S. H. Goh

Minor constituents of palm oil.

Crude palm oil contains about 1% of minor components including carotenoids, tocopherols, sterols, triterpene alcohols, phospholipids, glycolipids and terpenic and paraffinic hydrocarbons. The nutritionally important components such as carotenes and tocopherols also improve stability of the oil. Although a highly valued product, carotene unfortunately is bleached or destroyed in refining because suitable recovery technology is not available. Thermal degradation of carotene, previously suspected of giving rise to undesirable chemicals, now is known to furnish mainly harmless hydrocarbons, most of which are removed by the deodorization step in refining. Tocopherols, being natural antioxidants, need to be carefully preserved during milling, refining, fractionation and modification of palm oils. The accumulation of tocopherols in the palm fatty acid distillate promises to provide a new source for the recovery of this valuable substance. The role played by phospholipids is frequently misunderstood because they can act in two ways, i.e. as an antioxidant synergist and a surface active agent to disperse impurities in oil. In crude palm oil the phospholipid content is small, because most of it is removed during milling; the phosphorus content is due mainly to inorganic phosphorus. Among the sterols, cholesterol constitutes too small a percentage to be of much concern. Sterols, triterpenoids and terpenoid hydrocarbons are also potentially useful side products should recovery technology become available. Other newly characterized minor and trace components also are discussed.

Kinetic studies of epoxidation and oxirane cleavage of palm olein methyl esters

The kinetics for the epoxidation of methyl esters of palm olein (MEPOL) by peroxyformic acid and peroxyacetic acid generatedin situ were studied. The rate-determining step was found to be the formation of peroxy acid. Epoxidized MEPOL (EpMEPOL), with almost complete conversion of the unsaturated carbon and negligible ring-opening, can be synthesized by thein situ technique described.The kinetics of the oxirane cleavage of EpMEPOL by acetic acid were studied at various temperatures. The reaction was found to be first-order with respect to the epoxy concentration and second-order to the acetic acid concentration. The activation energy and the entropy of activation for the epoxidation of MEPOL were comparable to those for the oxirane cleavage of EpMEPOL by acetic acid, suggesting that the two reactions are competitive. The success of the epoxidation of MEPOL with only negligible oxirane cleavage is attributed to the heterogeneous nature of the system employed in thein situ technique.

Recovered oil from palm-pressed fiber: A good source of natural carotenoids, vitamin E, and sterols

Recovered fiber from pressed palm fruits, which is normally burned as fuel to provide energy for the palm oil mills, has now been found to be a rich source of carotenoids, vitamin E (tocopherol and tocotrienols), and sterols. Residual oil (5–6% on dry basis) extracted from palm press fibers contains a significant quantity of carotenoids (4000–6000 ppm), vitamin E (2400–3500 ppm), and sterols (4500–8500 ppm). The major identified carotenoids are α-carotene (19.5%), β-carotene (31.0%), lycopene (14.1%), and phytoene (11.9%). In terms of vitamin E, α-tocopherol constitutes about 61% of the total vitamin E present, the rest being tocotrienols (α-, γ-, and δ-). The major sterols present are β-sitosterol (47%), campesterol (24%), and stigmasterol (15%). The oil extracted from palm-pressed fiber is contaminated with about 30% of palm kernel oil. The quality of this fiber oil is slightly lower than that of crude palm oil in terms of the content of free fatty acids, peroxide value, and anisidine value.

Alkaloids of Alstonia angustifolia

Abstract Thirty-one alkaloids have been isolated from the leaves and from the stem bark of Alstonia angustifolia from Malaysia. Twenty of them were known compounds: yohimbine, O -acetyl yohimbine, pleiocarpamine, fluorocarpamine, cathafoline, cabucraline, N -1 desmethylquaternine, vincamajine, normacusine B, lochnerine, affinisine, akuammicine, 11-methoxyakuammicine, antirhine, alstonisine, alstonerine, alstophylline, macralstonine, villalstonine and tetrahydrocantleyine. Among the 11 novel alkaloids, three were monomers: 19,20-dehydro-10-methoxytalcarpine, 19,20-dehydro- O -acetyl yohimbine and hydroxystrictamine, and eight were dimers: villalstonine N -4′-oxide, 10-methoxy villalstonine, 10-methoxyvillalstonine N-4′-oxide, 10-methoxymacrocarpamine, 10-methoxymacrocarpamine N -4′-oxide, angusticraline, alstocraline and foliacraline. Structural elucidation of the new alkaloids was based on spectral data analysis including high field 1 H and 13 CNMR.

Environmental effects on growth and biochemical composition ofNitzschia inconspicua Grunow

The effects of nitrate and silicate levels, and carbon source on growth, biochemical composition and fatty acid composition ofNitzschia inconspicua were investigated using batch cultures. Within the range of silicate levels supplied (8.8–176 μM), no marked variations in growth trend, biochemical composition or fatty acid composition were shown. Biomass at stationary phase, ranging from 64–66 mg ash-free dry weight (AFDW) L−1, and specific growth rate (μ) based on chlorophylla (0.41–0.50 d−1) of the cultures grown within 0.3–3.0 mM NaNO3 were not significantly different. Cultures supplemented with glucose (0.1 % w/v), acetate (0.1 % w/v) or 5% CO2 attained higher biomass (85, 85, 97 mg AFDW L−1) than the control which was grown in synthetic seawater and agitated by magnetic stirring. Cells grown at <3.0 mM NaNO3 contained higher carbohydrate contents (14.8–21.5% AFDW) than those grown at 3.0 mM (4.0% AFDW). Lipid content increased at the expense of proteins in cells aerated with 5% CO2. The dominant fatty acids, 16:0 and 16:1, ranged from 35.7–45.0% and 36.4–45.4% total fatty acids (TFA), respectively, while the relative proportions of 20:4 (n-6) and 20:5 (n-3) ranged from 1.7–5.4% and 3.4–5.9% TFA respectively. Cultures aerated with 5% CO2 attained the highest biomass (97 mg AFDW L−1) and yield of 20:5 (n-3) (0.34 mg L−1).

Transesterification of cocoa butter by fungal lipases : effect of solvent on 1,3-specificity

Transesterification and alcoholysis reactions catalyzed by immobilized lipases fromMucor miehei andHumicola lanuginosa in hexane gave fatty acid esters that did not reflect the expected 1,3-specificity of the enzymes, due to competing acyl migrations in the partial glyceride products. However, both lipases were 1,3-specific in reactions when diethyl ether was used as a solvent, and this provided a convenient analytical methodology in combination with gas chromatography and nuclear magnetic resonance spectroscopy for the determination of fatty acid distribution within triglycerides.

Epoxidized esters of palm olein as plasticizers for poly(vinyl chloride)

A series of esters of palm stearin and palm olein were synthesized by alcoholysis using KOH as catalyst. Epoxidations were carried out in situ by the method of peroxyformic and peroxyacetic acids. The alcohols employed ranged from methanol to dodecyl alcohol. The esters were evaluated as plasticizers for poly(vinyl chloride) (PVC). Esters of palm stearin had poorer compatibility and might be used only as secondary plasticizers. Promising results, however, were obtained for epoxy esters of palm olein which were found to be good plasticizers for PVC. Long chain epoxy esters were less compatible while their short chain counterparts were too volatile for thermal stability. Epoxy butyl esters of palm olein were found to be most promising. The solubility parameters δ for a series of oleates, palmitates and epoxy esters were calculated using Smalls method with Fredors molar volume. Epoxystearates have higher δ values than the corresponding oleates and palmitates, in agreement with the experimental findings that epoxidation improves compatibility. Molar volumes calculated by Fredors method were found to be in remarkable agreement with the experimental values for oleates and palmitates but were overestimated for epoxystearates. It was concluded that the palmitates were largely responsible for the poorer compatibility for the epoxy esters of palm olein prepared from higher alcohols.

Phospholipids of palm oil (Elaeis guineensis)

Mesocarp oil ofElaeis guineensis provides 1000~2000 ppm of phospholipids. Thin layer chromatography revealed that the major components are phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI) and phosphatidylglycerol (PG). Minor components are phosphatidic acid (PA), diphosphatidylglycerol (DPG) and lysophosphatidylethanolamine (LPE), and traces of lysophosphatidylcholine (LPC) and phosphatidylserine (PS) are detectable. An artifact from enzymatic transphosphatidylation in methanolic solvents was isolated and characterized as phosphatidylmethanol (PM). Phospholipids are only present at low levels (20~80 ppm) in commercial crude palm oil and they usually account for a minor part of the total elemental phosphorus of the oil. It is desirable to have low levels of phospholipids in the oil to obtain better oxidative stability and bleaching properties.

Essential oils of Cinnamomum species from peninsular Malaysia

ABSTRACT The chemical composition of the leaf, bark and wood oils of seven Malaysian Cinnamomum species (C. pubescens, C. javanicum, C. iners, C. impressicostatum, C. mollissimum, C. porrectum and C. camphora) was examined by co-chromatography with authentic samples on three columns of different polarity, capillary GC/MS and selective proton NMR. The major components of the leaf, bark and wood oils were identified. These species could be useful new natural sources for safrole, eugenol, linalool, camphor and benzyl benzoate, which are commercially important chemicals in the flavor, fragrance and pharmaceutical industries. The distribution and accumulation of the compounds in different parts of the plant within the same species or among different species may be used for taxonomic purposes and for future use in the identification of possible varieties of Cinnamomum species.

Effects of epoxidation on the thermal oxidative stabilities of fatty acid esters derived from palm olein

A variety of esters from the reactions of monoalcohols with palm olein were prepared, epoxidized byin situ peroxyacid techniques, and some of their physical properties were compared. The thermal oxidative stabilities of these esters andbis(2-ethylhexyl) phthalate were studied. The esters were placed in an oven maintained at 120°C, and the loss of mass and acid, iodine, percent oxirane, hydroxyl, and peroxide values were monitored periodically. The epoxidized esters had higher densities and lower volatilities, and were more resistant toward oxidation than their unepoxidized counterparts. The stability of the oxirane was related to the initial acid value of the sample. Higher initial acid value resulted in a greater decrease in the oxirane content, indicating acid-catalyzed cleavage of the oxirane ring.