Pectin orange

Pectin - Orange peel Carbon paste O.l-O.OgU1 - - 2 weeks [32]... 

Pectin Orange peei Pectin esterase Carbon paste eiectrode... 

However, since pectins can be methylesterified and/or acetylesterified, sections were treated on grid with an orange peel methylesterase to remove the methyl groups or with NaOH to remove both methyl and acetyl groups. After the enzymatic treatment, all the primary walls of most of the samples bind the... 

Castaldo, D., Lovoi, A., Quagliuolo, L., Servillo, L., Balestrieri, C. and Giovane, A. 1991. Orange juices and concentrates stabilization by a proteic inhibitor of pectin methylesterase. J. Food Sci. 56 1632-1634. 

Rouse, A.H. Atkins, C.D. 1955. Pectinesterase and pectin in commercial orange juice as determined by methods used at the Citrus Experiment Station. Florida Agric. Exper. Station Bull. 570 1-19. 

Acetyl esterase (AE) has been purified to homogeneity from orange peels. The purification steps included cation exchange chromatography and gel filtration. The enzyme has affinity for triacetin and sugar beet pectin with K, of 39 mM and of 26 mg/ml, respectively. AE has a MW of 42 kD and is a monomer. The isoelectric point is at pH > 9. 

Immuno localization using polyclonal antibodies raised against AE showed that AE was widely distributed in orange fruit but with more intensive immunological detection in the outer part of the peels e.g. albedo and flavedo and in the segments (juice vesicles). The results indicate that AE is located at the site where the major fraction of pectin is deposited. 

CTl hyperproduces pectinases on "citrus pectin " as well as on "orange peel" local substrate. 

One of the important criteria taken into account for the choice of an industrial producer strain is its ability to secrete enzymes on cheap and local substrate. Thus, we cultured our mutant as well as the Pol6 mutant on a local substrate milled "orange peel", at the same concentration as citrus pectin in the liquid medium. The results summarized on table 3 show a net difference between both strains the CTl mutant is able to produce high amounts of endo and exopectinases on both substrates whereas Pol6 is unable to hyper-produce both pectinases on "orange peel". 

Comparison of Enzymes production by CTl and Pol6 strains cultured on citrus pectin and orange peel... 

The substrates used were PC citrus pectin E orange peel G glucose, Gly gycerol, APG polygalacturonic acid. Results of two cultures (1 and 2) are presented. On ordinates, specific activities (Activity Units par p,g of extracellular proteins) are presented. Note the ordinates scale differs from one histogramme to another. 

Influence of microwave pretreatment of fresh orange peels on pectin extraction... 

Laboratory studies on the extraction of pectin from orange peels, pretreated in an electromagnetic field of hyper frequency, were carried out. The influence of intensity of microwave treatment (P ) and time on pectin yield and pectin quality was investigated. It was established that the increase of Pw and time lead to increase in the pectin yield with 180-240 % in comparison with the control. Apparently, the microwave treatment leads to a considerable increase in the soluble form of pectin, characterized by increase in the jelly strenght and in the polyuronic content. 

The aim of the present investigation is to study the influence of microwave pretreatment of fresh orange peels on the extraction time of orange pectin and the influence of the intensity and duration of microwave heating on pectin yield. 

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. 

Influence of extraction time on the yield and characteristics of pectin from fresh Navel I orange peels pretreated by microwave heating... 

Pectin is found in apples and in the white membrane that surrounds the sections of oranges, grapefruits, or other citrus fruits, as well as in several other sources. Powdered pectin made from apple cores is also available, but scientists have found that eating apples or citrus fruit has a much better effect on lowering blood cholesterol levels than eating powered pectin does. They believe eating the whole fruit is better because the body also needs vitamin C to convert cholesterol into bile acids. Fruits contain vitamin C, or ascorbic acid, but the powdered pectin does not. 

The apparent Michaelis constants for pectinesterase are usually given in percentage of pectin, which constitutes a poorly defined substrate, so that the quantitative value of these data is limited. For pectinesterases of various origins, Km values of 0.04-0.24% of pectin were found.36,58-62 For orange pectinesterase, by using pectins having... 

Christensen TMIE, Nielsen JE, Mikkelsen JD. Isolation, characterization and immunolocalization of orange fruit acetyl esterase, in Progress in Biotechnology 14 Pectins and Pectinases (Visser J, Voragen AGJ, eds.), Elsevier, Amsterdam, The Netherlands, 1996, pp. 723-730. 

Christensen TMIE, Nielsen JE, Kreiberg JD, Rasmussen P, Mikkelsen JD. Pectin methylesterase from orange fruits characterization and localization by in situ hybridization and immunohistochemistry. Planta 1998 206 493-503. 

Rather thorough studies have now been made of the properties of the PM of tomatoes,20 21 44 62 63 66 orange peel,21 tobacco3 61 64 and alfalfa.49 The activity of PM is profoundly affected by the pH of the reaction mixture, the salt concentration and the cation component of the salt. In salt-free solutions, the activity of the PM of higher plants is nearly zero at pH 4.25 and increases linearly with a steep slope as the pH is increased to 8. Above 8 the pectinic acids are also demethylated by the action of alkali and the enzyme activity measurements therefore become unreliable. The relationship between activity and pH is also dependent on the salt content of the reaction mixture. 

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