IFT sag method

For many years, the pectin industry has measured gel strength using the IFT-SAG method (Cox and Higby, 1944 IFT, 1959). In this method, pectin gels are prepared under standard conditions, and the amount of sag under the force of gravity is measured with a micrometer called a Ridgelimeter. The method is precise, reproducible and simple to operate, but it is incapable of a comprehensive evaluation of gel structure. 

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... 

IFT-SAG. In the IFT-SAG method, a standardized amount of sugar Is cooked with a test amount of pectin. The mixture Is poured Into a 7.94 cm height jelly glass which contains an excess of acid and allowed to gel for 18 to 24 hours. The jelly Is demolded and the amount of sag under the force of gravity Is measured with a special micrometer called a Rldgellmeter. 

The IFT-SAG method did not win unanimous support at Its Inception because test conditions do not stimulate how pectins are used In commercial practice. The test pH of 2.2 Is ten times more acid than the commercial jelly pH of 3.2 and Is well below the maximum gel strength pH (7, 36, 53, 62). The test Is based on a water jelly which does not account for the naturally occurring buffers and salts In fruit juice. The low gravity compression rate... 

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. 

The Ridgelimeter used for the IFT SAG Method is excellent from the point of simplicity and sturdiness. Other methods, however, have been developed with a higher degree of sophistication, but at the same time, they are also more complicated and subject to mechanical errors. 

Limitations of the IFT SAG method with respect to pH have been demonstrated. Similar limitations have been reported by other laboratories (2). Since the Herbstreith Pectinometer and the Voland Stevens Texture Analyser have been developed recently, it could be of interest to see how the jelly characteristics measured by these Instruments correspond to the official results as expressed by IFT SAG. 

From the beginning the IFT Committee realized that their SAG Method was a compromise between conflicting interests. Furthermore the Committee realized that no one test could measure all parameters of pectin performance in a jelly. 

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. 

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