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New challenges for the preservation of bioethanol by-products
Around 5 million tons of by-products are produced by food and beverage companies every year in the Netherlands alone. Traditionally these by-products are used as feedstuffs for farm animals.
The by-products have a high feeding value and contain mainly protein, carbohydrates and minerals. Examples of these products are spent grains from breweries, sugar beet pulp from the sugar industry and wheat starch from companies that produce glucose from wheat. In most cases the by-products exit the production process in wet form and are distributed to farms by specialist feed companies. Liquid by-products are mostly fed to pigs, because the farms are equipped with liquid feeding systems with specialist storage and piping facilities. Stackable products are primarily fed to dairy cows and cattle. Products can be preserved by ensiling when they reach the farms. The main advantage of keeping the by-products in a high moisture form (20-60% dry matter) is to save on high drying costs. On the other hand, the farms must be relatively close to the factory (<300 km). If further away transport costs get too high and drying becomes more viable. Because wet products are susceptible to mould, yeast and bacterial growth preservation is critical.
Bioethanol by-products
Over the past few years an important product group has been introduced to this moist feedstuff market: bioethanol by-products. This is due to developments in the biofuel market: stimulated by the EU and governments the production of bioethanol and biodiesel has grown rapidly as a CO2 neutral alternative to fossil fuels. The European Union started with the first Biofuel Directive in 2003. This Directive sets indicative targets to promote the use of renewable fuels by replacing a percentage of gasoline or diesel with biofuels (bioethanol or biodiesel) in the transport sector. The target was set by energy content at 2% for 2005 and at 5.75% for 2010. In the EU bioethanol is predominantly produced from wheat and to a lesser extent from maize or other cereals. The main wet by-products from the bioethanol process include: condensed distillers solubles (CDS) and grains (see figure 1). When mixed and dried they are called dried distillers grains and solubles (DDGS). However, in regions where pig and dairy farms are relatively nearby, it is more economical to use them in wet form.
Fighting mould, yeast and bacteria
The safety and integrity of stored by-products in the grain processing industry is very important to food and feed supply. Microbial and mould contamination in particular are related to a loss of dry matter and valuable nutrients. Furthermore, it can cause the formation of mycotoxins which can seriously affect metabolic processes and consequently the performance and health of farm animals.
In some cases the products can be preserved by natural fermentation. In this case, lactobacilli produce lactic acid, which causes a drop in the pH ensuring microbiologically stability of the product. However, in other cases good preservation can be achieved by adding mixtures of organic acids and their salts. These mixtures also induce a lowering of the pH and also have specific anti-mould, anti-yeast and antibacterial properties, which also lead to a stable product. Every by-product has its own specific properties that require tailor made mixtures to be added for preservation.
ProSid® FL
Perstorp has been manufacturing and developing additives for preservation of wet feedstuffs for almost 50 years. The company has extensive experience in preserving by-products from the grain processing industry. Perstorp has developed a test procedure in which the products can be tested for their ability to stop mould and yeast growth by using a combination of mainly propionic and/or formic acid. This unique method is based on the production of CO2 by microorganisms that grow in the by-products. This test and several others have been carried out over the years resulting in a wide range of highly effective mould and yeast inhibitors especially for the preservation of by-products called ProSid® FL.
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