The hunt continues for alternative ingredients to fuel the ever-increasing demand for new and different products to entice the discerning pet owner. Whether to fill the void after we dodge the negative perceptions of corn, soy, wheat, beef and by-products or as a matter of satisfying the burgeoning array of “limited ingredient” and “no grain” diet choices, finding the perfect new and different ingredient is always a challenge—especially when dietary protein levels are edging upward, perceived overages in minerals have been tightened and the availability of process functionality has declined.
To add more protein by simply increasing meat, poultry or fish meals isn’t the answer for nutrient balance or functionality. Before the market got finicky, we could incorporate soy protein concentrate or corn gluten meal to fill the gaps; but, for the most part, these ingredients are now on the “no” list. So, today another option is needed.
This is where we are seeing a growing popularity in the use of ingredients like pea proteins. Whether pea protein concentrate or isolate, this ingredient is finding its way into a host of different petfoods in virtually every product format—from extruded to wet foods to injection-molded treats. Pea protein certainly sounds wholesome, but are using these ingredients a good practice?
Pea proteins are derived from the yellow or green field pea (Pisum sativum). Most commercial pea proteins are produced in Canada and Western Europe, with some Asian sources coming into the market in recent years. The proteins are produced by either dry or wet processes.
The dry process produces pea protein concentrate. The peas are finely ground and then classified according to mass with moving air. This so-called air classification relies on the differing density of particles rich in starch from those rich in protein. The lightest fraction contains mostly seed hulls and is collected and merchandised as pea fiber. As it has been described, the heavier fraction is finer and contains more protein, and the medium-coarser fraction is rich in starch.
Pea protein concentrates contain around 45–55% protein, with fat and ash around 5–6% and dietary fiber of 15–20%. This process can also concentrate the trypsin inhibitor, oligosaccharides and saponins native to the pea. These compounds can influence taste and utilization.
The wet process produces pea protein isolate. Exact details of this process are closely guarded by the manufacturers, but essentially, the peas are ground and washed to produce various fractions containing starch and soluble sugars, bran and protein. Depending on wash pH, salt, enzyme hydrolysis and (or) solvent used, the protein fraction may be more than 80% protein (dry basis) and the starch, oligosaccharides and phytate content reduced to insignificant levels.
The wet, protein-rich fractions are drum- or spray-dried and sold as a powder. Besides retaining their favorable amino acid profile and diminished anti-nutritional properties, these isolates have interesting food functionalities such as foaming, binding and texturizing capabilities.
The advantage or disadvantage between the concentrate and isolate used in a petfood generally rests on protein content, price and availability. Nutritionally, the amino acid profile of each is similar when expressed as a percentage of the protein, with methionine and tryptophan being the first limiting amino acids. Conversely, pea proteins contain a surfeit of essential lysine. Because of this incomplete amino acid profile, the amounts included in the diet are commonly limited to supplemental or complementary roles of less than 10–12%.
Pea proteins are truly new ingredients to the petfood scene if the lack of published nutritional studies is any barometer. Research about dogs or cats being fed pea proteins is not yet readily available. Some recent work in which pea protein concentrates were fed to other species can be found. Unfortunately, performance and digestibility data from uncooked pea protein concentrates fed to pigs and chickens are not directly applicable because of the influence from protease inhibitors and other anti-nutritional compounds that would otherwise be neutralized by the thermal processes typically used to produce petfoods.
However, if you are willing to think out of the species box, extruded diets containing pea protein concentrates fed to trout have been shown to compare favorably to fish meal. While trout are a carnivorous fish and the results could be loosely considered applicable to dogs and cats, clearly there is need for additional information, especially regarding limitations on amount, effects on palatability, digestion or elimination and whether they influence food sensitivity.
As a frame of reference, pea proteins are similar in many aspects to soy proteins. Like those concentrates, pea proteins retain their functionality and can be used in a wide array of capacities. For example, pea protein in a pet diet expands well and yields a durable kibble during normal extrusion. In addition, pea protein isolates can be “texturized” through extrusion to create products with a consistency and appearance similar to meat products. Concentrated pea proteins have also found use in injection-molded chews and treats. Incorporating them into these applications does not appear to be an issue up to a certain level.
Pea proteins have a bland flavor and aroma that can take on the characteristics of the remainder of the diet. The only challenge to this is dilution of flavor. In cat diets especially, elevated levels of pea protein (exceeding approximately 15%) can compromise the palatability relative to diets rich in meat proteins.
Acceptance of pea proteins by pet owners seems to be fairly high but not to the level of meat proteins. Very few customer service questions arise about this ingredient, but that may simply be due to its recent entry on the scene.
Acceptance by regulatory agencies isn’t as straightforward. In Europe and other regions of the world, there are no indications that pea proteins are unacceptable. In the Association of American Feed Control Officials’ Official Publication (2012), peas can be found in the index but are not defined, and pea proteins do not even merit mention. This is odd given how ubiquitous peas have been historically in foods and animal agriculture. Supposedly pea protein manufacturers are working to fill this regulatory void. Meanwhile, by most reports, regulatory officials have been prudent and not made significant issues of this ingredient’s use.
In the end, pea proteins, whether concentrate or isolate, are a nice ingredient tool for nutritional fortification today and, with their positive consumer perception and food functionality, appear to be opportune for innovation in petfoods and treats in the future.
Read more columns by Dr. Aldrich at www.petfoodindustry.com/ingredientissues.aspx.
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