Abstract
Palm oil is one of the most consumed oils, one of whose refining steps is the removal of pigments and other substances using bleaching clay as adsorbent. Worldwide production of this oil was 70 million tons in 2017, requiring 1 t of clay to produce 1000 t of refined oil. The residual bleaching clay, having an oil fraction (12.70%) rich in phenolics, carotenoids and tocopherols, was extracted in this study with ethanol to obtain an antioxidant-rich palm oil bleaching extract (POBE), with the aim of using it as a natural antioxidant source. The POBE antioxidant capacity determined by the DPPH method corresponded to a 20.29% inhibition of radical formation. The POBE was also tested for its potential to enhance oxidative stability of passion fruit, pracaxi and Brazil nut oils used as reference oils, and compared to common synthetic antioxidants (tert-butylhydroquinone and propyl gallate), either separately as controls or in mixtures with them. Besides the increased oxidative stability of these oils induced by the POBE, a positive synergistic effect between it and the synthetic antioxidants was observed. These results taken together suggest that the exploitation of the waste oil from bleaching clay as an additive to improve the oxidative stability of biofuels or lubricating oils is feasible.
Highlights
Palm (Elaeis guineensis) is grown on over 11 million hectares worldwide [1], and its oil is one of the most important branches of agribusiness in many countries
The aim of this work was to recover the clay used as an adsorbent in the palm oil bleaching process and to use the residual oil extract (POBE) as an antioxidant additive in order to increase the oxidative stability of vegetable oils
The passion fruit, Brazil nut and pracaxi oils were tested as references for future studies on biofuels and lubricating oils
Summary
Palm (Elaeis guineensis) is grown on over 11 million hectares worldwide [1], and its oil is one of the most important branches of agribusiness in many countries. Because of its high content in fatty acids and substances with strong antioxidant activities, such as tocopherols, tocotrienols and carotenoids, palm oil is one of the most consumed in the world and serves a variety of sectors, among which are the food, cosmetic, biofuel and energy industries [2,3,4,5]. In the initial two steps, some emulsifying substances such as lecithin, free fatty acids, glycerol, carbohydrates, resins and metals are removed [7]. Bleaching is one of the most important steps of refining, during which pigments (chlorophyll and its derivatives, carotenes, tocopherols), saponifiable materials, phosphatides, phospholipids, peroxides, metals, water and so on are eliminated [8,9,10]. The loss of bioactive compounds from palm oil is inevitable during the refining process
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