The Science Behind Flavourings and their Solubilities
Oct 24, 2023
Introduction
Flavourings have become essential components in the food and beverage industry for several reasons, one of which is their ability to dissolve into a wide range of applications, including water-based or fat-based solutions.
In this blog, we will explore the process of creating flavourings based on their solubilities, understand their characteristics and advantages, and discover their applications in various industries.
By gaining insight into the secrets of the flavour industry, you will understand how the flavourings you use are developed and identify the potential challenges involved when requesting them for your products.
Flavours formulation and compounding
This is the expertise of the flavourist—to balance a flavour formulation using water-soluble and fat-soluble raw materials, resulting in perfect solubility, stability, and homogeneity of the flavouring throughout its shelf-life and the product it is applied to.
To ensure solubility, it is important to consider specific requirements when formulating and compounding flavourings, such as:
🔸Quantities of each raw material (e.g. solvent, flavouring substances, natural preparations, foodstuffs, additives) and their solubility (will be discussed in more detail in the next chapter).
🔸Format of each raw material: Most raw materials are available in a liquid form as dilutions. However, some raw materials, such as vanillin and heliotrope, are only available in powdered forms. In order to use these powdered materials, they need to be dissolved using heat and mechanical agitation.
🔸The order of mixing: This is the sequence in which the raw materials should be combined, taking into consideration their solubility and reactivity.
🔸Choice of food-grade solvent: Solvents are selected based on their solubility, in the application, whether it is water-soluble or fat-soluble.
Other general requirements to formulate a flavouring include depiction, legislation, CIU, dietary restrictions and preferences, sustainability, achieving desired flavour profile, strength, and nutritional profile of the application.
Flavouring substances and natural preparations solubility
Flavouring substances, which are isolated aroma compounds, have the ability to evaporate, so transform from liquid or solid into gas, at room temperature.
This property is what makes them so valuable when it comes to food/beverage - they can be easily carried by air inhaled or exhaled when eating and reach the olfactory receptors at the back of our nose.
Various factors can affect the volatility of the aroma compounds contained in a product, among their solubility.
Indeed, most aroma compounds are relatively insoluble in water, due to their hydrophobic properties. The theory is that because of their aversion to water, they have a tendency to evaporate.
Only some shorter-chain aroma compounds are soluble in water.
Natural preparations are obtained from plant, animal, or microbiological sources and can be either water-soluble or fat-soluble.
These preparations often contain hundreds of aroma compounds. Examples of natural preparations include coffee extract, raspberry esters, strawberry juice concentrate, and peppermint essential oil.
Food-grade solvents
Food-grade solvents are essential in the flavour industry as they serve as carriers to effectively blend all raw materials in a flavouring (e.g. flavouring substances, natural preparations, foodstuffs, additives), allowing them to dissolve in both water-based and fat-based applications.
They typically make up 60-90% of the flavouring, while the remaining portion consists mainly of flavouring substances and natural preparations.
For water-soluble flavourings, solvents like ethanol, propylene glycol (PG), or glycerol are commonly used. Ethanol and PG are particularly effective in solubilising aroma compounds.
For fat-soluble flavourings, solvents like triacetin, MCT oil (medium-chain triglyceride extracted from coconut), or vegetable oils are commonly used. Triacetin, in particular, proves highly effective in solubilising aroma compounds, although it can become bitter when used in high dosages.
Challenges
Flavouring substances and natural preparations are generally soluble in PG and Triacetin at low quantities.
However, it becomes more challenging when flavourists create Natural X flavourings, also known as FTNF (From The Named Fruit) or Natural X flavourings WONF (With Other Natural Flavourings), which contain larger quantities of natural preparations.
For instance, essential oils, which are fat-soluble, may have limited solubility in PG (depending on their quantity in the flavouring), but they are soluble in ethanol and triacetin.
Even if some essential oils dissolve in ethanol, they may not dissolve in clear water-based beverages once the flavouring is added. In such cases, it is necessary to separate the essential oil from its fat-soluble aroma compounds, such as terpenes, or create emulsions.
How do flavourists manipulate the solubility of flavourings?
From Essential oil to washed extract
Essential oils are natural preparations that are extracted from the skin, flowers, or leaves of botanicals, spices, and foods (such as basil, cinnamon, and coffee) that contain high levels of aroma compounds.
They are obtained through mechanical or vapour extraction processes, chosen based on the yield, sensibility, and composition of the material being extracted.
A mixture of ethanol and water is typically used as a solvent to selectively extract specific aroma compounds.
Although essential oils are not soluble in water, they find wide applications in fat-based products. However, to incorporate them into water-based and transparent applications like clear jelly or beverages, insoluble aroma compounds, such as terpenes found in citrus fruits and certain botanicals like lavender, pine, or thyme, need to be removed.
These processes result in terpeneless oils, also known as washed oils or washed extracts. It is important to note that these processes alter the flavour profile and intensity due to the loss of some aroma compounds.
Flavour emulsions
Emulsions used in the flavour industry are stable suspensions of fat-soluble flavourings (such as essential oils) in a water phase.
The water phase contains water, fruit or vegetable juice concentrates, stabilisers (such as gum acacia and modified starch), water-soluble flavourings, acids, and preservatives. Additionally, emulsions require weighting agents to increase the low density of the oils.
They provide a straightforward method of incorporating insoluble flavourings into water-based food and beverage systems, such as soft drinks. However, it is important to note that emulsions result in a cloudy finished product and necessitate preservation against microbial spoilage.
Moreover, emulsions are employed in the flavouring manufacturing process to produce encapsulated flavourings.
Encapsulations
Spray-drying is a widely used technique for encapsulating water-soluble and fat-soluble flavouring substances and natural preparations, particularly citrus essential oils.
This encapsulation method is employed for a variety of reasons, including enhancing flavouring shelf-life (such as delaying oxidation), improving storage options, controlling flavour release, and preventing flavour contamination across production lines and products.
This process involves creating an emulsion by combining and emulsifying water-soluble and fat-soluble components to achieve a fine and uniform particle size. Triacetin is commonly used as a solvent, while PG should be avoided as it can make the powdered flavour hygroscopic and cause the particles to clump together.
The emulsion is then dried by spraying it into a hot chamber, effectively encapsulating the flavouring within each particle.
The choice of carrier, such as gum arabic, modified starches, or maltodextrin, used in the encapsulation process can result in some cloudiness in the final product, depending on the dosage of the flavouring.
There are various other encapsulation techniques, including granulation, which is the most advanced form. Various granulation technologies can be employed to achieve different granule shapes, sizes, and colours, including core-shell structures, extrusion, or agglomeration.
These techniques are also effective in homogenising water-soluble and fat-soluble flavouring substances and natural preparations, and tend to be more heat resistant.
Main applications
Beverages
Flavour emulsions, made from oil-soluble flavourings like citrus essential oils, are commonly used in certain soft drinks such as soda and lemonade.
This emulsion not only adds flavour, but also a slight cloudiness to the beverage. It should not be confused with a cloud emulsion, which is specifically used to introduce turbidity with minimal flavour contribution.
To maintain product quality over its shelf life, emulsions must remain stable and not coalesce or separate. If the flavour emulsion separates from the soda, it may rise to the top and leave behind a noticeable white creamy or oily ring in the neck of the bottle.
To create clear and soluble beverages (e.g. flavoured water, tonic water, gin, vodka), water-soluble flavourings such as PG or ethanol based flavouring, essences and washed extracts are used. These beverages typically have a longer shelf-life and are less prone to oxidation since some aroma compounds like terpenes have been removed.
Powder products
Spray-dried flavourings are commonly used in powdered products such as instant soups, hot chocolate, custard, protein powders, and meal replacement powders.
This encapsulation method ensures that the flavouring is evenly distributed throughout the product, prolongs its shelf life by delaying oxidation, and maintains its flavour profile and strength over time.
Just like other dried raw materials, spray-dried flavourings may settle at the bottom of the product over time. To ensure a flavourful experience, the product may need to be shaken before use.
It is important to note that when using spray-dry flavouring in a product, its aroma will be less pronounced compared to liquid flavouring as the flavour is encapsulated. Additionally, the release of aroma compounds when consuming a product with spray-dried flavourings will be delayed compared to products with liquid flavourings.
Baked goods
Baked goods offer a wide range of opportunities for incorporating flavourings. These may include fat-soluble or water-soluble flavourings, as well as liquid or encapsulated options, depending on the specific application.
However, one of the main challenges with baked goods is the heat treatment they undergo during the process. This often leads to a significant loss of volatile aroma compounds, resulting in a finished product with a less pronounced and less satisfying flavour profile.
Baking losses can be minimised by initially mixing fat-soluble flavourings with butter, shortening, or oil before incorporating them into the recipe. Water-soluble flavourings can also be used, although the boost in intensity may not be as great.
This is because most aroma compounds are hydrophobic and tend to gravitate towards fat-soluble molecules, resulting in better retention during the baking process.
Another solution is to use granulated flavourings. Some granulated processes involve encapsulating the flavouring in a matrix outside of a solid core (e.g., acids, sugars, sweeteners, botanicals), which is then surrounded by a fat coating.
The idea behind this is that the fat coating will delay the dissolution of the encapsulated flavouring until later in the baking process, providing protection against evaporation.
Savoury Snacks
The flavouring can be incorporated into the dough before heat treatment (e.g. baking) or applied topically after heat treatment (e.g. baking, frying, or extruding).
Most savoury snacks use powdered seasonings, which is a combination of encapsulated flavourings, foodstuffs (e.g. herbs, spices, vegetables, fruits), basic taste ingredients (e.g. sugar, salt, yeast extract, acids), and some functional ingredients (e.g. anti-caking agents).
Topical application is commonly used for adding flavour to snacks like crisps, popcorn, puffed snacks, and tortilla chips. There are two main methods: slurry and dust-on.
In the slurry method, a mixture of liquid and powder ingredients, including the seasoning, is mixed in oil and then sprayed onto the product. In the dust-on method, oil is sprayed onto the product before adding the powder ingredients among the seasoning.
These seasonings have to adhere to strict and specific requirements, such as particle sizes and fluidity, to ensure they can pass through the nozzles of the machines, guarantee even distribution on each product, and prevent any waste caused by drop-off.
Conclusion
Flavourists play a crucial role in achieving optimal solubility of flavourings in various applications for the food and beverage industry.
They utilise their formulation expertise and techniques such as washed extracts, flavour emulsions, and encapsulations to balance water-soluble and fat-soluble flavouring substances and natural preparations.
Different applications require specific types of flavouring solubility to address not only their incorporation but also various challenges.
These challenges include oxidation, maintaining flavour strength and profile over time, minimising aroma compound losses during heat treatment, and ensuring a smooth process.
To gain a deeper understanding of flavourings, it is important to comprehend the process and challenges involved in creating both water-soluble and fat-soluble flavourings.
By acquiring this knowledge, you can make more informed decisions, enhance the efficiency of your future projects, and ensure that the products you create meet consumer expectations.
In order to maximise the benefits of working with flavour suppliers, it is crucial to improve communication with them. Involve your flavouring suppliers early on in your project.
Don't hesitate to ask them questions as their invaluable insights can guide you and prevent wasted time with incompatible flavourings for your product.
Link to related blogs you may enjoy
🔶The Magic of Aroma Compounds: How They Shape Our Food Experience
🔶Flavourings Unwrapped: What is a flavouring?
🔶Natural vs. Non-Natural Flavours: A Comprehensive Guide
🔶What You Need to Know Before Using Flavourings
🔶Unleashing the Zest: Exploring the World of Citrus Essential Oils
References
Previous experience includes working at a flavour house, where I received comprehensive flavour trainings.
S.J. Risch, Flavors and colors for microwave foods, Development of Packaging and Products for Use in Microwave Ovens, 2009,Pages 176-191, https://www.sciencedirect.com/science/article/abs/pii/B978184569420350007X
John Wright, Flavor Creation, 2004
Gary Reineccius, Flavour chemistry and technology, second edition, 2006
European flavour association (EFFA) https://effa.eu/eu-legislation/flavouring-legislation
British Society of Flavourists https://www.bsf.org.uk/
European legislations: Flavouring Ingredients EC (1334/2008) https://www.legislation.gov.uk/eur/2008/1334/contents
