Starter Troubles Can be Overcome. Purity Essential

Taranaki Daily News, 30 September 1940, Page 13 (Supplement)

Starter Troubles Can be Overcome. Purity Essential

There are two fundamental processes in the manufacture of cheese. The first is the making of "junket" by the introduction of rennet to milk. and the second is Ihe development of acid in the junket. Then follow all the processes of manufacture of which many people in Taranaki know very little. They know, howevcr, that sometimcs the cheese they

buy'is more palatable to them than at others but why there should be a difference even in cheese from the same factory is more than the retailer can say. Very often the cause is found in what the cheesemaker calls a "starter," the agent that is to say, which starts the development of acid in the milk to which rennet has been added. From time immemorial up to .about 40 years ago such development of acid happened by chance. It was brought about by bacteria which happened to be present in the milk. With the study of bacteria in modern times came the possibility of spccially sclccted bacteria which would

produce acid in a more regular way and thus give a flavour to cheese that would vary very little provided other processes of manufacture were also standardised. The scientist supplies what he calls a "culture" of these chosen bacteria the cheesemaker puts the culture into a certain quantity of milk and calls it his

"starter" and has evcry reason to believe that he will make better cheese than that in which the acid was developed by bacteria which were found by accident in the olden days. A certain

quantity of starter goes into each vat of milk at the cheese factory and the process of manufacture has begun. But the starter cultures are absorbent Ihings. It was found that those received from the laboratory gave differing results and scientific investigation proved that this was due to the absorption of material from the air. Once the cause of the irregularity ' was known the remedy was within sight. The stcps taken in that direction are

detailed in a report made by Dr. H. R. Whitehead, Dairy Research Institute, and Mr. J. Thompson, manager of the Bell Block factory, where experiments were carried out. The report was submitted to the Dairy Board, which had provided financial assistance towards making the investigation. By the courtesy of the board, and of Profcssor W. Riddet, director of the Dairy Research Institute, the salient features of the report are reproduced as follows:— "Investigation of starter failures ovet Ihe course of several years had indicated that a major source of trouble in commercial factories was contamination of cultures with air-borne bacteriophage. It became evident that the surest way of eliminating this particular form of contamination would be preparation of the starter in some place where phage contaminated air could he excluded. In order to put the mattcr to the test undei commei'G'ial conditions for the guidance

of the cheese industry a building was erected at the Bell Block dairy factory where starters could be maintained in a phage-free environment. "The building," says the report, "is a simple rectangular structure 10ft. Oin. x 14ft. Gin. x 8ft. high (internal measurements). It is situated in an nngle formed by the walls of the main factory building and is 3ft. distant from one wall and 9ft. distant from the other. At the time when the starter building was planned it was considered that the rnost probable source of air-borne bacteriophage was dust from the vicinity of the whey tanks. Hence in deciding on the site emphasis was laid on the desirability of having the building remote from tho whey "tanks, rather than on distance from the factory. Subsequcnt experience has shown that a more important source of bacteriophage is the whey separator in the factory. Therefore an obvious improvement would be to increase the distance between the starter building and the factory. Needless to say a position to windward is still indicated wherever possihle. "The building is divided into two rooms, the larger for the preparation of the bulk starter, and the smaller for the inoculation and incubation of mother cultures. The only outer door of the building opens into the bulk starter room, while there is an inner door between the

two rooms. The bulk starter is prepared in twenty gallon cans fitted with sealedon lids, which are heated and incubated in a rectangular metal tub fitted with a domed lid which completely covers the cans during the sterilising process. The tub is lagged on the sides and bottom with cork. The removal of steam is effected by an exhaust fan fitted above the window in the larger room. The inlct for air is over the window in the smaller room. Thus Ihe air, drawn froip

the side of" the huildln^' remote fro'rh-tKe': factory, sweeps . through the motherculture room, under the connecting door and out by way of the exhaust fan. The 1 air is not filtered." The main lines of defence against airbome phage in the Bell Block room are: — Scparation of the building from the factory; covered bulk-starter tub; lids sealed on starter cans and wood plugged spouts; inner room for mother culture inoculation, providing extra sealing door between factory and mother cultures. "Three single strain starters from the institute were used, viz. HP, R1 and R6. A mixcd culture from another source was also kept for a time mainly in order to show that there was no difficulty in keeping it active. In the vats various combinations of the cultures were used. This was done more from the point of - view of observing the effect, if any, on the cheese, than for any other reason.

"There was not a single case of failure due to bacteriophage during the whole of the period under review. This was in marked contrast with experience in other factories in the New Plymouth district, more espccially in the early part of the season, when failures were common. The cheese-mnking process throughout the season at Bell Block was reduced to an almost regular routine. Variations in the running of the vats amounted at thc most to a differenee of ten minutes in the time required to reach a given acidity. Most of the variation was due to changes in milk composition as a result of weather conditions and progress of lactation. The three cultures were renewed from the institute several times. Most of these renewals proved quite unnecessary and nctually tlie original mother culture of HP was carried throughout the season. "Thc bulk starter showed a pcculiarity on two occasions, 'non-acid' milk heine the essential cause of the failures. The occurrence emphasises the necessity of using only morning s milk for - the preparation of starter. The growth of "non-acid" bacteria in morning's milk cannot procecd far enough to inhibit Ihe growth of starter organisms. Apart from these occurronces the bulk starter was normal throughout the season. "It was obviously of interest to know whether there was bacteriophage in the surroundings nt Boll Block during the dairying season and whether thc possibility for contamination of the starter existed. Otherwise there could be no assumption that the separate starter room was serving a useful function. since there do occur periods when factories can maintain starters sometimcs for months without trouble. under conditions which j do not appear safe."

The Bell Block factory was visited at approximately monthly intervals throughout the season and ample evidence obtained that the possibility for phage failures existed there and hence that the preeaulions taken served a useful purpose. "Although the systcm used at Bell Block eliminated phage failures throughout the season, the finding of phage in the air of the separate building on a few occasions indicated that the object of eliminating the possibility of contamination with air borne phage had not been completely attained. With rooms which are now being built at other factories two main modifications have been adopted in the hope of eliminating all traces of phage. (a) Distance between building and factory has been increased, in one case up to twenty-eight yards. (b) A system of air filtration has been installed. The air, drawn through filters, is driven into the building so as to main-

tain a slight positive pressure within it, and the exhaust air is arranged in such a way as to encourage the escape of steam from the building. "If by these means it should prove to be the case that phage is entirely excluded from the air, the only remaining possibility for phage failures will be contamination of the cultures (with whey for instance) as a result of improper handling. This personal factor. can, of course, never be entirely -eliminated. "The questions of starter mnintenance and cheese quality are separate and distinct. The cheese made at Bell Block during thc 1939-40 season graded excellently at New Plymouth, but we must emphasise that the trial was primarily concerned with prevention of starter failure. In so far as regular running of the starter leaves the cheesemaker more freo to exercise his judgment, freedom from starter failure will lead to improved

cheese q.uality. But there are so many factors which determine quality in cheese that it is unwise to assume too dircct a connection between fkeedom from starter trouble and high grading score. Regular running of the starter will undoubtedly reduce costs by eliminating overtime and reducing manufacturing losses and spoilage. "The use of the special starter room at Bell Block over a season of approximately eight months, was an unqualified success. The only trouble encountered (on two days) was npparcntly due to the use of some 'non-acid' milk for the preparation of the bulk starter. Thanks are due both to the Dairy Board and to the directors of the Bell Block Dairy Company for making it possible to eonduct this crucial trial on a commercial scale."