Pectic Composition Research Articles

Oven-dried table olives: textural properties as related to pectic composition

The effects of processing treatments on the microscopic structure, pectic fractions and firmness of ripe olives (Olea europaea L Cassanese variety), processed by the 'Ferrandina' method for oven-dried table olive production, were studied. The process included a first heating step, a salting step and a final oven-drying process. Scanning electron microscopic observations of olive tissue structure revealed that heat treatment was highly damaging, affecting the intercellular pectic substances and producing cell separation. Epicuticular waxes were barely affected and limited the shrivelling of the fruit during the oven dehydration process. The pectin content was higher in the oven-dried olives than in the fresh samples. The sodium hydroxide-soluble fraction was the main pectin fraction in the olive tissues. Its content decreased markedly after the heating step, while it increased after the oven dehydration step. The softening of the olive tissues increased after heat treatment, and a correlation was found between protopectin content and firmness. In oven-dried olives a firming of the olive tissues was observed due to the de-esterification of pectin and to its decreased solubility resulting from an increase in cell wall calcium bridging. # 2000 Society of Chemical Industry

Pectic epitopes are differentially distributed in the cell walls of potato (Solanum tuberosum) tubers

Six monoclonal antibodies (mAbs) were used to map the distribution of pectic epitopes in the cell walls of potato (Solanum tuberosum L. cvs Kardal and Karnico) tuber tissue in both light and electron microscopes. Unesterified (mAb JIM 5 epitope) and methyl‐esterified (mAb JIM 7 epitope) pectins were abundant and equally distributed in all parenchymal and vascular cell walls. Homogalacturonans (HGAs) involved in Ca2+‐cross‐linking (mAb 2F4 epitope) were localised to the middle lamella and abundant at cell corners. The tuber cortex was densely labelled, but parenchymal cell walls in the perimedullary region contained few epitopes of calcium pectate except at corners and pit fields. In contrast, pectic side‐chains were not detectable in the middle lamella of all parenchymal cell walls, except in the cortex where mAb LM6 (arabinan epitope) labelled the entire wall. The galactan epitope (mAb LM5) was localised to a zone very close to the plasmalemma in cortical cell walls and was also less abundant at pit fields and in vascular cell walls. MAb CCRC‐M2 (rhamnogalacturonan I epitope) did not cross‐react. Our results show that the cell walls of potato tubers are not homogeneous structures and that the pectic composition of the walls is spatially regulated.

INFLUENCE OF OSMOTIC DEHYDRATION ON TEXTURE AND PECTIC COMPOSITION OF KIWIFRUIT SLICES

ABSTRACT In order to optimize the osmotic dehydration process as a pre-treatment to freezing, chemical and structural characteristics of the raw fruit have to be studied together with their influence on the solid liquid exchanges and on the quality of the end products Textural properties of fruits are intimately associated with the cellular structure and pectic composition. So the influence of osmodehydration on the modification of texture and water-soluble, oxalate-soluble and residual protopectin in kiwifruit slices was studied. To determine the optimum firmness level of the raw kiwifruit, the fruits were processed at three instrumentically measured texture levels: firm, medium and soft. Chemical and physical analyses showed that the biggest difference among the three groups of fresh kiwifruit was the protopectin content which was correlated directly with texture. No relationships were found between texture changes and pectic composition during osmodehydration, the slight firmness increase probably being produced by the soluble solids concentration.

The effect of preharvest foliar sprays of calcium on quality and shelf life of two cultivars of sweet bell peppers (Capsicum annuum L.) grown in plasticulture

The effect of preharvest calcium sprays on postharvest quality of sweet bell peppers grown in plasticulture was studied. Calcium was applied as three sprays of 0.4% (wt/vol) CaCl2 in water to plots of Oriole and Bell Boy peppers in each of 2 yr. Fruit weight, water loss, firmness, decay and the composition of the pectic fractions were determined at harvest and during storage. Preharvest sprays of CaCl2 increased the weight of fruit for Oriole, improved firmness retention in storage, decreased decay, increased pericarp wall thickness and the insoluble pectic fractions of both cultivars but had no effect on water loss in storage. The results suggest that Ca improves firmness retention through enhancing the pectic composition of cell walls and pericarp wall thickness. Effects of Ca sprays on reducing decay could not be attributed to factors measured in this work. Preharvest foliar sprays of CaCl2 show promise in reducing postharvest decay and improving firmness retention in sweet bell peppers grown under plasticulture. Key words: Capsicum annuum L., calcium, pectin, shelf life, postharvest decay

Effect of calcium treatment prior toBotrytis cinereainfection on the changes in pectic composition of grape berry

The influence of calcium on the process of infection byBotrytis cinereawas studied following calcium infiltration of grape berries, using Sauvignon, a cultivar ofVitis viniferaknown to be susceptible toB. cinerea.Calcium pretreatment had no significant effect on infection rate. Analysis of pectic fractions of rotten berries showed that total amount of pectins decreased during infection. The proportion of water and chelator soluble pectins increased over the same time period. These changes in pectic fractions were less pronounced when grape berries were calcium infiltrated prior to infection. Demethylated pectins produced by the fungal pathogen are probably protected by a rapid calcium chelation.

LITERATURE ABSTRACTS

INSTRUMENTAL MEASUREMENTS: Physicochemical Properties of Cocoyam Starch. R.D. Lauzon, K. Shiraishi, M. Yamazaki, S. Sawayama, N. Sugiyama and A. Kawabata. INSTRUMENTAL MEASUREMENTS: Studies on Rheological Properties of Rice‐Soya Crackers. M.V. Prince, P.K. Chatopadhyay and R.K. Mukherjee. INSTRUMENTAL MEASUREMENTS: Mechanical Properties of Wheat. Y.S. Kang, C.K. Spillman, J.L. Stele and D.S. Chung. INSTRUMENTAL MEASUREMENTS: Vkcoelastic Property Changes in Cheddar Cheese During Ripening. M. Rosenberg, Z. Wang. SENSORY MEASUREMENTS: Cheddar Cheese Texture Related to Salt Release During Chewing, Measured by Conductivity ‐ Preliminary Study (An Hypothesis Paper). F.R. Jack, J.R. Piggot and A. Paterson. FACTORS AFFECTING TEXTURE: Frozen Carrots Texture and Pectic Components as Affected by Low Temperature Blanching and Quick Freezing. M. Fuchigami, K. Miyazaki and N. Hyakumoto. FACTORS AFFECTING TEXTURE: Programmed Freezing Affects Texture, Pectic Composition and Electron Microscopic Structures of Carrots. M. Fuchigami, N. Hyakumoto. FACTORS AFFECTING TEXTURE: Texture and Pectic Composition Differences in Raw, Cooked and Froze‐Thawed Chinese Cabbages due to Leaf Posithn. M. Fuchigani, N. Hyakumoto. FACTORS AFFECTING TEXTURE: Low Temperature Blanching Effects on Chemistry, Firmness and Structure of Canned Green Beans and Carrots D.W. Stanley, M.C. Bourne. FACTORS AFFECTING TEXTURE: Rheological Properties of Solutions and Emulsions Stabilized with Xanthan Gum and Propylene Glycol Algiiate. D.J. Pettitt, J.E.B. Wayne, J.K. Renner Nantz and C.F. Shoemaker. FACTORS AFFECTING TEXTURE: Postmortem Delay Time and Heating Rate Affext Tenderness and Ultrastructure of Prerigor Cooked Bovine Muscle. J.Y. Wu (Dept. of Food Sci.), E.W. Mills and W.R. Hennirig. GENERAL PRINCIPLES: ‘Weak Gel’ Properties of Khan Flour from Belschrniedia sp. ‐ a Traditional Food Thickener from Tropical West Africa R. Ndjouenken. GENERAL PRINCIPLES: Gelation Mechanism of Methylhydroxypropylcellulose in Aqueous Solution. Y. Yuguchi, H. Urakawa, S. Kitamura, S. Ohno and K. Kajiwara. GENERAL PRINCIPLES: Gelation Mechanism and Rheological Properties of Rice Starch. C.‐Y. Lii, Y.Y. Shao and K.H. Tseng.

Chinese Cabbage Midribs and Leaves Physical Changes as Related to Freeze‐processing

ABSTRACTDifferences were investigated in texture, drip and pectic composition of raw or blanched Chinese cabbage midribs and leaves after conventional (F) or program freezing (PF). Softening of tissues and amount of drip were least to greatest: PF‐5°C/min < PF‐2°C/min < F‐35°C < F‐20°C, respectively. Freezing‐thawing accelerated release of pectin but the freezing rate did not affect pectin release much. Total pectin in raw midribs was less than in raw leaves. The leaves contained more low methoxyl pectin than midribs, but the high methoxyl pectin was almost the same. Cell damage in frozen‐thawed midribs and leaves by light‐and electron‐microscopy appeared extensive.

Electron and Light Microscopy Structure and Polysaccharide and Pectic Composition of Highbush and Rabbiteye Blueberries

Rabbiteye (Vaccinium ashei) blueberries were harvested in Mississippi and highbush (V. corymbosum) blueberries were harvested in Michigan. The berries were rapidly cooled to 5C after harvest and kept at this temperature for 48 h before being analyzed as fresh fruit or freezing for later analyses. Microstructural (light and scanning/transmission electron microscopy) and chemical (pectins, cellulose, hemicellulose, lignin, and fiber) evaluations were performed to evaluate differences between the two types of blueberries. Scanning electron micrographs showed that rabbiteye spp. have thicker epidermal and subepidermal cells than highbush spp. Transmission electron micrographs also showed that rabbiteye spp. have a thicker, more uniform cuticle layer than highbush spp. Rabbiteye spp. contained higher fiber and complex polysaccharides than highbush spp. Although, there were no differences in total pectins, rabbiteye berries had lower water soluble pectins and oxalate soluble pectins than highbush blueberries. Differences in polysaccharides and pectins between highbush and rabbiteye berries indicate that their cell wall components differ. These differences, along with the variation in subepidermal, epidermal and cuticle layers of the skin, provide valuable information to explain the textural differences between rabbiteye and highbush blueberries.

Effect of harvest maturity on pectic substances, internal conductivity, soluble solids and gel breakdown in cold stored ‘Songold’ plums

Abstract ‘Songold’ plums (Prunus salicina Lindl.) were harvested at optimum and post-optimum maturity with a flesh firmness of 64 and 44 N, respectively. After cold storage for 10 days at −0.5 °C, followed by 18 days at 7.2 °C, the plums were ripened for 14 days at 10 °C. The fruit was analysed for soluble solids, internal conductivity, pectic composition and viscosity of water soluble pectin at eight examination stages during storage and ripening. Insoluble pectin levels declined during cold storage and ripening while soluble pectin levels increased to make up the difference. Neither harvest maturity nor storage time had a significant effect on the concentration of calcium pectate, and this pectic fraction did not appear to influence development of gel breakdown (GB). Water soluble pectin and availability of cell fluids, as indicated by viscosity and internal conductivity, respectively, indicated a high gel potential in plums of both maturities, but at different stages during storage and ripening. Significant levels of GB developed only in plums harvested at post-optimum maturity. In this fruit, significantly higher sugar levels and loss of cell membrane integrity early in storage probably enhanced formation of pectin-sugar gels as cell fluids bind with pectins in cell walls.

Programmed Freezing Affects Texture, Pectic Composition and Electron Microscopic Structures of Carrots

ABSTRACTRaw and blanched carrots (3 min, boiling water) were frozen at −2°C, −3°C, −4°C or −5°C/min (final −20°C or −50°C) then thawed at 20°C or 100°C. Firmness of thawed raw carrots was: −5°C > −4°C > −3°C > −2°C/min. Effect of freezing rate on blanched carrots was less than that on raw carrots, but firmness of thawed carrots was not affected by final temperature of freezing. When raw carrots were thawed at 20°C, high methoxyl pectin decreased. Pectin decrease in blanched carrots caused by freezing was greater than that in frozen raw carrots. Effects of slow‐freezing, programmed‐freezing (slow + quick + slow) and quick‐freezing showed quick freezing (—5°C/min) best for texture. As freezing rate decreased, drip increased. A wide difference among experimental samples in fine structure was revealed by cryo‐scanning electron microscopy.

Texture and Pectic Composition Differences in Raw, Cooked and Frozen‐Thawed Chinese Cabbages due to Leaf Position

ABSTRACTDifferences in texture of raw, cooked and blanched‐frozen‐then‐thawed Chinese Cabbages and their leaf positions (10, 20, 30, 40, or 50th midribs from the outside) were investigated. Firmness and rupture strain of raw midribs were low, but increased after short cooking time. Crispness of tissues decreased and elasticity increased. The 20–30th midribs were slowest to soften during cooking, while the inner midribs from the 40th were more readily softened. The 40th contained more high methoxyl pectin than did the 20th. Therefore, they were more quickly softened because of pectic release by transelimination. After freezing‐thawing, firmness decreased and rupture strain increased. Midribs with firmer texture contained more pectin. After freezing‐thawing, amounts of pectin in midribs decreased.

Effect of storage regimes on pectolytic enzymes, pectic substances, internal conductivity and gel breakdown in cold stored ‘Songold’ plums

SummaryPlums (Prunus salicina cv. Songold) were cold stored according to a single-temperature regime comprising 28 d at −0.5°C, and a dual-temperature regime comprising 10 d at −0.5°C followed by 18 d at 7.2°C. After cold storage, the plums were ripened for 8 d at 10°C. Pectolytic enzyme activity, pectic composition, internal conductivity and gel breakdown were determined at seven stages during storage and ripening. Although not exposed to chilling temperatures prior to harvest, approximately 10% of the plums exhibited gel breakdown at harvest, indicating that the disorder cannot be classified solely as a cold-storage chilling disorder. The higher temperatures of the dual-temperature regime resulted in higher polygalacturonase activity than with the single-temperature fruit. Consequently, protopectin degradation and the concomitant production of water- soluble pectins were greater in the dual-temperature fruit. Single-temperature storage resulted in higher pectinmethylesterase activity during the latter s...

Effects of Various Chlorides on the Softening of Cooked Japanese Radish Roots and on the Pectic Composition after Cooking

Effects of Various Chlorides on the Softening of Cooked Japanese Radish Roots and on the Pectic Composition after Cooking

LITERATURE ABSTRACTS

GENERAL PRINCIPLES: Wall Slip Corrections for Couette and Parallel Disk Viscometers. A. Yoshimura and R. K. Prud'HommeGENERAL PRINCIPLES: Foam Rheology: III. Measurement of Shear Flow Properties. S. A. Khan, C. A. Schnepper and R. C ArmstrongGENERAL PRINCIPLES: Stability of Bovine Muscle Connective Tissues. V. M. Bernal and D. W. StanleyGENERAL PRINCIPLES: Application of Reaction Kinetics to the Denaturation of Whey Proteins in Heated Milk. F. Dannenberg and H. G. KesslerGENERAL PRINCIPLES: Rheological Properties of Ultrafiltered Skim Milk. M. Hallström and P. DejmekGENERAL PRINCIPLES: Mechanical Studies of Sol‐Gel Transition: Universal Behavior of Elastic Modulus. Masayuki Tokita and Kunio HikichiGENERAL PRINCIPLES: Rheological and Thermal Properties of Carrageenan Gels. Effect of Sulfate Content. Mineo Watase and Katsuyoshi NishinariGENERAL PRINCIPLES: Dymanic Viscoelasticity and Anomalous Thermal Behaviour of Concentrated Agarose Gels. Mineo Watase and Katsuyoshi NishinariGENERAL PRINCIPLES: Foaming Properties of Protein Solutions: Comparison of Large‐Scale Whipping and Conductimetric Methods. David J. Wright and John W. HemmantFACTORS AFFECTING TEXTURE: Responses of CA‐stored Bramley's Seedling and Cox's Orange Pippin Apples to Modified Atmosphere Retail Packaging. J. D. Geeson, S. M. Smith, Helen P. Everson, Pia M. Genge and K. M. BrowneFACTORS AFFECTING TEXTURE: Restructured Pork with Texture Variation. N. G. Marriott, S. K. Phelps, C. A. Costello and P. P. GrahamFACTORS AFFECTING TEXTURE: Texture Changes in White Bread: Effects of Processing and Storage. U. Stollman and B. LundgrenFACTORS AFFECTING TEXTURE: Chemical Composition and Rheological Behaviour of Strawberry Jams Relation with Fruit Content. E. Costell, E. Carbonell and L. DuranFACTORS AFFECTING TEXTURE: Influence of Sugar and Cyanide Concentrations and Paste Viscosities of Cassava Flour on Fried Cassava Chip Quality. A. M. AlmazanFACTORS AFFECTING TEXTURE: Influence of Hot and Cold Boning on the Palatability, Textural and Economic Traits of Restructured Beef Steaks. D. L. Seman, W. G. Moody, J. D. Fox and N. GayFACTORS AFFECTING TEXTURE: Influence of Soy Protein and NaCl on the Rheological Properties of Beef, Pork or Chicken Muscle Homogenates. M. A. Bianchi, A. M. R. Rilosof and G. B. BartholomaiFACTORS AFFECTING TEXTURE: Relationship of Water Content to Textural Characteristics, Water Activity and Thermal Conductivity of Some Commercial Sausages. G. R. Ziegler, S. S. H. Rizvi and J. C. ActonFACTORS AFFECTING TEXTURE: Texture of Cooked Mantle of Squid Ilex argentinus as Influenced by Specimen Characteristics and Treatments. I. Kolodziejska, Z. E. Sikorski and M. SadowskaFACTORS AFFECTING TEXTURE: Relationship Between Pectic Composition and the Softening of the Texture of Japanese Radish Roots During Cooking. M. FuchigamiFACTORS AFFECTING TEXTURE: Intrinsic Viscosity of Tomato Serum as Affected by Methods of Determination and Methods of Processing Concentrates. T. Tanglertpaibul and M. A. RaoFACTORS AFFECTING TEXTURE: Rheological Properties and Conformation of Tomato Paste Pectins, Citrus and Apple Pectins. T. D. Chou and J. L KokiniFACTORS AFFECTING TEXTURE: Effect of Aging and Mustard Flour on Rheological Properties of Model O/W Emulsion. R. Fischbach and J. L. KokiniFACTORS AFFECTING TEXTURE: Cold Shock in Fish: Its Characteristics in Bighead. R. W. H. Parry, M. V. Alcasid and E. B. PanggatFACTORS AFFECTING TEXTURE: Continuous Emulsification and Gelation of Dairy Ingredients by HTST Extrusion Cooking: Production of Processed Cheeses. F. Zuber, D. Megard and J. C. CheftelFACTORS AFFECTING TEXTURE: The Effect of Fermentation Temperature, Flour Type, and Starter on the Properties of Sour Wheat Bread. H. Salovaara and T. ValjakkaFACTORS AFFECTING TEXTURE: Rheological Properties of Ultrafiltered Skim Milk. I. Effects of pH, Temperature and Heat Treatment. M. Hallstrom and P. Dejmek.FACTORS AFFECTING TEXTURE: Improvement of Quality of Whipping Cream by Adding Carrageenan and Milk Constituents. II. Influence of Additives on the Physical Properties of Whipped Cream. D. Precht, K.‐H. Peters, and J. PetersenFACTORS AFFECTING TEXTURE: The Effects of Salt Concentration and pH Upon Water‐Binding, Water‐Holding and Protein Extractability of Turkey Meat. R. I. Richardson and J. M. JonesSENSORY EVALUATIONS: Sensory Profiling and Multidimensional Scaling of Selected Finnish Raye Breads. U. Hellemann, H. Tuorila, H. Salovaara and L. TarkkonenSENSORY EVALUATIONS: Texture and Sensory Evaluation of Frankfurters Made with Different Formulations and Processes. C. M. Lee, R. C. Whiting and R. K. JenkinsINSTRUMENTATION AND METHODOLOGY: Adaptation of the Instron to Determine the Surface Tension of Ice Cream Mix. S. A. Wittinger and D. E. SmithINSTRUMENTATION AND METHODOLOGY: Double Direct Shear Test for Potato Texture. D. R. McComber, R. A. Lohnes and E. M. OsmanINSTRUMENTATION AND METHODOLOGY: Computer Simulation of the Attrition Patterns of Particulated and Agglomerated Foods. M. Peleg and M. D. NormandINSTRUMENTATION AND METHODOLOGY: A Rapid Method for the Evaluation of Emulsion Stability of Non‐Dairy Creamers. R. M. Tran and M. A. EinersonINSTRUMENTATION AND METHODOLOGY: Elongational Viscosity Measurements of Melting American Process Cheese. O. H. Campanella, L. M. Popplewell, J. R. Rosenau and M. Peleg

Host‐plant resistance of sorghum: Differential hydrolysis of sorghum pectic substances by polysaccharases of greenbug biotypes (Schizaphis graminum, homoptera: Aphididae)

AbstractPectic substances extracted from different varieties of sorghum are hydrolyzed at differing rates by unfractionated polysaccharases isolated from two biotypes (C, GBC; and E, GBE) of the sorghum pest, Schizaphis graminum (the greenbug). A higher degree of susceptibility of a sorghum variety is associated with a greater rate of hydrolysis of sorghum pectic substances by a greenbug biotype. Increases in the specific activity of polysaccharases on the pectic substances from a resistant sorghum variety are dependent on the duration that a biotype is maintained as a colony on that variety. Polysaccharase activity of GBE on arabinogalactan was significantly greater than GBC. However, there were no differences between the biotypes on the depolymerization of a variety of other plant matrix polysaccharides and a synthetic polysaccharide. The sequence of substrates of increasing refractoriness to hydrolysis are: arabinogalactan < microcrystalline cellulose < xylan < pectin < 2,3‐diacetyl pectin < α‐1,4‐galacturonan. Pectic substances from sorghum varieties resistant to GBC but susceptible to GBE are relatively lower in arabinogalactan with elevated levels of uronic acid (UA) compared to varieties susceptible to both biotypes. A sorghum variety resistant to both GBC and GBE was lowest in levels of arabinogalactan, highest in UA, and highest in fructan content, which in the other varieties occurred only in trace amounts. Pectic composition of rhamnose, xylose, and glucose showed no relationship to resistance. Bound phenolics (potential inhibitors of enzyme activity) were not detected in any of the sorghum pectic substances. The relationship of plant matrix polysaccharides to host‐plant aphid biotype compatibility is discussed.

Le pneumatode chez Phoenix dactylifera. II. Ultrastructure de la paroi de la cellule aérifère chez des pneumatodes jeunes provenant de cultures axeniques

The pneumatode in Phoenix dactylifera is composed of air-filled cells with multilayered walls. Three main layers, L1, L2, and L3, have a pectic, polysaccharide, and proteic composition. When ageing, the last layer gives rise to wall outgrowths which are covered with a thin lamella (L4) essentially polysaccharidic in nature as are the wall and all material of intercellular spaces. Inwards, there appears a thin layered deposit (L0) that might correspond to beginning suberisation. The wall outgrowths are warts composed of juxtaposed vesicles. Every vesicle is constituted by a thin envelope and a matrix with a central globule inside. In the intercellular spaces, between young cells with still smooth walls, a fibrillar material is visible among a mosaïc of polysaccharidic and proteic matter. When vesicles appear, they release an homogenous-appearing material.

PECTIC CONTENT OF APPLES IN RELATION TO THIOCYANATE SPRAYS

An earlier report (5) has described the effect of thiocyanate sprays on sugars and certain other constituents in apples. The present paper is a continuation of the general problem with attention directed to the pectic constituents. In previous work it was noted occasionally that apples sprayed with thiocyanates were found to keep better in cold storage at 3? to 5? C. than control samples not sprayed with thiocyanates. Since changes in pectic substances are known to occur in connection with the ripening and softening of fruit, it was considered worth while to examine suitable samples of sprayed and unsprayed material to find out if the improved keeping quality might be related to differences in pectic composition. Titratable acidity was determined on most of the samples. Several investigators (1, 2, 3, 4) have made a study of the pectic changes occurring in apples during ripening. In general, the results show a gradual change from insoluble protopectin to soluble pectin accompanied by a decrease in the thickness of the cell wall. Materials and methods

PECTIC CONTENT OF PLANT MATERIALS

Many plants and plant materials such as wood (2), tea (25), tobacco (15), cotton (16), hops (13), ramie (11), flax (12), grass (6), potato (10), plantain seed (20), celery (9), limes (22), guava (1), bergamot (23), and root hairs (21), have been shown to contain pectic compounds. Because different methods of extraction and analysis were employed, it is impossible to make comparative studies from these data of the pectic composition, types of pectic materials, and distribution of pectic compounds in these plants. A systematic study, employing uniform treatment of the pectic materials of leaves, cereal grains, apples, and citrus fruits, was conducted by Nanji and Norman (18). They determined water-soluble pectin, oxalic-acid-soluble pectin and ammonium-oxalate-soluble pectin. These data were interpreted as representing pectic material present as pectin, pectin in combination with metallic ions, and pectic acid. This interpretation was based on the theory that protopectin is an insoluble calcium, magnesium, or iron salt (19), and that treatment with oxalic acid and ammonium oxalate dissolved the pectin and pectates combined in this manner. More recent studies, however, (3, 4, 14^ 17, 24), lead to the conclusion that the pectic molecule is essentially a long-chain, poly-galacturonic molecule combined through intermolecular forces and anhydride structure to form the insoluble protopectin layers of the cell wall and middle lamella. Single treatment with water or acid does not remove any definite pectic compound, but yields a part of a series of pectic substances; continued hydrolysis progressively dissolves the entire protopectin layer. The lack of quantitative data for comparison of the distribution of pectin in the plant phyla has led to the present study. A large number of plants and plant materials have been included, and in order to obtain comparative data for the concentrations of each pectic fraction present, a system of extraction involving successive stages of hydrolysis was employed. The first stage involves the removal of the water soluble pectin ; the second, the easily hydrolyzable protopectin; and the third, the difficultly hydrolyzable protopectin. These analyses have been supplemented by data on gelling power of the pectic material. Extraction and analyses One hundred grams of the material was ground in a sausage mill ; 500 ml. of water were added, and the mixture was heated for one hour at 90? C, evaporated water being replaced during the heating. The pulp was then pressed free of the liquid and returned for a second extraction with 500 ml. of water containing 0.155 ml. H2S04 (pH = 1.5). The pulp was again