THE RECOVERY OF USED FRYING OILS WITH VARIOUS ADSORBENTS

The recovery of used frying oils is of commercial and economic importance. One additional reuse of recovered oil could provide considerable savings to the food processors. Seven commonly used filter aids: Silasorb, Britesorb, HB 600, Purifry, Frypowder, Activated Carbon, and Magnesol, as well as two commercially unavailable adsorbents, Sorbead AF and Calsilite were studied. A number of AOCS official methods were used to evaluate their adsorptiveness, free fatty acids (FFA), conjugated diene value (CDV), total polar components (TPC), oxidative stability index (OSI), color and viscosity (V). High performance size exclusion chromatography was employed to determine the amount of polymers and low molecular weight compounds. When heated to 150C prior to filtration, HB 600 was found to reduce FFA content by 84.5%. Frypowder improved oil stability by 38.3%, and Magnesol lightened oil color by 46.3%. After statistical analysis of the data, five of them were selected, two or three of which were blended to obtain the most effective combination. The blending of HB 600 and Magnesol reduced FFA and TPC by 90.8–93.7% and 6.0–17.8%, respectively, and improved oil stability by 23.4–24.7%. The adsorbent combinations have potential for use in practical frying operation to improve the functional and healthy aspects of used frying oils.     

Active Treatment of Frying Oil for Enhanced Fry-life

Frying experiments were conducted simulating food service operation for 10 d, with and without active treatment of frying medium. Oil samples were analyzed for free fatty acids (FFA), color, food oil sensor (FOS) readings, chemiluminescence, and total polar compounds (TPC). Daily treatment of frying oil with adsorbent was found to extend the frying life of oil by reducing the accumulation of FFA, TPC, and AOCS ‘R’ color value by 72%, 30%, and 52%, respectively.     

Polar compounds: a quantitative indicator for life cycle assessment during protracted semi-continuous deep fat frying simulation

Total Polar Compound (TPC) analysis was used to evaluate fry life cycle of oils and shortenings with differing fatty acids compositions, and to understand if longer trisaturated material (Tribehenin), could influence total fry life, during protracted, semi-continuous deep frying simulations. Results showed, when TPC reached 25% max, the TOTOX and FFA revealed correlated values. However, both FFA and Totox were deemed unreliable indicators of oil quality. TPCs were more acutely accurate, especially during oil filtration and top-up procedures, where peak TPC onset showed stronger correlation for assessing oil degradation. Unsaturated frying oil, SBO (PUFA based), resulted with the shortest fry life of 132 fry-cycles; POL (MUFA based) 138 fry-cycles and MPS (MUFA based + Tribehenin) achieving up to 146 fry-cycles, suggesting Tribehenin may apparently extend fry life longevity.     

The recovery of used sunflower seed oil utilized in repeated deep-fat frying process

In this study, 50 consecutive deep-fat fryings were done by frying potato samples, each weighing 100 g, in sunflower seed oil at 170 °C. Significant chemical and physical changes in sunflower seed oil were observed during frying. A number of official methods were used to evaluate its adsorption abilities including free fatty acids (FFA), peroxide value (PV), conjugated dienes at 232 nm, secondary oxidation products at 270 nm and specific heat value determination. These parameters were determined in oil samples taken after each of the ten fryings before and after adsorbent treatment. A mixture of 2% pekmez earth, 3% bentonite, and 3% magnesium silicate was used as the adsorbent mixture. The FFA content of oil increased from 0.17 to 0.29% during frying. The use of adsorbents reduced FFA content of the used oil to 0.13%, i.e., a value below the FFA content of fresh oil (0.17%). Peroxide values decreased during frying because of decomposition of peroxides at high temperatures. A significant reduction was obtained in peroxide and conjugated diene values (K₂₃₂ value) due to the adsorbent treatment. However, the treatment increased the amount of secondary oxidation products (K₂₇₀ value). The specific heats of untreated used oil were higher than specific heats of adsorbent treated used oil over the entire frying process.     

COMPARISON OF THE FRYING PERFORMANCE OF REFINED, BLEACHED AND DEODORIZED PALM OLEIN AND COCONUT OIL

The frying performance of refined, bleached and deodorized palm olein (RBDPO) and refined, bleached and deodorized coconut oil (RBDCO) was compared in this study. The oils were studied during intermittent frying of potato chips at 180C for 5 h/day for 5 consecutive days. The indices used for assessment of frying performance of the oils were fatty acid composition (FAC), peroxide value (PV), anisidine value (AnV), % free fatty acid (FFA), iodine value (IV), % polar component, polymer content, color, viscosity, smoke point and foaming tendency. The results showed that RBDPO was superior to RBDCO in frying performance in terms of % FFA, iodine value, foaming tendency and smoke point. However, RBDCO performed better than RBDPO with respect to % polar component, polymer content, resistance to oxidation, color and viscosity. Flavor evaluation showed that potato chips fried in RBDPO were preferred by the panelists.     

Rapid assessment of the quality of deep frying oils used by street vendors with Fourier transform infrared spectroscopy

Deterioration of deep frying oils used by street vendors is one of the major food safety concerns. Fourier transform infrared (FTIR) spectroscopy coupled with partial least squares (PLS) regression was applied for rapid evaluation of the quality of deep frying oils collected from different street vendors (n = 109) using various frying processes in Shanghai. The levels of free fatty acids (FFA), total polar compounds (TPC), and viscosity of oils were determined with conventional methods and used as reference values for developing PLS models. The FFA (0.07–1.78 mg (KOH)/g) of all tested frying oils were below the maximum allowed value, while 5.5 % of oils had TPC (3.19–54.47 %) above the maximum allowed value (27 %) based upon the related chinese standards. FTIR coupled with PLS regression resulted in less satisfying results for FFA determination (predictability for soybean oils: R² = 0.709, SEP = 0.14, RPD = 1.83), but showed great promise for rapid determination of viscosity (model predictability: R² = 0.921–0.945, SEP = 0.68–0.71, RPD = 3.54–3.98) and TPC (predictability for soybean oils: R² = 0.790–0.931, SEP = 1.89–2.94, RPD = 2.16–3.55) of frying oils from different commercial settings. Developing separated PLS models for shortening and non-shortening oils improved predictability, particularly for the analysis of TPC.     

DEVELOPMENT OF DEEP FRYING EDIBLE VEGETABLE OILS

Refined soybean and rice-bran oils have been selected as base oils for preparation of frying oils. Hexane and acetone fractionation of nontraditional tree seed oils (NTOs) such as sal, mango, mahua and palm fats was carried out at 5–20C. Chemical and chromatographic parameteres were used to fractionate each oil (NTOs) in order to obtain olein-rich and stearin-rich fractions. The stearin fraction obtained at 10 and 15C from hexane and acetone were identical and hence mixed together. The stearin fraction obtained from all the four NTOs were incorporated at 10% level with the conventionally refined (market sample) and physically refined (laboratory sample) soybean and rice-bran oils in order to obtain frying oils. Heat stability parameters of the oils, namely free fatty acids (FFA%), peroxide value (PV), and iodine value (IV) were determined for base oils and frying oils after heating. Values for oil samples changed as follows: A (refined soybean oil and frying oils containing it) % FFA from 0.18 to 0.17–0.19, PV from 3.6 to 4.6–6.0 and IV from 125.3 to 109.2–115.8; B (refined rice-bran oil and frying oils containing it) from 0.21 to 0.19–0.23 for % FFA, 4.0 to 4.6–6.7 for PV and 99.4 to 87.6–92.8 for IV; C (physical refined soybean oil and frying oils containing it) from 0.36 to 0.33–0.36 for % FFA, 5.7 to 7.4–11.2 for PV and 126.9 to 108.9–113.2 for IV; and D (physical refined rice bran oil and frying oils containing it) from 0.79 to 0.75–0.79 for % FFA, 7.1 to 8.2–11.3 for PV and 101.4 to 88.6–93.7 for IV, respectively. However, when base oils were heated as such, their deterioration was much faster. Fatty acid composition, determined by gas chromatography, also supported the results obtained by chemical means. These frying oils showed improved heat stability compared to their base oils.     

基于主成分分析的西式快餐条件下煎炸油品质评价

为了研究西式快餐条件下煎炸油的品质并建立其评价体系,考察了5种常见煎炸油(大豆油、菜籽油、葵花籽油、棕榈油及稻米油)在模拟西式快餐条件170℃连续7 d煎炸薯条过程中11个品质相关的理化指标,通过主成分分析法综合评价了5种煎炸油在煎炸过程中的煎炸性能,并建立煎炸油品质评价模型。结果表明,5种煎炸油煎炸周期结束后酸价、极性组分、羰基价、茴香胺值、全氧化值和色泽均显著升高(P<0.05),维生素E总量和氧化稳定指数均显著降低(P<0.05)。相关性分析显示茴香胺值、全氧化值、羰基价两两之间均显著性正相关(r=0.877～0.997,P<0.05),色泽与酸价呈极显著正相关(r=0.822,P<0.01),碘值与氧化稳定指数呈极显著负相关(r=-0.846,P<0.01),与亚油酸/棕榈酸比值呈极显著正相关(r=0.833,P<0.01)。主成分分析提取出3个综合性评价指标,累计贡献率达84.115%,反映了原指标的大部分信息,并进一步建立煎炸油煎炸性能的综合评价得分模型F=0.405F₁+0.295F₂+0.1...     

介电常数在煎炸油极性组分快速检测中的应用

介电常数与煎炸油中极性组分含量有较好相关性,用于评价煎炸油品质,具有快速、便捷、安全等优点。本文分析了液体介电特性的测试原理和煎炸油介电特性机制,列出极性组分和介电常数的相关性拟合模型。以商业化应用广泛的FOS、FOM 310、Testo 270三类快速检测仪器为对象,对其内部构造、仪器操作和数据可靠性进行评价,结合餐饮业实践经验总结了影响其检测准确度的主要因素,包括煎炸油品种、校准体系、悬浮物、操作规范性。最后,提出此快速检测技术未来的两大发展方向:对信号处理参数的特异性优化和对数据处理技术或红外在线检测技术的引入结合。     

TESTO快速检测法在煎炸油质量监控过程中的应用

生产加工与餐饮企业为降低成本需要合理重复使用煎炸油,为保证煎炸食品的安全性,有必要建立快速有效的检测方法,以便于企业对煎炸油品质进行监控。选用目前生产加工及餐饮企业广泛使用的12种煎炸油为监控对象,包括大豆油、棕榈油、高油酸菜籽油等7种单品油和5种不同组成的调和油,煎炸处理薯条、鸡块和鱼排3种常见快餐食品,试验每12 h取样检测煎炸油中的总极性组分含量(TPC),对比研究柱层析法及TESTO 270快速检测法的结果相关性。试验结果表明,使用快速检测仪检测样品TPC,当TPC20%时,其结果与柱层析法具有显著相关性(Pearson系数为0.744~0.984,P0.01),但当TPC20%时,相关性减弱(Pearson系数为0.553~0.929,P0.01),R~2值为0.149 2~0.863 2。当TPC介于20%至27%之间时,TESTO 270快速检测法的结果有3.6%假阳性,TPC大于27%时,假阴性结果比率为10%。本研究为TESTO 270快速检测法在煎炸油质量监控中的应用提供了参考。     

High-Temperature Natural Antioxidant Improves Soy Oil for Frying

ABSTRACT:  The objectives of this study were to determine the frying stability of soybean oil (SBO) treated with a natural citric acid-based antioxidant, EPT-OILShield™ able to withstand high temperatures and to establish the oxidative stability of food fried in the treated oil. Soybean oil with 0.05% and 0.5% EPT-OILShield and an untreated control SBO were used for intermittent batch frying of tortilla chips at 180 °C for up to 65 h. Oil frying stability was measured by free fatty acids (FFA) and total polar compounds (TPC). Chips were aged for up to 4 mo at 25 °C and evaluated for rancid flavor by a 15-member, trained, experienced analytical sensory panel and for hexanal content as an indicator of oxidation. Oil with 0.05% EPT-OILShield had significantly less FFA and TPC than the control. The effect of EPT-OILShield was apparently retained in aged chips because hexanal levels were significantly lower in chips fried in oil with 0.05% EPT-OILShield than in chips fried in the control. Tortilla chips fried in the control were rancid after 2 mo at 25 °C at sampling times evaluated from 25 to 65 h; however, chips fried in oil with 0.05% EPT-OILShield and used for 65 h were described as only slightly rancid after 4 mo. Gamma tocopherol levels were significantly higher in the chips fried in the oil with 0.05% EPT-OILShield than in the control, helping to inhibit oxidation in the tortilla chips during storage.     

Quality changes in mixtures of hydrogenated and non‐hydrogenated oils during frying

BACKGROUND: There is a need for frying oils with reduced trans fatty acid content and increased oxidative stability. This study was conducted to measure and compare frying oil quality parameters, namely colour, viscosity, free fatty acid (FFA) content and dielectric property, and to investigate changes in properties of mixtures of fully hydrogenated and non‐hydrogenated canola oils during deep‐fat frying of chicken nuggets. Proportions of hydrogenated oil to non‐hydrogenated oil used in the study were 0, 20, 40, 60, 80 and 100%. Chicken nuggets were fried at 190 °C. The relationships among quality parameters, frying time and oil type were investigated. RESULTS: Frying time and oil type had significant effects on all properties. First‐order kinetic equations were used to represent changes in colour, viscosity and FFA content. The rates of change of viscosity and FFA content were higher in non‐hydrogenated oil, whereas the rates of change of colour were similar in the different oils. Increasing the level of hydrogenated oil in the mixture resulted in only slight changes in quality parameters. CONCLUSION: Quality parameters, namely colour, viscosity, FFA content and dielectric property, of frying oil are significantly affected by frying time and hydrogenation level. Frying oil quality and stability can be adjusted by mixing hydrogenated and non‐hydrogenated oils. Copyright © 2008 Society of Chemical Industry     

氧化甘三酯指标在煎炸油品质评价中的应用（网络首发、推荐阅读）

研究煎炸过程油脂各极性组分的变化规律,并从法定废弃点处极性物质组成及指标间相关性两个角度,评价各极性组分指标用于表征油脂煎炸废弃的可行性。煎炸过程,油脂劣变生成的总极性组分(TPC)随煎炸时间的延长而累积。在油脂法定废弃点处,当TPC为27%时,煎炸油脂含11.2%的氧化甘油三酯多聚物+氧化甘油三酯二聚物(oxTGO+oxTGD),与各国标准规定的TPC和ox TGO+oxTGD比例是接近的。当TPC为27%时,煎炸油脂的氧化甘油三酯单体(ox TGM)含量为3.5%,煎炸过程oxTGM含量变化呈上下波动而无明显规律。Pearson相关性分析表明,煎炸过程油脂oxTGM与TPC无显著相关(P>0.05),表明应用TPC评价煎炸油品质时,实际未能同时覆盖对oxTGM的有效控制。因此须用TPC和oxTGM两项指标方可评价油脂煎炸过程的劣变。考虑到oxTGM的潜在毒性最强,oxTGM值作为表征高温煎炸油脂氧化劣变的废弃指标有一定实际意义。     

煎炸油中极性化合物和3-MCPDE的形成及控制研究进展北大核心CSCD

食用油在长时间高温煎炸过程中,会发生氧化、聚合、水解等反应,产生不利于人体健康的安全危害因子如极性化合物(TPC)和3-氯丙醇酯(3-MCPDE)等。介绍了煎炸油中TPC与3-MCPDE的形成机制与危害,并重点介绍了煎炸过程中TPC和3-MCPDE形成的影响因素,及有效控制煎炸油中TPC与3-MCPDE形成的措施,旨在为揭示TPC和3-MCPDE形成机理、控制煎炸油中TPC和3-MCPDE的形成提供参考。     

COMPARISON OF THE FRYING STABILITY OF REGULAR AND LOW-LINOLENIC ACID SOYBEAN OILS

The frying stability of a regular soybean oil (RSO) was compared with a modified low linolenic-acid soybean oil (LLSO). The rate of free fatty acid (FFA) formation was similar for both oils during 72 h of frying. Despite a reduction in polyunsaturated fatty acids, however, the rate of formation of total polar compounds (TPC) in LLSO was greater than RSO. The higher production of TPCs in LLSO was explained, in part, by a lower level of tocopherols and a more rapid rate of degradation of the main isomers, γ- and δ tocopherols. This study points to the limitations of predicting frying stability based solely on fatty acid composition.     

QUALITY CHANGES OF REFINED-BLEACHED-DEODORIZED (RBD) PALM OLEIN, SOYBEAN OIL AND THEIR BLENDS DURING DEEP-FAT FRYING

The quality changes of refined, bleached and deodorized palm olein (RBDPO) and soybean oil (SBO) and their blends were investigated in this study. The oils were studied during intermittent frying of potato chips at 180PT5C for 5 h per day for 5 consecutive days. The indices used for assessment of changes in quality of the oils were fatty acid composition (FAC), peroxide value (PV), anisidine value (AnV), % free fatty acid (FFA), iodine value (IV), % polar component, polymer content, color, viscosity, smoke point and foaming tendency. The results showed that RBDPO was superior to SBO in frying performance in terms of resistance to oxidation, changes in IV, AnV, foaming tendency, % polar component and polymer content. However, SBO performed better than RBDPO with respect to color, viscosity, FAA content and smoke point. Sensory evaluation showed that potato chips fried in both RBDPO and SBO were equally acceptable by the panelists.     

Change in colour and rheological behaviour of sunflower seed oil during frying and after adsorbent treatment of used oil

Improvement in colour and viscosity of used sunflower seed oil was studied because the reuse of recovered oil could provide considerable savings to food processors. In this study, 50 consecutive deep-fat fryings were done by using potato samples in sunflower seed oil at 170 °C. Significant changes in sunflower seed oil were observed during frying. Change in viscosity and Hunter colour parameters were investigated. These parameters were determined on oil samples taken periodically during frying, and after adsorbent treatment. A predetermined optimum adsorbent mixture (2% pekmez earth, 3% bentonite and 3% magnesium silicate by weight) was applied for colour and viscosity recovery of used oil. Both the adsorbent-treated and untreated used oils showed Newtonian behaviour. Significant increase in oil viscosity was observed during frying. Frying caused a decrease in Hunter L value and an increase in a, b and TCD values of used oil samples. Adsorbents improved the Hunter L, a and b values significantly as well as TCD values, but not the viscosity of the used oil. All the Hunter parameters and TCD followed zero order reaction kinetics. Good agreement was observed between calculated and measured data (r=0.986–0.996).     

棕榈油和大豆油在油条煎炸过程中品质变化研究

以不同熔点棕榈油和棕榈油―大豆油混合油为原料,以大豆油作对照,通过比较油条外观、口感,筛选出适于煎炸油条的棕榈油,再进一步通过测定油条煎炸过程中油脂样品游离脂肪酸(FFA)、过氧化值(PV)、色泽、极性值(PC)、羰基价(COV)等指标,研究两种油在油条煎炸过程中品质变化情况。研究结果表明,熔点14℃棕榈液油和大豆油都适于煎炸油条,且棕榈液油在煎炸过程中具有比大豆油更好氧化稳定性,仅是其游离脂肪酸(FFA)和色泽上升速率快于大豆油。总的来说,两种油在满足煎炸油质量要求前提下,同等数量棕榈油可比大豆油煎炸更多油条。     

Regeneration of thermally polymerized frying oils with adsorbents

Two thermally polymerized palm oils used continuously for deep-fat frying of legume-based snacks for 30 and 36 h were treated with various adsorbents as such and in binary and quaternary blends, in an attempt to regenerate them. Activated charcoal powder (ACH), aluminum oxide (ALO), aluminum hydroxide (ALH), activated clay (ACL), celite (CE) and silica gel (SG), activated carbon (ACA), frypowder (FP), britesorb (BR) and magnesol (MA) were evaluated for their efficacy in regenerating the oils in terms of their effects on physicochemical parameters such as free fatty acids (FFA), total polar materials (TPM), p-anisidine value (p-AV), conjugated dienes, viscosity and colour. Binary and quaternary adsorbent treatments were better than single adsorbents in improving the overall quality of the oils studied. The efficacy of the best adsorbent blend was further evaluated in a highly polymerized cottonseed oil collected from a local eatery. Use of such adsorbents is recommended for small processing units in the unorganized sector, where such polymerized oil is generally discarded.     

鲮鱼油炸过程中棕榈油指标的变化与控制

本研究对鲮鱼油炸过程中棕榈油指标的变化进行了感官及理化分析,并采用"Dalsorb吸附剂+板框过滤"的方法,对油炸后的棕榈油进行处理。结果表明:随着油炸时间的延长,棕榈油色泽逐渐加深、流动性及透明度逐渐变差,并且有大量鱼渣出现;棕榈油的酸价、羰基价、极性组分随油炸时间的延长不断增大(酸价由初始0.06 mg KOH/g上升至2.34 mg KOH/g,羰基价由初始3.64meq/kg上升至17.70 meq/kg,极性组分由初始3.07%上升至15.1%),过氧化值的变化无明显规律;其中酸价、极性组分变化更接近国标上限,可优先做为评价指标,但考虑到极性组分检测时间长的原因,建议在线监控以酸价指标为主。采用"Dalsorb吸附剂+板框过滤"的方法,能够明显的降低煎炸后棕榈油的酸价指标(酸价由2.36 mg KOH/g下降至1.50 mg KOH/g),对羰基价和极性组分的处理效果不明显。