148. Acidity.—The essential biological factor in the making period of Camembert is proper souring. The milk should be free from gassy organisms. The lactic starter required should introduce the typical lactic organism (Streptococcus lacticus) in numbers sufficient to suppress all other forms during the next twenty-four hours. The amount of acid starter introduced, however, plus the acid resulting from growth during the curdling period, should not produce a grainy acid curd. The temperatures of handling are such as to favor this group of organisms if properly introduced and permit the development of nearly 1 per cent of acid (estimated as lactic) by the second morning. Cheeses with such acid are fairly free from further danger from bacterial activity. Members of the high-acid group (B. Bulgaricus and allies) may be found in these cheeses but do not appear to develop in numbers sufficient to affect the cheese to any marked degree.
Fig. 20.—Halloir, the first ripening room for Camembert in an American factory.
149. Ripening the cheese.—The cheese is now ready for the ripening rooms ([Fig. 20]). For this process temperatures between 52° and 58°F. are desirable; lower temperatures only delay the process; higher temperatures favor undesirable fermentations. The cheeses rest upon coarse matting (Fr. clayons) consisting of round wooden rods about the size of a pencil separated 1-1¼ inches and held in position by wire strands. Assuming cheeses of optimum composition as indicated above, the relative humidity of the ripening rooms should be 86 to 88 per cent. Higher humidities produce too rapid development of slimy coatings; too low humidity is indicated by drying, shrinkage and the growth of green molds on the surface. A slight and very slow evaporation is demanded; by this the water-content of the cheeses is reduced 3 to 6 per cent in two weeks. During the first two weeks of ripening, the cheeses commonly show some growth of yeast and Oidium lactis first, followed by cottony white areas of Camembert mold (Penicillium Camemberti). This mold must be introduced by inoculation in new factories but once firmly established in the factory will propagate itself if conditions are kept favorable. Climatic conditions in most dairy sections of America have been sufficiently unfavorable to make more or less continuous use of pure cultures desirable. At the end of two weeks, Camembert cheeses should show a well-established rind, consisting of a well-matted felt work of mold hyphæ through the outer 2 mm. (⅟12 inch) of the whole surface of the cheese. More or less of the pale gray-green fruit of the characteristic Penicillium Camemberti can usually be seen. Beginning at about twelve to fourteen days,[52] a softening of the curd is first directly detectable under the rind. This is preceded by the disappearance of the acidity of the curd, which progresses inward. The softening of the curd follows closely the lowering of the acidity. Thus a litmus test taken along the cut face of a Camembert cheese at any stage of softening will always show a sharp acid reaction in the solid sour portion which changes to alkaline just before the softening due to proteolytic action becomes noticeable. These two changes appear to be due to enzymes secreted by the mycelium of the Penicillium Camemberti and Oidium lactis which constitute the most active factors in the ripening. Some accessory bacterial action is indicated but of minor importance in the changes found.
To avoid loss from breaking, after the softening of the curd has fairly begun, the cheeses must be removed from the coarse matting to smooth boards where they are watched and turned repeatedly, or as in the more common practice, wrapped at once in parchment paper and boxed. The ripening may be completed in either way. The conditions necessary are such as to favor the extension of slimy areas of bacteria over part or all of the rind to the exclusion of further development of gray-green fruiting areas of mold.
Complete softening may occur in three weeks in cheeses in which evaporation has gone on too slowly. Such cheeses are found to contain 51 to 55 per cent of water when ripe and decay very quickly. If handled properly, the water-content should fall from about 57 per cent at the beginning of ripening to 48 per cent at its completion which should require a minimum period of about four weeks. It is more desirable that a cheese four weeks old show a thin core of sour curd in the center than that it be entirely liquid at that age.