Background last update:29 Jan 2008

Keeping moulds out of food and animal feed with propionic acid

The EU hygiene directive in force since January 2006 also applies to animal feed, requiring it to be in perfect condition. Animal feed products have to be free of mould and have a long storage life. Propionic acid is the ideal animal feed preservative. It is also an important element in the production of vitamin E. BASF has a long experience with propionic acid and Vanessa Holzhäuzer elaborates on the versatility of the acid.

By Vanessa Holzhäuser, BASF, Ludwigshafen, Germany

As everyone knows, you can't count on the weather. Its caprices may hit farmers hard. Too dry is bad, as is too wet. Farmers don't appreciate rain at harvest time, for example. The weather doesn't always play along, though. Farmers who want to ensure peace of mind have two alternatives: either to use special hot air systems to dry their grain prior to storage, or treat it with preservatives. The main thing is to prevent mould from developing. The toxins contained in mould can destroy a farmer's entire feed reserves. An eco-efficiency analysis conducted by BASF compared the two methods. The results show that using propionic acid is more cost-effective and better for the environment (see box).

Mixes to match every requirement

Farmers can choose from an array of propionic-based product mixes. The right product for a particular application depends on the moisture content of the grain and the planned storage period. Wetter grain and longer storage times call for more of the active substance. "Depending on the moisture content and storage period, farmers need an average of six to 15 kilograms of propionic acid to preserve seven metric tons of grain," says Ulrich Roser, BASF's technical advisor for feed preservatives. The preservative-treated grain is stable for around one year and is used by farmers for their own feed mixes, prepared by adding soy meal, minerals and vitamins. The mixes are mainly used for pig feed.

Propionic acid keeps the feed fresh for a long period of time. This acid, like formic acid and acetic acid, belongs to the family of carbonic acids. All three are potent fungicides and can be counted on to kill mould. However, propionic acid is a much more powerful agent than its shorter-chained siblings. The grain needs to be wetted all over with propionic acid in order to prevent mould from developing. Mould toxins cause fertility disorders, digestive problems and immune deficiency in animals. Propionic also effectively combats other pests such as yeasts, bacteria, and insects like the granary weevil, thereby protecting both animal feed and farm animals.

Natural product and energy supplier

The acid itself is fully digested by farm animals. In fact, dairy cows produce propionic acid in their own rumen as a major by-product of natural digestion: bacteria in the bovine stomach release propionic acid and acetic acid from the cellulose in the grass they eat. A single cow produces as much as one and a half litres of the acid per day and benefits from it as a source of energy. One kilogram of propionic acid has the nutritional value of two kilograms of barley. In the maturation process that goes to produce Swiss cheese, bacteria break up lactic acid products into propionic acid and carbon dioxide. The acid prevents the cheese from going bad during the long maturation period. Because of the acidic taste, the amount of acid in the cheese should not exceed a certain limit. The acid concentration may rise to as much as one weight percent – a level sufficient to preserve grain with a moisture content of 26% for a whole year.

Its reliability as a preservative also qualifies propionic acid for other agricultural applications, for example as an additive in liquid animal feed, hay and drinking water. Micro-organisms and algae are no longer able to grow and water does not get contaminated. Propionic acid is extremely effective in combating moulds and pests. It is also a major element in herbicide manufacture.

Animal feed market expands

The EU hygiene directive says that farmers and feed mix manufacturers must supply and use feed in perfect condition. Propionic acid-based preservatives are essential to achieve this aim. "Farm-mixed feed in particular is a vigorously growing market in Germany. Our shares in this segment are growing at a huge rate year on year," says Roland Preuss, product manager propionic acid.

With an annual production capacity of 110,000 metric tons of propionic acid, BASF is global market leader. More than 40% of the acid produced is used to preserve animal feed. The main markets for propionic acid are the USA and Europe. The Asian market is significantly smaller but growing at a faster rate.

In response to rising demand for propionic acid, BASF started up a new plant at the corporate site in Nanjing, China in summer 2005. The main Asian markets - China, India and Taiwan – have received their supplies from Nanjing since summer 2005.

Propionic acid preserves environment and budget

Propionic acid treatment is a more cost-effective and environmentally compatible method for preserving grain than drying and storage silos, according to a recent BASF eco-efficiency analysis. Farmers who use propionic acid are spared the cost of buying or leasing drying equipment and storage silos, as well as the cost of electricity and heating oil. The advantages continue to apply even for large grain volumes. Although capital investment in drying equipment and storage silos is relatively lower for large volumes, the environmental burden is higher.

Since propionic acid destroys the harmful microbes naturally present in animal feed, the animals digest the feed better and grow stronger and healthier. What's more, the rate of grain loss is lower than with other methods of preservation. Farmers benefit from shorter planting and harvesting cycles and from more efficient use of tillage areas.

The new BASF film "We ensure sustainable development" illustrates the method of Eco-Efficiency Analysis, using the example of grain preservation. A copy of the film can be ordered free-ofcharge via email (s.thib@trio-group.de).

Vitamin E, a growing market

In addition to its use as a preservative, propionic acid is also gaining importance as an element of synthesis. For instance, it is the first molecular element in the multistage process for manufacturing vitamin E. Approximately 45,000 to 50,000 metric tons of this vitamin are produced in the world today, and that figure is rising. Around two-thirds of the active substance, supplied in the form of a pale yellow oil, is used for animal nutrition. The main animal feed markets are the USA and Europe. South America, and, to a greater extent, Asia, are emerging markets. Vitamin E is now the world's second best selling vitamin after vitamin C.

High natural levels of vitamin E are present in young green fodder and wheat germ. The vitamin E content declines significantly as the plant grows. Vitamin E levels in mature grain are fairly low as a result, and farmers need to add the vitamin artificially when preparing feed mixes for their animals. Vitamin E is mixed with another 12 vitamins in poultry and pig feed, corresponding to 30 to 150 grams per metric ton of feed mix. It makes animal breeding more efficient because the animals stay healthier. Vitamin E significantly enhances meat quality. This nutrient protects the cells, and vitamin E stored in fat depots stays effective in the slaughtered animal. The meat keeps its healthy colour and stays fresh longer. Propionic acid in food does a lot of good in its own right, not just as an element in vitamin E production. In the form of a calcium bond, it helps to keep sliced bread fresh. This multitalented acid is also in great demand as a raw material for the chemical and pharmaceutical industry. It is used among other things in the manufacture of pharmaceuticals and it is in large-scale technical systems for the manufacture of aromatic aldehydes and acids.

In recognition of its many benefits, propionic acid's range of applications is increasing. Its main function is and remains as a preservative in animal feed and food. The use of propionic is set to increase in agriculture in particular, not at least because of a recent eco-efficiency analysis. The results leave no room for doubt: A farmer who thinks ecologically and acts economically will opt for propionic acid.

Source: Feed Tech, Volume 10, nr. 7


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