ACID.
Acid microbes are inherent in the lacteal structure and come dormant in the milk from the udder. As soon as they feel the atmosphere they spring into spontaneous activity, however retarded by cold or fostered by heat. Acid in milk is a species of yeast fermentation and is the first step toward decomposition. It is the best servant the cheese maker has and is also his worst enemy when the relation is changed to that of master. In a temperate climate, in hay produced milk, in the spring of the year, acid is nearly dormant and there is but little use for it. Hay cheese are expected to be thrown on the market in cool weather when they will be quickly consumed; therefore, the additional firmness given by acid is not required to be applied as a safeguard against heat. If early hay cheese are cooked enough and salted about two pounds to the thousand, it is all that is desirable. On the border between hay and grass the weather is gradually moderating and there is torrid temperature in sight in the immediate future. Acid now begins to appear in the whey and curd you are working by the time you have it scalded. It has a right to be there for it is your friend and you now need its timely proffered assistance. If, through unusually good quality of milk, it does not come to the front, coax it a little in the following way: After the curd is cooked and before whey is drawn, turn on steam and re-warm the whole mass, then draw the whey and pack the curd in bulk as much as possible, covering it up with a cloth. This will soon set the acid to working in good shape. Always rely on the hot iron test to locate acid. It takes an expert to get the amount of acid even from mess to mess by an olfactory measurement. On March and the first half of April stock I do not care for any acid to show, but on later April and beginning of May goods acid should show on the hot iron clearly and perceptibly. When the curd is pressed to the metal, fine strings should just start from it immediately prior to salting. At this time you want just a little acid but not too much—too much will surely spoil spring made cheese.
The question arises, “How far must a cheese maker probe into the hidden mysteries that shroud the digestive assimilation of the product he manufactures?” We answer that he cannot probe too deeply or extend his researches too far into the minute. There are too many makers now with only a superficial knowledge of their craft, and before there can be any perceptible elevation of quality in American cheese the shoes of these novices must be filled by such men as we now term “experts.” Take, for example, the subject of acid which we are here discussing. A maker who can perceive it only as it is revealed by stringing on the iron is not competent to be in charge of a factory, for anybody could detect it there. The development of lactic acid is a species of fermentation induced by the spontaneous increase of inherent minute bacteria. It takes the same experience to perceive and govern it in milk and cheese as it does practice with square and compass to become a carpenter. We cannot tell you all about it—it will take many days of careful observation and fine testing to understand its nature enough to make it your servant in the cheese making art. That is why makers without practical experience are always incompetent. Hold curd in the whey until it shows at least a quarter of an inch of acid by the hot iron and then draw off whey as quickly as possible. It is always a good plan where you have large vats and they are pretty well filled to have a third of the whey drawn off before acid develops, for then you can more quickly lay bare your curd. As the whey recedes, push the curd with the rake head toward the upper end of the vat and then tip the vat down, so that the whey will flow out from the lowest corner. Make a gutter with your hands through the center of the curd mass and distribute it in an even pack on each side of the vat. Now, take a knife and cut it into strips eight inches wide, drawing the knife from the center gutter toward the side of the vat. Flop these strips upside down and, to farther facilitate drainage, cut a longitudinal canal next to the sides of the vat. Examine by the iron and see how the curd is working as to acid; if it is maturing slowly and the curd is not hot, shut off all draughts of air, cut the curd into “bricks” or blocks the size of a brick, and scatter them over the bottom of the vat. Then cover the vat up with the same cloth that you used when scalding. If, on the other hand, the curd is hot and maturing rapidly, cut into small bricks, scatter well and give it all the air possible, frequently turning the bricks over. Unless positively unavoidable on account of overplus of acid never grind curd until you have cooled it down to a temperature of 80°. Above that heat the fine texture of the curd is torn and mutilated so that it will give out white whey, and, as a consequence, waste of quality and substance ensues.
The curd being first well drained and cooled to 80° by subdivision of pieces and having also developed acid sufficient for the season, it is ready for the mill. Grind with deliberation, and if you have a self-salter, so much the better. Incorporate the salt into the curd by thorough, although not violent, mixing and then air your curd. This is one of the most important processes of all and yet the one most neglected by negligent makers. A curd requires airing, not so much to expel heat as to expunge the gaseous odors that have followed it down from its animal origin. Stir it well at frequent intervals and spread it out well over the surface of the vat. So calculate that it can lay twenty minutes or half an hour before it has sunk to the temperature of 70°, when it is just right for the hoops. Allowing it to lay this length of time gives the salt an opportunity to strike into the pores and impregnate the product with its saline properties before being put under pressure.