Milk and Cream Grading

New Zealand Journal of Agriculture, Volume 60, Issue 1, 15 January 1940, Page 11

Milk and Cream Grading

Contributed by the

DAIRY DIVISION.

THE object of grading milk and cream is twofold. It serves to keep the supplier advised regarding the quality of his produce, thereby giving him an opportunity to correct any defect, and provides the means of inflicting the penalty without which any regulation is impotent. The deduction from the butterfat payment for second-grade milk and cream cannot be regarded as an indication of the difference in value between those two qualities. For instance, the inclusion of 201 b of garlic-flavoured cream in a churning of 20 boxes of butter has been known to reduce the quality to second-grade, which, on the differential of Jd per lb allowed at that time, . amounted to 46s Bd. The deduction of the 81b of butterfat which the cream contained amounted to only Bd. The loss in this instance was easily calculated, but there are many cases in which the secondary qualities are mixed with the higher-grade cream, and although the butter made may not be poor enough for second-grade, there is a general reduction in quality which is not compensated by the small amount deducted from the second-grade butterfat. There may be, in addition, an inherent unsoundness in the butter which is not noticeable at grading, and as an. instance of this we have the experience in connection with the manufacture of unsalted butter, for which purpose only cream of the highest quality can be used. Milk for cheese-making is, generally speaking, not graded until after the manufacturing process is well advanced, so that segregation in this case is not possible. Start of Grading Cream grading was undertaken by individual dairy companies on a volun-

tary basis in the first instance, and the experience so gained led to the demand from the industry for both milk and cream grading. Cream grading was made compulsory in 1926, but milk grading was not started until 1931. In both instances the grader is required to hold a certificate which is issued by the Director of the Dairy

Division after the applicant has been examined and passed as competent by an instructor. This certificate may be cancelled if for any reason the Director is of the opinion that the grader is no longer a fit and proper person to be entrusted with this responsible work. In the case of milk for cheesemaking, two grades (first and second) are compulsory and finest grade is optional, but milk for butter-making must be graded into finest, first, and second grades.

The standard of grading for milk for cheese-making is that, if manufactured separately without pasteurisation, it would make cheese of the quality assigned to it. The standard for milk and cream for butter-making is that, if manufactured separately by the usual approved methods, it would make butter of the quality assigned to it. Method of Grading The method of grading varies according to the use which is to be made of the milk. Thus, milk for cheesemaking must be based jointly on the curd test, and either the reductase or the microscopic tests. Milk for buttermaking, which includes milk supplied to a casein station, a dried milk or a condensing factory, must be graded by (a) the curd test or (b) the reductase test combined with the senses test; (c) the microscopic test together with the senses test; (d) the curd test together with the reductase or the microscopic test. It will be noted that the provisions are wide enough to cover all the methods which have been used from time to time, but in actual practice it can be accepted that milk for cheesemaking is graded by the curd test plus the reductase test, while milk for butter-making is graded by the reductase test plus the senses test. The senses test in this case means that milk which has not decolourised in the time fixed for finest or first-grade may, after those periods have elapsed, be graded down to first or even second-grade by the sense of smell. There is a further provision that milk which is second-grade by the sense of smell or taste —sour or turnipy milk, for instance or milk which is shown to be dirty by the sediment test, which is a test for actual dirt, may be put

into that class without the application 1 of any further test. < In general, the grading of cream is J carried out solely by the senses of taste i and smell, although the grader is quite ' within his rights in degrading cream which contains visible dirt, or is ( churned, ropey, curdy, etc. . Cream ; must be graded within three hours of , being received at the creamery into finest, first, or second-grade, and if so desired the grade of either milk or cream may be indicated by points. Right of Refusal Under certain conditions the manager has the right to refuse to accept delivery of either milk or cream, and is, in fact, required to do so if, for instance, it is affected by putrefactive decomposition, contains or has contained any bird, etc., is affected with the flavour of any disinfectant, kerosene, etc., or contains anything which renders it unfit for the manufacture of a product

for human consumption. In all these cases he shall forthwith add to such milk or cream a sufficient quantity of methyl violet to colour effectively the whole of it. He may also refuse to accept milk or cream which he considers to be below second-grade and also milk or cream which, if mixed with the rest of the supply, would reduce the quality of the whole of the produce made from it, but in this case he can use his discretion regarding the addition of colouring matter. The responsibility for the correct grading of milk and cream rests in the first instance on the grader, who must, in the case of milk, indicate the grade on the sheet or. docket on which the delivery is recorded. In the case of cream, he must enter the grade on a docket, which shall be initialled or marked and be delivered or sent to the supplier after each delivery. This responsibility is shared by the manager

who, with the grader, is responsible to the cheese or butter instructor in charge of the district. This instructor, with the Special Dairy Inspector, exercises such supervision over the work as may be necessary to maintain a correct standard of grading. Standard of Grading From the foregoing it will be noted that the standard of grading must be based on the quality of the product which can be made from the milk and cream received. This being so, the grader cannot take into account the disabilities of the supplier in regard to distance from the factory, inferior pastures, and so on, but must confine himself to the quality from a manufacturing point of view. In practice, the standard is actually set by the class of milk or cream delivered by the best suppliers. Grading without a penalty would have little effect, and the deductions provided are designed to keep an even balance between milk for cheesemaking and milk and cream for buttermaking. In all cases they are the minimum differentials which must be made. Thus, the deduction from butterfat for milk graded second-grade for either butter- or cheese-making must be al least jd per pound, while the deduction from butterfat for cream graded ■ second-grade must be at least Id per lb. This apparent discrepancy is due to the fact that cream from milk which would make second-grade cheese will frequently make first-grade butter, and if Id deduction were made from, milk it would be an inducement to a careless supplier to supply cream. The extra payment for finest-grade butterfat is optional in the case of milk for cheese-making, but must be at least Jd per lb of butterfat for butter-mak-ing. All deductions and additions must be made on the first payment, and all subsequent payments must be evenly distributed over all grades of butterfat. Suggestions which will assist in the production of high-quality cream, most of which apply equally to milk, will be found in Bulletin No. 139, which will be posted by the Department of Agriculture, Wellington, on application.