January 1, 2004
When I think of fluffy, light-textured desserts, whipped cream, meringue, chiffon, mousse and frozen desserts like semifreddo come to mind. I also think about why these types of desserts appeal to so many people -- they appeal to the hedonists among us.
Whip it good
In the distant past, chefs created fluffy, light-textured desserts via physical, manual methods such as a wire whip and chilled copper bowl, usually from whipping cream. Adding sugar in meringue and sugar and yolks in custard provide stability and texture. The idea was to incorporate air into a tasty medium, giving it a unique texture so that it may be enjoyed by more than just our taste buds. A light, fluffy whipped dessert is as visually stimulating as it is fun to eat, not to mention the aroma that it releases because it is a much-less-dense product than, say, a cheesecake. This sensation and unique mouthfeel is attributed to the physical nature of the product.
Chefs and cooks of old may not have known the science behind the taste sensation of a whipped dessert, but they knew that it delivered. The founding fathers of Western cuisine who lived in the 1800s and early 20th century, such as Marie-Antoine Carême (1783-1833), Charles Ranhofer (1836-1899) and Georges-Auguste Escoffier (1846-1935), discovered that delivering a unique, light mouthfeel was very important after serving a five- or six-course meal.
Although these chefs did not know that their whipped confections resulted from complex networks of protein films or matrices of suspended lipid molecules in liquid media, they did know how to create light, fluffy desserts, and how to improve upon them. For instance, adding a touch of cream of tartar to egg whites made the whipped meringue more stable, and using a well-chilled copper bowl was the best choice for whipping cream.
Today's research chefs not only have the know-how of the countless chefs who went before them, but also the scientific knowledge of why things happen -- that the protein and/or fat-and-liquid matrices entrap air bubbles, and by manipulating the ingredients and mixing, you change these structures to provide foams of varying textures and stability. We know that the foaming properties of proteins can be influenced by protein concentration, pH, temperature, salt, sugars and fats. For example, the cream of tartar mentioned above helps to stabilize the foam because acids alter the structure of protein molecules. The stray copper from a copper mixing bowl does the same by forming a molecular complex with the protein.
Today's product designers also have access to various ingredients, such as gums, modified starches and stabilizers, that make commercializing a high-quality dessert easier than ever. As a research chef, I can quickly ascertain which specialized functional ingredient will help solve a problem with a whipped dessert. Does it involve stabilizing a whipped oil-in-water emulsion with an emulsifier, or making a lower-fat whipped dessert hold up better with a fat-replacer type of ingredient?
Today's environment of specialized ingredients that solve specific problems makes it easier -- and more acceptable -- to create a taste-tempting whipped treat that is sold in the local grocer's freezer or refrigerated section. Prior to the technological advances of recent years, it would have been unheard of to sell many of these whipped finished products in the retail market.
A whipped product delivers flavor in a different way than a heavy, dense one. By incorporating air into a liquid or semisolid, the surface volume of the product increases, and therefore, the aromatic quality of the finished dessert intensifies. A very basic way of testing this theory is to take a drop of vanilla extract, place it on the tip of your tongue and taste. What is the sensation? Take a 10-minute break and drink some water and eat a cracker.
Now, take one drop of the same vanilla extract and put it on a spoon. This time, breathe it in to your mouth, taking in a copious amount of air along with the drop of vanilla extract. Notice any differences with the flavor -- any subtle nuances of cooked sugar, caramel notes, vanillin, etc.? Does the taste "expand" in your mouth?
This is what happens when consuming a light-textured dessert. Air mixes with the cream, sugar, egg yolks, flavorings and other ingredients to make an extraordinary taste experience. You might even conclude that, calorie for calorie, a whipped dessert provides a bigger "bang for the buck" than other choices.
Compared to the entire history of food in restaurants, the use of concentrated flavors in "lighter" whipped desserts is a relatively new development in the past 75 years.
We now know why these products look and taste the way they do. Now let's examine the methods and science behind some well-known whipped confections.
Meringues of varying degrees
Several types of meringues feature in today's desserts. To create the most common, a chef whisks egg whites into a soft-peak foam and then gradually adds granulated sugar. Whisking causes the protein in the egg whites to unfold, forming films that trap the air bubbles, and the sugar stiffens the foam. By varying the amount of sugar in the final mix, the chef controls how hard or soft the final product will be. As the mixing time increases, the bubbles become smaller and more numerous; this increases the volume and makes a more-stable structure. (A beaten egg white can increase six to eight times its original volume.) However, overbeating will cause the proteins to lose their ability to hold the small air bubbles causing it to lose volume or collapse. Finally, cooking (baking) a meringue will set the structure. During heating, the air bubbles expand, causing the volume to expand until the white's protein network surrounding the bubbles solidifies.
We can make another type, the Swiss meringue, by combining unwhipped egg whites with sugar and gently warming the mixture to 100°F. The chef then whips this mixture until it is cool and stiff, with the resulting ratio of sugar to egg whites again determining how hard or soft the final product will be.
To make Italian meringue, slowly pour a hot (240?F) sugar syrup into the bowl of soft-peaked, whipped egg whites as they are mixing on medium speed. This will denature some of the protein in the egg-white mixture, partially setting it and ultimately making a more-stable meringue. This meringue can form the base of other confections, such as Italian or French buttercream icing. Incorporating various flavoring ingredients to this mix will intensify the final product.
A word on mousses
The term "mousse" applies to a variety of light dessert creams not easily classified elsewhere. Mousses can be made either sweet or savory, depending on the ingredients. Usually, dessert mousses are of the sweet variety.
A mousse is similar to a Bavarian crème, which is a custard, or a chiffon, in that it is light and airy due to the addition of whipped egg whites, whipped cream or both, in some cases. It is generally softer than the Bavarian or chiffon and can contain some form of gelatin or gum. Mousses usually are too soft to mold into a semirigid form, as you would mold a gelatin dessert. To get a desired shape, the best method is to pipe the mousse into or onto the final dessert presentation and garnish just prior to service.
Many choices are available when making a mousse. Chocolate and fruit are some good starting points; your choice here will determine whether or not the base recipe will require gelatin.
To properly prepare a mousse, after creating a "base" of melted chocolate, custard or puréed fruit, add a bit of softened gelatin or gum to the warm base. After the gum or gelatin has dissolved into the base, fold in the whipped egg whites while the base is slightly warm -- this increases the stability of the egg whites (see Italian meringue method). After the mousse has cooled down to a refrigerated temperature, it is time to add the whipped cream.
The recipe calls for adding the egg whites first because the mixture is still warm; adding the meringue at this point further stabilizes the mousse, because some of the meringue will denature and set. If this procedure is reversed, i.e., adding the whipped cream before the egg whites, it would deflate the cream, and the resulting product will be gritty, grainy and overall, sub-par. This is why chefs must follow procedures to create the best product. Everything happens for a reason, and often the science of what occurs during the preparation of any whipped dessert is the primary driver of why we do what we do in the order in which it is done.
Frozen desserts, semifreddi and such
Although you might not think of ice cream, gelato, sorbets or semifreddi as whipped creations, nothing is further from the truth -- all contain a certain amount of added air. Without the air, these frozen desserts would be icy and impossible to scoop by hand. The term "overrun" refers to how much air a manufacturer whips into ice cream during its creation; it's determined by the percent increase in volume of ice cream greater than the amount of mix used. Superpremium and premium ice creams tend to have low overrun (and higher fat content) than regular ice creams.
Along with ice cream, frozen-fruit purées, or sorbets, and sherbets (fruit and dairy products) are frozen as air is incorporated into them, which gives them their light texture. Sugar, added as a sweetener, also acts as a functional ingredient by creating a product that is still soft while frozen.
A semifreddo is a mousse or custard that is prepared and then frozen without being churned. Its light texture is due to its preparation method, not the freezing portion of the process.
The frozen-dessert category offers one unique eating characteristic: People consume them frozen, whereas most whipped desserts are eaten chilled. This added, unique dimension offers both rewards and challenges.
Consider the first time you tasted delicious, cold, refreshing ice cream -- what an experience! The minute that semisoft, textured, sweet spoonful of ice cream passed your lips, you were hooked. As it melted in your mouth, you could taste the flavors incorporated into the mixture.
Therein lies the challenge: Since the dessert is frozen, the flavors are muted. Developers need to take great care in creating an ice-cream flavor that delivers what the package says.
Liquors, inclusions and liquid flavors are ways to incorporate flavors into a frozen dessert. However, the use of a high-proof liquor must be monitored due to the fact that it lowers the freezing point of the ice cream. The more alcohol a frozen dessert contains, the greater the chance that it will not freeze as needed. One way to overcome this is to use concentrated flavors that replicate their alcohol-containing counterparts at the local liquor store.
As you can see, much more science and technology is involved in creating an authentic, stable, whipped dessert than you may have originally thought. The use of proper methodology, ingredients and experience has a large influence on how the final product will turn out. Look for the trend of healthier eating to continue worldwide, driving the research and development of more tasty, lighter and healthier whipped products in the future. Bon appetito!
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