An Immersive Look At The Role Of Lecithin In Chocolate

Cocoa origins and percentages, types of sugar and/or milk, and processing methods are not the only issues that chocolate makers must wade through with each batch. While some ingredients are selected to impart specific flavor or texture combinations, others are included for utilitarian rather than epicurean reasons. In the latter category is lecithin, an ingredient widely used by industrial chocolate manufacturers that works in minute amounts and is therefore usually listed at the very end of an ingredient list.

But how much do we know about lecithin—and its specific role in chocolate?
In food technology, lecithin is an emulsifier, a type of additive that serves many functions in processed foods. From a broader perspective, how do emulsifiers work to be so versatile in most food applications?

Food Emulsifiers: what they are and how they can be multifunctional

Emulsifiers are canonically described as substances that help stabilize two normally immiscible (not stable and homogenized after mixing) media. For example, a foam (a gas-in-liquid or -solid) or a dispersion (a liquid-in-liquid or -solid) are two different biphasic systems that can be held together thanks to the presence of an emulsifier.

Two typical naturally unstable liquid-in-liquid dispersions are water-in-oil and the reverse, oil-in-water.

An oil-in-water dispersion. The dispersed oil droplets have an obvious surface tension due to the repulsive nature of the two immiscible materials (oil and water). In the absence of an emulsifier, the natural antagonism of the two liquid phases would force the oil droplets to coalesce, i.e. to attract the closer oil droplets to form larger ones, resulting more stable for having reduced surface tension in relation to increased volume.

Emulsifiers, because of their amphiphilic properties—the heads of their molecular structure are hydrophilic (water-loving) and the tails are lipophilic (fat-loving)—facilitate the energetic interactions between the mutually repulsive water and oil phases by reducing their surface tension and homogenizing the dispersion.

Molecules of an amphiphile that stabilize oil-in-water and water-in-oil emulsions. Examples of oil-in-water emulsions: milk, mayonnaise. Examples of water-in-oil emulsions: butter, margarine.

In numerous food products, the benefits of emulsifiers are evident as they manifest themselves as:

  • Stability of condiments against phase separation, preventing the oil and water from separating during production, distribution, or storage,
  • Improved texture and longer shelf life in baked goods by complexing starch and protecting it from retrogradation and staling,
  • Improved whipping properties and prevention of ice crystal growth in ice cream through better incorporation of air and binding of free water molecules susceptible to crystallization, both of which have the effect of lowering the final freezing point,
  • Enhanced anti-spatter properties in margarines and frying oils by preventing gravity from returning spattered fat droplets to the hot pan.

One of the most widely used and appreciated emulsifiers for achieving many of the above stability functions in a food product is undoubtedly lecithin. So, to get back to its identity, let’s take a closer look at lecithin.

Lecithin in the Food Industry: History, Market, and Production

Lecithin (from the Greek lékithos, “egg yolk”) was first isolated from egg yolk in 1845 by French chemist and pharmacist Théodore-Nicolas Gobley—the same scientist who would discover vanillin as the characteristic flavoring agent of natural vanilla about a decade later.
Gobley demonstrated the presence of lecithin in a wide variety of biological materials, focusing his studies on tissues of animal origin. He found that biological lecithin is a mixture of bipolar phospholipids that perform essential physiological functions such as stabilizing cell membranes and facilitating metabolic activity in human organs (brain, blood, liver, etc.).

Schematic diagram of a phospholipid and view of a phospholipid bilayer in a cell membrane. Note that cell membranes consist of two opposing layers of phospholipids, while emulsions have only one layer, called a micelle (see previous image).

The earliest known reference to the presence of lecithin, even in plants such as soybeans, dates back to 1889 in Switzerland, where the legacy of a German chemist named Ernst Schulze would mark Germany as the leading European center for the industrial development of food-grade lecithin.
The first patent for the use of soy lecithin in chocolate was filed in 1930 by Hansa-Mühle GmbH in Hamburg, which later began importing soybeans as a raw material from the prolific United States and selling the finished ingredient back to American chocolate manufacturers.

Friedrich Hülsmann, an advertising manager at Hansa-Mühle in the 1930s, designed and photographed this booth for a trade show in Frankfurt, Germany, with a cheeky slogan that promoted foods with lecithin as “power food.”

Today, the raw materials from which vegetable lecithin can be extracted have never been so diverse: not only soybeans, but also rapeseed, oat, and sunflower seeds. Despite this diversity, soybeans remain the most productive source for lecithin production.

Organic soy lecithin is the cleaner answer to conventional soy lecithin, with producers certifying to steer clear of any questionable GMO practices.

Dried soybeans

Due to strict EU requirements to declare the presence of allergens and genetically modified organisms (GMOs) in foods, the food industry is gradually switching to allergen-free and GMO-free lecithin sources, such as sunflower lecithin, in an effort to educate consumers.

Sunflower seeds

In addition, sunflower lecithin has the same rheological properties as soy lecithin with only a slight increase of about 0.1%.

Rapeseed sources of lecithin, on the other hand, are marginalized for the presence of unhealthy trans fatty acids in the composition of erucic oil, of which rapeseed is naturally rich. Healthier patterns for the extraction of lecithin from rapeseed are envisioned in the low-erucic GMO canola variety, although it raises similar concerns already seen for non-organic soy lecithin.

Moreover, recently, the European Food Safety Authority (EFSA) Panel authorized oat lecithin for use as a new food additive in the food category of cocoa and chocolate products.

Contrary to popular belief, not all lecithin is created equal.
Commercial lecithin comes in different grades and forms (oiled and deoiled) that are suitable for specific food applications to achieve the desired dispersibility properties. Specifically, fluid (oiled) lecithins are recommended for a food where the fat phase predominates over the water phase, as they tend to disperse more readily in fat-based dispersions (like chocolate); whereas deoiled (powdered) lecithins are recommended for a food where the water phase predominates over the fat phase, as they tend to disperse more readily in water-based dispersions.
The emulsifying properties of different types of lecithin are conventionally expressed by a Hydrophilic-Lipophilic Balance (HLB) index.

Hydrophilic-Lipophilic Balance (HLB) of different lecithin grades. Standard Fluid Grade lecithin contains about 36% triglycerides. Deoiled Lecithin has a granular or powdered form, with its triglycerides and free fatty acids removed. The fractionation process to make refined deoiled lecithin takes advantage of the different solubility of phospholipids in the polar solvent. Lecithin can be further modified through hydrolization and enzymatic reactions to make it more suitable for oil-in-water emulsions.

The production of standard liquid lecithin can be obtained mechanically from the raw material through a natural process that involves first cleaning and pressing the oilseeds and then degumming the oil sludge at 70°C, followed by centrifugation to separate the crude oil from the water component.
Selective chemical extraction of lipids (oil) from lecithin using solvents such as hexane, acetone, or alcohol is only necessary if the desired form of lecithin is deoiled. Clarifying this distinction is critical because some detractors of lecithin in chocolate incorrectly claim that this ingredient contains solvents that are harmful to human health.

Standard fluid sunflower lecithin. Since chocolate is a lipophilic medium, non-deoiled lecithin is preferred.

Simply put, the type of lecithin used for chocolate is not as highly processed. The more lipophilic (oily) the lecithin, the less processed it is. A 4 point HLB lecithin is generally the standard for chocolate production.

After understanding why there are different types of lecithin available on the market today, what is the primary cost/benefit analysis that justifies the use of an emulsifier in chocolate?

Chocolate’s flow behavior: why it’s important to know before you can control it

From a physical point of view, chocolate can be described as a suspension, i.e. a special type of solid-in-liquid dispersion consisting of non-fat solid particles (cocoa solids, sugar crystals and, possibly, milk powder particles) dispersed in cocoa butter as a continuous (liquid) fat phase.

What happens when chocolate moves as a solid-in-liquid suspension?

In rheology—the science that studies the deformation and flow of solids and liquids under the influence of mechanical forces—molten chocolate is a shear-thinning, non-Newtonian fluid, which indicates an “imperfect” liquid substance with a dispersed solid phase whose viscosity (resistance to flow) decreases with increasing stress over time.
While perfect Newtonian substances such as water and milk have a constant viscosity regardless of shear rate (speed), non-Newtonian substances such as chocolate have different viscosities at different shear rates. Therefore, measuring the viscosity at a single shear rate once or twice during the chocolate manufacturing process does not provide sufficient information to predict and then control the flow behavior of the chocolate, which is essential to differentiate between processes that occur at different shear rates, such as molding, vibrating, and enrobing.

Viscosity behavior differences between a non-Newtonian fluid (standard milk chocolate) and a Newtonian fluid (standard milk). Note how standard milk chocolate, unlike standard milk, exhibits variable and dependent viscosity with shear rate.

With large economies of scale, factoring in these variables is paramount to optimizing product consistency for profit margins. Production costs will therefore be closely linked to the ability to achieve and maintain consistent product quality—ensuring customer satisfaction and loyalty—without the need to adjust the recipe from batch to batch.
If defining the viscosity of a chocolate for a specific recipe requires a high degree of precision in measurement and calculation, knowing the exact viscosity required ensures that as little cocoa butter—the most expensive input in chocolate production—as possible is used.
For a major chocolate manufacturer, there are significant profits to be made by developing more cost-effective recipes with minor strategic changes. A seemingly insignificant 4% saving in cocoa butter—the maximum amount that can be replaced by a tenfold lower amount of lecithin (0.4%)—has the power to deliver substantial bottom-line effects in the order of 100,000 EUR/USD for the production of 1,000 tons of chocolate!
With such clear returns, it’s no wonder that the major chocolate industry is leaning toward cost-stable emulsifiers as a viable alternative to cost-inefficient cocoa butter. Emulsifiers such as lecithin not only reduce costs, but also provide the chocolate manufacturer with the ultimate tool to control viscosity—and therefore consistency—during production.

So, now that we have understood the main reason why emulsifiers make sense for a large-scale chocolate maker, how exactly does lecithin work when added to chocolate?

Lecithin addition: how it helps chocolate production efficiency

Take your average mass-produced chocolate. It is likely to have a low cocoa mass content (the natural composition of cocoa solids + cocoa butter obtained by pressing cocoa beans), with a total fat content (cocoa butter + milk fat) not exceeding 32%—which is the recommended minimum fat content for acceptable chocolate fluidity. The remaining lion’s share will consist mostly of added dry solids (namely sugar, cocoa powder, and/or milk powder) forced to flow in an artificially-minimized fat phase.
Scrimping on the essential cocoa butter content will inevitably come back to haunt chocolate production down the road in the process, as the need to evenly disperse the high solids dry phase in the low fat liquid phase must be balanced against the need to avoid achieving a coarse particle undesirable to the consumer’s palate. To solve this problem, our typical big chocolate manufacturer will try to maximize two aspects during production:

  1. to process the chocolate so as to obtain a very fine particle size, the granulometry of which cannot be perceived when the chocolate is tasted—usually down to about 18‒20 µm;
  2. to evenly disperse the resulting fine solid chocolate particles in a low-cost, fat-reduced chocolate medium with the help of lecithin.

While a fine particle size is desirable for sensorial reasons, the newly developed chocolate conformation high in solid particles is not without technical drawbacks, as it may risk affecting a lesser known value relevant to chocolate flow, referred to as “yield value.”
While plastic viscosity (PV) is the force required to maintain a constant flow in the chocolate mass (important for processes with medium to high shear rates, such as enrobing), yield value (YV) is the force required to initiate flow in the chocolate, which affects low shear rates, particularly during molding and vibrating processes—then YV is even more critical than PV when it comes to chocolate bars.

Lecithin comes to the rescue to positively influence the yield value in the production of minimally fat-reduced and fine-particle chocolate. Unlike cocoa butter, which has no emulsifying properties, lecithin is chosen for its functional ambivalence as a surfactant. The hydrophilic heads of its phospholipid moieties interact with the sugar particles, while the lipophilic tails float in cocoa butter—and any additional free fat from dairy ingredients.

Lecithin molecules surrounding sugar particles in the continuous fat phase in chocolate. If we look closely at the conformation of the polar interactions of lecithin with the non-fat solids of chocolate (such as sugar in this example) and the dispersing fat phase of chocolate, it reminds us exactly of what happens in an emulsifying stabilization process between the aqueous and fat phases in an immiscible solution to conceal their naturally-repulsive surface tension. Even if the chocolate medium contains no water, it can be considered a water-in-oil dispersion, where “water” represents the hydrophilic solids dispersed in the fat phase.

The physical interactions of the lecithin phospholipids on the sugar particles create spatial “microgaps” between the sugar particles and the fat phase, reducing the mechanical friction of the particles in the low-fat dispersion and thus the energy required to keep the chocolate mass within optimal flow properties.

When everything seems to be working like a charm for the newly improved yield value, a second obstacle can potentially negate the benefits gained by using lecithin. In chocolate manufacturing, the finer the solid particles dispersed in a low-fat chocolate, the greater the amount of lecithin required due to the increasing surface-to-volume ratio of the smaller particles.

To better explain such a seemingly tricky concept with comparative visuals, I created the following prospectus from scratch:

Differences in surface area to volume ratio. Particle A has a surface-to-volume ratio three times greater than particle B, even though its radius is one-third that of B, and therefore requires more input (emulsifier) to be wetted (coated and lubricated) during the process.

However, food technologists have observed during the chocolate manufacturing process that adding more lecithin beyond a certain threshold hides an unexpected drawback: it can lead to an irreversible inconvenience known as the “thickening effect.” This phenomenon occurs when the excess lecithin interacts with the lecithin molecules already added and promotes the formation of reverse micelles, which not only stop reducing the yield stress but start increasing it after a dosage of 0.4% is exceeded.

Bilayer of lecithin around a sugar particle. When an excess of lecithin is added above a certain threshold, bistrate complexes (reverse micelles) of lecithin are formed around the dry solid particles of the chocolate medium, which, by leaving the lipophilic part of the lecithin out of contact with the fat phase, prevent the solids suspended in the matrix from flowing canonically.

Dosing lecithin in chocolate at around 0.4% usually provides a tenfold (4%) saving in cocoa butter. Chocolate tolerates a dosage of 0.4% soy lecithin, after which the yield value begins to gradually increase, producing the opposite desired effect and making the chocolate thicker.

Yield value of soy lecithin in chocolate

To overcome the drawbacks of lecithin over the years, the mainstream chocolate industry began looking for more reliable emulsifying solutions that could outperform lecithin in achieving optimal flow properties without sacrificing processing standards.

Lecithin Alternative Emulsifiers: why they were developed for the industrial chocolate industry

Since any residual moisture in the chocolate evaporates during the early part of conching, an initial expedient to avert the thickening effect in chocolate is to add lecithin only toward the end of conching. Coating the surface of particles that are not completely dry with lecithin—as well as with cocoa butter—would otherwise cause moisture to remain trapped in the chocolate mass.
In the manufacture of milk chocolate, other ingredients such as milk phospholipids may have surface-active properties similar to those of lecithin and thus further contribute to the thickening effect. In synergy with lecithin, milk phospholipids may ultimately increase the yield value of the chocolate.
Crumb chocolate (chocolate made from vacuum-dried milk and cocoa) is even more sensitive to the presence of lecithin. Cadbury’s first crumbly milk chocolate, produced in the 1960s, tended to develop unwanted “grass” or “hay” flavors during storage. For this reason, the British company sought a new alternative to lecithin called ammonium phosphatide (AMP), also known as Emulsifier YN.
However, the first version of AMP was based on rapeseed oil, which was high in the unhealthy trans fat erucic acid. Fast forward 50 years and an improved version of AMP is made from refined sunflower oil and glycerin by Danish emulsifier manufacturer Palsgaard A/S.
Compared to soy lecithin, AMP has a number of significant advantages, such as a more consistent phospholipid composition, a completely bland taste, and better flow properties, as it does not have an unwanted thickening effect, but continues to reduce plastic viscosity while keeping yield value at the same level even at higher dosages.

Effect of AMP on plastic viscosity and yield value compared to soy lecithin in a standard chocolate formulation. AMP can extend the cocoa butter savings of chocolate formulated with soy lecithin by an additional 2‒3%, for a total potential savings of 6‒7%.

Another widely used lecithin alternative emulsifier in chocolate manufacturing is polyglycerol polyricinoleate (PGPR), which is obtained by polycondensation of castor oil and glycerin. PGPR does not have a large effect on plastic viscosity, but it can reduce the yield value by 50% at 0.2% or eliminate it at about 0.8%, turning chocolate into a quasi-Newtonian fluid so that it flows more easily and settles quickly when poured into the mold.
Industrial chocolate manufacturers typically use PGPR as a lecithin coadjuvant to achieve a desirable yield value and plastic viscosity, especially when the chocolate has too many fine particles to coat or when too much lecithin has been added.

Does the Fine Chocolate Industry stand up against or for lecithin?

If the mainstream chocolate industry has found the use of lecithin and lecithin-alternative emulsifiers so economically attractive for almost a century, what is the current position of the fine chocolate industry?

Different fine chocolate brands have different experiences and interests regarding the use of lecithin in their products.

An overwhelming majority of fine chocolate brands, represented by the growing wing of producers who would describe their production as “artisanal,” “handmade,” “small batch,” exclude lecithin regardless of any cost/benefit assessment, mainly for branding reasons, as today’s consumer demands fewer and fewer ingredients and an accessible language on a product label. In addition, efficient machinery specifically designed for the production of fine chocolate facilitates the demand of a brand that prefers not to include lecithin in its philosophy.

On the other hand, luxury chocolate brands that include lecithin in their products, while still striving for an aura of authenticity, naturalness, and transparency, opt for more sustainable and cleaner alternatives such as sunflower lecithin or, at most, organic soy lecithin.

Since lower amounts of lecithin (around 0.1‒0.2%) are typically required in a fine chocolate product due to its naturally abundant cocoa butter content (well over 32%)—and, conversely, much lower levels of dry solid particles of added sugars—there are some good reasons to support the lecithin partisans. Since flavor is the most important aspect for a trusted fine chocolate brand, limiting cocoa butter additions to 4‒6% and using lecithin for further viscosity adjustments proves to be a smart integrated strategy to avoid “diluting” the intrinsic flavor profile of a single-origin chocolate product, as well as to avoid making its mouthfeel too fatty.
Fine chocolate brands can also rely on the functional role of lecithin to standardize the production of certain problematic lines, i.e. filled chocolate products are made more stable against susceptibility to fat bloom, migration, or oxidation, while plain chocolate products rely on more efficient production speed and invest the time saved in other business activities to increase market share and brand reputation.

As long as the choice of one fine chocolate brand over another remains the ultimate decision of consumers and customers, fine chocolate brands that produce products with superior taste and standards to mass-produced products will continue to use different production methods and drive innovation in the global chocolate industry for years to come, with or without lecithin.