CHEMICAL ENGINEERING INNOVATION IN FOOD PRODUCTION
“If the grass on the other side of the fence appears greener . . .
it must be all the fertilizer they are using.” Kevin Rodowicz
The inherent safety, convenience, availability, nutritional content, aesthetic appeal, and
variety that typify our food supplies are a hallmark of modern life, but this was not
always the case. For the last 100 years we have been witnessing dramatic advances in the
scientific understanding and engineering techniques that increase agricultural production
and allow for the commercial-scale production of countless processed foods. Through the
concerted efforts of chemical engineers and others, the yields and quality of farm crops
have increased exponentially, and the industry producing and packaging foods and
beverages has evolved to a business worth many hundreds of billions of dollars.
Early food-related businesses usually consisted of small stores selling primarily fresh,
locally grown foods with a limited shelf life. Before modern engineering advances were
widely adopted by the food industry, the variety of foods available at stores were
determined by what was produced locally, since transportation limitations dictated the
distance that perishable foods could travel.
The 20th century, with its two World Wars, space race, immense technological advances,
and rapid modernization, brought unprecedented advances in the tools and techniques to
ensure food safety and improve nutritional value and aesthetic appeal. Ingenious
packaging options and sterilization methods were also developed extending
transportation distances and the shelf life of foods. These changes have brought a much
more varied cornucopia of foods to people all over the world.
Chemical engineering know-how can be credited with improving the conversion of raw
foodstuffs into safe consumer products of the highest possible quality. Chemical
engineers routinely develop advanced materials and techniques used for, among other
things, chemical and heat sterilization, advanced packaging, and monitoring and control,
which are essential to the highly automated facilities for the high-throughput production
of safe food products.
Chemical engineering unit operations and methodologies, developed for other industrial
purposes, are used by the food industry, including drying, milling, extrusion,
refrigeration, heat and mass transfer, membrane-based separation, concentration,
centrifugation, fluid flow and blending, powder and bulk-solids mixing, pneumatic
conveying, and process modeling, monitoring, and control. The food-related application
of chemical engineering technology involves interdisciplinary teamwork, which, in
addition to the expertise of chemical engineers, draws on that of food technologists,
microbiologists, chemists, mechanical engineers, biochemists, geneticists, and others.
Technological milestones
Over the years, cleverly engineered solutions have increased the production of processed
fruits and vegetables, dairy, meat and poultry, and seafood products, and have allowed
more widespread distribution of such foods. The following are some of the most
revolutionary improvements in food processing noted in the “Milestones of the Twentieth
Century” by the Institute of Food Technologists (www.ift.org).
1900s. Vacuum packaging, which removes the oxygen from inside the food package, was
invented to prolong the shelf life of foods, and the widespread practice of freezing foods
began with fruit and fish. The first ready-to-eat cereals using many chemical engineering
unit operations appeared as well.
1920s. Quick-freezing processes for foods were first commercialized by Clarence
Birdseye, whose name has become practically synonymous with frozen foods. Birdseye
found that by blanching vegetables (cooking them briefly in boiling water) just before
freezing, the process could deactivate certain enzymes that cause off-colors and offflavors, thereby enhancing the quality of the thawed vegetables. The first commercial use
of “puffing” to produce such cereals as Cheerios and puffed rice also began.
1930s. Freeze-drying processes were pioneered. Frozen foods are dried after deep
freezing, in which the entrained water is removed by a process known as sublimation by
heating the frozen product in a vacuum chamber. Freeze-dried foods in turn become
shelf-stored foods that quickly regain their original flavor, aroma, size, shape, and texture
after rehydration. The removal of water slows spoilage, thus providing longer shelf life,
and reducing the weight of the food, which makes it cheaper and easier to transport.
1940s. The advent of automated processes to concentrate, freeze, and dehydrate foods
enabled a greater variety of foods to be mass-produced and packaged for shipment
overseas to military personnel during World War II. Aseptic packaging drastically
improved food quality, safety, and nutrient retention.
1950s. Controlled-atmosphere packaging using plastic increased the shelf life of fresh
foods. The process controls oxygen and carbon dioxide levels inside the packaging
environment to limit respiration by fruits and vegetables (akin to human breathing) and
reduces the amount of off-gas ethylene produced, which delays ripening and spoilage.
1960s. The first commercial-scale plant began producing freeze-dried foods and coffee.
Advances in aseptic processing allowed shorter heating times for sealed food containers.
1980s. Modified-atmosphere packaging began to be used widely. It is a more advanced
variation of controlled-atmosphere packaging, in which the “head space” atmosphere
within a food package or the transportation/storage vessel is modified by flushing it with
a blend of inert (nonreactive) gases. Aseptic processing and packaging were also widely
adopted in the U.S.
1990s. The U.S. Food and Drug Administration (www.fda.gov) first approved the use of
irradiation to control harmful bacteria in fresh and frozen poultry and meats. Highpressure processing was also commercially applied first to fresh packaged foods to kill
microorganisms that cause spoilage without altering flavor, texture, or appearance.
Advances in chemical fertilizers, herbicides, and pesticides
Early mankind experimented with human and animal wastes, seaweed, ashes, menhaden
(a fish used by coastal Native Americans), and other substances to fertilize crops and
increase yields. Over time such trial-and-error attempts to boost yields gave way to the
focused application of science and technology. Chemical engineers have applied their
expertise to chemically synthesize fertilizers, herbicides, and pesticides that promote crop
growth and protect crops from weeds, insects, and other pests. Today, the use of these
products is more important than ever to meet the needs of an ever-expanding population.
Fertilizers Nitrogen
is the most plentiful part of the air we breathe, present at 79% by
volume and a prime nutrient (most often in the form of ammonia).
Modern fertilizers stem from a chemical engineering breakthrough pioneered by Fritz
Haber in 1908 who developed a process to synthesize ammonia by reacting hydrogen and
nitrogen. In 1918, he was awarded the Nobel Prize in Chemistry for this discovery.
Working with industrialist Carl Bosch, Haber scaled up the successful Haber-Bosch
process that allows ammonia to be produced cost-effectively in commercial quantities for
use in nitrogen fertilizers. Haber’s original reaction was carried out under high pressures.
The improved ammonia synthesis process carries out the reaction at lower pressures and
temperatures, which helps save money by reducing the amount of energy required by the
process. It allows the use of less costly materials and engineering designs for reactors,
piping, and other components. (In general, higher pressures and temperatures require
more expensive materials and specialized designs.)
Many people consider the Haber-Bosch process one of the most monumental chemicalengineering achievements of all time, thanks to its direct impact on global food
production.
Pesticides and herbicides. Chemists and chemical engineers have also been instrumental
in the discovery, synthesis and commercial-scale manufacture of numerous chemical
compounds that function as pesticides (to kill insects) and herbicides (to kill weeds).
Various pesticides and herbicides work in different ways. For example, chemical
engineers discovered that when glyphosate (the primary ingredient in Monsanto’s widely
used herbicide Roundup) is applied to a crop, it inhibits a specific growth enzyme called
the EPSP synthase. Glyphosate is rapidly metabolized by weeds, and unlike many other
earlier herbicides, it binds tightly to soil so that it does not accumulate in runoff to
contaminate surface waters or underground aquifers. Today, 80% of U.S. soybean fields
use glyphosate to eliminate weeds, which is widely used on other types of crops as well.
According to its manufacturer, it eliminates more than 125 kinds of weeds, but does not
effect mammals, birds, fish, or insects.
The herbicidal activity of glyphosate was first discovered in 1970 by Monsanto’s John
Franz, for which he received the National Medal of Technology in 1987 (the highest
honor awarded to America’s leading innovators by U.S. President). In 1990, he also
received the Perkin Medal for Applied Chemistry from the Society of Chemical Industry,
and in 2007, he was inducted into the National Inventors Hall of Fame.
Advanced food processing technique
Techniques to improve the flavor, texture, nutritional value, safety, appearance and
overall aesthetic appeal of various foods—involving cooking over fire, smoking,
steaming, baking, fermenting, sun drying, or preserving with salt or spices—were already
being practiced before recorded history.
Today, imaginative and effective engineered approaches—many drawn directly from the
chemical engineers’ toolbox—routinely add nutrients, improve aesthetic appeal (in terms
of a food’s flavor, texture, and appearance), enable longer distance transport (leading to
multiseasonal availability), extend shelf life, and remove microorganisms that contribute
to spoilage and are responsible for food-borne illnesses. Modern food processing can also
improve the quality of life for people with food allergies (by removing or neutralizing the
proteins and other substances that create allergic reactions in certain people) and for
diabetics (by reducing sugar content and providing sugar-free alternatives).
Consistent, predictable food quality is of paramount importance. For instance, coffee beans
can be roasted to ensure uniform, batch-to-batch consistency in color, flavor, and aroma.
The steps needed to achieve such consistency could not have come into being without the
direct contribution of chemical engineers.
The roasting of coffee beans requires exceptionally precise control of the chemical and
physical reactions over time. Depending on the progressive bean temperature experienced
during roasting, final flavor characteristics can vary widely. Chemical engineers have
devised ways to make timely adjustments to the roaster to moderate airflow rates and
manipulate bean temperatures without changing the flavor.
Sterilizing and packaging perishable foods
Before modern food-packaging technologies were widely adopted, foods available to
consumers were limited to what could be produced and transported locally. By devising
novel packaging, chemical engineers have helped people everywhere enjoy a more
bountiful selection of foods. Modern-day packaging marvels include traditional metal
cans, newer multilayer packages that allow foods to be heat sterilized right in the
package, and packages with oxygen and carbon dioxide levels that slow ripening and
spoilage.
Sterilization is a key aspect of any food-packaging operation. The ability to sterilize
foods to protect them against spoilage by oxidation, bacteria, and molds has always
presented an important engineering challenge. Throughout history, people have
experimented with the use of dehydration, smoking, salting, pickling, candying and the
use of certain spices.
Chemical engineers have made enduring contributions to reducing spoilage and giving
foods greater shelf life. They include high-temperature pasteurization and canning,
refrigeration and freezing, chemical preservatives (using such compounds as sulfite,
sodium nitrite, ethyl formate, propionic acid, sorbic acid, and benzoic acid), and
irradiation.
Traditional canning. In the late 1790s, French confectioner, Nicolas Appert, discovered
that many foods (including meats, fruits and vegetables, and milk) will resist spoilage for
extended periods once they are sufficiently heated and sealed in airtight glass containers.
By the early 1800s, his promising preservation principles were demonstrated by the
French Navy in tests on meat, vegetables, fruits, and milk. Building on his discoveries,
England’s Peter Durand developed a way to seal food in lightweight, easy-to-seal,
unbreakable, airtight containers made from tin-plated iron, for which he received a patent
in 1810. This technique ushered in a whole new era in food safety. Today safe,
wholesome canned foods remain a staple in every pantry.
A skilled tradesman used to make about six to ten tin cans per day by hand. Bryan Dorkin
and John Hall who set up the first commercial canning factory in England in 1813
dramatically changed the food-processing industry. By the 1920s, mechanized factories
became widespread and could produce around six cans per hour. Today’s systems,
however, can produce 1,500 cans per minute or more.
In addition to automation processes that enable the commercial-scale production of cans,
the container has evolved from steel to aluminum and then to a variety of metal alloys.
These advances have significantly reduced the weight and material cost of cans.
Meanwhile, ongoing engineering advances have enabled food processors to move from
batch to continuous processing and to apply mathematical models for process control to
significantly reduce over- and undercooking. For example, through modeling, investigators
found that by simply rotating the cans during cooking, they could significantly reduce
process time, yielding products with more consistency and better aesthetic attributes.
Pasteurization. In the early years, no one knew how Nicolas Appert’s process preserved
foods successfully, but the ability to can foods meant that Napoleon’s army fighting a
long way from home could be fed properly and safely and that British sailors could
maintain a healthier diet by feasting on fruits, vegetables, and meats while on long
voyages overseas.
More than 50 years later, Louis Pasteur (1822–1895) solved the mystery by
demonstrating that the growth of microorganisms is the primary cause of food spoilage
and food-borne illnesses and that a high percentage of them could be killed by heating
liquids to about 130°F (55°C) or higher, for relatively short periods, without altering the
chemical makeup of the food. This simple process became known as pasteurization and
was quickly and widely adopted.
Aseptic packaging. First introduced in the U.S. in the early 1960s, it provides major
advantages over traditional canning. It allows many products once considered perishables
such as milk and juice to be packaged, distributed, and stored for months or longer
without the need for refrigeration, irradiation, or chemical preservatives. In general,
during aseptic packaging, both the food and packaging are sterilized at high temperatures
for very short periods. The sterile container is then filled in a sterile atmosphere.
The original technology superheated steam to sterilize cans. Pressurized heat exchangers
and holding tubes allows the foods and beverages to be sterilized at around 300°F. This
rapid (“flash”) heating and cooling process substantially reduces energy requirements and
nutrient losses much better than conventional high-temperature sterilization. It also
allows processing times of less than 1 minute, speeding production rates.
Foods processed using aseptic packaging retain their vitamins, minerals, and desired
textures, colors, and flavors more effectively than those processed with traditional
canning. In 1989, aseptic-packaging technology was voted the food industry’s top
innovation of the last 50 years by the Institute of Food Technologists.
Advanced packaging options. For fresh fruit, vegetables, meat, seafood, and dairy
products, slowing the ripening process and protecting perishable foods against spoilage
have helped connect worldwide food sources with new markets. People can find
strawberries, raspberries, bananas, mangoes, and kiwis at their corner market in winter,
and fresh meat, poultry, and seafood far from any farm or fresh- or saltwater source.
Chemical engineers were intimately involved in developing vacuum packaging, in which
the food is first placed into a gas-impermeable bag, the air within the bag is vacuumed
out, and the bag is sealed. This process reduces the oxygen inside the bag, so the
microbes that spoil food cannot survive.
Improvements on traditional vacuum packaging—controlled-atmosphere packaging
(CAP) and modified-atmosphere packaging (MAP)—represent chemical engineering
breakthroughs. During CAP, oxygen and carbon dioxide levels inside the food packaging
are controlled to limit fruit and vegetable respiration and reduce the amount of off-gas
ethylene produced. This technique slows ripening and spoilage of fresh produce.
When MAP, an advanced version of CAP is used, a customized blend of inert
(nonreactive) gases (most often carbon dioxide and nitrogen) is pumped into the shipping
container and the food package to replace oxygen in the “head space.” It not only slows
ripening, but also prevents many natural reactions that cause foods to spoil.
The invention of chemically sterilized “brick packs” was another important chemical
engineering contribution to food safety and convenience. The multilayer packages are
widely used to package juice, milk, tomato sauce, and countless other products. Brick
packs protect contents from spoilage and provide extended shelf life without the need for
refrigeration.
The ingenious, brick-shaped package is typically constructed from high-quality
paperboard, plastic (such as low-density polyethylene), and aluminum with each layer
playing a specific role.
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The paper layer gives the carton stiffness and strength.
The polyethylene layer makes the package liquid-tight and keeps gases or odors
from passing into or out of the package.
The aluminum layer protects the food contents from exposure to light or oxygen,
both of which cause many foods to degrade rapidly.
A protective coating on the exterior keeps the package dry.
Recently, flexible, laminated “retort pouches” are used as an alternative to traditional
metal cans or glass jars. The multilayered retort pouches are filled with wet foods,
sealed, and then heat-treated to sterilize the contents so that the food within the pouch
is never exposed to air until eaten and stored without refrigeration until opened. This
thin, multilayer retort pouches allow high-temperature sterilization using shorter
heating times than for traditional canning. It not only saves money for the food
processor, but also reduces the risk of overcooking and preserves the desired color,
texture, and nutrient value of the processed foods. This process technology is widely
used to supply sterile, prepackaged foods for soldiers, astronauts, hikers, campers,
and consumers.
Ingredients and food additives
Chemical engineers have worked closely with food scientists for decades to find ways to
isolate and produce natural and artificial flavors, as well as other food additives at a
commercial-scale.
Natural sweeteners. Refined
sugar (sucrose, in the form of crystallized sugar or sugary
syrups) is produced most often from sugar cane or sugar beets and has long dominated
the natural sweetener market. The commercial-scale production of refined sugar involves
a variety of chemical-engineering unit operations including
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milling the shredded raw materials,
mixing the raw materials with water,
adding chemicals to adjust and control the pH (a measure of the acidity of the
mixture),
removing impurities using such technologies as centrifugation and filtration,
crystallizing and drying sugar crystal, and
treating wastewater.
Artificial sweeteners. Calorie-conscious consumers and diabetics value artificial
sweeteners with a sweetness level of 500-600 times greater than those of traditionally
refined sugar. While its early discovery was accidental, chemical engineering expertise
perfected the synthesis of these chemical compounds and commercial production.
The earliest artificial sweetener, saccharine, was discovered in the late 19th century, and
its widespread commercial availability as “Sweet N Low” helped usher in a diet
revolution in the U.S. in the 1950s. Recently, aspartame (made of two amino acids,
phenylalanine, and aspartic acid) has emerged as a leading artificial sweetener, Equal,
and as the food additive NutraSweet, it is now used in thousands of processed foods
including diet sodas, desserts, yogurt, and candy.
Another artificial sweetener (sucralose), sold as Splenda, is made from sugar unlike the
other artificial sweeteners. Using a patented process, its makers produce a no-calorie,
chlorinated derivative that tastes like sugar with virtually no bitter aftertaste. The process
selectively replaces three hydrogen-oxygen groups on the sugar molecule with three
chlorine atoms. This change in molecular structure converts sucrose to sucralose, which,
according to Splenda’s manufacturer, is an inert (nonreactive) molecule. Once the
product is consumed, it passes through the body without being used for energy, so it has
no calories and the body does not recognize it as a carbohydrate.
The chemical discovery, synthesis, process design, and scale-up used to produce these
low- or no-calorie artificial sweeteners would be impossible without innovations based
on chemical engineering principles.
Natural and artificial flavors. Many processed foods we eat today contain a variety of
natural and artificial flavors. Natural flavors are essential oils, oleoresins, and essences
that are typically extracted or distilled from such products as spices, fruits or fruit juices,
vegetables or vegetable juices, plant materials, meat, seafood, poultry, eggs, dairy
products, or fermentation products of such foods using roasting, heating, enzyme-based
processes, and other techniques.
Artificial flavors are chemical compounds synthesized in the lab by chemical engineers
and other technical professionals to mimic the flavors found in nature and then
manufactured in commercial-scale quantities. There are only four basic categories of taste
your tongue can differentiate (sweet, salty, sour, and bitter), yet the nose can differentiate
thousands of distinct odors. As a result, most artificial flavors require a blend of both
taste and smell components to create the total signature flavor experience.
Starches from various sources are a major source of nutrient carbohydrates in processed
foods and often added as an ingredient to achieve a desired function. Starches are added
to many foods, ranging from soups, stews, and gravies to pie filling, sauces, and custards.
Since starches absorb water and become a gel when cooked, starch additives help thicken
many foods and improve the stability of the food during heating, intense mixing, or long
shelf life. They also help give many foods a good “mouth feel.”
Chemical engineers have played a key role in isolating the desired starch from various
cereal grains (such as corn, wheat, rice, and sorghum), roots and tubers (such as potatoes,
sweet potatoes, cassava, and arrowroot), and other sources, and then in engineering
systems to produce easy-to-use, free-flowing powdered starches in commercial-scale
quantities. Such systems use a variety of chemical engineering processes including wet
grinding or milling, screening or sieving, washing, centrifuging, dewatering, and drying.
Chemical engineers have also devised a variety of processes such as cross-bonding,
esterification, or reaction with acids or enzyme to alter natural starches to produce socalled modified starches. When added to processed foods, modified starches provide a
range of desired characteristics, such as increased resistance to heat, bacteria, or acid
exposure. In pharmaceutical applications modified starches can be used to help such
products as aspirin or other tablets disintegrate more quickly in the presence of moisture
(such as saliva).
Powder and bulk-solids processing
In recent years, powder and bulk-solids processing has become more technically
sophisticated, with advances in the areas of weighing and feeding bulk solids, separating
and classifying powders, characterizing particles, pneumatic conveying, drying, mixing
and blending, and managing both dust emissions and the electrostatic hazards that can
arise when dusts are present in enclosed areas. These advances have had a tremendous
impact on food processing and have enabled the commercial-scale production of foods
powdered form, such as cake mixes, powdered pancake mixes, and cocoa.
Convenience foods
Modern-day consumers love “convenience foods,” for which chemical engineers
invented the many automated processes needed to concentrate, freeze, dehydrate, and
otherwise process such foods.
Fast-cooking foods. Fast-cooking, or “instant,” foods, such as quick-cooking rice,
canned soups, packaged bake mixes, and canned and frozen vegetables are often prepared
by hydrating and then precooking the foodstuff, after which the treated products are dried
to reduce the moisture content and prolong shelf life.
Early efforts to produce fast-cooking rice, beans, and other legumes, however, often
made trade-offs in terms of nutrition. Such processing typically required nutrient-rich
outer bran layers to be removed (because they tend to absorb water slowly and thus slow
the cooking process). To avoid this trade-off, chemical engineers developed foodprocessing techniques allowing highly nutritious brown rice, wild rice, beans, and various
crop seeds to be cooked quickly without sacrificing their nutrient-rich outer layers. For
example, whole grain, brown, or white milled rice is heated to create cracks in the outer
layers and then hydrated with water, cooked to partially gelatinize the starch content, and
then cooled and dried for packaging.
Frozen foods. Chemical engineers also have helped devise the processes to produce
frozen foods retaining their appearance, texture, taste, and nutritional content when
thawed and cooked. For instance, investigators found that quick-freezing processes could
keep large ice crystals from forming in the foods and help thawed foods retain fresh taste
and texture. Similarly, when vegetables are first blanched (swift cooking in boiling water)
and then frozen quickly, the combined process suppresses certain enzymes causing
discoloration and “off” flavors.
In freeze-drying processes, food material is introduced to a vacuum chamber where it is
frozen, and then most of the water is removed by sublimation by reducing the chamber
pressure to a few millibars, which is finally subjected to controlled heating to remove any
remaining water. Freeze-dried foods have a long shelf life and quickly regain their
original flavor, aroma, size, shape, and texture, once water is added back to them, which
reduces spoilage and the weight of the food, making it easier and cheaper to transport.
In quick-frozen processing, pieces of fruits or vegetables remain free-flowing and retain
their natural characteristics after thawing, and can be used for decoration or adding
texture and flavor to such processed foods as jams, confectionary products, and ice
cream.
Advances in food purification
While the U.S. food supply is among the safest in the world, millions of Americans are
stricken every year by food-borne illnesses. Contamination by bacteria, mold, and other
microorganisms is by far the most important cause of such illnesses, so chemical
engineers have been working hard to commercialize effective technologies to control
such microbes as Escherichia coli, Salmonella, and other disease-carrying pathogens.
Such systems typically use high temperatures, high pressure or high vacuum, and
chemical preservatives. In all cases these techniques must be able to kill microorganisms
at sufficient levels, be controlled in large-scale operations, be cost-effective and
economical, and function without damaging meat proteins and creating unwanted
changes in food appearance, taste, texture, color, or nutritional value.
Membrane-based separations
Until they are purified, most food ingredients and processed foods contain unwanted
contaminants, such as suspended solids, dissolved salts, metals, bacteria, fungi, and
pathogens. Chemical engineers have invented a variety of engineered processes that
allow food processors to remove these substances to improve food quality, safety, and
aesthetics. Today’s membrane-based separation is used widely to remove impurities
during food processing by pressure to force unwanted substances in food ingredients to
pass through a semipermeable membrane. It is also used broadly in the dairy industry,
principally as a processing step in making soft cheeses and in separating and recovering
soluble whey proteins (milk albumins and globulins) from whey--a necessary by-product
in the process for producing hard cheeses. The recovered whey protein, typically as a
concentrate or dried, has considerable commercial value as an additive to a wide variety
of other food products.
Chemical engineers have created a broad array of semiporous membrane materials,
including cellulose acetate, ceramics, and polymers (such as polyacrylonitrile and
polyvinylidene fluoride), as well as numerous physical configurations to enable them to
separate unwanted solids and dissolved compounds from foods and beverages. Compared
with traditional separation techniques such as centrifugation, vacuum filtration, and
filtration using sand or diatomaceous earth, membrane-based separation provides
numerous cost and performance advantages.
Membrane-based separation systems are classified as reverse osmosis, microfiltration,
ultrafiltration, or nanofiltration, based on the size and structure of the membrane pores
(this dictates the size of the solid particles or liquid droplets to be removed). Numerous
designs are available, including tubular, hollow-fiber, plate-and-frame, and spiral-wound
configurations. Chemical engineers strive to develop advanced membrane-based
separation systems to maximize the available surface area, reduce membrane pore size
(for the more precise removal of smaller contaminants), minimize the pressure drop the
fluid will experience when flowing through the unit, and maximize cost-effectiveness.
One particularly innovative use of membranes is under development by the U.S. Army,
which involves a “self-hydrating” pouch containing a reverse-osmosis membrane that
separates two compartments. When water from any available source—lakes, rivers,
ponds, or even puddles—is taken into one of the compartments and is forced through the
membrane, more than 99.9999% of bacteria in the dirty source water is removed. This
cleaned water is then used to hydrate beverages or dry-ration foods contained in the other
compartment. This ingenious invention allows combat troops to produce clean drinking
water in sustainable supplies rather than having to carry clean water.
Existing membrane-based systems that produce drinking water from untreated sources
often use reverse-osmosis membranes (as does this self-hydrating pouch), but they
typically require a pump to force the water across the membrane. By comparison, this
design relies on a process called forward osmosis, in which during operation water is
pulled through the membrane without a pump lightening the load combat troops must
carry.
The drivers of the process are specific ingredients in the beverage powder or dehydrated
food contained in the self-hydrating pouch. The water moves across the membrane in the
direction of charged ions such as salts, sugars, and amino acids in the foods to equalize
the osmotic pressure inside the pouch.
Irradiating food. In 1997, the U.S. Food and Drug Administration first approved the use
of a technique known as irradiation to kill disease-causing bacteria and parasites and
spoilage microorganisms in fresh and frozen poultry and meats. Today, the irradiation of
food and agricultural products is allowed by about 40 countries.The approval by U.S.
regulators validated what food scientists had known for a long time through extensive
research that low doses of ionizing radiation absorbed by various foods could effectively
kill such disease-causing bacteria as Salmonella, E. coli, and Listeria, and delay food
spoilage. Extensive testing of food irradiation shows that treated foods are not at risk of
“becoming radioactive,” because approved energy levels are too low to induce
radioactivity.
Beverages. During the fermentation process of producing wine, beer, or spirits, yeasts are
used as enzymes to convert starches into simple sugars, which are converted to ethanol
(an alcohol). Secondary metabolic reactions give various alcoholic beverages their
characteristic aromas and flavors.
In beer brewing, supplemental enzymes are also used to accelerate the malting process,
suppress the formation of off-flavors, or help break down unwanted residues. In wine
production, enzyme can help improve juice recovery during the pressing of grapes and
adjust flavors and aromas. In the production of alcoholic spirits, enzymes are often used
to break down unwanted starches and carbohydrates. Many enzymes used today in food
processing are produced in bulk with the help of genetically modified microorganisms.
Today, numerous advanced polymeric membranes provide a support structure on which
to immobilize enzymes. Membrane characteristics of hydrophilicity and porosity affect
the performance of immobilized enzymes, as does the orientation of the active sites on
the membrane. Hydrophilicity refers to the ability to attract or repel water molecules and
the porosity of a membrane the size and configuration of the openings dictating the size
of the particles, droplets or molecules that are allowed to pass through them.
Genetically modified foods
Genetically modified foods are produced using so-called recombinant deoxyribonucleic
acid (rDNA) techniques to produce desired changes in the characteristics in plants,
animals, and food-related microorganisms (such as yeasts and enzymes). Recombinant
DNA techniques are used today to give genetically modified crops greater nutrient
content, greater resistance to damage by herbicides and pesticides, as well as cropdamaging diseases faster ripening or delayed softening, andless “allergenicity.”
Chemical engineers work with food scientists and biotechnologists to advance the
techniques needed to effectively transfer genetic materials from one organism to another.
Historically, researchers have sought to produce desired traits by cross-breeding plants
over multiple generations—a relatively hit-or-miss approach. By comparison, geneticmodification techniques allow researchers to identify one or more genes responsible for a
particular trait and then insert them into a plant or microorganism with greater speed and
precision. This process results in safer and more predictable results.
The first agricultural product generated using rDNA in the U.S. was introduced in the
1990s with a plant producing tomatoes with a longer shelf life, which was achieved by
genetically modifying the plant to produce less of the enzyme that causes tomatoes to
ripen and soften rapidly. Since then, other rDNA-derived crops for fruits, root and leaf
vegetables, and grains with desired traits have been introduced.
Many consider the ability to produce genetically modified foods the most promising
strategy available today for increasing global food production by reducing crop losses
and increasing the nutritional value of treated crops.