OPENNESS IN N.Z. CHEESE

Waikato Times, Volume 107, Issue 18027, 23 May 1930, Page 3

OPENNESS IN N.Z. CHEESE

Within recent years there has been a continual increase in the number and seriousness of complaints against the body and texture of New Zealand cheese exported to England, and it may be fairly stated that looseness and openness are now the outstanding defects of our cheese. The fault it not one of recent appearance, having been encountered for many years, but a number of causes have been cooperating t 6 make its occurrence more ' and more obvious, until now .there is no gainsaying the fact that openness in cheese is responsible for much loss in popularity and considerable reduction in price. Openness in New Zealand Cheddar cheese is not a new defect, and the writer will not endeavour to maintain that some new and highly abstruse condition calling for elaborate research has suddenly arisen to cause the fault. On the contrary, openness has always been with the cheesemaker. It is an extremely common trouble, and arises from a large variety of known causes. Possibly also some unknown factors may be operating to-day, but there is far more likelihood that our cheese is suffering from the combined effects of a number of causes, all operating in the one direction. The gradual accumulation of these conditions has been so slow and insidious that no-one has marked its progress, but gradually the combined effect has become unmistakable. Most of these causes of openness are well known, and each in itself may be comparatively trifling, but the peculiar and distinctive lines along which the New Zealand cheesemaking industry has evolved have brought about a steady accumulation of effect such as could not occur in any other country. Hence has arisen our national problem. This paper is an endeavour to review some of the known causes of openness, and to show to some extent how the present position has been created. TYPES OF OPENNESS. .Openness in cheese may be subdivided into three classes, namely:— 1. Openness due to fermentation, ai.d arising from the action of microorganisms. 2. Mechanical openness, the result of simple failure of the pieces of curd to knit together. - 3. The state or condition of export ‘ cheese which results in quick drying out, and the formation of large and unsightly cracks soon after a cheese is cut and exposed for sale. Openness Due to Fermentation. 1. The first and best known type of this class of openness is that which is due to the infection of the cheesemaking milk with gas-forming organisms, and which is characterised by the formation of innumerable holes throughout the body of the cheese. These holes, which are usually perk fectly spherical in shape, have a polished interior caused by the pressure of the gas liberated by the bacteria, and may vary in size from about the size of a pin’s head to about several millimetres in diameter. The most advanced forms of gassy curd will float in the whey in the factory, although the gas is frequently dissipated by deep piling during cheddaring, and by thorough aeration of the milled curd, so that the resultant may not be very open in texture. ' The worst type of bacterial openness is that which develops gas during the curing of the cheese, sometimes causing it to swell to the extent of bursting the bandage. Since the gas is the product of fermentation of the lactose of the whey, it follows That such an action can take place only in a cheese containing an • ..excessive proportion of moisture. Actually the majority of cheese curds contain a certain number of gas forming bacteria, and the tendency of the cheese to swell and become distorted during curing is a measure of the extent to which the cheesemaker has endeavoured to exceed the normal percentage o,f moisture. Actually, massive inoculations of milk with gas forming bacteria are now very rare, and this variety of openness, while sometimes occurring, has no bearing upon the national problem. 2. A second type of fermentation openness is that due to the action of •- yeasts. This action is invariably delayed, and never gives rise to a floating eiird in the factory, owing to the slower rate of growth of these organisms. The holes produced in the cheese during curing are never of the \ small pin-point variety, but are larger, often spherical, but frequently associated with mechanical openness, thus producing irregularly shaped openings. A sweetish fruity odour due to traces of alcohol and aromatic esters is associated with this type of openness. Yeasts, which are responsible for this class of fermentation openness, are universally distributed in nature, and may infect the milk of any supplier if equipment is not in the best of order. It is extremely common to find factory whey tanks strongly infected. Whey which has stood overnight often froths and sometimes seems to boil, while occurrences of drunkenness and sudden death of pigs fed upon fermented whey are tolerably common. Owing to the practice of allowing the transport of whey .to the farms in empty milk cans it follows that there may be a general infection 'of a factory milk .supply with yeasts if cans have not been sterilised. Unfortunately many New Zealand factories cause trouble for themselves by serving out so-called “boiling I water’’ to suppliers for use at home for cleaning milking machines and cans. Where this pernicious practice sterilisation is impossible, and ’thus the infection of cheese making milk with yeasts is perpetuated. The isolation of yeasts from any sample of New Zealand factory cheese is practically a certainty, and where moisture conditions are favourable, *eome fermentation must occur, either

SCIENTIFIC INVESTIGATION. DEFECTS IN FACTORY PRACTICE. REMEDIES SERIOUSLY NEEDED. The Federation of Taranaki Co-operative Dairy Factories has Issued the report of Its research chemist (Mr P. O. Veale, B°A., M.Sc., A. 1.0.) on cheese quality and openness In cheese. Mr Veale has surveyed the whole process of cheeeo manufacture In order to show the oauses contributing to openness, and as a result he strongly advocates very drastic changes In the method of manufacture and also In the marketing of the finished produot. Mr Veale’s report Is very lengthy. We publish some of It below and further portions will appear dally. _

producing new holes, or enlarging others already there from mechanical causes. Complete elimination of yeasts therefore, would ameliorate, to some extent, the defect of openness by removing at least some of the holes classed as “fermentation* holes’ by grading officers. To this .end. therefore it would be advisable to prohibit universally the carriage of cheese factory whey in milk cans; also the supplying of hot water from the factory for cleaning purposes, and to insist that every supplier to a cheese factory shall have adequate facilities for the production of ample supplies of boiling water In the cowshed’. Mechanical Openness. During the latter part of the cheese making process, the large slabs of cheddared curd are milled Into small pieces, and, after maturing and salting, these small pieces are pressed together to make the final cheese. It is the failure of these small pieces io cohere together without gaps or crevices which gives rise to the so-called ‘mechanical openness’ of Cheddar cheese. It is well known amongst cheesemakers' that the ability of the small pieces of milled curd to knit together into a homogeneous mals is a function of the acidity developed in the curd, and occurs perfectly only when there is an exact relationship between the maturity of the curd and the degree of acidity developed at milling, and again at salting, and again at pressing. In the judging of the optimum stale of curd maturity lies the skill of the cheesemaker, but, if at the same time, the acidity is not correct, the Anal result will not be a perfect bodied cheese. It follows 'therefore that acidity development plays a most important part in determining cheese body, and the rate of acid development must synchronise with the biochemical changes taking place within the curd. If the development is too fast,.-the cheesemaker may do a little to curb It, but if It is too slow, he is powerless to accelerate it. Since lactic acid is essential to the maturing and keeping qualities of cheese, and is a safeguard against putrefaction, no maker would dare to manufacture his product! without its protective mantle of acidity. If development of acidity is too slow, he must wait, and if during this time the character of his curd changes, its cohering' power may be impaired, or even totally destroyed. It is proposed to show’ that the slow development of acidity In cheesemaking has an important bearing upon the occurrence of openness. Acidity Development. Vats.—Of recent years factory managers throughout New Zealand have become increasingly troubled with a type of milk which is extremely slow’ in developing acidity during cheesemaking. In some cases the in the whey, instead of increasing regularly, has remained almost stationary for hours, and such milks, for want of a better name have been called “non-acid” milks by our cheesemakers. The writer has found at least one type of non-acid milk to be due to massive inoculations of a variety of lactis-aerogenes . bacteria. These germs develop lactic acid at a very slow rate and their maximum acidity does not reach the curdling point of normal milk, i.e., does not exceed 0.5 per cent, to 0.6 per cent, lactic acid. Milk inoculated with a pure culture of these organisms will not curdle, but putrefies after a number of days. When present in large numbers, they tend to suppress the activity of the true lactic starter culture, and the result is that from about 0.20 per cent, to 0.40 per cent, the rate of development of lactic acid is very slow’. Gradually, however, the activity of the pseudolactic germs diminishes as their optimum acidity ap-< proaches, until finally the starter culture once more gains the ascendancy, although with impaired vigour. As a result the rate of acid development in the cheese cannot keep pace with the other chemical and physical changes.which are occurring, and the final acidity is often incompatible w’ith the body of the curd which has evolved. In consequence, the texture is generally very open, w’hile, in extreme cases, the pieces of curd have tended to fall apart even after long periods of pressing. ' Non-acid milk of the bacterial type is readily recognisable under the microscope. It is caused by massive inoculations of the deleterious germ, and is the result either of insanitary conditions in milking machines or cans which have allowed this particular germ to gain a strong foothold or else of poor methods of hand milking followed by lack of cooling, whereby an initially small germ population is increased enormously by multiplication. It is a fact that bacterial nonacid milk is usually rectified by a thorough sterilisation of equipment, oi' by attention to cleanly methods of milking followed by adequate cooling on the part of hand milkers. Frequently the trouble disappears automatically If the air temperature falls, and may reappear after a warm, muggy night for the reverse reason.

True non-acid milk is so annoying and vexatious to cheesemakers, and is' a cause of so much waste of factory time accompanied by poor quality cheese,,, that iU occurrence is much dreaded—so much, in fact, that other phenomena are sometimes mistaken for It. The result is that much open cheese is made, and many useless hours spent in the factory. When ti’ue non-acid milk Is present, the cheesemaker usually finds that on running off the whey at the end of the- cooking prooess the expected rapid increase In acidity does not take place, lie therefore stops the escape of whey, and" continues agitation of the curd in the whey for a period amounting to hours, until the starter culture begins to gain the upper hand, as evidenced by the increase in acidity, He then runs off the whey and completes the cheese-making process. Sometimes, however, the

expected increase in acidity during cooking and at the , ginning of the run-off is delayed for totally different reasons.' and cheesemakers aire deluded into believing that true non-acid milk is being ’handled. They extend the cooking period as usual, and keep the curd in the whey until its cheddaring properties are sei’iously impaired or even totally destroyed. In extreme cases, the curd loses all cohering pow’er, fails to Cheddar or to press, and never assumes the properties of cheese at all. In milder cases, which are extremely common, the development of acid in the whey is judged to he slow, me cooking period is prolonged, and the body of the cheese spoiled sufficiently to make it very open. In a subsequent paragraph, the method of measuring acidity in whey will be discussed, and the view will be expressed that cheesemakers are somewhat misled as to the acidity which they are measuring, thus leading them to take steps which result in spoiling the body of their cheese. For the present, however, we will discuss those cases where the acid development actually is slower than normal.

A case was recently investigated in which a cheesemaker was convinced that he was dealing with chronic nonacid milk. Microscopic examination of the milk failed to reveal the slightest defect, yet the rate of acid development in the whey was slow, and the cheesemaker adopted the practice of cooking for many hours over the normal period. This procedure so destroyed the body of his cheese that the product manufactured could not he pressed at all, and became unsaleable. Extended chemical examination of the milk responsible for the trouble showed everything present in normal proportion. There appeared to he some abnormality in the relationship of the mineral matter to the casein, if not an abnormality in the constitution of the casein itself, and the view was finally put forward, substantiated by some little experimental evidence, that the casein in this milk was not in its usual “balanced” state, but was more capable of combining initially with acids than with alkibes. In fact, by careful titration with very dilute acids, this milk appeared initially capable of absorbing measurable quantities of dilute acid without rising in titratable acidity. It was suggested, therefore that this absorption was occurring with the first acid developed by the starter culture in the vat, and that if acid could he supplied artificially the trouble would he overcome. After various trials, normal hydrochloric acid was selected, and eacli day the acidity of the milk in the vat was artificially raised, prior to setting, by slow and careful additions of normal hydrochloric acid. At first 0.25 per cent, calculated as lactic acid was aimed at, and this was gradually reduced until the normal acidity of 0.19 to 0.20 per cent, was established by titration. The cheesemaking process at once proceeded normally, acid development was rapid and regular, the body and texture of the curds was considered noticeably good in the factory, and the flavour and subsequent- grading of the cheese weie not in the least impaired. This procedure of artificial acidulation was continued for a number of weeks until trial showed that it was no longer necessary. Partial “Non-Acid” Milk. The, above examples of true and false non-acid milk have been detailed at some length for the reason that, although extreme cases may not be very widespread, mild or- partial cases of "both varieties are very common Every cheesemaker has experience of vats which are slow in developing acid in the whey, and which require cooking for 3J to 4 hours before it is deemed safe to run off the whey and proceed. Likewise every cheesemaker has experienced innumerable cases where the acid development in cheddared cheese and milled curd has faded away, and instead of reaching about 1 per cent, or more, has stopped in the vicinity of 0.70 to 0.80 per cent. In both instances the final acidity of the curd is not consistent with the body and texture evolved, and the result is that the curd partly loses its power to knit completely, and produces some mechanical openness. i

Slow development of acid in the whey may he due to a mild infection of non-acid germs, or may he caused by the partial absorption of the lactic acid by the casein. In either case, the trouble could be largely overcome if the cheesemaker could advance the acidity .beyond the point at which either action ceases. Probably for these very reasons,.old time cheesemakers insisted upon a ripening period of cheesemaking milk, and refused to add the rennet until an acidity of from 0.19 to 0.22 per cent, was present, and the power to increast in acidity had been demonstrated. New Zealand cheesemakers, however, have completely discarded all attempts at ripening their milk, and add the starter and rennet immediately their vat is full with sweet milk. They are probably not to blame, as the position has been forced upon them, not only by the shortening of working hours in the factory by labour unions, but also by the ever-increasing tendency of the suppliers to arrive late with their milk. Regulations which prescribe rejection of milk after a certain hour are difficult to enforce in these days of keen competition, and the writer has been present in large factoi’ies where'the last vat has been set after 11 a.m. Under such circumstances the ripening of milk seems out of the question, and yet, if the adverse conditions are present, it would' be better to wait for the acid development in the milk, when no harm can be done to the body of the cheese, rather than set with rennet and then impair the cheddaring properties of the curd by “hanging on” to it in the whey waiting for acid development. (To be continued.)