DAIRY BACTERIOLOGY.

Hawera Star, Volume XLVI, 25 May 1926, Page 4

DAIRY BACTERIOLOGY.

SCIENTIFIC FOUNDATIONS OF INDUSTRY. LECTURE BY MR. P. O. YEALE. A lecture to the managers, branch managers, and assistants of the dairy factories incorporated in the Federation of Taranaki Co-operative DairyFactories was delivered yesterday afternoon in the offices of the Egmont A. and P. Association bv Mr. P. O. Veale, the head of the Dairy Federation’s laboratory in Hawera. This is the first of a series of six lectures to be given for the benefit of the factories that support the laboratory. In the> absence of the president of the Federation, Mr. T. A. Winks, who was in Wellington, Mr. ,J. R-. Corrigan, a member of the executive, occupied the chair. The attendance numbered some 3p dairymen

Iu his opening remarks the chairman said that science had not ad-vaV-ied with _ the practical sidje of dairying in this country. A great deai was owing to factory managers for the produce they had been able to manufacture without scientific help. The object of these lectures by iMr. Veale was to provide the factory men with the scientific assistance they' had lacked in the past. The chairman then read a message from Mr, Winks, expressing the latter’s regret .at being absent, and referring to the meeting and lecture as the second great step in the progress of the dairying industry. The community owed a debt to those present for bringing the district's produce so prominently; before the people of the world. While realising the managers’ value in the past, the executive felt that the stage was being approached when science should be brought to bear on the manufacture of dairy produce. With closer settlement, and the yearly increase in the. number of imported cattle, diseases were bound to increase beyond the power of the ordinary prac. tical manager, highly qualified though he be. The writer said he had yet to be persuaded that many of our troubles did not arise from the fertilisers which the farmer was now bound to use. The use of manures had altered the character of the milk as compared with the product when the virgin soil was at the dairyman’s command. Realising the difficulties, the federation had decided to assist by initiating a series of lectures by its scientist, Mr. Veale, in whom the executive had confidence. It was hoped that these classes would form the nucleus of a. dairy school, where the budding manager would take a thoroughly scientific course before actually taking up the practical side of manufacture, thus avoiding many of the worries that attended his course of apprenticeship. The general grounds covered by tlie lecturer were: Nature of bacteria, kinds, mode of growth, and produce tion; changes and fermentation produced, and meclianicisms of the. process; yeasts, mould's,- and other effects ; methods of cultivation and examining bacteria.

Particularising, Mr. Veale said that his lecture was not for the purpose of teaching anything about the practical side of dairying, but to give a bird’s-eye view of. the scientific side of the industry. Dairying was more closely connected than any other with bacteria, because milk was so subject to the breeding of it. Bacteriology involved bacteria, yeasts, moulds, and fungi. Bacteria consisted of minute, free swimming plants. Plants usually had a constituent, the greeii substance known as ehlorophyle. If they did not contain this they were either parasites or saprophytes Bacteria belonged to the latter class, being divided into (1) micrococci, (2) diplococci, (3) streptococci, (4) strapliylococci, (5) .sarcina, (6) bacilli mobile, (6a) bacterium non mobile, (7) spirillae. The speaker illustrated the cell formations of the divisions of bacteria, and their forms of- reproduction, the latter being by (1) simple fusion and (2) spore formation. The second form was general as a, protection or when- food was short. Spore formation was known as endogenous when it occurred within the cell, exogenous when by the construction of an outside cell, and anthrospore when. the whole cell becomes a spore. The minimum tempera, tuer for spore formation was just above freezing point (33deg. F.J, hence the preservation against decay by freezing. The best temperature for spore formation, or the optimum, varied, as low as 70deg. F. for lactic, hut usually from 90 to 100 deg. F'. Some bacteria had a much higher optimum,'i.e., lactobacilli of Yoghurt (Bulgarian hug). The thermal death point for bacteria varied from 140 deg. F for a' good many ■bacteria to 190 deg. F., which was: generally fatal except to spores. Anything organic formed food for bacteria. Milk was peculiarly suited to it, because it lacked no element which bacteria required. Growing bacteria produced a breakdown of the elements in which they increased, and they made food of the substance they broke down. In food the changes observed were fermentation, putrefaction, and the production of acids. Bacteria, and yeasts were once called organised ferments, and they were followed by the discovery of - unorganised ferments dr enzymes, such as the dinstate of germinating barley. Eventually the enzymes and bacteria merged, the proof of which came with the grinding of yeast, and by the use of compressed yeast. Important divisions of bacteria. occurred from the dairy point of view according to the enzymes secreted, the chief undesirable types in milk being lipolytic (fat splitting) andi proteolytic. The toxins of pathogehie bacteria were related to the enzymes of the non-pathogens. Passing to the study of bacteria, the speaker said that cultures could be produced in incubators. Gelatine was used to- assist the cultivation of bacteria. which grew in a low temperature, and agar-agar for those which grew at a high temperature. With the substances were incorporated beef broth, sodium chloride, peptone, sugars, an indicator, and water. One. of the lecturer;’si exhibit w r as a. tube of milk many months old which had not coagulated because the milk had been sterilised, and no bacteria, could get to it. Bacteria only moved, of its own accord in liquid, and some forms could not move even there.

Yeasts were usually recognised as a yellowish frothy fluid of characteristic smell. The essential and causative agent was an oval cell, bacteria of saprophyte order, one variety of which fermented cane' sugar, and another fermented: lactose. The latter variety liked acidity, and in its capacity to form gas and odour was a. clanger to cheese. The method) of reproduction was (1) by germination or budding, or (2) spore formation (distribution). Wild yeasts were smaller, and occurred in uncovered milk. The ingredients which the bakers’ used' were attacked by the yeast from the air, and did: not themselves contain the necessary bacteria. If starter culture were of too high acidity the yeast flying about in the atmosphere would lodge' in it. ] The cells increased by buds breaking j off the parent cell.

Moulds, said the speaker, turning to this head of his address, were fungi, or multicellular saprophytes. They ramified all over tlie iiutritivq material, reproduced by spores, and were responsible for various (fermentations. The commonest types were (1) monilia negra, the black spot on cheese which resell)Died an oval yeast; (2) oidium lactis, the white mould of sour milk, cream, and butter; and (3) penicilliuni glaueum, the common green mould of the curing room. Mould cultures would burst and scatter in a current of air, and, settling on cheese again, would grow. It was useless to dust or scrape the mould off cheese. Fumigation was necessary to cure a room of it. Moulds rarely penetrated: far enough into cheese to do it any harm, unless they got into a. deep crack. Some cheeses were ripened by the aids of moulds, e.g., French Camembert, Stilton, and Roquefort. In the first-named many fine holes 'were punched to let the mould in. Mould produced special flavours not required in Cheddar. Mr. Veale then concluded his address and invited, questions. Mr. G. Thorburn asked for an explanation of bitterness in cheese. iMr. Veale said he could not speak from his own observation ns to the cause of bitterness. Experiments mentioned in text books said it was due to one of the varieties of wild yeast. The affection was commoner in America than in this country. The scientific name of the bacteria responsible for bitterness was totula amara. Asked whether bitterness might be caused, by too- much salt, over-pasteur-isation, or rusty milk cans, Mr. Veale said that a certain amount of bitterness could be caused by contamination of milk cans or bare patches of copper if such were freely exposed to the sun.

Mr A. J. Hop croft asked whether, if a dairy factory were provided with an ordinary starter which did >iot function, the cause could be found by .an examination of the bacteria., The lecturer assured the speaker, that it was possible to examine the starter under a mieri scope and to see whether any extraneous matter was present in it.

In reply to Mr George Duncan, the speaker .said that an ideal method was to get the milk supply pure, so that the ordinary starter mixture would act upon it. The factory supply might, through no fault of the suppliers-, not be normal. Certain variations were/ beyond the ability, of the farmers to correct, such as the quality.of the land, and the methods by which it had- been cultivated. One manager had informed him that, although acidity had been as high as 118 deg., there had been no coagulation. Absence of coagulation was due to deficiency in calcium salts. Some milks _ had deficiencies, and others additional ingredients, which impeded' the starter. A lactic acid culture should then be developed which would overcome the deficiencies. Acclimatisation would help a starter to overcome unusual conditions.

Continuing on the -subject of starter milk, Mr. Veale said bringing this to a boiling temperature would -give the cheese an unpleasant .burnt, flavour. Lower temperatures were better for the development- of bacteria. In answer to Mr. G. Wood, as_ to whether heating milk for pasteurised eheddar cheese to 212 deg. would have a detrimental effect on the body of the milk, Mr. Veale said that any beating above 150 deg. would' be injurious. American authorities maintained that' pasteurisation of milk for cheese was not a success. t

Asked what- was the best temperature for setting starters, Mr. Veale said from 70 deg. to 76 deg. Allowing for a- cold night, there would be no harm in settins: at 78 deg. Mr A. J. Hoperoft inquired, whether Mr. Veale would make a suggestion regarding the use of machinery to bring up the temperature of starter _ milk quickly as against bringing it up slowly in the' cans. The reply was to the effect that quick heating was advantageous. If the heating was slow the bacteria was capable of forming spores, which would he able to resistthe heat.

The chairman asked if the lecturer knew anything about the new yellow mould which had come here lately. The questioner said he had seen it while watching cheese being loaded on a. boat in Wanganui. Mr. Veale said he had no samples, hut had discussed the matter with Mr., Hodge, of the West- Coast Freezing Company. A black mould was associated with the new vellow one. The latter had developed late in the year. A hearty vote of thanks was passed to Mr Veale for his address. •