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Film plates free technician time; eliminating need to prepare media and pour plates allows time for developing 'real-time' quality control techniques.

Historical numbers are of little value in controlling a process," said Dr. Barry Vermilyea, Director of Quality Control for Land O'Lakes' Dairy Foods Operations. "The data you get provides an assessment of what you did, not what you're doing."

As new technologies become available, Land O'Lakes seeks to implement quality control methods that provide "real-time" data. Implementing some new methods requires substantial investment, in the form of capital as well as labor. "It's possible to invest $20,000 in an analytical instrument, and then invest another $60,000 for initial calibrations," Vermilyea said. The additional expenses accrue in the form of lab time and labor for the wet chemistry or bacterial enumerations needed to establish the calibrations.

Other tools have offset labor requirements for implementing the improved QC methods. Labor savings have been realized through use of sample-ready film microbiological plates. Use of the film plates eliminates need for technicians to prepare and sterilize media, melt agar, and pour petri plates. Immunoassays and other screening methods are employed, freeing technician time by reducing the number of laborious "standard" methods.

Monitoring quality

Land O'Lakes is a cooperatively owned corporation with annual sales of about $2.5 billion. Land O'Lakes dairy foods membership includes 4500 "direct patrons" (dairy-farmer members) and a group of "Class A members". Class A members are other cooperatives, with their own direct patrons, that have a working agreement to produce Land O'Lakes product, to Land O'Lakes specifications.

Substantial laboratory resources are required to monitor raw milk. Annually, 4 billion lb of milk are received by Land O'Lakes for processing. Raw milk is purchased by weight, and payment to the producer is then adjusted on the basis of milkfat content, protein content, and a series of quality parameters.

To determine the final value of a producer's monthly milk shipments, tests must be performed for milkfat, protein, aerobic plate count, somatic cell count (an indication of udder health), absence of added water, and absence of drug residues. In addition to the tests for determining payment, regulatory tests are also required.

Further laboratory work must be performed to ensure that processing has proceeded as intended. Physical, chemical, and microbiological methods are used to indicate the efficacy of sanitation, completeness of pasteurization, and conformance of product to quality specifications. Tests are conducted to monitor process, ingredients, and finished products.

Historical data, acquired after-the-fact, have value in that they can be used to document that a parameter was within specification or to track a problem that occurred. Data that are available in "real time" have the added benefit of making corrective action possible.

Standard methods for detecting beta lactam antibiotics in milk are quite sensitive. Adulterated milk from a single farm can be detected even when diluted in an entire truckload. Time to complete detection, however, precludes the use of standard methods to screen a truck prior to unloading.

With the advent of "screening methods" requiring only 7-10 minutes, Land O'Lakes can screen truck loads prior to unloading, and thereby avoid contaminating still more milk that is in pre-process storage. Standard methods are then applied to confirm the presence of antibiotics and trace the source of contamination of the load. The responsible producer may be charged for the value of the load, which must be destroyed.

Technology for enumerating microorganisms in real time remains lacking, although Vermilyea indicates that impedance microbiology systems, used for screening at two Land O'Lakes labs, are a step in the right direction. Land O'Lakes is also keeping an eye on bioluminescence.

For the time being, most Land O'Lakes microbiological work is done utilizing methods employing nutrient media in which organisms grow to population levels sufficient to be detected. Although the time for incubation remains the same, sample-ready film plates have reduced labor required for test setup.

Standard plating methods require several basic preparation steps. Specific methods may require more.

In contrast, with sample-ready film plates it is necessary only to prepare the sample and pipette it onto the plate. Incubation then follows with traditional plating.

Methods utilizing film plates have been accepted by regulators as equivalent to standard methods. Lab technicians, certified under provisions of FDA's Pasteurized Milk Ordinance, may opt to be certified using film plates.

The specific tests performed at Land O'Lakes using film plates are aerobic plate count, coliform count, yeast and mold, and E. coli. All of the above, except yeast and mold, are AOAC methods.

Sample-ready film plates (which might be more accurately called cards) are more space efficient than traditional plates--both in storage and the incubator. Many Land O'Lakes technicians have come to prefer them. "The film plates not only require no media preparation, but they have a dye that stains the colonies...they're easier to read," said Vermilyea.

Although unable to quantify savings in dollars, Vermilyea contends that film plates are justified. "On strictly a material basis, film plates are more expensive by at least two or three times," Vermilyea said. However, labor costs offset the material expense. He continued, "In a couple of labs we've reduced overtime...that's a direct savings.

"In other labs, film plates allow labor to be re-used elsewhere by technicians being freed from media preparation. That allows allocation of time for development of the new real-time systems."

That work includes the initial calibration work for new analytical systems.

Complete information on Petrifilm[TM] plates can be obtained from 3M, Microbiology Products, Building 275 4E-O1, St. Paul, MN 55144-1000.
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Title Annotation:sample-ready film microbiological plates
Author:Eilers, James R.
Publication:Food Processing
Date:Dec 1, 1992
Words:902
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