In the world of food for pets, no different than with food
for people, there are a number of additives used to enhance a
product's presentation--some obvious and some not. One less
obvious ingredient used in canned food applications is
carrageenan. This ingredient is added to help form a loaf
(meatloaf), retain moisture in the loaf and bind the contents
together so they slide from the can intact. This ingredient is
often lumped into the category of gels and thickeners, which
"foodies" call hydrocolloids.
Carrageenan's sole purpose is to enhance the appearance of
the product and create a consistent mix of meat and other
ingredients from top to bottom. But exactly what is this quiet,
unassuming ingredient, and should it be there?
The name carrageenan may be new to many, but the ingredient
has been around quite a while. The earliest applications were
reported some 600 years ago as a seaweed extract from
Chondrus crispus
, also known as Irish Moss, used to gel milk products.
Carrageenan didn't become a commercially viable ingredient
until after World War II. Today it is found in a wide variety
of foods. Most akin to petfoods are applications in processed
meats wherein carrageenan is used to increase moisture content
and provide mouth feel and texture, especially in low-fat
meats.
Like most food hydrocolloids (hydrophilic colloid),
carrageenan is a branched-chain carbohydrate. It is a galactan
sugar extract from red seaweed. In the
AAFCO Official Publication 2008
, it is listed under title 87.5 as an "additional special
purpose product" and is classified under the food additives
amendment as an "emulsifier, stabilizer or thickener for
petfoods."
The exact FDA regulation 21CFR172.620 describes carrageenan
as "the refined hydrocolloid prepared by aqueous extraction
from members of the families
Gigartinaceae
and
Solieriaceae
of the class
Rodophyceae
(red seaweed)."
Seaweed from these various species and from various regions
of the world are harvested from the sea or estuaries by boat,
dried at nearby processing plants, washed and macerated in hot
alkaline solution. The alkali helps form
3,6-anhyro-D-galactose, which is essential to gel formation.
After alkaline extraction, the material undergoes various
cleaning, concentrating, drying, sizing and standardizing
steps.
The earliest applications were reported some 600 years ago.The seaweed extract, carrageenan, has a molecular weight of
100,000 to 1 million, consists of linear galactan
polysaccharides with alternating (1»3) and (1»4) β-D-glycosidic
linkages and has an ester sulfate content of 15-40%. Three
types are commercially available that vary in the number of
anhydro-linkages and sulfate groups:
- Kappa (κ);
- Iota (ι); and
- Lambda ( λ).
The three types don't exist singly but are sold as mixtures
with one type predominating. These mixtures are influenced by
species, habitat and harvesting conditions.
Petfood principally uses κ-carrageenan because it survives
retort, forms a strong but brittle gel and is stable to pH just
under 4. The κ-carrageenan is strongest in the presence of
potassium ions, which create an aggregate (like rocks in
cement) with the polygalactan coils, and also works in synergy
with other hydrocolloids like locust bean gum. This type of
carrageenan is commonly used at less than 1% of the
formula.
The ι-carrageenan is similar in many respects to
κ-carrageenan but forms an elastic gel, which is strengthened
by calcium ions and does not interact synergistically with
other hydrocolloids. The λ-carrageenan does not create a gel
but acts as a thickener.
In canned meat products the exact mode of action that allows
for carrageenan to serve as a gel is not completely understood,
but it is thought that the gel interacts directly with proteins
in the meat system (Trius and Sebranek, 1996). In wet petfood
applications, carrageenan has been reported to be superior to
animal plasma, egg albumen and wheat gluten (Polo
et al
., 2005). For dogs, the use of gelling agents such as a
combination of guar/carrageenan had a positive impact on diet
digestibility and stool quality remained good, but stool output
increased slightly (Karr-Lilienthal
et al
., 2002).
The soluble fiber in canned foods from sources such as
carrageenan may account for part of the reason that cats need
more taurine in canned foods. The theory is that increased
taurine degradation by intestinal flora occurs due to greater
fermentation as more soluble fiber (of which carrageenan would
qualify) reaches the colon (Anantharaman-Barr
et al
., 1994).
There have been a few reports that carrageenan may be
carcinogenic. But in long-term bioassays, carrageenan has not
been found to be carcinogenic, and there is no credible
evidence supporting a carcinogenic effect or a tumor-promoting
effect on the colon in rodents, humans or dogs.
A vast body of information explains the safety and utility
of this naturally occurring gelling agent. Carrageenan is very
effective at providing form and texture to meat-based wet
petfoods at low concentrations, and pets seem to do well
nutritionally on products that contain it. While it may seem
simple, just the right mixture (kappa, iota and lambda) is
unlikely right off the shelf. A technician with experience and
ties to a consistent carrageenan supply base will be
required.