Not to be too negative, but virtually every recipe also has practically a random amount of rennet. You see recipes with 60-100 IMCU per liter and the author seems to have no idea why they are using that amount. The thing about cheesemaking is that it's very difficult not to end up with *some* kind of cheese (at least as long as you aren't making quick mozzarella...). The vast majority of recipes I see, whether online or in books, make no sense to me at all. More than one famous recipe author has a "buttermilk blue" recipe where they add something like 1/4 of the total milk as buttermilk and *then* add a mesophilic culture for good measure. I honestly think that most people have no idea why they are adding the ingredients that they are adding.
The thing about culture amount is that adding too much or too little doesn't ruin your cheese. It just makes a different cheese than you are trying to make. If you add too little, your rennet is going to work more slowly. If you aren't checking flocculation, then you will cut the curds too early. This will result in more fat and whey escaping. You'll drain too early, but because you cut early, the curds won't be too moist. The pH is high which will spare calcium, leading to a very pliable curd. At worst, if you blindly pile on the weight, it will close the rind and it won't drain well. But likely you'll be OK and since the curd retains a bit too much whey, it will actually acidify faster than it would have done and you'll be at about the right pH when it comes time to salt. The curd compositions is going to be *very* different than what you were aiming for, but it will be good cheese.
In the other direction, your rennet works faster. You get more fat and whey in the curds. You cut late, but because the acidity is high, it drains faster. If you are *really* over, the curd will be so firm that you tear it when cutting, letting it drain even faster. You drain late and the pH is low, so it's harder to press. You'll notice that as well as having to much culture (and too much rennet) in the recipes, they also press with too much weight. Well, if you've overshot your pH and you added too much rennet you might need that weight. Again, it drains quickly and so the pH drop slows. You end up at about the right pH at salting and you get a good cheese. However, worlds apart from the other extreme.
If you don't know what the cheese is supposed to taste like ahead of time (the vast majority of these authors seem not to have much experience with the original traditional cheeses -- they just want a few hundred recipes in their book), then it will be good cheese and you'll think, "I'm a genius".
Not every author is like that. Jim Wallace's recipes are by and large incredibly well researched. If you ask him why he's done something, he'll tell you *exactly* why. I don't always agree with some of the recipes, but he clearly knows a lot more than me so I tend to think that I need to study more :-) Caldwell's recipes are the same. Quite a lot of the recipes here on the cheese forum are really well thought out and researched. Pretty much everything else I've found has been of variable (random?) quality.
