+87. Acidity and expulsion of the whey.+--The contraction of the curd and expulsion of the whey are so closely related that they may be treated under the same heading. The more acid, the faster the whey separates from the curd, other conditions being uniform. The relation of acidity and firmness of the curd to temperature of the curd is another important factor in the successful manufacture of cheese. The higher the acidity, the faster the temperature of the curd can be raised without any harmful effects. If the temperature is raised too fast in relation to the acidity, the film surrounding each piece of curd will become toughened so that the moisture will not be able to escape. When this condition exists, the curd will feel firm but when the pieces are broken open the inside is found to be very soft. This results in a large loss later or may cause a sour cheese. It usually causes an uneven texture and color in the cheese. +88. Acidity in relation to cheese flavor.+--Just what part the acid plays in the development of cheese flavor is not known. If a certain amount of acid is not present, the characteristic cheese flavor does not develop. If too much acid is developed, it gives the cheese a sour flavor which is unpleasant. If sufficient acid is not developed, the other undesirable factors seem to be more active, causing very disagreeable flavor and may cause the cheese to putrefy. A cheese with a low acid usually develops a very mild flavor, and if carried to extremes, as in the case of some washed curd cheese, the true cheese flavor never develops. +89. Acidity in relation to body and texture of cheese.+--If a cheese is to have a close, smooth, mellow, silky body and texture, a certain amount of acid development is necessary. If too much acid is developed, the body and texture will be dry, harsh, sandy, mealy, corky. If the acid is not sufficient the cheese may be soft or weak bodied, and is usually characterized by "Swiss curd holes," which are spaces of various sizes usually more or less round and very shiny on the inside. +90. Acidity in relation to cheese color.+--An over-development of acidity affects the color of a cheese. If this development of acidity is uniform throughout the cheese, it causes the color to become pale or bleached. If this development is uneven, due to the uneven distribution of moisture, the color will be bleached in spots, causing a mottled effect. +91. Control of moisture.+[28]--The cheese-maker must use skill and judgment in regulating the amount of moisture in relation to the firmness of the curd and the acid. Since there are no quick accurate tests to determine the amount of moisture, this is left entirely to the judgment of the operator. Certain methods of handling the curd reduce the moisture-content, while others increase it. The cheese-maker must decide how to handle the curd. If the curd becomes too dry, methods should be employed to increase the moisture, and vice versa.