Science Diet to Have Plastic Coated Kibble?

Susan Thixton posted on her site Truthaboutpetfood.com about some changes being made to Science Diet which should be taking place by this coming December 2012. Apparently Science Diet is coming out with more natural kibble. Before you get your hopes up about Hill's offering a potentially more species-appropriate kibble than their regular corn and grain based products, there is evidence that their new more natural kibble will be coated in plastic, specifically low-density polyethylene, to extend the shelf life. So we're clear, polyethylene "is the polymer that makes grocery bags, shampoo bottles, children's toys, and even bullet proof vests."

Note: I love the jab Hill's makes about consumers "making product choices based primarily on a set criteria for ingredients, rather than the overall promise of nutrition and clinical research." Ok ok hold on a darned second. They are, right there in the statement, saying they are including "more natural ingredients" but at the same time saying that their current food is based on the promise of nutrition and clinical research. Did they just admit that their current foods are not natural? Seems they did.

As noted in Thixton's post, Hill's has gotten a patent. The patent says of the polymer coating: "wherein the thickness of the polymer film is between 1 and 2000 microns." How big are microns? Sounds small, and they are. But 2000 of them adds up. 2000 microns is 2 mm. Up to 2 millimeters of plastic coating on the kibble to extend the shelf life. The polymer, as noted in the patent, would be designed to quickly dissolve once in the pet's mouth. I wondered about that part so began searching.

It is specified in the patent that it will be low-density polyethylene polymer. What is low-density polyethylene used for? According to DynalabCorp, " Low Density Polyethylene (LDPE) is a most useful and widely used plastic especially in dispensing bottles or wash bottles. It is translucent to opaque, robust enough to be virtually unbreakable and at the same time quite flexible... LDPE is ideally suited for a wide range of molded laboratory apparatus including wash bottles, pipette washing equipment, general purpose tubing, bags and small tanks." It has "Excellent resistance (no attack) to dilute and concentrated Acids, Alcohols, Bases and Esters." I've looked and looked trying to find where LDPE is used as a pill coating or something similar to no avail, including searches adding the word 'polymer.' The only information I'm able to find states how it is used for making inorganic food packages, plastic bags, or other plastic products. How exactly is plastic supposed to dissolve in the dog's "oral cavity" when dogs don't have a piece of kibble in their mouth more than a second anyway? Dogs don't have the physical capability of chewing their food and certainly have no reason to hold food in their mouth to allow a 2mm coating to dissolve. Most dogs swallow kibble pieces whole as fast as possible.  Hill's can't honestly expect it to dissolve in the dog's mouth. It'll have to dissolve in the stomach and the rest of the digestive tract- if at all from the sounds of it. That's not the real point though, the real point is that from everything I can find, LDPE is a pretty tough plastic that wouldn't dissolve at all.

Another claim in the patent is that the "polymer film further comprises a polymer selected from zein, casein, starch(es), cellulose(es), gum(s), gelatin, and combinations thereof." Maybe that's how the LDPE will be able to be dissolved? Let's do a quick look at what each of these items is derived from, what it is, and common uses.

Zein : The principal protein of corn. It is "a mixture of water insoluble proteins" and "Zein is not a valuable feed component since it is water insoluble and deficient in some of the important amino acids, lysine and tryptophan. Zein is also an alcohol soluble protein in corn which has been used as a water barrier and protective coating for foods such as nuts and confectionery products."

Casein: The principal protein found in cow’s milk. "It is responsible for the white, opaque appearance of milk" and "The major uses of casein until the 1960s were in technical, non-food applications such as adhesives for wood, in paper coating, leather finishing and in synthetic fibres, as well as plastics for buttons, buckles etc. During the past 30 years, however, the principal use of casein products has been as an ingredient in foods to enhance their physical properties, such as whipping and foaming, water binding and thickening, emulsification and texture, and to improve their nutrition."

Starches : "Starches" is very vague but includes foods such as potatoes, cereals, wheat and other grains, and rice. "Food starches are typically used as thickeners and stabilizers in foods such as puddings, custards, soups, [etc]"

Cellulose: Substance that makes up plant cell walls. "Cellulose can be used to make paper, film, explosives, and plastics, in addition to having many other industrial uses."


Gums: Also very vague, but "Food gums have an ability to stabilize liquids, thereby allowing other ingredients to be dispersed and suspended in the solution.  Food gums can also be used as an emulsifier, which means they disperse fat to allow it to become more water-soluble." They come from many sources. "Food gums come from all over the world, from both the land and the sea.  For example, carrageenan and alginates come from seaweed.  Many food gums come from plants, such as guar, locust bean gum, pectin and gum arabic.  Some food gums are derived by microbial fermentation (e.g. xanthan) while others are synthesized, such as (cellulose gum).  Others, such as gelatin are derived from animal tissue."

Gelatin: See above.


I'm seeing a lot of uses for making inedible plastic products apart from starches and gums. Not very promising but I guess we'll have to wait and see.

I'm very concerned that Hill's believes it is acceptable to coat their food in a plastic polymer simply to extend shelf life, and it's even more appalling that they are using it on their supposedly more "natural" formulas to be released. In what horrible world does natural mean plastic-coated?