Tremendous strides have been made in the last century to improve the quality of the foods we eat. Yet every year millions of Americans are stricken by food-borne illnesses. In most developing countries people are at even greater risk.
Because many challenges remain, the chemical-engineering community continues to work on even more advanced techniques for purifying, sterilizing, and modifying the ingredients in the foods we eat.
Purification
Food purification during processing is essential to remove such contaminants as salts, metals, bacteria, fungi, and pathogens. Membrane-based separation systems, pioneered by chemical engineers, have now become the purification methods of choice for many food processors.
Getting the impurities out
Most food ingredients and processed foods contain unwanted contaminants, such as:
- Suspended solids,
- Dissolved salts,
- Metals,
- Bacteria,
- Fungi, and
- Other pathogens.
Chemical engineers have invented a variety of processes to remove these substances, thereby improving food quality, safety, and aesthetics. One of the most widely used processes today is membrane-based separation.
Membrane-based separation
This technique uses pressure during food processing to force unwanted impurities out through a semipermeable membrane. Differences in size, shape, or surface charge determine what is and is not removed.
Semipermeable membrane materials developed by chemical engineers include cellulose acetate, ceramics, and polymers. Numerous physical membrane configurations have been devised to separate unwanted solids and dissolved compounds from foods and beverages on a commercial scale. Membrane-based separation provides significant cost and performance advantages compared with such traditional separation techniques as centrifugation, vacuum filtration, and sand or diatomaceous earth filtration.
Different types of membrane-based separators use reverse osmosis, microfiltration, ultrafiltration, or nanofiltration systems based on the size and structure of the membrane pores. The size of the pores regulates the size of the solid particles or liquid droplets that can be removed.
While numerous commercial designs are currently available, chemical engineers are constantly striving to develop even more advanced membrane-based separation systems that are more efficient, effective, and cost-effective.
Safety
Contamination by microorganisms is the most common cause of food-borne illnesses and spoilage. Chemical engineers have been responsible for commercial-scale sterilization techniques, such as high temperatures, high pressures and vacuums, and preservatives. Now irradiation is used to kill microorganisms without sacrificing food quality, appearance, or nutritional value.
Battling the bugs
Although the U.S. food supply is among the safest in the world, food-borne illnesses are not at all uncommon. Chemical engineers have devoted considerable effort to developing and commercializing technologies to control such microorganisms as Escherichia coli, Salmonella, and other disease-carrying pathogens.
Traditional methods
Eliminating microorganisms from meat and poultry, seafood, dairy products, grains, fruits, and vegetables helps reduce spoilage and protects consumers from food-borne illnesses. Traditional methods have typically been based on the use of high temperatures, chemical preservatives, or exposure to high pressures or vacuums. To be effective any process must:
- Kill microorganisms in great numbers;
- Cause no damage to meat proteins and other constituents;
- Function effectively and economically in large-scale operations; and
- Not affect food appearance, taste, texture, color, or nutritional value.
Irradiation
In 1997 the U.S. Food and Drug Administration first approved the use of irradiation to kill disease-causing bacteria and parasites and spoilage-causing microorganisms. Today, about 40 countries allow the irradiation of food and agricultural products.
Chemical engineers and food scientists pioneered this effective process. Through extensive research they discovered that low doses of ionizing radiation effectively killed disease-causing bacteria and delayed food spoilage. At the same time taste and appearance were not affected. Extensive testing has also shown the safety of this method: the approved energy levels were too low to induce radioactivity.
Genetic modification
The crossbreeding of plants over many generations was once required to produce foods with more desirable or enhanced traits. Now with techniques developed by chemical engineers, genetic materials can be quickly and precisely transferred from one organism to another. Among the results are stronger, more nutritional products.
Stronger, bigger, better plants
Plants that have been modified genetically may be used to produce crops with
- Higher nutritional content,
- Greater resistance to herbicide and pesticide damage,
- Increased resistance to disease,
- Specific desirable traits (e.g., faster ripening or delayed softening), and
- Reduced allergenicity.
Genetic modification is a technique for changing the characteristics of a plant or organism to produce more desirable traits. For many years these changes were done by natural selection. Now genetically modified foods are produced using an artificial form of DNA called recombinant DNA (rDNA). In simplest terms rDNA with a positive trait is transferred into an organism lacking that trait to create the desired improvement.
Longer-lasting tomatoes
The first agricultural product produced in the United States using rDNA was introduced in the 1990s. It was a plant that produced tomatoes with a longer shelf life. The plant was genetically modified to produce less of the enzyme that causes tomatoes to ripen and soften. Since then many other rDNA-modified crops—fruits, vegetables, and grains—have been introduced with improved traits.
Predictable results
Historically, researchers introduced desired traits into plants by crossbreeding over multiple generations. This relatively hit-or-miss approach took a long time. By comparison, genetic-modification techniques allow researchers to identify one or more genes responsible for a particular trait and then insert them into a plant with greater speed and precision. The end result is highly predictable.
Future goals
Chemical engineers continue to work with food scientists and biotechnologists to develop more advanced techniques to transfer genetic materials from one organism to another. Genetic modification of foods is one of the most promising and safest strategies available to increase total global food production, reduce crop losses, and increase nutritional content.