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were radically altered; e. g., ripening temperature of the cheese milk 102° F. (instead of 80° to 84° F.), renneting temperature 90° F. (instead of 84° F.), maximum temperature of scald 102° F. (instead of 96° F.).
This modification considerably shortened the time required to make. a bulgaricus cheese, but it was still too long by a couple of hours. After running the whey, the acidity came on slowly, especially if the temperature was allowed to fall much below 100° °. To counteract this fall in temperature, the curd after the running of the whey was allowed to mat on the warm bottom of the vat, and water at 160° F. was added at intervals to the jacket of the vat. 'The curd thus kept warm becomes well matted on its lower surface, and is then turned over, and similarly matted on its other surface. When this stage is reached the curd is piled in blocks two deep on racks in the bottom of the vat and weighted. Hot water is run in below the racks and the vat covered over. In this way the temperature during cheddaring can be maintained at a little over 1000 F.; curd so treated develops acidity at the usual rate.
Cheese made after this method acquires a rich and characteristic flavor which is quite distinct from the ordinary Cheddar flavor; it is more attractive, especially toward the end of the ripening period. The texture, however, is firmer than the Dunlop type and still firmer than the standard Cheddar texture. The cheese at pressing seemed to have the desirable body, but during curing the texture became unexpectedly tight. The evidence of 50 cheeses made after this manner confirmed this finding. Attempts were made to secure a softer type of cheese by following the principles practiced in the making of English Cheddars, which are noted for their soft smoothi body. More moisture was retained in the curd consequent on ail earlier renneting; and a lower acidity, on running the whey. The curd was allowed to develop a full acidity before milling. High ripening and cheddaring temperatures were employed as before. The resultant cheese had a full and fine flavor, but the texture was decidedly faulty, being short and inclined to brittleness.
A combination of B. bulgaricus and Str. lacticus used as a combined starter gave good results when ordinary temperatures were used, but there was a tendency to overacidity whenever the proportion of Str. lacticus was high. Experiments showed that not more than one-eighth per cent of the latter should be employed along with B. bulgaricus. But with such a combination of starters, it is somewhat difficult to secure uniformity in the finished article, especially with reference to texture.
It ultimately became evident that the degree of acidification of the curd is the factor which exercises the greatest control over the texture of the cured cheese, and that if a normal Cheddar texture is to be got, B. bulgaricus cheese must be made with acidities much lower than normal. It was therefore decided to make cheese after the method of the English Derby, but to employ temperatures to suit the organism. (The Derby is a popular English cheese which commands a ready market; it is one of the softest of the handpressed cheeses, ripens quickly, has a soft buttery texture and a mild but distinctive flavor.) When this course was followed, and the degree and rate of acidification of the Derby attained, a type of cheese with Cheddar characteristics was produced which exhibited a first-class flavor and texture. The texture, hitherto the weakest feature of a B. bulgaricus cheese, was now no longer faulty. At the age of four to five months, it was equal in texture to the best Cheddar, and the meatiness previously sought for was at length obtained. The flavor was full and distinctive, and without exception was appreciated by all cheese judges.
As the management of this type of cheese differs in some essentials from the Cheddar and the Derby cheeses, and is adapted to all starters of a similar type, a few observations on the process of manufacture will be given.
SPECIAL PROCESS OF MANUFACTURE.
In order to control the fermentation in the cheese milk overnight, a small quantity, usually a few drops, of starter is added to the evening's milk, which is stirred and cooled to 70° F. In the morning, an acidimeter reading is taken; starter at the rate of 1 per cent is added, and the morning milk is run in. The temperature of the mixed milk is adjusted to 100° to 104° F., kept at this for three-fourths hour, and then cooled back to 86° F., the temperature at which the rennet is added. If the cheese milk were renneted at 100° F., the resultant cheese would be too firm in texture, as our experiments have amply demonstrated.
Coagulation with normal rennet extract, added at the rate of 1 ounce to 20 gallons, is complete in 40 minutes. The curd is cut as for Cheddar, and an acidimeter reading of the whey taken immediately after cutting. This reading, which is usually about 0.13 per cent, gives an important clue to the development of acidity and the rate at which the subsequent scald should be conducted. After the curd has been hand stirred for 10 minutes, the temperature is raised 1° in every 3 minutes to a maximum of 96° to 100° F. (according to season and class of milk). The curd is pitched when sufficiently firm at an acidity of 0.15 to 0.16 per cent. In 30 to 40 minutes, the whey is run at an acidity of 0.18 to 0.20 per cent. It is important that the acidity should develop gradually, and that the whey should not be more acid than 0.20 per cent when it is run. (British Cheddars are usually dipped at 0.23 per cent.)
On the removal of the whey, a channel is cut down the center of the quickly matting curd, which after 20 minutes is cut up into 10-inch blocks. These blocks are piled two deep on the top of racks placed in the vat and weighted. The blocks are turned and piled until the curd is well cheddared and the requisite degree of acidity has been developed. If the temperature of the curd falls too low, so that acid formation is arrested or proceeds unduly slowly, the curd may be warmed by first placing it on the bottom of the vat, to the jacket of which hot water has been added, and subsequently on racks below which hot water has been introduced. We have usually found this procedure more necessary in the early and again in the later part of the cheese-making season.
After the third turning, the curd is cut into strips and placed on the cooler to reduce the temperature to that of milling. If this is not done, the curd at milling will be too soft, which factor, coupled with the high temperature of the curd, will result in a large loss of fat in the form of a white whey at milling and from the press. The curd should be milled when hot-iron threads three-fourths to one inch are got, and when the acidity is from 0.4 to 0.45 per cent. Salt is added to the cooled curd at a temperature of 76° F. and at the rate of 1 ounce to 3 pounds. The acidity of the press whey should be from 0.5 to 0.6 per cent. An acidity of over 0.65 per cent is generally too high if a soft meaty texture is desired.
Recently we have obtained excellent results by adding all the starter to the evening's milk. The quantity of starter required in the case of Str. lacticus when this procedure is adopted is 1 ounce to 40 gallons of milk, but much larger quantities are required when organisms of the B. bulgaricus type are used-up to 1 per cent of the volume of the evening's milk. When all the starter is added in the evening, the acidity of the evening's milk in the morning should not be higher than 0.25 per cent if the normal period of three-fourths hour at the maximum ripening temperature of 100° F. is to be allowed. If an acidity in the vicinity of 0.3 per cent in the evening's milk is recorded, the temperature of the milk after the addition of the morning's milk should be adjusted to 84° F., a short ripening period of half an hour allowed, and the routine described followed.
After several years of careful experimentation we are satisfied that the foregoing process of manufacture, if carefully followed, will produce with B. bulgaricus a cheese of excellent texture and an unusually fine flavor, which in an unrestricted market will com mand a higher price than ordinary Cheddar. The temperatures and acidities should be strictly adhered to, and the starter carefully prepared. The cheese is always true to type, and its manufacture can be confidently recommended to the skilled cheese maker. Its production in factories from milk pasteurized to 140° F. by the holding method is specially indicated. The important points in the making of this type of cheese are the use of pure high-grade milk, a regulated development of acidity during the making process. and a comparatively low acidity from the press. It should take the same time to develop 0.5 per cent acidity with B. bulgaricus cheese as it takes to develop 0.9 per cent acidity with ordinary Cheddar.
As regards the curing of these cheeses, certain distinctive features have to be recorded. The rate of ripening is somewhat slower than normal and the progressive changes in texture more marked At the end of four weeks, the flavor has only faintly developed: the curd is still harsh and raw, and the texture consequently dis appointing. At two months the characteristic flavor begins to appear and the texture to improve. At four months the fine distinctive flavor is appreciated. The texture is now soft and silky and mellow to the palate. The temperature of curing should lie between 50° and 60° F.
The same procedure was followed with other organisms of this group with uniformly successful results. Two of the most useful representatives are B. freudenreich and Streptothrix dadhi. B. freudenreich, whilst not so vigorous as B. bulgaricus Massol, is sa fer to use with milks which are easy to ferment. It produces cheese with a mild but very pleasing flavor and a silky texture. which remains soft, even with advanced curing. A ripe cheese when cut across usually exhibits small irregular or ragged holes.
Streptothrix dadhi (the designation streptothrix is not morphologically correct) was found on the whole to be the most satisfactory of all the organisms experimented with. A pure culture of this bacterium, which is native to the sour milk of central India, was obtained from Doctor Chatterjee, of Calcutta University, by whom it was first described in 1910. As a starter, it proved to be reliable, was relatively easy to maintain in pure culture, and remained vigorous for a considerable time. It gives cheese of a soft meaty texture and of an excellent flavor. It seldom produces cheese with a firm or tight texture.
Three organisms, Bastonicini lactici coagulanti Gorini and streptobacterium 11 and 32 (Jensen), did not prove quite so vigorous as the aforementioned organisms; nevertheless, cheeses made with their aid were very attractive to the consumer, and earned very favorable commendation. The bacillus of Tarkhana appears to be closely related to B. bulgaricus of Massol, and produces cheese with similar characteristics.
As regards the quantity of starter to be employed in the case of individual organisms of this group, and also with reference to the acidity to be developed during the making process, some guidance may be got from the rate of acid production in the starter itself. When a starter develops 2 per cent acid or over in 12 to 16 hours, a low acidity from the press should be aimed at, 0.5 to 0.55 per cent being sufficiently high. Organisms producing 1.5 per cent acid in the same time may be allowed a higher maximum acidity from the press, and up to 0.65 or 0.7 per cent should be developed. The higher the rate of acid formation in the starter, the less need be added to the cheese milk.
CONTENU MICROBIQUE DANS LE FROMAGE GRANA PENDANT
GIULIO DALLA TORRE, Ph. D., de L'Institut Expérimental de Laiterie de Lodi,
C'est l'usage que dans la fabrication du fromage italien grana, et particulièrement dans l'espèce qui s'appelle “Reggiano, dans le lait différentes quantités de microbes, moyennant des ferments sélectionés, ou bien encore, comme on fait aujourd'hui, sous forme de ferments naturels en se servant dans ce cas du petit-lait fermenté.
Le petit-lait examiné immédiatement après la fabrication du fromage présente des quantités de germes très variables qui sont en relation directe avec le contenu microbique du lait et avec celui du ferment ajouté.
Pour rendre le petit-lait frais adapté à l'inoculation il est nécessaire de l'enrichir de microbes, soit moyennant l'addition de ferments sélectionnés, soit en le soumettant à la fermentation, c'est-à-dire en le rendant dans les conditions les plus favorables qui permettent un développement majeur des microbes utiles au désavantage des germes
Les températures plutôt élevées au premier temps de la fermentation, sont particulièrement celles qui donnent dans le petit-lait le développement des bactéries lactiques, lesquels cependant même, plus en avant, continuent sans en être dérangés à se multiplier jusqu'à fermentation achevée.
Ces conditions favorables servent aussi, malgré en mesure beaucoup plus limitée, pour les streptococcus qui, au moment de l'examen du petit-lait dans l'inoculation du lait, se trouvent toujours en grand nombre.
Les températures élevées qui aident le développement des bâtonnets lactiques exercent par réflexion--si elles sont conservées pendant longtemps-une influence remarquable, même sur la qualité du fromage.
D'après de nombreuses expériences faites, portant le petit-lait moyennant un chauffage avec un poële exprès à 42-45° C. pendant 20 à 22 heures, j'ai toujours obtenu des fromages qui, dans leur propriété, s'éloignaient assez de la grana et se rapprochaient, au contraire, soit par les trous, soit par la saveur à l'Emmental.
Le fromage sitôt fait présente une flore bactérique identique à celle de son petit-lait.
D'après de nombreuses analyses faites sur du fromage frais, j'ai toujours pu constater les streptococcus lactiques en grand nombre, même pendant la saison froide, où d'habitude, en comparaison avec l'été, le quantitatif microbique paraît assez réduit.
Les lacto-bacilles se trouvèrent chaque fois signalés (cependant presque toujours en nombre inférieur à celui des coccus), soit ceux avec propriété de coagulation facile du lait, type B. casei alfa et epsilon de Freudenreich, soit ceux avec lente ou sans coagulation et avec propriété gazogène; et leur présence se rencontre continuellement en grande quantité pendant l'été, tandis qu'en hiver on n'en trouve d'ordinaire un petit nombre.
Dans cette dernière saison on a pu souvent remarquer les bâtonnets lactiques producteurs de gaz en majeure quantité de ceux avec facile coagulation de lait.
Entre autres microbes importants, outre les bactéries cités, nous trouvons les bactéries acido-présamigènes, saccaromycètes, et torules souvent présents en quantité considérable.
Le quantitatif des germes, déjà très élevé dans le fromage de préparation récente, augmente encore remarquablement pendant la maturation, particulièrement pendant les premiers temps, jusqu'à ce que la température dans la masse caséeuse reste élevée, rejoignant parfois des chiffres très élevés de microbes pour un gramme de fromage.
Arrivés au point maximum de l'augmentation le numéro des microbes commence à diminuer.
En suivant le procédé des bactéries lactiques, qui, à fermentation avancée du fromage sont toujours les majeurement représentés, nous observons que la diminution se prolonge pour longtemps, se faisant rémarquer spécialement dans les coccus, lesquels généralement disparaissent avant les formes bacillaires, malgré qu'en certains cas on peut apercevoir en quantité remarquable ensemble aux bâtonnets jusqu'à une époque très avancée de la maturation.
En ce qui concerne les ferments nuisibles aux fromages, il faut rappeler en premier lieu les bactéries du groupe coli-aérogènes presque toujours contenu dans le lait, mais leur action dans le from