Flavor Materials are highly potent, highly aromatic, materials that require dilution to reach proper consumable concentrations. Most of these materials are present in nature at very low concentrations, parts per million (ppm) levels: 1ppm = 0.0001%. In order to deliver such low concentrations into a beverage or food, solvents must be used to dilute the materials to a proper level. Various solvents are used to dilute materials to the desired concentration; taking into account various factors such as solubility (both of the materials and the finished product), volatility and potential reactions.
Types of Solvents:
Ethanol (Ethyl Alcohol)
Neobee Oil (Medium Chain Triglycerides)
Ethanol is an extremely popular solvent due to being relatively tasteless and odorless, as well as its versatility. Most Flavor Materials including essential oils are easily soluble in Ethanol, making it extremely easy to work with for flavor creation. However, Ethanol is not always permitted in the finished product (and certainly not at any level beyond a small fraction of a percent) and it is an extremely volatile solvent. Ethanol is often not permitted in the finished product due to a variety of reasons: desired label claims, regulatory requirements, reactivity, safety and others.
Many finished products companies (especially in the pharmaceutical world) want to make the claim that their product contains no ethanol (you won’t get drunk when you consume it). Certain food and beverage categories do not permit any ethanol in the finished product without labeling it as an alcoholic beverage. This requirement is typically centered on the concentration of ethanol in the finished product; often a requiring below a fraction of a percent. Ethanol can be highly reactive with other flavor materials (reactions will be covered in depth later), and as such can prove undesirable to utilize in certain flavor types. One last major consideration (although there are many minor considerations) is safety. This consideration can be mitigated by proper procedures and safety measures but Ethanol is extremely flammable. Ethanol has a Flash Point of 16.6oC (Merriam Webster defines Flash Point as the lowest temperature at which vapors above a volatile combustible substance ignite in air when exposed to flame - https://www.merriam-webster.com/dictionary/flash%20point ), requiring extra safety precautions for working with and transporting the flavor.
Benzyl Alcohol is a popular “additive” or secondary solvent. Benzyl Alcohol displays many properties similar to that of Ethanol; most importantly, most of the materials soluble in Ethanol are also soluble in Benzyl Alcohol. Benzyl Alcohol comes with many of the same drawbacks, except for label claim: can claim “does not contain ethanol” because Benzyl Alcohol is not Ethanol (it does not have the same effects in the human body as ethanol). However, Benzyl Alcohol comes with one major negative: it is not odorless. Benzyl Alcohol has a noticeably Cherry aroma, which can be a negative when utilizing in flavors where a cherry aroma is not desired.
Glycerin is not an extremely popular solvent but does see some use in flavor delivery due to its sometime desired added characteristics. Glycerin is a viscous solvent that has a slightly sweet taste when utilized at lower levels. The viscosity of Glycerin allows a Flavorist to manipulate a flavors release in the finished product by changing the volatility of flavor materials. The physically thick material will “hold onto” volatile materials better than ethanol and can create a more rounded profile. However, Glycerin does not have great solubility and can be extremely difficult to work with due to its viscosity. It is often utilized as a secondary solvent.
Neobee Oil (Medium Chain Triglycerides)
Neobee Oil is a very popular solvent; however, it cannot be utilized in any water-based finished product without the use of weighing agents or emulsification (to be visited later). Neobee oil is relatively tasteless and odorless, like ethanol, but is not volatile and most flavor materials are readily soluble in it. These factors, along with the Neobee’s low reactivity, make it an extremely useful solvent, as long as the finished product is not water-based. Neobee oil is also a popular solvent to use for a procedure called Spray Drying which coats a dry core with flavor (thereby creating a dry flavor for finished products that cannot utilize a liquid flavor).
Triacetin, similar to Neobee oil, has a very low reactivity, is non-volatile, tasteless and odorless, and can solubilize a large variety of flavor materials (Although, essential oils are not soluble in Triacetin). There are two major drawbacks to utilizing Triacetin. The first, Triacetin is more expensive relative to the other solvents; making it not useful for delivery of flavor requiring oil solubility, as it is not as versatile as Neobee and more expensive. The second (and likely more important), Triacetin is not easily solubilized in water. All of the benefits of Triacetin are nearly negated by the low solubility in water, which makes the last solvent on the list the most valuable solvent for flavor creation.
Water can be a useful secondary flavor to slow some reactions and increasing shelf stability. It is not widely used due to microbial growth considerations, as well as low solubility of most flavor materials.
Propylene Glycol has been a solvent that has garnered a lot of publicity over the last 10 years, most of it unjustly negative (that will be revisited). However, Propylene Glycol is likely the most popular solvent for flavors due to a number of factors. Propylene Glycol is relatively tasteless and odorless, non-volatile and easily water-soluble. A large variety of materials are readily soluble in Propylene Glycol making it a great delivery for flavors. Those materials that have poor solubility in it can be solubilized by adding small amounts of ethanol or benzyl alcohol. Propylene Glycol is extremely versatile and relatively inexpensive. In consideration of length, Propylene Glycol will be covered in-depth on its own.
Mentioned earlier, not all finished products are capable of utilizing liquid flavors. As such, other means of flavor delivery have been developed to produce dry flavors for these products. One example for utilization of dry flavors would be drink mixes, such as Powdered Gatorade or Kool-aid. There are three major forms of processing for dry flavors: Plating, Spray Drying and Encapsulation.
Plating is a technique by which a liquid flavor is added to a tank filled with a powder carrier (ex: Maltodextrin) and mixed until the material is free flowing and completed coated in flavor. Once upon a time, this technique was all there was available to create dry flavor systems. There are a number of advantages to plating, including cost, processing difficulty and aroma release. Plating provides a very aromatic product as the flavor is physically coated on the outside of the carrier, allowing more volatile components to evaporate over time. When in a finished product, the presence of a plated material can provide a nice aroma when opening a bottle. The disadvantage of plating centers on stability. Because the material is coated on the outside of the carrier, the flavor is exposed to the air and can undergo oxidation reactions or evaporation. Over a rather short period of time, the flavor will change due to reaction and can dissipate due to volatile components evaporating.
In order to mitigate the stability problems of Plating, a technique called Spray Dry was developed as an alternate method of drying flavors. Spray drying is a process where an oil-based flavor is emulsified with a carrier system (usually Modified Starch) in water, then sprayed into a heated chamber where the water is evaporated and the rest is collected. The resulting product is a partially encapsulated flavor in and on the carrier system. This process greatly increases stability with only minor changes to flavor perception. The addition of heat can change the flavors character, but the short duration of heat results in only minor changes. The advantages of Spray Dry flavors are definitely a game changer for the flavor industry. Flavors maintain much longer shelf stability in regards to flavor profile and intensity, but also undergo very few changes during processing. Spray Dry flavors do cost more than Plated, as the process is more labor intensive and requires specialty equipment; however, the over time the benefits pay back that difference through longer product shelf life.
Although Spray Dry flavors are the most common and often more than sufficient for most products, some flavors require additional protections for stability. Citrus flavors are highly susceptible to oxidation when exposed to light and air, and even Spray Dried citrus flavors have a relatively short shelf-life (this due to only a partial encapsulation). As a result, Encapsulation techniques have been developed at many flavor houses to accommodate more reactive flavors. Many techniques are closely guarded as to processing parameters and technical aspects, in order to preserve the company’s competitive advantage. However, most have a similar framework and all utilize the same concept: completely encapsulate a flavor inside a carrier system. Some techniques include adding flavor to a molten sugar mixture, then extruding the mixture into long cylindrical strips. Once extruded, the strips are cut into very small pieces, and washed with a solvent (i.e. ethanol) that will remove any residual flavor on the outside of the hardened surface. Once washed, these granular particles will be completely impervious to air, maintaining the flavor stability inside the particle. The resulting particles have a much longer shelf-life, but they come at much greater cost. The process is expensive, labor intensive and can result in much larger changes to the original flavor (which must be accounted for at the time of flavor creation).
In order to properly deliver a flavor into a finished product, many considerations must be taken: solubility, liquid or dry, solvent requirements, and many more. The method of delivery is almost as important to consider as the flavor materials chosen; with the wrong method of delivery, the flavor will be a failure, no matter how good the original design. In addition to considerations above, some of the most important items to consider, when choosing a delivery method, are the potential reactions that could take place within the flavor over time. Some of these topics will be explored in the next several posts; topics such as Flavor Reactions, Emulsions, “Is Propylene Glycol Safe?” and more.