Is Edible Palm Oil Replaceable? The Underutilized Pequi Oil Say YES!
Introduction
Palm oil is acknowledged as one of the leading vegetable oils worldwide. It is often referred to the edible crude palm oil (CPO) which generally derived from the Elaeis guineensis species of oil palm fruits’ mesocarp. The commercial palm oil has been consumed daily by almost half of the world’s population in diverse food products, whereby its annual production is more than 69 million tonnes and the market is growing continuously [1]. For instances, palm oil is mostly used as cooking oil and food ingredient in breads, noodles, shortenings, chocolates, margarine, confectioneries and many other foods. This substantial increase of palm oil consumption is due to the fact that it is considered as a healthier alternative to replace trans-fat products [2] [3]. On the other hand, the palm kernel oil (PKO) has a primary application in non-food manufacturing sectors like cosmetics, oleochemicals and many cleaning products [4].
Figure 1. Oil palm fruit and its cross section showing the mesocarp (where CPO is extracted) and its white kernel (where PKO is extracted).
Image Source: Alabi, Olabiyi and Oguntibeju [5]
When compared to other commercially available vegetable oils, the relatively high yield and low production cost have made this palm oil attractive in terms of the financial returns [4]. It is also accompanied with multiple nutritional benefits upon dietary consumption. In spite of its numerous advantages, palm oil has been a highly controversial issue in recent decades, particularly on deforestation and the loss of global biodiversity. Large-scale expansion of oil palm plantations was criticized as a significant threat to the endangered species and increased greenhouse gas emissions that contributing to global warming [2]. The emergences of Roundtable on Sustainable Palm Oil (RSPO) and Certified Sustainable Palm Oil (CSPO) show the efforts of palm oil industry in attempting to tackle the controversies and create the sustainability of palm oil [1] [2]. However, many parties are still arguing for its long-term environmental damage and thus emphasizing on the importance of palm oil substitution with better alternatives in the industrial and consumer products.
In the 21st century, a sustainable and secure supply of vegetable oils is still a major challenge to meet the high global demand, thereby resulting in the much higher prices of commercial edible oils such as palm oil [6]. Due to the palm oil controversies and rising demand for edible oils, many researchers and food manufacturers are seeking for novel or underutilized oils, especially from the sources of oil-bearing crops. Rigorous investigation and development on the potential edible oils with analogous fatty acid profiles, desirable functional and health properties are crucial to replace palm oil [7]. In this context, an underutilized Brazilian native pequi oil that meets a similar fatty acid composition with palm oil was proved for its nutraceutical and economical importance as a viable alternative in the oil and fat industry.
Pequi oil is a novel edible oil which comes from the oleaginous fruits of a perennial pequi tree. It belongs to the Caryocaraceae family with two different genera, namely Caryocar and Anthodiscus [8]. Pequi is native to the Brazilian Cerrado and there are more than 20 species distributed widely throughout Central and South America, in which the C. brasiliense, C. coriaceum and C. villosum are the predominant species that comprised Caryocar genus [8] [9]. Nevertheless, pequi pulp oil derived from the C. brasiliense species in Brazil is the most studied product of interest for natural dietary consumption or supplementation [10]. This underutilized oil has a unique fatty acid profile similar to palm oil, which contains mainly oleic acid (54 – 60%) and palmitic acid (35 – 40%) [7]. Furthermore, pequi oil is also recognized as the richest Brazilian carotenoid sources, at the same time it has a considerable amount of bioactive and nutrients that play a vital role in human health [8].
Pequi Fruit Component
This prevalent fruit in Brazil is drupaceous. Figure 2 illustrates the components of a pequi fruit which typically has 1 – 4 segments (pyrenes). The outermost thin brownish green peel is called epicarp or exocarp [8] [10]. External mesocarp is non-edible, whereas internal mesocarp and almond are the edible portions. The fruit pulp or internal mesocarp normally appears as yellow to orange in colour which attributed to its carotenoids content [7]. Pequi pulp has been employed in food processing sectors for the preparation of pequi rice, liqueur, ice cream, oil, jam, sweets, pickled pequi, ground meat, chicken and savory dishes [8] [10] [11]. This is due to the fact that it is highly nutritious which contains high level of lipids, fibers, tannins, flavonoids, carotenoids, minerals, vitamins A and C [12]. As shown in Figure 2, it is also constituted of a thin spiny layer of endocarp and a whitish mass of almond which is known as kernel, nut or seed. Apart from the internal mesocarp, this almond can also act as a culinary ingredient to be used in the tamale-like cake or condiments [8]. Hence, pequi has been commercialized in Brazil for its most valued edible pulp and kernel in food applications because both of them are excellent sources of proteins and lipids.
Figure 2. Pequi fruit and its cross section of components.
Image Source: Torres et al. [8]
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Cultivation and Growth Conditions of Pequi
Pequi is a fairly slow-growing perennial tree native to the Brazilian savanna (Cerrado) [9]. Table 1 displays several optimum conditions for the growth and cultivation of pequi. This oil crop is suitable to be planted in the drier regions of the world because it can tolerate drought and long dry seasons. Moreover, it is being well-adapted to the less fertile and nutritionally poor soils [13]. To date, pequi tree is mostly found in Central and South America. Nevertheless, it can be potentially cultivated in Southeast Asia for uses especially its rich oil content which is highly valuable and beneficial. Based on climate studies, the annual rainfall of many Southeast Asia regions is usually between 1,000 and 3,000 mm, while the mean temperature is around 18 °C to 27.2 °C throughout the year [14][15]. Therefore, some drier tropical and subtropical climatic zones of Southeast Asia would be more appropriate and preferable for the growth of pequi. For examples, Timor-Leste, Thailand, Laos, Vietnam, Cambodia and Myanmar are the relatively drier regions [15].
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Comparison between Palm Oil and Pequi Oil
In terms of the fatty acid (FA) profile, it can be observed from Table 2 that both palm oil and the unconventional pequi oil have a similar composition. Palmitic acid and oleic acid are the major FA, which make up more than 80% of the total lipid composition. Palm oil with a balanced ratio of saturated and unsaturated FA is usually containing slightly more saturated palmitic acid than the oleic acid, whereas pequi oil is richer in the oleic acid or known as monounsaturated fatty acids (MUFA). Hence, this high-oleic pequi oil could be an ideal replacement for palm oil because of the analogous FA profiles enable a better mimic of palm oil’s physicochemical properties [1].
Table 2. Fatty acid composition (% total lipids) of palm oil and pequi oil [7].
Furthermore, both types of edible oil are suitable to be used in high temperature cooking and frying, due to the small amount of unstable polyunsaturated fatty acids (PUFA). Since pequi oil has extremely low level of linoleic and linolenic acids, it is more oxidatively stable?in the rancidity deterioration process [11]. Besides, both palm and pequi oils can be produced form the fruit pulp and seed kernel. The pequi kernel oil was found to possess similar fatty acid compositions to its pulp oil that shown in Table 2 [7]. In contrast, the composition of palm kernel oil (PKO) is different with the crude palm oil (CPO). The saturation level of CPO is about 50%, while PKO contains approximately 80% of saturated fatty acids where it is a rich source of lauric acid [17].
Table 3 compares some of the characteristics of palm oil and pequi oil. The smell and taste of palm and pequi oils are distinguishable, albeit they have similar FA compositions. It was reported that the extraction process and natural volatiles of pequi oil are the main contributing factors for its strong and sweet flavor. As heat is applied during the oil extraction, it will lead to the formation of several new flavor components [7]. In addition, the pequi pulp or internal mesocarp contains around 36 – 66% of oil which is comparable to the oil content found in the mesocarp of an oil palm fruit. This suggests a strong potential of pequi pulp as an excellent source of oils can be utilized maximally in the oil and fat industry.
Among the functional phytochemicals present in pequi oil, the most significant bioactive compound is carotenoids up to 246 μg/g, which is the main source of β-carotene as the essential pro-vitamin A [9] [11]. The oil also contains a high level of phenolic compounds, especially the ellagic and gallic acids. Vitamin C and Vitamin E contents of pequi oil included ascorbic acid, α-tocopherol, α-tocotrienol, γ-tocopherol and γ-tocotrienol. Moreover, stigmasterol, β-sitosterol, campesterol and squalene were found as the major phytosterol components in this oil [8]. Interestingly, the aforementioned bioactive compounds that present in pequi oil are almost same as those can be found in palm oil, in which both oils are particularly rich in tocopherols, phenolics and carotenoids. As a result, these functional phytochemicals exhibit the similar antioxidant capacities, biological activities and health-promoting properties in both oils [5] [8]. This indicates the underutilized pequi oil is a suitable candidate in replacing the highly demanded palm oil. Due to the high β-carotene content, both palm and pequi oils are naturally reddish to yellowish-orange in colour as illustrated in Figure 3 before refining [5].
Figure 3. Crude palm oil (left) and crude pequi oil (right).
Owing to its high oleic and palmitic acids content, pequi oil that stored at room temperature in tropical climates will tend to undergo phase separation or fractionation, which similar to palm oil. By re-distributing the fatty acid moieties in TAG, this modification process called chemical interesterification is useful to overcome the undesirable fractionation characteristic [7]. Likewise, this technique is also commonly employed for the commercial palm oil. With a new polymorphism, different melting and crystallization profiles, the zero trans-fat produced will give a broader range of applications and functionalities at cold and room temperatures [9]. In order to produce a cocoa butter-like fat, stearic acid can be incorporated at the sn-1,3 position of TAG in pequi oil through an enzymatic modification which performed using Lipozyme [9]. Furthermore, the functionality of cocoa butter is indeed dependent on the triacylglycerol POP to a great extent, where the confectionery industry is now looking for new sources to be utilized as cocoa butter equivalents [7]. As shown in Table 3, the major TAG composition of pequi oil with the presence of POP makes the oil of interest in food industry like the substitution of cocoa butter [8] [9]. Besides, the fractionation of palm olein and palm stearin is regarded as a mature technology nowadays. However, it was reported that the researchers are still currently working on the fractionation process of pequi oil to separate the stearin from olein [7].
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Potential Applications and Health Benefits
In fact, the underutilized pequi oil with a high content of saturated and monounsaturated FA has numerous promising applications. Owing to its high amount of oleic acid, pequi oil is particularly attractive in the food, oleochemical and cosmetic industries. For examples, the cosmetic industry in Brazil has adopted crude pequi oil in their manufacturing of hair products [7]. Additionally, previous studies demonstrated that the formulations of cosmetic products containing pequi oil have positive effects on the skin hydration improvement [20]. This edible oil can also be used as the flavoring and coloring agents in diverse food applications [13]. Meanwhile, this kind of oil is very useful in shortening and margarine applications because of the high palmitic acid content in its FA profile [9]. As mentioned earlier, pequi oil can be potentially used as alternative in making a wide range functionality of trans-fat free products and a less expensive cocoa butter substitute. This is attributed to its TAG composition, as well as the chemical, enzymatic or physical modi?cations [9]. Since pequi and palm oils have analogous TAG and FA profiles, both of them can mostly be used for the same applications, which suggest the feasibility of this underutilized pequi oil in substituting the edible palm oil.
With respect to the medicinal and therapeutic uses, pequi oil is considered as a tonic. Apart from its effective treatment for influenza and vitamin A deficiency-related symptoms, the combination of honey with pequi pulp or seed oil is commonly used by indigenous Brazilian populations to cure the bronchitis and colds [11] [13]. Due to the high level of natural antioxidants and MUFA in pequi oil, they contribute greatly to an extensive health benefits, including anti-inflammatory, anticancer, antitumor, anti-genotoxic, antimicrobial and antifungal effects, as well as the enhanced lymphocyte-dependent immunity, digestive and cardiovascular functions. The findings revealed that the regional Brazilian populations have also routinely made use of the oil extracted from pequi pulp to treat various diseases such as wound lesions, muscle pain, chronic arthritis, tumors, respiratory diseases, gastric and inflammatory diseases [8] [10]. For examples, the carotenoids and oleic acid can help to produce the anti-inflammatory eicosanoids to minimize the expression and concentration of inflammatory mediators at the genomic and protein levels [8]. Moreover, the bioactive compounds are capable of scavenging the free radicals, decreasing oxidative stress and boosting the antioxidant defense system to inhibit the advance of carcinogenesis [8]. Since the pequi oil is rich in oleic acid, it will also alleviate the risk of coronary diseases by reducing the bad LDL (low-density lipoprotein) while maintaining the good HDL (high-density lipoprotein) cholesterols. Meanwhile, the consumption of this healthy MUFA can lower the obesity risks and the plasma levels of triacyclglycerols [10]. Furthermore, pequi pulp oil was also reported to have efficient protection against the oxidative and DNA damages in athletes, as well as suppressing the exercise-induced high blood pressure [8] [10].
Based on researches, most of these health-promoting properties of pequi oil are also applicable for palm oil. This is attributed to the presence of similar functional phytochemicals in both oils that responsible for the biological activities and antioxidant capacities [5] [8]. As discussed earlier, this pequi oil contains a tremendous amount of nutrients, MUFA and bioactive compounds that can significantly improve human health upon dietary consumption. To date, several studies have proved the great potential of pequi oil to be utilized as a source of health supplement or natural medicine. Hence, this unconventional pequi oil with such high nutraceutical values should not be neglected. Instead, it is recommended to further explore the best extraction, processing and commercialization of the edible pequi oil for its maximum use and to substitute palm oil.
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Extraction Methods of Pequi Oil
According to [7] and [11], the crude pequi oil can be obtained through traditional hot water floatation or modern solvent and mechanical extraction techniques. Different extraction methods of pequi oil will eventually influence its carotenoid levels and physicochemical properties. In addition, this kind of oil is usually stored at ambient conditions in the amber bottles to block light and UV rays for minimum loss of bioactive compounds, as well as for a better preservation of oil quality [10] [11].
In traditional hot water floatation method, the collected ripe fruits were peeled and boiled in water for 40 minutes with continuous stirring. After boiling process, the floating oil was skimmed off for subsequent drying and filtering [7]. This method is able to preserve many bioactive compounds in pequi oil, especially the carotenoids. However, it is more time-consuming and the crude oil produced will be less stable [7]. Besides, expeller press is the main equipment in the process of mechanical extraction. Before feeding into the expeller press, the pequi fruit pulp was dried at 60 °C for 1 day. The extracted or pressed oil was then filtered and collected [9] [11]. Mechanical extraction is less preferred because the high temperature during pressing will cause oil degradation, resulting in higher free fatty acid (FFA) content and peroxide values [11]. Due to the associated TAG hydrolysis and oxidation reactions, the crude pequi oil will tend to have shorter shelf life and require more efforts in oil refining before human consumption. Furthermore, this approach also produced lower yield as some oil might retain inside the pressed cake [11].
For the solvent extraction process, prior drying of the pequi fruit pulp at 60 °C for 1 day is necessary, and followed by grinding into fine flour [11]. Hexane, acetone, ethyl ether and ethanol are the common solvents employed for this extraction of pequi oil [7] [11]. Similar to the industrial solvent extraction of other popular vegetable oils, the effective solvent removal or recovery steps are crucial in the downstream processing. When compared to other approaches, it was reported that a relatively high yield of pequi oil could be obtained from this solvent extraction. Since the pequi oil was exposed to lower temperature, this solvent method will also preserve more carotenoids than the mechanical pressed oil [11].
Apart from the aforementioned traditional hot water floatation, mechanical extraction and solvent extraction, the researchers have also studied on a few new techniques recently for this oil extraction either from the pequi pulp or its kernel. For instances, the supercritical fluid extraction assisted by pressing (SFEAP) to extract oil from pequi, the subcritical propane extraction of pequi pulp oil, the Soxhlet extraction and ultrasound-assisted extraction of pequi pulp oil, as well as cold pressing method to obtain the pequi almond oil were reported [20].
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Conclusion and Recommendations
The internal mesocarp of Brazilian native pequi fruit is an excellent source of lipids because it contains around 36 – 66% of oils. This underutilized pequi oil is rich in oleic and palmitic acids, along with a substantial amount of bioactive compounds such as carotenoids, phenolics and tocopherols. Due to the similar phytochemicals, triacylglycerols and fatty acid profiles, the high-oleic pequi oil is a suitable candidate for palm oil replacement. In the functional and nutraceutical points of view, this oil demonstrates a strong potential as a promising edible oil source and provides economic opportunities in the oil and fat industry [6]. Therefore, the unconventional pequi oil as a viable alternative to palm oil should not be neglected, but it is vital to expand the commercialization of the underrated pequi fruit. This would eventually help to meet the continuous growing market demand of edible oils, meanwhile addressing the controversial issues of palm oil.
Nevertheless, pequi oil is harvested from the naturally-growing pequi trees in the wild, where these native plants will not be sufficient to meet the rising demand [7]. As the conventional oleaginous fruits or oilseeds are always prioritized, most of these unconventional oil crops are generally lacking of investments, researches and improvements. Hence, it is suggested to domesticate the wild pequi trees for large-scale production. For instances, some domestication techniques like grafting, vegetative propagation, planted seedlings, organic fertilization, irrigation system and other useful agronomic practices have been investigated to boost the productivity and pequi oil quality efficiently [7] [9] [16]. Besides, it is also recommended to cultivate this oil crop in some drier tropical and subtropical climatic zones of Southeast Asia for commercial utilization.
Although pequi oil has a fairly close TAG and FA profile with palm oil, they will not have exactly the same composition. Therefore, oil blend is suggested to reformulate and mimic the composition of palm oil without the presence of hydrogenation process. In addition, the aforementioned chemical interesterification, enzymatic or physical modi?cations for pequi oil could also be useful to produce the desirable functionalities of edible oil. In order to effectively improve the agrobiodiversity and socio-economical sustainability, further research on the plant cultivation and domestication, as well as the extraction technology for higher pequi oil production and commercialization are necessary. This would definitely add value to the current underutilized pequi oil’s production chain [6] [9]. In short, pequi oil will be an ideal substitution to palm oil, and it is encouraged to fully utilize this great potential edible oil for the benefits of oil and fat industry.
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