Y. B. Che Man

Enzymatic Transesterification of Palm Olein with Nonspecific and 1,3-Specific Lipases

The enzymatic transesterification of palm olein was conducted in a low-moisture medium with nonspecific and 1,3-specific lipases from microbial sources. The enzymes were first immobilized on Celite, lyophilized for 4 h and then added to a reaction medium that consisted of 10% (wt/vol) palm olein in water-saturated hexane. The catalytic performance of the enzymes was evaluated by determining the changes in triglyceride (TG) composition and concentrations by reverse-phase high-performance liquid chromatography (HPLC) and the formation of free fatty acids by titration. Studies with lipase fromCandida rugosa showed that the degree of hydrolysis was reduced by drying the immobilized preparation and that the best drying time was 4 h. In all cases, the transesterification process resulted in the formation of PPP, a TG initially undetected in the oil, and increases in the concentrations of OOO (1.3–2.1-fold), OOL (1.7–4.5-fold), and OLL (1.7–4.3-fold), where P, O, and L are palmitic, oleic, and linoleic acids, respectively. SOS (where S is stearic acid), another TG not detected in the oil, was synthesized byRhizomucor miehei andPseudomonas lipases, with the latter producing more of this TG. There was a corresponding decrease in the concentrations of POP, PLP, POO, and POL. PPP concentration ranged from 1.9% (w/w) forMucor javanicus lipase to 6.2% (w/w) forPseudomonas lipase after 24 h. The greatest degree and fastest rate of change were caused byPseudomonas lipase, followed by the enzymes fromR. miehei andAspergillus niger. The effects of transesterification and hydrolysis of palm olein by the various lipases resulted in changes in the overall degree of saturation of the triglyceride components. There seems to be no clear correlation between the enzyme positional specificity and the products formed. Possible mechanisms for the formation of PPP, OOL, OLL, OOO, and SOS are discussed.

Comparative differential scanning calorimetric analysis of vegetable oils: II. Effects of cooling rate variation

The effects of scanning rates (1, 5, 10 and 20 degrees C/min) on the DSC cooling profiles of 11 vegetable oils have been determined in order to monitor peak transition temperatures, onset temperatures and crystallisation enthalpies. Triacylglycerol (TAG) profiles and iodine value analyses were used to complement the DSC data. The melted samples exhibited complicated crystallising exotherms. As the cooling rate increased, the crystallisation temperature decreased and the breadth of the crystallisation exotherm on cooling from the melt increased. In addition, the intensity of the exothermic peak increased somewhat when the cooling rate was increased. At slow cooling rates, TAG had more time to interact. It is conceivable that, at a low cooling rate (1 degree C/min), a prominent exotherm would be observed on crystallisation of vegetable oils and fats. The occurrence of one exotherm upon cooling indicated the co-crystallisation of the TAG upon slow cooling. On the basis of the corollary results obtained, vegetable oils may be differentiated by their onset temperature (Ton) values in the DSC cooling curves. Generally, there was a shift of Ton toward lower values with increasing cooling rates.

Effect of storage temperature on texture, polymorphic structure, bloom formation and sensory attributes of filled dark chocolate

The effects of 18 and 30°C storage temperatures on texture, polymorphic structure, bloom formation and sensory attributes of dark chocolate, stored for 8 weeks were studied. Results showed that storage at 18°C for 8 weeks, significantly retarded changes in filled chocolates; the chocolates were free from bloom during the storage period. In contrast, at 30°C there was an increase in the rate of fat migration and rate of change of C36 and C50, and also a decrease in texture and the polymorph structure in the coating changed to β and β′ polymorphs. However, the chocolates bloomed in the third week of storage (2 cycles). Sensory evaluation indicated that, storage at 18°C is better than 30°C, and desiccated coconut gives a pleasant flavour to the chocolate.

Thermal analysis of failed-batch palm oil by differential scanning calorimetry

Thermal behavior of palm oil samples drawn from the batch crystallizers that failed during crystallization and of a control oil that was drawn from a batch that produced good crystallization were analyzed by differential scanning calorimetry under constant heating and cooling conditions. Four polymorphs—β’2, α, β’1, and β1—were observed, and their temperatures were tabulated. A rapid and sudden surge of heat demand was observed for samples from failed crystallizers. Less supercooling values were obtained from the control oil compared to the higher values for samples from failed crystallizers. In crystallization thermograms, a sharp high-temperature exotherm (high-T peak) and a broad low-temperature exotherm (low-T peak) were observed. Low-T peaks were found almost invariably stationary at −5.1 to −5.6°C, and high-T peaks varied depending on the saturation level of the oil. A new peak, sandwiched between the high-T and low-T peaks, was observed for the control oil.

Differential scanning calorimetric analysis for monitoring the oxidation of heated oils

Abstract A simple and reliable differential scanning calorimetric (DSC) method was developed for monitoring the oxidation in heated oils. Three different types of edible oils, namely, corn oil (CO), refined, bleached and deodorised palm olein (RBDPO) and soybean oil (SO) were used in this study. The DSC method was based on the cooling thermogram of oil samples at a scanning rate of 1°C/min from −30 to −85°C. The cooling thermogram of oil showed a well-defined single crystallisation peak. Two DSC parameters of this single crystallisation peak, namely peak temperature and enthalpy were determined. In addition to the DSC method, the deterioration of heated oils was also quantified by means of seven chemical methods. A statistical comparative study was carried out on the DSC and chemical methods. The results show that there is good correlation between the DSC method and other standard chemical methods. In conclusion, the DSC method offers an alternative for the monitoring of the oxidation of heated oil due to its appreciable time-saving, use of small samples with minimal preparation, and absence of toxic chemicals.

Recent developments in differential scanning calorimetry for assessing oxidative deterioration of vegetable oils

Abstract Differential scanning calorimetry (DSC) is one of the most frequently used analytical instruments in the field of oils and fats. Today, it is already an established technique for characterizing the physical properties of many materials. The possibility of using DSC to characterize oils and fats has been realized for over 50 years. The wide variety of different applications investigated during this period reflects the diversity and complexity of oils and fats materials, as well as the versatility of the DSC technique. The main purpose of this article is to review the latest developments in the use of DSC to evaluate the oxidative deterioration of vegetable oils.

Aqueous enzymatic extraction of coconut oil

Aqueous extraction of coconut oil with various enzymes was investigated. Several enzyme preparations (cellulase, polygalacturonase, protease, and α-amylase) were used at different concentrations, pH, and temperature values to enhance oil extraction. After the oil had been released by the enzyme reaction, it was separated by centrifugation. The results showed that an enzyme mixture at 1% (w/w) each of cellulase, α-amylase, polygalacturonase, and protease at pH 7.0 and an extraction temperature of 60°C represented the most effective extraction conditions with an oil yield of 73.8%. Quality characteristics of the oil were as follows: moisture content, 0.11%; free fatty acid, 0.051%; peroxide value, 0.016 meq oxygen/kg; anisidine value, 0.026; iodine value, 8.3; saponification value, 260; and color, 0.6 (Y+5R). This technique for recovering oil from fresh coconut meat with enzymes is a significant improvement in both oil yield and quality over the traditional wet process.

Rapid identification of pork for halal authentication using the electronic nose and gas chromatography mass spectrometer with headspace analyzer

The volatile compounds of pork, other meats and meat products were studied using an electronic nose and gas chromatography mass spectrometer with headspace analyzer (GCMS-HS) for halal verification. The zNose™ was successfully employed for identification and differentiation of pork and pork sausages from beef, mutton and chicken meats and sausages which were achieved using a visual odor pattern called VaporPrint™, derived from the frequency of the surface acoustic wave (SAW) detector of the electronic nose. GCMS-HS was employed to separate and analyze the headspace gasses from samples into peaks corresponding to individual compounds for the purpose of identification. Principal component analysis (PCA) was applied for data interpretation. Analysis by PCA was able to cluster and discriminate pork from other types of meats and sausages. It was shown that PCA could provide a good separation of the samples with 67% of the total variance accounted by PC1.

Application of Fourier transform infrared spectroscopy to determine free fatty acid contents in palm olein

A simple and rapid method for the quantitative determination of free fatty acid (FFA) contents in palm olein by Fourier transform infrared (FTIR) transmission spectroscope is described. A set of palm olein samples is used as the calibration set. This set was prepared by spiking increasing amounts of oleic acid into a series of palm oleins that covers a wide range of FFA (0.08–1.04%). A partial least squares (PLS) calibration model for the prediction of FFA contents was developed, based on the spectral range 1728–1662 cm−1. This model was tested by cross-validation steps to minimize standard error of the model. The coefficient of determination (R2) and standard error were 0.997 and 0.017% of a FFA unit. Accuracy of the method was determined by comparing the FFA of a series of oleic acid-spiked palm oleins predicted by a PLS model to values obtained by the AOCS titration method. For accuracy, the difference between the mean FFA determined by the chemical method and the mean FFA determined by the FTIR method (MDa) gave FFA contents of a value of 0.00016, with the FTIR method giving a higher prediction of palm olein than the AOCS method. For reproducibility, the mean differences between duplicates (MDr) of the chemical and FTIR methods were close to zero (−0.0064 and −0.0046, respectively). The implementation of such a method as a quality control tool would eliminate the use and disposal of hazardous solvents required by the chemical method, and drastically reduce analysis time to less than 2 min/sample.

Effect of different types of maltodextrin and drying methods on physico-chemical and sensory properties of encapsulated durian flavour

A study on durian (Durio zibethinus Murr) flavour encapsulation was conducted using three types of maltodextrin – glucose syrup solid (GSS), fieldose PHS-15 and pasilli – and two drying methods: spray and freeze drying. Results showed that the three types of maltodextrin used in this study proved to be suitable for use in the preparation of durian flavour encapsulation. GSS, however, was shown to be the most suitable encapsulating agent in maintaining the original aroma of durian. For both physico-chemical and sensory analyses, durian powder dried using the freeze drying method was better in terms of moisture, water activity, fat, total sugar, colour, bulk density, degree of lump, scanning electron photomicrograph microstructure and sensory attributes, including aroma, appearance and colour, compared to the durian powder dried using the spray drying method. © 1999 Society of Chemical Industry