In Macbeth, Shakespeare anticipated what many American cooks envision about food processing. Eye of newt, root of hemlock, and gall of goat are not approved ingredients in processed foods. That segment of the play is rather offensive in many ways. I don’t believe William would get his dialogue past the censors if he wrote it today. Food processing is more straight-forward and less mysterious than its critics tell us. Many commercial processes have counterparts in the modern American kitchen. My goal this week is to demystify food processing. Most of what we hear about food processing is not accurate.
First, let’s clarify what we mean by ‘real’ food. In Metabolical ‘real’ refers to any natural food that hasn’t entered a processing plant to make it toxic. Raw fruits, vegetables, nuts, seeds, meat, eggs, and similar items are ‘real.’ Cooking and other home food preparation techniques do not threaten a food’s ‘real’ status. ‘Real’ foods maintain their integrity and are recognizable by the original ingredients used. Or are they? Do homemade cornbread, lasagna, cookies, or moussaka pass this test? Processed foods are not ‘real.’ Or are they?
There are three purposes of food processing. Commercial operations make foods safe, extend shelf life, and preserve nutrients. Dealing with microbes is Job One for food preservation. Most raw foods are teeming with microbes that can turn the item unpalatable or make us sick. Most raw foods undergo rapid deterioration. Fruits and vegetables continue to act as living organisms after harvest. Biological activity includes using up nutrients leaving less for us. Unless consumed in a reasonable time, raw fruits and vegetables die and become food waste.
We call food from animal muscle dead meat for a reason. Meat undergoes chemical deterioration after slaughter of the animal. Processing kills or inhibits microbes to prevent spoilage and food poisoning outbreaks. Processing slows or eliminates biological activity in whole foods until consumption. It also slows microbial spoilage to the same end. At the same time, it halts loss of vitamins and minerals. Traditional food processes sacrifice flavor, color, and texture of real food. It keeps food safe, stable, and nutritious.
Metabolical lists four things that processing does to real foods. Processing forms dangerous chemicals, strips away good stuff, and changes its properties. The book is right, but home cooking does the same things. The processor has better control over its operation than most home cooks. In many processes, the changes are less severe in the processed product than the homemade one. The fourth thing that processing does? It adds preservatives. This week I describe how processing affects chemical formation, nutrients, and food properties. Next week I take on preservatives and other food additives.
Faith Hill told us that the secret of life is that there is no secret. Critics claim that there are secrets about food chemicals and processing Big Food won’t tell us. I taught FDST 4040/L, Food Chemistry for years. Then I swapped courses with the instructor of FDST 4010/L, Food Processing. There are no secrets about food chemistry or processing. Everything you want to know about these topics are in two textbooks. Read about these topics in Fennema’s Food Chemistry and Food Processing Technology.
NOVA classifies foods and ingredients into four categories. Let’s look at the processes associated with each category below:
GROUP 1: unprocessed or minimally processed food. Minimal processes include boiling, pasteurization, and roasting. These three processes use heat to kill microbes to increase the safety and slow spoilage of the food. Roasting and baking forms AGEs as the food turns brown. The dangers posed by AGEs are controversial. AGEs formed in food processing are no more dangerous than those produced in home cooking. Most home cooks would be reluctant to avoid roasted meats, baked bread, toast, and coffee. Boiling strips away essential vitamins and minerals. Southerners recapture some of those lost nutrients by drinking the potlikker. Steaming is a more nutrient friendly practice.
Pasteurization also uses less heat to kill harmful microbes while minimizing nutrient losses. Any type of heat applied to a ‘real’ food induces profound changes. The more heat applied, the more changes in color, flavor, texture, and nutritional value. Food processors have precise controls to reduce undesirable changes while maintaining safety. Home cooks may skirt safety concerns to achieve more desirable flavor and texture.
Refrigeration, drying, vacuum-packaging, and freezing are other minimal processes described by NOVA. Instead of killing harmful microbes, these techniques slow their growth. Refrigeration lowers the temperature of the food. A simple rule-of-thumb is that every decrease by 10ºC (18ºF) cuts microbial growth in half. Drying lowers the amount of water available to bacteria. A half-dried food like mushrooms or tomato sauce becomes more likely to become moldy. Moldy foods can produce toxins. Vacuum packaging is good in a way and bad in a way. Microbes that need oxygen to survive do not grow in a vacuum. There are some dangerous microbes that do grow in the absence of oxygen. Know the properties of the packaging material and the food to prevent safety hazards. Baked potatoes wrapped in aluminum foil in the refrigerator can lead to botulism.
Freezing lowers both temperature and the availability of water. Partial freezing of intact fruits, vegetables, and meats breaks down cellular structure. Molecular interactions at these temperatures can lead to undesirable flavor, color, and texture. Blanching is a mild heat process performed before freezing to inactivate enzymes. Enzymes in ‘real’ foods can lower both sensory and nutritional quality of frozen foods. Even at very low temperatures, enzymes can damage the food. Enzyme activity is very slow at frozen temperatures. In the freezer, these enzymes have a long time to damage the food.
Non-alcoholic fermentation leads to dramatic changes in food properties. Think milk and yogurt or vegetables and kimchi or flour and bread. Fermentation employs beneficial microbes to change molecules in ‘real’ food. These modifications change the food’s flavor, color, texture and nutritional properties. Yes, a fermented food is a processed food. These changes are NOT minimal. Most food processes target harmful microbes to slow spoilage and keep the food safe. Fermentation is the exception. Inhibiting enzymes is another target of these processes. Remember all these ‘minimal’ processes result in processed food.
GROUP 2: processed culinary ingredients. Culinary ingredients come from nature by pressing, refining, grinding, or milling. Many common off-the-shelf ingredients contain unapproved components. Pressing separates an ingredient like olive oil from its natural container. Grapes are also pressed to form juice or the material to make wine. Refining produces sugar and salt. Refining of sugar is a dangerous process that strips away fiber and nutrients. Table salt is either mined or recovered from salt water and then purified. Certain specialty salts contain valuable minerals stripped away during purification. To get the benefit of these minerals we end up consuming too much sodium. Grinding and milling break down food into smaller particles. Milling can render fiber less effective or expose fats to oxidation.
GROUP 3: processed foods. Canning is the only process mentioned in association with Group 3 that is not mentioned in Groups 1 and 2. Anyone who ever operated a steam retort to can vegetables knows it is not a gentle process. Steam retorts are giant pressure cookers. I became the retort operator on the night shift my second day on the job when the regular person failed to show. There were eight, twelve-foot retorts arranged in a convex semi-circle. The heat was almost unbearable. My mission was to turn on and shut off the valves for steam and cold water in proper sequence. It was not an easy task for a skinny college kid. The least worst thing that could happen was to ruin a batch of asparagus. Each batch was worth more than my dad paid for his 1965 Buick LeSabre brand new. The worst thing that could happen was that the retort could take off like a rocket ship and kill us on the catwalk.
Canning goes through a 12D process. For every trillion cans processed, one could contain an active botulinum spore. The unlucky people eating from that can could get botulism. The canning industry has a remarkable record of botulism-free product. Outbreaks associated with botulism trace back to operator or process-design error. I have no qualms in eating a commercial canned food. When I was a recruiter for Food Science majors, I met 4-H students who presented me with their home canned food. I accepted their precious gift and thanked them for it. When I went home, I threw the treasure away. I was not going to risk botulism! Think of the damage to my legacy from a case of botulism!
GROUP 4: ultra-processed foods. NOVA recommends a diet of Group 1 and 2 foods with an occasional item from Group 3. NOVA urges us to avoid all Group 4 foods. Ultra-processing involves operations that have no domestic equivalents. Processes included in Group 4 are extraction, hydrogenation, and hydrolyzation. Extraction involves removing ingredients from intact foods. Most of these ingredients add flavor to recipes that are not recognizable as ‘real’ foods. Any product with the name extract falls into this category. Think pure vanilla extract, amaretto flavor, or almond extract. Millions of Americans extract flavor volatiles to make their morning cup of coffee.
Hydrogenation was a process to make products like salad dressings and spreads smoother. Partially hydrogenated oils contain trans fats. If we see one of these oils listed on a package, it must be an old food. In 2018, the FDA disallowed use of them in commercial products. Critics of processed foods still warn us about trans fats in processed foods. Hydrolyzation occurs during molecular interaction with food components such as starch. The amylase in our mouth hydrolyzes starchy foods like bread and baked potatoes.
Extrusion, molding, and preprocessing for frying are techniques unacceptable to NOVA. Extrusion is a cooking process that mixes, shapes, and forms processed foods. Think Cheerios, sausage, and Cheetos. It is not difficult to see why these foods classify as ultra-processed. But wait, all pastas, whether manufactured or homemade, are also extruded. Homemade fudge and nougat are also extruded, but we should not eat such sugared foods anyway. Any food formed to a specific shape undergoes molding. Think cheese balls, ice cubes, holiday cookies, chocolates, and deviled eggs. What cook hasn’t dipped raw chicken into an egg sauce then rolled it into some type of breading? OK, none of us should be eating fried foods in any form.
Bottom line. Processing keeps foods safe, prevents waste, and preserves nutrients. There is nothing magical about it. The primary target of processing is to kill microbes or slow their growth. Despite contrary claims, most industrial processes have a counterpart in the kitchen. Foods prepared at home do not need as long a shelf life as foods processed in a commercial plant. The home process may not be as vigorous as the commercial one. Home preparation is also on a much smaller scale than commercial operations. The difference is one of degree and not one of technique. Both home cooking and food processing can produce toxic chemicals. Both ways of making food can strip away nutrients. Home cooking and food processing make profound changes in the properties of a ‘real’ food. That is why we cook and process.
The dirty little secret is that ultra-processing is not about processing. It is about industrial formulations. What are they? Tune in next week for the sequel.
Next week: Chemical processing. What is it? Why is it dangerous?