Pet Food Enzymes - Application Sheets

• Enzymatic Hydrolysis of Proteins Using Novozymes Proteases
• Extensive hydrolysis of proteins with Flavourzyme
• Use of Novozymes amylases in dry pet food extrusion
• Use of Proteases in Production of Digest for Pet Food

An important sales parameter for pet food is palatability. Good palatability is dependent on the raw materials used and on the processing conditions. In this respect dried pet food products containing a relatively high percentage of cereal ingredients need careful optimization. For this purpose digests can be used, i.e. meat or meat by-products hydrolyzed using enzymes. The hydrolysis process liquefies the raw material and creates a good flavour.

The digest, which may be suspended in a fat coating, is sprayed on the dry extruded base material.

Proteases are used to produce the digests, as described below.

The general process layout for processing 1,000 kg of meat by-product is shown in Figure 1 and discussed below.

The type of raw material used has a major impact on the quality of the endproduct. Poultry by-products are especially favourable for digest to be used in cat food. Chicken/turkey intestines are often used, preferably with the liver too. The process can also be used for processing raw materials of porcine and bovine origin, e.g. liver, lungs, etc.

It is recommended to grind the raw material in a meat mincer or a wet milling system, before transferring the meat to the digester/hydrolysis tank. This is done to give the enzymes better access to the meat proteins.

The bacteriological quality of the raw material is important. When good quality raw materials are used, e.g. chicken liver, heat treatment is not necessary and hydrolysis may start immediately. If the raw material has a very high bacterial count, such as viscera/intestines, heat treatment before hydrolysis is recommended, and a pasteurization step should be carried out prior to enzyme addition.

The pH of the minced meat substrate should be as close as possible to the pH optimum for the enzymes. In practice, the pH should be in the range of 6.0 to 7.5 before the enzyme is added. If necessary, the pH can be adjusted using a base, e.g. NaOH, Ca(OH)2 or NaHCO3.

The temperature is adjusted to 55-65°C (131-149°F).

The liquefaction of the meaty raw material is performed by proteolytic enzymes and the desired properties of the digest determines the choice of enzyme products.

The standard protease for digestion is Novo-ProTM D, and the actual dosage depends on the raw material and processing time available. Normally, a dosage of 0.50 kg per 1,000 kg of raw material is sufficient to liquefy the raw material within 30 minutes. A longer digestion time or higher dosage may be required, depending on the raw material. Alternatively, the other serine protease Alcalase® may be used at a recommended dosage specified in Table 1.

In cases where more complete hydrolysis of the raw materials is required, it is recommended to use Flavourzyme®, an exo-peptidase, as well. Flavourzyme will create shorter peptides and free amino acids in the digest, thus promoting subsequent flavour reactions and palatability enhancement.

The digestion process can be terminated by heat treatment or by reducing pH to 3. Traditionally, liquid digests are stabilized by adding phosphoric acid, which at the same time will terminate the digestion process and inactivate the enzymes after 30 minutes at the low pH. For production of digest powders, it may not be necessary to acidify prior to drying, and in that case, heat treatment is recommended. To ensure complete inactivation the temperature should be kept at 90-95°C (192-203°F) for 10 minutes prior to spray-drying.

The need for further processing before packing is limited to two steps, depending on the raw material used:

• The digest should be screened, for instance on a 60 mesh screen, to eliminate larger particles from the liquid digest, so that no blockage of spray nozzles occurs. It may be a good idea to wet-mill the digest prior to screening, in order to minimize the screen loss.
• A homogenizing step may be necessary if the raw materials contain a large amount of fat, to ensure good homogenization of the liquid digest.
• Furthermore, an emulsifier may be necessary to keep a stable emulsion.