Introduction

Citrus essential oils have become increasingly popular in the world of aromatherapy, cosmetics, perfumery, pharmaceuticals, and food/beverage formulations. But what exactly are these aromatic compounds and how are they extracted from citrus fruits? 

Whether you're a curious R&D consultant, a dedicated food scientist, or an innovative product developer, this blog post will take you on a fascinating journey into the world of citrus essential oils. 

From the unique composition of these oils to the methods of extraction, we will delve into the secrets behind their vibrant aromas. We will also explore the sustainability challenges and eco-friendly practices shaping the future of citrus essential oils. 

By understanding the science and practices behind citrus essential oils, you can better appreciate their role in the food and beverage industry and make informed choices about their usage.

What is citrus essential oil? 

Citrus essential oils are aromatic compounds extracted from the oil glands located at various depths in the peel and cuticles of citrus fruits. These fruits, which belong to the Rutaceae family, include lemon, lime, grapefruit, orange, mandarin, bergamot, yuzu, and kumquat.

Additionally, essential oils can be extracted from the flowers and leaves of the orange tree. However, these oils are predominantly used in the fragrance industry rather than the flavouring industry. The essential oil derived from orange leaves is called petitgrain oil, while the essential oil from the orange blossom is known as neroli oil.

Citrus essential oils are not soluble in water, but can dissolve in vegetable oils and alcohol. 

Aroma compounds 

Citrus essential oils consist of 200-400 compounds, including both volatile and non-volatile ones. 

The volatile compounds make up the majority of citrus essential oils, comprising 85% to 99% of the overall composition.

The primary component present in citrus essential oils is limonene, which can vary in concentration depending on the specific type of citrus. For example, lemon essential oil typically contains 45%–76% limonene, while sweet orange essential oil (also known as orange oil) can range from 68%–98% limonene.

Non-volatile compounds found in citrus essential oils make up 1-15% of the composition. These compounds include flavonoids (antioxidants found in wine, chocolate, and tea), sterols (plant-based cholesterol), and fatty acids. 

The composition of citrus essential oils can vary depending on factors such as the maturity of the citrus fruit when harvested, species, variety, terroir, and extraction techniques.

Cost 

The cost of citrus essential oils can vary widely due to several factors. These factors include the amount of citrus peel required, the availability and sensitivity of the plants, and the impact of natural disasters and climate change.

For instance, hurricanes and citrus diseases have significantly impacted orange production in Florida in recent years, resulting in decreased availability and increased prices.

Methods of extraction

Cold pressing 

Citrus essential oils are commonly extracted from the fruit peels through a method called cold pressing, also known as expression. 

This technique ensures that the volatile aroma compounds remain intact as they are not exposed to high temperatures. 

The citrus peels are placed in a container and punctured by a rotating device with spikes. As the peels are punctured and gently pressed, they release the essential oil into a container below. 

The resulting watery emulsion is then separated into the citrus essential oil through centrifugation. 

Overall, cold pressing retains the natural aroma compounds of the fruits and results in high-quality essential oils with vibrant and complex flavours.

Hydrodistillation

The citrus peels are placed either in a heated cooking chamber with water or in a vessel above boiling water for steam distillation. As the steam slowly passes through the peels, it carries the volatile aroma compounds that evaporate. 

The vapours then go through a chilled condenser, which brings them back to their liquid form. The essential oil can be easily separated and collected from the surface of the water. 

To achieve successful hydrodistillation, it is crucial to calibrate the pressure in the cooking chamber, steam temperature, and the duration of the exposure of citrus peels to the steam.

Each citrus plant may require different calibration for these factors.

Washed citrus oils

Citrus oils can undergo additional processing to remove insoluble terpenes, which are prone to oxidation. This process creates terpeneless oils, also known as washed oils or washed extracts. 

These separation methods include solvent extraction (e.g., using a mixture of ethanol and water in a separating funnel), distillation, or chromatography. 

However, it is important to note that some aroma compounds will be lost during the processing, resulting in the reduction of zesty, fresh, and juicy characteristics.  

Yield and best practises 

On average, it takes about 200 kilograms of citrus fruit peels to produce approximately one kilogram of essential oil, depending on the extraction process and the citrus plant used. This relatively low extraction yield contributes to the value and sometimes scarcity of citrus essential oils.

However, it is worth noting that it is not the worst yield compared to other essential oils like rose, which require 4-5 tonnes of rose petals to obtain about 1kg of rose essential oil.

Some manufacturers may redistill the same batch of citrus peels multiple times, resulting in a lower quality essential oil. It is best practice to use the citrus peels only once. 

Other manufacturers may use non-organic raw materials that often contain pesticides or other harmful chemicals, which may then end up in the essential oil. 

Sustainability and future 

Sustainability

In our pursuit of creating affordable, “natural” and delicious food and beverage products, it is crucial to think about sustainability. This ensures that our products are not only good for us but also for the planet.

Even though citrus essential oils are often derived as by-products of the juice industry, they have significant environmental implications.

The cultivation of a large number of citrus plants, sometimes in controlled environments, as well as the extraction and transportation processes of citrus essential oils worldwide, contribute to waste generation, energy and water consumption, as well as CO2 emissions.

In terms of availability, the citrus market is highly unstable because citrus fruit production has been severely impacted in recent years by various factors such as climate change, crop diseases, civil unrest, and land development.

One of the major challenges facing citrus production globally is citrus greening disease. This disease negatively affects the size, quality, and productivity of citrus fruits, making it increasingly challenging for farmers in regions like Florida, Mexico, and Brazil.

Furthermore, this blight now poses a threat to citrus trees in other parts of the world, including Europe in the near future.

Future

That is why recent research focused on developing eco-friendly and energy-efficient green practices including waste minimisation, while ensuring safe and high quality citrus essential oils. 

Some green extraction techniques include supercritical fluid extraction, ultrasound extraction, and microwave steam distillation as well as alternative solvents.

Innovative practices are also being implemented to give these peels a second life. They have been explored for various applications such as insect/pest control, antimicrobial packaging, nanoemulsions for food preservation, or conversion into biogas.

These applications help reduce environmental impact and promote a circular economy.

New research in the flavour industry is currently concentrating on developing alternatives that can emulate the taste and properties of citrus essential oil. This approach takes into consideration the availability and cost-effectiveness of these natural or non-natural ingredients to replicate the original flavour and properties of citrus essential oils.

It is essential to prioritise sustainability now more than ever. Exercise your right to inquire about your suppliers' sustainability policies, as well as their sourcing methods and locations for obtaining oils.

Conclusion

As we conclude our fascinating journey through the world of citrus essential oils, we have explored the intricate processes of extracting the unique and characteristic aroma compounds from citrus fruits. 

We have also discussed the challenges that citrus fruits are currently facing, including disruptions in the supply chain that threaten not only major producers like Florida and Brazil, but also Europe.

Sustainability is crucial for the food and beverage industry, as the future yield of citrus fruits may be drastically affected by climate change and crop diseases. This poses a risk to the availability of citrus essential oils, washed extracts, and flavour molecules like limonene. 

While citrus essential oils have lower environmental impacts compared to essential oils like rose, it is important for essential oil manufacturers and the flavour industry to continue innovating and investing in greener technologies and processes.

This will help ensure citrus sustainability and biodiversity, with the goal of reducing waste, energy and water consumption, and CO2 emissions associated with their production.

It is important for the food and beverage industry to make informed choices when selecting citrus essential oils and to educate their consumers about the challenges associated with them.

Link to related blogs you may enjoy 

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🔶 Uncovering The Flavours Of Chocolate Series  | The Impact Of Cacao Process

References

Previous experience includes working at a flavour house, where I received comprehensive flavour trainings. 

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Gary Reineccius, Flavour chemistry and technology, second edition, 2006

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