About 95% of dry pet food is made by a process called extrusion. A study by Wageningen University in the Netherlands shows that drying pet food between 160°C to 180°C can significantly reduce its nutritional value.
Sometimes temperatures can even reach 200°C during commercial pet food manufacturing. The high temperatures cause radical changes to the ingredients.
Here are the consequences high temperatures have on pet food:
1. Vitamins are damaged
Most vitamins are sensitive to heat and water. Extrusion involves high temperatures. Vitamins A, C, E and the B-group vitamins are either destroyed or heavily decreased by the extrusion process.
These vitamins are crucial for your pet’s health. Vitamin A is important for cell growth and healthy skin and coat for dogs and cats. It’s essential for cats’ night vision as well.
Pet food brands include a long list of synthetic vitamins to make up for the loss during the heating process.
Unfortunately, the pet food industry is not regulated by the same standards as the human food industry. Pet food therefore might include vitamins from lower grade sources with a poor absorption rate.
Several studies show that nutrients are most potent when they come from the food itself compared to supplements.
2. Decreased level of antioxidants – omega three and six
The level of antioxidants decreases during high temperatures. Antioxidants play a major role in your pet’s health since they inhibit oxidation, a chemical reaction that can produce free radicals.
These free radicals attack cell membranes, proteins and DNA, but are stopped by antioxidants.
Studies find that older dogs are less likely to suffer from age-related behavioural changes associated with cognitive decline when they eat a diet rich in anti-oxidants.
Dogs on a diet rich in anti-oxidants recognise their family members more easily compared to the control group. Antioxidants also help dogs and cats with allergy or skin and coat issues.
High temperatures decrease the level of omega three and six and increase the concentration of oleic acids (omega nine monounsaturated) and other potentially toxic compounds.
3. Starch gelatinisation
Commercial pet food manufacturing requires enormous amounts of carbohydrate or starch to bind the kibble together.
This is partially because the machines pet food companies use were originally invented to produce cereal, and therefore can’t include large amounts of fresh ingredients. Without the large amount of starch, it’s impossible to shape and hold the kibble together.
During the extrusion process, the high heat melts and gelatinises the starch. This helps form the kibble and causes an expansion of the product.
Typically, the amount of starch in dog food is 40% and in cat food 30%. However some brands include twice that amount.
The starch mainly comes from cereal grains, which are not biologically appropriate nutrition for either dogs or cats. Large amounts of starch can cause blood-sugar spikes after your pet eats the meal.
For example extruded rice can cause higher glucose and insulin response compared to other starches like barley, corn and wheat. This is worth to consider if your pet struggles with diabetes.
4. Structural change in proteins
High heat changes the molecular structure of a protein, called denaturation. It involves the breaking of weak bonds within a protein.
These bonds are responsible for the protein’s highly ordered structure. Denatured proteins have a looser, more random structure.
Once a protein is denatured there’s no going back. Think of it like scrambled eggs – once scrambled you can’t unscramble it.
How denaturation works in dry pet food
The protein source in dry pet food is often a combination of animal and vegetable protein. In most cases, it’s much cheaper for companies to include protein from plant sources than use large portions of meat.
This raises the overall protein level of the food but has a much lower digestibility than meat protein. Denaturation helps this pet food to become more digestible.
The opposite scenario happens when a high-quality protein source is used. Denaturation makes it less digestible. These changes in protein structure can result in food allergies.
There’s a risk that your pet’s immune system may not recognise the new protein structure and treat it as a foreign invader.
That explains why some pets have an allergy to a particular meat-based dry food but have no problem eating the same meat in its whole, raw form.
Denaturation can cause off-flavours, so some companies apply a great deal of additives to give their dry food a better flavour.
Pet parents are seeking alternatives
Loss of vitamins, decreased level of antioxidants, omega three and six, starch gelatinisation and structural change in protein are some of the things that happen when pet food is exposed to high temperatures.
This is one of the main reasons many pet parents are switching from kibble to a minimally processed diet like raw, home-cooked, freeze-dried or air-dried food.
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