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The Secret Lives of USDA Food Chemists

Posted by Dr. Michael D. Sussman, Director, AMS Laboratory Division in Research and Science
Feb 28, 2012
“I personally find the samples with human impact most interesting,” says Lauren Shoemaker, pictured here with, Jonathan Barber (middle) and Dr. Kouassi Dje (right).  Food chemists at USDA’s National Science Lab help monitor the quality and wholesomeness of the foods we eat.
“I personally find the samples with human impact most interesting,” says Lauren Shoemaker, pictured here with, Jonathan Barber (middle) and Dr. Kouassi Dje (right). Food chemists at USDA’s National Science Lab help monitor the quality and wholesomeness of the foods we eat.

This post is part of the Science Tuesday feature series on the USDA blog. Check back each week as we showcase stories and news from the USDA’s rich science and research portfolio.

Food chemistry is the study of the chemical processes and interactions that happen within our foods.  By examining different components like water, starches and fats found in foods, we can learn how to enhance or prevent different natural and unnatural chemical reactions from happening in our food.

For instance, food chemistry helps us understand natural processes like the fermentation that turns milk protein into yogurt or the use of different freezing speeds to preserve color and flavor in vegetables. Carbohydrates, fats and proteins are some of the main food components studied by food chemists, but we also examine the water, vitamins, minerals, additives, flavors, colors and enzymes, found in foods.

A lot of the work we do at the National Science Laboratory (NSL), a part of USDA’s Agricultural Marketing Service (AMS), involves checking the quality of food products to make sure certain specifications are met.  As with many areas of science and research though, each of our food chemists bring their own perspectives to the field of food chemistry.

“I personally find the samples with human impact most interesting,” says Lauren Shoemaker, a molecular biologist/chemist.  “For instance, we began testing milk products for melamine and cyanuric acid after several deaths were associated with these chemicals.”  These tests were added to the analysis of fat, salt, protein, moisture, mineral and vitamin content already being conducted by the lab.

Examining the water content and its influence on the quality of food is also a key piece of the work done by food chemists.  Our food is made up of mostly water—with meats being about 50% water and some fruits and vegetables being made up of 95% water.

“It is water that supports the growth of micro-organisms,” says Dr. Kouassi Dje, lead chemist. “Water is also the solvent for other biochemical reactions that influence spoilage in foods, and the level of water in any food affects its long term stability.  Efforts to preserve food products are driven by the control of water through drying, freezing, or manipulating water activity with preservatives.”

By determining the moisture content of food, our food chemists can look at the wholesomeness of products throughout their shelf life, and can make sure U.S. companies meet the regulatory requirements needed to market foods domestically and internationally.

“We strive to provide our customers—the U.S. Military, the American public and international customers—with the most accurate information and food testing,” says Jonathan Barber, Chemist in Charge at NSL.  “We take pride in delivering quality test information to our customers and our role in ensuring the quality of foods we eat.”

Category/Topic: Research and Science

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Brian Rice
Feb 28, 2012

Why does the U.S. Military require information about food testing?

Brady Carter
Feb 29, 2012

Thank you for the information about the testing at the lab. I hope though that your USDA lab is not trying to use moisture content to determine shelf life since in your own regulations, you list water activity as the most important moisture measurement for determining product shelf life. Since the work of Scott in the 50's, this has been known. There are still many producers who are mistakenly trying to use moisture content to determine product safety when they need to be measuring water activity. I hope that as a USDA facility, you wont perpetuate in the incorrect idea that producers should be measuring moisture content to determine product safety and shelf life. Thanks for your consideration.

Mar 14, 2012


The USDA AMS National Science Laboratory tests Meals, Ready-To-Eat (MRE). Meals, Ready-To-Eat are complete portions of one meal for one military person and are processed and packaged to destroy or retard the growth of spoilage-type microorganisms in order to extend product shelf life for 7 years. MREs are tested to determine if they meet DOD, Defense Personnel Support Center (DPSC) contract military specifications for an acceptable one meal serving, retorted pouched or 18-24 serving hermetically-sealed tray packed meat, or meal product regarding satisfactory analyses for fat, salt, protein, moisture content, added stabilizer ingredient, and sometimes microbiological composition. MRE's are for use by the DOD, DPSC as a component of operational food rations, and as an item of general issue by the military.

Thanks, Mike

Mar 15, 2012

Thank you, Dr. Carter, for your very interesting comment. You can rest assured that the USDA Agricultural Marketing Service’s Laboratory Division is testing water activity in samples sent to us by our stakeholders to ensure product quality.

Water activity is related to moisture content in a non-linear relationship known as a moisture sorption isotherm curve. These isotherms are substance and temperature specific. Isotherms can be used to help predict product stability over time in different storage conditions.

The USDA AMS Laboratory Division is a full service laboratory network providing analytical testing and assisting producers in meeting international regulatory requirements, domestic purchase specifications, and imported product testing requirements. Supporting the USDA's commodity program areas, other federal agencies, the agricultural sector and accredited to ISO/IEC 17025:2005 for specific tests in the fields of chemistry and microbiology, the Laboratory Division offers a full range of food and fiber product testing. Requests for laboratory services and inquiries are welcome. Just email us at

Thanks again,


Jul 03, 2012

What can we add to our frozen chick pea that has a dry flavor to give it more moisture. The issue is the taste is dry and it sits in warmers for hours.. any ideas?