MONITORING OF TRANSESTERIFICATION OF PALM OIL BY DIFFERENTIAL SCANNING CALORIMETRY

Chemical transesterification was conducted to obtain triacylglycerol ( TG) containing maximum concentrations of trisaturated and triunsaturated TG in palm oil. Catalyst (sodium methoxide) concentration of 0.1–0.5%, reaction temperature of 50–92C and reaction time of 30–480 min were applied in 20 treatments. Concentrations of trisaturated and triunsaturated TG, as well as melting points and iodine values were monitored by differential scanning calorimetric (DSC) techniques. The results showed that maximum trisaturated and triunsaturated TG achieved for refined-bleached-deodorized (RBD) palm oil were 17.10 and 7.50%, respectively, using 0.42% catalyst, at 58C in 389 min. These amounts were higher compared to control (untransesterified) RBD palm oil i.e 7.45 and 4.92%, respectively. The melting points of the products were higher compared to the control, while the iodine values were not significantly changed in all of the treatments.     

动物性食品中磺胺类药物残留分析研究进展

介绍了动物性食品中磺胺类药物残留的来源和危害,着重对动物性食品中常见的磺胺类药物残留的分析方法进行了综述,为研究最有效的检测方法奠定了基础。     

DIFFERENTIAL SCANNING CALORIMETRY DETECTION OF HIGH OLEIC SUNFLOWER OIL AS AN ADULTERANT IN EXTRA-VIRGIN OLIVE OIL

Differential scanning calorimetry (DSC) was employed to detect high oleic sunflower oil (HOSo) as an adulterant in extra-virgin olive oil (EVOo) by means of cooling and heating thermograms. Addition of HOSo did not significantly alter cooling profiles of EVOo except for onset temperature of crystallization, which was significantly shifted toward lower temperature at 40% of adulterant addition. At the same percentage of adulteration, the heating profile of EVOo was significantly changed as the major endotherm broadened and the minor event became smaller and less evident. Cooling thermograms of pure oils and their admixtures were deconvoluted into three constituent exothermic peaks in an attempt to detect addition of HOSo at levels lower than 40%. Thermal properties of the two lower-temperature exotherms (area percentage, offset temperature and range of transition) were significantly changed at ≥ 20% of HOSo substitution, suggesting that DSC can be employed to detect this oil as an EVOo adulterant.

PRACTICAL APPLICATIONS

Adulteration of extra-virgin olive oil (EVOo) with cheaper oils from other vegetable sources or seeds, as well as with lower quality olive oils, is a serious concern for oil suppliers and consumers and requires the use of new analytical techniques for their detection. Differential scanning calorimetry (DSC) exhibits some advantages over the classical analytical methods as it does not require sample preparation and use of solvents, thus resulting in a reduced environmental impact. Results suggested that its application to the detection of EVOo adulteration with high oleic sunflower oil, a vegetable oil largely employed for this type of fraud, is promising with the support of the deconvolution analysis of cooling thermograms.     

OPTIMIZATION OF CAROTENE RECOVERY FROM HYDROLYZED PALM OLEIN IN ADSORPTION COLUMN CHROMATOGRAPHY USING RESPONSE SURFACE METHODOLOGY

Response Surface Methodology (RSM) for optimization of carotene recovery from hydrolyzed palm olein (HCPOlein) in adsorption chromatography was carried out. The level and interaction of three independent variables was investigated: column temperature (50 to 60C), oil loading (25 to 200 g), and mobile phase flow rate (6 to 60 mL/min). Based on the response as percentage of carotene recovery from 50 g of HP-20 adsorbent, the optimum conditions were achieved at 200 g of oil loading, column temperature at 55C, and flow rate at 33 mL/min. Up to 98% of carotene recovery was obtained under these conditions. Interaction of oil-oil, oil-flow rate and flow rate-flow rate could enhance the percentage of carotene recovery. However, oil and flow rate as single factors could significantly reduce percentage of carotene recovery. Oil loading as a single factor could positively influence the amount of carotene adsorbed. However, flow rate as a single factor and oil-oil interaction could negatively influence the amount of carotene adsorbed. The mean of difference (MD) of the experimental and predicted data for percentage of carotene recovery and the amount of carotene adsorbed were very small, −0.0067 and 0.0133, respectively. The probability (P) value showed no significant lack-of-fit for both equations in this model.     

PRODUCTION OF PALM OIL REFERENCE MATERIALS FOR THE DETERMINATION OF SOLID FAT CONTENT

ABSTRACT

Three palm oil reference materials were produced for solid fat content analysis employing the Malaysian Palm Oil Board (MPOB) Test Methods. Thirteen laboratories participated in the characterization study, where the solid fat content in palm oil, palm olein and palm stearin were identified at temperature range from 0 to 45C. The consensus values were calculated based on the acceptability of statistical results from collaborating laboratories. Both of the consensus values and their uncertainties (%) for each reference material are as follows: 71.12 ± 1.82% (0C), 54.07 ± 1.05% (10C), 37.44 ± 0.88% (15C), 24.18 ± 1.09% (20C), 13.32 ± 0.86% (25C), 7.64 ± 0.28% (30C), 4.05 ± 0.14% (35C) and 1.25 ± 0.49% (40C) for SFC of palm oil, 66.32 ± 1.93% (0C), 43.53 ± 1.32% (10C), 22.50 ± 0.78% (15C), 6.68 ± 1.14% (20C) and 1.40 ± 0.35% (25C) for SFC of palm olein, and 78.09 ± 1.23% (0C), 67.66 ± 0.71% (10C), 56.29 ± 1.18% (15C), 44.37 ± 1.13% (20C), 30.22 ± 1.25% (25C), 20.08 ± 0.58% (30C), 13.72 ± 0.32% (35C), 8.97 ± 0.72% (40C) and 5.06 ± 0.41% (45C) for solid fat content of palm stearin.

PRACTICAL APPLICATIONS

The implementation of the ISO 17025 accreditation should be encouraged for testing laboratories to assure the traceability of analysis performed. This accreditation requires the use of certified reference materials to ensure that the analysis performed is parallel to the ISO 17025 standards. However, the unavailability of palm oil reference materials will affect the implementation of such standards for laboratories that are performing palm oil analyses. Hence, this study is aimed to characterize and certify the palm oil reference materials for determination of solid fat content. The establishment of this study is hoped to increase the credibility of laboratories, which are involved in the palm oil analysis. This will also promote the Malaysia Palm Oil Board as a center for the certification of palm oil reference materials.     

MEASUREMENT OF HEAT CAPACITY FOR BORAGE SEEDS BY DIFFERENTIAL SCANNING CALORIMETRY

Specific heat capacity of borage seeds was determined by differential scanning calorimetry (DSC) in the temperature range of 5 to 80C and moisture content range of 0.47 to 30.31 % wet basis. The specific heat ranged from 0.57 to 2.48 kJ/kgK. A multiple regression model with interaction terms correlated well the specific heat to temperature (T) and moisture content (M). It was found that the interaction terms T*M and T*M² were significant (α=0.01) and thus were included in the model, and the term M*T² was insignificant. Effect of measurement techniques with DSC were also investigated in this study to ensure that true specific heat values were obtained. Seal condition of the sample holders during DSC measurement had considerable effect on the specific heat of borage seeds. The difference between the specific heat of sealed and unsealed samples increased as seed moisture content increased, especially at higher temperatures. For the measurement of the specific heat of borage seeds by DSC in the above-mentioned temperature and moisture content ranges, an average of 5.75% deviation was found between the measurement with and without blank compensation.     

动物源性食品中痕量磺胺兽药残留的分析

以多壁碳纳米管作为固相吸附材料，与高效液相色谱联用建立食品中痕量磺胺兽药残留的分析方法，对富集条件和分离条件进行了详细优化。以1μg/L的10种磺胺混合标准溶液富集100mL，9次平行测定的峰面积相对标准偏差（RSD）在2．56％～7．62％，10种磺胺的最低检测限（S／N=3）在2．1ng／L～9．3ng／L，线性范围均在0．2μg／L-15μg/L之间。实际样品加标回收率范围为70.18％～85．68％，相对标准偏差范围为1．02％～14．56％。     

一类四阶微分方程解的渐近性态

利用Ｌｉａｐｕｎｏｖ函数研究一类四阶微分方程ｘ￣（４）＋α＿１ｘ￣（３）＋α＿２ｘ￣（２）＋α＿３ｘ＋ｈ（ｘ）＝Ｐ（ｔ，ｘ，ｘ＇，ｘ￣（２），ｘ￣（３））解的渐近性态。它要求所得结果，不需要函数ｈ（ｘ）的可微性，甚至可以是不连续的，推广和发展了文献［１～５］中的某些主要结果。     

动物性食品中兽药残留现状及对策

介绍了我国兽药残留问题的现状，详细分析了兽药残留的危害和兽药残留的原因，概述了兽药残留检测方法的研究进展，并提出了解决兽药残留问题的对策和建议。     

ULTRAVIOLET SPECTROPHOTOMETRIC DETERMINATION OF PROTEIN IN SOME FOOD PRODUCTS

SUMMARY— The spectrophotometric method of estimating the protein content of whole milk at wavelength 280 nm (Nakai and Le, 1970) was modifed for corned beef, flour, bean and egg yolk. A clear solution was obtained by adding 50% sulfuric acid or 2N sodium hydroxide with and without 7–8M urea depending on solubility of the food products. The protein content was calculated from the absorbance at 280, 243 or 215 nm on o spectrophotometer. The correlation coefficient between the absorbance and the protein by Kjeldahl method was 0.99, 0.99, 0.99 and 0.99 with the coefficient of variability of Kjeldahl protein for absorbance of 1.8, 4.1, 3.8 and 4.1% for bean, corned beef, egg yolk and flour, respectively.