Extraction, Characterization and Storage Stability of Oils from Selected Plant Seeds

There is a great demand for renewable sources of raw materials that have nutritional and industrial potential. To meet the increasing demand for vegetable oils, improvements are being made with conventional crops as well as with selected plant species that have the ability to produce unique, desirable fats and oils. The physicochemical properties and chemical composition of oil extracted from five varieties of plant seeds (bitter melon, Kalahari-melon, kenaf, pumpkin and roselle) were examined by established methods. Most of the quality indices and fatty acid compositions showed significant (P < 0.05) variations among the extracted oils. The oils were rich in tocopherols, with γ-tocopherol as the major component in all oil samples. Among the phytosterols, β-sitosterol was the major phytosterol extracted from the five plant-seed oils.Enzymatic extraction of oil from Kalahari-melon seeds was investigated and evaluated by response surface methodology. Two commercial protease enzyme products were separately used: Neutrase® 0.8 L and Flavourzyme® 1000 L from Novozymes (Bagsvaerd, Denmark). Response surface methodology (RSM) was used to model and optimize the reaction conditions, namely concentration of enzyme (2-5 g/100 g of seed mass), initial pH of mixture (pH 5- 9), incubation temperature (40-60 °C), and incubation times (12-36 h). The optimal conditions for Neutrase 0.8 L were enzyme concentration of 2.5 g/100 g, initial pH of 7, temperature at 58°C and incubation time of 31 h, yielding an oil recovery of 68.58 ± 3.39%. The optimal conditions for Flavourzyme 1000 L were: enzyme concentration of 2.1 g/100 g, initial pH of 6, temperature at 50 °C and incubation time of 36 h, yielding a 71.55 ± 1.28% oil recovery. The physicochemical properties of oil from Kalahari-melon seed were determined following extraction with petroleum ether and aqueous-enzymatic methods. The free fatty acid, peroxide, iodine and saponification values of the oils extracted using these two methods were found to be significantly (P < 0.05) different. No significant (P > 0.05) difference was observed between the melting points of the oils obtained from solvent and aqueous-enzymatic extractions. Enzyme-extracted oil tended to be light-colored and more yellow in color, compared with solvent-extracted oil. Fatty acids and phenolic acids in enzymeextracted oils were comparable to the solvent-extracted oil. The oils extracted with these two methods differed in the composition of their phytosterol and tocopherol contents, but no significant (P > 0.05) difference between the two enzyme-extracted oils was observed Supercritical carbon dioxide extraction of oil from Kalahari-melon and roselle-seeds were investigated in this study. Response surface methodology (RSM) was used to model and optimize the extraction conditions, namely pressure (200-400 bar), temperature (40-80 ºC) and supercritical fluid flow rate (10-20 mL/min). The optimal processing conditions for Kalahari-melon-seed oil recovery and phytosterol concentration were pressure of 300 bar, temperature of 40 °C and supercritical fluid flow rate of 12 mL/min. These optimal conditions yielded a 76.3% oil recovery and 836.5 mg/100 g of phytosterol concentration. The results indicate that the roselle-seed oil recovery was optimal, with a recovery of 102.61% and a phytosterol composition of 727 mg/100 g at the relatively low temperature of 40 °C, a high pressure of 400 bar and at a high supercritical fluid flow rate of 20 mL/min. Tocopherol-enriched oil from Kalahari-melon and roselle-seeds was extracted by supercritical fluid extraction with carbon dioxide (SFE-CO2). The optimal SFE-CO2 conditions for the extraction of tocopherol-enriched oil from Kalahari-melon seeds were extraction pressure of 290 bar, extraction temperature of 58 ºC and flow rate of carbon dioxide of 20 mL/min. The optimum conditions for roselle-seeds were extraction pressure of 200 bar, extracting temperature of 80 ºC and flow rate of carbon dioxide of 20 mL/min. These optimum conditions yielded a tocopherol concentration of 274.74 and 89.75 mg/100 g oil from Kalahari-seed and roselle-seed, respectively. During 6 months of storage of Kalahari-melon-seed and roselle-seed oils at both 4 ºC and room temperature in the darkness, changes occurred in the content of fatty acids, phytosterols and tocopherols, and in the presence of primary and secondary oxidative products. These seed oils were obtained from the seeds of Kalahari melon (Citrullus lanatus) and roselle (Hibiscus sabdariffa Linn.) by supercritical carbon dioxide (SC-CO2). As expected, statistically significant differences were observed in the content of fatty acids, phytosterols and tocopherols, and in the presence of primary and secondary oxidative products in Kalahari-melon-seed and roselle-seed oils throughout the storage. The quality indices peroxide and anisidine values increased during the 6 months storage time. After storage, degradation parameters may change because of lipid oxidation

In vitro evaluation of the structural and bioaccessibility of kenaf seed oil nanoemulsions stabilised by binary emulsifiers and β-cyclodextrin complexes

Kenaf (Hibiscus cannabinus L.) seed oil contains high nutrition value, suggesting its potential applications in food and nutraceutical fields. However, the poor water solubility and stability strictly limit its applications. A good physical stability of kenaf seed oil-in-water nanoemulsions stabilised by sodium caseinate, Tween 20 and β-cyclodextrin complexes were produced using high pressure homogeniser. A simple model of two-stage dynamic in vitro digestion was employed to investigate the releasing rate of bioactive compounds from kenaf seed oil-in-water nanoemulsions, compared to unencapsulated bulk oil. The particles size and structural changes during digestion were also evaluated. Digested nanoemulsions showed good lipid digestion (85.25%), good bioaccessibility of antioxidants (tocopherols and total phenolic contents) and lower degradation rate of phytosterols compared to digested bulk oil. This study provides good information about the characteristic and release behaviour of formulated kenaf seed oil-in-water nanoemulsions, which is important for the future application in food and nutraceutical industries

Effect of gum arabic, β‐cyclodextrin, and sodium caseinate as encapsulating agent on the oxidative stability and bioactive compounds of spray‐dried kenaf seed oil

Kenaf seed oil is prone to undergo oxidation due to its high content of unsaturated fatty acids, thus microencapsulation stands as an alternative to protect kenaf seed oil from the adverse environment. This study primarily aimed to evaluate the oxidative stability of microencapsulated refined kenaf seed oil (MRKSO) by the use of gum arabic, β‐cyclodextrin, and sodium caseinate as the wall materials by spray drying. Bulk refined kenaf seed oil (BRKSO) and MRKSO were kept at 65 °C for 24 days to evaluate its oxidative stability, changes of tocopherol and tocotrienol contents, phytosterol content, and fatty acid profile. The results showed that the peroxide value, p ‐Anisidine value, and total oxidation value of BRKSO were significantly higher than the MRKSO at day 24. The total tocopherol and tocotrienol contents were reduced 66.1% and 56.8% in BRKSO and MRKSO, respectively, upon the storage. There was a reduction of 71.7% and 23.5% of phytosterol content in BRKSO and MRKSO, respectively, upon the storage. The degradation rate of polyunsaturated fatty acids in BRKSO was higher than that of MRKSO. This study showed that the current microencapsulation technique is a feasible way to retard the oxidation of kenaf seed oil

In-vitro gastrointestinal digestion of kenaf seed oil-in-water nanoemulsions

The high nutrition value of kenaf seed oil has good potential to be used as functional foods or nutraceutical products. Kenaf seed oil-in-water nanoemulsions stabilised by ternary emulsifier mixtures, namely sodium caseinate, gum Arabic and Tween 20 were produced by using high pressure homogeniser. A two-stage in-vitro model was employed to investigate the bioaccessibility of bioactive compounds that is naturally present in the kenaf seed oil-in-water nanoemulsions. The changes in the antioxidants properties before and after in-vitro digestion and the structural changes during digestion were also evaluated. By comparing the digested and undigested nanoemulsions, the digested nanoemulsions had increased the total phenolic content by 71% and tocopherol content by 230%. However, 2,2-diphenyl-1-picrylhydrazyl (DPPH ) radical scavenging activity was decreased by 34% and phytosterols content was decreased by 39%. The amount of free fatty acids (FFA) released from gastric digested nanoemulsions during 120 min of intestinal digestion was 247.7 μmol/mL. This high release of FFA indicates good lipid digestion, which is the preliminary step for releasing and absorption of lipophilic bioactive in the small intestine. This study provides useful insights into the changes of kenaf seed oil-in-water nanoemulsions during gastrointestinal digestion

Effects of accelerated storage on the quality of kenaf seed oil in chitosan-coated high methoxyl pectin-alginate microcapsules

The objective of this research was to study the oxidative stability and antioxidant properties of microencapsulated kenaf (Hibiscus cannabinus L.) seed oil (MKSO) produced by co-extrusion technology upon accelerated storage. The combination of sodium alginate, high methoxyl pectin, and chitosan were used as shell materials. The oxidative stability of the kenaf seed oil was determined by iodine value, peroxide value, p-Anisidine value, total oxidation (TOTOX), thiobarbituric acid reactive substances assay, and free fatty acid content. Total phenolic content, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) cation radical-scavenging assay and 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay were used to examine the antioxidant properties of oils. Oxidative stability tests showed that bulk kenaf seed oil (BKSO) was oxidized significantly higher (P < 0.05) than MKSO. The total increment of TOTOX value of BKSO was 165.93% significantly higher (P < 0.05) than MKSO. Co-extrusion technology has shown to be able to protect kenaf seed oil against lipid oxidation and delay the degradation of natural antioxidants that present in oil during storage

Emulsifying conditions and processing parameters optimisation of kenaf seed oil-in-water nanoemulsions stabilised by ternary emulsifier mixtures

Kenaf (Hibiscus cannabinus L.) seed oil has been proven for its multi-pharmacological benefits; however, its poor water solubility and stability have limited its industrial applications. This study was aimed to further improve the stability of pre-developed kenaf seed oil-in-water nanoemulsions by using food-grade ternary emulsifiers. The effects of emulsifier concentration (1, 5, 10, 15% w/w), homogenisation pressure (16,000, 22,000, 28,000 psi), and homogenisation cycles (three, four, five cycles) were studied to produce high stability of kenaf seed oil-in-water nanoemulsions using high pressure homogeniser. Generally, results showed that the emulsifier concentration and homogenisation conditions had great effect (p < 0.05) on the particle sizes, polydispersity index and hence the physical stability of nanoemulsions. Homogenisation parameters at 28,000 psi for three cycles produced the most stable homogeneous nanoemulsions that were below 130 nm, below 0.16, and above −40 mV of particle size, polydispersity index, and zeta potential, respectively. Field emission scanning electron microscopy micrograph showed that the optimised nanoemulsions had a good distribution within nano-range. The optimised nanoemulsions were proved to be physically stable for up to six weeks of storage at room temperature. The results from this study also provided valuable information in producing stable kenaf seed oil nanoemulsions for the future application in food and nutraceutical industries

Oxidative stability of sunflower oils supplemented with kenaf seeds extract, roselle seeds extract and roselle extract, respectively under accelerated storage

With the concern of adverse effects of lipid oxidation on food deterioration and human health, the antioxidant activities of kenaf seed extracts (KSE), roselle seed extracts (RSE) and roselle extracts (RE) were evaluated by comparing its oxidative stability in refined, bleached & deodorised (RBD) sunflower oils with that of in synthetic antioxidant, BHA. Established methods such as peroxide values (PV), p-anisidine values (AV), TOTOX values, free fatty acids (FFA), iodine values (IV), total phenolic contents (TPC), conjugated dienes (CD) and conjugated triene (CT) were employed to assess the extent of oil deterioration. During 24 days storage, consensus was accomplished based on the results assessed by PV, TOTOX, CD, CT, IV and TPC at which the antioxidant activities of KSE, RSE and RE were better than BHA. Surprisingly, the results obtained by AV and FFA assays showed the reversed. Among the extracts, RSE exhibited the best antioxidant activities. These suggest that KSE, RSE and RE may be used as potential source of natural antioxidants in the application of food industry to prevent lipid oxidation

Effect of chemical refining on the quality of kenaf (hibiscus cannabinus) seed oil

Crude kenaf seed oil was obtained by solvent extraction and chemically refined using industrial refining process, which includes degumming, neutralization, bleaching, and deodorization. The changes in physical characteristics, oxidation indexes, antioxidant activity, bioactive compounds, and fatty acid composition were determined after each stage of refining. The results obtained showed that there was no significant difference in the specific gravity of kenaf seed oil, but there was a significant increase in the refractive index and a significant decrease in the a* and b* values in the color determination after the refining. Peroxide value decreased from 2.64 to 0.55 meq/kg, p-Anisidine value increased from 2.41 to 3.41, TOTOX value decreased from 7.70 to 4.51, and free fatty acids decreased from 1.72 to 0.61 after the whole refining process. There was a removal of 64.5% of total phenolic content, 65.3% of total carotenoid content, 22.5% of phytosterol content and high retention of tocopherol content in kenaf seed oil after refining. Kenaf seed oil showed an increasing of 84.5% and 58.6% in DPPH value and ABTS+ value, respectively. Oleic acid was found in the largest amount in the refined kenaf seed oil (35.1%), followed by linoleic acid (32.3%) and palmitic acid (21.9%). There was a slight increase in unsaturated fatty acids and a slight decrease in saturated fatty acids after refining. This work showed that the chemical refining process offers an improvement in the quality of kenaf seed oil

Functional properties of roselle (Hibiscus sabdariffa L.) seed and its application as bakery product

Roselle (Hibiscus sabdariffa L.) seed is a valuable food resource as it has an excellent source of dietary fibre. Therefore, this study examined the functional properties of roselle seeds. Replacement of cookie flour with roselle seed powder at levels of 0–30 % was investigated for its effect on functional and nutritional properties of cookies. Among the four formulations cookies, the most preferred by panelists was 20 % roselle seed powder cookie (F3), followed by 10 % roselle seed powder cookie (F2) and 30 % roselle seed powder cookie (F4). The least preferred formulation among all was control cookie (F1). Cookie with 20 % roselle seed powder added showed higher content of total dietary fibre (5.6 g/100 g) as compared with control cookie (0.90 g/100 g). Besides that, cookies incorporated with roselle seed powder exhibited improved antioxidant properties. Thus, roselle seed powder can be used as a dietary fibre source and developed as a functional ingredient in food products

Kenaf (Hibiscus cannabinus L.) seed oil-in-water Pickering nanoemulsions stabilised by mixture of sodium caseinate, Tween 20 and β-cyclodextrin

The limit application of functional kenaf (Hibiscus cannabinus L.) seed oil in food and pharmaceutical industry owing to the poor water solubility and low storage stability can be overcome by the development of kenaf seed oil-in-water Pickering nanoemulsions. In this study, oil-in-water Pickering nanoemulsions were produced to investigate its stability by optimising emulsifier mixtures, namely sodium caseinate (SC), Tween 20 (T20) and β-cyclodextrin (β-CD). The interaction effects of SC and T20 on the formation of Pickering nanoemulsions with β-CD was studied and found synergistic effect among them that enhanced the stability of Pickering nanoemulsions. The optimum proportion of emulsifier mixtures obtained by employing simplex centroid mixture design was found to be 57.9% (w/w) SC, 27.6% (w/w) T20, and 14.5% (w/w) β-CD, which produced Pickering nanoemulsion with mean particle size of 155.53 nm, PDI of 0.07 and zeta-potential of −46.67 mV. These experimental values were in accordance with the predicted value, indicating the adequacy of the fitted models. The mixture design was found to be a valuable tool to optimise and study the interaction effects of different components for the development of stable Pickering nanoemulsions