Grading pectins

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 ( ). 

These percentage increases in pectin grade caused by the age of jellies become smaller as the jelly pH is lowered. 

Dryden, E. C., Willaman, J. J., and Hills, C. H. 1952. Some factors affecting pectin grade of apple pomace. Food Technol. 6, 474-478. 

Citrus pectin ( Polygalacturonic Acid Methyl Ester from Citrus Fruits, Grade I ) was obtained from the Sigma Chemical Company. It had a galacturonic acid content of 89% and a degree of esterification of 57. Separate aqueous solutions of citrus pectin were freeze-dried and air-dried in deionized water. These samples were replicated with 9.8A Pt/C and backed with 148A of carbon. The replicas for these samples were picked up without a carbon support film (38). 

The proportion of sugar which pectin will form into a firm jelly determines the jetty grade of the pectin. In a jelly, jam, or marmalade, the propoitions of total solids of sugars, die pH. and the proportion and nature of the pectin used will determine the extent of jellification obtained. The use of pectin in fruit jams and related products is approved by most food regulators because the addition is believed to compensate for an incidental natural deficiency. 

Different grades of low-methoxyl pectin (Hercules, Inc., Wilmington, DE). 

Using a two-stage, single-pass module of food-grade dynamic metal oxide membrane on a sintered stainless steel support tube under a TMP of approximately 20 bars and a temperature of 50 C, Thomas et al. [1987] have successfully clarified apple puree with a juice yield of 86% and a steady state flux of about 85 L/hr-m. The quality of the clarified apple juice by this dynamic or formed-in-place membrane is excellent -sparkling looking and flavor retained. As much as 65% reduction in the total pectins has been attained. 

Rotary multitray dryer pulverized coal, pectin, penicillin, zinc sulfide, waste slude, pyrophoric zinc powder, zinc oxide pellets, calcium carbonate, boric acid, fragile cereal products, calcium chloride flakes, caffein, Inorganic fluorides, crystals melting near 100°F, prilled pitch, electronic grade phosphors, and solvent-wet organic solids... 

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. 

Citrus pectin (MexPec 1400) with the molecular weight (M.W.) of 1.8 x 105 dalton and the degree of esterification of 82 and Nisaplin (2.5% Nisin) were purchased from Danisco-Cultor (Kansas City, KS). Soybean flour protein (SFP), poly(ethylene oxide) (PEO, M.W. 900,000), and glycerol (reagent grade, < 99.5%) were obtained from Aldrich Chemical Corp. (Milwaukee, WI). 

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