I recently held a class featuring Italian Desserts. One of the dishes we made was Panna Cotta. This is a wonderful light and silky egg-less custard that relies on gelatin to set up. I like to use something called Leaf Gelatin rather than powdered gelatin. Since many of us have never seen or used leaf gelatin, I thought I would discuss it in this Cooking Tip.
Let’s start with what is gelatin. It is a thickening agent that causes food items to form a jelly-like substance. It is odorless, tasteless and colorless. It is pure protein derived from the connective tissues of animals. I will discuss vegetarian alternatives in a subsequent Cooking Tip.
There are two forms – powdered (aka granulated) and leaf (aka sheet). Although all powdered gelatin is the same, there are different strengths of leaf gelatin. There are four grades. From weakest to strongest, they are bronze, silver, gold and platinum. The sheet size is adjusted with the different strengths. The stronger gelatin has a smaller sheet size. This means that sheet-for-sheet, they will have similar setting properties. One sheet of gelatin will generally set around 100 ml (3.4 ounces) of liquid to a soft set. The most common in professional kitchens is the silver grade. It is also what I use and would be a good choice if you wish to try it.
Professional chefs like leaf gelatin because they think it results in a clearer and cleaner result. I find it gives the final product a smoother and silkier texture.
All gelatin needs to be rehydrated before using it. This is called “blooming” the gelatin. In the case of powdered gelatin, it is normally sprinkled over a bit of cold water or other liquid. If your recipe doesn’t specify how much liquid, use about ¼ cup liquid for every 2 teaspoons of powdered gelatin. After it sits for 5-10 minutes, the granules absorb the liquid and swell up. After that step, the gelatin is melted by stirring it into the hot liquid of your dish.
Another method that some recommend is to whisk the gelatin together with the sugar (or other dry ingredient) in your recipe before mixing it into the liquid. The supposed advantage of this is that mixing it with a dry ingredient separates the granules so they can rehydrate more evenly.
Leaf gelatin is hydrated by putting in a bowl and covering with cold water. Once the sheets are soft, they are squeezed to remove excess water and then added to your hot liquid.
Many ask how to substitute powered gelatin for leaf. There is much debate on this issue with recommendations varying between 3½ sheets to one envelope of powdered gelatin to as much as 5 leaves for one envelope. Since one envelope of Knox gelatin (the one we most commonly have in our pantries) contains about 2½ teaspoons of gelatin, you will often read to use 1 tablespoon of powdered gelatin for every four sheets of leaf gelatin as it is sort of an average. If you use a different brand of gelatin, you will need to measure to make sure you are using the proper amount.
Gelatin is a great ingredient but it does not work in all situations. It does not hold up well in an acidic environment. For setting gelatin, the ideal pH is between 4 and 10. Because of this, gelatin is not the best choice for a citrus dish as the pH will be less than 4 and it will not set.
Temperature is also another concern. If the temperature of your liquid is too high when you add the hydrated gelatin, it can interfere with the gelling ability. You do need to heat the liquid to about 120°F to ensure the gelatin is fully dissolved but you do not want to go over 140°F. So, let your hot liquid cool a bit before adding the gelatin.
For gelatin to set, it needs to cool to about 59°F and needs to be kept there for 6-10 hours. That is why many of these dishes recommend that you make them the day before or at least the morning of the day you are going to serve it.
Another temperature-related concern is that gelatin starts to melt at about 77°F and it will soften at temperatures below that. Keep this in mind when serving a gelatin-based dish so the texture is not compromised by too high of an ambient temperature.
Other inhibitors to proper gelation include salt, high alcohol content (above 40%) and proteolytic enzymes such as are found in fresh kiwi, papaya, pineapple, mango, peach, guava and fig. These enzymes, though, are inactivated by simmering. This means you can set a fruit-based dessert with gelatin but only if you first bring it to a simmer, not if you are trying to use fresh fruit juice.
If you are not someone who is on friendly terms with math, you may want to ignore the remainder of this Cooking Tip. For those of you who might want to create your own gelled dish without a recipe, there is some math that you need to know. You will also need a food scale as this is all based on weight, not volume.
You need to be aware of something called “Use Percentage”. This tells you how much gelatin you need to add to a certain amount of liquid to get a proper gel. For gelatin, the use percentage is 0.6% to 1.7% of the liquid’s weight. For example, if your liquid weighs 1000 grams, the amount of gelatin required would be between 6 (0.6%) and 17 (1.7%) grams. For ease of use, just take a number in the middle – 1% – and that will give you 10 grams of gelatin is required to gel 1000 grams of liquid.
Have you ever tried leaf gelatin? Let me know what you think of it. If you haven’t tried it and want to, you will most likely need to get it online. I use the product from ModernistPantry.com but there are others out there. Stay tuned for a discussion of vegetarian alternatives.
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