Laboratory Supply Update

Dairy Foods, March, 2001 by Donna Berry

To be competitive in dairy manufacturing and distribution, in house labs are investing in rapid testing technologies such as those for microbial safety, composition al analysis and even on-line standardization. These tests save time and effort, which ultimately translates to saving money.

Ensuring it's safe and pathogen-free

For the actual dairy plant, there are two primary areas where rapid microbial testing is used. The first is to monitor the cleanliness of the environment. The second is focused on detecting the presence of pathogens in food. This article focuses on the latter.

Rapid microbial assays enable processors to respond quickly to potential food safety problems. Acceptance by the dairy industry of rapid microbial tests seems to vary by pathogen, and is based on reliability, customer request and desired turnaround time. Most conventional microbial tests take five to 10 days, with rapid tests taking anywhere from hours to a day and a half.

With speed comes a price. Some rapid microbial tests can cost as much as three times more than conventional methods. These expenses are associated with personnel training, special reagents and equipment. However, it is advised not to think of the cost per test but rather in the value of the information obtained.

By obtaining results quickly, dairies can identify production run problems early, which reduces waste and product hold times. The value here comes in the form of saving contamination, inventory and warehousing costs.

The primary benefit, there fore, of rapid microbial testing is that processors can obtain results before product leaves the plant. This prevents the possible outbreak of food-borne illness and expensive and consumer confidence-damaging recalls.

Rapid analysis of milk components

Rapid testing is also available for compositional analysis. This type of test can be used to analyze raw material, mixed or finished products.

Raw material purchases in the dairy industry are typically based on solids or fat content, with prices fluctuating with current market values. Obtaining accurate milk composition information in a timely manner can therefore help dairies save money.

For example, let's assume that cream has a current market value of $1.70 and an average ice cream plant consumes 50,000 gallons of cream daily. If the agreement between supplier and purchaser is negotiated for cream with a fat content of 39% but the cream is actually coming in at 38.5% fat, the financial loss for the dairy is significant.

If the dairy has the ability to perform a rapid test on the cream composition, the supplier should hopefully negotiate a price adjustment. Based on the example, this amounts to about $200 a day, which over the course of a five-day work week year comes to more than $50,000.

It's also helpful to monitor fat contents during the manufacturing process. Quick adjustments can be made in order that the finished product meets specifications. For example, if fat is high during an in-process check of low-fat ice cream mix, fat content can be reduced with the addition of condensed or powdered milk, both of which contribute nonfat solids.

A patent-pending fat and moisture composition test, which incorporates microwave drying with high-performance nuclear magnetic resonance (NMR) technology, is now available to dairy processors. Unlike more traditional fat analyses like the Mojonnier and Babcock methods, which can take anywhere from four to six hours to obtain results, the new Smart Trac System [TM] provides results in four to five minutes.

"The combination of microwave and NMR technologies will revolutionize fat analysis for process control applications," says Bobbie Haire, process product mgr. for the Smart Trac System.

This solvent-free, non-destructive, direct measurement system determines both free and chemically bound fat, which previously could only be measured using the labor-intensive conventional methods.

Major Types of Rapid Microbial Assays

Antibody-based assays

These tests rely on the simplicity versatility and high specificity of antibody antigen interactions, similar to those responsible for allergic reactions in humans.

Examples include:

* Latex agglutination

* Immunoprecipitation

* Enzyme-linked immunosorbent assay (ELISA)

* Immunodiffusion

* Immunosensors

* Immunomagnetic separation

Nucleic acid-based assays

These tests rely on the uniqueness of the pathogen's DNA or rRNA. Examples include

* DNA probes

* Polymerase chain reaction (PCR)

* Ligase chain reaction (LCR)

* Reverse transcriptase polymerease chain reaction (RT-PCR)

Source: Drake, M.A. Mississippi State University and the international Food information Council Foundation.