Cacao origins and percentages, types of sugar and/or milk, and processing methods are not the only hassles that chocolate makers have to wade through at every single batch. While some ingredients are selected for imparting specific flavor or texture combinations, others are included to carry out utilitarian rather than epicurean reasons. To the latter category belongs lecithin, an ingredient widely used by industrial chocolate manufacturers, working at just minute amounts, and, therefore, usually declared at the very end of an ingredients 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 performing a multi-purpose function in processed foods. In a broader view, how do emulsifiers act to be so versatile in most food applications?
Food emulsifiers: what they are and how they can be multi-functional
Emulsifiers are canonically described as substances that assist in the stabilization of two mediums normally immiscible (not remaining stable and homogenized after being mixed.) For example, a foam (a gas-in-liquid or -solid) or a dispersion (a liquid-in-liquid or -solid) are two different biphase systems that can be kept together thanks to the presence of an emulsifier.
Two typical naturally-unstable liquid-in-liquid dispersions are water-in-oil and its reverse oil-in-water.
The dispersed oil droplets present evident surface tension due to the repulsive nature of the two immiscibles (oil and water). In absence of an emulsifier, the natural antagonism of the two liquid phases would force the oil droplets to coalesce, that is to attract the closer oil droplets to form larger ones which result more stable for having reduced surface tension in respect to increased volume.
Emulsifiers, for possessing amphiphilic properties—with heads of their molecular structure being hydrophilic (water-loving) and tails lipophilic (fat-loving)—ease the energy interactions between the mutually repulsive water and oil phases by reducing their surface tension and homogenizing the dispersion.
Oil-in-water emulsion examples: milk, mayonnaise. Water-in-oil emulsion examples: butter, margarine.
In numerous food products, the perks provided by emulsifiers are conspicuous as they manifest as:
⠀• condiments’ stability against phase separation, preventing the oil and water from separating during production, distribution, or storage,
⠀• enhanced texture and prolonged shelf-life in baked goods through the complexation of starch, protecting it from retrogradation and stalation,
⠀• improved whipping properties and prevention of ice crystal growth in ice cream by better incorporating air and binding free water molecules susceptible to crystallization, which both have the effect of depressing the final freezing point,
⠀• reinforced anti-spattering properties in margarines and frying oils by preventing gravity from bringing the spattering fat droplets back into the hot pan.
One of the most used and appreciated emulsifiers for obtaining many of the above-mentioned stability functions in a food is definitely lecithin. So, coming back to its identity, let’s investigate lecithin with a closer glance.
Lecithin in the food industry: history, market, and manufacture
Lecithin (from the Greek lekithos, “yolk”) was first isolated from egg yolk in 1845 by the French chemist and pharmacist Théodore-Nicolas Gobley—the same scientist who would discover vanillin as the characterizing flavor agent of natural vanilla circa a decade later.
Gobley demonstrated the presence of lecithin in an ample variety of biological matters, focusing his studies especially on animal-origin tissues. He found out that biological lecithin was a mixture of bipolar phospholipids performing essential physiological functions, such as stabilization of cell membranes and facilitation of metabolic activity in human organs (brain, blood, liver, etc.).
To note how cell membranes are made up of two opposite layers of phospholipids, while emulsions have only one, called micelle (see previous pic).
The earliest known reference to the presence of lecithin even in plants such as soybeans dated back to 1889 in Switzerland, where the legacy left by a German chemist named Ernst Schulze would then mark Germany as the leading European hub for the industrial development of food-purpose lecithin.
The first patent for the application of soy lecithin to chocolate was filed in 1930 by Hansa-Mühle, which would later start importing soybean as a commodity from the prolific United States and selling back the finished ingredient to American chocolate makers.
In modern days, the raw materials from which plant-based lecithin can be extracted have never been so variegated: not only soybeans, but also rapeseeds and sunflower seeds. Albeit this diversity, the higher-yielding source for the production of lecithin still is soybean.
Asia-Pacific is projected to be the largest consuming region of soy lecithin (contained in many convenience foods) for the next years, even though it is the United States that have been leading the global market production of soybeans and soybean lecithin since the end of World War II.
Organic soy lecithin is the cleaner reply to conventional soy lecithin, whereas producers certify to steer clear of any questionable GMO practices.
Because of strict EU requirements to declare any addition of allergens and genetically modified organisms (GMOs) in foods, a gradual shift to allergen- and GMO-free sources of lecithin, such as sunflower lecithin, is taking place in the food industry who cares about the informed consumer.
Moreover, sunflower lecithin displays the same flow functionalities of soy lecithin at just a lighter increase of about 0.1%.
Rapeseed sources for lecithin, instead, 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-variety canola, though it raises similar concerns already seen for non-organic soy lecithin.
Contrary to popular beliefs, not all lecithin is created equal.
Commercial lecithin has different grades and forms (oiled and deoiled), suitable for specific food applications to achieve desired dispersibility properties. In particular, fluid (oiled) lecithins are recommended for a food with the fat phase prevailing over the water phase, as they tend to disperse more readily in fat-based dispersions; whereas deoiled (powdered) lecithins are recommended for a food with the water phase prevailing over the fat phase, being more easily soluble in water-based dispersions.
The emulsification properties of lecithin at different grades are conventionally expressed with a Hydrophilic-Lipophilic Balance (HLB) index.
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 manufacture of standard liquid lecithin can be obtained from the raw material mechanically through a natural process, which first cleans and presses the oil seeds and then water-degums the oil sludge at 70°C, following centrifugation to separate the raw oil from the water component.
The selective chemical extraction of lipids (oil) from lecithin with solvents, such as hexane, acetone, or alcohol, is necessary only when the desired lecithin form is deoiled.
Such distinction is pivotal as, for chocolate making, a 4-point HLB grade lecithin is generally the standard.
Since chocolate is a lipophilic medium, non-deoiled lecithin is the option.
In simple terms, the type of lecithin used for chocolate is not that heavily processed as food fearmongers mistakenly divulge. The more lipophilic (oily) the lecithin, the less processed.
After realizing why different types of lecithin are available on today’s market, what is the primary cost/benefit analysis justifying the use of an emulsifier in chocolate?
Chocolate’s flow behavior: why it’s essential to know before controlling it
From a physics standpoint, chocolate can be described as a suspension, that is a particular kind of dispersion consisting of nonfat solid particles (cocoa solids, sugar crystals and, eventually, 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 fluids 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 (the resistance to flow) decreases with increased stress over time.
While perfect Newtonian substances, such as water and milk, have constant viscosity, independent of shear rates (speeds), non-Newtonian substances like chocolate have different viscosities at different shear rates. As such, measuring single-shear rate viscosity once or twice throughout the entire chocolate-making process does not provide sufficient information to predict—and, then, control—the chocolate’s flow performance, fundamental to distinguish among processes occurring at different shear rates, such as molding, vibrating, and enrobing.
In large economies of scale, factoring these variables are paramount to optimize product consistency against profit margins. Production costs will, therefore, be closely tied to the ability to achieve and maintain consistent product quality—securing customer satisfaction and loyalty—without the need to adjust recipe batch after batch.
If defining a chocolate’s viscosity for a specific recipe requires high precision with measurements and calculations, knowing which exact viscosity is needed makes it possible to ensure that as little cocoa butter—the most expensive input in chocolate production—is used as absolutely necessary.
For a large chocolate maker, substantial gains are in fact possible from developing more cost-effective recipes with minor strategic changes. A seemingly irrelevant 4% cocoa butter saving—the maximum amount interchangeable with a tenfold lower amount of lecithin (0.4%)—has the power to deliver substantial bottom line effects in the order of EUR/USD 100,000 when producing 1,000 tons of chocolate!
With such clear earnings, it’s no wonder if the big chocolate industry leans toward the cost-stable emulsifiers as a viable alternative to the cost-inefficient cocoa butter. Emulsifiers like lecithin not only cut costs, but also offer the chocolate manufacturer an ultimate tool to control viscosity—and, consequently, reach consistency—during production.
So, now that we have understood the main reason why using emulsifiers is convenient for a large-scale chocolate manufacturer, how does the lecithin specifically work when added to the chocolate?
Lecithin: how it aids efficiency in chocolate production
Take your average bulk-made chocolate. It will likely be characterized by a low cocoa mass content, whereas cocoa butter won’t surpass a 32%—that is the minimum recommended amount of fat to make chocolate fluidity acceptable. The remaining lion’s share will mostly be consisting of dry solid components (namely sugar, cocoa powder, and, eventually, milk powder), compressed to the marrow and forced to flow in a depleted fat reservoir.
Cutting corners on essential cocoa butter percentages will inevitably lead to pay a fee in chocolate production down the road, as the necessity to evenly disperse the high-in-solids dry phase in the low-fat liquid phase has to be balanced with the necessity to avoid achieving a coarse particle, undesired for the consumer’s palate. To thwart the issue, the big chocolate manufacturer then tries to maximize two aspects during production:
⠀• to work the chocolate as to reach a very fine particle size, whose granulometry cannot be perceived when tasting the chocolate—usually up to about 18-20 µm;
⠀• to disperse the achieved highly-fine particles in the chocolate mass, tapping into the aid of lecithin.
As a fine particle size is desired for sensory reasons, the newly-engineered chocolate conformation high in solid particles is yet no void of technical drawbacks, as it may risk affecting a less-known value relevant to chocolate’s fluidity, reported as “yield value.”
While Plastic Viscosity (PV) is the force needed to maintain a constant flow in the chocolate mass (important for processes at medium to high shear rates, such as enrobing), Yield Value (YV) is the force needed to initiate flow in the chocolate, affecting the low shear rates, particularly during molding and vibrating processes—then, YV is even more critical than PV when it comes to chocolate bars.
To positively intervene on the yield value, lecithin comes to the rescue for the production of the minimally-fat-reduced and finely-particle-sized chocolate.
Unlike cocoa butter—which has no emulsifying properties—lecithin is opted in favor thanks to its functional ambivalence as a surface-active agent. The hydrophilic heads of its phospholipid components interact with the sugar particles, while the lipophilic tails fluctuate in the cocoa butter—and additional free fat from eventual dairy ingredients.
Even if the chocolate mass has no water, it may be considered a water-in-oil dispersion, whereas “water” are the hydrophilic solids dispersed in the fat phase.
The physical interactions of lecithin phospholipids on sugar-particles form spatial “micro-gaps” between the sugar particles and the fat phase, such as to lower the mechanical friction of the particles in the low-fat dispersion and, consequently, the energy required to maintain the chocolate mass within optimal flow properties.
When everything seems to work like a charm for the newly-enhanced yield value, a second hindrance may potentially invalidate the earned benefits by using lecithin altogether.
In chocolate making, in fact, the finer the solid particles dispersed in a low-fat chocolate, the higher the amount of lecithin required, due to an increasing surface-to-volume ratio of the smaller particles.
Particle A has a surface-to-volume ratio three times higher than particle B, despite its radius being one third B, thus requiring more input (emulsifier) to be ‘wetted’ (coated and lubricated).
But adding more lecithin over a certain threshold may lead to an irreversible inconvenience, known as “thickening effect.” This well-studied phenomenon by the chocolate industry occurs when the amounts of lecithin in excess interact with the lecithin molecules already added, promoting the formation of reverse micelles, which not only cease to decrease the yield stress but start augmenting it after crossing a 0.4% dosage.
Dosing lecithin in chocolate at around 0.4% normally provides tenfold (4%) cocoa butter savings. Chocolate tolerates a dosage of 0.4% soy lecithin, after which the yield value starts gradually increasing, making the chocolate thicker.
To overcome the drawbacks procured by lecithin over the years, the run-of-the-mill chocolate industry started 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 large chocolate industry
As any residual moisture in chocolate evaporates during the early part of conching, an initial expedient to ward off the thickening effect in chocolate is to add lecithin just toward the end of conching. Coating with lecithin—as well as cocoa butter—the surface of particles not completely dry would otherwise cause the humidity to remain locked in the chocolate mass.
When making milk chocolate, other components such as dairy phospholipids may show surface-active properties similar to those of lecithin and thus further contribute to the thickening effect. In synergy with lecithin, dairy phospholipids may end up increasing the yield value of chocolate.
Crumb-made chocolate (chocolate made from vacuum-dried dairy and cocoa) is even more sensitive to the presence of lecithin. The first crumb-made milk chocolate made by Cadbury in the 1960s was prone to taste undesired “grass” or “hay” notes during its storage. For this reason, the British company sought a new alternative to lecithin, called ammonium phosphatide (AMP), also known as Emulsifier YN.
The first edition of AMP, though, was based on rapeseed oil—rich in unhealthy trans-fatty erucic acid. 50 years forward, an improved version of AMP would be obtained from refined sunflower oil and glycerine by the Danish emulsifier producer Palsgaard.
When compared to soy lecithin, AMP has a few significant advantages, such as a more constant phospholipid composition, a totally bland flavor, and greater flow functionalities, as it does not show any unwanted thickening effect but continues reducing the PV while keeping the YV at the same level even at higher dosages.
AMP can extend the cocoa butter savings of chocolate formulated with soy lecithin by an additional 2-3% to create a total potential total saving of 6-7%.
Another widely used lecithin-alternative emulsifier in chocolate manufacturing is polyglycerol polyricinoleate (PGPR), obtained by polycondensation of castor oil and glycerol.
PGPR does not have large effects on plastic viscosity but can reduce yield value by 50% at 0.2% or remove it at about 0.8%, turning chocolate into a quasi-Newtonian fluid, so that it flows more readily and settles rapidly when poured into the mold.
Industrial chocolate manufacturers mostly use PGPR as lecithin coadjuvant to achieve a desirable yield value and plastic viscosity, mainly when the chocolate has too many fine particles to coat or if too much lecithin has been added.
Fine chocolate: does the industry stand up against or for lecithin?
If for almost a century, the mainstream chocolate industry has found the use of lecithin and lecithin-alternative emulsifiers so economically appealing, what the current position taken by fine chocolate?
Diverging experiences and interests animate different fine chocolate brands concerning the inclusion of lecithin in their products.
A preponderant part of fine chocolate brands, represented by the growing wing of makers who would identify their production as “artisan”, “handmade”, “small-batch”, excludes lecithin regardless of any cost/benefit assessments, doing so mainly for branding’s sake, since today’s consumer is asking for fewer and fewer ingredients and an accessible language printed on a product label. Moreover, efficient machinery specifically designed for the production of fine chocolate is facilitating a brand’s demand that prefers not to feature lecithin in their philosophy.
Of opposite take are fine chocolate brands including lecithin in their products while still aiming at an aura of authenticity, naturalness, and transparency, by opting for more sustainable and cleaner alternatives, such as sunflower lecithin or, at most, organic soy lecithin.
As lower quantities of lecithin (around 0.2-0.3%) are typically required in a fine chocolate product thanks to its naturally-abundant content in cocoa butter (well over 32%)—and, conversely, considerably lower in dry solid particles of added sugar, a few valid reasons are in support of the lecithin partisans. With flavor being the dearest aspect to a trusted fine chocolate brand, limiting cocoa butter additions to 4-6% and using lecithin for further viscosity adjustments turns out 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 may also resort to the functional role of lecithin as it standardizes the production of certain problematic lines, i.e., filled chocolate products will be made more stable against susceptibility to fat bloom, migration, or oxidation, while plainer ones will rely on a more efficient speed of production and invest the time saved in other business activities to increase market share and brand reputation.
As long as opting for a fine chocolate brand over another remains the final choice of consumers and customers alike, fine chocolate brands turning out products with superior flavors and standards than mass-produced ones will keep embracing different methodologies of production and spur innovation in the global chocolate industry for the years to come—be it with or without lecithin.
What’s your experience or take with lecithin in chocolate?