Guar gum is a common,
but nearly invisible, ingredient in petfoods. It is found in almost every brand
of wet petfood, whether marketed at a farm-and-fleet, grocery, big-box, indie
or boutique store. However, you won’t find this ingredient on the shelf by
itself at your local grocery, and it has low recognition with consumers.
Usually this degree
of unfamiliarity would make it a target for vilification; but, surprisingly, that
has not been the case for guar gum. While that could be construed as a good
thing, it might still be worthwhile to understand whether this ingredient has
any issues and if its presence in our pets’ food delivers some intrinsic value
to our animals.
From a regulatory
standpoint, guar gum is classified in the US as a substance generally
recognized as safe (GRAS) under subpart H-Stabilizers-582.7339 of the code of federal
regulations. In the European Union E-number system, it is E412 and falls within
the category “natural gums obtained from non-marine botanical sources.”
Guar gum is a
naturally derived polysaccharide used worldwide in human and animal foods and
personal care items. It has various industrial applications for its thickening,
stabilizing and modest emulsifying properties.
In petfoods, the motivation for using guar gum rests solely on its functional properties.In petfoods, the
motivation for using guar gum rests solely on its functional properties. In
short, it is a thickener used to give the meat batter just the right viscosity
and suspending properties during the can filling process. It is effective at
very low concentrations and improves particle distribution and uniform filling,
without imparting significant influence of its own on the visual outcome of the
finished product. In essence, it is a real behind-the-scenes aid to the canning
process.
Guar gum is derived
from seed-pods of the Indian cluster bean plant (Cyanaposis tetragonolobus of the Leguminosae family). This annual
legume has been cultivated for centuries in dry arid regions of the Indian
subcontinent, where it was once grown as forage for cattle. Now it is cultivated
exclusively as a food crop. Most commercial production occurs in India and Pakistan,
with more recent production in the southern US. Guar gum became popular as a
functional ingredient following shortages of locust bean gum immediately after
World War II. It was an effective alternative and remains so to this day.
The guar seed consists
of about 40% endosperm, 15% hull and 45% germ. The endosperm is the component
of interest. Commercial extraction of guar gum was developed and industrialized
in the US in the 1950s and subsequently adopted elsewhere around the globe in
the decades thereafter.
In the process of
separating the endosperm from the hull and germ, the seed is ground or milled
into “splits.” These splits are cleaned via differential density (sifting or
cyclone), then soaked to pre-hydrate the ground materials to improve separation.
The pre-hydrated splits are flaked, ground and then dried. The removed hull and
germ are rich in protein, making them a good cattle feed. The remaining guar gum
flour is further cleaned and then ground to various particle sizes depending on
the specification of the end user. The final yield of guar gum constitutes
about 30% of the starting seed.
What makes guar gum
an effective thickener? It is primarily made up of the polysaccharide guaran, which
is almost exclusively galactomannans (more than 75%). In the simplest
description, guaran is a mannan sugar chain with galactose side units.
Once grown as forage for cattle, now it is cultivated exclusively as a food crop.For the more
technically driven reader, that is a chain of (1→4)-linked β-D-mannopyranosyl
units with single α-D-galactopyranosyl units connected to every second main chain by
(1→6) linkages. The
ratio of D-mannosyl to D-galactosyl is 1.8:1 and has a molecular weight in the
range of 150,000 to 1,500,000. This high ratio of side chains gives guar gum
more “hooks” to clasp onto other molecules—much like Velcro clasps to a knitted
sweater—thereby imparting the characteristic described as a pseudoplastic
fluid.
In the food
production environment, guar gum is known to produce the highest viscosity of any
of the naturally occurring commercial gums. It is soluble in cold and warm
water, has a wide functional pH range (pH 4 to 10) and is effective at
concentrations as low as 0.25%. However, beyond 1% guar gum can become too
thick or viscous for most purposes. It also breaks down or thins at very high
temperatures, so the viscosity formed during the food preparation phase
disappears at cooking temperatures or following retort.
Incorporating guar
gum into the formula can be a little tricky. In most cases, it will require high
shear mixing and copious amounts of water to prevent formation of clumps (e.g.,
gum balls). In addition, the rate of hydration is affected by the salt
concentration of the meat batter and the particle size of the guar gum—larger
particle sizes take longer to hydrate.
From an animal
standpoint, guar gum is an effective soluble fiber. By laboratory analysis, it
is greater than 80% total dietary fiber, with the majority of this as soluble
fiber (more than 65%) and a small amount of insoluble fiber (about 15%). Guar
gum is rapidly fermentable with a pattern of short chain fatty acid production
similar to the fructans like FOS or inulin (Flickinger et al., 2000; Bosch et al.,
2008).
In dogs fed wet
foods, guar gum was shown to improve amino acid digestibility, fecal dry matter
and stool scores (Karr-Lilientahl et al.,
2002) and was reported to reduce post-prandial plasma insulin and cholesterol (Diez
et al., 1998). It may do this by dramatically
increasing digesta viscosity (Dikeman et
al., 2006), thereby slowing digestion and subsequent nutrient absorption. However,
it did not affect fecal bile acid excretion or taurine status in cats
(Ananthraraman-Barr et al., 1994).
From an animal standpoint, guar gum is an effective soluble fiber.While thermal
processes may affect viscosity, they do not affect physiological responses by
the animal (Maskell et al., 1994).
High levels of guar gum may change the mouth feel of the food and thereby
affect palatability; but no data were found to indicate whether this was a significant
concern.
Guar gum has near
uniform regulatory acceptance around the world, appears to be an effective
natural ingredient that possesses functional food thickening and emulsifying
properties and provides nutritional value to the pet. Not bad for what some
might consider to be an invisible processing aid.