Part 13 (1/2)

CHAPTER VII

BACTERIA AND buttER-MAKING

Inbutter from the butter fat in lobules into crea process The crearavity process or separated froal action In either case the bacteria that are nor numbers in the creareatthat the bacteria are caught and held in the hter specific gravity, move toward the surface of the milk or toward the interior of the separator bowl This filtering action of the fat globules is si As the suspended particles fall to the bottoanison the kind as well as the number of the bacteria that are to be found in the creaely deter tee of the ravity methods_ In the old shallow-pan process, the teh, as the h temperature favors especially the develop-point is near the air temperature By this er time than with any other, and consequently the contareater Usually creaer nuher acid content

_2 Modern gravity ravity methods where cold water or ice is used to lower the tee variety of species The nuely upon theIf care is used in , and the milk is kept so as to exclude outside contamination, the cream will be freer fro the milk Only those forrow at the low temperature at which the milk is set Cream raised by this method is less frequently infected with undesirable forher teal erm-life than that which is secured in the old way It should contain only those for and subsequent to the , for the cream is ordinarily separated so soon that there is but little opportunity of infection, if care is taken in the handling

As a consequence, the number of species found therein is smaller

Where milk is separated, it is always prudent to cool the creaenerally heated before separating in order to skih cream is nues due to bacterial action are slower; hence milk sours more rapidly than cream For this same reason, cream will sour sooner when it remains on the milk than it will if it is separated as soon as possible

This fact indicates the necessity of early crea quality of the product, and is another argu of cream~ If creaoes a series of ferly complex in character, the result of which is to produce in butter made from the same the characteristic flavor and aroma that are so well known in this article We are so accustomed to the developenerally recognized as being intimately associated with bacterial activity unless compared with butter made from perfectly fresh cream Sweet-cream butter lacks the aromatic principle that is prominent in the ripened product, and while the flavor is delicate, it is relatively unpronounced

In the pri, where the butter wasof creaht be accue occurred spontaneously without the exercise of any especial control With the develop a control of this process, and therefore the modern butter-maker must understand the principles which are involved in this series of coive to his product its coes three different factors are to be taken into consideration: the development of acid, flavor and aroma Much confusion in the past has arisen from a failure to discriminate between these qualities While all three are produced si, it does not necessarily follow that they are produced by the sao too far, undesirable rather than beneficial decoreatly impair the value of butter, so that it becomes necessary to know just to what extent this process should be carried

In crearowth, the extent of which is determined mainly by the temperature of the creaaniserm content of the ripened product is more uniform When creaanisher nuerm content that has no parallel in any natural er proportion of bacteria in crea class, but in the process of ripening, these forms seem to thrive still better, so that when it is ready for churning the germ content of the cream is practically ~ In fresh crealobules which are suspended in the milk serum are surrounded by a fil readily During the ripening changes, this enveloping substance is lobules cohere when agitated, as in churning The result is that ripened creaer nuranules, the yield is slightly larger--a point of considerable econoe quantities of butter are made

~Development of acid~ The result of this enormous bacterialthe principal acid so foranic acids are undoubtedly formed as well as certain aromatic products While the production of acid as a result of fermentative activity is usually accompanied with a development of flavor, the flavor is not directly produced by the formation of acid If cream is treated in proper proportions with a commercial acid, as hydrochloric,[154] it assu properties as found in normally ripened cream, but is devoid of the desired aromatic qualities Lactic acid[155] has also been used in a similar way but with no better results

The amount of acidity that should be developed under natural conditions so as to secure the optimum quality as to flavor and aro Concerning this there have been two soent views as to what is best in practice, so that better results were obtained with crearee of acidity than where a less amount was developed[156] The present tendency seems to be to develop soht that this secures h, quick” flavor wanted in the e, creaher percentage than this giving a strong-flavored butter In the determination of acidity, the ton alkaline tablet, which permits of an accurate and rapid esti creaoverned by the amount of butter-fat present, for the formation of acid is confined to the serum of the cream; consequently, a rich cream would show less acid by titration than a thinner cream, and still contain really as much acid as the other The iathered-crea is dependent upon the conditions that affect the rate of growth of bacterial life, such as tianisms in cream and also the per cent of butter fat in the creao it was customary to ripen cream at about 50 to 60 F, but more recently better results have been obtained, it is clai te lessened As high a temperature as 70 to 75 F has been recommended

It should be said that this variation in practice may have a valid scientific foundation, for the te crea what kind of bacteria will develop most luxuriantly It is well known that those for bitter flavors are able to thrive better at a lower te species

The importance of this factor would be lessened where a pure culture was used in pasteurized creaanism alone controls the field

It is frequently asserted that better results are obtained by stirring the crea it to the air as ricultural College, however, show practically no difference in the quality of the butter reatto the facultative class, and are able to grow under conditions where they are not in direct contact with the air

~Flavor and aroma~ The basis for the peculiar flavor or taste which ripened creae part, to the formation of certain decomposition products formed by various bacteria Aroma is a quality often confounded with flavor, but this is produced by volatile products only, which appeal to the sense of sood flavor is accoin of the two qualities is not necessarily dependent on the saanisms The quality of flavor and aroma in butter is, of course, also affected by other conditions, as, for instance, the presence or absence of salt, as well as the inherent qualities of the milk, that are controlled, to some extent at least, by the character of the feed which is consumed by the animal The exact source of these desirable but evanescent qualities in butter is not yet satisfactorily deter to Storch,[157] flavors are produced by the decoar and the absorption of the volatile flavors by the butter fat Conn[158] holds that the nitrogenous elements in cream serve as food for bacteria, and in the decomposition of which the desired aroe is unquestionably a cole fererspecies can take part in the production of proper flavors as well as desirable aromas The researches of Conn,[159] who has studied this question most exhaustively, indicate that both of these types of decomposition participate in the production of flavor and aroma He has shown that both flavor and aroood flavor-producing for to that class which renders e the reaction at all Soelatin and would therefore belong to the casein-dissolving class Those species that produced bad flavors are also included in both feranisms that are favorable flavor-producers; in fact they werespecies None of the favorable aroations were lactic-acid species,--a viehich is also shared by Weigmann[160]

McDonnell[161] has found that the production of aroma in certain cases varies at different te evolved near the optih for crea cream do not seem to exert any marked influence in butter A considerable number of species are positively beneficial, inasood flavor or aroma