Pet food and animal feed quality acceptance has some differences to that of food products manufactured for human consumption. In the pet industry, particularly, the texture must appeal to both the animal consuming and the owner/consumer. The palatability of the food in terms of appearance, smell, taste and texture should ensure the animal eats the product and, with the possible exception of taste, these attributes must satisfy human sensory processing.
All food intended for animal consumption has required nutritional and safety targets, which restrict the variability possible in the formulation process. For this reason, once the acceptability criteria are proven, there is benefit in using texture analysis techniques to quantify the measurable properties.
As with food for human consumption, the correlation to desirable texture first involves sensory testing of a range of samples. The difficulty for animal food items is gaining feedback from the subjects, which have heightened senses compared to that of humans. Usually a desirable product is one that is simply not rejected, although experiments can be designed to rate preference of one formulation over another. Dogs (omnivores) and cats (carnivores) represent the vast majority of the market for pet food. Products for daily consumption, treat items and occasional veterinary prescribed medication being the categories of food that an owner would need to supply, with the choice of wet or dry formulation.
Raw ingredient selection, the manufacturing processing and the need to deliver the product to its packaging in an efficient and economically viable manner all have influence on final animal food texture. The ingredient mix is driven by a nutritionist, stipulating limits for, amongst other things, proteins, amino acids, carbohydrates, vitamins and minerals, ensuring variety of diet and a balance of the essential requirements of the animal’s biology – meat, vegetable content, etc.
Additionally, specific formulations to improve conditioning or provide additional medical support for pets are available, including: kitten/puppy (young), adult, and senior life stages; dental hygiene, urinary tract maintenance, joint health and hairball control; reduced calorie for obese, inactive or indoor pets. Small mammals and rodents are also fed kibble-like products, such as pellets and nuggets, which are subject to the same processing challenges Processing the ingredients to form the final product, introduces further elements that can impact texture adversely. The operational parameters for the manufacturing equipment must be optimized to maintain operational efficiency, but still deliver the product that is palatable. Thermal processing / heat treatment is applied to pet food for safety, stability and shelf life performance, yet has an effect on animal proteins and fats – both fundamental to the nutrition and palatability. The production throughput of extruded, shaped dry kibble pellets and viscous, wet food, delivered via filling machines is sensitive to the physical properties of the ingredients at the appropriate production stage and must be balanced against the final texture.
These consumer choices add to the variability in raw materials, which can add uncertainty to the production of the desired texture – increasing the need to quantitatively define it, via texture analysis. Similarly, the parameters controlling dispensing of the product into its packaging – whether sachet, can, pouch, retort or tray - can be evaluated for their impact.
Food products for animal husbandry are also subject to nutrition and safety legislation, as are pet foods - which are a sub-category of animal feed. The regulations are concerned with the fact that farm animals form part of the human food chain. The nutritional requirements are factored towards commercially optimal meat and dairy produce, rather than prolonged lifespan. The same challenges exist in balancing the manufacture, packaging, storage and transportation of the feed, with the necessary palatability.
Texture measurement in the animal feed industry is of most value in maintaining the consistency of palatable products, in the face of changing ingredients or the improvement of shelf life or packaging options. Dry kibble, pellets and biscuits, canned or otherwise packaged wet foods can be tested in the same manner as similar consumer products.
Measuring small particulates in confections, such as meringue is much more accurate in bulk form.
Slice through nougat to measure average hardness from its cross-section. Cross-sections of samples can be evaluated by slicing through them with blades and wires imitating the actions applied by the front incisor teeth. Attributes assessed include bite strength, cook quality, tenderness and toughness. Product texture variations are measured by slicing through the whole sample.
For bar-shaped treats, the three point bend is an ideal method for determining flexibility, or brittleness.
Gelatin (gelatine) is a natural protein of animal origin, which is commonly used in many pet foods. It performs several functions, any of which may be the primary purpose.
Testing the Bloom strength of gelatin in-house adds control to the formulation process.