Nutrition

Licorice, peanut puffs, corn flakes, snack bars, breakfast cereals in all shapes and colors, pasta, crispbread, soy meat, cat and dog food, everything passes through the extruder. The extruder swallows almost everything and converts cheap raw materials into expensive products. But who knows this magic machine, responsible for a number of groceries that have found their way to the shelves of our supermarkets?

Slowly the semolina pulp sinks into the funnel of the extruder. Underneath, inside a metal sleeve, a steel spiral is turning, soaking up the nutritious mass and pushing it forward. It’s getting tighter. Huge shear and pressure forces mercilessly move the pulp forward. He’s getting hotter and hotter. At the end of the pipe, the mass is passing with high pressure through a nozzle. Suddenly the mass is released, water evaporates and the pulp puffs up. Rotating knives cut the airy mass into the desired shape. Vitamins that fell by the wayside during this procedure are injected from fine nozzles. Ready are your breakfast cereals!

History of the Extruder

According to the dictionary, extrusion means: “To express a product through a nozzle, a hole or a slot in order to obtain a certain shape.” The first products to come out of an extruder were seamless lead pipes. Today, a wide variety of plastic pipes and profiles are made, but also bricks, copper wires, coated wires, soaps and much more are pressed through the extruder.

It wasn’t long before the food industry discovered the extruder for its own purposes. In 1869, pieces of meat were squeezed through the machine and stuffed into sausage skins. The extruder is indeed reminiscent of the good old meat grinder. The extrusion principle has already for a long time been used in pasta processing. Hydraulically driven piston presses squeeze moistened semolina through perforated plates, forming spaghetti, macaroni, spirals, stars and letters. Roller extruders and piston presses also transform sugar masses in the confectionery industry into all conceivable shapes and forms.

With the introduction of the screw extruder in the pasta industry during the mid-1930s, began the modern age of the extrusion process in food technology.

Structure of the Cooking Extruder

In simple terms, each extruder can be divided into the following parts. First comes the feeding zone, comparable to a funnel. This is where the raw material, be it flour, semolina, a porridge, ground peanuts, starch or a sugar mass, is fed in. A screw, sometimes two co-rotating or counter-rotating screws, transport the mass forward.

This is followed by the conversion zone. This is where things are mixed, compressed, heated, melted, transformed. Mechanical and thermal reactions take place. That is why the extruder is sometimes referred to as a bioreactor.

Now the processed product comes to the discharge zone. A nozzle is the limit. The nozzle and subsequent rotating knives determine the shape of the product to a wide extent. When the heated mass is pressed through the nozzle, the water in the product evaporates abruptly due to the drop in pressure. It results in a blown-up product, giving it a porous, light an airy structure. In principle, extruding mimics the conventional production of popcorn. Popcorn puffs at around 9.5 bar and at a temperature of about 350⁰F (175⁰ Celsius).

The Result: Product Diversity

The extruder swallows almost everything, whether waste products or valuable raw materials. Depending on the process, dry raw materials, moistened or pulpy masses are processed. Often the heat generated by the shear forces and pressure alone is enough to transform the material into the desired shape. This is referred to as cold extrusion. The friction normally results in temperatures of 90 to 140⁰F (40 to 60⁰C). However, there are also processes where additional heat must be added. The warm extruder works with 160 to 270⁰F (70 – 130⁰C) and the hot extruder with 270 to 480⁰F (130 – 250⁰C). Most cooking extruders are based on combinations of frictional heat and externally supplied heat. The pressure is in the range up to 200 bar.

The variety of products from the extruder is overwhelming. Many conventional baking or cooking processes are replaced by the extruder. Today, almost all breakfast cereals come from the extruder. A new generation of crispbread has emerged. It has an airy, light, longitudinal fiber structure.

Milling waste products such as bran and grinding meal are refined in the extruder, given new structures and afterwards are added to baked goods. Breadcrumbs and modified starch, as well as many instant foods, such as instant soups, are now produced in the extruder. Oil can be extracted. Chewing gum and even chocolates are made in the extruder. A lack of taste, due to the fast production or less valuable raw materials needs to be compensated by many tricks and trade secrets of the industry.

An interesting product is also the long egg. Boiled, sliced eggs are used a lot for garnishing. For practicality, egg yolk and egg white are separated and cleverly reassembled in the extruder. The end product is a meter-long rod, in which the yolk is always nicely placed in the middle of the egg white. There is no waste when slicing.

What Happens to the Nutrients?

The starch from raw products is almost completely broken down, so it becomes easily digestible. It comes to gelatinization and swelling, sometimes also to undesired roasting processes.

Little is known about the conversion of protein in the extruder. However, it is known that some important amino acids are destroyed. At the other hand, it has been shown that harmful enzymes in legumes, such as trypsin inhibitors in the soybean, are rendered harmless by the heat. The changes in extrusion are very versatile and can only be investigated in very complex and expensive processes. That is why there are not yet many independent results about adverse side effects of the extrusion process.

Losses are partially reduced because mass is only exposed to the high temperatures for a short time. Nevertheless, the high heat causes a substantial loss of vitamins. Cereal products provide us with the important vitamins of the B group and with folic acid. Depending on the process, there are losses of 50 – 80%. In comparison, with normal bread baking, the losses of B vitamins are between 5 and 30%. Nutrition experts recommend treating the raw materials as gently as possible. What happens in the extruder can certainly not be described as gentle. That’s why the breakfast cereals need to be subsequently enriched with vitamins.

Conclusion

Extruder products have become an integral part of our diet. Children especially demand them frequently. Be it in the form of snacks, sweets, snack bars, or breakfast cereals. But we would do well to limit it. In a nutshell, extruder products are mostly air that is sold with a lofty price tag. Expensive products are made from cheap raw materials. In case of doubt, the food industry will pay attention to the taste the consumer will crave for and less to the nutritional value that contributes to a healthy lifestyle.

If we put extruder products on the table, we should definitely vary them with conventional cereal products, in addition to fresh, untreated fruits and vegetables, nuts, and seeds. They are the ones who provide our body with important nutrients for our health.

Stay Always Up to Date

Sign up to our newsletter and stay always informed with news and tips around your health.

Sign Up Now!

Selenium occurs only in traces in the human body. An adult weighing 70 kg has just about 7 milligrams on average. In medicine, selenium is considered a vital, essential trace element. It plays an important role in detoxifying the body, protects the membrane of our body cells, prevents red blood cells from oxidizing and is part of some important enzymes.

Occurrence

Selenium belongs to the semi-metals. It stands at the 59th place in the frequency of the elements in the Earth’s surface. It rarely occurs in nature in its pure form. We usually find it in compounds with sulfur. Selenium minerals are also rare. Clausthalite and naumannite are known examples. Selenides are found in copper gravel and zinc blend. Selenium is used in the semiconductor industry for the production of photodiodes, photocells, radar systems, solar cells and light meters. It is used in photocopiers because of its photoelectric property. Tiny additions to glass give it a bright red color. In the red traffic lights, we experience this color in daily life.

The vital necessity of selenium for plants, humans and animals was only discovered in 1957. With selenium deficiency, young animals do not gain weight properly. In humans occur very specific deficiency diseases.

Functions in the body

Selenium fulfills its most important function as a component of the enzyme glutathione peroxidase. This important enzyme is mainly found in red blood cells. It protects them from attack by harmful oxygen radicals that are produced in normal metabolic processes, but also by smoking, alcohol, ozone, smog and ionizing radiation.

Together with vitamin E, the enzyme also protects all cell membranes. Various fats are built into the membrane, which are wafer-thin boundary layers, that must be particularly protected. If such biological membranes are destroyed, premature cell death or genetic damage to the DNA occurs.

However, the body uses this selenium-containing enzyme very sparingly. If it is consumed, it is regenerated by vitamins C and E. Vitamin B2, carotenoids and anthocyanins also play an important role in this metabolic process. So we see the importance of a diet rich in vitamin-packed unprocessed plants.

Selenium is also contained in another enzyme, iodinethyronine-5-deiodase. Here it controls the conversion of the thyroid hormone thyroxine into the biologically active form. It therefore has an influence on the basal metabolic rate, cell differentiation, cell growth and the rate of cell division.

Selenium also plays a role in the detoxification of heavy metals. It binds cadmium, lead and mercury, so that these toxic metals can no longer bind to vital proteins.

Selenium also stimulates the immune system. Research in recent years also suggests that selenium plays an important role in cancer prevention. In cancer patients, a much lower selenium levels are found in the blood.

Deficiencies

Some soils are very low in selenium. This affects Central and Northern Europe but also large parts of China. An increased incidence of the so-called Keshan’s disease has also been found there. In its chronic form, this disease manifests itself as cardiac insufficiency with simultaneous enlargement of the heart muscle. In the area where this disease has occurred more frequently, the salt has been enriched with selenium and has thus been able to be suppressed.

The first symptoms of selenium deficiency include myopathies, which are muscle weaknesses. Metabolic disorders of the liver and pancreas are often associated with a selenium deficiency. Low levels of selenium in tissues have also been found in various forms of arthritis and degenerative joint diseases.

It is interested to notice that in those areas of China where the soil is selenium deficient, mortality of COVID-19 was much higher than in other parts o the country. That stresses again the importance of Selenium for the immune system.

Chemotherapy of cancer as well as oxygen therapies lead to increased formation of free radicals, which can be intercepted by selenium and other antioxidants.

Selenium-rich Foods

Animal foods generally contain higher amounts of selenium than plant foods. But selenium from the plant is more bioavailable, so it is more easily absorbed by the body. High amounts of vitamin C, being still in the physiological range, improve the absorption from the gastrointestinal tract.

Nuts and seeds have high amounts of selenium. The Brazil nut has by far the highest selenium content, even multiple times more than animal products. Chia and sunflower seeds have moderate amounts of selenium, Soybeans and white beans are also good sources. Substantial amounts are also found in whole grain, millet and rice, but this depends on the selenium content of the soil. Finland is a very selenium-poor area. The soils there are enriched with selenium. Other countries in Central and Northern Europe are also discussing enrichment.

Those who live in areas with selenium-poor soils should not eat exclusively products from their own garden or the farmers from the surrounding area. Supplementing your diet with some nuts and seeds grown in tropical areas can help to balance this deficiency. Brazil nuts tend to be especially high in selenium, but can vary greatly depending on soil conditions. Eating just two Brazil nuts normally gives you more than your daily need. Since Brazil Nuts are so high in selenium, you should be cautious to not overuse them, though eating up to 4 nuts daily on a regular basis you should be still in the safe zone.

Overdosage and Poisoning

Before it was discovered that selenium is vital for humans, the trace element was considered one of the most toxic elements. However, acute selenium poisoning has occurred very rarely. In the production of glass and paints and in electronics, where selenium is used, however, protection of employees is necessary.

An overdosage is highly unlikely via food alone. However, supplementation with selenium is increasingly popular. Corresponding preparations are already on the shelves of supermarkets and drugstores. Whether a general supplementation can be recommended is controversial because the knowledge about the trace element is still insufficient. Therefore, an independent intake of selenium-containing supplements should be discouraged. They belong in the hands of an experienced doctor. It is certain that the additional intake of selenium is recommended for cancer, special forms of arthritis and certain cardiovascular diseases. However, the amounts to be taken vary depending on the respective course of treatment. This again shows that only the attending physician should decide on selenium supplementation.

Varied Diet

To avoid a selenium deficiency, a balanced diet is key. Problems are only likely to arise in areas with selenium-poor soils and limited food choices at the same time. With the exception of the Brazil nut, plant products have lower selenium levels, but this is made up by better absorption and better recycling of selenium containing enzymes. Once again it has been shown that a varied diet with a high proportion of plant-based food is the right way to go.

Kiwis from New Zealand, tomatoes from Mexico, bananas from Ecuador, grapes from South Africa … Shopping in the supermarket is like immersing yourself in the big wide world. Also, contemplating the variety of fruits and vegetables available, it is hardly possible to tell which season is outside the supermarket. A huge logistic is behind the extensive product range.

Long Transport Chains

The food supply sometimes requires very long transports and the associated consumption of a lot of energy, not only for transport, but also to cool the goods. In addition, there is the energy and raw material for the production of the packaging material and the many plastic foils used for cultivating vegetables. The transport of food over long distances has increased because of global trade unions.

To reduce these energy expenses, local produce should be given preference. This has many advantages, also for the consumer. Fruits and vegetables can be harvested when they are ripe, since there are only short transport routes. Mature products not only taste better, the nutritional value is also higher.

Tracing Phytochemicals

In recent years, scientists have been following very closely the traces of the so-called phytochemicals in natural produce such as fruits, vegetables, cereals, legumes, herbs and teas. These are substances that the plants produce for their own pest protection and to avoid being eaten. But it also includes coloring and flavoring substances, plant toxins and hormones. In nutritional science, these substances were predominantly referred to as unhealthy and anti-nutrients. Today the tide has turned. Cancer research, in particular, indicates that there is more to be found in fruits and vegetables than minerals and vitamins. More of these valuable ingredients can be found in mature products that are in season and that could grow on organic farming.

Exotics from Overseas

Overseas fruit is usually harvested unripe. Chemical agents are often used to suppress the natural ripening process, trying to bring the products to the market when they are ready for consumption. Unfortunately, that doesn’t always work. Often the hard, tasteless fruits are just a far reminiscent of the exotic ones that you got to know on your previous vacation. Certainly nothing is wrong with adding some tropical fruits every now and then to the menu. But local products should preferably be served.

Seasonal Fruits and Vegetables

Vegetables from the greenhouse and cultivated in tunnels have higher nitrate contents than vegetables grown in the open because of the lack of sunlight. More pesticides must also be used. Such residues can be reduced with a seasonal diet. In winter and spring, winter hardy vegetables should therefore be preferred: lamb’s lettuce, kale, leek, storable vegetables such as cabbage, carrots, red beets, celery, endive, radicchio, apples and pears. Pumpkins also last well into winter. Let’s also get the first green from the wild, such as dandelions, wild garlic, ground elder, violets and daisies.

Direct Marketing

Marketing directly from the producer to the consumer contributes a lot to securing the livelihood of local small and medium-sized farms. Associated with this is the preservation of the rural landscape and of cultural assets. By shopping from the farm or at the farmers’ market, we can also do a lot to avoid waste. Around half of the volume of household waste is packaging, of which around 90% are food packaging.

Products from Organic Farming

Organic farming techniques not only take into account the lower environmental impact, but also results in healthier and better-tasting products. Organic farming offers reasonable alternatives for many problems. Pollution of soil, air, water and food is reduced, besides the superior taste and nutritional value. In addition, the biodiversity is being preserved by cultivating varieties that are not used in large scale commercial production.

Cultivation in the Garden

Growing in your own garden more than pays off – despite the cheap goods at the supermarket. The short way from the garden to the kitchen guarantees freshness and quality. There are also other health benefits: exercise in the fresh air while gardening and the joy of working with the Creator. Growth and prosperity come from him. The gardener sows, cherishes, cares and is looking forward to the harvest.

Rethink

In this sense, spring offers a good new beginning. Let’s learn to rethink. The comfortable reach on the supermarket shelf is not always the best way. Let’s start with our own garden, let’s plant a few vegetable patches again. Maybe we go out of our way to buy directly at the farm and give preference to local products. Many small steps pave the way to better health and a more intact environment.

Stay Always Up to Date

Sign up to our newsletter and stay always informed with news and tips around your health.

Sign Up Now!