of water‐soluble beetroot pigment, mainly consisting of the betalain betanin, encapsulated in three different matrices (pullulan and two maltodextrin samples differing in their molecular weight) were carried out under various water activity ( a w = 0.23, 0.43, 0.64, 0.75 and 0.84) and temperature (30, 40 and 50 °C) conditions. The water sorption behaviour of these materials was also examined. Degradation of the pigment was monitored by absorbance measurements at 537 nm (λ max of betanin). The highest values of the rate constants for degradation were observed at an intermediate water activity level ( a w = 0.64) for all matrices and all three storage temperatures examined. An attempt to relate the degradation kinetics to the molecular mobility of the wall material was not successful. Pigment losses were observed even at temperatures below the glass transition temperature ( T g ) of the polymeric matrices, although degradation was largely slowed down in the glassy state. In the vicinity of the T g zone, where all polymers go through a glass → rubber transition, there was not a distinct change in the reaction rate, which could reflect the pronounced changes in molecular mobility of the wall material. In fact, some of the lower degradation rates were observed mostly under conditions where the matrices were fully plasticised (ie rubbery) and ‘collapsed’, implying that the degradation kinetics is not governed by factors related only to the physical state of the polymeric wall material. © 2001 Society of Chemical Industry