Antioxidants from Rendered Products Studied

By Annel K. Greene, PhD, Center Director
Clemson University Animal Co-Products Research and Education Center


Preventing oxidation of rendered fats and oils is an ongoing battle waged by rendering and animal feed ingredient companies. As customers continue to request “natural” products, mixed tocopherol use has increased. However, tocopherols can be expensive and their source is based outside of the rendering industry. Clemson University researchers Dr. Vladimir Reukov and Dr. Alexey Vertegel are studying ways to use components of rendered products to isolate potent antioxidants that would allow economical antioxidants for use within the industry as well as create a new marketable antioxidant product.

The researchers have isolated a potent antioxidant agent from poultry and bovine animal by-products. Reukov’s and Vertegel’s first research goal is to improve the procedures for isolation of this valuable agent so that it can be commercially feasible on a large scale. Their second goal is to study applications of the agent in animal feeds and other potential products such as paint, caulking, and other goods that are exposed to oxidation. Their third and final goal is to determine methods of increasing usable shelf life of the agent.

Vertegel is a native of Moscow, Russia, where he obtained both his master of science and PhD degrees in chemistry from Moscow State University. He continued his studies at the University of Missouri-Rolla and Rensselaer Polytechnic Institute in Troy, NY. He is currently an assistant professor in the Department of Bioengineering at Clemson University.

Reukov is also a native of Moscow, Russia, where he studied as a graduate student of Vertegel. He obtained his master of science in materials science and his PhD in chemistry from Moscow State University. He is currently a research assistant professor in the Department of Bioengineering at Clemson University. Reukov and Vertegel are the first researchers from the field of bioengineering to join endeavors at the Clemson University Animal Co-Products Research and Education Center (ACREC).

As the animal agriculture industries continually seek to produce high-quality products, the protection of rendered fats and oils has been a significant area of research. As important components in animal feeds, rendered fats and oils are degraded by lipid auto-oxidation processes that decrease the nutritive value of animal feeds made with these lipids. In addition, auto-oxidation can affect flavor, color, odor, and texture of lipids, which can affect palatability. Certain fatty acids such as linoleic and linolenic acid contain unsaturated carbon-carbon bonds that can be unstable and very susceptible to lipid auto-oxidation.

The rendering industry utilizes antioxidants to prevent this lipid degradation; however, choices for antioxidant products are limited and the animal feed industry has had to rely on sources outside of the industry to provide such antioxidants as ethoxyquin or mixed tocopherols, which are particularly costly and can be subject to price fluctuations.

Use of vitamin C and E or tocopherols is not only expensive but is not always highly effective in protecting fats. Reukov and Vertegel report that the agent they have isolated from animal by-products is “several thousand times more efficient in eliminating free radicals than conventional antioxidants such as vitamin C.” Natural antioxidant agents that, at the time, had been derived primarily from yeasts were widely studied and patented in the early 1970s. However, these agents did not achieve widespread use in the food and animal feed industries primarily due to the high price of their natural isolation sources.

Reukov and Vertegel have developed an inexpensive method for isolation of antioxidants from animal by-products. Poor stability of natural source antioxidant agents from yeasts was another problem that prevented their widespread industrial applications. However, the antioxidant agent derived from bovine and poultry by-products is more stable and Reukov and Vertegel believe it can be further stabilized using fatty acids to achieve an effective shelf life of three years or longer at room temperature.

In the last few decades, the search for antioxidants that could be marketed as “natural” has intensified as interest in substituting synthetic antioxidants with naturally-derived products has increased. In recent years, antioxidant protein hydrolysates and peptides have been discovered including some isolated by other ACREC researchers. In their search, Reukov and Vertegel noted that several herb-derived agents have been marketed as natural products for human dietary supplements. Using this inspiration, they began examining other potential sources for similar antioxidant agents.

A literature review of information revealed a key cellular antioxidant that is one of the most powerful antioxidants known for neutralizing oxidative radicals and the researchers realized that it is contained in the animal by-products’ raw material stream. In the animal body, this agent is a key cellular antioxidant that works as part of an important system for protecting cells and tissues from free radical damage. This agent has excellent antioxidative properties since it is an effective free radical scavenger. On the cellular level, it out-competes damaging oxidation reactions, thus protecting the cell from oxidation toxicity.

The antioxidation reaction occurs quite rapidly in the cell to protect sensitive and critical cellular targets, such as lipids present in the cell membrane. Moreover, this antioxidant has the largest reaction rate with its substrate of any known antioxidant. This reaction is only limited by the frequency of collisions between the antioxidant and its substrate. The research team postulates that this agent could be used to inhibit oxidative deterioration of animal feeds and when fed to livestock and poultry, could possibly even protect resultant meat lipids from oxidation.

In their study, Reukov and Vertegel are working on methods of producing large quantities of the antioxidative agent from rendered products. In their research laboratories, they have produced a protein concentrate with high antioxidative activity from animal by-products. However, natural raw product degradation post-mortem can reduce yields of the valuable agent so Reukov and Vertegel are now working to improve recoverability. The team has used a commercially available assay kit with standards to assay the antioxidant activity. They examined finished animal protein meals but obtained fairly low antioxidant activity. However, their results indicate very consistent and excellent recovery of the antioxidant agent from raw materials.

The final activity of antioxidant extract from raw materials was in the range of 80 to 100 units per milliliter (U/mL) after concentration. In isolation studies using raw materials prior to concentration, the activity of the antioxidant extracted from samples donated by industry suppliers was 9.64 U/mL, which was considerably lower than the researchers expected. One possible reason for such low antioxidant recovery was thought to be due to blood coagulation during collection and transport of the samples. Blood clots can capture antioxidant-containing components and prevent efficient extraction from the cells.

In using fresh materials, the researchers isolated extremely high levels using their extraction technique. The antioxidant yield could therefore be increased if antioxidant isolation is performed on-site or if anticoagulants are added to raw materials during storage and transport. The researchers are currently developing an improved extraction protocol to produce concentrates with higher antioxidant activity.

The results obtained thus far are very promising and indicate great potential for commercially isolating one of the most potent antioxidants known from animal by-products. Reukov and Vertegel will examine the effectiveness of the agent in protecting animal by-products and animal feeds and compare its efficacy to other commercially available antioxidants such as tocopherol.

In future studies, the team will work to examine ways to improve shelf life of the antioxidant agent to improve marketability. Other research on the antioxidant agent could include examining effectiveness of the product for protecting other items such as paints and plastics. If effective, the isolation of this antioxidant agent from rendered animal by-products could not only allow the industry to produce its own antioxidant agents and, therefore, have significant cost savings, but uses in other products may open new markets for the rendering industry.

This research project was supported by funding from the Poultry Protein and Fat Council through the Fats and Proteins Research Foundation support to ACREC.


ACREC Solutions – February 2011 RENDER | back