PET Food Processing - June 2020 - 26

INGREDIENTS

containing polyunsaturated fatty acids are very unstable
and highly prone to oxidation. This includes ingredients
such as Omega-3 fatty acids, whole grains and nuts.
"Oxidation is a hot topic in the pet food industry,"
said Robb Caseria, managing director,  Videka LLC,
Kalamazoo, Mich. "Finding the antioxidant system that
will preserve a pet food's sensorial and nutritional properties throughout its shelf life is often a headache for pet
food manufacturers."

Auto-oxidation - a chain reaction 

The two
primary roles of
antioxidants in pet
foods and treats
are protecting
product quality
and supporting
animal health.
Corbion

26

is when they develop objectionable flavors and odors.
There's no way to prevent it completely, only to slow it,
and there's no recovery.
Fats degrade when fatty acids react with air, moisture
or other compounds and break down into free fatty acids and other unstable compounds. Oxidative rancidity,
also known as auto-oxidation, occurs in the presence of
oxygen. Thus, the first step for delaying the inevitable is
proper packaging and sealing.  
Hydrolytic rancidity, also called hydrolysis or enzymatic oxidation, occurs in the presence of moisture
and the absence of air. This normally is accomplished
through enzymatic peroxidation, where enzymes found
naturally in plant oils and animal fats catalyze reactions
between water and oil.  
A third type of fat degradation is microbial rancidity which occurs when enzymes from bacteria, mold
or yeast break down the fat. Such excessive microbial
growth usually visually renders the food inedible.
Higher temperatures, light, water, metal ions and
biological catalysts may accelerate reactions. The presence and placement of unsaturated fatty acids on the
fat molecule also influences the rate of degradation.
Thus, fat selection comes into play when taking steps to
delay degradation. 
In general, the more polyunsaturated fatty acids on a
fat molecule, the faster it will go rancid. This is due to
the unstable double bonds that participate in the various
degradation processes. Antioxidant systems containing
different combinations of natural phenols, vitamins and
organic acids may prevent or slow oxidation.
Fat degradation is an issue in all types of pet foods, with
longer shelf life products such as dried kibble and jerkystyle snacks being the most affected. But it is not just the
inherent fat in meat, or the bulk oils added to recipes
that may go rancid; specialty, better-for-pet ingredients

Auto-oxidation occurs in three stages, with the first
being the initiation. It is here where molecular oxygen
combines with unsaturated fatty acids, producing hydroperoxides and peroxyl free radicals, both of which
are highly reactive and unstable. The second stage is
called propagation and occurs when these unstable byproducts of the first stage react with other lipids. This
starts a chain reaction, with the reaction supplying its
own accelerant.  
At this point there is no turning back for the fat, as
it is in a continuous cyclical oxidative degradation process that will only end upon the final stage, which is
aptly known as termination. This can occur when the
free radicals become highly concentrated and begin to
react together, and by doing so, stop further reactions.

"Finding the antioxidant
system that will preserve
a pet food's sensorial and
nutritional properties
throughout its shelf life is
often a headache for pet
food manufacturers."
Robb Caseria, Videka LLC
Termination can also occur when reactions yield
unreactive compounds, thus preventing further propagation. Reactions will also cease when an antioxidant
enters the scenario. But at this point, any degradation
that has already occurred is permanent. The fat cannot
repair itself.
If objectionable flavors and odors have developed,
they will remain. Initial rancid notes come from the secondary products produced during the initiation stage of
auto-oxidation. When the peroxides eventually break
down, they decompose into various aldehydes, ketones

PET FOOD PROCESSING | June 2020 | www.petfoodprocessing.net

PFP_Jun20.indb 26

5/15/2020 3:05:21 PM


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PET Food Processing - June 2020

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