大豆油中动力学参数检测方案(食用油品分析)

智能文字提取功能测试中

2IDiSTAM Application of the Oxitestmethodto estimate the kinetic parameters in soybean oilunder accelerated storage conditions Packlab Mora， L.*， Limbo， S.*， Maiocchi， p**. Department of Food Science and Microbiology (DISTAM)， University of Milan， Via G. Celoria， 2-20133 Milan-Italy. Phone：+39 02 50316660； Velp Scientifica srl， via Stazione， 16-20040 Usmate (MI)； analyticalsupport@velp.it A number of accelerated methods have been developed to test the resistance of edible fats and oils to oxidation. All theseaccelerated methods involve the use of elevated temperatures because of the rate of the oxidative reaction is exponentiallyrelated to the temperature.Oxitest reactor (Velp Scientifica， Usmate-MI) has been successfully used to measure the resistanceto oxidation of vegetable oils and fatty foods.In spite of that， the measure of the oxidative degradation kinetics of food duringshelf life represents the main goal for the complete development of the reactor.In order to assess this instrumental capacity apreliminary study was carried out comparing the Oxitest response (IP) with the traditional measure of the Peroxide Value (PV).Soybean oil was used as lipid matrix due to its high susceptibility to oxidation (high PUFA content) and was stored at differenttemperatures in opened glass bottles. For each temperature， the PV numbers of the vegetable oil and the IP values obtained from the Oxitest@ were recorded andplotted against the storage time. The increase of the PVs and the decrease of IPs followed a zero order kinetic： therefore thereaction rate constant (k) for each temperature was simply estimated (Table 1). Index 25℃ 50°C 70°C 90°C k(IP)h-1 0，0603 0.092 0.6761.817 k(PV)h-0，0259 0.2812.6937.683 Table 1. Constant rates for IP and PV variations at different temperatures Figure 1 and 2 show the ability of both PV and Oxitest (IP) to measure theoxidative degree of soybean oil exposed at growing temperatures. TheArrhenius equation (InK=InA -Ea/RT) was used to determine theactivation energy (Ea) of the oxidation reaction for each index. Also， atemperature acceleration factor，(Q10) based on the increase in oxidationrate from a 10°℃ increase in temperature， was calculated from the slopesof the lines (Table 2). Table 2. Arrhenius parameters and Q10 for lipid oxidation described by the two indexes Figure 1. Change of the rate constant (k) at different temperatures (PV) The results summarized in Table 2 show a similarity between IP and PVresponses. Figure 3 shows the good correlation that exists between the twomethods at 70°C. Similar results were obtained also for the others storagetemperatures (data not shown). Figure 2. Change of the rate constant (k) at different temperatures (IP) Figure 3. Correlation between IP and PV at 70°℃ The results show that the Oxitest could be a helpful solution for monitoring the vegetable oil oxidation. It could be usedalternatively to traditional and time-consuming methodswith several advantages： analyticalrapidity， easiness of use，reproducibility and reduced production of chemical wastes. Oxitest is also a promising instrument in order to study oil shelf-lifein accelerated conditions. A good level of correlation with a traditional method like Peroxide Value was found (R>0，98). ( 1 ) Farhoosh R ， Niazmand R ， Rezaei M， Sarabi M (2008). Kinetic parameter determination of vegetable oil oxidatio n under Rancimat ) test conditions. Eur J Lipid Sci Technol 110：587-592. ( 2 )H y ung YC . (1997). Reaction Mechanisms and Kinetics of Antioxidant Using Arrhenius Equatio n in Soybean Oil Oxidation， J. Food ) Sci. Nutr. 2： 6-10. 3) Mora L， Piergiovanni L， Limbo S， Maiocchi P.(2009). Valutazione della stabilita ossidativa di oli vegetali mediante reattore per test di ossidazioneoxitest. Industrie Alimentari， 48：51-56.         人们已经开发了许多快速测定食用油脂抗氧化性的方法。所有这些加速法都涉及使用高温，因为氧化反应的速度与温度有关。油脂氧化分析已成功用于油类和高脂肪食物的检测。      油脂氧化分析仪开发的主要目标就是通过食物氧化降解动力学的测量推算食物货架期。为了评估油脂氧化分析仪的性能，和传统的过氧化值(PV)测量进行了方法比较。 实验仪器：油脂氧化分析仪（意大利VELP）实验过程解析 在每个温度阶段，记录植物油的PV值和从油脂氧化分析获得的IP值。遵循零阶动力学：因此每个温度下的反应速率常数(k)被简单地估算如下表。 图1和图2显示了PV和油脂氧化分析 (IP)在温度变化下，暴露在氧气中大豆油的氧化程度。采用Arrhenius方程(lnK=lnA-Ea/RT)测定各指标的氧化反应活化能(Ea)。  图1   不同温度下速率常数(k)的变化(PV)图2   不同温度下速率常数(k)的变化(IP)同样，一个温度加速因子(Q10)基于氧化的增加温度升高10℃时的速率，由斜率计算得到下表。图3显示了两者之间在70℃时存在良好的相关性。图3   在70℃时IP和PV的相关性实验结果论述结果表明，采用合适氧饱和度法可作为植物油氧化监测的一种有效方法。油脂氧化分析分析速度快，易于使用，还减少了化学废物的产生。基本可以替代传统耗时的方法，经实验，与过氧化值等传统方法有良好的相关性(R>0.98)。油脂氧化分析也是一种未来有前景的研究油品货架期的仪器。