A TVP "meat piece" does a better job of distinguishing itself as a "meat chunk" than an actual chunk of chopped or reformed meat.
Textured vegetable protein (TVP), the meat extender we loved
to ridicule in our school lunches, may be more prevalent in
petfood than many realize. It isn't being used to stretch the
meat budget or even to supplement meat protein. Instead, the
most common application for TVP in petfoods is cosmetic. It
makes for a great visual effect in canned foods, making them
look more like real meat.
It's not a cost-cutting matter. As it turns out, in a wet
petfood application, a TVP "meat piece" does a better job of
distinguishing itself as a "meat chunk" than an actual chunk of
chopped or reformed meat. The reason for this is because TVP
retains its shape, coloration and distinct outline during
retort. So, one can discern with just a glance that there is a
real difference between this virtual meat chunk and its
surroundings. It is especially true for the chunk in loaf
product formats in which a meat piece is embedded in a meatloaf
or paté.
So, it appears that petfood isn't solely about nutrition. It
does have its shallower side in which appearance matters. While
this might give purists indigestion, the application of TVP
chicken-analog pieces in a loaf product or beef-analog pieces
in a lighter colored chicken based meatloaf is pretty popular
in the canned dog food market. The technology is also deployed
in numerous overseas markets without shame.
While it may be assumed that wet petfoods are predominantly
meat based and this infiltration of vegetable proteins into
these products might seem like heresy, their popularity would
indicate that it is an effective method to deliver the visual
experience desired by the pet owner. So, if TVP is so common,
then what is it and how well does it perform with our pets?
According to the
AAFCO Official Publication
(2008): "Textured Soy Protein Product is made from defatted soy
flour mixed with water and/or steam, extruded and then
dried."
While the products on the market are predominantly soy
flour, depending on the application, cost, availability and
desired appearance of the piece, other proteins might also be
included. Examples include small quantities of wheat gluten or
more commonly flour from other edible beans (e.g., lima, pinto
or navy). Thus, it is most often known and marketed as the
broader "vegetable" protein, rather than exclusively as soy
protein.
TVP came about during the 1960s as research to develop meat
analogs met up with the expanding application of extrusion
technology. In general, defatted soybean flour (soybean meal
that has been ground really fine) is combined with processing
aids (calcium chloride, sodium carbonate, sulfur) and colors
(caramel color, FD&C red #3, etc.) in the preconditioning
cylinder prior to extrusion.
TVP retains its shape, coloration and distinct outline during retort.For the production of TVP, extruders are commonly
high-temperature, short-time single screw machines very similar
to those used in the production of extruded petfoods. The
actual development of texture occurs at the end of the extruder
screw and during exit from the die as cellular proteins
reorient or realign themselves into strands or fibers (Harper,
1978). These newly formed fibers are created when denatured
protein molecules rupture and form new intermolecular peptide
bonds that then aggregate into fibrous subunits.
After conveyance away from the extruder, the pieces are
dried to a moisture level of 6% to 8%. In the dried form, TVP
is stable, with most suppliers claiming a shelf life of one to
two years. The dry product is easy to handle and in canned
formulas may be added at 1% to 15% depending upon the visual
appearance desired.
The dry pieces rehydrate readily and will absorb two to
three parts water per unit weight. After rehydration, the TVP
piece is perishable and should be handled in a manner similar
to that of meat. Thus, rehydrated pieces should be processed
immediately or stored under refrigeration.
Since the starting material for TVP is soy flour (also known
as finely ground soybean meal), the nutrient composition should
not be expected to differ substantially. TVP is sold at a crude
protein of 50% or more. It contains approximately 1% fat, 3 to
6% ash and 3.5 to 5% crude fiber (about 15% total dietary
fiber).
In a recent scan through the literature, no data reporting
intake or palatability issues were found related to TVP. It is
generally assumed the flavor and aroma of TVP is bland, and it
will take on the sensory attributes of surrounding
ingredients.
As for dietary effects in pets, several research studies
have been published. Each study utilized the same experimental
diets in which dogs were fed canned foods that replaced beef
with TVP at levels of 14, 29 and 57%. No health or nutritional
anomalies were noted from these studies. However, relative to
beef, dogs fed the TVP-containing diets had slightly lower
nutrient digestibility, their stool volume increased and the
stools were softer and more fluid (Hill
et al
., 2000; Hill
et al
., 2001).
It was also noted that insulin secretion in the first few
hours following a meal was decreased for dogs fed the TVP diets
(Hill
et al
., 2006). This is most likely due to the oligosaccharide
content of TVP and, if managed properly, could be a dietary
tool in treating diabetes.
TVP is a convenient, stable and effective means for
achieving the appearance of meat pieces in wet dog and cat
foods. At inclusion levels well beyond those commonly used in
petfood, TVP has been shown to be safe, though a negative for
stool consistency. Palatability or animal acceptability has not
been identified as an issue, and at typical dietary levels TVP
has minimal impact on digestion or stool consistency. So, while
TVP may have an image issue with its name, it has proven itself
in the categories of appearance and utility.