The world of citrus fiber in pet food

It is sometimes questioned whether the natural diets of cats and dogs – as carnivores – contain fiber at all. However, since both dogs and cats eat the intestines of their (generally vegetarian) prey in the wild, they thereby indirectly ingest plant material. Dogs are considered more omnivorous than cats because they eat some plant materials such as berries by choice. Although both animal species naturally ingest fiber, the fermentation of fiber and its benefits are more prominent in a dog’s digestive system than a cat’s.

Fiber content

For diets low in fiber, the addition of pectin can increase fecal volume and moisture, potentially allowing easier passage and improving the pet owner’s cleaning experience. Depending on the fiber source and the manufacturer’s production process, fiber can allow more moisture to be added to the finished product. However, this could increase the chance of mold growth so increased microbial testing is recommended. For diets already high in fiber, such as vegetarian diets, it might be worth replacing part of the current fiber content.

Water-holding and emulsifying properties

Pectin is a prominent type of soluble fiber in citrus pulp which has great water-holding capacity and is commonly used in jams. Consequently, it has applications in wet pet food as it helps the finished product to retain water over time.

There are a variety of citrus fibers available in the market, designed for different applications – ranging from high levels of pectin to depectinized products. A source with less pectin and more (hemi)cellulose could be more appropriate to increase the energy content.

Besides their water-holding capacity, some citrus fiber products can be used as an emulsifier to allow fat and water to mix, creating creamy liquid solutions. As a result of both of these properties, citrus fiber can be used instead of gum in wet pet food and as a texturizer in dry kibble.

Scope for ‘natural’ claims

As a clean-label ingredient, citrus fiber provides some scope for pet food brands looking to make ‘natural’ claims on their packaging. However, according to the European Pet Food Industry Federation (FEDIAF), the extraction process can affect whether the pulp can be claimed to be ‘natural’. It is possible that the citrus fiber falls under the EU regulation No. 1831/2003 on Additives for use in animal nutrition, and/or the EU regulation No. 68/2013 on the Catalogue of feed materials, in which case it must be declared differently.

Despite the antioxidative properties of citrus fruit, citrus fiber contains little antioxidant, and claims relating to flavonoids including antibacterial, antiviral and anti-inflammatory cannot be made.

Microbial fermentation

Pectin from citrus pulp is completely fermentable in the digestive system of dogs and cats and is even more fermentable than the industry standard: beet pulp. It can be seen as a prebiotic, because it serves as ‘food’ for fermenting microorganisms Bifidobacterium and Lactobacillus, which are considered part of a healthy microbiome.

Beneficial fermentation products are short-chain fatty acids (SCFAs), and the dietary addition of citrus pulp has been shown to increase acetate, butyrate and lactate in dogs. Also, in the same study, orange fiber presented higher apparent total tract dietary fiber digestibility than beet pulp, and butyrate production was superior to that of inulin and beet pulp.

Gut health claims

SCFAs support the gut structure by providing a rapid energy source for gut cells (enterocytes). SCFAs also keep the gut pH low and encourage the ‘good’ gut microbes. Furthermore, they help to regulate water and thereby the bulk of the stool, while propionate as one of the SCFAs also serves to provide nutrition for the liver. Gut health claims can be seen across the board, from economy to premium products, based on inclusion rates ranging from 0.1%-2% depending on the product type and requirements.

Despite the benefits of fermentation, citrus fiber, orange fiber and pectin are repeatedly shown to reduce dry matter, organic matter and energy digestibility of pet food. Such products may therefore be a better choice for energy reduction diets rather than high-energy diets, and they also offer good potential for treats.