Principles Of Pet Food Palatability: Factors That Influence Wet Pet Food Palatability

RESEARCH & DEVELOPMENT - TECHNICAL POSITION PAPER

Leading with Technical Expertise - White Paper

Brittany White & Leah Lambrakis Department of Technical Services

There is nothing more frustrating as a pet parent than when you place a bowl of food in front of your pet and they turn their nose away in rejection!  Just like humans, pets have preferences for certain types of foods, flavors, textures and ingredients.  There are many factors that drive a pet’s liking or disliking of their foods and some that may cause them to turn away from a food that they may have really enjoyed previously.  So how do pet food formulators design a diet to ensure that it is not only nutritious for our pets, but also palatable and enjoyable?  In a previous white paper, we reviewed the evaluation tools used to measure these attributes.  Our team has invested many years into understanding the drivers of palatability, and this white paper will review many of the factors that could influence the palatability of a wet pet food diet and how they may be leveraged to improve the feeding experience.

Nutrients

All animals are innately inclined to prefer certain nutrients over others as a means of protecting themselves against deficiencies.  An animal’s sense of taste can help them assess the nutrient content of food and helps protect them against eating things that might harm them.  Moisture or water content of a food plays a key role in palatability for both dogs and cats, both of which generally prefer moist foods (i.e., wet, fresh) over dry foods (kibble) as the moisture content of wet foods is more similar to fresh meat.  Since cats are obligate carnivores, meaning they require protein in their diet to thrive and survive, they are typically drawn towards foods with high protein, especially animal proteins, which ensures that they are meeting their dietary requirements. [1]  In return, cats have less preference for carbohydrates and fat, and have been demonstrated to choose a higher protein, lower carbohydrate diet when given the option. [2]  Most commercial dry foods contain high levels of carbohydrates since they are critical for successful extrusion processing, whereas wet foods and emerging fresh-cooked formats typically contain higher amounts of meat, making them naturally more palatable compared to kibble.  Unlike cats, dogs are omnivores and tend to be more opportunistic with their food selection.  Though dogs need the amino acids from protein to survive, like humans, they often show preference for foods with simple sugars and higher fat, likely as a way to ensure they are getting sufficient energy. [3]  Additionally, a review of 10 years of palatability studies found that as crude fiber of the diet increases, there is a decrease in palatability for dogs. [4]  Finally, both cats and dogs at times may show a preference towards new foods over those that they typically consume as part of their daily diet.  Called the “novelty effect,” this is believed to be an innate behavior to ensure that their overall diet is complete and balanced since it is unlikely that two diets with different flavor/aroma profiles will contain the same nutrients. [5]

Flavor and Ingredients

Cats have around 470 taste buds whereas dogs have around 20,000 and humans around 10,000. [6]  Since cats have relatively fewer taste buds compared to both humans and dogs, their ability to taste sweet, sour, salty, and bitter is significantly impacted. [7]  Like humans, both dogs and cats have a strong aversion to things that taste bitter, which encourages them to avoid things that may be toxic or poisonous. 

When it comes to palatability, not all animal proteins are created equal.  Liver is commonly used in wet pet food diets to improve their palatability.  Simmons Pet Food has demonstrated that generally higher inclusions of liver in a diet are more palatable for cats. However, for dogs, the law of diminishing returns applies as they do have a preference for liver in the diet, but higher levels do not always lead to improved palatability.  Preferences also exist among liver types for both dogs and cats as we have demonstrated that poultry and pork liver are preferred over beef liver (Figure 1).  When given the choice between various raw lamb and beef parts, cats generally preferred the liver and kidney over lung, heart, tripe and muscle meat, and preferred lamb over beef. [8]  Additionally, many animal ingredients used in the production of pet food contain bone components that naturally deliver minerals, including calcium and phosphorus, which are needed to meet the animals’ requirements.  However, the presence of bone has been shown to have a negative impact to palatability in multiple trials [4], several conducted by Simmons Pet Food. 

Figure 1. Animal liver type palatability preferences for dogs and cats (Simmons unpublished data)

Often, palatants, which are ingredient blends specifically created to improve flavor, are added to pet food formulas to improve palatability.  The composition of palatant ingredients varies depending on the source and intended use, but many are made up of a combination of animal digests, sugars, amino acids, yeasts, vitamins, minerals and other ingredients known to drive taste preferences for dogs and cats.  In dry kibble manufacturing, the palatant is typically applied to the outside of the kibble in the final stages of processing to deliver an intense flavor and aroma that attracts the dog or cat consuming the food.  Palatants are not always added to wet pet food because they are typically high in meat and already naturally palatable by design.  However, when they are added, their application is more complex because they must be mixed with the other ingredients prior to retort processing. During cooking at relatively high temperatures, such as those that occur in the retort, ingredients, including those in the palatant undergo chemical reactions producing compounds such as Maillard reaction products that will likely change the palatability of the diet for better or worse.  With this in mind, palatants designed for wet pet food applications typically contain a mixture of sugars and amino acids that then react during processing to generate flavors that are pleasing to both dogs and cats. 

Format and Texture

Flavor and nutrients are not the only factors that influence the palatability of a pet food diet.  As previously mentioned, both dogs and cats tend to prefer wet or moist diets over kibble because it is more similar to fresh meat; however, kibble is well accepted by both species.  Within wet pet food, the format (loaf vs. cuts in gravy) and texture of the food can play a significant role as well.  This can be particularly true for cats whose feeding preferences are largely driven by texture, as they tend to roll the food around in their mouth before swallowing using their vomeronasal, or Jacobson’s organ on the roof of their mouth to essentially smell their food, compensating for relatively few taste buds. [9]  Anecdotal evidence suggests that cats, when offered a cuts in gravy diet, tend to lick the gravy and leave the chunks behind.  AFB International recently performed a controlled study to evaluate the texture preferences in multi-component wet diets. [10]  To summarize this study, cats preferred gravy alone over the chunks alone or the full, multi-component diet (chunks + gravy).  They also preferred the whole diet over the chunks only.  This suggests that the presence of gravy in a wet food diet is a key driver of palatability for cats.  Similarly, Simmons Pet Food has evaluated cats’ preferences of different forms of wet pet food and found that minced and shredded style cuts in gravy is preferred over other formats including loaf.  The temperature in which a diet is served may also influence preferences.  In one study, research found that aging cats significantly preferred warmer meals compared to chilled, and room temperature food was the most preferred. [11]  Little available research exists on the impact of format and texture of wet pet food on dog palatability; however, our work suggests that they are much less sensitive to changes in texture compared to cats, likely because the food spends little time in their mouth before swallowing! 

Process

Certain process parameters such as time, temperature, and mixing can impact the overall acceptability of a diet as well.  To our knowledge, there has not been a study to directly compare the impact of different pet food processing technologies (i.e., extrusion, retort, etc.) on palatability.  Such a study would be interesting, but difficult because the ingredients used for these formats differ considerably and would influence the results of the study.  However, considering retort processing only, it has been demonstrated that temperature can impact palatability of canned cat food with a lower temperature, longer cook time process favored over a higher temperature, shorter cook time process. [12]  Simmons Pet Food has demonstrated similar results when different retort conditions were used to manufacture a canned cat food; however, in this study, the different retort conditions did not impact dog palatability.  There are many other process-related factors that may impact palatability (i.e., retort type, grind size, filling temperature, etc.), leaving us at Simmons Pet Food with plenty of opportunities for research!

Quality and Freshness

Given that dogs and even cats often appear to be attracted to rather unsavory aromas that might be found in the yard or elsewhere in the wild (i.e., carrion), it is commonly believed that their preferences for the aroma of their food is “the stinkier, the better.”  However, that couldn’t be further from the truth!  Both cats and dogs have an enhanced sense of smell because they have more receptors in their nasal epithelium as well as a vomeronasal organ in their mouth that enhances their olfactory system. [13]  Therefore, the aroma of a food has more of an impact on their acceptability of that food than it would ours.  Though cats and dogs may find them interesting, spoilage aromas are indicators that a food may be unfit for consumption, thus, just like humans, they tend to avoid spoiled food, especially when given the option to select a fresher smelling food.  We at Simmons Pet Food have research underway to investigate the formation of volatile flavor compounds during the shelf life of raw meat ingredients used in the production of wet pet food and, in turn, understand their impact on palatability for both dogs and cats.      

In closing, pet food palatability is extremely complex, and ensuring a diet is acceptable and enjoyable to cats and dogs is made even more difficult by the fact that they are not able to tell us exactly what it is they like or dislike about their foods.  Often an animals’ food preferences are established right after weaning and may impact their preferences into adulthood, [5,14] and just like us, individual pets have unique taste preferences, so it is unlikely that a single food can meet the preferences of all animals.  Finally, it should be noted that a formulation focused solely on the highest palatability may lead to increased consumption by the animal, thus the caloric density of the pet’s overall diet may need to be closely managed. 

Simmons Pet Food is committed to continued investigation of key drivers to improve wet pet food palatability in an effort to better nourish and delight the pets we love!

Our Commitment – Leading with Technical Expertise – Leah and Jarrod are here to provide guidance and insights – do not hesitate to connect with us at Simmons Pet Food, pfcomments@simfoods.com. We would love to hear from you and be part of your pet’s nutrition solution!

Literature Referenced

  1. Zaghini G, Biagi G (2005). Nutritional peculiarities and diet palatability in the cat. Vet Res Commun 29 Suppl 2:39-44.

  2. Salaun F, Blanchard G, Le Pai L, Niceron C (2017).  Impact of macronutrient composition and palatability in wet diets on food selection in cats. J of Anim Physiol Anim Nutr 101(2): 320-328.  

  3. Roberts MT, Bermingham EN, Cave NJ, Young W, McKenzie CM, Thomas DG (2018).  Macronutrient intake of dogs, self-selecting diets varying in composition offered ad libitum. J Anim Physiol Anim Nutr (Berl) 102(2):568-575.

  4. Alegría-Morán RA, Guzmán-Pino SA, Egaña JI, Muñoz C, Figueroa J (2019).  Food preferences in dogs: effect of dietary composition and intrinsic variables on diet selection. Anim (Basel) 9(5):219.

  5. Bradshaw JWS (2006). The evolutionary basis for the feeding behavior of domestic dogs (Canis familiaris) and cats (Felis catus). J Nutr 136(7 suppl):1927S-1931S.

  6. Robinson PP, Winkles PA (1990). Quantitative study of fungiform papillae and taste buds on the cat’s tongue. Anat Rec 226:108-111.

  7. Li X, Li W, Wang H, Bayley DL, Cao J, Reed DR, Bachmanov AA, Huang L, Legrand-Defretin V, Beauchamp GK, Brand JG (2006). Cats lack a sweet taste receptor. J Nutr 136(7 Suppl):1932S-1934S.

  8. Watson P, Thomas D, Hoggard A, Parker M, Schreurs N (2020).  Investigating the palatability of lamb and beef components used in the production of pet food for cats. Anim (Basel) 10(4):558.

  9. Pekel AY, Mulazimoglu SB, Acar, N (2020). Taste preferences and diet palatability in cats. J Appl Anim Res 48(1):281-292.

  10. Research and Development, AFB International (2021). Cats’ eating enjoyment informs preference for food components [White paper].
    https://www.afbinternational.com/wp-content/uploads/2022/10/Measuring-Consumption-WP.pdf

  11. Eyre R, Trehiou M, Marshall E, Carvell-Miller L, Goyon A, McGrane S (2022). Aging cats prefer warm food. J Vet Behav 47:86-92.

  12. Hagen-Plantinga EA, Orlanes DF, Bosch G, Hendriks WH, van der Poel AFB (2017). Retorting conditions affect palatability and physical characteristics of canned cat food. J Nutr Sci 6(23):1-5.

  13. Padodara RJ, Jacob N (2014). Olfactory sense in different animals. Indian J Vet Sci 2:1-14.

  14. Stasiak M (2001). The effect of early specific feeding on food conditioning in cats. Dev Psychobiol 39:207-215.

Mollie Pratt