Heat processing changes the protein quality of canned cat foods as measured with a rat bioassay.

Abstract

ABSTRACT:The purpose of this study was to determine the influence of increasing heat treatment on the protein quality of a canned cat food. A standard recipe cat food was canned and heat-treated for different times in a standard laboratory autoclave to obtain experimental diets containing different lethality values. Estimates of the lethality value of the different diets were calculated using the temperaturetime relationship recorded with a data logger positioned at the center of the can. The experimental diets were analyzed for crude protein, amino acids, and reactive lysine (fluorodinitrobenzene and Omethylisourea) and were used in a rat bioassay for the determination of the true ileal digestibility of amino acids. The heat treatment of the cat food resulted in experimental diets with lethality values of 5.3, 8.6, 17.2, and 24.3 min. There was no decrease in the amino acid content of diet with increasing heat treatment. The reactive lysine content of the diets also showed no change with heat treatment. There were significant ( P < .05) changes in the true ileal digestibility of all amino acids and amino acid nitrogen, and the digestibility of most amino acids decreased with increasing heat treatment.

The Maillard reaction and pet food processing: effects on nutritive value and pet health

“…The difference between total and reactive lysine content in the pet food ingredients used in this particular food does not explain the high differences between total and reactive lysine reported in some moist canned foods. True ileal total lysine digestibility as measured using growing rats consistently decreased with increasing F-values from 84·2 % for the untreated food to 77·4 % for the food with the highest lethality value (24·3) (133) , indicating that part of the lysine was rendered indigestible. However, total as well as OMIU-and FDNB-reactive lysine did not change due to processing.…”

“…This indicates that processing conditions applied during retorting of cans favour the Maillard reaction, but effects of processing conditions on total and reactive lysine content have been the subject of only a few experiments. Retorting a standard moist cat food recipe containing a low content of carbohydrates (maximum 6·7 %) at lethality values (F-values) of 5·3, 8·6, 17·2 and 24·3 (temperature set at 1218C, time periods between 80 to 120 min) had no effect on the total or OMIU-reactive lysine content (133) . In the unprocessed food, the difference between total and reactive lysine was 12·0 %.…”

“…Retorting is a temperature/ time-dependent process, using an F 0 -value as a unit to summarise the lethality of the heat employed on the product. The F 0 -value represents the time equivalent in minutes of a heating process to destroy micro-organisms at the reference temperature of 121·18C (133) . In general, the process time should be at least 3 min at 121·18C (F 0 -value of 3) to kill pathogenic bacteria (118) .…”

“…However, higher values (F 0 -value . 10) are employed in practical pet food production in order to destroy spores (133) . As described above, the difference between total and reactive lysine can be considerable in moist canned foods, with values between 39·0 and 61·8 % (Fig.…”

Development of a novel bioassay for determining the available lysine contents of foods and feedstuffs

“…However, there are a number of factors that control the rate of Maillard product formation, including temperature, pH, water activity and reactant concentration 12 . Many foods or feedstuffs undergo processing during their manufacture to either improve palatability, functionality or food safety 13 , during which, foods and feedstuffs are subjected to heat, pH extremes and pressure, all of which can greatly accelerate Maillard product formation.…”