Is Sample Integrity Affecting your Dairy Test Results?

Welcome to the first edition of the all-new DQCI blog! Stay tuned for additional installments that address pertinent topics for the milk producer and dairy processing industries from our in-house experts.

The preparation of a sample is often overlooked for its importance in chemical, microbial, and/or Infrared (IR) analysis of dairy products. However, sample preparation is one of the most critical steps before analysis, especially due to the nature of dairy products, which are one of the most difficult matrices to homogenize. Examples of these difficult matrices include:

• Butter
• Cheeses (soft and hard)
• Condensed milk
• Dairy powders
• Dairy products with added ingredients (fruits, nuts, etc.)
• Raw dairy products (whole milk, creams, etc.)

In our experience, for all types of dairy products we encounter on a daily basis (which is a lot!), we must take steps to ensure products are properly prepared prior to analysis; this includes client samples as well as our calibration standards. Improper sample preparation can lead to repeatability/reproducibility issues as well as incorrect results. Without high repeatability and reproducibility, numerous complications arise such as, instrument calibration problems, product development errors, incorrect nutritional labeling, etc.

What can you do to ensure proper sample preparation of your dairy samples?

1. Always store samples at the recommended temperature for sample type. Usually 0 – 4.5⁰C for liquid sample storage and 20 – 25⁰C for dry sample storage.
2. Preserve any raw product whenever possible. Options are available in liquid and pill form.
3. Temper samples appropriately depending on the product type. The recommendation for liquid dairy samples is 38-42⁰ Most importantly, do not overheat.
4. Do not leave liquid dairy samples in any heated water bath longer than recommended. Keep in mind, tempering time depends on sample size and product density.
5. Slow tempering of dairy products is highly recommended to avoid fat layering and oiling off.
6. Thaw frozen samples slowly. Never use a microwave.
7. Prior to sampling, invert samples as recommended for the analysis.
8. Present samples within 1-2 minutes to prevent fat layering on non-homogenized samples.

We understand sample preparation can be complicated at times and, while these eights guidelines are just the tip of the iceberg, we hope it prompts careful consideration moving forward. After all, if you do not perform an appropriate sample preparation, then the subsequent testing can very well be meaningless, no matter how proper your analytical technique.