As a vital component within the feed production chain, water not only acts as a hygiene enhancer in the form of steam, but it is also an important nutrient and lubricant. In contrast, water provides a perfect environment for microorganisms to grow, impacting feed quality and threatening animal performance. How to achieve that delicate and important objective of balancing feed’s ideal moisture level and quality?
Two important components that have a significant impact on moisture and quality are water activity and surface tension. Get these two attributes in order and the results can be extraordinary. Below, we will describe the 3 most impacted parameters related to water activity and surface tension:
1. Improving overall feed quality and shelf life
2. Increasing feed mill efficiency and throughput
3. Increasing final moisture content in finished feed
PARAMETER 1: IMPROVING OVERALL FEED QUALITY AND SHELF-LIFE
Adding water during feed processing poses several threats. Beyond increasing moisture content, added water also raises water activity. A high water activity means that free water is available for microorganisms to grow and consume valuable nutrients. Feed ingredients that are high in water activity will impact ingredients with low water activity, as the moisture will balance out throughout the feed, potentially affecting attributes such as texture, durability, and palatability.
Water activity is not the only aspect that must be managed when it comes to moisture. For example, some fungi can grow and proliferate in very low water activity and cause spoilage and reduce shelf-life, while consuming valuable nutrients and affecting palatability. Moulds like aspergillum, fusarium and penicillium are known to generate mycotoxins, which can further harm animal health and performance. Prevention and elimination of fungi with specific blends of organic acids is therefore essential, even in feeds with a low water activity.
Water’s surface tension becomes an important parameter to consider in order to ensure a long-lasting effect and deep penetration of water and organic acids throughout the particle. As surface particles of the liquid attract each other, a so-called ‘film’ is formed. This ‘film’, or ‘tension’ makes the water drop pull together. This effect creates the tension that allows insects to walk on water without sinking. And this is also the very property that creates a challenge for feed production.
Water has a relatively high surface tension which makes it difficult for feed particles to absorb it. Also, as the droplet size is quite large, dispersion and spreading of the water can be challenging. Therefore, applying an emulsifier to the water before mixing with the feed can be a first step to improve absorption. Specific emulsifiers can reduce surface tension, resulting in smaller droplets and better absorption within the feed. Including a mixture of specific organic acids, together with an emulsifier provides an even higher benefit as it not only creates a more even spread of the liquid, it also enables the organic acids to penetrate deeper and have a higher effect in reducing harmful microbes. In a benchmark study it became evident that Fylax Forte-HC liquid, a product within Trouw Nutrition’s feed additive brand Selko, had the highest impact on surface tension (Figure 1).
Fylax Forte-HC liquid contains ActiProp, a patent-pending technology incorporating a synergistic effect of organic acids, buffering agent, emulsifier, and phytochemicals. Applying process moisture management that consists of dedicated dosing equipment applying a hydrated solution of water and Fylax Forte-HC liquid can decrease process loss, improve throughput pace, and support pellet durability and quality. At the same time, it can provide energy savings and safeguard shelf-life.
PARAMETER 2: MILLING EFFICIENCY AND THROUGHPUT
Heat treatment during pre-conditioning is a vital part of the production process in most feed processing facilities. Besides recovering moisture that is lost during grinding, conditioning helps to reduce harmful pathogens, such as Salmonella and E.coli and causes starch to break down and become gel-like: starch gelatinization.
The high surface tension of water impacts thermal (heat) conductivity of feed particles during pre-conditioning. When surface tension is decreased, the improved wettability (absorption) of feedstuffs can provide valuable improvements within the feed manufacturing process.
As heat is conducted via water, a deeper penetration will automatically improve the heat conductivity of the feed. Therefore, reducing the surface tension not only causes a better dispersion, it also increases the ability to transport heat via steam to the inner part of feed particles. This combined effect can improve starch gelatinization and reduce microbial growth. Figure 2 shows thermal conductivity increases as moisture content goes up.
The abovementioned figure would imply that simply increasing water would be sufficient. However, in practice, increasing animal feed’s moisture level is always subject to limitations. Raising the amount of moisture may lead to nutrient dilution, choking of the pellet mill and increasing the risk of microbial growth.
Depending on the type of raw material, starch starts to gelatinize when certain temperatures are reached. Proper gelatinization benefits the pelleting and extrusion process as it acts as a lubricant, which will make mash pass through the pellet mill with less friction and energy. Less friction means lower energy consumption and higher throughput. Such production efficiency can reduce production cost, and wear and tear on equipment. Finally, feed particles also tend to stick together better, causing less breakage and reducing fine particles in the final product.
PARAMETER 3: INCREASING FINAL MOISTURE CONTENT IN FINISHED FEED
Moisture levels can fluctuate dramatically during various stages of feed processing (Figure 3). Different ingredients contain different moisture levels to begin with. As particle size is reduced and different ingredients are mixed, water activity causes moisture to disperse evenly throughout the mixture. However, the lack of an emulsifier will keep most of the moisture on the outer layers of the particles. Grinding of raw materials contributes greatly to moisture reduction due to evaporation.
The loss of moisture is usually compensated during the conditioning step through the addition of steam. However, high temperatures also cause evaporation during cooling. A commonly used solution is to add water, along with steam, to compensate for evaporation. This process is not free of risks free water within the feed particles can remain on the surface of the final product, creating favourable conditions for moulds and other microorganisms to take advantage.
Deeper penetration and binding of moisture within the feed particles is imperative, given the threats moisture poses if it remains on the outer area. Applying a hydrated solution of water with specific blends of buffered and non-buffered organic acids and emulsifiers is key to utilize moisture at the highest possible efficacy. Figure 3 shows how increasing the amount of water added to 3% along with an emulsifier may even support a process gain in moisture – especially in dry environments.
CONSISTENCY IS KEY – AN INTEGRATED APPROACH
In conclusion, water activity and surface tension are important factors to control as they can have a tremendous effect on overall feed quality, safety, and shelf-life. Local conditions and needs differ for each feed mill, whether it is producing mash feed, pellet feed or extruded feed. Besides the controlled production conditions, there are many additional factors beyond our control that affect moisture and quality. Factors like climate, material availability and quality upon arrival affect needs and demands for proper process management.
Application of products in a hydrated solution can be challenging to get exactly right. To help feed producers, Selko Feed Additives created its Feed Processing & Quality programme. This solution offers an integrated approach of knowledge, services, and products to arrive at an ideal solution based on the individual feed production situation. One important component within the service package is the installation of dosing equipment solutions that enable application of a hydrated solution to be fully automated and integrated on the feed production lines.
Specifically designed for full-automatic and in-line optimization of moisture levels, Selko created the Moisture Management System. This complementary dosing service uses microwave sensor technology to measure moisture levels during production and automatically adjusts inclusion rates of hydrated solutions without the need for human intervention. The system was recently enhanced with the addition of remote access and data logging capabilities. This cloud-based solution enables feed millers to significantly reduce the time needed between diagnosing an issue and solving it. Additionally, it increases the support level of dedicated engineers by deploying the ‘fix on first visit’ principle.
Considering the three parameters described above can help feed mills leverage the power of water to support safe, efficient production of high-quality animal feed.
About Prince Nanda
Dr. Prince Nanda is Global Programme Manager of Selko’s Feed Processing and Quality programme. He is a Doctor of Veterinary Medicine & Animal Husbandry with a master’s degree in Agricultural Business Management from India. During his professional career he obtained a certificate in feed mill management from Kasetsart University in Thailand, as well as gaining thorough knowledge on feed shelf-life extension, Salmonella control and moisture management at various large feed additive and grain handling companies.