We had a day out today, and watched some small scale mozzarella cheese making in the Istituto Sperimentale Lattiero Caseario/Institute of Dairy Science in Lodi, not far from Milan. The lab is equipped with a cheese making facility and over the course of our day-long visit, the master cheesemaker whipped up a batch of mozzarella and a little ricotta for us.
Mozzarella curd: whole milk from the institute’s dairy farm has been acidified (lowering the pH from 6.8 to 5.85) with citric acid (interesting to see it’s useful for more than cleaning one’s kettle).
Mozzarella curd: cut, drained, cut and then left to drain again.
Mozzarella curd: cut, drained, cut, drained and now cut again.
Mozzarella curd: cut, drained, cut, drained, cut, drained and then put into the basin; cut once again. Then some hot water (around 90 degrees c) is added and the stretching begins.
Hand stretching the curd – a slower, lower-yield way to make mozza. The advantages are that any problems with texture can be dealt with right away, so you end up with a better quality cheese. But you’d go bust doing it: the volume of milk you need to process to make mozzarella, together with the greater loss of milk solids into the liquid, and the slower processing (man ain’t no machine) just aren’t cost effective these days.
Stretching the cheese; shaping it into balls. Stretchy stuff with characteristic threads (elongated casein strands, eh?): practical heat and chemistry.
Hand-adjusting the steam-heated vats to start making ricotta from the mozzarella whey. Ricotta, we now know, means ri-cotta, or re-cooked/twice cooked. (Want to make your own? Here’s an illustrated guide.)
The whey starts off at the same pH as the mozzarella curd (around 5.85 – lowered from milk’s natural pH of 6.8). Sodium hydroxide was added in order to raise the pH to what’s needed for ricotta, between 6 and 6.5; the pH is regulated and if it goes too high, more citric acid can be added to lower it again. In the process we watched, there was a mistake – the pH gauge was too close to the sodium hydroxide when that was added, and gave a faulty reading, so it never quite worked out while we were watching. Which was instructive: we saw the effect of curds that were too small to bind properly for ricotta. However, under optimum conditions, the whey begins to coagulate and – after adding milk (around 6% in this case, although up to 20% might be used) – the foam needs to be skimmed off. The ricotta is then poured into baskets to drain and set, and is used most often in pasta and cake fillings.
In one of the labs: Roberto Giangiacomo tells us about a piece of equipment called ‘the sniffer’ while Richard Gere and Clive Owen look on.
