Pet
Food
Review

Antioxidants - Good Cops or Bad Cops

Stopping rancidity | Natural alternatives | Packaging considerations | Conclusions

Can you think of making a baked product containing between 10 - 20% fat which you place into a paper sack and leave around for 12 months at room temperature AND expect it to be edible at the end of that time period?

I guess the answer is 'No!' because the food would have gone rancid by that time. That's why you need preservatives/antioxidants to stop that rancidity or at least slow it down. Fat that has gone rancid (that slight well-used cooking oil smell you sometimes notice when you're picking up your fries from the chip shop) produces ketones and aldehydes which are not particularly good for health!

ALL dried pet foods need antioxidants/preservatives to stop the food going off before the Best Before Date.

If your pet food does not list any antioxidants used, then ask why they're not being totally open about their ingredient declaration.

Why does dry pet food need antioxidants?

Any product which contains fat, and which has contact with the air stands a good chance of 'going off' after a while, as the oxygen reacts with the fat molecules - this process is called oxidation, or we tend to think of it as fat going rancid. (Canned dog food is protected from oxidation by its airtight storage)

RANCIDITY is the oxidation(decomposition) primarily of unsaturated fatty acids(containing one or more bonds, such as oleic, linoleic, and arachidonic acids) resulting in disagreeable flavors and odors in fats and oils (stale chip fat smell). This occurs slowly and spontaneously and may be accelerated by light, heat and certain minerals. Once the reaction is initiated, it becomes autocatalytic (i.e. it just keeps on going!) and proceeds unabated until the reactants are completely exhausted.

Oxidation of the fat decreases the nutritional quality of the food, makes it less palatable to the pet, and can even make it unsafe to eat (Oxidation of unsaturated fatty acids yields ketones and free fatty acids that are usually unpalatable and potentially injurious. It takes as little as 0.05% of the fat to react with oxygen to produce rancidity.)

Since most pet food contains high level of fat and fat-soluble ingredients (including vitamins A and E), it is critical to prevent oxidation to maintain quality, nutritional value and palatability.

The meat meal and fats used in pet food are subject to a lot of processing and mechanical damage before they get to the factory (During rendering, the inherent animal cellular defense mechanisms are disrupted or destroyed), and during that process and storage they will start to deteriorate due to oxidation - they will go rancid - unless something is done to stop or slow this change from happening.

Rancidity is usually expressed as a 'Peroxide Value' or PV, and there is much debate as to what is the point at which a fat goes rancid, as you can see from the extract below:

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So how do we stop fats going rancid?

As far as the majority of the pet food industry is concerned, your pet food will be preserved with one or more different antioxidants - either natural (Vitamin E, C or Tocopherols) or not (BHA, BHT, Ethoxyquin or similar) or a mixture of both types - and the pattern will be something like this:-

'Hang on!' you might say at this point. 'Product 3 contains artificial preservatives!' And of course it does, but because the meat meal and fats were pre-treated before manufacture by the supplier, I think I'm right in saying that you don't actually have to declare them as ingredients (there's a similar rule with human food, believe it or not)

You need to know this! Some companies specify from their suppliers that fats and meat meal do not contain artificial preservatives, others do not. You may not realise this from the ingredient declaration.

Dr. Lisa Freeman, DVM writes 'The problem is that there's no legal definition of "all natural," "preservative free," or similarly named products. Manufacturers define products by what they believe these terms mean. In general, the implication is that no preservatives or artificial colors have been added and that natural preservatives, such as vitamin C or vitamin E, have been used, but this can vary from brand to brand. In addition, although these products may not contain added artificial preservatives, they may still contain low low levels of artificial preservatives that were already in the meat or fat-soluble vitamins obtained from suppliers.'

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What are the natural alternatives?

Well, I've mentioned the main ones already, ethoxyquin, butylated hydroxyanisole (BHA), Butylated hydroxytoluene (BHT) are the traditional antioxidants used. You might also see propyl-gallate and potassium sorbate used as preservatives. I asked Royal Canin, Eucanuba/Iams and Pedigree for comments on the system they use. Pedigree are happy using BHA and BHT but offer no expanation as to why they prefer these to more natural alternatives, but I got a very informative reply from Royal Canin who are very upfront about the antioxidants they use and why - full marks for a real spirit of openness. You can read Royal Canin's response here.

Hills have also responded, and although a little clarification is needed, the news for 'natural' is good. They said 'Hill's adds a Natural Preservative System to all Science Plan and Nature's Best dry products. This is to protect against fat rancidity and maintain freshness and flavour. This system consists of a blend of mixed tocopherols (natural antioxidants that are part of the vitamin E family), citric acid (a natural preservative which is synergistic with tocopherols) and rosemary extract, which also has antioxidant properties. Hill's Natural Preservative System enables us to maximise the protection of the fatty acids and fat soluble vitamins within these dry foods and maintain our aim of providing the very best quality nutrition possible.'

This Natural Preservative System will also be added to Hill's Prescription Diet dry products. Currently new, dry product introductions to this range contain the Natural Preservative System and the existing products contain a blend of the food antioxidants BHA and BHT (butylated hydroxyanisole and butylated hydroxytoluene). These synthetic antioxidants have been widely used by the manufacturers of human foods and pet foods because they are both safe and effective. They are most effective when used in combination.'

(I have responded to this by asking if Hills pre-treat their fats and meat meal naturally or with BHA/BHT (this wouldn't be obvious from the ingredient declaration) - so far no response, so I'm guessing that route 3 above is the way they follow!)

Eucanuba were a little more coy in their response 'I would like to reassure you that our Eukanuba and Iams over-the-Counter range does not contain artificial antioxidants or preservatives. The EC permitted antioxidants in our diets are natural preservatives such as Vitamin E, Rosemary Extract, Citric Acid and Lecithin.'
I might be wrong, but I'm guessing that Eucanuba follow the 'Product 3' approach, with chemically pre-treated fats and meat meal. The reply promised that my enquiry would be forwarded to their technical department - so I await further clarification.

Iams new Wellness brand declares no preservatives - so on the basis of all dried pet foods need antioxidants I'm guessing that they also use pre-treated fat and meat meal, maybe coupled with a gas-flushed bag to eliminate oxygen. But then, what happens when the consumer opens the bag? Unless of course they've discovered a miracle new way of stopping fats go rancid?

So let's look at the alternatives and, as importantly, their effects on reducing or stopping the adverse oxidation and rancidity of the product. After all, what we don't want, even if we're committed to the natural route, is a product which not only contains rancid fat but is potentially causing adverse health problems.

Incidentally, did you know that BHA and BHT are already present in a lot of human foodstuffs as well as cosmetics (particularly lipstick and mascara!!?) Read More

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The effects of packaging on rancidity

There's an added complication in that the material that the food is packed in can also have an effect on oxidation - and this obviusly has a bearing where natural antioxidants are used.

Quoting from a packaging company website (http://www.fresco.com/petfood_industry.html) they say this when looking at the differences between paper packaging and plastic barrier films:

I would guess that if oxygen could be eliminated from the bag after packing (gas flushing) then this would also be advantageous (albeit expensive) and I believe one or two companies are looking at this.

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Conclusions!

At the end of the day you have to take a balanced view on this rather emotive subject. I've tried to look at both sides of the arguement, because I know from experience that naturally preserved pet food can and sometimes does go rancid within the twelve months that usually comprises the Use By date after manufacture. This can be because of poor quality ingredients, poor storage (high temperature mainly either in warehouse or at home) or by poor distribution of the antioxidant mix during processing. Packaging also seems to play a part. The question is 'Is this rancidity potentially harmful to me pet?'

Against this, we have to balance any potential health problems associated with the long term ingestion of chemical antioxidants - even if added at recommended maximum rates.

I was also interested to see just how much of these products we eat or spread on our skin within cosmetics - these chemical antioxidants are not just used in animal feed (other than ethoxyquin)

As someone who currently feeds a naturally preserved dog food, I've given myself a lot of thinking to do!

My personal recommendations based upon what I have read over these past few days are these:

1) If you are currently buying a product which is preserved with chemical antioxidants, and are happy with that product then carry on using it.

2) If you are using or thinking of using a naturally preserved product then check the best before date before you buy. Most foods of this type are manufactured with a 12 month shelf life, but if you buy one with only 3 or 2 months left on that date how can you be sure of the conditions under which it has been stored?

Make sure there's 8 or 9 months on the shelf life, and there's less chance of problems, the food is fresher and Peroxide Values (as a measure of rancidity) will be hopefully lower. After all, why should you be offered food that has been hanging around a warehouse for 9 months or more?!

3) Food sold in a plastic bag may possibly be better protected against rancidity than that sold in paper sacks.

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Appendix to article and references

Response from Royal Canin to query about their use of artificial antioxidants/preservatives:-

'There are two categories of antioxidants:

Synthesized antioxidants: BHA (Butyl-Hydroxy-Anisole), ethoxyquine, gallates, BHT (Butyl-Hydroxy-Toluene)

Natural antioxidants: other tocopherols: extracted from vegetable oils,
alpha-tocopherol: precursor of vitamin E, ascorbic acid: precursor of vitamin C

Natural antioxidants are often preferred by consumers, but one must know that they are less stable, consequently their efficiency is not so good (higher quantities must be used). Producing diets that have a short shelf life would not be considered practical by consumers.
They are largely more expensive: the cost of the products would reflect this price.

Choosing the right antioxidant and its level of incorporation depends on several factors: ingredients to protect, shelf life guarantee, using conditions, stability, cost etc.
Royal Canin has chosen to associate two different antioxidants plus another substance working in synergy, that enhances their efficiency and allows a decrease in the doses of incorporation. These products are:-

BHA, propyl-gallate and potassium sorbate. We do not use BHT or Ethoxquin - by using Propl-gallate and potassium sorbate their Synergistic action reduces the amount of BHA that is used. By adding these it enables us to give a longer shelf life thus reducing the cost to the consumer.

These substances are incorporated in the fats just after their extraction, in order to prevent the oxidation process from the very beginning. This is done by our suppliers of oils and fats, according to a protocol established by Royal Canin.

Whatever the additives are (vitamins and trace-elements included), they may have harmful effects when they are used over the maximum safe levels. These effects have been studied and they are well-known; this is why the European regulation imposes precise maximal rates of incorporation.

The antioxidant residues likely to be found in Royal Canin products are 5-10 times less compared to the maximum limits imposed for human food. Controls are regularly performed on raw materials to check the strict application of the rules as listed above.

All the ingredients, including the meat in Royal Canin Diets are of human grade quality. We will not use sub-class ingredients in these diets. The fats we use are from the same source as the meat and are not left over fats from catering plants. Poultry meal is the pure chicken meat with the fat and water content removed. It is a high quality, easily digested protein source and does not contain any by-products such as feathers, beak, hoof etc. We do not include “fresh” poultry meat due to logistical problems regarding transportation in this form and it would increase the cost considerably. Royal Canin provides strict checks on all the ingredients used in our range of diets, upon delivery at the factory and then again in an external laboratory. All animal meats are first examined visually to check there are no unwanted components and if any of the ingredients do not conform to the standards, then they are refused.'

Human exposure to BHA

Potential for consumer exposure to BHA by ingestion and dermal contact is widespread. In 1975, the estimated average daily intake of BHA in the diet was 4.3 mg (IARC 1986). It is a widely used food additive in products containing vegetable oils or animal fats. It retains its antioxidant properties even at high temperatures. The general population may be exposed to BHA in butter, lard, meats, cereals, baked goods, sweets, beer, vegetable oils, potato chips, snack foods,
nuts, dehydrated potatoes, flavoring agents, sausage, poultry and meat products, dry mixes for beverages and desserts, glazed fruits, chewing gum, active dry yeast, defoaming agents for beet sugar and yeast, and emulsion stabilizers for shortenings.

The estimated U.S. consumption of BHA in food increased to 660,000 lb/yr during 1970 to 1982, up from 374 lb/yr in 1960 (Anonymous 1984, IARC 1986). Reported annual consumption for BHA in the mid 1970s was 990,000 lb compared with 3.1 million lb for butylated hydroxytoluene (BHT)
(Kirk-Othmer 1978). Industrial use of BHA has largely been replaced by tert-butylhydroquinone (TBHQ) (Kirk-Othmer 1980).
Potential dermal exposure exists for the population that uses cosmetics, especially lipstick and eye shadow

Report on Carcinogens, Eleventh Edition; U.S. Department of Health and Human Services, Public Health Service, National Toxicology Program .
http://ntp.niehs.nih.gov/ntp/roc/eleventh/profiles/s027bha.pdf

Susan E. Orosz, Ph.D., D.V.M
http://www.lafeber.com/Lafeber-Library/Articles/orosz/ethoxyquin.asp

Dr. Lisa Freeman, DVM
http://www.executec.com/nutra.htm

http://www.engormix.com/e_articles_view.asp?art=431

Food Antioxidants: Technological, Toxicological, and Health Perspectives
Edited by DL Madhavi, SS Deshpande, and DK Salunkhe / Dekker 1996
http://www.mindfully.org/Plastic/Antioxidants/BHA-BHT.htm

Report on Carcinogens, Eleventh Edition; U.S. Department of Health and Human Services, Public Health Service, National Toxicology Program .
http://ntp.niehs.nih.gov/ntp/roc/eleventh/profiles/s027bha.pdf

Committee on Toxicity of Chemicals in Food,
Consumer Products and the Environment
http://cot.food.gov.uk/pdfs/cotcomcocannualreport1992.pdf

Food Standards Agency-funded research on health effects of mixtures of food
additives (T01040/41)
In 2001, the Food Standards Agency commissioned a project to develop
methods to assess the health effects from mixtures of food additives. From an ILSIEurope
ADI Task Force report, four food additives were selected where the
possibility of joint actions or interactions occurring in the liver could not be excluded.
The selected additives were all reported to produce liver enlargement which was
often associated with enzyme induction, and comprised butylated hydroxytoluene
(BHT), curcumin (CC), propyl gallate (PG) and thiabendazole (TB).
http://cot.food.gov.uk/pdfs/tox200802.pdf

Food Standards Agency research project T01040/41 – summary of results
This annex contains prepublication results and is therefore received in
confidence and will not be published on the Committee’s website. It
should not be circulated beyond the Committee members, secretariat and assessors.

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