A study of the Relationships Between Hydrogen Ion Concentration Titratrable Acidity, and Quality in Cheddar Cheese

Abstract

The manufacture of sour or acid cheese causes serious losses each year to the American cheese industry. The excessive acidity may affect any or all of the properties of the cheese, such as flavor, body, texture, color and finish. The defect may be almost negligible or it may be highly injurious to the market value of the product. Excessive acidity may be avoided by skillful operators through careful observation of the milk and curd from day to day. Tests which indicate, but do not measure acidity accurately, are the so-called renne t and hot-iron test . These methods of detecting acidity attain their greatest value when used every day by the same operator on the same milk supply. The alkali titration test is commonly used to measure acidity during the cheese-making process. Optimum degrees of titratable acidity in the starter, milk or whey have been indicated for nearly every operation. But defective cheese is sometimes made even though these schedules of optimum titratable acidities have been carefully observed. It is well known that the titratable acidity of fresh, normal milk may vary through wide limits (1) due to the influence of a number of factors (2, 3, 4). The differences in titratable acidity which may be caused by the variations in the composition of milk should be particularly significant in the manufacture of cheese. ~Ieasurements of titratable acidity during the making process actually indicate, that the maximum acidities, which may be safely attained in the manufacture of cheese from milk with high solids content, may be disastrous if applied to milk which is low in solids-not-fat. The hydrogen ion concentration furnishes an indication of changes in milk which can not be definitely measured by titratable acidity. For example, the maximum hydrogen ion concentration attained during the fermentation of milk by a given organism is quite constant; then, also, the changes in the casein of milk, which are caused by increasing acidity, culminate in coagulation at the iso-electric point of pH 4.7. It seems possible that measurements of hydrogen ion concentration might furnish a better means of detecting critical changes during the making of cheese than do measurements of titrat~ble acidity.