A comprehensive review on the techniques for coconut oil extraction and its application

Bioprocess and Biosystems Engineering https://doi.org/10.1007/s00449-021-02577-9 CRITICAL REVIEW A comprehensive review on the techniques for coconut oil extraction and its application Yan Jer Ng1 · Pei En Tham1 · Kuan Shiong Khoo1 · Chin Kui Cheng2 · Kit Wayne Chew3 · Pau Loke Show1 Received: 24 February 2021 / Accepted: 21 April 2021 © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2021 Abstract Virgin coconut oil is a useful substance in our daily life. It contains a high percentage of lauric acid which has many health benefits. The current industry has developed several methods to extract the oil out from the coconut fruit. This review paper aims to highlight several common extraction processes used in modern industries that includes cold extraction, hot extraction, low-pressure extraction, chilling, freezing and thawing method, fermentation, centrifugation, enzymatic extraction and supercritical fluid carbon dioxide. Different extraction methods will produce coconut oil with different yields and purities of lauric acid, thus having different uses and applications. Challenges that are faced by the industries in extracting the coconut oil using different methods of extraction are important to be explored so that advancement in the oil extraction technology can be done for efficient downstream processing. This study is vital as it provides insights that could enhance the production of coconut oil. Keywords Virgin coconut oil · Lauric acid · Extraction process · Application Introduction * Kit Wayne Chew * Pau Loke Show ; Yan Jer Ng Pei En Tham Kuan Shiong Khoo Chin Kui Cheng 1 Department of Chemical and Environmental Engineering, Faculty of Science and Engineering, University of Nottingham Malaysia, Jalan Broga, 43500 Semenyih, Selangor Darul Ehsan, Malaysia 2 Department of Chemical Engineering, College of Engineering, Khalifa University, P. O. Box 127788, Abu Dhabi, United Arab Emirates 3 School of Energy and Chemical Engineering, Xiamen University Malaysia, Bandar Sunsuria, 43900 Sepang, Selangor, Malaysia Coconut is one of the most important tree crops in the tropical region of the world securing food and shelter for millions of people. Coconut tree is grown in more than 93 countries around the world in an area of 11.95 million hector producing 57,510 million coconuts annually [1]. Virgin coconut oil (VCO) was introduced to the world at the end of twentieth century. It is being considered as the greatest value derived from the fresh coconut [2]. VCO becomes one of the most prominent high-value coconut products in coconut producing countries because of its versatility. VCO gains worldwide popularity because of its wide range of applications in medication, food, cosmetics and hair care products [3]. VCO is a clear, high value oil obtained from the fresh mature kernel of coconut through mechanical or natural means [4]. Various methods have been employed to extract the coconut oil, but whichever method have been used it is still the best to avoid oil that has been refined, bleached or deodourized. This is because when the coconut oil undergo these processes, the health benefit, taste and the aroma will be reduced [3, 5]. As VCO contains large amount of high value compounds, its importance has been given more and more attention by the industry throughout the years. This results in the development of various extraction processes, 13 Vol.:(0123456789) Bioprocess and Biosystems Engineering each with its respective advantages and limitations. Therefore, it is crucial for the industry to choose the most suitable extraction process to avoid breaking down of the high value compounds. VCO is believed to have medical qualities, including but not limited to antifungal, antioxidant, antibacterial, antiviral, hepatoprotective, low glycaemic index and immune system enhancement [6]. Coconut oil comprises 90–95% of saturated fatty acid [7]. Unlike long-chain fatty acid found in plant-based oil, medium-chain fatty acid is smaller in size, allowing higher cell permeability for immediate energy conversion instead of being stored as fat. When compared with long-chain fatty acids found in plant-based oil, mediumchain fatty acid can also be digested more easily and at the same time it is also antimicrobial and antifungal [8]. VCO contains 2.6% less calories as compared to other fats as it provides various health benefits to human body [9]. It helps in controlling blood sugar level as it preserves insulin action and insulin resistance. VCO also helps in preventing liver disease by reversing hepatosteatosis which is a type of fatty liver disease [10, 11]. Moreover, coconut oil also plays important roles in hair care and cosmetic products. When compared with mineral oils, it penetrates better to the dry and fizzy hair giving a shinier look of the hair due to the smaller particle sizes of VCO [12]. VCO is found to be a powerful antioxidant product which serve to fight against free radicals in the human body as it helps to slow down the ageing process [11]. The most popular traditional method of oil extraction are cold extraction and hot extraction process. The challenges faced by these two processes include low yield of oil and the heating process in the hot extraction technique will cause a reduction in the antioxidant properties in oil. Since the last decade, several extraction techniques have been introduced with the aim to improve the technology for coconut oil extraction. Table 1 shows the summary of various techniques available for coconut oil extraction. This review aims to let reader understand the difference between various extraction method of coconut oil and the applications of VCO. This paper will discuss various extraction processes in depth, including its respective advantages and limitations. The daily and industrial application of VCO will also be included in the end of this paper as well. Properties of coconut oil Physical properties Coconut oil is a colourless liquid at a temperature of 30 °C and above. It will be solidified at a temperature of 25 °C. Solidified coconut oil is white in colour. Unrefined coconut oil reaches its smoking point at a temperature of 13 170 °C while refined coconut oil reaches its smoking point at 232 °C [32]. Coconut oil has a typical coconut smell to it only if it is not refined, bleached or deodourized. Coconut oil will form a white homogenous mixture when mixed with water and agitated. Without agitation, coconut oil will be insoluble in water. Coconut oil has a density of 924.27 kg/m3 [33]. The density of an oil depends on its saponification value (molecular weight), iodine value (unsaturation), free fatty acid content, water content and temperature. Density of triglycerides in solid state is approximately 10% greater than in liquid state. However, there is no specific data that was reported on the specific heat for coconut oil. It is known that when in solid state, there i (...truncated)