Original papers
Aqueous Extraction and Nutraceuticals Content of Oil Using Industrial Enzymes from Microwave Puffing-pretreated Camellia oleifera Seed Powder
2016 Volume 22 Issue 1 Pages 31-38
Details
2016 Volume 22 Issue 1 Pages 31-38
The objective of this study was to extract the oil from Camellia oleifera seeds by aqueous enzymatic oil extraction (AEOE). A novel process for extraction of oil using industrial enzymes from microwave puffing-pretreated Camellia oleifera seed powder was described. The results indicated that the free oil extraction efficiency obtained with microwave-assisted extraction was very high, which the recovery yield was up to 55% (dry weight of Camellia oleifera seed). Besides, microwave pretreatment of Camellia oleifera seed increased the tocopherols (by 22.2% – 39.4%), squalene(by 6.3% – 29.2%) and phytosterols (by 6.7% – 14.8%) of the oils extracted by AEOE. Moreover, a very low acid value and peroxide value of oil superior to those of oils obtained by previous works was obtained. From the obtained results, this novel process may prove to be an environment-friendly alternative to solvent extraction.
Camellia oleifera (Theaceae) is one of the widely cultivated and important oilseed crops in China. C. oleifera seed oil is the main cooking oil in China's southern provinces, especially Hunan and Jiangxi. C. oleifera seed oil is composed mainly of unsaturated fatty acids with oleic acid (C18:1) being the predominant fatty acid (Zhang, et al., 2011). Due to its high oleic acid content and to high levels of natural antioxidants (phenols and tocopherol), C. oleifera seed oil is very resistant to peroxidation, forming few free radicals (Ye, et al., 2001).
Industrial processes for the extraction of edible oil from Camellia oleifera seeds generally involve a solvent extraction step preceded by pressing. Mechanical pressing is often associated with lower yield and more energy consumption, while the use of hexane, generally employed for oilseed extraction is being questioned because of its toxicity and flammability (Latif, et al., 2009). Safety considerations on the use of organic solvents prompted attempts in the past to develop aqueous extraction but these were unsuccessful mainly due to the low oil yields (Hagenmaier, et al., 1975).
Aqueous enzymatic oil extraction (AEOE) is becoming an important alternative to hexane oil extraction, which offers many advantages compared to conventional oil extraction. With this process we can eliminate not only the use of hexane but some refining steps can also be omitted. Many papers have been published on the effects of enzymes on the extraction and characteristics of olive oil (Najafian, et al., 2009; Tabtabaei, et al., 2013). One disadvantage associated with AEOE is still a low free oil yield and a high production cost in this process, which limits industrial application of AEOE. In order to effectively increase the oil yield, some pretreatment approaches have been utilized based on aqueous enzymatic oil extraction. Sharma et al. (2006) reported that the ultrasonic pre-irradiation enhanced the oil yield from 77% to 95% (w/w) using aqueous enzymatic oil extraction from almond. Proteases improved oil extraction from both soybean flour and extruded soybean flakes, but combining extrusion with enzyme treatments yielded more free oil than enzyme treating flour alone (Lamsal, et al., 2006). Enzyme-assisted aqueous extraction processing (EAEP) of extruded flakes yielded the highest oil yield, which were 96% for soybean (De Moura, et al., 2008; Wu, et al., 2009). Aqueous enzymatic process assisted by microwave extraction of oil from yellow horn seed kernels yielded the maximal oil yield of 55.8% under optimal conditions (Li, et al., 2013).
The present study deals with a novel process for aqueous extraction of C. oleifera seed oil using industrial enzymes from microwave puffing-pretreated Camellia oleifera seed samples. We also studied and compared the physico-chemical attributes of oil and the nutraceuticals contents of the enzyme-extracted oils with those of the solvent-extracted oil. To our knowledge, this is the first report on the effect of microwave treatment for oilseed powder with a high moisture content on the quality of oil.
Sample Camellia oleiferaseed samples were obtained from the local market. The sample standards were purchased from Sigma–Aldrich Co. (USA). Four different types of enzymes were obtained from Nanning Pangbo Biological Engineering Co., Ltd. (neutral protease and alkaline proteinase, China) and Imperial Jade Bio-technology Co., Ltd. (cellulose and pectinase, China), respectively. All chemicals and solvents used were of analytical grade.
Microwave puffing-assisted aqueous enzymatic oil extraction
C. oleifera seed kernels in 70% ethanol aqueous solution (1:1 w/v) containing no or 1% sodium bicarbonate (w/v) were milled by crusher. C. oleifera seed kernel meal was collected and sieved through a 120-m mesh sieve to obtain the fine powder meal subject to microwave heating at 800 W power for specified period of time. The microwave puffing powder was mixed with distilled water at a ratio of 1:7 w/v (10 g powder for 70 mL distilled water). Enzyme was added and the mixture was incubated at 50 – 60°C for 0.5 – 2 h in a water bath with constant shaking. Total free oil forming the upper phase was collected and weighed. The amounts of oil recovered were calculated as percentage of dry weight of C. oleifera seed kernel. Experiments were carried out on extracted oil samples as soon as possible after oil extraction.
Oil extraction by solvent Oil was extracted from C. oleifera seed samples by solvent. In brief, powdered C. oleifera seeds (50 g) were extracted with 500 mL hexane at room temperature with vigorous shaking for 48 h in an Erlenmeyer flask covered by aluminium foil. Then, the mixture was filtrated through defatted filter papers, using a Buchner funnel under vacuum. Solvent was removed under reduced pressure at 60°C. Experiments were carried out on extracted oil samples as soon as possible after oil extraction.
Quality indices analysis of C. oleifera seed oil The peroxide value of seed oil was determined according to China Official Method GB/T 5538-2005 and expressed as millimole of active oxygen per kilogram of oil. The acid value (mg KOH/g oil) was measured by China Official Method GB/T5530-2005/5.
Determination of tocopherols Tocopherols were analysed using an HPLC following China Official Method GBT5009.82-2003. A 20 µL sample was injected into a ultrasphere ODS column (4.6 mm × 25 cm, 5 µm). The flow rate was kept at 1.7 mL/min and the UV detector was fixed at 300 nm. Tocopherols were qualified using standard UV spectrum analysis. Tocopherols were identified by comparing their retention times with those of pure standards of α-, β-, γ-, and δ-tocopherols and were quantified on the basis of peak area of the unknowns with those of pure standards (Sigma-Aldrich Chemical Co.). The tocopherol/oil ratio was expressed as mg/100 g. Under the chromatographic conditions used, β- and γ-tocopherols did not separate fully, so the sum of β- and γ-tocopherols was determined.
Determination of squalene Quantification of the squalene was performed on a Agilent-7890A gas chromatograph equipped with a flame ionization detector (FID). The content of squalene was conducted by simply diluting 2 g of oil in 10 mL hexane. The samples were previously filtered. 1 µL of the mixture was injected directly into the gas chromatograph and a DB1701 capillary column (30 m × 0.32 mm, 0.50 µm) was used. The operating conditions were as follows: nitrogen at a flow rate of 2.5 mL/min was used as the carrier gas, and temperature programming was isothermal: the oven temperature was 250°C, and the temperature for injector and detector was 300°C. Squalene was qualified using standard spectrum analysis.
Phytosterol analysis For analysis of phytosterols, oil samples were first saponified. The weighed oil sample (0.25 mg) was mixed thoroughly with 5 mL of 0.5 M KOH in 95% ethanol in a glass tube, and shaken in a water bath at 90°C for 15 min. After cooling the tubes, 2 mL of water and 1.5 mL of hexane were added and mixed vigorously. Thereafter, the mixture was centrifuged at 3000 rpm for 5 min and the hexane layer containing unsaponifiables was separated for further analysis. An Agilent DB1701 capillary column (30 m × 0.32 mm, 0.50 µm) was used. The column was connected to a Agilent-7890A gas chromatograph equipped with a flame ionization detector (FID). The analysis conditions were: (a) injector 310°C; (b) oven 60°C for 1 min, increased at a rate of 40°C / min to a final temperature of 310°C held for 27 min; (c) nitrogen as the carrier gas at a flow rate of 36 mL/min and (d) detector temperature of 310°C. Quantification of phytosterols was done relative to 5α-cholestane as an internal standard.
Fatty acid compositions Fatty acids were derivatized to their corresponding methyl esters using BF3-MeOH. Fatty acids methyl esters (FAME) were injected into a Agilent HP88 capillary column (60 m, 0.25 mm inner diameter, 1 µm film thickness) installed in Agilent 7820 A gas chromatography (Agilent Technologies) equipped with a flame ionization detector (FID). The sample (1 µL) was injected with a split ratio of 50:1 and the inlet temperature was set at 270°C. During chromatography, initial oven temperature was 170°C and initial time was 14 min. Then the temperature increased to 250°C at a rate of 10°C /min and kept for 8min. The carrier gas was nitrogen with a flow rate of 1.5 mL/min. Identification of FAME was achieved by comparing their retention times with those of authentic compounds analyzed under the same conditions. The composition of FAME was expressed as relative area percent of total FAMEs.
Data analysis The experiments were done in triplicate and the values reported were the means ± standard deviation.
Selection of enzyme species of aqueous enzymatic oil extraction A major feature of the oil seed cotyledon is that it is made up of cells that contain discrete cellular organelles called lipid and protein bodies (also known as spherosomes and oleosomes), which are the principal repository sites of lipid reserves in oil seeds (Jacks, et al., 1990). The walls that surround the cells are primarily composed of cellulose, hemicellulose, and lignin in addition to pectin. The rupture of cell walls is a critical step in improving oil extraction yield during aqueous enzymatic extraction oil. Using most hydrolytic enzymes such as cellulases, hemicellulases, and pectinases in the usual aqueous enzymatic extraction oil processes is to break the structure of the cotyledon cell walls and to release oil from the plant material cells (Gai, et al., 2013). In our previous findings, microwave puffing as a pretreatment step ruptured the structure of oilseed cells where there were not the intact cells to be found and most of the oil was located on the surface of oilseed materials (Zhang, et al., 2011). When Neutral protease, Alkaline proteinase, Cellulose and Pectinase were added, 54.6 – 54.8, 54.8 – 55,49.6 – 49.8 and 49.9 – 50% of oil yield were obtained, respectively (Table 1). The highest oil yield was obtained from Alkaline proteinase treated seed samples, whereas, the lower oil contents were observed with Cellulose and Pectinase. The higher oil contents determined can be explained by the hydrolysis of proteins, which possibly causes a breakdown in the protein network that surround the oil droplets in microwave puffing-pretreated Camellia oleifera seed samples, thereby liberating the more oils.
| Enzyme and solvent | Extraction yield for microwave pretreatment using | |
|---|---|---|
| Ethanol(%) | Sodium bicarbonate+ethanol(%) | |
| Neutral protease | 54.6±0.28 | 54.8±0.3 |
| Alkaline proteinase | 54.8±0.14 | 55.0±0.24 |
| Cellulose | 49.9±0.35 | 50.0±0.26 |
| Pectinase | 49.6±0.14 | 49.8±0.29 |
| Control | 47.7±0.8 | 48.1±0.3 |
Temperature effect The experiments carried out to evaluate the temperature effect upon extraction are presented in Table 2. The results indicated the higher oil extraction yield and lower at 55°C and 60°C to be 54.8% and 52.2% for neutral protease and 55 and 52.9% for alkaline proteinase. On the whole, literature reports do not agree with respect to the temperature impact. Although thoughtfully reported as an essential parameter in some oilseeds cases (Dominguez, et al., 1994), it has also been shown to exhibit no considerable effect in others (Sarkar, et al., 2004). In this work, the decrease of oil extraction yield has been found at 60°C in relation to others, which reveals that some enzymatic activity could have been lost under this condition. Since high temperatures will inactivate the enzymes, thus excluding the possibility of their recuperation and recycling, and require more energy, the lower value is preferable in industrial application.
| Enzyme | Temperature | Extraction yield for microwave pretreatment using | |
|---|---|---|---|
| Ethanol(%) | Sodium bicarbonate+ethanol(%) | ||
| Neutral protease | 45°C | 52.6±0.31 | 52.8±0.21 |
| 50°C | 54.6±0.28 | 54.8±0.3 | |
| 60°C | 52.2±0.24 | 52.3±0.27 | |
| Alkaline proteinase | 45°C | 53.3±0.26 | 53.5±0.2 |
| 50°C | 54.8±0.14 | 55.0±0.24 | |
| 60°C | 52.9±0.32 | 53.0±0.29 | |
Incubation time effect The effect of different incubation times on extraction is given in Table 3. It can be seen from Table 3 that, for neutral protease and alkaline proteinase, 1 – 2 h of incubation time resulted in a higher yield of oil. These results are not in agreement with those reported by Passos et al. (2009) that it was not effective to detect observable enhancements in extraction yield for shorter times and increments of 8.9, 19.5, 46.5, 60.2 and 136% were measured for t = 8, 16, 24, 48 and 120 h of reaction. In our case, from 1 h to 2 h, only a small increment of 0.4% was achieved, but the oil yield has reached 54.4 – 54.7%, which clearly surpassed most earlier studies, despite other parameters having not yet been considered and optimised. This might be due to the complete rupture of oleosomes in microwave puffing-pretreated oilseed samples.
| Enzyme | Time(h) | Extraction yield for microwave pretreatment using | |
|---|---|---|---|
| Ethanol(%) | Sodium bicarbonate+ethanol(%) | ||
| Neutral protease | 0.5 | 51.7±0.21 | 51.4±0.21 |
| 1 | 54.4±0.14 | 54.5±0.19 | |
| 2 | 54.6±0.28 | 54.8±0.3 | |
| Alkaline proteinase | 0.5 | 51.5±0.21 | 51.8±0.22 |
| 1 | 54.5±0.23 | 54.7±0.2 | |
| 2 | 54.8±0.14 | 55.0±0.24 | |
Quality indices analysis FFA (free fatty acid) is one of the most frequently determined quality indices during the production, storage, and marketing of oil products and the oil price is dictated by FFA content (Saad, et al., 2006). The FFA limit in China Camellia oleifera seed oil mills is 2.5 mg KOH/g oil(free fatty acid 1.25% as oleic acid). In particular, extra virgin olive oil (EVOo) (free acidity <0.8 g/100 g) is recognised by the EC Regulation as the product with the highest quality among different commercial categories of olive oils (European Community, Commission Regulation) (2003).
The acid values determined for oils extracted by different methods from Camellia oleifera seeds are presented in Table 4. A significantly lower content of free fatty acid (0.10% – 0.15% as oleic acid) compared with previously reported publications (Baboli, et al., 2010) was observed in the AEOE oils, which might be due to the fact that the endogenous lipases in Camellia oleifera seed were inactivated by ethanol and microwave treatments used in this study. Previous studies have shown that there is an endogenous lipase (triacylglycerol acylhydrolase) in oil palm fruits, and is the first enzyme to be involved in the degradation of triacylglycerols. The action of lipase causes increment in free fatty acid levels in palm oil once the disruption of cells occurs. On the other hand, Lorenzo Cerretani reported that lipolysis was significant only at the longer microwave treatment times (more than 12 min), especially in EVOo, and it seemed to be directly related to the water content of oils (Cerretani, et al., 2009).
| Parameter | Extracted by | Extracted by aqueous enzymatic processes after microwave pretreatment using | |||
|---|---|---|---|---|---|
| Solvent | Ethanol | Sodium bicarbonate+ethanol | |||
| Neutral protease | Alkaline proteinase | Neutral protease | Alkaline proteinase | ||
| Acid value mg KOH/g oil | 0.38±0.01 | 0.22±0.01 | 0.3±0.01 | 0.19±0.00 | 0.21±0.00 |
| Peroxide value mmol/kg | 1.06±0.04 | N.D. | N.D. | N.D. | N.D. |
N.D. not determined
The oxidative state of oil was determined using the peroxide value. The peroxide value determines the formation of hydroperoxides (primary oxidation products) (Gunstone, et al., 2004). The peroxide values determined for oils extracted by different methods from Camellia oleifera seeds are also stated in Table 4. The peroxide values of oils extracted by AEOE were not detected, indicating that there are no thermal degradation of oil in the process of microwave treatment samples. These results were found to be not in agreement with the findings of Uquiche et al. (2008) where moisture content of the rapeseed samples before microwave treatment was 7% and acid value and peroxide value of oil extracted by pressing were 1.83 mg KOH/g oil and 0.92 meq O2/kg oil), respectively. It should be mentioned that the microwave treated samples in our study have a high moisture content of more than 30%.
Tocopherol and squalene analysis Tocopherols are lipophilic antioxidants present in vegetable oils. Tocopherols occur in four related forms, designated alpha (α), beta (β), gamma (γ) and delta (δ) on the basis of their chromanol ring. It is reported that α-tocopherol has the stronger vitamin E activity, whereas the δ-tocopherol has better antioxidant efficacy than either γ-, β- or α-tocopherols (Ozcan, et al., 2005). Tocopherol contents of all the extracted oil samples were determined by HPLC (Fig.2, Table 5). The concentration of α-Tocopherol in oil samples ranged from 6.25 to 8.71 mg/100 g and other tocopherols were not detected under the experimental conditions used in this study. α-tocopherol was found to be significantly higher in the enzyme-extracted oils (7.64 – 8.71 mg/100 g) than that of the solvent-extracted (6.25 mg/100 g) oil showing an enhancement of 22.2 to 39.4%, which may be attributed to the fact that the microwave puffing pretreatment damaged the intact cell structure of oilseed, increased the release of tocopherols, and enhanced their amount in the extracted oils as shown in Table 5. Results obtained from these experiments are consistent with those presented in our previous publication (Zhang, et al., 2011). Azadmard-Damirchi et al. (2010) also reported that the pretreatment of Camellia oleifera seeds by microwave prior to oil extraction by press increased the tocopherols significantly in oils and improved the oxidative stability. Similar results had also been published by Ko et al. (2003).
High-performance liquid chromatogram of tocopherols of standards
(1)(β+γ)-Ttocopherol; (2) δ-tocopherol;(3)α-tocopherol.
High-performance liquid chromatogram of tocopherols of Camellia oleifera seed oil
| Tocopherol and Squalene | Extracted by | Extracted by aqueous enzymatic processes after microwave pretreatment using | |||
|---|---|---|---|---|---|
| Solvent | Ethanol | Sodium bicarbonate+ethanol | |||
| Neutral protease | Alkaline proteinase | Neutral protease | Alkaline proteinase | ||
| α-Tocopherol mg/100g | 6.25±0.07 | 7.76±0.02 | 8.71±0.00 | 7.64±0.02 | 7.69±0.01 |
| (β+γ)-Tocopherol mg/100g | N.D. | N.D. | N.D. | N.D. | N.D. |
| δ-Tocopherol mg/100g | N.D. | N.D. | N.D. | N.D. | N.D. |
| Squalene µg/mg | 0.048±0.000 | 0.062±0.001 | 0.062±0.002 | 0.052±0.001 | 0.051±0.002 |
Squalene, a C30H50 triterpenic hydrocarbon with six nonconjugated double bonds, is usually found in the deep sea shark, olive oil and palm oil. It is a known natural antioxidant that plays a important role in lowering blood cholesterol, enhancing the anti-tumor action of chemotherapeutic agents, inhibiting cancer growth and increasing the efficiency of the immune system (Ko, et al., 2002). Consequently, the presence of a high content of squalene in Camellia oleifera seed oil would improve its nutraceutical value (Xu, et al., 2011).
GC-FID chromatogram of squalene standard
The squalene content of the oils is shown in Fig.4 and Table 5 and a mean of 0.048 – 0.062 µg/mg was detected. The oils from microwave-treated Camellia oleifera seeds were significantly richer in squalene (0.051 – 0.062 µg/mg) as against the solvent-extracted oil (0.048 µg/mg), indicating that microwave-treatment improved the qulaty of oils. However, the squalene concentrations under two microwave treatment conditions were very different, ranging from 0.062 to 0.062 µg/mg of squalene/mg of oil for microwave pretreatment only adding ethanol and 0.051 – 0.052 µg of squalene/mg of oil for microwave pretreatment adding sodium bicarbonate+ethanol. This can be explained that microwave pretreatment destroyed squalene in alkaline experimental conditions.
GC-FID chromatogram of squalene of Camellia oleifera seed oil
Phytosterol analysis Phytosterols (plant sterols) are minor components of vegetable oils and form a major proportion of the unsaponifiables (Azadmard-Damirchi, et al., 2005). Phytosterols in vegetable oils are important from a nutritional point of view because they contribute to lowering serum cholesterol levels, and are also considered to have anti-inflammatory, anti-bacterial, anti-ulcerative and antitumour properties in humans, as well as contributing to the oxidative and thermal stability and shelf life of vegetable oils (Przybylski, et al., 2006). The amount of individual and total phytosterols varied significantly depending on the extraction method (Table 6). Oil extracted from C. oleifera seed by solvent had the lowest phytosterol content (2366 mg/kg) among all the analysed samples while phytosterol content of oil extracted by AEOE from microwave puffing-pretreated Camellia oleifera seed had higer amounts of phytosterol (2524.5 – 2716.5 mg/kg). These results concur with previously published results where phytosterol content in oil samples extracted by press increased with increasing microwave treatment time and total phytosterol contents of oil extracted by press from untreated oil and oil treated for 2 and 4 min with microwaves were 6601, 7407, and 7813 ppm, respectively (Azadmard-Damirchi, et al., 2010).
GC-FID chromatogram of fatty acid methyl esters of standards
| Phytosterol | Extracted by | Extracted by aqueous enzymatic processes after microwave pretreatment using | |||
|---|---|---|---|---|---|
| Solvent | Ethanol | Sodium bicarbonate+ethanol | |||
| Neutral protease | Alkaline proteinase | Neutral protease | Alkaline proteinase | ||
| Total mg/kg | 2366±21.21 | 2679.5±6.361 | 2716.5±57.28 | 2612±14.14 | 2524.5±40.31 |
Fatty acid composition analysis The fatty acid compositions of the camellia oleifera seed oil are given in Fig.6 and Table 7, which shows the principal fatty acid components in the camellia oleifera seed oil. The major saturated fatty acids in oil samples were palmitic and stearic acids which accounted for 8.9 – 9.0% and 3.6 – 3.8% of the total fatty acids, respectively. The main unsaturated fatty acids were oleic acid (78.1 – 78.7%) and linoleic acid (7.7 – 8.3%). Oleic acid being of monounsaturated fatty acids (MUFA) was the most abundant in C. oleifera seed oil (approximately 78%). As compared with virgin olive and other edible oils already reported (Baboli, et al., 2010; Dıraman, et al., 2009; Mitra, et al., 2009), camellia oleifera seed oil has a higher content of oleic acid indicating a good nutritional value of seed oil. From Table 7, no significant variation was observed for the fatty acid composition in the oils extracted by different methods, suggesting no effect of microwave treatment on the fatty acid composition of oil. No previous data were available on the effect of microwave treatment on the fatty acid composition of oil for comparison. However, Yaqoob et al. reported that the effect of gamma irradiation on the fatty acid composition of oil extracted from irradiated sunflower seeds was significant (Yaqoob, et al., 2010).
GC-FID chromatogram of fatty acid methyl esters of Camellia oleifera seed oil
| Fatty acid | Extracted by | Extracted by aqueous enzymatic processes after microwave pretreatment using | |||
|---|---|---|---|---|---|
| Solvent | Ethanol | Sodium bicarbonate+ethanol | |||
| Neutral protease | Alkaline proteinase | Neutral protease | Alkaline proteinase | ||
| Myristicacid(14:0) | 0.046±0.000 | 0.049±0.000 | 0.05±0.001 | 0.05±0.000 | 0.046±0.001 |
| Palmitic acid (16:0) | 8.9±0.000 | 8.9±0.000 | 9±0.000 | 8.9±0.000 | 8.9±0.000 |
| Hexadecylenic acid(16:l) | 0.092±0.001 | 0.086±0.001 | 0.086±0.000 | 0.09±0.000 | 0.0890±0.001 |
| Heptadecanoic acid(17:0) | 0.064±0.000 | 0.065±0.000 | 0.065±0.000 | 0.066±0.001 | 0.065±0.000 |
| Heptadecenoic Acid(17:1) | 0.049±0 | 0.051±0.001 | 0.049±0.001 | 0.049±0.000 | 0.049±0.000 |
| Stearic acid (18:0) | 3.8±0.000 | 3.6±0.000 | 3.7±0.000 | 3.7±0.000 | 3.7±0.000 |
| Oleic acid (18:1) | 78.7±0.000 | 78.2±0.000 | 78.1±0.000 | 78.5±0.000 | 78.45±0.071 |
| Linoleic acid (18:2) | 7.7±0.000 | 8.3±0.000 | 8.3±0.000 | 7.9±0.000 | 7.9±0.000 |
| Linolenic acid (18:3) | 0.165±0.007 | 0.16±0.000 | 0.165±0.007 | 0.17±0.000 | 0.17±0.000 |
| Arachidic acid (20:0) | 0.081±0.000 | 0.077±0.000 | 0.078±0.001 | 0.079±0.001 | 0.079±0.001 |
| Eicosanoic acid (20:1) | 0.445±0.007 | 0.44±0.000 | 0.44±0.000 | 0.45±0.000 | 0.45±0.000 |
The two major drawbacks in the AEOE process are the cost of the enzyme and the low oil yield, which limits its industrial adoption. In the present study, we provided a novel process for aqueous extraction of C. oleifera seed oil using industrial enzymes from microwave puffing-pretreated Camellia oleifera seed samples. From the obtained results, it is advisable to treat Camellia oleifera seed powder with microwave before oil extraction by AEOE, because it gives relatively good recovery of oils and improves nutraceuticals content of oils extracted by AEOE. Furthermore, we firstly reported that there was a positive effect of microwave pretreatment of Camellia oleifera seed powder with a high moisture content on quality of oil, which gave a very low acid value and peroxide value of oil superior to those of oils obtained by previous works. Overall, the quality of Camellia oleifera seed oil obtained by the novel extraction process is superior to that of oil obtained by conventional methods.Therefore, this novel process may prove to be an environment-friendly alternative to solvent extraction.
