Deacidification of Microalgal Oil with Alkaline Microcrystalline Cellulose
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Deacidification of Microalgal Oil with Alkaline Microcrystalline Cellulose Qijun Li 1,2 & Zhenzhen Zhou 1,2 & Dongmei Zhang 1 & Wei Cong 1 Received: 13 August 2020 / Accepted: 8 November 2020/ # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
Microalgal oil is considered a promising candidate for edible oils. However, investigation of the refining processes of microalgal oil has been limited, especially deacidification. In this work, microcrystalline cellulose (MCC) was pretreated using different methods and utilized for the first time in the deacidification of microalgal oil. Detection results from FTIR and XRD indicated alkali pretreatment had a significant effect on the structure of MCC. Some inter- and intramolecular hydrogen bonds in AMCC (alkali-pretreated MCC) were destroyed, and crystallinity index of cellulose decreased, which increased its adsorption capacity and the reaction of OH groups with free fatty acids. Some NaOH was adsorbed into AMCC through cellulose swelling, which also contributed to deacidification. The interaction with oil was also improved with many cracks and voids on the surface of AMCC. AMCC could reduce the acid value to about 2 mg KOH/g. Comparatively, original MCC and MCC pretreated with microwave or ultrasound did not exhibit the ability to deacidify. Furthermore, the conditions of alkali treatment were optimized. Treatment with 20% NaOH for 20 min was optimal. Compared with other adsorbents, such as sodium silicate and chitosan treated with alkali and resin, only AMCC could effectively reduce acid value while maintaining high lipid recovery. Therefore, AMCC was considered a better adsorbent for the deacidification of microalgal oil. Keywords Microalgal oil . Deacidification . Adsorption . Microcrystalline cellulose . Alkali treatment
* Dongmei Zhang [email protected]
1
State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China
2
University of Chinese Academy of Sciences, Beijing 100190, People’s Republic of China
Applied Biochemistry and Biotechnology
Introduction Microalgae have attracted substantial attention from researchers in recent years with the advantage of not competing with arable land and high production efficiency [1]. The Food and Agriculture Organization (FAO) has suggested large-scale algae cultivation as food to supply proteins, and microalgae are also considered as a candidate for the sustainable production of edible oils [2]. The fatty acid composition of microalgae oil is mostly C16 and C18 fatty acids, similar to vegetable oils [3, 4]. Moreover, particular microalgae, for example, Nannochloropsis sp., are rich in valuable omega-3 polyunsaturated fatty acids (PUFAs), which were reported to positively reduce cardiovascular disease, cancer, and depression in humans [5, 6]. One of the essential steps in the oil refining process is deacidification, which can remove free fatty acids (FFAs) in oil to prevent oil rancidity [7]. According
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