Ricotta (Whey Cheese Set by Heat)

Name: Ricotta (Whey Cheese Set by Heat)
Prep time: 15 min
Cook time: 55 min
Total time: 1 h 10 min
Yield: 6 servings
Cuisine: Italian
Ingredients: 4 L whey; 1 L whole milk; 1 tsp salt; 30 ml lemon juice; 100 ml double cream

Italy's fresh whey cheese, made by reboiling the liquid left over from making something else. This site already has three ways to set milk and all three set the same protein, casein: acid in rasgulla, a calcium salt in douhua, rennet in mozzarella. Ricotta sets the other one, the protein all three of them leave behind in the whey. So what does the setting here is heat rather than acid, and the raw material is what the cheesemaker poured away. The name means recooked.

Ingredients

6servings

The traditional route (whey)
whey · left from making mozzarella, paneer or janu-siers. The fresher and the sweeter, the better4 L
whole milk · optional but effectively standard: whey alone gives a painfully small yield1 L
salt1 tsp
lemon juice · or white wine vinegar. Not needed at all if the whey has been left to sour overnight30 ml
Optional
double cream · gives a softer, richer curd100 ml

Steps

Strain the whey once through a fine sieve lined with muslin. It carries stray crumbs of casein from the cheese you just made, and those are what stick and scorch on the base of the pan.
⏲ 10 min
The traditional route stops here and leaves the whey at room temperature for 12-24 hours. It sours on its own, the pH falls, and then no added acid is needed at all. If you have not got the time, skip it and use the lemon juice at step 4.
Put the whey, milk and salt in a wide heavy pan and bring it up slowly, over a low heat. Stir occasionally until about 70C so nothing catches, then stop stirring.
⏲ 30 min
At 85-90C add the lemon juice in two goes, pouring it down the side. With no thermometer: the surface shivers and steams but never bubbles. Do not stir from here on -- a network that has just begun to form will disperse if you stir it, and it does not re-form.
Drop the heat right down or take the pan off, and leave it 10 minutes. White curds rise and the liquid below turns clear and pale green: that is done.
⏲ 10 min
Lift the curds out with a slotted spoon into a cloth-lined sieve or basket. Lift, do not pour -- tipping the pan breaks them up.
⏲ 15 min
Let it drain 1 hour. The longer it drains the firmer it gets, so drain it briefly for something to spread and overnight in the fridge for a filling.
⏲ 60 min

Tips & Variations

Variations

Whole-milk ricotta: what most shops now sell. No whey at all -- 2L milk, 500ml double cream and 60ml lemon juice, set at 85C. Softer, richer and a far better yield, but what sets is casein, so it is really closer to the cheese in rasgulla. It is not the thing the name describes.
Sheep's whey: the standard in Sicily and Sardinia. More protein than cow's, so a better yield and a fuller flavour. The ricotta in the photograph is Sicilian.
Ricotta salata: salted, pressed and dried, then grated over pasta.
Ricotta al forno: baked until the surface browns. Ricotta forte is the Pugliese one, fermented for months into a sharp, salty spread.
If you use cream: add it with the milk at step 3. Milk fat gets between the proteins and keeps the network open, which is why it sets softer.

Tips

It is a different protein. Milk protein comes in two families: casein, which floats in clusters called micelles, and the whey proteins, which are dissolved singly. The acid in rasgulla, the calcium salt in douhua and the rennet in mozzarella all act on casein alone. So the whey those three leave behind still holds every bit of the other family, and ricotta is what sets it.
Heat does the setting, not acid. Whey proteins are folded into globules, and heat unfolds them. From about 75-80C they open up and the opened ones stick to each other into curds you can see. The acid is a supporting player that helps them clump -- which is why pouring vinegar into cold whey does nothing at all.
In brunost this same thing is the failure. The Norwegian brown cheese boils whey down to drive the water off, and its page says that "whey protein coagulates around 75-80C, and coagulated protein sticking to the base is where the burning starts", and that curd left in makes the finished cheese gritty. It strains and avoids exactly what this dish is made of. Same whey, same temperature: an accident to be prevented there, the product here.
Never a hard boil. Boiled, the curds tighten and go squeaky and dry, and protein baked onto the base gives the whole batch a scorched taste (dairy and heat).
The yield is meant to be small. Four litres of whey plus a litre of milk gives 250-350g. Whey protein is only about a fifth of the protein in milk, which is why ricotta has always been a by-product rather than a thing you set out to make.
Eat it the day you make it. Almost no salt, almost no acid and a great deal of water: two or three days in the fridge is the limit. That is also why the Roman agricultural writers never mention it -- it could not reach a city market, so the shepherds who made it ate it.
The whey comes from this site. Make mozzarella and its own page tells you: boil the rest again with acid and you have ricotta. Janu siers and rasgulla leave you the same few litres.