The Plot Thickens: Gelatin, Pectin and other Hydrocolloids

by Miranda Kohout

Controlling water is one of the secrets to successful pastry. Mousses, sauces, ice creams and confections all rely on successfully harnessing and controlling water to bring a chef’s ideas to life. “Hydrocolloid” is a word many chefs had never heard before the rise of the Molecular Gastronomy movement, though it has been in use for a century. Hydrocolloids are simply water-soluble substances that thicken liquid or form gels, so whether you’re on the cutting edge of food technology or not, you likely encounter one or more hydrocolloids regularly.

Four Common Types of Hydrocolloids

Gelatin

One of the most common, obvious and easily accessible hydrocolloids is gelatin. Gelatin is a protein extracted from animal skin or bones. Most chefs use gelatin in either granules or sheets.

Gelatin sheets are available in different strengths, from strongest to weakest:

• Platinum, Bloom strength 230+
• Gold, Bloom strength 200
• Silver, Bloom strength 160
• Bronze, Bloom strength 140
• Titanium, Bloom strength 120
• Powdered Gelatin, Bloom strength 225

Note that exact bloom strength can vary by manufacturer.

One sheet of any type of gelatin will have the same Bloom strength as another type; it is the weight of the sheets that varies. For example, it is not necessary to use two sheets of titanium sheet gelatin to equal the gelling power of one sheet of platinum gelatin.

When creating recipes, assume as a starting point that one leaf of gold gelatin will firmly set 100 grams of liquid (note that the gelatin should be bloomed in a portion of the recipe’s liquid).

Converting between gelatin strengths can be tricky, and converting between sheets and powdered gelatin can be especially troublesome. Generally speaking, 1.88 g of powder equals the gelling strength of one sheet of gold gelatin. (Source: Michael Laiskonis, WordPress)

Pectin

Most fruits naturally contain some pectin, though it might just be trace amounts. Commercial pectin is extracted from citrus peels and apple pomace. Pectin is most commonly used in fruit preserves and confections such as pate de fruit. Regular citrus or apple pectin will fill the bill for most recipes, particularly confections or jams. For more specialized applications, LM (Low-Methoxyl) or NH pectins can offer better outcomes.

Starches

Starches come from grains, tubers and roots, and while their mechanisms of thickening are essentially the same, there are subtle differences among them that can help a chef home in on the exact texture or appearance they are seeking. Cornstarch is a staple in most kitchens, with tapioca and potato starch growing in popularity among savvy chefs and gluten-free bakers. Arrowroot has long been a popular option for those looking for an alternative to cornstarch, believing it to be more nutritious.

Special Carbohydrates

These are the “fancy” hydrocolloids. They are no longer truly new to pastry chefs, but they remain uncommon and a bit mysterious for many. Derived from seaweed, algae or bacteria, these gelling agents have unique properties and gelling mechanisms that can work beautifully where other hydrocolloids fall short. While pectin and starches are also carbohydrates, their upscale cousins have unique properties that set them apart. Agar agar, carrageenan, xanthan and guar gums and alginates are hydrocolloids that are a “special order” item for many pastry chefs. Still, they are valuable tools for creating a specific texture, effect, or appearance that can’t be achieved with gelatin or pectin.

Use of Hydrocolloids

Gelatin

Gelatin is sold in dry form and must be rehydrated before use, a process called “blooming.” Gelatin should be bloomed in cold liquid, as hot liquid can cause clumping and prevent all of the gelatin from rehydrating.

To bloom powdered gelatin, mix the granules with the amount of water specified in the recipe or with some of the liquid used in the recipe.

To bloom sheet gelatin, soak the sheets in cold water for a few minutes, then remove and squeeze them or blot them dry. Chefs should take care not to “over-bloom” sheet gelatin. The sheets can dissolve and weaken if left in the liquid too long.

For large-scale production, many chefs make gelatin mass: a combination of gelatin and three to six times the weight of the gelatin in water. When properly made, gelatin mass eliminates the need for blooming; the mass can be added directly to warm/hot preparations.

When a gelatin mixture is cooled very quickly, the bonds formed are disorderly and random, and the product’s set is weak. For the strongest bonds, a gelatin-based product would be allowed to cool slowly, at room temperature for hours, but this is not food safe. Allowing a gel to cool in the refrigerator for 24-36 hours is the happy medium that gives us both safe food and firm, stable protein bonds.

Pectin

Standard pectin requires three things to form a stable gel: sugar, acid and cooking. Pectin molecules in water develop a negative electrical charge and will not bond with one another. Our hygroscopic friend sugar will draw water to itself and away from the pectin molecules, exposing them to one another. Boiling the mixture will remove more water and concentrate the pectin molecules. Adding an acid will neutralize the pectin’s negative charge, allowing the molecules to form tight bonds with one another and form a gel.

The amount of pectin required for fruit preparations will vary with the amount of pectin naturally present in the fruit. Blueberries and certain apple varieties are naturally high in pectin; apricots and pears are on the low end of the pectin spectrum.

LM or Low-Methoxyl pectin molecules form bonds in the presence of calcium ions. The water-loving properties of sugar aren’t necessary to facilitate gelling in this case, allowing chefs to create low and no-sugar preserves.

As with standard pectin, the type of fruit used will affect a chef’s recipe. Fruits naturally high in calcium, such as plums, apples and quince, will need little added calcium to gel. Supplemental calcium is necessary for creating most low-sugar, LM pectin-based preparations.

NH (Non-Heat reversible) Pectin is a type of LM pectin that has been commercially modified. It bears a separate mention due to its ability to gel without boiling and its stellar performance in glazes and fillings.

Best practices call for a chef to mix pectin with a small amount of the recipe’s sugar before adding it to hot liquid. This helps disperse the pectin evenly and prevents clumping.

Starches

Starches thicken liquids by absorbing water. The amylopectin and amylose that form the structure of a starch break down in the presence of heat, allowing the starch to absorb water, swell and eventually burst. While they all function in essentially the same way, there are differences in how starches work that make one or the other better suited for a given application.

High-amylose starches, such as cornstarch, produce opaque gels that cut cleanly. Think custard pie. Gels made with these starches have higher gelation temperatures and resist thinning when reheated, a boon for sauces that need to be made in advance, but served warm.

Products made with high-amylose starches should not be frozen, as the product will weep upon thawing. Stirring a high-amylose starch once it has set can cause the mixture to thin.

For example, cornstarch begins to swell between 144°-262°F (62°-72°C) and is fully gelatinized at 203°F (95°C). Heating a cornstarch-based mixture beyond 203°F can decrease the starch’s thickening power.

High-amylopectin starches create clear, glossy gels and are ideal for glazes. Products made with these starches will freeze and thaw nicely. Note that they will thin if reheated or if subjected to overheating or over-stirring during cooking. Arrowroot and tapioca starch are both examples of high-amylopectin starches. Potato starch falls somewhere in between the two types.

To evaluate the thickening power of a starch, bring the mixture to a gentle boil. Then assess its thickness, remembering that starch-gelled liquids will continue to thicken as they cool.

Those who regularly use cornstarch will be familiar with making a slurry of starch and water to add to the heated mixture. A starch will not dissolve in cold water, but the water will help to keep the starch granules separate. If starch is added directly to hot liquid, it will quickly clump and the outer starch granules will immediately begin to swell upon coming in contact with the heated mixture, forming a waterproof coating around a dry lump of starch that no amount of stirring will be able to disperse.

It is important to consider gel strength when choosing a starch, as the amount of starch needed to thicken a given preparation can vary drastically. Potato starch offers the greatest thickening power among all the starches.

Seaweed, Algae and Bacteria

The world of special carbohydrate hydrocolloids is vast and fascinating. They have become easier to find as demand for them grows. Many chefs creating “free-from” recipes have found these hydrocolloids invaluable when replacing animal-based products or creating gluten-free baked goods.

For most of these ingredients, it is generally best to incorporate the hydrocolloid into the liquid using an immersion blender to ensure complete and even dispersal. Note that some hydrocolloids, just as some starches, will be weakened by over-mixing. Pay special attention to whether a hydrocolloid should be dissolved in hot or cold liquid.

Carrageenan

Carrageenan comes from seaweed and is commonly available as I-Carrageenan or K-Carrageenan, each with different thickening properties and requirements. Both types take some time to hydrate and must be simmered to set.

Alginates

Alginates form gels only in the presence of calcium and do not require heat to set. In the restaurant kitchen, they are best known for being used in combination with calcium citrate for spherification, or with dairy-based products for reverse-spherification. However, sodium alginate is also used for thickening and creating foams. It works best in non-acidic mixtures.

Gellan

Made by fermenting corn sugar with a specific bacterium, gellan gum sounds like a questionable food ingredient. However, it is safe to consume and produces very clear gels with a clean flavor. It gels in the presence of salts or acids.

Xanthan Gum

Like gellan, xanthan gum is produced via a combination of fermentation and bacteria. It can be made from corn, soy or wheat. Xanthan gum has recently gained popularity as an ingredient that can help replace gluten.

Xanthan gum is soluble in both cold and hot water. It thaws and freezes well, and is not affected by a solution’s pH or salt content, though high-sugar solutions may make it harder for xanthan gum to hydrate. It is not necessary to heat xanthan gum for it to gel.

Agar Agar

Known as a vegetarian substitute for gelatin and used for centuries as a gelling agent in its own right, agar agar is a seaweed-derived hydrocolloid. Its most notable characteristic is its high melting point. Agar agar solutions must be boiled to hydrate fully, then cooled to 110°F (38°C). To remelt an agar agar gel, you must heat it to 185°F (85°C), much higher than other gels. It works well in sugar-heavy preparations and should be used with strong flavors to mask its slight seaweedy taste.

A host of other powders and gums are used to form gels and thicken liquids. More specific information about using these other ingredients and how to use the hydrocolloids mentioned here is now widely available.

Ingredients That Can Affect the Performance of Hydrocolloids

Sugar

The same water-drawing action that helps a pectin-based gel to set can also be seen when sugar is added to a gelatin mixture. The water in the solution will be pulled to the sugar, leaving the gelatin molecules exposed and more likely to bond with one another.

A jam or jelly requires a sugar concentration of at least 60% to form a strong gel. Confections such as pate de fruit clock in closer to 75%. Note that adding sugar too quickly will reduce the temperature of a jam or jelly and may affect the setting power of the final product.

Sugar has been found potentially to increase the gelatinization temperature of a starch, which can affect its structure and other properties.

Acid

The optimal pH for setting a standard, high-methoxyl pectin gel is between 2.8 and 3.5, and the mixture should be around .5% acid by weight. LM pectin requires a range of 3-4.5 pH. A mixture that is too acidic will have a weak pectin structure and will often weep. This can be countered by raising the pH of the mixture with sodium citrate or adding another hydrocolloid such as locust bean gum. A pH lower than 4 can cause weaker bonds in gelatin, so ingredients such as citrus juice may require more or other gelling agents to set as the chef desires.

It has not been extensively studied, but evidence suggests that high concentrations of acid in a starch mixture can weaken the hydrogen bond between starch molecules, negatively affecting their gelling properties. Carageenan, sodium alginate, gellan and some other gums are sensitive to acidic environments, which can inhibit their ability to gel. Agar agar is the least affected by acid, but its flavor and texture may need to be accounted for.

Enzymes

Certain fruits contain protein-targeting enzymes that affect both gelatin and pectin bonds. Fruits such as pineapple, kiwi, papayas, ginger, melons and figs have naturally-occurring enzymes that break down proteins and weaken gelatin bonds. These fruits can still be used successfully, but they must first be cooked to a temperature that kills the protein-destroying enzyme, usually between 160°-185°F (71°-82°C). Canned versions of fruit have generally been brought to a temperature sufficiently high to destroy the enzymes.

These enzymes target specific proteins and do not affect the gelling properties of agar agar or other “molecular” hydrocolloids. Some affect pectin’s gelling ability and should be used with caution.

Alcohol

Small amounts of alcohol can increase gelatin strength. However, when the alcohol concentration in the gel rises above 30-50%, it can prevent the gelatin from properly setting. It can denature the gelatin proteins, making them unable to form a gel. Alcohol can also cause a gelatin mixture to be cloudy rather than clear. Alcohol has little to no effect on agar agar and may be a solution for making high-alcohol gels that won’t set with the use of gelatin. It should be used sparingly with xanthan and gellan gums. Some hydrocolloids set better in the presence of alcohol, so a certain amount of research is warranted before creating an alcohol-based gel.

Tannins

Like alcohol, tannins can strengthen a gelatin solution. At higher concentrations, though, tannins can negatively affect gel strength. Measuring the tannins in a solution isn’t possible for the average chef, so proceed cautiously when using ingredients such as strong tea or red wine. Tannins can also cause a gelatin product to be cloudy. Tannins have been found to affect the gelling power of agar and alginates, though this effect can be mitigated with other ingredients.

Salt

Standard table salt can cause gels (whether made from gelatin, starch or xanthan gum) to swell and can weaken the overall structure of the final product.

Milk

Gelatin proteins can form bonds with casein, one of the proteins in milk, creating a more cohesive network and a stronger gel. Casein has varying effects on other hydrocolloids.

Trivia

A gelatin’s strength is expressed in terms of “Bloom.” This measurement is named after Oscar T. Bloom, a chemist working in the Chicago meat-packing industry in the 1900s who invented the Bloom Gelometer, a device used to measure the rigidity of a gelatin film.

(This article appeared in the Summer 2025 issue of Pastry Arts Magazine)