Esterification, of pectins

Data on the pectin content of the initial material (AUAC and DE) is presented in Table 1. It is evident that the main difference between the two lots of oranges was in their anhydrouronic acid content. Observations from previous research (1) were confirmed that microwave heating of the fresh material ensured better drying conditions by inactivating pectolitic enzymes, particularly pectinesterase. Thus a better retention of the degree of esterification of pectin was ensured. 

Work at the Eastern Regional Research Laboratory (35) was concerned with the de-esterification of pectin by two alternative schemes acid and enzyme. It was found that whereas enzyme de-esterification of apple pomace pectin required several minutes, acid de-esterification took 1 to 2 days. Although 40° to 50° C. was optimum for both acid and enzyme de-esterification. 

Phinney et al. [Ill] investigated the application of citrus pectins, as chiral selectors, to enantiomer separations in capillary electrophoresis. Successful enantioreso-lution of primaquine and other antimalarials, was achieved by utilizing potassium polypectate as the chiral selector. Changes in pH, chiral additive concentration, and capillary type were studied in relation to chiral resolution. The effect of degree of esterification of pectin materials on chiral recognition was evaluated. 

The group of pectic enzymes includes pectinesterase, which catalyzes the de-esterification of pectin, and depolymerizing enzymes which catalyze the splitting of glycosidic a-( 1 — 4) bonds of the D-galacturonan chain of the pectin molecule. 

The original test for the presence of pectinesterase was the formation of gel after an enzymic de-esterification of pectin in the presence of Ca2+ ions. This behavior was observed by Fremy107 more than 100 years ago, after he found the presence of pectase in carrots. 

Qualitative tests for the presence of pectinesterase, based on a color change of such indicators as Bromothymol Blue or Bromocresol Green, after de-esterification of pectin, are simple and very useful these tests are used as drop tests when checking chromatographic columns85,97 100 or for a qualitative assay of pectinesterase in culture filtrates, using the cup-plate method.113... 

Fig. 9.— Influence162 of Degree of Esterification of Pectin Substrate on V and 1 IKm of Pectate Lyase of Arthobacter, strain 547.

Schultz, T.H. 1965b. Determination of the degree of esterification of pectin. In Methods in Carbohydrate Chemistry, Vol. 5 (R.L. Whistler, ed.) pp. 189-194. Academic Press, New York. 

PEI and PEII did not completely de-esterify pectins with DE ranging from 95.6 to 32%. The lower the initial DE of the substrate, the lower was the DE of the final product of the reaction. However, none of the products from PEI and PEII reactions with pectins (DE 95.6 to 32%) had DEs of less than 11%. Solms and Deuel (38) earlier noted that 11% DE was the lower limit for de-esterification of pectin by PE. 

N. O. Maness, J. D. Ryan, and A. J. Mort, Determination of the degree of methyl esterification of pectins in small samples by selective reduction of esterified galacturonic acid to galactose, Anal. Biochem., 185 (1990) 346-352. 

Figure 3. Influence of degree of esterification of pectin substrate on maximal velocity (relative Vmax, %) of PG from Kluvveromvces fragilis, of endopectate lyases from Pseudomonas fluorescens (PAL I), Bacillus polymvxa (PAL II) and Arthrobacter 37D (PAL III) and of endo pectin lyase from Aspergillus niger (PL). For PL also the effect on the Michaelis-Menten constant (1/Km) is shown (PL x-x).

Sungthongjeen S, Sriamornsak P, Pitaksuteepong T, et al. Effect of degree of esterification of pectin and calcium amount on drug release from pectin-based matrix tablets. AAPS Pharm Sci Tech... 

Pectic acid is rather resistant to alkaline degradation, but pectin is not. The alkaline de-esterification of pectin in oxygen-free solutions is accom-... 

Table I. Effect of Degree of Esterification of Pectin on the Shear Modulus of...

Table 4. Effect of high pressure and heat treatments on changes in the degree of esterification of pectin in guava juice ...

Table 3.1 Percentage yield and degree of esterification of pectin obtained from various sources.

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