CHECKING UP ON CHEESE YIELDS.

Horowhenua Chronicle, 29 April 1937, Page 2

CHECKING UP ON CHEESE YIELDS.

WORK OF DAIRY DIVISION. I EFFECT ON PAY OUT Cheese factory managers present at the Dairy Research Institute "week" yesterday were interested in an address given Mr C. Stevenson, of the Dairy Division, on cheese analysis as a check on butterfat recovery in relation to fat credited. Dairy farmers supplying cheese factories will also be interested in the work that is being done in this direction as it has an important bearing on pay-outs. The work of cheese analysis for moisture and fat, said Mr Sthevenson, has been carried on by the Dairy Division over a number of years, the first work along this line being done under the supervision of Mr. W. E. Gwillim. The work of cheese analysis in the earlier stages was undertaken chiefly with a view to making comparisons of cheese quality in relation to moisture and fat content. At the same time, however, a large amount of valuable information was made available in connection with cheese yields, it being definitely shown that many of the high yields of cheese per pound of butterfat, claimed by cheese companies at that period, could not be substantiated by the percentage of fat incorporated in the cheese. Some of the records obtained through this earlier work of cheese analysis are particularly interesting as showing the large increase in the fat content of cheese and corresponding decreases in moisture content, which has taken place over a comparatively short period. Ib the year. 1913 North Island cheese showed an average fat content of 33. S per cent, and a moisture content of 3(5.1-1 per cent., while at the present time the average content is, fat 36.4, moisture 34.5. Probably in individual districts such as Taranaki, the increase in the fat content of cheese over the period referred to would be considerably higher than the average figures shown.

The work of cheese analysis for moisture and fat content received much greater prominence during the period 1929-31, when the manufacture of standardised ciheese was permitted, it being necessary to provide a definite check on the fat in water free substance of all standardised cheese forwarded for export. This work was later extended and developed along the line of a definite check on cheese factory yield*. As already pointed cut, even tn the earlier stages of this work, it was evident that many of the yields claimed by cheese companies could not be legitimately obtained. It became therefore abundantly cliear that in order to prevent some dairy companies from obtaining an unfair advantage over others in this respect, some accuxaie system of checking up on cheese factory yields was necessary. The necessity for a cliecfe. of this description is probably greater at the present time than ever before, as, under the dairy produce purchase scheme, recently instituted by the New Zealand Government, all dairy companies manufacturing cheese are paid at a uniform rate per pound of cheese. There will, of course, always be quite legitimate discrepancies in yield, and a corresponding difference in tihe price paid per pound of fat at cheese factories, owing to the variation in the fat content of the milk handled a different factories, but the work of the division is designed to prevent as far as possible discrepancies wlhich cannot so be accounted for. The basis of the check on yields is carried out by the divison is quite simple, being merely a comparison between the butterfat recovered or incorported in the cheese, and that originally credited to milk suppliers, with, of course, reasonable allowance for losses in manufacture, which should not under normal conditions greatly exceed an average of 7 per cent., with a limit of variation of from 6 to 8 per cent.

Mr Stevenson also made reference to tilie question of whey fat recovery, closely allied to that of fat losses. The .whey fat recovery will be from 1.75 to 2 per cent, less than the total fat lost : as this amount, from If to 2 per cent, is no recoverable in seperation, lost in pressing, etc. Therefore a factory showing a manufacturing loss of 7 per cent, should show a whey fat . recovery of from 5 to 5.25 per cent. Whey fat recovery therefore under normal working conditions should amount to from 5 to o per cent, of the total fat credited. A case recently came under his notice m connection with returns from factories, where the results from a particular factory quite corresponded with the Di vision's analysis so far as fat recovered and yield was concerned, this factory showing a fat recovery of 93 per cent, of the fat credited. This, of course, showed a manufacturing loss of 7 per cent., yet the original return received from this factory showed a whey fat recoveiy of 8 per cent., or 1 per cent, more tihan the total amount of at lost. This return was, of course, obviously incorrect, and it was difficult to see how such errors occurred. The cheese factory referred to sold the wihey cream to a neighbouring butter factory, and i f was scarcely conceivable that this company was crediting the cheese company with more than the amount of ivhey fat supplied. In carrying out this work, tihe figure with which the Divisonal officers are most closely concerned is that of the percentage of fat contained in the cheese, and a large amount of experimental wori has been carried out from time to time in order to ensure the maximum degree of accuracy in this connection. Getting Composite Samples In the winter of 1935, experiments were made in testing cheese for fat and moisture from composite samples, care-

ful comparisons being made between averages obtained by testing separately plugs drawn from a consignment of cheese, and tests made from a composite sample of the same plugs. The results of these comparative tests were so similar that it was evident that quite satisfactory results would be obtained with composite samples, and in addition much more work could be accomplished in the same tie, as under the composite method one test is sufficient to include each vat of cheese in every consign ment coming forward. In December, 1935, this method sampling cheese was adopted in all grading stores for a limited number of samples, and later, in the spring of 1936, the provision of ad-" ditional assistance in test rooms made possible the adoption of a system whereby a test for fat is obtained of eacih vat of cheese passing through the various grade stores, by means of a composite sample. The method of taking composite samples is as follows: The set of plugs drawn for grading are first examined for closeness. Then with a special too, a uniform sample is cut from each plug, the whole representing a composite sample of. each factory's consignment of cheese for that day. Ths portions cut from each plug are placed in a bottle, which, is plugged with -J rubber stopper, until tested. Prior to testing, the samples are passed through a grinding machine and afterwards thoroughly mixed. 9 grams of the mixed sample are then weighed to a 50 per cent, test bottle and tested for fat j.n the usual manner. Method of Calculation

lii calculating the amount of fat incorporated in the cheese, the factory yield is multiplied by the percentage of fat found in the cheese. If a cheese contained 37 per cent, of fat, and a factory claims a yield of 2.5 pounds of cheese per pound of fat credited, it .s obvious that this 2.5 pounds of cheese contains .925 pounds of fat or 92.5 per cent, of the original fat credited, thus showing a manufacturing loss of 7.5 per cent. Should, however, a claim of 2/3 pounds of cheese be made, and the fat in the cheese remain at 37 per cent., each 2.6 pounds of ciheese would contain .926 pounds of fat, or 96.2 per cent, of the original fat. This latter would be obviously incorrect, as a manufacturing loss of only 3.8 per cent, is shown. Such discrepancies as this are in many cases due to the inaccuracy of the returns furnished by dairy companies. For the purpose of a check on yields as carried out, the Division required from dairy companies a correct monthly return showing: The pounds of milk credited for cheosemaking; pounds of fat credited for oheesemaking; pounds of cheese made for the month; yield of cheese per pound of butterfat,- percentage of whey fat recovered. In returns to date, in connection with this work, considerable discrepancies were shown, many dairy companies apparently having incorporated in the cheese considerably more than 100 per cent, of the total fat credited to suuppliers. This, of course, was obviously impossible, and it would appear in many eases errors had been made in the returns received from dairy companies, particularly with regard to weights of cheese. Begulations gazetted in October, 193(3, provided that the weights of cheese returned by dairy companies in this connection shall be packed weights. A period up to 21 days after tihe end of each month was allowed for the fur nishing of this return, which must include all cheese made for eac/h month, whether for l'ocal trade or for export. In carrying out a test for check on yields, the only means of arriving at the amount of fat incorporated in the cheese was by multiplying tihe weight of cheese made by the percentage of fat found in the cheese. It would therefore be evident that it was most essential that weights of cheese, as returned by dairy companies, must be accurate. In one case, the weight of cheese was estimated at 82 lb. for each cheese made. The average packed weights of the same cheese were later found to be 80-i lb. so that in tliis case the original return showed an excess weight of 14 lb. for each cheese made during the montih. In some cases green weights, or weights taken at the time the cheese was removed from the press, were submitted in these returns. Such weights are obviously useless for cihecking- purposes, as no dairy company computes yields on this basis. Errors in returns of butterfat credited have also been noted. At one factory, owing to a break-down in the machinery, it was necessary to separate the milk for two days. The fat separated some 800 lb., was credited to the cheese account and returned to us as fat used for ciheese ■ making. Quite naturally, in this ease, there was considerable discrepancy be tween our cheek results and those actually obtained at this factory.

Care Needed in 'furnishing Returns "I would like to take this oppo:r trinity of impressing upon those responsible, tihe necessity for extreme care in furnishing absolutely correct returns in this connection, and in many cases the need for greater promptitude in forwarding these returns to the grading stores each month, within tihe prescribed period," added Mr Stevenson. '' In some cases where returns of cheese are known to be correct, and discrepancies between our check and factory results are still in evidence, such discrepancies will probably be traced to inaccurate work in dairy factories in connection with fat tests in milk, or incorrect weights in milk credited to srppliers. For a number of years the Division has carried out a system of checking milk fat tests at dairy factories, but owing to the limited time at the disposal of our field officers, this work was somewhat restricted. The appointment of a number of additional officers in the spring of the present season has, however, greatly facilitated the extension of this, branch of the work. In following up discrepancies

shown under our analysis,, much, inaccurate work has been discovered 111 factories. Our officers have on occasions found milk fat tests being read as much as .2 lower than the correct reading. In such cases, the yield as shown by the factory was higher than could be substantiated by the fat incorporated in the cheese as shown by our analysis, and fat losses too low. On the other hand, incredible as it may appear, we have found factory milk fat tests being read ,2 higher than the correct reading. Here again, of course, factory results would not agree with "our analysis, yields being too low and fat losses abnormally high. Although not so prominent a source of error as fat testing, we have from time to time found discrepancies due to inaccurate milk weights. In this connection, I am of the opinion that factory milk scales do not generally receive sufficient attention. I would suggest that all factory milk scales be thoroughly overhauled and adjusted, at least once every year." The speaker added that in examining the monthly returns received from various grading stores in connection with this work, it was noticeable that there had been an appreciable reduction from month to month in the number of cheese factories showing abnormal returns.