Lecithin is an ingredient that we see periodically on petfood labels, most commonly on canned foods. It is included for a "functional food" purpose but has some nutritional benefits, as well. The ingredient name is pronounced "less eh thin" so you'd think it would have some appeal on the label; however, in most discussions with marketing folks they either have never heard of it or have little interest in exploring it further. Maybe they need to take a closer look at this ingredient and where it might prove beneficial in petfood production and pet nutrition and health.
To start, lecithin is already defined and readily accepted by feed control officials. The Association of American Feed Control Officials (AAFCO) 2013 Official Publication lists this ingredient twice: First in the Official Feed Terms section as "Lecithin. (Part) A specific phospholipid. The principal constituent of crude phosphatides derived from oil-bearing seeds;" second under US Food and Drug Administration (FDA) Regulation 582.1400 (IFN 8-08-041), where it is classified under the food additives amendment as a "Stabilizer" with no limitations or restrictions on use. Under the EU system, lecithin is listed as number E322.
Commercially, lecithin is a very general term for a group of polar lipids, specifically phospholipids, derived from water-degummed vegetables oils in contrast to the "chemical" name for lecithin that would narrowly define it only as the phospholipid phosphatidylcholine. For the sake of this article, the more liberal use of "lecithin as a food ingredient" will be used in which all food phospholipids are lumped into the category of lecithin.
There are several phospholipids to consider; for starters, all living cells, animal and plant, contain phospholipids. In animals, these phospholipids are concentrated in the brain, liver and kidney. Egg yolk, milk and brain tissue have served as commercial sources of phospholipids in the past. They contain phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI), with lesser quantities of phosphatidic acid (PA), phosphatidyl serine (PS), glycolipids, ceramides and sphingomyelin.
In plants, phospholipids are most concentrated in the seeds, nuts and grains. The most common commercial sources are derivatives extracted from soybean, corn, cottonseed, rapeseed/canola, sunflower and peanut oils. The primary phospholipids found in plant sources are PC, PE and PI, with lesser quantities of PA, PS and glycolipids. Today, the bulk of commercial lecithin available to the human and petfood industries is derived from soybean oil.
Lecithin is produced from hexane-extracted crude oil from oil seeds such as soybeans by a process called water degumming. The oil is heated to 70-80ºC, and then water is added to an amount approximately equivalent to the amount of phospholipid content (~1-2%) then agitated vigorously, followed by centrifugation to separate the oil from the lecithin emulsion. This emulsion is then dried under vacuum or over thin film evaporators to remove the water. The resulting viscous fluid may be bleached to remove the naturally-occurring brown color derived from plant pigments, deodorized to remove off-odors and (or) further refined to remove residual oil.
It may also be blended with a parent oil (e.g., soybean) to thin its phospholipid content and (or) improve handling. It is sold under a number of different specifications depending on the target application. One of the more confusing specifications is the "HLB" number which is a measure of the hydrophilic-lipophilic balance of the final preparation.
To explain, lecithin can act as an emulsifier, surfactant, wetting and dispersing agent, antioxidant, release agent, viscosity modifier, and lubricant. This is due to the hydrophilic-lipophilic (amphipathic) properties of the molecule. In essence, lecithin, the phospholipid molecule, contains two long-chain fatty acids and a phosphodiester bound choline, ethanolamine or inositol all esterified to glycerol. This architecture creates a nonpolar fatty acid end which is lipophilic (or fat-loving) and a zwitterionic (dipolar) phosphodiester which is hydrophilic (or water-loving) and charged.
In other words, this molecule has a split personality where it behaves like a fat and water at the same time. This special property allows it to work at the surface of oil and water making it is the magic ingredient that keeps mayonnaise from separating.
In petfood, it is used in canned foods where the target is to prevent or reduce the incidence of "fat-caps" in loaf products and fat globs in chunks and gravy products. In this application, lecithin is incorporated at 0.5% to 2% of the formula depending on the type and amount of fat. In dry foods, lecithin incorporated into the formula has been reported to reduce motor load, improve throughput, decrease clumping and enhance starch gelatinization (Russett, 1998; Technical bulletin LECT-T-43, The Solae Company).
If repeatable, this would be a significant help in high-meat formulas and those with a great deal of fat. One can surmise that in these situations lecithin might work by improving fat blending into the mix when steam (water) is being used to heat the product, and further trap the fat in water-in-oil emulsions, thereby reducing the lubricating effect of the fat in the barrel extruder. In baked products, lecithin has been tried as a release agent to aid product separation from the mold. In all cases, lecithin use is typically at less than 2%.
Using lecithin beyond this 2% level can lead to a bitter taste which is typically unacceptable to the pet and can lead to palatability issues and rejection. This is unfortunate in some respects because lecithin can be nutritionally beneficial. First and foremost it can serve as a viable source of the essential water-soluble vitamin choline (see Petfood Industry, August 2008). The bioavailable choline content in commercial lecithin has been reported to be 2% and 3.5% for fluid and de-oiled (powdered) lecithin, respectively (Emmert et al., 1996).
In addition to providing choline and serving as a precursor to acetylcholine (the neurotransmitter), phosphatidylcholine provides structural stability to cell membranes and serves as a membrane constituent for lipoproteins in their fat transport role (Miller, 2002). It can also influence inflammatory processes, neurological development and decline, and cardiovascular health and metastatic disease (Kullenberg et al., 2012).
This merely scratches the surface regarding the topic of lecithin and phospholipid use in food and nutrition applications. It is an interesting ingredient that probably has a bigger role to play in petfoods if fully evaluated. Research into its direct effects on nutrition and health of dogs and cats would be warranted, as well as additional exploration regarding where it might improve some of the challenges faced in production of the modern food forms currently being developed for our pets.
