20-004 Code Vt. R. 20-021-004-X

Current through August, 2024

Section 20 021 004 - WEIGHING, SAMPLING AND TESTING MILK AND CREAM

APPROVED TESTS FOR BUTTERFAT IN MILK AND CREAM

The Babcock and Milko-Tester methods of testing for butterfat in milk and the Babcock method of testing cream are approved tests by the Commissioner of Agriculture to determine the quality of milk and cream with reference to payment for it when received or purchased.

The following revised regulations concerning the taking of samples of milk and cream for making the butterfat test, the making of the test, and the computing of results thereof, have been promulgated in accordance with the provisions of V.S.A., Title 3, Chapter 25.

All operators of licensed dairy plants that receive or purchase milk or cream on the basis of its quality as determined by the butterfat test and all licensed and certified operators of the butterfat test are hereby required to comply with the Vermont Statutes and with the following regulations:

Section 1 General Requirements

A. No person shall test milk or cream for butterfat in Vermont unless he has secured a certificate from the Commissioner of Agriculture certifying that he is competent to perform such tests, as required by Section 2724 Vermont Statutes.

B. Applicants for a certificate to test milk and cream for butterfat must apply on a blank furnished by the Commissioner of Agriculture and arrangements will be made for an examination.

C. In order for an applicant to qualify for a certificate to operate butterfat tests, he must first demonstrate his ability to test samples of milk or cream and also his knowledge of the fundamentals of the test by answering in writing ten questions furnished by the examiner. The ten questions will be chosen from the list published.

D. Each certified operator shall sign in ink his certificate and post it in some conspicuous place where he works.

E. An assistant or second operator shall be certified to operate the butterfat tests in each laboratory in case the regular operator is absent.

Section 2 Composite Sampling

A. It shall be the responsiblility of the licensed sampler to take a representative sample from each delivery of milk. Such representative samples may be combined into composite samples for each respective producer covering a period not to exceed sixteen days. In taking samples from each delivery of milk to be combined into the composite samples, the amount taken from each delivery of each patron should be in proportion to the amount of milk making up such delivery. In common practice, however, the weights of milk delivered from day to day by any given producer are reasonably uniform so that a daily portion of at least 10 ml., and not more than 12 ml., is added to the composite sample from each delivery.

B. If composite samples are maintained, two sets of sample bottles must be provided to make it possible to take samples of milk on the days that butterfat tests are made and also to permit holding the composite samples not less than twelve days after the close of the period as required in these regulations.

C. Composite samples of milk, the butterfat tests of which are used as a basis of payment for product delivered, must be taken of each pickup or delivery for the entire period that such payment represents. Such composite samples must not include samples of milk taken during another period of payment.

Universal Fresh Samples

A. After receiving permission from the Commissioner, a handler may elect to pay producers for milk by computing the average butterfat test of not less than three universal fresh milk samples taken in accordance with (B) below.

B. A representative sample shall be taken of each collection of milk and delivered to the plant receiving such milk or to other collection points suitable to the Commissioner. Not less than three of the samples (or six in the case of every-day delivery) representing at least twelve complete milkings may be tested for butterfat content within three days of the date of sampling. One third of the samples tested for butterfat content shall be selected from each ten day period of the month. If more than three samples are tested per month all tests shall be used in computing the average test for the month.

C. The remaining portion of the fresh milk samples tested for payment purposes shall be preserved intact for at least one day under refrigeration following original testing. The Commissioner may exempt licensees from this requirement on the basis of established adequate internal control. Such exemption continues in effect unless revoked at the discretion of the Commissioner.

Section 3 Approved Equipment for Sampling Milk

A. Composite Sampling by the Dipper Method

1. Sample dipper holding not less than 10 nor more than 12 ml.

2. Glass sample bottles with tight stoppers to prevent evaporation. All sample bottles shall be clean and dry at the beginning of the sampling period. The 8 oz. sample bottles with rubber stoppers attached are recommended. Each bottle must be numbered plainly. Numbers may be metal tags wired to the necks of the bottles or painted on the sides of the bottles. Marking the numbers on the stoppers is permitted and recommended if the stoppers are attached to the bottles. Composite sample bottles shall be numbered consecutively and the numbers shall correspond to the numbers assigned to producers. No bottle shall bear two different numbers.

B. Universal Fresh Sampling

1. Sample dipper, holding not less than 10 ml. or other sampling device approved by the Commissioner.

2. Sterile bottles or other sterile leak-proof containers of adequate capacity to provide for mixing the contents.

3. Daily samples shall consist of sufficient quantity so that 22 ml., remains after the butterfat test has been performed.

4. Samples shall be taken aseptically and maintained at a temperature above freezing and less than 40 [degrees] F. until analyzed.

5. Sample containers shall be identified with the producer's number in a manner approved by the Commissioner.

Section 4 Care and Holding Of Samples

A. Sample bottles shall be clean and dry when placed in use. All stoppers shall fit tightly to prevent evaporation from the sample or adulteration.

B. Samples shall be at all times, except while being tested for butterfat, be maintained at a temperature above freezing and below 40 [degrees] F.

C. A colored preservative tablet, containing not less than 10 grains of bichloride of mercury or a preservative tablet containing not less than 1.5 grains of potassium dichromate or other approved preservative shall be used to preserve half pint composite samples of milk during the usual sampling and holding period in order to keep the samples in good condition for a test at the end of a sixteen-day sampling period and for a retest not more than twelve days later. Preserved composite samples of milk or cream or open equipment used for milk or cream.

D. After the addition of the first sample the composite sample bottles shall be closed tightly to keep out moisture and to prevent evaporation from the sample.

E. After each daily portion is added to the composite sample bottle, the contents of the bottles shall be rotated gently to mix the newly added portion of milk or cream completely with the preservative. Special care at this point will make the results more accurate and dependable. Do not shake the contents vigorously to cause churning nor against the stopper where the cream would harden and make proper preparation of the sample for testing more difficult. Care must be taken to add the daily portion to the correct composite sample bottle.

F. Composite sample bottles of milk and cream must be kept in a vertical position is the sample cabinet during the sampling and holding periods in order to prevent spillage and to avoid drying of the contents on the insides of the bottles which makes it more difficult to obtain a uniform moisture for an accurate butterfat test.

G. Preserved composite samples are poisonous and shall be locked except when licesed operator is in attendance. The bottle of (preservative) tablets shall be kept corked tightly to prevent spoilage, also shall be kept in a locked cabinet to prevent misuse.

H. Daily samples of milk taken on collection routes for addition to composite samples shall be taken into clean dry bottles that are numbered properly and shall be combined into the composite samples immediately on the return of the pickup truck to the plant.

I. Permission shall be obtained from the Commissioner of Agriculture or his agent to transfer samples for test to a central laboratory. When transferred, the entire sample and not a split sample must be transferred and due care taken to prevent churning and to maintain the temperature specified in (B) above.

J. Composite samples must be tested within three days after the close of the usual sampling period.

K. Composite samples must not be tested or handled by anyone except licensed plant personnel, state inspectors or other persons to whom specific permission has been granted by the Commissioner of Agriculture or his agent.

L. Composite samples of milk properly preserved, refrigerated above freezing and below 55 [degrees] F., and numbered for identification must be kept in good condition for retesting in all dairy plants for a period of at least twelve days after the close of the sampling period in order to allow patrons the privilege of having retests made and to allow creamery inspectors to verify the testing done by licensed operator.

M. All tests of milk made for comparative or verification purposes, or tests used to compare with those made by licensed operators, must be made by licensed operators in accordance with these regulations.

N. After composite samples have been held the required twelve days after testing and then emptied, the sample bottles shall be washed thoroughly and then dried before being used again. To prevent mold in the composite samples or on the stoppers, soak them about twelve hours in a ten percent solution of formaldehyde.

Section 5 Approved Methods of Testing Milk

Babcock Method

A. Apparatus and Materials Required

1. Standard Babcock milk test bottles, 8% 6 inch, having a capacity of 45 ml. up to the base of the neck, with graduations from 0 to 8.0% into whole percent, 0.5% and 0.1% respectively.

2. Pipette graduated to contain 17.6 ml. to the bottom of the meniscus.

3. C entrifuge, or tester, shall stand on a solid foundation to prevent vibration, shall preferably have a built-in speed indicator or be so constructed that the speed of the centrifuge may be ascertained without disassembling any part of the machine. D uring use the centrifuge must be heated to at least 135 [degrees] F. and not over 140 [degrees] F., which temperature shall be controlled thermostatically.

4. Acid burette or measure graduated to deliver 17.5 ml.

5. The use of a mechanical shaker is recommended where an appreciable number of samples are tested as it is a time saver and often is more accurate than hand shaking.

6. Thermometer.

7. Speed indicator preferably built in as in (3) above.

8. Dividers.

9. Tempering bath equipped with thermostat set to control temperature at a range of 135 [degrees] to 140 [degrees] F. and racks to hold the test bottles upright.

10. Sulphuric acid having a specific gravity of 1.82 to 1.83 at 68 [degrees] F. Sulphuric acid containers shall be kept corked tightly to prevent weakening of the acid.

11. Acid hydrometer for use at 68 [degrees] F.

12. Distilled water or rain water shall be provided to add to tests if mineral deposits in the water interfere with reading the tests.

B. Preparing Universal Fresh Samples for Testing

1. Samples shall be in good condition and tested within 3 days of the day taken. They shall be warmed to about 100 [degrees] F. and mixed thoroughly by pouring from one vessel to another at least four times.

C. Preparing Composite Samples for Testing

1. Loosen the stoppers of the composite sample bottles and place the bottles in warm water up to the necks to soften the butterfat and to facilitate complete mixing of the sample. To prevent over heating and oiling off of samples, the water bath should have an ample volume of water that is maintained at about 95 [degrees] F. by a thermostat set at that temperature. Dislodge any milk solids from the inside of the bottle with a spatula so a complete mixture of the contents of the bottle may be obtained.

2. Shake the bottles gently by a rotary motion several times during the course of preparation to mix in the softened cream layer and also to prevent the samples from "oiling off" in warm water. Never shake the samples vigorously as it is apt to churn the butterfat and thus make it more difficult to perform an accurate test.

3. Continue the preparation, as above, until the sample is uniform throughout. Mix the sample thoroughly by pouring from one bottle to another at least four times before pipetting the test charge.

D. Making the Test

1. Draw 17.6 ml. of milk, prepared as above, into the pipette with the bottom of the meniscus on the graduated line. Transfer this test charge at a temperature of about 95 [degrees] F. into the Babcock milk test bottle. The use of two pipettes is recommended to increase the speed of testing when large numbers of samples are tested. Blow out the last drop of milk that drains from each pipette into the test bottles or accomplish the same result by dripping the pipette against a grooved rubber air vent on the pipette stem.

2. Add 17.5 ml. of sulphuric acid slowly to the test bottle. In adding the acid, rinse down the milk adhering to the inside of the neck of the test bottle The acid and the milk should be tempered to 65 [degrees] to 70 [degrees] F. when the acid is added.

3. Mix the milk and acid together by a slow rotary motion until all of the solids-not-fat have been destroyed. The use of a mechanical shaker is recommended when large numbers of tests are made. Allow the bottles to stand several minutes to get complete action of the acid before placing them in the centrifuge.

4. Place the bottles in the centrifuge and balance the machine by distributing bottles opposite each other. The temperature in the centrifuge must be controlled by thermostat at a range of not less than 135 [degrees] F. and not more than 140 [degrees] F. While at the proper speed for five minutes. The proper speed to operate the centrifuge will vary according to the diameter between the bases of opposite test bottle cups when they are in a horizontal whirling position. The following table gives the number of revolutions per minute at which machines of different diameters must be operated.

Diameter of Machine(Inches)	Number of Revolutions (Per Minute)
10	1074
12	980
14	909
16	848
18	800
20	759
22	724
24	693

5. Fill the test bottles up to the bases of the necks with hot water at a temperature of 140 [degrees] F. Avoid the use of hard water as it may cause foam in the test bottles. If necessary to use it, add a small amount of sulphuric acid to the water before use.

6. Mix the contents of bottles after the addition of water and whirl in centrifuge for two minutes.

7. Fill the test bottles to about an inch from the top with hot water at 140 [degrees] to 145 [degrees] F. and whirl for one minute. If the fat on the surface of the test bottle is not clear amber color, it is advisable to mix the contents of the bottle by a slow rotary motion before filling the test bottle to about an inch from the top with hot water at 140 [degrees] to 145 [degrees] F.

8. Remove the tests from the centrifuge and temper them in a bath of hot water for five minutes. The water in the bath must be maintained at 135 [degrees] to 140 [degrees] F. by thermostatic control, and extend to the full height of the butterfat column in the test bottles. The temperature of the water must be maintained as above until all tests have been read.

9. When reading butterfat tests, the record of the previous tests must not be available for comparison by the certified test operator until after all tests have been completed.

10. Measure the length of the butterfat column of the whole milk test (Fig.1.) with calipers from the upper point of the meniscus at the top of the column (A) to the bottom of the column at its lowest point (B).

To read the percentage of butterfat be sure to maintain the above caliper measurement (A to B), then transfer the lower point of the calipers to the zero graduation (Fig.2.) and read the percentage of butterfat at the top of the calipers.

The use of calipers, or some approved reading device, is required because it reduces the chances of errors and facilitates the work. In reading the tests do not remove a second bottle from the tempering bath until the first has been read and recorded.

Replace the test bottles in the hot water bath so that the water level is maintained to the full height of the butterfat columns until all tests have been read.

11. As soon as all of the butterfat tests for the period have been completed and the results recorded, compare these tests with the previous period.

12. When a composite milk sample varies in butterfat test three-tenths of one percent or more from the composite test of the same producer from the previous period, a retest shall be made to check the accuracy of the first test and the results of both tests recorded. Variations in butterfat test of three-tenths of one percent or more from the previous period shall be reported at once to producers whose tests vary.

Retest must be made if the finished test contains charred or foreign substances, curdy particles, or is not perfect test.A perfect test for butterfat appears as follows:

(a) Bright yellow straw color fat column.

(b) Extremities of fat column sharply defined.

(c) Fat column free from foreign substances as curd or char.

(d) Liquid beneath fat column clear.

(e) Fat column within graduated scale on test bottle.

Milk-O-Tester Method

A. Reference Methods

1. The Babcock and/or Gerber methods or other means approved by the Commissioner for determining the fat content of milk shall be used as the reference method to maintain the calibration of the Milk-O-Tester instrument as described in these regulations.

2. Written notification of the reference method to be used shall be sent to the Commissioner prior to the installation and first use of a Milk-O-Tester. A subsequent change in the reference method used shall be made only with the specific approval of the Commissioner.

B. Laboratory Facilities and Reagents

1. The following supplies and facilities shall be available and instruments shall be in good working order:

(I) Complete set of approved equipment and reagents for testing control milks by the reference method to be used.

(II) A turbidemetric instrument with automatic diluent dispenser intended for testing milk for fat content, accessories, and instruction manual appropriate for the machine in use.

(1) Any automatic diluent dispensing devise added to a manual instrument shall be done in a manner so as to be activated by either manual means or by changing the position of the collection funnel (7) and so that the tubing connecting the dispenser to the separation check value (17) does not change dimensions during operation of the dispenser.

(2) The addition of an automatic dispensing device or any other modification to the instrument shall not change any of the provisions of these regulations, especially those dealing with control and calibration of the instrument.

(III) Thermostatically controlled water bath with recording thermometer, with proper temperature distribution, set to maintain sample temperature at 95 [degrees] to 100 [degrees] F.

(IV) Power supply. Single phase, 115V or 220V, 50 or 60 cycles, within +/- 10% fluctuation, with indicating voltmeter convenient to operator.

(V) Means of measuring pH.

(VI) A strainer of 80 - 100 mesh screen to clarify and mix samples when manual model is in use.

(VII) Supply of distilled or deionized water for flushing and preparation of diluent.

(VIII) Refrigeration at 33 [degrees] - 40 [degrees] F. for milk sample storage.

(IX) A laboratory with adequate lighting facilities, adequate counter surface to accommodate all essential equipment and free from disturbing drafts, dust, noise and vibrations.

(X) Hot and cold water, wash sinks, and cleansing agents to clean equipment.

(XI) Adequate waste and sewage system to dispose of all milk, acid and wash water.

(XII) Preservative. If used, 1 grain potassium dichromate for each 100 ml. of milk or other formulations approved by the Commissioner.

2. The diluent for the manual Milk-O-Tester shall consist of the following reagents:

(I) Manual model with automatic diluent dispenser.

1. 10.0 liters of distilled or deionized water 45.0 grams of sisodium ethylenediaminotetraacetate n1 (EDTA) n1 Dow Chemical Co.7.6 grams of reagent grade sodium hydroxide (NaOH)10.0 milliliters Tween 20 n2 (polyoxyethylene (20) sorbitan monolaurate) n2 Atlas Chemical Ind., Inc.

2. If the diluent is to be assembled from the reagents by the user, the following procedure shall be followed: Wash the EDTA into the container with one liter of the distilled water. Dissolve the NaOH in one liter of distilled water and add. Next add seven liters of distilled water. Finally add the 10.0 milliliters of "Tween 20" and rinse the funnel with the final liter of distilled water. Mix well and let stand several hours for air bubbles to disappear. The pH of the final mixture shall be between 9.5 and 10.1.

3. If the diluent mixture or a concentrated or dried form is purchased from a supplier, the supplier's instructions for making an equivalent solution shall be followed.

(II) For semi-automatic and automatic Milk-O-Testers:

45 grams of disodium ethylenediaminotetracetate n3 (EDTA)

n3 Dow Chemical Co. or J. T. Baker Chem. Co. 7.6 grams of reagent grade sodium hydroxide (NaOH)

1 ml. Triton X-100 n4

n4 Rohm & Haas 5 Dow-Corning Corp.

1 ml. Antifoam A emulsion n5

n5 Dow-Corning Corp.

Sufficient distilled or deionized water to dilute above reagents to 10 liters. The general procedures of this section, B.2.(a)(ii) shall be followed.

(III) Or other approved equivalent for subparagraphs (I) and (II) above listed as may be recognized by the Commissioner.

Routine Inspection and Control Prior to Daily Use

A. Preparation of Control Samples

1. At least four control samples of unstandardized natural milk of sufficient quantity, shall be available to allow for the performance and accuracy checks required by (C) of this section and (D) of the following section, Routine Testing by Milk-O-Tester Method, for a 24 hour period.

(I) At least one control milk shall be a pooled sample of unhomogenized milk from a minimum of three herds and/or. 100 cows testing between 3 and 4% fat and at least one control milk shall test between 5 and 6% milk fat.

(II) Each control sample shall be tempered to 95-100 [degrees] F., an approved preservative added at the required rate if control sample is to be used more than 24 hours after preparation, and mixed thoroughly. Churning shall be avoided. Subdivided each sample into subsamples of adequate size. Keep the control sample thoroughly mixed, but avoid churning during subsampling.

(III) A subsample of each control milk shall be tested in triplicate by the reference method for fat content. Individual determinations shall be read to at least the nearest 0.05% fat. The individual results and the average for each control milk shall be recorded as provided in the Section-Required Forms-DMC Milk Form # 3.

(IV) The remaining control subsamples shall continue to be stored at 33-40 [degrees] F. until used. No subsample more than 10 days old shall be used.

(V) Prior to the expiration date or use of the last subsample of control milk, whichever comes first, preparation of a new set of control samples shall be completed.

2. Alternatively, standard mixtures approved by the Commissioner may be used in lieu of the control milks. Such mixtures shall be stored, tempered, and tested in the manner prescribed by the Commissioner.

B. Instrument inspection prior to daily use of Milk-O-Tester where applicable (the numbers in parenthesis refer to the diagram presented on page 26).

1. With all electrical power disconnected from the instrument, the meter (14) shall read exactly 9.2.

2. With the power on, the meter shall read zero with diluent only in the cuvette(9).

3. The diluent check value (15) in the diluent system between the syringe and the diluent supply bottle shall be inspected, thus: Remove the tube from the supply bottle, invert and cycle the automatic syringe. If the film of diluent on the screen increases in quantity, the value shall be replaced and the inspection repeated until the value is found satisfactory.

4. There shall be no air bubble in the diluent syringe (2) or the tubing connecting this syringe to the separation check value (17).

5. Place cooled, freshly boiled distilled or deionized water on the sample intake (3) and press the start button. Collect the discharged water until the collection funnel (7) is approximately one-half full. If the water has a milky appearance, air is being drawn into the system. This leak must be eliminated before proceeding.

6. The separation valve (17) shall be inspected by cycling milk at least three times without collection. If milk leaks back into the diluent line, the valve shall be replaced and the inspection repeated until the valve is found satisfactory.

7. The water bath (18) shall be maintained at 140 [degrees] F. +/- 1 [degrees] F. and at the proper level. The hot water shall circulate freely through the homogenizer heating coil (16).

8. All moving parts and hose connections shall be inspected for leaks and proper operation. The supply of diluent shall be checked for adequacy.

C. Daily Performance Check

1. Accuracy check. each day before routine testing begins, at least one subsample of control milk shall be tested in triplicate. Read the test to 0.01%. Disregard the first reading. If the difference between the average of the second and third reading and the average of the three reference method result is 0.1% fat or less, proceed to C.2. below. If the difference is more that 0.1% test 3 more samples of new control milk. If the average difference of the additional samples exceed 0.1%, discontinue operation of the machine, determine the reason and correct before resuming operation.

2. Repeatability check. Each day before routine testing begins 10 consecutive readings on a single well mixed bulk sample of milk shall be made and recorded as a permanent record. The standard deviation of the results shall be less than +/- 0.03% fat. This standard deviation, defined below may be assumed to be below the maximum if the range of the ten readings is .07 or less. If the standard deviation is exceeded, discontinue operation of the machine until the cause is determined and corrected. The standard deviation of results shall be calculated by the mathematical equivalent of the following formula:

[See formula in printed version]

Routine Testing By Milk-O-Tester Method

A. Preparation for Testing

1. Samples shall be tempered to 95-100 [degrees] F. in the thermostatically controlled water bath prior to testing.

2. Samples held over 24 hours shall be prepared in accordance with Section No. 5, C.

3. The well-mixed sample shall be poured through an 80-100 mesh screen immediately prior to testing when using a manual machine.

B. Testing

1. Manual "Milk-O-Tester" with automatic diluent dispenser.

I. The well-mixed sample shall be placed on the milk intake tube (3) and the start button pressed immediately after mixing. Air entrance into the milk intake tube shall be avoided.

II. The operator shall wait at least three seconds after the homogenizer (5) stops before depressing the collection funnel plunger (8) and activating the diluent syringe (2).

III. The operator shall wait for the diluent syringe (2) to return to its rest position under its own power before releasing the collection funnel (8). The operator shall not assist the return of the syringe in any way.

IV. The meter (14) shall be read to the nearest 0.1% fat immediately after the indicating needle stabilizes, or within 20 seconds, and the results recorded.

V. With any sample that is more than 2.0% fat difference from the preceding sample, disregard the first test result and the sample shall be rerun and the rerun result recorded.

VI. If no sample is to be run within five minutes, distilled water or diluent shall be cycled through the homogenizer and cuvette twice to clean. The first reading on the next sample shall be invalid and that sample shall be rerun.

VII. The instrument cover or siutable replacement shall be in place during operation of the machine.

2. Semi-automatic and automatic models of "Milk-O-Tester."

I. Applicable operational procedures approved by the Commissioner shall be followed, otherwise provisions of Bl of this section shall apply.

3. All samples shall be held unless exempted by the Commissioner until the next hourly or more frequent accuracy check described in D of this section is completed. If this check fails, all samples shall be retested by a duly licensed tester using either an alternative procedure approved by the Commissioner, or held for retesting on the "Milk-O-Tester" after proper repairs and/or adjustments are completed and the machine shown to be in calibration. If sample holding exemption has been granted and the accuracy check fails, immediate rescheduling shall be made of all samples tested subsequent to last correct accuracy check.

4. The identity of each sample shall be preserved explicitly during the holding period described in B3 above.

5. Samples which are frozen or partially frozen, lumpy, curdled or churned, containing excess amounts of preservatives, or samples that contain flavoring materials such as chocolate, or any milk that has been homogenized previously shall not be tested by the "Milk-O-Tester" method.

6. The Commissioner may request, and licensees shall conduct turbidimetric milk fat determinations on samples supplied by him for the purpose of determining the accuracy of testing and/or send to a location specified by the Commissioner the remaining portion of certain samples for retesting.

C. Zero Adjustment

1. The meter (14) shall be adjusted to zero on the manual model and to .02 on semi-automatic and automatic models with pure diluent in the flow thru cuvette (9).

I. This adjustment shall be made before each day's run, before the performance check described in Section C, above, and before testing samples for calibration purposes as described in C. of the following section, Instrument Calibration. If out of zero adjustment, make the accuracy check as provided in D of this section, then adjust to zero and rerun the accuracy test.

II. This zero check shall also be made before the accuracy check described in D of this section and after testing of approximately each fifty samples.

III. The first reading after this zero check shall be invalid and shall be ignored. Such a sample shall be retested.

2. Alternative zeroing procedures approved by the Commissioner may be used after testing of each fifty samples.

D. Accuracy Check

A control sample prepared in A of the previous section, Routine inspection and control prior to daily use, shall be checked each hour or more frequently of machine operation. If the reading is 0.1% fat or less different from the value obtained by the reference method, the machine may continue to be used. If the reading is greater than 0.1% different, follow the procedure given in C of the previous section. At all times, the last 20 control sample tests must meet the criteria of A.2. of the following section with respect to the average difference and standard deviation of difference from the reference method.

E. Cleaning

1. The machine shall be flushed twice with distilled water or diluent if it is to be idle for five minutes or more.

2. The machine shall be thoroughly cleaned at the end of the day's testing by alternately circulating distilled water and an appropriate cleaning solution through the entire system. The final rinse shall be with distilled water or with the diluent.

3. Formation of milkstone in any part of the machine shall not be allowed to occur.

4. Milk and oil splatters shall be wiped from all accessible surfaces on both the exterior and interior of the machine at least daily, and the machine other wise shall be kept clean.

5. The collection funnel (7), pipette (6), and wiper blade shall be kept clean at all times during operation.

6. The machine shall be lubricated and adjusted as required to keep it in good working order.

Instrument Calibration

A. Definitions

1. Calibration shall mean to adjust the settings on the instrument so that the readings will match results obtained by the Babcock, Gerber or other reference method approved by the Commissioner.

2. A machine shall be considered to be properly calibrated when the average difference between the machine results and the reference method results, called D, and the standard deviation of difference between methods, called S[D], are less than the values shown in Table 1. At least 20 samples shall be tested.

TABLE 1

Maximum allowable average difference (D) and the standard deviation of difference (S[D]) between the Milk-O-Tester and the reference method.

Machine Calibrated For Use On
Reference Method Individual Cow Samples Herd or Pooled Samples
	D	S[D]	D	S[D]
Gerber	+/-0.04	+/-0.08	+/ -0.04	+/-0.06
Babcock	+/-0.04	+/-0.10	+/-0.04	+/-0.06

B. Conditions Requiring Calibration

1. The instrument shall be calibrated when initially installed.

2. The instrument shall be calibrated when the performance check, Section C of Routine Inspection and Control Prior to Daily Use, or the accuracy Section D of Routine Testing by Milk-O-Tester Method, fail.

3. The instrument shall be calibrated when any of the following parts are replaced, rebuilt, or adjusted; syringe (2), check valve (15), separation valve assembly (17), pipette (6), cuvette (9), photocell (10), lamp (11), or homogenizer (5).

4. The homogenizer (5) shall be rebuilt, including the replacement of the homogenizing valves, and the instrument subsequently shall be recalibrated after a maximum of 20,000 samples for manual Milk-O-Tester, including control and calibration samples have been tested.

C. Types of and Preparation of Calibration Samples

One of the following types of samples shall be used for calibration:

1. At least ten samples of individual cow milks testing between 3 and 4% milk fat and at least ten samples of individual cow milks testing between 5 and 6% milk fat, or

2. At least ten pooled or herd milk samples testing between 3 and 4% milk fat and at least ten pooled or herd milk samples testing between 5 and 6% milk fat, except that not more than five of the ten 5 to 6% milk fat samples may be prepared by co-mingling varying amounts of "low" and "high" test milks. A herd milk sample is defined as one representing a minimum of 35 cows milking and pooled sample as one representing a minimum of three herds' milkings.

A variety of fat levels within the required ranges shall be used.

3. The calibration samples shall be tempered and mixed as required in A of the section, Routine Testing by Milk-O-Tester Method.

D. Testing Calibration Samples

1. The "Milk-O-Tester" shall be operated in accordance with B of the previous section with the following additions: At least three readings shall be made, recorded and averaged to the nearest 0.01% fat.

2. The well mixed sample for the reference method shall be followed with the following additions: At least three tests shall be made on each sample. All readings shall be made to at least the nearest 0.05% fat. The three results shall be averaged and this average shall be regarded as the true fat content of the sample.

E. Calculation of Calibration Results

1. The average of the results obtained on the law testing samples (3-4%) by the "Milk-O-Tester" method shall be compared to average of the results obtained on the same samples by the reference method. If the difference is 0.01% fat or less, the calibration may be continued. If the difference is greater than 0.01% fat, the machine shall be adjusted and the samples retested on the adjusted "Milk-O-Tester" until the differece is less than 0.01% fat.

2. The average of the results obtained on the high testing samples (5-6%) by the "Milk-O-Tester" method shall be compared to the average of the results obtained on the same samples by the reference method. If the difference is 0.05% fat or less, the calibration procedure may be continued. If the difference is greater than 0.05% fat, the machine shall be adjusted and the samples retested on the "Milk-O-Tester" until the difference is less than 0.05% fat.

3. The criteria listed in E.1 and 2. of this section shall be met simultaneously.

4. The average difference between methods, D, shall be calculated as the differece between the average of the "Milk-O-Tester" method on all calibration samples and the average of the reference method on all calibration samples. D shall be considered as the mathematical equivalent of the following formula:

[See formula in printed version]

5. The standard deviation of difference, S[D] of all calibration samples shall be calculated by a mathematical equivalent of the following formula:

[See formula in printed version]

For those unfamiliar with the calculations required in this and preceding paragraph, the work sheet DMC Milko Form # 1 may be used to get equivalent results. A sample calculation is shown in Tables 2-4.

6. All calibration samples tested on the "Milk-O-Tester" shall be used in the calculations described in E.4. and 5%. of this section, even though the minumum of twenty samples may be exceeded.

7. The average difference, D, and the standard deviation of difference S[D], shall not exceed the values shown in Table 1, A. 2. of this section.

8. The criteria listed in paragraphs 3 and 7 of this section shall be met simultaneously. If not, the machine shall be considered to be uncalibrated. After appropriate adjustments, such as changing the amount of diluent delivered or reseting of electrical systems, have been made, all calibration samples shall be tested on the machine and new calculations made according to these provisions.

STATE OF VERMONT - OFFICE OF THE SECRETARY OF STATE

RULES REFERENCE MATERIALS

AGENCY: Agriculture

REQUIRED RECORDS

A. A record of all butterfat tests shall be maintained.

B. Additionally, the following records for each machine shall be made and kept on file for a period of three months at the place where "Mile-O-Tester" testing is used. These records shall be made available at all times to the Commissioner or his representative:

1. Work sheet for determining standard deviation (DMC Milko Form # 1)

2. Milk-O-Tester check list (DMC Milko Form # 2)

3. Milk-O-Tester daily performance checks (DMC Milko Form # 3)

4. Calibration and shift value check (DMC Milko Form # 4)

5. Sample record (DMC Milko Form # 5)

6. Temperature chart of water bath

7. Any other records requested by the Commissioner

REQUIRED FORMS

A. All records listed under B of this section shall be kept on forms prescribed by the Commissioner as herein follow and listed as DMC Milko Form # 1 through DMC Milko Form # 5.

TABLE 2

Sample Work Sheet for Determining Standard Deviation
COLUMN NO.
	Step 1		Step 2		Step 3
1	2	3	4		5
	Average	Average	Difference (D)		Difference
Sample	Duplicate	Triplicate	Milko-		Square d
No.	Milko-	Babcock	Babcock		(D<2>)
			4a	4b
1	3.53	3.55		-.02	.0004
2	3.61	3.60	.01		.0001
3	3.69	3.65	.04		.0016
4	3.40	3.30	.10		.0100
5	3.47	3.45	.02		.0004
6	3.85	3.80	.05		.0025
7	3.62	3.60	.02		.0004
8	3.71	3.75		-.04	.0016
9	3.91	3.85	.06		.0036
10	3.61	3.60	.02		.0004
11	6.12	6.15		-.03	.0009
12	6.39	6.40		-.01	.0001
13	6.75	6.80		-.05	.0025
14	6.39	6.35	.04		.0016
15	6.77	6.70	.07		.0049
16	6.42	6.45		-.03	.0009
17	6.71	6.75		-.04	.0016
18	6.68	6.70		-.02	.0004
19	6.71	6.70	.01		.0001
20	6.43	6.45		-.02	.0004
		Sub Total	4b	4b
			.44	-.26
Step 4 n1 - sum D (4a - 4b) = 0.18
Step 5 - sum D<2>					.0344
Step 6 - D = sum D = .18 =					.009
N 20
Step 7 - D X sum D = .009 X .18 =					.00162
Step 8 - sum D<2> - (D X sum D) = .0344 - .00162 =					.03278
Step 9 - sum D<2> - (D X sum D) = .03278 = S[D]<2> =					.0017
5(N-1) 19
Step 10 - Find S[D] from S[D]<2> in table 3.

n1 If step 4 is negative, it does not affect results.

The data in Table 3 will enable you to arrive at a sufficiently accurate estimate of S[D].

TABLE 3

If S[D]<2> is:	Then S[D] is:
.0001	.01
.0004	.02
.0009	.03
.0016	.04
.0025	.05
.0036	.06
.0049	.07
.0064	.08
.0081	.09
.0100	.10

S ince the example cited above SD<2> was 0.0017 the S[D] would fall between 0.04 and 0.05. It would suffice to estimate it as 0.04. If the value for S[D2] exceeds .0036 on blended milk or .01 on individual cows milk, the instrument obviously needs to be recalibrated.

The Milko-Tester will be considered to be properly calibrated when the average difference (D) and the standard deviation of difference (S[D]) so calculated are equal to or smaller than the values shown in table 4.

TABLE 4

Maximum allowable average difference (D) and standard deviation of
difference (S[D] between the Milk-O-Tester and the reference method.
Machine calibrated for use on
Reference method Individual cow samples Herd or other blended samples
	D	S[D]	D	S[D]
	%	%	%	%
Gerber	+/-0.0 4	+/-0.08	+/-0.04	+/-0.06
Babcock	+/-0.04	+/-0.10	+/-0.04	+/-0.06

Since the average difference (D) in the example is 0.0009 and the standard deviation (S[D]) is 0.04, the machine is in proper calibration because these values are less than the values shown in table 4 for the Babcock method for individual cow samples.

Should either the mean difference or the standard deviation of difference determined as outlined exceed the values shown in the table, the Milko-Tester must be adjusted in accordance with the manufacturer's instructions and the calibration procedure repeated by retesting the same samples with the Milko-Tester.

Listing of blank form to be used:

Work Sheet for Determinining Standard Deviation - DMC Milko Form # 1

Weekly Milk Test; Clean Up; and Homogenizer Count Form

Milko-Tester Daily Performance Checks/Form - FMMA 6/71

Calibration and Shift Value Check - DMC Milko Form # 4

Sample Record - DMC Milko Form # 5

Diagrams:

Diagram of "Milko-Tester", Mannual Model (2 Pages)

Key to Diagram Preceeding

Section 6 Approved Methods of Testing Cream

A. Apparatus Required

1. Standard Babcock cream test bottles, 50% 9 gram either 6 inch or 9 inch, or the 50% 18 gram 9 inch bottles shall be used. Bottles must be marked "9g" or "18g" as the case may be. The body of the bottles shall contain not less than 45 ml. Graduations shall represent 5.0% and 0.5% and each 5.0% graduation from 0 to 50 shall be numbered.

2. Pipettes

3. Cream test scales sensitive and accurate to one grain (0.065 gram) when loaded to capacity.

4. Weights marked "9g" or "18g", as the case may be.

5. Acid measure or burette graduated to deliver 17.5 ml.

6. Centrifuge.

7. Speed indicator.

8. Thermometer.

9. Tempering bath containing racks to hold bottles upright and with thermostat at 135 [degrees] to 140 [degrees] F.

10. Sulphuric acid, specific gravity 1.82 to 1.83 at 68 [degrees] F.

11. Acid hydrometer for use at 68 [degrees] F.

12. Mechanical shaker.

13. Dividers.

14. Distilled Water.

15. Glymol (red reader or meniscus remover).

B. Preparing Individual, or Daily, Samples for Testing

1. Cream samples for the daily test shall be tested the same day as taken and shall not be held over night for testing the next day. They shall be warmed to about 70 [degrees] F. and mixed thoroughly by pouring from one vessel to another at least four times. All the cream must be well mixed in and the sample uniform throughout when the test charge is weighed. Daily testing of cream samples is recommended.

C. Preparing Composite Samples for Testing

1. Loosen the stoppers and place the bottles in warm water at about 95 [degrees] F. to soften the cream layer and to facilitate complete mixing of the sample. Use a spatula to remove any cream from the inside of the sample jar.

2. Shake the bottle gently by a rotary motion several times during the course of preparation to mix in the softened cream layer and also to prevent the samples from "oiling off" in warm water. Never shake the samples vigorously as it is apt to churn the butterfat and thus make it more difficult to perform an accurate test.

3. Continue the preparation as above until the sample is uniform throughout. Mix the sample throughly by pouring from one bottle to another at least four times just before weighing the test charge.

D. Making the Test

1. Cream test scales must stand level and on a solid foundation.

2. Mark the cream test bottles to correspond to the samples being tested, place them on the scales and balance the scales.

3. Weigh 9 grams of well mixed cream into the 9 gram test bottle or 18 grams into the 18 gram test bottle.

4. Cool the test charge to about 65 [degrees] to 70 [degrees] F.

5. Add 9 ml. of 70 [degrees] F. water to the 9 gram cream sample but no water is added to the 18 gram sample. Mix the water with the cream before adding the acid.

6. Add 17.5 ml. of sulphuric acid. The same amount of acid is used for either the 9 gram or 18 gram samples. The temperature of the acid should be about 65 [degrees] to 70 [degrees] F. the same as the cream sample when the acid is added.

7. Mix the cream and acid immediately by a slow rotary motion of the test bottle until a uniform chocolate brown color results. Allow the bottles to stand several minutes to get complete action of the acid before placing them in the centrifuge.

8. Place the bottles in the centrifuge and balance the machine by distributing bottles opposite each other. The temperature in the centrifuge must be controlled by, thermostat at a range of not less than 135 [degrees] F. and not more than 140 [degrees] F.

9. Whirl at the proper speed for five minutes. The proper speed to operate the centrifuge will vary according to the diameter between the bases of opposite test bottle cups when they are in a horizontal whirling position. The table on page 7 gives the number of revolutions per minute at which machines of different diameters must be operated.

10. Add hot water at a temperature of 140 [degrees] to 145 [degrees] F. up to the bases of the necks of test bottles.

11. Mix the added water with the contents of the bottles by a slow rotary motion and whirl for two minutes.

12. Add hot water at a temperature of 140 [degrees] to 145 [degrees] F. to about an inch from the top of bottle to bring the butterfat column within the graduated scale on neck of bottle. If the fat on the surface of the test bottle is not a clear amber color, it is advisable to mix the contents of the bottle by a slow rotary motion before filling the test bottle to about an inch from the top with hot water at 140 to 145 [degrees] F.

13. Whirl for one minute.

14. Remove the tests from the centrifuge and temper them in a bath of hot water for five minutes. The water in the bath must be maintained at 135 [degrees] to 140 [degrees] F. by thermostatic control, and extend to the full height of the butterfat column in the test bottles. The temperature of the water must be maintained, as above, until all tests have been read.

15. Add about four drops of red reader, called glymol or meniscus remover, slowly be allowing it to flow down the inside of test bottle neck to cover the surface of the butterfat column before reading the test. The specific gravity of the red reader must not exceed 0.85 at 68 [degrees] F. so as not to mix with the butterfat column.

16. When reading butterfat tests of cream, the record of the previous test must not be available for comparision by the certified test operator until after all tests have been completed.

17. Measure the length of the butterfat column of the cream test with calipers from the upper part of the column at the junction of the red reader and the butterfat column to the bottom of the column at its lowest point. To read the percentage of butterfat be sure to maintain the above caliper measurement, then transfer the lowest point of the calipers to the zero graduation and read the percentage of butterfat at the top of the calipers. The use of calipers, or some approved reading device, is required because it reduces the chances of errors and facilitate the work.

Replace the test bottles in the hot water bath so that the water level is maintained to the full height of the butterfat columns until all tests have been read.

18. In reading the tests do not remove a second bottle from the tempering bath until the first has been read and recorded.

19. When a composite cream sample varies in butterfat test three percent or more from the composite test of the same producer's cream for the previous period, a retest shall be made to check the accuracy of the first test and the results of both tests recorded. Variations in butterfat test of three percent or more from the previous period shall be reported at once to producers whose tests vary.

20. A retest must also be made if, in the finished test, the fat column has mixed with the meniscus remover, contains charred or foreign substances, curdy particles, or is not a perfect test. (See page 8 for description of a perfect test. (D. Making the test, 12, (a)-(e)) Butterfat tests of cream may vary from one period to another due to one or more of the following reasons:

1. Speed of separator.

2. Rate of inflow of milk separated.

3. Temperature of milk separated.

4. Butterfat test of milk separated.

5. Amount and character of flushing of separator.

6. Position of cream screw.

7. Balance of bowl.

8. Cleanliness and conditions of bowl.

21. If a state inspector finds that any butterfat tests of cream have been made erroneously by a certified operator, the state inspector shall notify in writing the manager of the plant where such tests are in error of the correct tests and such manager shall cause payments to be made to all patrons on the basis of the correct tests.

22. Daily samples of cream numbered properly for identification must be held in good condition for retest at least until the close of the day's work on the day after the samples were tested.

Section 7 Care of Glassware and Testing Apparatus

A. All test bottles and pipettes must be cleaned in water containing a good cleaning compound as soon as the tests have been completed. Each piece of glassware must be washed thoroughly and inverted to drain and dry. Unclean test bottles shall not be used as a residue of butterfat may cause an erroneous test or interfere with reading the tests. All test bottles, pipettes and other testing apparatus should be kept in racks in a closed cupboard to protect them from dust and breakage.

THE STANDARD PLATE COUNT

The Standard plate method of bacterial analysis of milk is an approved test by the Commissioner of Agriculture to determine the quality of milk with reference to payment for it when received or purchased. V.S.A., Title 6, Section 2701.

Except as provided herein, the methods of sampling and testing and computing the results of the test, shall be those approved and published in the latest edition of "Standard Methods of Milk Analysis" of the American Public Health Association, 1790 Broadway, New York 19, N.Y.

All owners and operators of licensed dairy plants who purchase milk on the basis of its quality as determined by the plate count method of bacterial analysis and all certified operators of the plate count method are hereby required to comply with these regulations.

Section 1 General Requirements and Regulations

(a) Applicants for certificate to operate the plate count method for the determination of the bacterial content of milk must apply on a blank furnished by the Commissioner of Agriculture and arrangements will be made for an examination.

(b) In order for persons to qualify for a certificate, they must first demonstrate their ability to operate the test satisfactorily and also their knowledge of the fundamentals of the test by answering in writing fifteen questions furnished by the Commissioner of Agriculture or his deputy. Such fifteen questions will be chosen from the list published herein.

(c) Each certified operator shall sign his certificate in ink and post it in the plant where he works.

(d) An assistant or second operator shall be certifed in each plant to do plate count work in case the regular operator is absent.

(e) Premium schedules and grade requirements shall be approved by the Commissioner of Agriculture before being used as a basis of paying premiums. Changes in premiums or grade requirements shall slao be approved by the Commissioner of Agriculture before being used as a basis of payments.

Section 2 Sampling

(a) Containers of milk at the time of delivery by the producer or his agent must be identified properly either by name or number, preferably the latter.

(b) A representative sample of milk, consisting of not less than 10 ml. must be taken from the entire delivery. Sampling only nights or mornings milk, or one can from several delivered is prohibited when the payment covers the entire delivery. The recommended procedure is to take a representative sample from the weigh can after all of the delivery has passed through a perforated metal strainer. It shall be optional, however, to take a sample from the composite of all the single cans before pouring into the weigh can provided each can is stirred thoroughly before sampling. The agitator and sampling dipper used for this purpose shall be rinsed in clean water and scalded and kept between samplings in a can of hot water with steam continually bubbling through it.

(c) Samples shall not be taken for plate count analysis from the same weigh can compartment through which an inferior or lower grade of milk passes unless the compartment is first washed thoroughly and sterilized.

(d) A schedule of sampling days for each calendar month shall be forwarded to the office of the Commissioner of Agriculture within four days before the end of each preceding month. The bacteriologist in charge shall treat the schedule of dates absolutely confidential in order that producers may not prepare in advance for sampling dates.

(e) Schedules of sampling days shall vary each succeeding week.

(f) Schedule dates for sampling shall be followed unless specific permission for changes is granted.

(g) Samples shall be cooled to and maintained at or below 40 [degrees] F. until they are tested.

(h) Samples shall be tested in the plant where taken and tests shall be made the same day as the samples are taken unless permission is granted to transfer them to some central laboratory to be tested. Extra care shall be taken when samples are transported to keep all bottles corked tightly and iced properly.

(i) At least two samples shall be taken during each half month period of payment or at such other intervals as the Commissioner shall require.

(j) All samples shall be numbered correctly to identify each producer's milk.

(k) The weigh can shall drain completely, so that residual milk does not mix with the next lot that is weighed and sampled.

(l) A list of patron numbers should be kept indicating the order of their deliveries on the days of sampling.

Section 3 Making the Test

The latest edition of Standard Methods of Milk Analysis shall be followed except:

(a) A single petri plate may be poured in the test of each sample.

(b) All petri plates, including water and media blanks, numbered properly for identification, shall be held in good condition for recounting one full day after the day on which the count is made.

(c) Counts shall be used exactly as obtained and no tolerance shall be allowed for weigh can contamination. All counts made shall be used in determining the correct average on which payment is based.

Section 4 Records and Payments

(a) A producer shall be notified promptly by telephone or a notice attached to a return empty can in case any test of his milk is below the grade which commands a premium.

(b) The statements to producers, who are paid premiums based partially or wholly on bacteria counts, shall show the premium rate and the average bacteria count or the individual counts for the period covered by the payment.

(c) In case the Commissioner of Agriculture or his deputy finds bacteria counts in error as made by a certified operator, the manager of the plant in which the errors are found shall be notified in writing of the correct counts and the plant manager shall cause payments to be made on the correct basis.

WEIGHING AND SAMPLING MILK AND CREAM

General Requirements and Regulations

1. No person shall weigh milk or cream or sample it for butterfat in licensed dairy plants or on bulk collection routes unless he has secured a certificate from the Commissioner of Agriculture certifying that he is competent to perform such work. V.S.A., Title 6, Section 2724.

2. Applicants for a certificate of competency to weigh and sample milk or cream must apply on a blank furnished by the Commissioner of Agriculture and arrangements will be made for an examination.

3. In order to qualify for a certificate to weigh and sample milk or cream, an applicant must answer ten questions in writing satisfactorily concerning the rules and regulations for weighing and sampling. Such ten questions will be chosen by the examiner.

4. All operators of licensed creamery companies and certified operators of weighing and sampling are hereby requested to comply with these rules.

THE STANDARD PLATE COUNT

20-004 Code Vt. R. 20-021-004-X

Amended: July 1, 963; October 18, 1971