celluloses and pectins revisted

7/29/2019 Celluloses and Pectins Revisted

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Celluloses and Pectins RevistedSee


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Pectins Pectins are mainly used as gelling agents, but

can also act as thickener, water binderandstabilizer.

Low methoxyl pectins (< 50% esterified) formthermoreversible gels in the presence of calciumions and at low pH (3 - 4.5)

High methoxyl pectins rapidly(>50% esterified)

form thermally irreversible gels in the presence ofsufficient (e.g. 65% by weight) sugars such assucrose and at low pH (< 3.5); the lower themethoxyl content, the slower the set.
http://www.lsbu.ac.uk/water/hydrat.htmlhttp://www.lsbu.ac.uk/water/hydrat.html


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Pectins (continued) The degree of esterification can be

(incompletely) reduced using commercial

pectin methylesterase, leading to a higherviscosity and firmer gelling in the presence ofCa2+ ions. Highly (2-O- and/or 3-O-galacturonic acid backbone) acetylated pectinfrom sugar beet is reported to gel poorly buthave considerable emulsification ability dueto its more hydrophobic nature, but this maybe due to associated protein impurities


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Pectin Gelation


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High Methoxy Pectin


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Low Methoxy Pectin


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Pectin action in jellies Pectin produces structure and a kind of

stiffness in jellies and jams by forming awater-holding network within the juice orcrushed fruit.

Before jelling starts, individual molecules ofpectin are surrounded and isolated from each

other by water molecules. If the surroundingsolution is acid enough, the pectin loses someof its attraction for these isolating watermolecules.


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Pectin action in jellies (con.)


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Cellulose Gums


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Cellulose gum types Carboxy methyl cellulose (CMC)

Carboxylated, water soluble, many forms, prevent ice crystal formation,

Hydroxy propyl cellulose (HPC) Increased hydrophobicity, good emulsifier

Methyl Cellulose Methylated, cold water soluble, viscosity increased by heating, hot water

insoluble

Microcrystalline cellulose Partially depolymerized; water soluble; non caloric filler


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Carboxy Methyl Cellulose

(CMC) Differ in respect to:

Degree of substitution (number of

substitutions per glucose molecule) 0.4 to0.7 for food grade CMC

Degree of Polymerization (number of

molecules modified) Uniformity of substitution


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CMC


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Food uses of CMC Ice cream stabilizer prevent ice crystal

formation

Icings, pie fillings & puddings to preventsyneresis

Cakes to increase volume

Protective colloid for flavor emulsions


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CMC and other GumApplications


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Pie Fillings Fillings for Danish and pies present difficult formulation

problems. They must pump or spread properly duringmakeup and go through the bake cycle without boilingover. Such fillings are frequently frozen during storage

and distribution and must retain a pleasing texturewhen thawed for consumption. The basic structural material in fillings is usually a

modified starch. Gums complement starch properties. Asoft gel former such as carrageenan or calcium alginatehelps suspend fruit pieces. Weeping is controlledthrough use of agar, high-viscosity CMC or acombination of locust bean plus xanthan.

At high temperatures, filling viscosity decreases,causing it to run over the side of the crust. MC or HPMCgums, with their ability to gel at higher temperatures,overcome this difficulty. The gel liquefies upon coolingso the filling in the finished product is not stiff or

rubbery.


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Cakes and cake donuts Cake and cake donut quality depends, in part,

upon proper batter viscosity during baking orfrying. If cake batter is thin and watery, leavening

gases escape too easily, giving a lower finishedvolume. Low viscosity in cake donut batter oftenresults in uneven expansion and a dense core. Amedium-viscosity gum, such as xanthan, locustbean, guar or CMC, can help adjust batterperformance


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Other bakery applications Frozen dough can suffer water loss and ice crystal growth that

shortens its shelf life. A water-binding gum such as arabichinders sublimation of water from the dough, while CMCinhibits ice crystal growth.

Bread and yeast-raised sweet goods benefit from water-binding gums that retain moisture and lengthen shelf life. Inhigh-fiber bread formulations, the gums guar, xanthan or CMChelp retain water in the finished product and improve doughstability during proofing and baking because of their highabsorption rate.

Meringues and angel food are protein-stabilized foams(whipped egg whites). Foam stability is enhanced whenresistance to flow, or viscosity, increases. Weeping afterbaking can also be a problem. Medium- and high-viscosity CMCaddresses both needs and are recommended for these uses.


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Applications of HPC Whipped toppings

Salad dressings

Edible films

Imitation dairy products

Aerosol frozen toppings

celluloses and pectins revisted

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