More Than Youre Ex-pectin

More Than Youre Ex-pectin

By R. J. Foster
Contributing Editor 

Pectinsare some of the most versatile hydrocolloids. They can function as thickeners,gelling agents and emulsifiers due to their wide range of characteristics.

Pectin is a linear polymer of approximately 300 to 1,000 galacturonic acidunits. Each ring-shaped unit has a carboxylic acid group that exists in one ofthree forms: free carboxyl (-COOH), methyl-ester (-COOCH3), or primary acidamide (-CONH2). The ratio of these forms across a given pectin chain is one ofseveral factors that influences its characteristics.

High hopes 

The percent of carboxylic-acid groups in the methyl-ester form (esterified)on a pectin chain is expressed as DE, or degree of esterification.When pectins DE is greater than 50%, it is considered a high-methoxyl, or HM,pectin. Those with a DE less than 50% are referred to as low-methoxyl, or LM,pectins.

Under the correct conditions, HM pectins form short-textured,nonthermoreversible gels. Generally, they require soluble solids greater than60% to form gels. As the soluble solids in a system increase, so does thetemperature at which gelation begins. HM pectins also require low pH to gel,typically below 3.5. As pH decreases, rate and temperature of gelationincreases.

DE can also dictate gelling rate. As DE increases, so does reactivity, so thepectin gels more rapidly, at lower temperature, or at higher pH. Rapidsetpectins possess DEs less than 70% and can gel at temperatures around 75°C to85°C and at pH levels of 3.5 to 3.3. Medium-rapid-set pectins have a DEaround 68% and will gel within the range of 60°C to 75°C and at pH levels of3.3 to 3.1. Slow-set pectins have DEs greater than 67% and require temperaturesbelow 60°C and pH levels of 3.1 to 2.9.

Rapid-set pectins are ideal for applications that require suspension ofparticulates, such as fruit. Conversely, slow-set pectins allow air to escapefrom a product, yielding crystal-clear jellies or confections. However, thedesignation of rapid or slow set indicates the relative gelling rate of HMpectins under a given set of conditions. Product developers can adjust the gelling rate of almost any HM pectin bycontrolling system conditions like solids and pH.

Half empty or full 

Pectins with a DE of less than 50% are referred toas low methoxyl, or LM. They are typically made from raw materials that containhighmethoxyl pectin that is de-esterified in mild acidic or alkaline conditions.Acidic de-esterification yields conventional LM pectins containinggalacturonic acids and galacturonic methyl esters. Alkaline de-esterificationwith ammonium adds galacturonamide (-NH2) units, resulting in amidated LMpectins. The amount of these amide units is indicated as degree of amidation, orDA.

DE and DA determine the gelling characteristics of LM pectins. Conventional LM pectins form thermostable gels, but amidated LM gels areusually thermoreversible.

Unlike HM pectins, LM pectins require calcium for gelation. Solids and pH aresecondary factors. Amidated pectins have lower calcium reactivity but offer a wider range ofcalcium levels for maximum gel strength. For both forms, increasing calcium willincrease gel strength and gelling temperature, even to the point of pregelationat or very near boiling. Increasing DE reduces calcium reactivity of both conventional and amidated LMpectins.

Pectin makes perfect 

Pectins can achieve a host of textures. By considering the system conditionssolids, pH, working temperatures, other ingredientsdevelopers can selectthe ideal pectin.

HM pectins are ideal for traditional jams and jellies with sugar levels at orabove 65% soluble solids (Brix) and pH levels around 3. Low-sugar jellies andjams require LM pectins. While calcium in fruit is usually sufficient forgelling amidated LM pectins, conventional LMs require added calcium salts tofacilitate gelling.

Pectins can texturize fruit preparations for yogurt or fruit-toppingapplications. LM pectins will work across the entire range of fruit levels (20%to 100%), solids (20% to 65%) and acidity (pH levels from 3.6 to 4.0). AmidatedLMs can be used at lower levels, but provide less thixotropy than nonamidatedproducts.

Fruit-preparation gels should be firm enough to suspend fruit uniformly, yetbe thixotropic enough to allow pumping and stirring. Alone or in combinationwith other hydrocolloids, pectins also control syneresis and reduce colormigration from the fruit prep into the dairy phase. Developers should considersystem parameters like target solids and filling temperature, as well as fruitcharacteristics such as acidity, calcium content, integrity (whole, sliced,puréed), source and ripeness.

In acidic confectionery applications, such as jellies and jelly centers, HMpectins create a very fine, short yet tendertexture with excellent flavorrelease. Rapid gelation (due to solids levels less than 70%) can be controlledthrough strict adherence to formulation and processing parameters, making HMpectin well suited to continuous manufacturing systems. Buffered HM pectinsoffer additional control and ease of use.

LM pectins are ideal for products requiring lower pH levels to avoidundesirable contrasts with flavors such as peppermint or cinnamon. Increasedthixotropy is another benefit, as is the ability to cold-set a gel throughcalcium diffusion into the filling.

Pectins can be used as viscosifiers to enhance the mouth-feel of beverages. Addition of LM pectin to a reduced- calorie application can restore body lostdue to reductions in sugar or fruit content. Instant fruit drink powders mightemploy pectin to provide a fresh-juice texture. Suspension of pulp can alsoimprove with HM pectins.

Pectin can stabilize acid dairy beverages like yogurt drinks, milk and juicecombinations, and acidified soy or whey protein beverages. By adsorbing to thesurface of proteins, pectins form a protective shell often referred to as thefuzzy golf ball, protecting the proteins from coming together andprecipitating.

Pectin might not be the most common or economical choice in application areassuch as frozen desserts and novelties, baked items, or puddings and creams.However, pectin does carry a strong natural image that might make pectin achoice worth considering.

R. J. Foster has over a decade of experience in research & developmentand technical service in the food industry. He is a freelance writer specializing in technical communications and can bereached at [email protected].