PASTEURISATION.

Manawatu Standard, Volume XL, Issue 7066, 27 July 1901, Page 4

PASTEURISATION.

(By J. A, Kinsblla, Dairy Com

missioner.)

After a brief introduction as to the necessity of improving the. quality of soma of the brands of butter, the writer proceeds :

If we wish to improve our methods we must move with the times, and take advantage of the latest scientific advance in this industry. Now, from what is known to the practical arid well-posted butter-maker of to day on the subject of cream-ripening, it would be idle for me to discuss the question with those who have had no experience in the preparation of cultures and starters, and who have no knowledge of the benefits derived from the use of a selected culture in the ripening of cream, whether it be pure artificial imported culture or a properly prepared domestio starter. Why we choose a starter is that if the cream is in anything like good condition, and the starter possesses favourable ripening qualities, it is certain to produce a similar fermentation in the cream.

I now come to tbe important point, and the one wuich faces every manufac* turer of butter ia the colony to-day. That-is, if the culture is added totheraw cream, which contains millions of dangerous bacteria, eminently adapted for the production of bad flavours, it is doubtful whether the culture organism, will gain the supremacy over such millions of dangerous bacteria duciog tho ripening process. It can hardly be expected that the most beneficial results will be attained in this way, seeing that only such a proportionately small quantity of starter is' added, to the cream. Where the cream is in bad condition, and the starter has not proved beneficial in improving the flaveur. we must resort te some other means of overcoming the difficulty. How are we to do this ? Tbe cream must, in the first place, receive more attention from the time the milk is drawn from the cow, aud the cream must also receive some special treatment at the factory, whereby a better seed-bed will be formed, so as to give the selected organisms in the starter a chance to overcome any undesirable organisms in the cream. From the knowledge we possess at the present time, this preparation or treatment of the cream can be accomplished by pasteurisation. Pasteurisation destroys mostly all the.vegetable bacteria, leaving only the latent spore forms of life in the cream. The then addition of a properly prepared starter into ' the . pasteurised cream, instead of into the raw cream, gives the selected, organisms contained in such starter a grand chance to overcome any other organism present in the cream. Even when cream is pasteurised, ii selfripened—that is, when no Btarter is added—the spore-bearing forms of life very often produce the most undesii-eble flavours in butter; hence the importance of a pure starter.

At a few. factories where the starter process of ripening was fairly carefully carried out during the past season, and where the butter made was found to be an excellent article when leaving the colony, it "was afterwards found that some of this same butter had deteriorated very much when placed on the counter in London, even with the low temperature it was held at in transit. Now, after careful observation in connection with two or three "such cases. I am more than ever convinced that we must'resort to pasteurisatiou at such factories, and I am prepared to assist aDy factory-manager who has had trouble with. quality last season arid who wishes to take up this question at the beginning of next season. I may hero point out a few of the advantages gained by the use of a fermentation starter in cream for butter making. One of the greatest advantages is that the butter maker' who is not able tn make good butter iB, by the application of a starter, able to get rid of some of the hidden trouble present in tbe cream in the form of bacteria. The butter maker is also able to make a: much tnore uniform quality from day to day by the use of a good culture starter. Without the use of a starter the very best butter makers are not able to control the ripening process so as to make a standard product. Then, again, comes the most important point: butter made from pasteurised cream to which a pure starter has been added will keep much longer than tbe ordinary product. The object in using a starter is not, as many people think, for the purpose of imparting a much higher flavor to the butter than can be obtained in the ordinary way, if the cream be pure, but more to overcome or destroy the > ban flavor producing organisms which exist m the cream in the ordinary factory.. In . ripening cream wo-aiin at three things : acid, flavor and ' aroma. - The ripening process certainly has influence over the character of the fermenta,tion that takes place. . The aroma of butter is very confused with flavor. Flavor is a quality _ which we judge by taste; The production of flavour in ripened cream butter is brought about by or due to certain feed eaten by the cows, and also to the action of the bacteria during the' fermentation changes. Flavours, on the palate,-or to the taste, may often bo described as bitter, lardy, oily, or weedy, while the ar6ma ; appeals to the. sense of smell';rather than to the taste. '■"■'• The source from which this delicate quality in but'er comes has not 1 been definitely: discovered,: 'but so far as .investigation goes,;:::it :is .dependent largely.'/on the presence of volatile decomposition. Coming 'back to the niairi subject, I may point out that T would not recommend pasteurisation in a factory where the cream is in first-clasß condition, and where the product turned out is giving entire satisfaction to the consumer. Pasteurisation, if properly carried out at factories, will drive off a great many taints that are absorbed direotly from

tho cow or from exposure to foul odours. While it is tiup, as above stated, that pasteurisation "'will not improve the flavour of first-class milk or cream, also that taints imparted by 'turnips, onionH, rape, garlic, and other such feed, if very strong in milk or cream, cannot wholly bo removed, it is possible by pasteurisation to eliminate part of such taints, so that a better article of butter cau bo made. Although when milk is heated to 140deg. and held for ten minutes most of the lactic-acid group aro kiiled, it is necessary in pasteurising for buttermaking to heat to a temperature of 158 deg. to I6sdeg., particularly with the ordinary type of • continuous-flow pasteurising, macbinos now on the market. Milk may bo heated to 140deg., and maintained there for thirty minutes; this will kill all tubercule germs, and it does not change or destroy ihe viscosty of the mi k. Inselectinga machine for factory work it is always a wise precaution not to select too large a machine, or to have on hand a small machine for use when small quantities of cream or milk aro to be pasteurised. In running large machines at a slow speed with small quantities of cream or milk we very often find the butter globules impaired by concussion against the sides. We .also find serious losses of fat by using large pasteurisers for heating purposes only. Thero are, in fact, a great many things to be remembered by the buttermaker when he undertakes pasteurisation in a factory. At temperatures above l.bdeg. bacteria do not grow well. Very few thrive above 125 deg., and the higher the temperature is raised the more bacteria perish. Heating milk to boilling-point or thereabouts always imparts a .boiled flavour ; but it is possible to reduce this so as to be almost imperceptible by heating to only 158 deg. Experiments have proved that if milk or cream is kept at 158 deg. for ten.minutes most of the bacteria will be killed. Cream may be heated to 160 deg., if quiokly cooled afterwards, without developing a boiled flavour. .-••...■.'

Some species of bacteria are not de~ stroyed even by heating the milk to 212 deg. or 215deg. That being so, it seems useless to attempt to overcome the prejudice against the so-called boiled or cooked flavour, when a,' sure safeguard against the most common daDgers can be secured by heating to between 158 deg. and 165. In other words, the worst flavour-produoing germs are de* stroyed at the latter temperatures. It has been proved that raising the temperature of the bream rapidly to 158deg. and keeping it at this point for two to five minutes, then immediately chilling tto 65deg-, or below, will destroy nearly all forms of bacterial life. But although heating to I.Bdeg., or even boilingpoint, kills most of.the bacteria, it does not desttoy their spores; hence, if the milk or cream is held at a favorable temperature—between 80deg. and 100 deg.- for any length oftime, tbesespores will develop and the battle begin anew. The cooling should be done rapidly, especially between 120deg. and 65deg. __.. From.a butter-making standpoint the cream only need be pasteurised. In the spring and summer, however, when the milk is fed to calves, it pays to heat tho skim milk"to 160deg. This process increases its keeping qualities, and makes it a much better food for calves. The whole milk may also be pasteurised. Reports Bhow that in Denmark it is compulsory to pasteurise all the milk, in orderto prevent tuberculosis from spread ing through the medium of the skim milk ; also, foot arid mouth disease. I would, however, recommend pasteurising the cream only, and if it is found necessary to pasteurise the skim milk this may be done more economically by using the exhaust steam from the engine. By means of an insulated skim milk tank covered over, and passing the exhaust steam direct into the skim milk, it may be scalded with little or no cost to the average factory, where the exhaust steam is at present allowed to go up in the air.

Alt-hough pasteurisation is far beyond the experimental stage, there is yet a diversity of opinion as to wether pasteurised cream gives a better butter than non-pasteurised. It is a fact that pasteurisation has a tendency to destroy the fine aroma of tbe raw butter, but while there is one factor against it there are many in its favour—viz. : - (1) Pasteurisation gives a mild, uniform flavour do the butter ; (2) it gives an increased keeping-quality to tbe butter ; (3) it destroys the injurious bacteria in milk or cream ; (4) it improves the fl ivour of milk tainted by strong* flavoured food; and (5J it reduces the germ-content of the milk, which means that it leaves a cleaner seedxbed for the lactic-acid germ, which is introduced into the cream through the medium of a pure-flavoured fermentation starter- an iddispensable factor iv the manufacturt of a uniform article of butter. -.

On the whole, seeing there is a difficulty in obtaining a good - quality of clean-flavoured milk, even at our best factories, pasteurisation is sure to be beneficial in bringing about uniformity in our butter.

The subject may be summed up in the following points :— 1. Pasteurising means heating the milk or cream to between 155 deg. and 160 deg., and keeping it that point from fifteen to thirty minutes,, then cooling quickly down to 05 deg , or a suitable ripening temperature. 2. Heating alone is not pasteurising, but the term is also used when milk or cream is heated and immediately cooled, which is sufficient to destroy a large number of the bad flavour producing germs in cream which is to be ripened. ... 3. The effectiveness of pasteurisation is in proportion to tho; height of ternv peratufe, and- tbe length of time the milk or cieain is exposed thereto. .4. Tho sooner the milk is pasteurised after being drawn from the cow the the greater value of the process, for the fewer germs will there be to kill.

5. The best results are obtained by the, quickest heating with the least scorching of tbe milk or cream, which means that it must be kept, in constant motion.

6. If you are not prepared to properly equip your factory and get sufficient assistance to carry out the work systematically arid well, do not pasteurise. 7' If. you are not . prepared to thoroughly clean your coolers, heaters, and everything connected with the cream, do not pasteurise. v 8. If cans, pails, vats, pasteurising machines, and all utensils are not thoroughly washed and sterilised, pasteurising is of but little avail.

9. Always remember that pasteurisa* tionis not a cure-all for every kind of tainted and dirty milk. 10. If you do not intend to ripen your cream, and you are not familiar with the method of preparing a good fermen-tation-starter do not pasteurise.