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.
How To Use Gelatin (Hydration + Incorporation)
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.
Properties of Gelatin + Pro Tips
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.
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.
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).