> The one remaining problem relates to use of pasteurized, homogenized milk (as
one would get from the store). I am less familiar with it than the fresh raw
goat’s milk I use, but the processing alters the protein structure, and may
cause problems establishing a firm curd. Some recipes call for purchasing a
solution from a cheese making supply house, and adding “1/2 to 1 teaspoons” per
gallon (5-10 mL).

The "solution" here is calcium chloride (CaCl₂) and the standard concentration
is 30% by weight (the article says 0.02%).

CaCl₂ is needed to replenish the calcium lost during pasteurisation, and
also during refrigeration. Basically any change to the temperature of milk will
cause the calcium in the milk to precipitate which means it is less available to
the rennet enzymes. I don't pretend to understand the chemistry any further than
that, but that's why we add CaCl₂ to cheesemaking milk.

On the other hand, CaCl₂ doesn't do anything for homogenisation. Homogenisation
basically pushes milk through a very small funnel with great force so that the
fat globules in the milk cream burst and become more evenly distributed
throughout the milk emulsion (milk is an emulsion!). This is done to consumer
milk to avoid having the cream float to the top that, legend has it, consumers
find icky. More honestly, the reason that milk is homogenised is to standardise
its appearance so that its fat content is not immediately obvious, leaving the
producer free to skim off any "excess" fat and standardise fat content to 3.5%
on the dot, while the rest of the fat is sold as cream. Skimmed milk is the
byproduct of the same marketing incentive.

In any case, pasteurised, homogenised and standardised milk can be used in
cheesemaking just fine and indeed most commercially produced cheese sold today
anywhere is made that way, both for public health reasons and for marketing and
regulatory reasons (for example, regulations for PDO cheeses typically specify
the minimum fat content of cheese, so cream must often be added or removed to
meet them). On the other hand, setting a curd gets progressively more difficult
the more such processing is applied to milk.

Pasteurisation is really the mildest treatment one can apply and it doesn't
really hurt if the milk is fresh and good quality milk to begin with.
Pasteurisation temperatures and durations are expressly tuned to avoid damaging
the milk proteins (contrary to what the article says) while ensuring the total
destruction of all vegetative forms of bacteria known to cause disease (the
standard of 63°C for 30' is calculated to exterminate 100% of individuals of
Coxiella burnetii with 97% accuracy, C. burnettii being the most heat-tolerant
disease-causing bacterium we generally expect to find in raw milk). In my
experience, home-pasteurised ewe's milk doesn't even need CaCl₂ to set the
firmest of curds, rather the opposite, the problem is to keep the curd from
coagulating too quickly (at least that is the case with sheep-derived rennet;
bovine rennet tends to act less immediately on ewe's milk for some reason I
don't understand. It's the same enzyme?). That's because of the highest amount
of protein in ewe's milk that makes for a firmer curd and greater yields. Cow's
and goat's milk are slightly thinner and they need more care to get all the
variables right.

Homogenisation on the other hand, makes it much harder to set a firm curd. In my
experience, making cheese at home with homogenised (cow's) milk from the
supermarket, I always get a thinner curd and have a lower yield than normal, so
I avoid it. There's nothing I know of that can be done to improve homogenised
milk. How the large factories do it, I know not, but for anyone who doesn't have
a factory the best is to stay away from homogenised milk if you're making your
cheese at home.

Also: don't make cheese with raw milk. You'll regret it. Trust me.