Carrot pectin

Sajjaanantakul, T., Van Buren, J. P., and Downing, D. L. (1993). Effect of cations on heat degradation of chelator-soluble carrot pectin. Carbohydr. Polym. 20 207-214. 

TABLE III. Methylation analyses of carrot pectin and the carboxyl-reduced polysaccharide... 

Smout, C., Ozcan, S.E., Fachin, D., Verlent, I. Vu Truong, S., and Hendrickx, M.E. (2003) Mild-heat and high-pressure inactivation of carrot pectin methylesterase a kinetic study. Journal of Food Science, 68, 1377-1383. 

Our two network model of the primary wall receives support from a variety of indirect observations. For example it has been shown Aat when a cell wall is regenerated by a carrot protoplast a homogalacturonan/ rhamnogalacturonan shell is laid down first, through which the cellulose/ hemicellulose network is later intercalated (8). Further evidence that pectin may form an independent network is seen in the fact that walls from suspension-cultured cells of tofnato Lycopersicon esculentum VF 36),... 

Fig. 10. Intercellular junction zones of carrot cells grown in suspension have been observed in electron microscopy after immunogold labeling with the 2F4 antibody, (a) no treatment of the sections prior to labeling the gold particles are restricted to the center of the junction zones (b) enzymatic (pectin methyl esterase) deesterification of the E.M. grids before labeling the deesterified pectins present in the primary walls now bind the probe. Scale bars = 1 pm.

The structural features of ceU wall polysaccharides of carrots have been studied by Stevens and Selvendran (1984) and Massiot et al.(1988). Plat et al.(1991), Ben Shalom et al.(1992) and Massiot et al.(1992) investigated the changes in pectic substances of carrots after blanching, dehydration and extended heat treatment. Data on the changes in ceU waU polysaccharides of canned carrots are lacking. This study aims to investigate the effect of preheating time at low temperature and the addition of CaCL on texture and on the composition of various pectin fractions of carrots canned by conventional and by a new process. 

Degree of methylation (DM%) of total pectin of carrot alcohol insoluble sohds (AIS) was decreased from 60.73% for fresh carrots to 48.70, 44.62 and 43.83% for canned carrots preheated at 65°C for 15. 30 and 60 min, respectively (Fig. 2). Similar levels of demethylation were also reported in potato (Bartolome and Hoff, 1972), in carrots (Lee et al., 1979) and in snap beans (Adams and Robertson, 1987) when they were blanched at low temperature between 65°C and 70°C. 

Figure 2. Degree of methylation (DM) and degree of acetylation (DAc) of the total pectin of fresh and canned carrots...

The AIS of fresh and canned carrots were sequentially fractionated into water-soluble pectin (WSP), oxalate-soluble pectin (OXSP), acid-soluble pectin (HSP), alkah-soluble pectin (OHSP), hemicellulose and cellulose. The distribution of uronic acid among various fractions is presented in Table 1. WSP of fresh carrots accounted for 19.0% of the total pectin, while OXSP constituted 29.6%. HSP represented the lowest (12.0%) pectin fraction, whereas OHSP was the highest (35.6%) In the hemicellulose and cellulose fractions significant amounts of uronic acid were found. Heat treatments during canning altered the proportion... 

Figure 5. HPSEC elution pattern of pectin fractions of canned carrots preheated at 65°C for different times, (a) WSP, (b) OXSP, (c) HSP,...

DM and DAc of various pectin fractions except those of OHSP (due to deesterification during extraction) are summarized in Table 5. The DM of WSP of conventionally canned carrots did not significantly differ from that of fresh carrots,while in the presence of CaCk a considerable increase was observed. This increment can be ascribed to cross-Unking of water soluble-low methylated... 

Degree of methylation (DM%) and degree of acetylation (DAc%) of the pectin fractions of carrots canned by conventional and by a new process in the presence of CaCk Fraction Fresh Conv. Conv.+ New +... 

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. 

Native pectin esterases can be used for protecting and improving the texture and firmness of several processed fruits and vegetables these include apple slices (53), canned tomatoes (54), cauliflower (55), carrots (56), potatoes (56), beans (57) and peas (91). 

Pectinesterase action was first reported in 1840 by Fremy (56). He noted that the addition of carrot juice to a pectin solution caused formation of a gel. This gel was produced by the enzymatic deesterification of pectin followed by precipitation of the resulting polygalacturonic acid as calcium pectate 20), Various names such as pectin meth-oxylase and pectin methyl esterase have been applied to the enzyme, but pectinesterase is the preferred trivial name (57). 

---