Temperature effects on the determination of oxidative stability with the metrohm rancimat

Reproducibility of Oil Stability Index (OSI) values determined on the Metrohm Rancimat was measured with a single run and between experimental runs. Within a single experiment, a range of 0.13 h and a standard deviation of 0.066 h were determined. For multiple experiments, standard deviations of 0.24 and 0.26 were obtained for soybean and low-erucic rapeseed oil, respectively. The effect of temperature was determined for safflower, soybean, lowerucic rapeseed, corn, peanut and olive oils. A linear relationship was established between log (OSI) and temperature. The linear equation obtained for soybean oil was utilized to calculate variability of the OSI due to temperature differences in the heating block.     

Oil stability index correlated with sensory determination of oxidative stability in canola oil

The usefulness of the Oil Stability Index (OSI) as an accelerated oxidative stability test for canola oil was studied by correlating the OSI with the induction period as determined by sensory analysis. Canola oil was treated by holding it for differing times (0, 1, 2, 3, 4, and 6 d) at elevated temperature (60°C) in the dark with agitation. The sensory induction period (SIP) was determined by storing the five treatments of oil and the control at 60°C in the dark with agitation and removing aliquots of oil for a nine-member sensory panel to evaluate over a 9-d period. The time it took for a treatment to reach an average sensory score of 5 (10-point scoring scale) was defined as the treatment’s SIP. OSI values were obtained on day 0 using a heating block temperature of 110°C and an air pressure of 6 psi. The relationship between SIP and OSI had a 0.89 coefficient of determination (r ²). This relationship may be sufficiently strong to warrant use of the OSI in industry applications but may not be ideal for more precise experimental studies of canola oil shelf life.     

Synergistic effect of metal deactivator and antioxidant on oxidation stability of metal contaminated Jatropha biodiesel

Biodiesel is relatively unstable on storage and European biodiesel standard EN-14214 calls for determining oxidation stability at 110 °C with a minimum induction time of 6 h by the Rancimat method (EN-14112). According to proposed National Mission on biodiesel in India, we have undertaken studies on stability of biodiesel from tree borne non-edible oil seeds Jatropha. Neat Jatropha biodiesel exhibited oxidation stability of 3.95 h. It is found possible to meet the desired EN specification for neat Jatropha biodiesel and metal contaminated Jatropha biodiesel by using antioxidants; it will have a cost implication, as antioxidants are costly chemicals. Research was conducted to increase the oxidation stability of metal contaminated Jatropha biodiesel by doping metal deactivator with antioxidant, with varying concentrations in order to meet the aforementioned standard required for oxidation stability. It was found that usage of antioxidant can be reduced by 30–50%, therefore the cost, even if very small amount of metal deactivator is doped in Jatropha biodiesel to meet EN-14112 specification.     

Effects of processing on the oxidative stability of soybean oil produced in Mexico

The stability parameters of 22 samples of soybean oil produced in Mexico were determined. Samples were analyzed for moisture, color, free fatty acids, peroxide value, p-anisidine value, fatty acid profile, metals, flavor, and Rancimat test for oxidative stability. Results obtained were compared with the stability parameters of soybean oil sproduced in the United States and Costa Rica. The fatty acid profile in all samples analyzed corresponded to the expected profile for a 100% soybean oil. Sixty-four percent of the oils had oxidative stabilities similar to those reported for soybean oils from the United States and Costa Rica. This suggests that in spite of the good quality, the soybean oil production process in Mexico needs further improvement. Especially important is maintaining appropriate control during the degumming and bleaching steps. Special consideration should be given to preserving the natural antioxidants present in the oil.     

油脂酸败仪操作参数对油茶籽油OSI测定及其货架期预测的影响

研究了油脂氧化酸败测定仪的操作参数温度、空气流速、样品量对油茶籽油化稳定指数(Oxidative Stability Index),温度系数,Q10的测定及货架期预测的影响。为了这个目的,试验数据建立了完全二次模型并且进行了方差分析,结果表明温度和空气流速对OSI的影响显著(P0.01)。此外,通过简化的线性模型检测表明在温度占主导效应的同时,与样品量相比,空气流速对油茶籽油OSI的测定也有较大的影响(P0.05)。此项研究获得的油茶籽油温度系数平均值为-3.02×10-2。Q10的计算平均值为2.02,表明温度每升高10℃油茶籽油的OSI减半。计算出的20℃下的OSI表现出明显不同,说明空气流量和样品量对油茶籽油货架期的预测有着很大影响。因此,在油脂氧化酸败测定过程中选择一个合适的操作参数水平会降低长期室温贮藏和加速氧化对货架期预测的影响。     

Brazilian encapsulated fish oils: Oxidative stability and fatty acid composition

Encapsulated fish oils are extensively commercialized in Brazil. These products could have an effect in the reduction of heart diseases because of their high content of polyunsaturated fatty acids. However, information about their composition and quality are still lacking. Fatty acid composition, oxidative stability (Rancimat, 80°C, 2.5 g sample and 8.3 L/h air), peroxide value (PV), and polar compound content were determined in sixteen trademarked encapsulated fish and cod-liver oils, purchased from Brazilian markets. The highly polyunsaturated fatty acid (eicosapentaenoic acid+docosahexaenoic acid) level appear to be typical of marine oils (16.2 and 32.1%). The PV ranged from 2.1 to 20.3 meq/kg, which is considered high, whereas the Rancimat induction periods varied from 1.95 to 8.45 h. The samples analyzed contained from 0.1 to 8.3% polar components. In some cases, both composition and quality were inadequate for this kind of product. One of the samples did not contain cod-liver oil, it appears that it contained soybean oil. Presented at the 6th Latin American Congress and Exhibit on Fats and Oil Processing, LA-AOCS, Campinas, SP, Brazil, Sept. 1995.     

牡丹籽油优势抗氧化剂研究

对牡丹籽油及其他5种植物油的基本理化指标进行了测定比较。牡丹籽油酸值(KOH)(2.034 mg/g)、过氧化值(0.286 mmol/kg)均在国标限值以内,碘值(I)185.8 g/100 g,说明其为干性油,皂化值(KOH)(188.1 mg/g)符合国家规定注射用油标准,较其他5种植物油品质好。选用迷迭香提取物、α-生育酚、TBHQ 3种抗氧化剂,并选择柠檬酸作为抗氧化增效剂,以不同比例组合加入牡丹籽油中,采用Rancimat法测定其氧化诱导时间(OSI)以确定优势抗氧化剂,结合温度外推法推测牡丹籽油货架期。最终遴选0.02%TBHQ+0.01%柠檬酸为优势抗氧化剂,推得20℃下添加此抗氧化剂的牡丹籽油货架期为3 737 h,约是未加抗氧化剂牡丹籽油的27倍,显著提高了牡丹籽油的耐贮藏性。     

固定化酶催化抗坏血酸硬脂酸酯的合成及抗氧化活性

研究液体脂肪酶CALB的固定化及其催化抗坏血酸和硬脂酸的酯化反应合成抗坏血酸硬脂酸酯（AS）。以大孔吸附树脂为固定化载体,对液体脂肪酶CALB进行固定,固定化负载率可达72%。探讨不同反应变量（反应溶剂、温度、酶添加量、底物物质的量比、底物浓度和分子筛添加量）对酯化反应的影响,并对反应条件进行优化,优化的反应条件为：反应温度72℃,底物物质的量比1∶12,酶添加量22.49%（质量分数）,反应24 h,在此优化条件下,AS产率可达（41.33±1.81）%。对产品进行分离纯化,并采用质谱等检测确定产品为AS。通过Rancimat实验发现AS具有良好的抗氧化性,添加100 mg/kg AS的玉米油氧化诱导期与添加50 mg/kg TBHQ的玉米油氧化诱导期接近。     

Influence of the Rancimat Apparatus Operating Parameters on Oxidative Stability Determination of Cold-Pressed Camelina and Hemp Seed Oil

The study investigates the impact of operating parameters such as temperature (90, 100, 110, 120 °C), airflow rate (10, 15, 20 L h⁻¹), and sample weight (3, 6, 9 g) on the oxidative stability of cold-pressed camelina and hemp seed oils using the Rancimat apparatus. Conducted analysis indicates a significant influence of temperature on oils' induction time. Moreover, higher airflows should be selected at high analysis temperatures. Based on the calculated parameters of the oxidation kinetics, it was shown that hemp oil has higher activation energy values than camelina oil. Response surface methodology (RSM) indicates that to minimize the determination time of camelina oil oxidation, the following analysis conditions should be selected: sample weight (SW) = 33.5 g, airflow (AF) = 20 L h⁻¹, and temperature (T) = 120 °C. However, for hemp oil, these parameters should be SW = 5.56 g, AF = 15 L h⁻¹, T = 120 °C. Sample mass does not significantly impact oils induction time, which depends mainly on the temperature and airflow. Practical applications: The conducted research shows that the parameters of the cold-pressed camelina and hemp oils oxidative stability have to be determined experimentally. The determined parameters for assessing the oxidative stability will reduce the analysis time and the possibility of interpolating the obtained result at different temperatures and analysis parameters.