Carrageenan: for appearance's sake only?
What is this quiet, unassuming ingredient, and should it be there?
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.
Kappa, iota, lambda
The seaweed extract, carrageenan, has a molecular weight of 100,000 to 1 million, consists of linear galactan polysaccharides with alternating (1Â»3) and (1Â»4) Î²-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 (Îº);
- Iota (Î¹); and
- Lambda ( Î»).
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 Îº-carrageenan because it survives retort, forms a strong but brittle gel and is stable to pH just under 4. The Îº-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 Î¹-carrageenan is similar in many respects to Îº-carrageenan but forms an elastic gel, which is strengthened by calcium ions and does not interact synergistically with other hydrocolloids. The Î»-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.