Accelerated oxidation tests – the RapidOxy method

The oxidation process that affects the compounds present in foods for animal nutrition alter their qualities, both organoleptic and nutritional, producing a decrease in the useful life of the final product.

The ingredients most sensitive to oxidation are those that contain double bonds, such as fats, oils and other essential nutrients (fatty acids, vitamins, carotenoids, etc.).

The oxidation and consequent formation of free radicals in the oxidation process cause a reduction of the nutritive value of the feed and its ingredients, but also produces a decrease in the immunity of the animals and, consequently, augments the appearance of diseases and increases in mortality.

A high intake of feed with a high content of oxidized lipids and polyunsaturated fatty acids, as well as pro-oxidant components, contribute to the in vivo oxidation of animals and the post-mortem oxidation of meat (Morrissey et al., 1998 or Stem et al., 2008).

This is very important, since lipid oxidation and the consequent oxidative rancidity are one of the main causes of food spoilage forhuman consumption, along with microbial development.

Therefore, the methods that determine the oxidative stability (resistance of a sample to oxidation) are very important, particularly when evaluating the effectiveness of antioxidants to delay the oxidation of these products in animal feed, these being used to investigate the useful life of the product and also in the assurance and quality control during the development and subsequent launch of the product.

In this post, we work with several accelerated oxidation methods (Rancimat method, Schaal method) of which we have already discussed in previous articles, however today we are going to focus on another method of accelerated oxidation: the RapidOxy method.

RapidOxy is an accelerated oxidation test that corresponds to the methods of oxygen absorption, which in recent years has become more relevant, especially in the animal nutrition industry, although it is also used in other industries such as food or cosmetics .

RapiOxy is based on the increase of oxygen pressure and temperature inside a sealed chamber, allowing us to determine the oxidative stability of the samples studied. It is carried out in oxygen pumps or special devices and the decrease in oxygen pressure is generally measured as a function of the time elapsed. The samples are subjected to a certain pressure with oxygen while their temperature rises, usually up to 200º C. The temperature remains constant, while the pressure is measured continuously until a definite drop in pressure is detected. Oxidation stability characterizes the resistance of the sample against oxygen.

With this accelerated oxidation method, only a small sample is needed to get accurate results in short periods of time, and without having to prepare the samples in advance. It is a very useful procedure for investigations on useful life, quality control of the raw materials and during the development of the products.

RapidOxy accelerated oxidation method procedure

  • The sample is deposited in a small sealed test chamber, where it is subjected to a pressure with pure oxygen of up to 700 kPa, while raising its temperature to 200 ° C.
  • The temperature is kept constant and the pressure is measured continuously until a defined pressure drop is detected.
  • The result is indicated as the induction period (IP) which is the time elapsed between the start of the test (when the heating of the container where the sample begins) and the point of rupture (instant where the oxidation increases rapidly, which causes a rapid oxygen consumption and therefore a defined pressure drop), which informs us of the oxidation stability of the sample tested.

Advantages of RapidOxy accelerated oxidation method

RapidOxy accelerated oxidation method has important advantages over other alternative methods:

  • It is not necessary to prepare samples and, therefore, there is no need for expensive or dangerous reagents for the extraction of fats.
  • We can work with liquid, solid and semi-solid samples. Normally, only 5 mL of sample is needed, that is, a small sample volume.
  • It is faster than other methods of accelerated oxidation, so it saves time and money.
  • Cleaning is quick and easy.
  • Your safety has been approved by the German Federal Institute for Materials Research and Testing.
  • It includes  free software that is supplied with the equipment, which allows the transfer of the results to the computer, obtaining graphs in real time which allows a quick comparison of the results.

Main uses of the RapidOxy method

  • Evaluate oxidative stability at high temperatures.
  • Predict the useful life of the product.
  • Control accelerated oxidation.
  • Detect the presence of antioxidants.
  • Control the conditions of packaging and storage.

RapidOxy applications in the animal nutrition industry:

  • Determine oxidative stability of vegetable oils and animal fats (eg. oils, lard, tallow, fish fats, etc.).
  • Determine oxidative stability of solid products (eg. compound feeds, calcium soaps, meat meals, fish meal, etc.).

Oxidation of fats affects both the feed with which the animals are fed, and the animal’s own organism and / or subsequently the quality of the products of animal origin for human consumption.

RapidOxy accelerated oxidation method is a type of assay that becomes increasingly relevant due to its multiple advantages and that can be used for a wide range of products in the animal nutrition industry.