Factors Influencing Gelation with Pectin

Abstract

Gelation studies have sought to establish the background for a theory of pectin gel formation. Factors investigated that control the properties of pectin gels were: pH, degree of esterification, effect of acylation, temperature, and molecular weight. Elastic moduli of pectin gels decrease as the degree of esterification or of acylation decreases; they remain practically constant from 0° to 50° C. and decrease rapidly with further increase in temperature; and they are controlled by number average molecular weight. Breaking strength is controlled by weight average molecular weight. Although a complete picture of pectin gel formation cannot be drawn until stress relaxation data are available, association of pectin may begin with the ester groups but hydrogen bonding may account for the strength of the gels. Instead of point-to-point contacts between molecules, there may be crystalline regions involving several galacturonide units. This hypothesis accounts for the effect of acylation, setting temperature, and the low-temperature coefficient of the shear modulus of pectin gels.Pectin, a long-chain polymeric galacturonide partly esterified with methanol, has been used in the preparation of jellies and similar food products for over a hundred years. The mechanism by which it forms gels is not clearly understood and more information on the factors influencing pectin gel formation is required to develop a more exact theory of gelation.The first coherent hypothesis of pectin gel formation and elucidation of the importance of each component were made about 20 years ago by Olsen (15). Sugar functions as the dehydrating agent. 2. Acid functions by reducing the negative charge on the pectin, thus permitting coalescence.3. Dehydration of pectin requires time to come to equilibrium (to account for slow setting or low temperature of setting of certain pectin gels). The rate of dehydration and precipitation increases directly as hydrogen ion concentration increases.5. The maximum jelly strength is reached when the system reaches equilibrium.6. Any component added to a pectin jelly system, including salts which cause a change in the ultimate jelly strength of that system, may function by changing the rate of gelation, by affecting the position of the ultimate equilibrium of the system, or by a combination of these effects.The question whether sugar acts solely as a dehydrating agent or enters the framework of the gel structure has been raised (29), but the fact that glycerol at the same weight concentration as sucrose forms equally strong gels with pectin (SI) may indicate that the number of hydrophyllic groups is the more important factor. The marked increase in viscosity of sugar solutions as the concentration of sugar is increased above 45% probably reinforces the rheological properties of pectin gels, but there is no direct evidence that sugar molecules actually enter the gel structure. Unpublished work at this laboratory has revealed that more than 99% of the sugar in a gel can be extracted with ethanol without a change in dim...

Preliminary Evaluation of 3D Printed Chitosan/Pectin Constructs for Biomedical Applications

“…According to Owens et al, while heating PEC solutions, in the temperature range between 0 °C to 50 °C, there is no detection of thickening of the solution. Contrarily, during cooling, hydrogen bonding is enhanced, providing strong gels [ 41 ]. The behavior of PEC is in accordance with our everyday experience.…”

Histological and Histochemical Changes in Developing and Ripening Peaches. II. The Cell Walls and Pectins

“…Molecular chain length, spacial configurations and complexity of side chain structure influence the solubility and gelling properties of pectins (Bonner, 1950;Deuel and Solms, 1954). It has been found that fuIIy esterified apple pectin can form gels in a 60% solids medium (approximately as in cell walls) which are firmer than those formed with the original pectin; also that increased esterification in certain ranges appears to be associated with decreased solubility of the pectin (Owens et al 1954). It is noteworthy here that the highest degree of esterification was found in both clingstone and freestone peaches at early ripening to hard ripe stages before and after which degree of pectin esterification was appreciably lower.…”

Solidification of concentrated pea protein–pectin mixtures as potential binder

“…Therefore, it was structurally weaker than the mixture with pea protein and apple pectin, which is most likely due to the lower molecular weight of the sugar beet pectin (45.0 kDa) compared with the apple pectin (64.6 kDa). 28 All the different control samples exhibited viscoelastic properties (tan ⊐ = 0.67-0.94) that facilitated a good balance of adhesion and cohesion. Therefore, all control samples were sticky, showing a cohesive failure (Table 1), and thus were generally suitable as food glues.…”