PET Food Processing - March 2021 - 40

FORMULATION

Final products
should not only meet
recommendations,
but the ratio of the AA
to each other and the
unique attributes of
the dogs to which the
food is fed need to be
considered.
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inhibitors, tannins, and phytate can all decrease protein
and AA availability (Gilani, et al. 2005). The inhibitors
of serine proteases (trypsin and chymotrypsin) are the
most important enzyme inhibitors in legumes with respect to protein digestion (Belitz and Weder 1990).
These enzyme inhibitors inhibit the function of trypsin and chymotrypsin enzymes, decreasing the overall
digestion of proteins and subsequently the availability
of AAs for absorption (Singh and Basu 2012). Phytate,
while primarily associated with minerals, can also bind
and decrease the availability of proteins in the gastrointestinal tract (Singh and Basu 2012). Tannins can
negatively affect protein digestibility through the precipitation of proteins in the gastrointestinal tract reducing availability for absorption (Singh and Basu 2012)
(Gilani, et al. 2005). Therefore, importance is placed on
processing pulses to enhance their digestibility and suitability in pet foods.
While processing of legumes can include methods
such as dehulling, roasting, boiling, and pressure-cooking, the most common method utilized in the pet industry is extrusion for their inclusion into dry commercial
dog diets. The high pressure and heat used in the extrusion process not only allows for the inclusion of legumes
in kibble but is necessary to reduce ANFs and may result in improved protein and indispensable AA contents,
digestibility, and protein quality (Malcolmson and Han
2019). Caution must be taken as these high-heat processing methods may also result in decreased protein and
indispensable AA digestibility, which may be attributed
to the formation of Maillard reaction products, as well
as thermal cross linking of AAs (Khattab, et al. 2009).

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Despite this, the reduction or destruction of ANFs from
these processing methods is generally greater compared
to reduction in AA content and overall results in a net
positive change in protein and AA availability.

Supplying adequate AAs

As mentioned, using nitrogen balance techniques to determine minimum requirements of indispensable AAs
does not account for secondary metabolic utilization of
an AA (Moughan 1999). Supplying adequate indispensable AAs to adult dogs goes beyond purely supporting
protein synthesis, as most AAs have secondary roles
through synthesis of secondary metabolites. For example, tryptophan is an indispensable AA for dogs and
while its primary role is in its contribution to protein
synthesis, tryptophan is also vital for a variety of secondary metabolic processes, including the synthesis of
both serotonin and melatonin (Triebwasser, et al. 1976)
(Richard, et al. 2009) (Freeman, et al. 2013).
Tryptophan is the sole precursor of serotonin, a neurotransmitter involved in the modulation of numerous
central nervous system functions, such as mood, aggression, anxiety, and motor behaviors, (Richard, et al.
2009) (Sandyk 1992), as well as the regulation of the
gastrointestinal environment (Gainetdinov, et al. 1999)
(Mohammad-Zadeh, et al. 2008) (O'Mahoney, et al
2015). Serotonin can also be used to synthesize melatonin in the pineal gland, a pathway that is influenced by a
dog's circadian rhythm, with the activity of the enzymes
responsible being greater at night and reduced during
daylight (Szeitz and Bandiera 2107). Another example
is phenylalanine, another indispensable AA for dogs

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PET Food Processing - March 2021

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