Control Samples
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1999 Raw Milk Infrared Control Samples – Use Guide for Order 124/135
Handlers
Federal Milk Market Administrator – Seattle, WA
November 1, 2000
Introduction
In January of 1999, the Seattle Market Administrator developed a raw milk infrared control sample program for the benefit of federal order 124 and 131 handlers subject to pay test verification. Participation in the program is strictly voluntary and there is no direct charge for this service. This guide is intended for all laboratory managers. It describes the nature of the new control samples and how handler labs can derive maximum benefit from their usage.
Sample Description
Number of samples: 12
Approx. sample volume: 60 ml
Vial coding: by color (new sets marked by different color stripe on white
vial)
Source: Ohio Market Administrator (Ohio-based dairy farms)
Distribution frequency: 2 sets of 12 every two weeks
Target delivery arrival date: Wednesday via FEDEX (freight billed
directly to MA)
Target delivery temperature: <40oF (wet ice used)
Target reference chemistry: available by 11:00 am Friday (via Internet,
fax, or website)
Reference chemistry source: Seattle + Cleveland + Chicago + Louisville MA
Labs (each lab performs measurements in duplicate)
Approx. component ranges
Fat: 2.0%
Protein: 1.0+%
Preservative: Bronopol
Expected shelf life: 18 days minimum
Recommended Usage Parameters (based on Seattle MA Lab protocols)
Tempering temperature: 108oF (42oC)
IR readings per sample: 2-3 (for best results, omit the 1st reading to
minimize carry-over effects)
Instrument zero: Zero all channels prior to calibration; check
zeros at finish and rerun or make corrections to sample readings if necessary.
Primary reference results: fat by ether extraction (4-lab mean;
each lab runs duplicates), true protein* by
kjeldahl direct analysis (4-lab mean), total
solids by oven drying (4-lab mean)
Secondary reference values: ash = 0.5379 + 0.0596*protein
lactose = TS – fat – protein – ash - 0.19
other solids = TS – fat – protein
(= lactose + ash + 0.19)
SNF = TS – fat (= lactose + ash + 0.19
+ protein)
(since lactose is determined by difference, all reference
chemical values should be internally consistent -- i.e., all terms in above
equations must add and subtract perfectly)
Daily Calibration Check – possible approaches
{Handler labs differ widely in their calibration procedures. A few calibrate daily using a sophisticated array of controls and in-house pilot samples. Others calibrate biweekly using commercially available controls. The options listed below illustrate the broad range of approaches possible given a new MA control set. Since the MA cannot supply enough controls for daily calibration (the most rigorous approach), all lab managers who choose to use the new controls should consider how to ensure the accuracy of their particular IR between weekly (or biweekly) formal calibrations.}
optimum: daily calibration on MA controls (as performed by Seattle Lab)
approach A: weekly MA-based calibration immediately followed by a run of raw milk check samples (check samples should possess good range and must be stable over a week). The same check samples are then run first thing daily. If there is a sufficient number of check samples (e.g. 6-10), mathematical adjustments to slope and bias can be made whenever necessary. If check samples are few (e.g. 3-5) and a drift is indicated, recalibration using MA controls may be warranted.
approach B: same as option A but with biweekly MA-based calibration. Spare MA set is reserved for a marked shift (e.g. due, for example, to instrument service).
approach C: weekly or biweekly MA-based calibration with no daily checks other than intermittent check or "pilot" samples (e.g. use of a large stock of raw or homogenized milk every 30 minutes). This option recommended only if IR is demonstrably stable. An unusual shift in check sample or pilot should signal a recalibration.
Evaluation of Control Sample and IR Performance
With each biweekly reference chemistry mailing, you will find a questionnaire page relating to your IR calibration. This is a completely optional service. You may:
- ignore it
- use the e-mail version (in Excel) to plot your IR results against chemistry and personally investigate the quality of your calibration
- fill it in and send it to us for troubleshooting help when you're experiencing difficulties
- submit it regularly and request 6-month summaries of your IR calibration performance
In principle, regular use of the questionnaire (or similar records of your own) can be used for
- Ongoing evaluation of control sample quality and stability of calibration parameters
- Assessment of individual IR ability to achieve linear response
- Charting of individual IR instruments for tendency to drift
MA Contacts
For general questions, missing reference chemistry, replacement/additional control samples, sample integrity problems (e.g. leakers, cracked vials, too warm) , incorrect or altered shipping information
Please call: Seattle MA Lab
telephone: 877-252-9557 or 425-487-6009
fax: 425-487-2775
e-mail: seattlelab@fmmaseattle.com
For: Shipping containers (PLEASE RETURN BOXES BIWEEKLY via FEDEX to CLEVELAND!)
Ship to: Bob Malinak
USDA-AMS-Mideast
FMMA Lab
1325 Industrial Parkway North
Brunswick, OH 44212
Phone: 330-225-4758
Fax:
330-220-6732
Use FEDEX Priority Overnight or Standard Overnight
Bill to: third party, call Seattle MA Lab @ 1(877)
252-9557
for the
FEDEX account number.
(if you prefer to use another carrier (e.g. UPS ground), this is fine, however, the Seattle MA office will only cover FEDEX shipping charges)
For Lost shipments
Please call: Cleveland MA Lab (Bob Malinak - control sample
coordinator)
telephone: 330-225-4758, ext. 117
fax: 330-220-6732 (lab fax)
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