Over the years, citrus fruits have managed to find their way from the tropics of the Asian continent to different parts around the world. The flesh of the fruit is not only tasty and juicy; it is also highly nutritious. It comes as no surprise that their popularity hasn’t dwindled with time.
Researchers are now taking a keen interest in the rind of citrus fruits which previously was considered as a waste product. Citrus rinds are rich in essential oils that have significant industrial applications in the pharmaceutical, cosmetic, and food sectors. 
Citrus aurantifolia, aka the subtle lemon, Mexican lime, or key lime, is a fragrant citrus variety that is of major interest to researchers. One study showed that the essential oils from this fruit have antifungal activity against Phaeoramularia angolensis, a pathogenic fungi with catastrophic consequences.  Important terpene constituents include limonene, β-pinene, γ-terpinene, and citral.  Potential medicinal properties include antimicrobial, antioxidant, antiulcer, anti-inflammatory, and hepatoprotective effects. 
What is the Best Way to Extract Essential Oils from Key Lime?
A group of researchers described an industrial extraction design for obtaining key lime essential oils.  Given the scope of the project, several factors were taken into consideration: equipment design, technical parameters, and cost implications.
The key lime materials were obtained from nearby farms belonging to the Association of Agribusiness Producers in Ecuador. Steam distillation was used to extract three different samples from the citrus raw material; 4kg, 8kg, and 12kg. An operating manual was created for each phase of the distillation process that included the equipment that was used.
Reprinted from: León C, Jordán EP, Salazar K, Castellanos EX, Salazar FW. Extraction system for the industrial use of essential oil of the subtle lemon (Citrus aurantifolia). Journal of Physics: Conference Series. 2020;1432(012044). License: CC BY 3.0
The design of the extraction equipment included a tank, a serpentine condenser, a fire heater, and auxiliary equipment. An architectural plant with dimensions of 150 m2 (16.5m x 9m) was designed and divided into 9 parts.
The 3-meter-long condenser was placed into the 12.5L capacity tank. At least 4 distillers were required for a quantity of approximately 10kg of citrus raw material for this design. 
From this research, it appeared that this design’s performance was relatively low with key lime compared to other raw materials. A 0.361% yield meant that 1 kg of final product was obtained from 276.85 kg raw material. However, a cost-benefit ratio analysis showed that the design was still profitable for industrial application.
Additionally, the research showed that 100 minutes was sufficient for the extraction of 12 kg of key lime material and 61.75 mL essential oil through distillation. After 100 minutes, energy expenditure increased yield negligibly regardless of raw material quantity (4kg, 8kg, or 12kg).
The researchers recommended modification of the design to include a cooling system to increase efficiency in the system and optimize the extraction process. 
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