Detecting Chemical Contaminants & Residues in Food

image: food and vials

The SwRI food chemistry laboratory uses solid-phase extraction techniques that allow for sample extraction and interferent cleanup in fewer steps and with shorter turnaround times.


image: lab workers testing food

Chemical analysis of food samples begins with the use of household blenders to reduce foods to fine particles whose chemical components can be extracted for quick and consistent screening and analysis.


image of conversion chart

Some common food preparation practices can result in conversion of the naturally occurring amino acid asparagine into acrylamide, a potential cancer-causing compound, when heated to high temperatures in the presence of certain sugars.

In recent years, the news media have reported a number of food product recalls after consumption of these products resulted in illnesses and in some cases, deaths.

The most publicized recalls were those attributed to bacterial contamination, such as E.coli in spinach and peppers and salmonella in peanuts and peanut butter. Other large recalls have involved chemical contaminants, most notably melamine, normally used in the manufacture of plastics. This compound was added to pet food and dairy products to make them appear higher in protein. Recalls have also been prompted by the presence of undeclared ingredients, or higher than permitted levels of pesticide residues.

Collectively, these recalls have resulted in heightened consumer concern over the safety of our food supply. This concern has prompted food suppliers to spend millions of dollars testing their products to assure consumers that the products are safe.

Food Quality & Safety Services

Southwest Research Institute (SwRI) chemists and scientists have provided many services to clients in food quality and safety, ranging across the food industry spectrum from the farm to the fork, including:

  • Farmers
  • Distributors
  • Manufacturers
  • Wholesalers
  • Retailers

Most projects are initiated to solve a specific concern, such as:

  • Evaluating flavor components through the determination of volatile organics
  • Determining ethylene exposure of produce stored under a variety of conditions
  • Analyzing volatile organic compounds to predict shelf life of milk and cereal products
  • Kinetic studies to determine the effectiveness of bags in protecting produce from the effect of ethylene gas
  • Determining the source of food contamination from the storage environment
  • Investigating suspected intentional and unintentional food contamination
  • Evaluating the effectiveness of common household washing and food preparation methods in reducing the levels of pesticide residues in produce
  • Monitoring levels of potentially harmful compounds created in the production of food products
  • Determining the content of vitamins and other nutrients in foods
  • Determining 4-methylimidazole (4-MEI), found in caramel color, in beverages, and in seasonings
  • Determining acrylamide in baked and fried products, as well as in ingredients, and beverages such as coffee and cocoa
  • Determining bisphenol-A in packaging and products
  • Quick turnaround analysis for pesticide residues in produce

Food can be a single commodity, such as fruits and vegetables, or it can be very complex as are most processed foods. This presents many challenges to those who perform chemical analyses. Keys to the success of these analyses include sophisticated sample preparation and analytical techniques that aim to reduce interferences caused by natural and artificial colors, sugars, starches and preservatives. Because of the shelf life constraints of most foods, these analyses must be performed in a short period. Turnaround of data to the client typically ranges from a few hours to a few days from the time samples are received in the lab.

Over the past 20 years, food chemists and scientists at SwRI have analyzed more than 40,000 produce samples for approximately 150 pesticide residues. During that time, the food chemistry laboratory has had to stay abreast of changes in regulations and tolerances for specific compounds and commodities. Additionally, many compounds have been banned and newer pesticides put into use. The SwRI team has adapted its analyses in response to these changes and maintains a same-day turnaround for samples received at the lab. This constraint has pushed the lab to improve standard sample preparation and evaluation techniques.

Related Terminology

food quality and safety services  •  food product and packaging safety  •  acrylamide detection  •  food product recalls  •  phthalates detection  •  bisphenol (BPA) detection  •  pesticide residue

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Southwest Research Institute® (SwRI®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 10 technical divisions.
06/02/14