Moisture optimization: How to safeguard feed quality and feed mill efficiency

In this article, we look at how the right choice of processing aid is key to sustainably boosting feed mill efficiency. A concerted focus on moisture management when preconditioning the mash feed prior to pelleting allows feed producers to reap both economic and feed quality benefits. Optimal moisture levels safeguard feed quality and support feed mill efficiency issues. SURF•ACE’s surfactant and preservative ingredients optimize moisture absorption and retention.

Sabria Regragui Mazili
EW Nutrition

In light of climatic challenges, variability in raw material quality, and technical constraints, it can be challenging for feed producers to optimize the water content in compound feed. In combination with high temperatures, too much moisture in feed can favor the growth of molds. Molds spoil feed by depleting energy and nutrients and rendering the feed unpalatable. Even worse, some molds release toxins harm animals’ health and performance. On the other hand, too little moisture in feed has a negative impact on pellet durability, increasing the level of fines, process loss, and energy consumption while decreasing press yield (Moritz et al., 2002).

In this article, we look at how the right choice of processing aid is key to sustainably boosting feed mill efficiency. A concerted focus on moisture management when preconditioning the mash feed prior to pelleting allows feed producers to reap both economic and feed quality benefits.

WHY MOISTURE MANAGEMENT REQUIRES BOTH SURFACTANTS AND ORGANIC ACIDS
Moisture management starts with monitoring certain indicators. The moisture content measures the total amount of water contained in a substance, usually expressed as a percentage of the total weight. Feed producers track the moisture contents of raw materials, mash feed, and pellets during all processing stages to optimize quality, yields, and profitability.

For the purpose of preventing mold growth, however, the critical indicator is water activity (aw). Simply put, microorganisms, such as bacteria, yeasts, and molds, will usually not grow below a certain water activity level, and the higher the water activity, the higher the chance of microbial growth (Roos, 2003). Water activity is technically defined as the ratio of partial vapor pressure of water in a substance to the partial vapor pressure of pure water under the same temperature and pressure conditions. What this describes is what proportion of water molecules are not chained to chemical groups in the feed itself, and, therefore, available to support microbial growth. This will affect the safety and quality of food and feed.

The following table lists the water activity levels at which common feed-contaminating fungi start to grow and produce mycotoxins, which severely damage animal production worldwide.

CAN WE CONDITION FEED WITH PURE WATER?
The intense friction during grinding and mixing results in heat; subsequently, moisture from the mash feed is lost in the form of vapor. As moisture is critical to ensure production output and feed quality, it must be added back to the system. If the levels are too low, the pelleting process will be ineffective regarding the final quality and also the cost of production, due to higher energy consumption. However, simply adding water does not work well: Pure water does not readily bind to the feed; it effectively “sits on top” of the feed surface, increases the feed’s water activity, and thus becomes a perfect substrate for microbial growth. Plus, pure water largely evaporates again when the feed is cooled and this can cause weight losses in the finished feed.

SURFACTANTS
Hence, at the conditioning phase, it is critical to add surfactants to the hydrating solution. Surfactants change the way water behaves: by reducing the surface tension of water, they enable the feed particles to absorb the water and ensure that it is evenly distributed throughout the feed. Improved moisture retention can:
• Facilitate the starch gelatinization during conditioning (important making the pellet more durable and the feed more digestible),
• Minimize feed shrinkage at the cooling stage,
• Reduce friction and hence the energy required for the pellet die (improving milling efficiency), and
• Curb microbial growth by reducing water activity.

ORGANIC ACIDS
While surfactants contribute to mold control, feed producers also require the help of organic acids. The objectives are to optimize the moisture content in feed and to prevent mold (re)contamination hazards along the production lines.

Let us consider how the most effective one, propionic acid, works: In its non-dissociated state, propionic acid has all its hydrogen ions attached to the molecule. Once it enters a mold cell, the propionic acid dissociates, meaning the hydrogen ions separate from the molecule. They reduce the intracellular pH in the mold cell and inhibit its metabolic pathways, ultimately leading to cell death (Smith et al., 1983).

Common feed ingredients such as soybean meal, maize, wheat, barley, and dehulled oats are often stored for several months. Given variable and likely challenging temperature, oxygen, and moisture conditions, their water activity levels can easily escalate (Mannaa and Kim, 2017) – rendering the long-lasting anti-fungal activity of targeted organic acid even more important.

SURF•ACE: IMPROVE MILL PERFORMANCE AND PELLET QUALITY
A synergistic blend of organic acids and surfactants helps to achieve the objective of adding moisture without risking either the subsequent loss of moisture during cooling or the development of mold. This is the working principle behind SURF•ACETM feed mill processing aid, carefully formulated to best achieve the objective of ensuring feed quality and increasing production efficiency. Achieving this objective means that feedstuff resources are optimally used and energy requirements decrease – both of which supports the feed industry’s environmental “footprint”.

IMPROVED PRESS YIELD
The effect of adding SURF•ACE to diets with increasing levels of fat was evaluated at more than 40 feed mills, with production capacities ranging from 5 to 20 tons per hour, under identical electricity consumption conditions. SURF•ACE is added to water, and this hydrating solution lubricates the mash feed, managing to reduce friction in the dies prior to the actual pelleting. The results show that the addition of SURF•ACE during the conditioning stage increases press throughout (t/h), relative to pure water conditioning, by between 9 and 23 %, depending on how much preconditioning solution is applied and the level of fat in the diet:

Addition of SURF•ACE increases press throughput
*Including large volumes of hydrating solution in high-fat diets might adversely affect the durability values of the feed

What is the role of fat in this scenario? Dietary fat acts as a lubricant between the feed and the pellet die, reducing the pressure within the die. The higher the percentage of fat included in the mixer, the lower the energy required to process the mash (Pope, Brake, und Fahrenholz, 2018). The surfactants contained in SURF•ACE have an emulsifying effect; they help bind water to the fat element of the feed. The emulsion of water and fat “behaves” like fat, improving the lubrication of the press and generating a higher throughput for the same electricity consumption.

HIGHER PELLET QUALITY
Significantly, adding SURF•ACE does not negatively affect pellet durability, a common issue in high-fat diets (Moritz et al., 2003). On the contrary, it enhances pellet durability as more crystal starch becomes gelatinized. This translates into improved results for Holmen pellet durability testing:

Addition of SURF•ACE improves pellet durability

Pellets need to withstand significant pneumatic handling, for example, during bagging and transport and in the feed lines. The Holmen pellet tester (the industry standard for evaluating pellet durability) simulates this handling and calculates the percentage of fine generated, expressed as a pellet durability index (PDI). Across six different poultry compound feed types, SURF•ACE improves pellet quality and thus the PDI. Fewer fines equate to less reprocessing for feed producers and higher palatability for animals.

THE NEXT LEVEL IN COMPOUND FEED PRODUCTION
Achieving optimal moisture levels in compound feed is a complex balancing act involving technical constraints, raw material variability, microbial challenges, and the price pressures of competitive feed markets. Feed mills generally operate within a particular comfort zone, a throughput and quality level at which they minimize production problems. Thanks to its dual surfactant and preservative effects, SURF•ACE feed mill processing aid expands the comfort zone in two dimensions: From an economic point of view, the improved lubrication gives mills the choice of either pushing their performance levels closer to their equipment’s potential capacity or achieving the same results at lower electricity use. From a feed quality angle, effective mold prevention and improved pellet quality allow for safer, more palatable feed – and from there, we come full circle to safe, nutritious food for all of us.

References
• Magan, Naresh, David Aldred, and Vicente Sanchis. “The Role of Spoilage Fungi in Seed Deterioration.” Essay. In Fungal Biotechnology in Agricultural, Food, and Environmental Applications, edited by Dilip K. Arora, 311–23. New York: Marcel Dekker, 2004.
• Mannaa, Mohamed, and Ki Deok Kim. “Influence of Temperature and Water Activity on Deleterious Fungi and Mycotoxin Production during Grain Storage.” Mycobiology 45, no. 4 (2017): 240–54. https://doi.org/10.5941/myco.2017.45.4.240.
• Moritz, J. S., K. J. Wilson, K. R. Cramer, R. S. Beyer, L. J. McKinney, W. B. Cavalcanti, and X. Mo. “Effect of Formulation Density, Moisture, and Surfactant on Feed Manufacturing, Pellet Quality, and Broiler Performance.” Journal of Applied Poultry Research 11, no. 2 (2002): 155–63. https://doi.org/10.1093/japr/11.2.155.
• Moritz, J. S., K. R. Cramer, K. J. Wilson, and R. S. Beyer. “Feed Manufacture and Feeding of Rations with Graded Levels of Added Moisture Formulated to Different Energy Densities.” Journal of Applied Poultry Research 12, no. 3 (October 1, 2003): 371–81. https://doi.org/10.1093/japr/12.3.371.
• Pope, J. T., J. Brake, and A. C. Fahrenholz. “Post-Pellet Liquid Application Fat Disproportionately Coats Fines and Affects Mixed-Sex Broiler Live Performance from 16 to 42 d of Age.” Journal of Applied Poultry Research 27, no. 1 (March 1, 2018): 124–31. https://doi.org/10.3382/japr/pfx054.
• Roos, Y. H. “WATER ACTIVITY | Effect on Food Stability.” Essay. In Encyclopedia of Food Sciences and Nutrition Second Edition, edited by Luiz Trugo and Paul M. Finglas, 6094–6101. Cambridge, MA: Academic Press, 2003.
• Smith, Philip A., Talmadge S. Nelson, Linda K. Kirby, Zelpha B. Johnson, and Joseph N. Beasley. “Influence of Temperature, Moisture, and Propionic Acid on Mold Growth and Toxin Production on Corn.” Poultry Science 62, no. 3 (1983): 419–23. https://doi.org/10.3382/ps.0620419.

About Sabria Regragui Mazili
A social scientist by training, Sabria Regragui Mazili has worked as a communications consultant in Berlin, Brussels, and London before joining EW Nutrition in 2019. As a science editor, she covers topics ranging from animal health to sustainability. Sabria is passionate about collaborating with technical experts and making complex issues understandable for everyone.