Hydrocolloids

Stella Culinary's Guide To Agar Gels

Winer Citrus Terrine Using AgarAgar is a gelling agent derived from red algae that is commonly used in Asian cuisine, modern kitchens, and as a substitution for gelatin in vegan and vegetarian recipes.

In a previous lecture series, I discussed how gelatin is commonly used and some of it's common pitfalls. One of the major shortcomings of gelatin is its inability to set in acidic environments. Take for example the winter citrus terrine pictured left; when I first started developing this recipe, I used gelatin. Time and time again, the terrine wouldn't set up as I planned.

When I took the pH of the terrine mixture, I realized it was at 3.2, which is below the acidity threshold of gelatin at 4. When I switched to agar, my setting problems went away, only to be replaced by other issues such as mothfeel and weeping (agar gels tend to leak liquid). But with a little research and a deeper understanding of how agar gels work, I was able to fine tune the citrus terrine to come out exactly how I wanted it.

The purpose of this two part video series is to give the knowledge needed to understand the intricacies of agar gels, allowing you to create your own, unique dishes when gelatin simply won't cut it.

An introduction to agar gels

An Introduction To Agar Gels | Part 1 of 2


How to Create an Agar Gel | Part 2 of 2

Further Information


Agar At A Glance - Infographic

How to Create an Agar Gel + Common Pitfalls | Part 2 of 2



Watch Part One Of This Video

In our previous video we talked about what agar is, some of it’s properties, and why you may or may not want to use it. In this video we’re going to go over how to create an agar gel and some of it’s common pitfalls.

Agar comes in the form of a white powder, and its use percent ranges from .2% (to set a standard gel) to .5% (for a firm gel), calculated based upon the liquid’s weight.

Example:

  • 1,000g Base Liquid

  • X.002 (.2%)

_________________
= 2g Agar to set a standard gel.

As with gelatin, agar is a hydrocolloid, meaning it can suspend or trap water, but to ensure a satisfactory outcome, it needs to be properly hydrated and dispersed.

The typical hydration procedure for agar is to first dissolve it into the liquid you want to gel by whisking, bringing the liquid to a simmer, and simmering for 4 minutes. At the end of four minutes, blend for 15-30 seconds using an immersion blender, strain, and allow to set. The added shearing power of an immersion blender will ensure even dispersion and proper hydration.

Although a standard blender can be used for dispersion (after the agar gel is simmered for 4 minutes), the rapid speed of the blender blade will incorporate extra air, which can then become suspended in the gel as it sets. These air pockets will reflect light, giving the gel an opaque appearance, instead of clear.

As we talked about in our last video, agar’s setting temperature is 95°F/33°C, and will set rapidly at this temperature. This makes agar extremely convenient to use as a gelling agent when you don’t have time to wait for gelatin to set, which takes anywhere from 12-24 at 59°F/15°C or below.

Common Agar Pitfalls

Agar is fairly easy to use, but there are some common reasons why a gel will fail or not perform as desired:

  • Improper Hydration: Make sure the agar is simmered in your base liquid for at least 4 minutes and then mixed with an immersion blender before straining and allowing to set.

  • Syneresis: Agar gels will “weep” or “leak liquid,” causing the gel to dehydrate and not perform as expected, especially when using it to set a terrine that will later be unmolded. This can be counterbalanced by the addition of .1% locust bean gum, calculated by the weight of the liquid being gelled.

  • Prolonged heating outside of the pH range of 5.5-8, although this is a less common problem. When we make our winter citrus terrine at Stella, with a pH of 3.2, the agar is still simmered in low pH citrus juice for 4 minutes to fully hydrate, without any adverse affect on the gel setting.

  • Tannic acid (commonly found in red wine and tea), in a known inhibitor of agar gels, but can counter balanced by the addition of 1% glycerol, based on the liquid’s weight.

If left uncovered, agar gels will dehydrate, causing them to loose moisture, which will adversely affect the gel’s texture. However, agar will swell in the presence of moisture, meaning gels can be rested in liquid containing a complimentary flavor, preserving its texture and enhancing it’s taste.

What Is Agar Good At?

Unlike gelatin, agar allows you to create vegetarian/vegan gels (since it’s seaweed based), will work in acidic environments, can tolerate high alcohol percentages (about 40%), and is resistant to proteolytic enzymes found in some fresh fruits including kiwi, papaya, pineapple, peach, mango, guava, and fig.

Basic Citrus Terrine Formula:

Because I used the example of the citrus terrine multiple times in our two agar videos, I’ve listed the formula and process below for reference. Please not that a working knowledge of calculating recipes based on the baker’s percentage is assumed.

  • 100% Citrus Supremes and Juice

  • 10% Sugar

  • 1% Salt

__________________________________________________

Add together the weight of above ingredients and then calculate the following:

  • .3% Agar (To set the gel)

  • .1% Locust Bean Gum (To keep agar gel from weeping)

___________________________________________________

  1. Drain liquid from citrus supremes.

  2. Combine in a pot with agar and locust bean gum.

  3. Bring to a simmer, simmer for 4 minutes, and then blend with an immersion blender.

  4. Heat citrus supremes in an oven or over a steamer to about 100°F/38°C. This is to keep the agar liquid from setting as soon as it hits the otherwise cold citrus segments.

  5. Combine hot agar liquid with warm citrus supremes in a mixing bowl, gently fold together, and place in a terrine mold lined with plastic wrap.

  6. Optional: place a flat tray on top of the terrine with weights. The pressure will cause the terrine to compact, yielding a more even texture.

  7. Allow to set in the refrigerator overnight.

  8. The next day, un-mold terrine, slice and serve.

  9. Note: The terrine can be pre-sliced and allowed to set in a flavored liquid to increase water retention and enhance overall taste. A good example would be apple or orange juice flavored with fresh vanilla bean, toasted spices, etc. The terrine will then swell with this liquid, giving it extra flavor and a “juicy” mouthfeel.


Agar Spherification

  1. Place a large, tall container of neutral flavored oil (like canola) in the freezer, until it starts to thicken, but pull before it solidifies (about 2-3 hours).

  2. Fill a squeeze bottle with hot agar liquid, and drip into chilled oil. As the agar drops to the bottom of the oil, it will gel into the form of a sphere.

  3. Pass oil through a strainer to remove agar spheres, rinse under cold water, and store in flavored liquid.


Agar Fluid Gel

  1. Set liquid with .3% agar by weight.

  2. Blend smooth in a blender, using an auger to move chunks around until it is evenly blended. Additional liquid or water can be added during the blending process to thin if necessary.

  3. Pass through a fine mesh strainer and reserve in an airtight container.


This “fluid gel” will have the consistency of a medium body mayonnaise, but will have a pure flavor, since the added viscosity is achieved by using a small amount of agar.

Conclusion

As you can see, agar can be used to achieve certain things gels and textures that simply isn’t possible with gelatin. For a complete break down of the difference between agar and gelatin, please watch the final video in this series, “Agar and Gelatin Compared.”

Further Information


Agar Gels at a glance

An Introduction To Agar Gels | Part 1 of 2

Watch Part Two Of This Video

Although agar has only recently emerged as a common gelling agent in modern western kitchens, it has been used in asian countries for centuries as their go-to gelling agent. A polysaccharide derived from red algae, agar is a great alternative to gelatin when a vegan or vegetarian gel is needed, or when attempting to gel liquids that normally will break down gelatin because of low pH, high alcohol, or proteolytic enzymes in fresh fruits.

One of the unique qualities of an agar gel is “hysteresis,” meaning there’s a large differential between agar’s setting and melting temperature (95°F/33°C and 175°F/80°C respectively). This makes it possible to serve a warm gel using agar, something that isn’t possible with traditional gelatin based gels.

Agar also sets rapidly above room temperature (95°F/33°C), within a matter of minutes, as opposed to gelatin, which takes 12-24 hours to fully set, once it’s core reaches 59°F/15°C.

The appearance of an Agar gel can range from clear to opaque, depending on what’s being gelled and the quality of the agar, and has a texture that ranges from firm to brittle. If too much agar is used to set a gel, the texture can become “crumbly” and unpleasant, especially since the heat from our mouth is well below it’s melting point.

However, an agar gel can be made less brittle and given an elastic texture with the addition of sorbitol or glycerol, usually around 1% by the weight of the entire gel being set.

One of the big advantages to using an agar gel is its low pH tolerance, with a range of 2.5-10. This makes it possible to set acidic terrines and gels, and is what we used last winter to create a seasonal citrus terrine with a pH of 3.2. This could not be achieved by using gelatin with its pH tolerance of 4-10.

Agar can also create what’s called a “fluid gel;” in this application it’s first allowed to set, and then blended smooth in a blender. When transforming a liquid with the viscosity of water into a fluid gel, usually .3% agar is added (based on the liquids weight), hydrated, allowed to set, and then blended smooth.

For more information, please refer to our next post in our Agar series, “How to Create an Agar Gel Plus Common Pitfalls.”

Further Links


Agar at a glance info graphic

Guide To Gelatin

Welcome to our gelatin resource page, we're you'll find everything you ever wanted to know about gelatin, and probably much more. Warning, the lecture videos listed below are extremely geeky and not for the faint of heart. But if you want to have a firm grasp on the properties of gelatin gels and how to use them, then this three part video series is for you. I've also included a gelatin infographic for your referencing pleasure.


Using Gelatin Sheets Vs. Powder
Part 1: The Basics Of Gelatin (Sheets Vs. Powder)
How To Use Gelatin (Hydration + Incorporation)Part 2: How To Use Gelatin (Hydration + Incorporation) Propertise of Gelatin Plus Pro TipsPart 3: Properties Of Gelatin Plus Some Pro Tips


Gelatin At A Glance (Click Image To Enlarge or Download Printable PDF)

Stella Culinary Gelatin Inforgraphic

Download This Info Graphic In PDF Format

Properties of Gelatin + Pro Tips - Part 3 of 3

Part One: The Basics Of
Gelatin (Sheets Vs. Powder)

Part Two: How To Use Gelatin
(Hydration + Incorporation)


In our previous two posts in this gelatin series, we discussed the various types of gelatin available, and how to properly hydrate and incorporate gelatin into a base liquid we wish to set. But whether or not gelatin is the proper ingredient for the application at hand depends greatly on the recipe’s ingredients, and the overall properties of a gelatin gel.

Texture & Appearance

Gelatin based gels have a clear, transparent appearance, especially when sheets are used instead of powder. It has the best flavor retention and release of any hydrocolloid (or water trapping ingredient) available.

Because its melting point (77-104°F/22-40°C) is pretty close to body temperature, gels set with gelatin have a soft, elastic texture. Yet this can also have its own drawbacks. Although gelatin doesn’t start to truly melt until it hits about 77°F/22°, its texture starts to soften at temperatures well below this. If you’re planning on serving a gelatin based dessert or appetizer in an environment that will expose it to warm temperatures over an extended period of time, then you may have difficulties with your item maintaining its texture.

PH Tolerance (4-10)

One of the drawbacks to using gelatin is it doesn’t work well in low pH environments, with a tolerance range of 4-10 (with 7 being neutral). This becomes an issues when trying to create an acid style gel, like a citrus terrine, which can have a pH of around 3.2. If the pH in your base liquid is below 4, then a gelatin gel simply won’t set.

Inhibitors

Gelatin gels do have some notable inhibitors you need to be aware of including salts, acids, prolonged heating, high alcohol concentration (above 40%) and protolytic enzymes found in fresh fruits such as kiwi, papaya, pineapple, peach, mango, guava and fig.

Of special note, the protolytic enzymes listed above are commonly found in meat tenderizers because of their ability to denature proteins (which also weakens a gelatin gel). However, bringing any of these fresh fruits to a simmer will deactivate these enzymes, making it possible to then gel with gelatin. However, if you’re trying to create a terrine using fresh pineapple juice and gelatin, you’re gonna have a bad time.

Promoters

Gelatin does have a “setting promoter” of note, transglutaminase, which works by cross linking proteins through a very strong bond. This allows the cook to create hot gels, including rice cakes and gnocchi that are held together by their liquid, instead of the standard “binding agents” such as egg or bread crumb. Common use percent is 0.5-1% transglutaminase by weight and 1% gelatin by weight (both percentages are based on the total weight of the mixture being set).

Further Information

How To Use Gelatin (Hydration + Incorporation) - Part 2 of 3

Part One: The Basics Of
Gelatin (Sheets Vs. Powder)
Part Three: Properties Of A Gelatin
Gel Plus Some Pro Tips


In our previous video post, we discussed the difference between gelatin sheets and powder, and settled on a use percent range of 0.6% on the low side to about 1.7% on the high (firmer) side. Now that you understand the various types of gels available to you on the market, it’s time discuss how to actually use gelatin.

What Is Gelatin?

Gelatin is a hydrocolloid (meaning it can suspend or trap molecules) derived from the collagen found in animals. Collagen is a simple triple helix of gelatin, and when heat and moisture are applied, the collagen unravels into three, separate gelatin strands.

In most common large scale productions, gelatin is extracted from pig skin (which is collagen rich), and dried into either powder or sheet form (see previous post to learn the difference between the two). Since diets restricting the consumption of pork exist, it’s important to know the animal source of the gelatin you’re using, which should be labeled clearly on the package.

Although bovine gelatin is widely available as an alternative to products derived from swine, true gelatin can only be extracted from animals, meaning it’s never appropriate to use when cooking for vegans or vegetarians. However, many good substitutes for vegan gelling agents do exist, the most notable being agar, which will be the subject of an upcoming video series.

How to Properly Bloom (Hydrate) Gelatin Powders and Sheets

As mentioned above, gelatin is a hydrocolloid, and every hydrocolloid, whether pedestrian (cornstarch, flour, and gelatin) or modern (xanthan gum, alginate or kappa carrageenan) will have a specific best practice for hydration and incorporation.

When working with sheets, “bloom” (hydrate) in cold water until soft. Once pliable, squeeze any excess water from the gelatin sheet, incorporate in the liquid you wish to gel, and heat to about 122°F/50°C until completely dissolved. Gelatin can be incorporated into a hotter liquid, but prolonged heating at high temperatures, especially those approaching a boil, will result in a degradation of the gelatin’s setting strength, leading to inconsistent results. That’s why I recommend heating your liquid to no more than 140°F/60°C once the gelatin, whether powder or sheets, is incorporated.

If starting with a hot liquid, simply bloom the gelatin sheets in cold water as discussed above, while allowing the base liquid to drop below 140°F/60°C before stirring in the softened sheets.

To properly incorporate gelatin powder, the approach will be different depending on if you’re starting with a hot or cold base liquid.  If starting cold, simply add the desired amount of gelatin powder to the base liquid, allow to hydrate for 5-10 minutes, and then gently heat to above 122°F/50°C, whisking occasionally, until completely dissolved.

If starting with a hot liquid, bloom powdered gelatin in a separate, complimentary cold liquid, taking into account the weight of both the hot liquid base and cold blooming liquid when calculating how much gelatin powder to use. Combine hot and cold liquid together, whisking until the gelatin powder is completely dissolved and applying additional heat if necessary. Note: even if you’re starting with a boiling hot liquid, incorporating the cold liquid plus bloomed gelatin powder shouldn’t be an issue, since once combined, the overall temperature of the liquid will drop and won’t stay hot enough to be measurably detrimental to the gelatin’s setting strength.

Because of the two step process required for incorporating gelatin powder into a hot liquid, I think this is another argument for using sheets, which have the added benefit of superior clarity and flavor.

Allowing Your Gelatin Gel to Set

Gelatin is a slow setting gel which sets at around 59°F/15°C, and needs to be kept at refrigeration temperatures for at least 6-10 hours before solidifying. Making gelatin gels at least a day before serving is extremely prudent, since gelatin can continue to set over a 24 hour period.

In our next post, we’ll discuss the specific properties of gelatin (including inhibitors and promoters) as well as best practices and common pitfalls.

Further Information

 

The Basics Of Gelatin (Sheets Vs. Powder) - Part 1 of 3

Part Two: How To Use Gelatin
(Hydration + Incorporation)
Part Three: Properties Of A Gelatin
Gel Plus Some Pro Tips


In this three part video series, we discuss one of the most common gelling agents used in the western kitchen, gelatin. To lay a firm foundation, I thought it was best to start our discussion with the two major types of gelatin available to cooks, sheets and powder.

Gelatin Sheets vs. Powder

Gelatin sheets are almost exclusively used in the professional kitchen, versus powder, which is more common in supermarkets. Yet with the advent of professional level cook books, gelatin in sheet form is quickly becoming easier to find. If you’re interested in working with gelatin sheets but your local supermarket only carries powder, you can easily purchase them on Amazon.com, in their various grades. If purchasing gelatin sheets, I would recommend the silver grade, since they’re the most common in professional recipes and have an intermediate level bloom strength. This makes them easy to adapt to almost any recipe without much adjustment required.

The subject of gelatin sheets can get confusing due to their separation into grades, which are bronze, silver, gold and platinum. Each grade is associated with various “bloom strengths,” or their ability to set a gel. This means that gram for gram, platinum will set a stronger gel than gold, silver a stronger gel than bronze, etc. The bloom strength for each grade is:

  • Bronze: 125-135

  • Silver: 160

  • Gold: 190-220

  • Platinum: 235-265


Now I must admit, knowing the bloom strength of various “grades” of gelatin is pretty useless. Yes, it’s true that silver will set a more “rigid” gel than bronze, but the same results can be obtained by simply using more bronze sheets.

To compensate for the fact that one sheet has a higher bloom strength than another; each grade of gelatin is weighted differently, making their overall ability to set a gel, more or less equal. For example:

 

  • Bronze: 3.3g

  • Silver 2.5g

  • Gold: 2.0g

  • Platinum: 1.7g


So this leads to the natural question of...if their gelling powers are pretty much the same, then why are their different grades of sheets in the first place?

And what is the answer? I have no idea. In fact, I’ve been pulling my hair out trying to figure this whole thing out, and the only thing I can think of is to make volumetric recipes easier to standardize, meaning once you get used to a particular sheet, you stick to it, and you know that x amount of sheets per cup of liquid is what your prefer for a particular result.

If it helps any, silver with a bloom strength of 160 and an average weight of 2.5g, is the most common grade of gelatin sheet found in the professional kitchen; so if you’re going to make the switch from powder, I think silver is your best option.

Professional chefs prefer sheets over powdered because the former will set a clearer, cleaner tasting gel as compared to the latter, which can sometimes have anti-caking agents and other impurities, resulting in a more opaque gel with a “dirtier” flavor.

But here’s the silver lining that you need to pull from this whole discussion: the general use percent for any given form of gelatin runs from about .6% on the low side to 1.7% on the high side. This makes it easy to find your gelatin’s sweet spot and is another great argument for why you should always be standardizing your recipes by weight (good scales are only $25, so stop procrastinating!).

As we discussed in this video, I recommend starting at 1% gelatin by your liquid’s weight (purely because it’s easy to calculate), and then scale the gelatin up or down accordingly, of course, keeping notes as you go.

In our next video post, we’ll talk about how to properly use gelatin, including hydration, melting, and how to properly incorporate both gelatin powder and sheets into your recipes.

Further Information

Ahi Sashimi, Cantaloupe "Caviar," Dehydrated Sesame Oil | Video Recipe



The video above will take you through the process of creating and plating our ahi sashimi dish that we are currently serving at Stella. If you've already watched the video and just need a quick refresher, you can refer to the step by step pictures below. For more information on acquiring specific ingredients or supporting recipes, please see the notes section at the bottom of this post.

Stella's Ahi Sashimi Plate Up

Start by making cantaloupe caviar using basic inoic spherification. Remember, the caviar has to be made to order or it will become a hard, rubber pebble with little flavor.

Next, lay out three strips of cucumber that have been thinly sliced lengthwise on a mandolin and pickled in a basic pickling liquid. Using this recipe, allow the sliced cucumbers to "marinate" in the pickling liquid for at least an hour before using. Dabbing them on a clean kitchen towel before plating will wick off any excess moisture and vinegar, giving you a better plate presentation and flavor.

Next, slice the ahi loin that has been fabricated into saku block. Here we're serving a total of 4 ounces of ahi sashimi. You can adjust this portion up or down depending on what you feel is appropriate.

Drizzle some home made citrus teriyaki directly on top of the sliced sashimi, and make a decorative pattern on the plate. The pattern should have some symmetry with equal distancing on all sides in relation to the edge of the plate.

Lay three, drained pickled cucumber strips in the middle of the plate, with each strip slightly overlapping the last. Pay attention to the center of the plate, and make sure there is an equidistance between the cucumber and rim, both with horizontal and vertical placement.

Place a strip of seaweed salad down the center of the cucumbers (making sure to leave some of the cucumber exposed), then lay the sliced ahi on top. Top with the previously made cantaloupe caviar that has been drained and rinsed.

Season ahi and cantaloupe caviar with a small sprinkling of fleur de sel. Garnish the plate with a spoonful of dehydrated sesame oil in opposing corners and serve immediately.


Additional Information



This post is part of our ongoing Completed Dish Video Series, which shows you how to combine multiple techniques into a restaurant quality dish. For more information, you can also view our How To Cook Video Index.

Cantaloupe Caviar - How To Make Faux Caviar Using Basic Ionic Spherification

how-to-make-faux-caviar.jpg
Ionic spherification was first introduced by Ferran Adrià of El Bulli. They would serve a beautiful apple "caviar" in a caviar tin, which at that time was absolutely mind-blowing. Because the overall technique is fairly simply, "faux caviar" quickly became many-a-cook's first foray into hydrocolloids and modern cuisine (also commonly referred to as "molecular gastronomy"). Although this recipe is to demonstrate the cantaloupe "caviar" we make specifically for our ahi sashimi, the ratios and techniques are fairly universal.

White Chocolate Panna Cotta

This is a quick and simple recipe for a white chocolate panna cotta that I've had a lot of success with serving over the years. One thing you need to keep in mind is that white chocolate can deaden the palate due to its fat content, so it's important to pair this dessert with something that will help cut the fat. Some of my favorites are black pepper, citrus sauces, or the Bing Cherry Compote linked in the recipe notes.
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