Relationship of the Strength of High Solids Pectin Gels to the Concentration and Jelly-forming Capacity of the Pectin Present

Abstract

IN 1940 Hinton¹ put forward a theory which was capable of explaining quantitatively many of the phenomena associated with the formation of high solids pectin gels. More recently, the assumptions on which Hinton based his theory have been criticized and an alternative explanation suggested which is more in keeping with current theories of the properties of macromolecules². Neglecting the small variation in the degree of dissociation of pectin with concentration^1,3, for a given pectin in a gel of specified soluble solids content and pH, both theories indicate a linear relationship between gel strength and pectin concentration. However, a review of a number of the published curves relating the gel strength and the pectin concentration shows that when the strength is measured within the elastic limits of the gel and is expressed in units proportional to an elastic modulus, in each case the curve obtained is convex to the pectin concentration axis^4–11 (gel strengths measured by means of the ridgelimeter^9–11 may be converted from percentage sag to shear moduli by means of the curve given by Owens and Maclay¹²). Similar curves have been obtained by some workers measuring the breaking strengths of the gels^13–15, although in some instances a linear relationship was found^16,17.