Pectin grading methods

Jelly Manufacturer s Needs. During the first half of this century, there was no uniform method to measure the ability of pectin to form a gel. Consequently, jelly manufacturers had to constantly adjust the amount of pectin used per batch of jelly with little assurance that the appearance and texture of the finished product would be of a high quality. After the adoption of the Institute of Food Technologist s (IFT-SAG) method in 1959, all pectins were standardized on their ability to form a gel. This method has been used by pectin and jelly manufacturers for more than 25 years. The details are discussed later in this chapter. Although the IFT-SAG method has been the pectin grading standard, it has some... 

Nondestructive vs. Destructive Tests. The pectin grade depends somewhat on the evaluation method (61). Gel strength Instrumentation may be nondestructive which measures the elastic properties of a gel, or destructive which measures the Inelastic or breaking strength of a gel. A major pectin producer unsuccessfully tried several Instruments and methods for more than 20 years to measure both elasticity and rupture strength with a single test ( ). 

Christensen, P.E. 1953. Methods of grading pectin in relation to the molecular weight (Intrinsic Viscosity) of pectin, Pectin Symposium of the New York Preservers Association, pp. 163-172. 

Cox, R.E. and Higby, R.H. 1944. An improved method for determining the grade of commercial pectins, Food Manuf, 19 199-202. 

After many years of discussion over the standard jelly for the jelly grade determination, work on a standard method was undertaken by a committee of the IFT. The committee worked for several years on pectin standardization. They selected the Exchange Ridgelimeter as the standard Instrument to measure jelly SAG because it was compact, inexpensive, easy to use, and it also gave reproducible results. 

Parallel to the work in the U.S., researchers in England also were working on a method to grade pectin. Simultaneously a method was published which specified soluble solids in the test jelly of 70.5% and a pH of 3.10 (4). 

In spite of the work done in England, the IFT SAG Method (sometimes called US SAG) over the years has become the most widely accepted method for the grading of commercial pectin all over the world. 

In Table I, the conditions of time, temperature, pH, and yields of the calcium pectinates prepared by the simultaneous acid-extraction and demethylation of pectin from apple pomace are presented, as well as the evaluation of the acid-alcohol treated calcium pectinates as to calcium pectate content, methoxyl content (expressed on the basis of 100% calcium pectate), relative viscosity, grade, and optimum pH. These data were obtained by methods described below in the order that they appear in the table. 

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