I announced on Instagram that we were going to turn page. Enough with baking, at least for a while, we won’t turn the oven on ;). Today, I am going to present you the most summery food: gelato.
I don’t know you, guys, but for me a summer without ice cream is as a sky without stars (all right, very poetic today). OK, I know, Tuesday supposes to be the day of the nerdy/ scientific explanations, therefore, I will spare you memoir today :P Let’s talk how gelato is made, instead. Or better, let’s talk how experts make it. In the next posts, then, I will explain how you can make it home.
So, gelato, we said. From the chemical-physical point of view, gelato is an emulsion (again!). I told you that the discussion on colloids was far from being over! ;) Briefly, gelato is an emulsion where air bubbles are suspended in a partially frozen liquid. This is the simple definition. Actually, things are a bit more complex, as often gelato consists of a custard, which is already an emulsion. You understand, now, the complexity of the system.
The colloidal system of gelato is similar to that of whipped cream: the fats take contact with the air bubbles, while the milk proteins act as emulsifiers and bridge the fats with the water phase, where the sugars are dissolved.
Gelato is made of milk, cream and sugar. Other ingredients can be added to this base as fresh fruit, dried fruit, eggs, and chocolate, to create various flavors.
Experts commonly classify gelato as follows:
Fruit gelato: they contain fresh fruit (e.g. strawberries, pear, raspberries…)
Creams: they might contain eggs (e.g. custard, stracciatella, malaga...)
Sorbets: they do not contain neither milk nor cream, but they can be added of albumen
Preparation of gelato
It consists of different steps:
It consists of mixing all the ingredients. Actually, it is not as trivial as it might sound. Sometimes, we just need to blend all the ingredients (e.g. when preparing fruit gelato), but others we need to incorporate solid foods as chocolate chunks or dried fruit. The addition of solids should be done when freezing is halfway. In the liquid mixture, the solids will precipitate, while they won’t incorporate in the frozen gelato.
This process is commonly used for both artisan and commercial ice creams. I personally use it just for those gelato containing eggs, but I do not follow the complex protocol used by the experts. I simply bring the custard almost to boil to make the gelato safer form the microbiological point of view. However, the industry follows strict SOPs of pasteurization that is applied to all types of mixtures.
There are several types of pasteurizations. The classic one consists in bringing the mixture at 85 ˚C for 5 sec to then cool it down around 4 ˚C. However, there are also pasteurizations carried out at lower temperatures for longer time intervals.
UHT treatment is often used in the production of industrial ice creams. In this case, the mixture is brought a bit above 135 ˚C, for a few seconds. This procedures modify the protein structures, improving their emulsifying properties and allowing obtaining a smoother gelato.
Simply, the gelato mixture is blended. I usually blend only the mixtures containing fresh fruits, but often the experts do that with all types of gelato to obtain a finer texture.
I never did it, mea culpa :P During this phase, the mixture is let rest around 4 ˚C, for a time that might vary from 12 to 72h. This procedure allows cooling the mixture down and hydrating the solid parts. The final result is a denser and creamier gelato.
The mixture is finally introduced in the gelato machine, were rotating paddles help the mass with incorporating air, under constant freezing. This step require the use of a good machine. Forget to place the mixture in the deep freezer and then whip it. Seemingly, using machines with the bowl that must be pre-cooled won’t work.
Gelato must then be transferred in the deep freezer and stored around -18 ˚C for a couple of days. Experts use a blast cabinet that allows achieving temperatures of -18/-20 ˚C in very short times. The use of blast cabinets limits the formation of large ice crystals and allow obtaining a creamier gelato.
That’s all folks, at least for today. But I must warn you, we just started. In the following posts, we will discuss how to dose all the ingredients, how to select the right sugar and the fats. We will see also how additives can help with improving the texture of gelato.
We will see on Thursday for the usual recipe! :)
L. Di Carlo, Tradizione in Evoluzione, 461-463, Chiriotti Editori
H.D. Goff, Colloidal aspects of ice cream—A review, International Dairy Journal, 7, 1997, 363-373