Displaying publications 1 - 20 of 201 in total

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  1. Che Man YB, Tan CP
    Phytochem Anal, 2002 May-Jun;13(3):142-51.
    PMID: 12099104
    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.
  2. Tan CP, Man YC
    Phytochem Anal, 2002 May-Jun;13(3):129-41.
    PMID: 12099103
    The melting curves of 11 vegetable oils have been characterised. Vegetable oil samples that were cooled at a constant rate (5 degrees C/min) from the melt showed between one and seven melting endotherms upon heating at four different heating rates (1, 5, 10 and 20 degrees C/min) in a differential scanning calorimeter (DSC). Triacylglycerol (TAG) profiles and iodine value analyses were used to complement the DSC data. Generally, the melting transition temperature shifted to higher values with increased rates of heating. The breadth of the melting endotherm and the area under the melting peak also increased with increasing heating rate. Although the number of endothermic peaks was dependent on heating rate, the melting curves of the oil samples were not straightforward in that there was no correlation between the number of endothermic peaks and heating rates. Multiple melting behaviour in DSC experiments with different heating rates could be explained by: (1) the melting of TAG populations with different melting points; and (2) TAG crystal reorganisation effects. On the basis of the corollary results obtained, vegetable oils and fats may be distinguished from their offset-temperature (Toff) values in the DSC melting curves. The results showed that Toff values of all oil samples were significantly (p < 0.01) different in the melting curves scanned at four different scanning rates. These calorimetric results indicate that DSC is a valuable technique for studying vegetable oils.
  3. Lo SK, Baharin BS, Tan CP, Lai OM
    J Chromatogr Sci, 2004 Mar;42(3):145-54.
    PMID: 15023251
    Separation of 1,2(2,3)- and 1,3-positional isomers of diacylglycerols (DAG) from vegetable oils by reversed-phase high-performance liquid chromatography (RP-HPLC) is investigated. The method is based on isocratic elution using 100% acetonitrile and UV detection at 205 nm. The following elution order of DAG molecular species is identified: 1,3-dilinolein < 1,2-dilinolein < 1,3-dimyristin < 1-oleoyl-3-linoleoyl-glycerol < 1,2-dimyristoyl-rac-glycerol < 1(2)-oleoyl-2(3)-linoleoyl-glycerol < 1-linolenoyl-3-stearoyl-glycerol < 1(2)-linolenoyl-2(3)-stearoyl-glycerol < 1,3-diolein < 1-palmitoyl-3-oleoyl-glycerol < 1,2-dioleoyl-sn-glycerol < 1(2)-palmitoyl-2(3)-oleoyl-glycerol < 1-linoleoyl-3-stearoyl-glycerol < 1,3-dipalmitin < 1(2)-linoleoyl-2(3)-stearoyl-glycerol < 1-oleoyl-3-stearoyl-glycerol < 1,2-dipalmitoyl-rac-glycerol < 1-palmitoyl-3-stearoyl-sn-glycerol < 1,3-distearin < 1,2-distearoyl-rac-glycerol. Linearity is observed over three orders of magnitude. Limits of detection and quantitation range 0.2-0.7 microg/mL for 1,3-dilinolein to 0.6-1.9 microg/mL for 1,2-dioleoyl-sn-glycerol, respectively. Precision and accuracy of the method are also demonstrated. The method is developed to separate mixtures of DAG molecular species produced from edible oils.
  4. Azila NM, Tan CP
    Med J Malaysia, 2005 Aug;60 Suppl D:35-40.
    PMID: 16315622
    Accreditation is a process by which official accrediting bodies evaluate institutions using a set of criteria and standards, following established procedures, to ensure a high quality of education needed to produce highly competent graduates. Additional objectives include (1) ensuring quality institutional functioning, (2) strengthening capabilities of educational institutions for service to the nation and (3) improving public confidence in medical schools. The accreditation process provides an opportunity for the institution to critically reflect upon all the aspects of its programme and the level of compliance or attainment of the requirements. The self-evaluation exercise, which identifies strengths and weaknesses, is perceived as formative. It is envisaged that eventually institutions will adopt a learning culture for curriculum development, implementation, monitoring and matching the outcomes. In conclusion, periodic accreditation activities can act as a "monitoring" system to ensure that the quality of medical education is maintained according to established standards.
  5. Tan CP, Rokiah P
    Med J Malaysia, 2005 Aug;60 Suppl D:48-53.
    PMID: 16315624
    Formative and summative student assessment has always been of concern to medical teachers, and this is especially important at the level of graduating doctors. The effectiveness and comprehensiveness of the clinical training provided is tested with the use of clinical cases, either with real patients who have genuine medical conditions, or with the use of standardised patients who are trained to simulate accurately actual patients. The Objective Structured Clinical Examination (OSCE) is one method of assessing the adequacy of clinical skills of medical students, and their level of competence. It can be used to test a variety of skills such as history taking (communication and interpersonal skills) and performing aspects of physical examination, undertaking emergency procedures, and interpreting investigational data. It can also be used to ensure an adequate depth and breadth of coverage of clinical skills expected of a graduating doctor.
  6. Sim SM, Azila NM, Lian LH, Tan CP, Tan NH
    Ann Acad Med Singap, 2006 Sep;35(9):634-41.
    PMID: 17051280
    INTRODUCTION: A process-oriented instrument was developed for the summative assessment of student performance during problem-based learning (PBL) tutorials. This study evaluated (1) the acceptability of the instrument by tutors and (2) the consistency of assessment scores by different raters.

    MATERIALS AND METHODS: A survey of the tutors who had used the instrument was conducted to determine whether the assessment instrument or form was user-friendly. The 4 competencies assessed, using a 5-point rating scale, were (1) participation and communication skills, (2) cooperation or team-building skills, (3) comprehension or reasoning skills and (4) knowledge or information-gathering skills. Tutors were given a set of criteria guidelines for scoring the students' performance in these 4 competencies. Tutors were not attached to a particular PBL group, but took turns to facilitate different groups on different case or problem discussions. Assessment scores for one cohort of undergraduate medical students in their respective PBL groups in Year I (2003/2004) and Year II (2004/2005) were analysed. The consistency of scores was analysed using intraclass correlation.

    RESULTS: The majority of the tutors surveyed expressed no difficulty in using the instrument and agreed that it helped them assess the students fairly. Analysis of the scores obtained for the above cohort indicated that the different raters were relatively consistent in their assessment of student performance, despite a small number consistently showing either "strict" or "indiscriminate" rating practice.

    CONCLUSION: The instrument designed for the assessment of student performance in the PBL tutorial classroom setting is user-friendly and is reliable when used judiciously with the criteria guidelines provided.

  7. Lo SK, Cheong LZ, Arifin N, Tan CP, Long K, Yusoff MS, et al.
    J Agric Food Chem, 2007 Jul 11;55(14):5595-603.
    PMID: 17571899
    Diacylglycerol (DAG) and triacylglycerol (TAG) as responses on optimization of DAG production using a dual response approach of response surface methodology were investigated. This approach takes the molecular equilibrium of DAG into account and allows for the optimization of reaction conditions to achieve maximum DAG and minimum TAG yields. The esterification reaction was optimized with four factors using a central composite rotatable design. The following optimized conditions yielded 48 wt % DAG and 14 wt % TAG: reaction temperature of 66.29 degrees C, enzyme dosage of 4 wt %, fatty acid/glycerol molar ratio of 2.14, and reaction time of 4.14 h. Similar results were achieved when the process was scaled up to a 10 kg production in a pilot packed-bed enzyme reactor. Lipozyme RM IM did not show any significant activity losses or changes in fatty acid selectivity on DAG synthesis during the 10 pilot productions. However, lipozyme RM IM displayed higher selectivity toward the production of oleic acid-enriched DAG. The purity of DAG oil after purification was 92 wt %.
  8. Mirhosseini H, Tan CP, Hamid NS, Yusof S
    J Agric Food Chem, 2007 Sep 19;55(19):7659-66.
    PMID: 17708646
    The possible relationships between the main emulsion components (namely, Arabic gum, xanthan gum, and orange oil) and the physicochemical properties of orange beverage emulsion were evaluated by using response surface methodology. The physicochemical emulsion property variables considered as response variables were emulsion stability, viscosity, fluid behavior, zeta-potential, and electrophoretic mobility. The independent variables had the most and least significant ( p < 0.05) effect on viscosity and zeta-potential, respectively. The quadratic effect of orange oil and Arabic gum, the interaction effect of Arabic gum and xanthan gum, and the main effect of Arabic gum were the most significant ( p < 0.05) effects on turbidity loss rate, viscosity, viscosity ratio, and mobility, respectively. The main effect of Arabic gum was found to be significant ( p < 0.05) in all response variables except for turbidity loss rate. The nonlinear regression equations were significantly ( p < 0.05) fitted for all response variables with high R (2) values (>0.86), which had no indication of lack of fit. The results indicated that a combined level of 10.78% (w/w) Arabic gum, 0.56% (w/w) xanthan gum, and 15.27% (w/w) orange oil was predicted to provide the overall optimum region in terms of physicochemical properties studied. No significant ( p > 0.05) difference between the experimental and the predicted values confirmed the adequacy of response surface equations.
  9. Ng CF, Lum LC, Ismail NA, Tan LH, Tan CP
    J Clin Virol, 2007 Nov;40(3):202-6.
    PMID: 17928264 DOI: 10.1016/j.jcv.2007.08.017
    BACKGROUND: Difficulties in the classification of dengue infection have been documented. Such difficulties could be due to the low awareness of the World Health Organization diagnostic guidelines among clinicians.
    OBJECTIVE: To study the diagnostic practices of clinicians in classifying patients as dengue fever (DF) or dengue haemorrhagic fever (DHF)/dengue shock syndrome (DSS) at the time of discharge during an outbreak.
    METHODS: A prospective descriptive study of clinical features and disease classification in adult and pediatric dengue patients in the University of Malaya Medical Centre.
    RESULTS: Five hundred and twenty adult and 191 pediatric patients were enrolled. Thrombocytopenia and evidence of plasma leakage were present in 8% of adult and 19% of pediatric patients. Of these, 93% and 49%, respectively, were given the discharge diagnoses of DF instead of DHF/DSS. Hemoconcentration, serous effusion and thrombocytopenia were not recognized in clinicians' discharge diagnosis of DHF/DSS for adult patients. The receiver operating characteristic (ROC) curve suggested a lack of consistency in the use of WHO guidelines in establishing DHF/DSS in adult patients, while implying otherwise for pediatric patients.
    CONCLUSION: DHF/DSS is an under-recognized condition by clinicians managing these patients. This can affect the case fatality rate of DHF/DSS and the economic burden of the disease. The lack of awareness in disease manifestations especially plasma leakage, can lead to delayed recognition of DHF/DSS.
    Study site: Outpatient department and inpatients, adult medical and pediatric wards, University Malaya Medical Center (UMMC), Kuala Lumpur, Malaysia
  10. Mirhosseini H, Tan CP, Yusof S, Hamid NS
    Phytochem Anal, 2008 Sep-Oct;19(5):429-37.
    PMID: 18435528 DOI: 10.1002/pca.1068
    Solid-phase microextraction (SPME) coupled to gas chromatography has been applied for the headspace analysis (HS) of 12 target flavour compounds in a model orange beverage emulsion. The main volatile flavour compounds studied were: acetaldehyde, ethyl acetate, alpha-pinene, ethyl butyrate, beta-pinene, myrcene, limonene, gamma-terpinene, octanal, decanal, linalool and citral (neral plus geranial). After screening the fibre type, the effect of other HS-SPME variables such as adsorption temperature (25-55 degrees C), extraction time (10-40 min), sample concentration (1-100% w/w), sample amount (5-10 g) and salt amount (0-30% w/w) were determined using a two-level fractional factorial design (2(5-2)) that was expanded further to a central composite design. It was found that an extraction process using a carboxen-polydimethylsiloxane fibre coating at 15 masculineC for 50 min with 5 g of diluted emulsion 1% (w/w) and 30% (w/w) of sodium chloride under stirring mode resulted in the highest HS extraction efficiency. For all volatile flavour compounds, the linearity values were accurate in the concentration ranges studied (r(2) > 0.97). Average recoveries that ranged from 90.3 to 124.8% showed a good accuracy for the optimised method. The relative standard deviation for six replicates of all volatile flavour compounds was found to be less than 15%. For all volatile flavour compounds, the limit of detection ranged from 0.20 to 1.69 mg/L.
  11. Thayan R, Huat TL, See LL, Tan CP, Khairullah NS, Yusof R, et al.
    Trans R Soc Trop Med Hyg, 2009 Apr;103(4):413-9.
    PMID: 19203772 DOI: 10.1016/j.trstmh.2008.12.018
    Dengue infection is a major public health problem affecting millions of people living in tropical countries. With no suitable vaccines and specific antiviral drugs, treatment for dengue is usually symptomatic and supportive. Early diagnosis and recognition of severe disease is therefore crucial for better management of the patient. Two-dimension electrophoresis was used to identify disease-associated proteins that can be used for diagnosis and as drug targets for treatment. Two markers, identified by mass spectrometry analysis as alpha1-antitrypsin and NS1 proteins were found to be upregulated in dengue fever (DF; n=10) and dengue haemorrhagic fever (DHF; n=10) patients compared with healthy individuals (n=8). Both alpha1-antitrypsin and NS1 proteins were overexpressed two-fold in DHF patients compared with DF patients. Our study suggests that alpha1-antitrypsin and NS1 protein could be used as biomarkers as early indicators of DHF risk among patients with suspected dengue infection.
  12. Leong WF, Che Man YB, Lai OM, Long K, Misran M, Tan CP
    J Agric Food Chem, 2009 Sep 23;57(18):8426-33.
    PMID: 19694442 DOI: 10.1021/jf901853y
    The purpose of this study was to optimize the parameters involved in the production of water-soluble phytosterol microemulsions for use in the food industry. In this study, response surface methodology (RSM) was employed to model and optimize four of the processing parameters, namely, the number of cycles of high-pressure homogenization (1-9 cycles), the pressure used for high-pressure homogenization (100-500 bar), the evaporation temperature (30-70 degrees C), and the concentration ratio of microemulsions (1-5). All responses-particle size (PS), polydispersity index (PDI), and percent ethanol residual (%ER)-were well fit by a reduced cubic model obtained by multiple regression after manual elimination. The coefficient of determination (R(2)) and absolute average deviation (AAD) value for PS, PDI, and %ER were 0.9628 and 0.5398%, 0.9953 and 0.7077%, and 0.9989 and 1.0457%, respectively. The optimized processing parameters were 4.88 (approximately 5) homogenization cycles, homogenization pressure of 400 bar, evaporation temperature of 44.5 degrees C, and concentration ratio of microemulsions of 2.34 cycles (approximately 2 cycles) of high-pressure homogenization. The corresponding responses for the optimized preparation condition were a minimal particle size of 328 nm, minimal polydispersity index of 0.159, and <0.1% of ethanol residual. The chi-square test verified the model, whereby the experimental values of PS, PDI, and %ER agreed with the predicted values at a 0.05 level of significance.
  13. Kong KW, Khoo HE, Prasad KN, Ismail A, Tan CP, Rajab NF
    Molecules, 2010 Feb 23;15(2):959-87.
    PMID: 20335956 DOI: 10.3390/molecules15020959
    By-products derived from food processing are attractive source for their valuable bioactive components and color pigments. These by-products are useful for development as functional foods, nutraceuticals, food ingredients, additives, and also as cosmetic products. Lycopene is a bioactive red colored pigment naturally occurring in plants. Industrial by-products obtained from the plants are the good sources of lycopene. Interest in lycopene is increasing due to increasing evidence proving its preventive properties toward numerous diseases. In vitro, in vivo and ex vivo studies have demonstrated that lycopene-rich foods are inversely associated to diseases such as cancers, cardiovascular diseases, diabetes, and others. This paper also reviews the properties, absorption, transportation, and distribution of lycopene and its by-products in human body. The mechanism of action and interaction of lycopene with other bioactive compounds are also discussed, because these are the crucial features for beneficial role of lycopene. However, information on the effect of food processing on lycopene stability and availability was discussed for better understanding of its characteristics.
  14. Mirhosseini H, Tan CP
    J Sci Food Agric, 2010 Jun;90(8):1308-16.
    PMID: 20474048 DOI: 10.1002/jsfa.3928
    The constituents in a food emulsion interact with each other, either physically or chemically, determining the overall physico-chemical and organoleptic properties of the final product. Thus, the main objective of present study was to investigate the effect of emulsion components on beverage emulsion properties.
  15. Cheong JN, Mirhosseini H, Tan CP
    Int J Food Sci Nutr, 2010 Jun;61(4):417-24.
    PMID: 20151850 DOI: 10.3109/09637481003591574
    The main objective of the present study was to investigate the effect of polyoxyethylene sorbitan esters and sodium caseinate on physicochemical properties of palm-based functional lipid nanodispersions prepared by the emulsification-evaporation technique. The results indicated that the average droplet size increased significantly (P < 0.05) by increasing the chain length of fatty acids and also by increasing the hydrophile-lipophile balance value. Among the prepared nanodispersions, the nanoemulsion containing Polysorbate 20 showed the smallest average droplet size (202 nm) and narrowest size distribution for tocopherol-tocotrienol nanodispersions, while sodium caseinate-stabilized nanodispersions containing carotenoids had the largest average droplet size (386 nm), thus indicating a greater emulsifying role for Polysorbate 20 compared with sodium caseinate.
  16. Cheong LZ, Tan CP, Long K, Affandi Yusoff MS, Lai OM
    J Sci Food Agric, 2010 Oct;90(13):2310-7.
    PMID: 20661900 DOI: 10.1002/jsfa.4088
    Diacylglycerol (DAG), which has health-enhancing properties, is sometimes added to bakery shortening to produce baked products with enhanced physical functionality. Nevertheless, the quantity present is often too little to exert any positive healthful effects. This research aimed to produce bakery shortenings containing significant amounts of palm diacyglycerol (PDG). Physicochemical, textural and viscoelastic properties of the PDG bakery shortenings during 3 months storage were evaluated and compared with those of commercial bakery shortening (CS).
  17. Anarjan N, Tan CP, Ling TC, Lye KL, Malmiri HJ, Nehdi IA, et al.
    J Agric Food Chem, 2011 Aug 24;59(16):8733-41.
    PMID: 21726079 DOI: 10.1021/jf201314u
    A simplex centroid mixture design was used to study the interactions between two chosen solvents, dichloromethane (DCM) and acetone (ACT), as organic-phase components in the formation and physicochemical characterization and cellular uptake of astaxanthin nanodispersions produced using precipitation and condensation processes. Full cubic or quadratic regression models with acceptable determination coefficients were obtained for all of the studied responses. Multiple-response optimization predicted that the organic phase with 38% (w/w) DCM and 62% (w/w) ACT yielded astaxanthin nanodispersions with the minimum particle size (106 nm), polydispersity index (0.191), and total astaxanthin loss (12.7%, w/w) and the maximum cellular uptake (2981 fmol/cell). Astaxanthin cellular uptake from the produced nanodispersions also showed a good correlation with their particle size distributions and astaxanthin trans/cis isomerization ratios. The absence of significant (p > 0.05) differences between the experimental and predicted values of the response variables confirmed the adequacy of the fitted models.
  18. Mehrnoush A, Tan CP, Hamed M, Aziz NA, Ling TC
    Food Chem, 2011 Sep 1;128(1):158-64.
    PMID: 25214343 DOI: 10.1016/j.foodchem.2011.03.012
    This study investigated the possible relationship between the encapsulation variables, namely serine protease content (9-50mg/ml, X1), Arabic gum (0.2-10%(w/w), X2), maltodextrin (2-5%(w/w), X3) and calcium chloride (1.3-5.5%(w/w), X4) on the enzymatic properties of encapsulated serine protease. The study demonstrated that Arabic gum, maltodextrin and calcium chloride, as coating agents, protected serine protease from activity loss during freeze-drying. The overall optimum region resulted in a suitable freeze drying condition with a yield of 92% for the encapsulated serine protease, were obtained using 29.5mg/ml serine protease content, 5.1%(w/w) Arabic gum, 3.5%(w/w) maltodextrin and 3.4%(w/w) calcium chloride. It was found that the interaction effect of Arabic gum and calcium chloride improved the serine protease activity, and Arabic gum was the most effective amongst the examined coating agents. Thus, Arabic gum should be considered as potential protection in freeze drying of serine protease.
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