Beyond The Antioxidant: Rancidity as the Tip Of the Iceberg

The natural reaction to detecting complaints is to increase the amount of antioxidants in the product. However, the traceability system becomes extremely important as a source of information, knowledge about the production process, and product handling until it reaches the final customer.

Raw Materials: The Starting Point

Controlling the raw materials used is the critical point of the process and where we can most effectively prevent oxidation problems.

Working with dependable suppliers is key, but not always enough. We need to understand the conditions under which we receive raw materials, and that can be achieved through tests.

In raw materials with a higher fat content, there are three main tests that allow us to understand where they are in the oxidation process:
 

• Acid number: It is one of the first tests that is generally available and measures the amount of free fatty acids. Its result provides information on the state of degradation, mainly associated with poor conservation conditions. 
   
  
• Peroxide value: Its value introduces us to the oxidation process, since it will measure the peroxides that are formed in the initial stages, and which indicate whether such oxidation is beginning. It is key to understand that these are unstable compounds, so depending on what stage of the process they are in, they can be low or high. For this reason, the result should be related to the acid number.
   
• Anisidine value: It indicates the advanced stages of oxidation when secondary compounds associated with the characteristic smell and taste of rancidity are already present.
   

The test results allow us to make decisions based on the information and reference values. It is important to understand that a raw material that enters an initiated state of oxidation is already undergoing an irreversible process.

The Production Process: The Biggest Consumer of Antioxidants

Each stage involving temperature, humidity, oxygen, light, or metals is a point where oxidation can be triggered and start progressing, causing the antioxidants present to be consumed. The purpose of antioxidants at this stage is to provide time and help the mixture to proceed without triggering the oxidation process. Knowing what those critical points are in each plant is essential to designing an effective protection strategy.

The grinding and mixing process is where all the raw materials come together, including vitamins and minerals. Some vitamins can function as pro-oxidants and in the case of minerals, such as iron or copper, they are metals that function as catalysts. This is one of the important points for applying antioxidants.

Extrusion is undoubtedly the most critical point: temperatures above 120°C, high pressure, and humidity make it the stage with the highest antioxidant consumption in the process. 

However, there are still stages that subject the product to elevated temperatures, such as drying, and to large airflows, such as cooling. In this final stage, although temperature is no longer the determining factor, prolonged and continuous exposure to air creates favourable conditions for oxidation, making it one of the most underestimated stages of the process.

The second point of application to reinforce the antioxidant is usually in the coating process. Fats added to provide palatability and/or coating can be used as vehicles for the antioxidant that will provide protection to the extruded food particles.

Finally, the packaging must ensure a barrier against moisture, air, and light throughout the product's shelf life. However, even with a well-controlled process, the product can be compromised if it is not carefully managed once it leaves the plant.

Storage and Distribution: The Most Difficult Link to Control

Temperature, humidity, and sun exposure during storage and transport can trigger the oxidation process significantly, especially in certain climates with a wide temperature range or extremely elevated temperatures. The FIFO (First In, First Out) system then becomes an essential tool that must be applied in all stages of the chain, from the plant to the end customers. Incorrect stock rotation is a frequent cause of complaints that are initially assumed to be formulation problems.

Training should be provided to distributors and points of sale, acknowledging that this is also part of the stability management strategy.

Finally, there is one more point: whether the policies and controls are properly applied, and that is achieved through evidence.

Finished Product Monitoring – It is Not Enough to Control, You Must Also Validate

Monitoring the finished product serves a dual purpose: it is used not only as quality control, but also as a system validation tool. Tests of acidity, peroxides, anisidine, and antioxidant residues, as well as sensory evaluations, will allow us to track the evolution of the parameters over time.

Stability studies will allow us to verify whether the adopted antioxidant strategy is effective and whether the product will reach its expected shelf life. Real-time studies reflect actual storage conditions and are the most representative, but they demand the entire shelf life to obtain results. Accelerated studies, on the other hand, allow for an early projection by subjecting the product to controlled conditions to accelerate its degradation, which is extremely useful in development stages or when facing formulation changes. These types of studies strengthen the validation of the system and can be used to support any decision regarding dosage, application points, or process conditions.

If the monitoring system is well designed, it will allow us to detect deviations early and make the necessary adjustments before they reach the consumer.

Conclusion

Rancidity problems cannot be analysed in isolation, as they are multifactorial problems that require a view of the entire system. It is important to know our raw materials, control our process, and make decisions based on supporting information. The goal is to move from reacting to anticipating, and the challenge is no longer choosing the best antioxidant, but designing a reliable system that always supports it.

By Eng. Mariana Piecenti, Process & Quality Advisor at BBR Industries
Source: All Pet Food