DAIRY RESEARCH INSTITUTE

Otago Witness, Issue 4033, 30 June 1931, Page 17

DAIRY RESEARCH INSTITUTE

ADDRESS BY PROFESSOR RIDDET. CEESE AND BUTTER EXPERIMENTS. During the past dairying season the Dairy Research Institute has continued ex-, perimental work on the manufacture of butter and cheese. Most attention has been directed to cheese, but some effort has also been devoted to butter problems. The cheese investigations were at the outset of experimental work in. 1929 specially concerned with openness in texture; but as time has progressed these have developed into a study of cheese quality in general, since the consideration of texture is inseparable from that of other factors. Thus results have a direct bearing upon flavour, body, texture, colour, and maturity. Special attention has been given to factors bearing upon openness, harshness of body, and mature flavour, which are all engaging the attention of those interested in the cheese industry. Butter experiments have been mainly concerned with the use of starters to produce a mild® full flavour without endangering keeping quality.

/ — An outline of the work done was given to the delegates to the conference of the National Dairy Association at New Plymouth on Friday by- the director of the institute (Professor W. Riddet). PASTEURISATION IN CHEESEMAKING.

“ Since fully 90 per cent, of New Zealand cheese factories pasteurise their milk, whilst most other countries selling produce in the British market manufacture cheese from law milk,” said Professor Riddet, “the Dairy Research Institute began its investigations with a study of the effects of pasteurisation of milk on cheese quality. The results are interesting, particularly since the belief has often been expressed of late that all present difficulties are attributable'to pasteurisation. The experiments extended from January, 1929, till May 1, 1929, and from January, 1930. till May 1, 1930. In all cheeses from 109 days’ make have been compared. The following conclusions have been drawn from these experiments:— 1. Pasteurisation of milk has neither caused nor prevented the devilopment of mechanical or slit openness. Even when | high pasteurising temperatures (over 165 deg F.) so altered the curd that it was brittle, lacking in cohesion, and would not cheddar properly, the mature cheeses did not differ from the corresponding raw milk cheeses in closeness. During the trials close or comparatively close cheeses were made on some days and open cheeses on others. When open texture apppeared in the make of any one day, it affected both raw and pasteurised milk cheeses on the average, to the same degree. 2. Differences in flavour have been observed. These are dependent on the temperature of pasteurisation and the purity of the milk supply. Taking the whole series of experiments into consideration. the cheeses from milk pasteurised at temperatures not exceeding 160 deg F. graded the higher at the age of three to four months, being then on the average cleaner in flavour. Out of a total of 68 cases, the flavour of the raw milk cheese was preferred in seven cases, the pasteurised in 41 cases, and they were equal in 20 cases. A certain number were held till they were more mature, when those cheeses made from finest grade raw milk developed the fuller cheddar flavour. On the other hand, cheeses made from raw milk of lower quality had less desirable flavours than those rhrt'de from the corresponding pasteurised milk. ~ 3. Differences in body were brought

about by pasteurisation. In most instances, when a pasteurising temperature of more than 165 deg F. was used, the body of the mature cheese was soft, pasty, and gritty. At temperatures of less than 165 deg F. no marked difference in body were observed. In total grading points of 41 pairs of cheeses, the raw mUk cheese graded better in six cases, the pasteurised in 20 cases, and they were

equal in 15 cases, when the pasteurising, temperature was 160 deg F. At a pasteurising temperature of 175dcg F. in 15 cases the raw milk cheese graded better in 11, in three cases the gradings were equal, and in only one case was the pasteurised milk cheese preferred at this temperature. 4. Pasteurisation effected a better distribution of ‘ fat throughout the cheese without increasing fat loss. Cheese made from high testing whole milk frequently contained visible pockets of fat, while that made from the same milk after pasteurisation showed much fewer, and often, no fat pockets. 5. Yields were affected by’ pasteurisation. At temperatures of from 150-165 deg F. pasteurisation of milk increased the cheese yield on the average by’ 0.02 per lb fat based on 14-day weights, At a pasteurising temperature of 175 deg F. the cheese yield was increased by 0.1. It is to be noted that this increased yield was entirely offset Ay marked deterioration in quality. 6. The yellowish colour of cheese made from high testing milk was slightly reduced bi pasteurisation of the milk. 7. No benefits were derived from pasteurising milk in a cheese vat by the batch or holding method, which requires the milk to be held for 30 minutes at a temperature of 140-150 deg F More difficulty’ was experienced with cooked flavours in the immature cheese and bitter flavours in the mature produce, and more time was taken up in the process.

PRACTICAL RECOMMENDATIONS Any move in the direction of the manufacture of raw milk cheese must be preceded by an improvement in the raw milk supply, which, it seems, can only be obtained by milk gracling and differential payment based on grade,” said the speaker. “ This preliminary is absolutely’ essential. Otherwise produce will lack uniformity in qualitv from l day to day consequent on the variability of the purity of the milk supply with weather and care in production, and considerable difficulty will be experienced with unclean flavours and fermentation openness. Raw milk cheese is particularly’ subject to rancid and ‘ stinker ’ flavours when the. milk quality’ is not sound. Besides, fooa flavours are more distinct in raw milk cheese. After the milk supply has been satisfactorily cleaned up, the possibility of development of numerous fat pockets should be avoided by not manufacturing into raw milk cheese milk of such test that will produce marked evidence of these. Factory managers must use discretion in this, being guided by the maximum test of the milk they may safely use as the season progresses. Meanwhile, any widespread return to raw milk cheese manufacture is not advisable till the milk supply is adequately improved, as indicated by grading over some period of time. Furthermore, particular attention should be devoted to temperatures of pasteurisation. Flash temperatures l<?ss than 150 deg Fahr, should be avoided; but temperatures should be kept as near to 150 deg Fahr, as the purity and flavour of the milk supply will allow. Since it is known that high pasteurising temperatures definitely spoil true. Cheddar flavour and it is equally well realised by makers that temperatures are subject to fluctuation in the process of pasteurisation, special care should be taken to avoid these fluctuations and to be prepared for their results.'

AVOIDING FLUCTUATIONS.

“ In addition to careful control of the flow of milk and steam to the pasteuriser, great care should be taken to use

accurate thermometers,” said Professor Riddet. “ Many cheap types with thick glass have been shown in work at the institute to be not sufficiently sensitive to register momentary fluctuations in temperature; many gallons of milk may pass through the pasteuriser at a higher orlower temperature before the mercury column registers the alteration. Thus good sensitive thermometers should be used. Better still are good and accurate types of long distance recording thermometers.

/QUALITY OF MILK SUPPLY. All research investigations emphasised the importance of the quality of the raw milk supply, said Professor Riddet. There was no definite evidence of the influence of the chemical'quality, though apart entirely from consideration of the test of the milk and the casein it contained, there was considerable reason to suspect that the chemical condition of the casein and mineral matter had a considerable influence on the resulting cheese. There was ample evidence, however, in support of the necessity for a pure milk supply, namely, one as free as possible of germs. This was so whether the milk was pasteurised or not before it was made into cheese. It must be remembered that germs commence their destructive work on the milk solids as soon as they entered the milk and they multiplied very rapidly, particularly in uncooled milk. Although pasteurisation subsequently destroyed many of these organisms, it could not restore the affected milk solids to their original state. Pasteurisation was no excuse for lack of care in producing and handling milk. MILK GRADING. Speaking of milk grading Professor Riddet outlined the results it should have. It ought to raise the average quality of the raw milk supply and give the factory manager a chance of improving cheese quality. It should assist in uniformity’ of manufacture from day to day. It would improve cheese flavour, under good conditions of manufacture. It would particularly improve the flavour of raw milk cheese. It could not be expected to eliminate cheese faults completely because there are in milk some factors affecting quality that have to date been unidentified. It should considerably assist in raising average quality. It is worthy-of mention that milk grading is practised widely in Denmark and its adoption is being urged in Canada.

OTHER CHEESE EXPERIMENTS. During the past dairying said Professor Riddet, cheese has been raaxL from low-testing, high-testing, and stand' ardised high-testing milks, produced on the same farm under identical’ conditions. A long series of investigations has also been commenced upon starters. This starter work is most important, because good milk and good starters are the foundation of good cheese. Some peculiar experiences have been encountered in the propagation of starter cultures in the dairy factory. They are very sensitive to temperature and acidity changes, thus every factory should have proper facilities tor preparing and caring for starters. Attention has also been devoted to the influence of pressure on cheese texture and to factors affecting pressure. The cheeses made in the above experiments have not all .yet been examined at maturity, and until the full series of experimental results are to hand, no opinions can be safely expressed. -

The institute is collaborating with Air Morgan, of the Dairy Division, and with Air Yeale, of the Hawera laboratorv, in regard to the cause of muddy, bleached, and pink discoloration'. While no definite cause has yet been shown, it is evident that as Air Alorgan has shown the trouble arises when cheese rinds are cracked, and discoloration follows openings in the cheese. FURTHER RESEARCH NECESSARY. The gross effects of feed, top-dressing, machine milking, and several phases-of manufacture, have yet to be tackled, but are not being overlooked, he continued. The work of the institute during the past three years has been directed towards a solution of some of the problems in the cheese industry by the introduction of some variations in the process of manufacture. These studies have yielded some positive and definite results which have been communicated in addresses to the N.D.A. conferences at Hamilton and in the present discussions. The problems have also been clarified by the elimination of a number of suggested causes for deterioration in cheese quality. By the work carried out to date we are led to the conclusion that it is essential to carry out some fundamental studies of the changes taking place in the cheese-making process simultaneous with the attempt to overcome present difficulties in a straightforward, practical manner. The fundamental studies have already been begun, but the problem is so complex that no results are yet available for report. In-

vestigations are already being made of the effect of abnormal milks, and on the chemical changes that take place in the cheese-making and curing process. The fundamental work is being assisted by a grant from the Empire Marketing Board. With continued moral and financial assistance from producers and factories, this work must, in the long run, help the industry. . BUTTER EXPERIMENTS. “During the 1929-30 season, experiments were carried out with the manufacture of butter from cream to which starter was added,” said the speaker. - “ The highest degree-of acidity in the cream was .17 per cent. Both fresh cream and neutralised cream were used. The results showed that, when the butter was graded in London at three months old, the starter butter made from fresh cream scored highest in 15»churninge; the fresh cream butter in eight churnings, and the scores were equal in 14 churnings. At this age, there was a little in favour of the starter butters when fresh cream was used. When these butters.'were held in New Zealand for six months the starter butter scored highest in four churnings, the non-starter in five churnings, and equal in 28 churnings. Thus, after six months’ storage -period, there was no material improvement from the use of starter. The butter made from neutralised cream scored differently. At three months old in London the starter butter ecored highest in seven churnings, that without starter in six, and they were equal in 24 eases. After six months’ storage in New Zealand the starter butter was highest m three cases, the non-starter in three cases, and equal in 31 cases. Thus no advantage was derived from the addition of starter to neutralised cream. In the season 1930-31 lots of butter were made from cream in which much higher degrees of acidity were developed. These ranged from .20 to .46. The detailed results have not yet been received, from England, but cabled advice indicates that some of the starter butters developed off flavours and graded much lower than the fresh cream butter. The results will be made public when available. The institute has had,, during the season, the hearty co-operation of the Massey Agricultural College, the Department of Scientific and Industrial Research, the Dairy Division, the Dairy Board, the laboratories of the New Zealand Co-operative Dairy Company, and’ the Taranaki Federation of Co-operative Dairy Factories, To all of whom thanks are expressed.