+110. Skim series.+--The kinds of cheeses eaten fresh have in common a very soft texture and the flavor of sour milk, principally lactic acid. The group falls naturally into two sections: (1) the cheeses made from milk curdled by souring; (2) those for which the milk is curdled by souring and rennet. In the latter group both agencies are necessary to the resulting product. The time required to curdle by souring alone is longer than when rennet is used; this period is usually longer than necessary for the cream to rise by gravity; hence the cream is either skimmed off or removed with the separator beforehand. The curd, therefore, is essentially a skimmed-milk curd. Casein curdled in this way tends to become granular or "rough," to feel "sandy" when rubbed between the fingers. Heating is commonly necessary to lower the water-content of the mass even to 75 per cent. Such curd tends to become hard or rubbery when heat is applied. In this group, the best known form is variously called "cottage" cheese, "clabber" cheese, schmierkäse. +111. Cottage cheese+ is made from skimmed-milk, soured by lactic bacteria until a curd is formed. This is done preferably at about 20° C. (70° F.), because at this temperature the purely lactic type of organism has been found to outgrow competing forms which may be present. Starter containing the desired culture, if properly used, saves much time in the curdling period. Such curdling requires at least twelve to twenty-four hours, frequently much longer unless abundant starter is introduced. +112. Household practice.+--The details of cottage cheese making in the home differ widely in separate sections and even in different families in the same part of the country. The essentials of the practice, common to all, include: (1) curdling the whole milk by natural souring; (2) removing the sour cream which is usually used for butter-making; (3) scalding the curdled skimmed-milk either by slowly heating it in the original vessel surrounded by hot water or by actually pouring an approximately equal volume of boiling water into the curdled mass; (4) bagging and draining the mass until it reaches the desired texture; (5) the kneading of the mass with the addition of salt and cream. The resulting product varies greatly in quality. Unfavorable fermentations frequently affect the flavor.[32] The "scalding" varies from a temperature of 90° F. almost to boiling with a resultant texture varying from almost the smooth buttery consistency of Neufchâtel to hard coarse granular lumps. The best practice, using clean well-cared-for milk and draining at low temperature, produces a very attractive cheese. Such cheese is heated to 90° to 100° F. on the maker's judgment, drained carefully, kneaded well by hand or by machine with the addition of cream to give it an attractive texture and flavor.