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Price is often a
good indicator of quality since low cost brands of
cat food must contain low cost raw materials.
Budget brands generally contain "meat and
meat derivatives" and "cereal". In
premium brands cereal appears in a smaller
percentage or not at all. The texture of budget
brands is more glutinous and less meat-like than
the texture of gourmet brands and the smell is
stronger.
American pet food
nutritional standards are set by the National
Research Council (NRC) of the Academy of Sciences.
The standards were based on purified diets and
required feeding trials for pet foods claimed to
be "complete" and "balanced."
The pet food industry found the feeding trials too
restrictive and expensive, so AAFCO designed a
procedure permitting nutritional claims based by
chemically analyzing the food for compliance with
"Nutrient Profiles." Chemical analysis
addresses content, but not palatability,
digestibility or biological availability of the
nutrients. A cat food can therefore be labeled
nutritionally complete even if the cat's digestive
system cannot extract those nutrients. AAFCO
compensated by adding a "safety factor"
so that foods contain more than the NRC
recommended amount. In the UK, Waltham (Whiskas)
also use an amount which compensates for possible
losses. Overnutrition, however, is equally
dangerous (e.g. hypervitaminosis).
How is
Canned Food and Kibble Made?
The raw materials
e.g. cattle carcasses are rendered. Pet food
manufacturers buy either the meat slurry or the
dried meal produced by rendering plants. Canned,
dry or semi-moist cat food all contain similar
ingredients. The ratio of protein, fat and fiber
may be different and the amount of water present
and the types of preservative used will differ
greatly. Canned food is more bulky which is good
for bowel action, but its soft texture means that
teeth are not "exercised" which leads to
tartar build-up and gum disease. Dry foods are
convenient for the owner, but they are compact,
energy dense and can cause constipation because
the cat's bowel does not get enough bulk to keep
throughput smooth. The natural diet of the cat is
semi-moist - moist muscle meat and tough skin and
sinew.
Dry food is made
with a machine called an expander or extruder. Raw
materials are blended and the mixture is fed into
an expander. It is then pressure cooked (steam,
pressure, very high temperature) into a paste
which is extruded through pipes which shapes blobs
of paste into biscuits. These are puffed like
popcorn and baked or dried, then sprayed with fat,
digests and flavor enhancers. The cooking process
kills bacteria, but may be ineffective against
heat stable toxins or prions (causative agents in
BSE). Non-extruded dry foods are baked and are
denser and crunchier and may require no coating of
fats of flavorings.
Most canned foods,
especially budget varieties, are meat slurry which
may or may not have been texturized and which
contains a gelling agent to solidify them. A
typical can of cat food may contain 45-50% meat or
poultry by-products. Some contain more water than
others - those in jelly or gravy containing the
greatest amount of water. In order to compare
different cans, the water has to be removed and an
analysis performed on the remaining dry matter.
Some labels provide a "dry matter
analysis" to aid the comparison. To make
canned food, the ground ingredients are mixed with
additives. The meaty chunks are made using an
extruder. The mixture is cooked and canned. The
sealed cans are sterilized by pressure cooking.
Some food is cooked in the can instead of
beforehand.
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