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.     

Stabilisation of sunflower oil and reduction of acrylamide formation of potato with rosemary extract during deep-fat frying

The aim of this study was to evaluate the effects of rosemary extract on the stabilisation of sunflower oil and the reduction of acrylamide formation in potato during deep-fat frying. The synthetic antioxidants butylated hydroxyanisole, tertiary butylhydroquinone, and tocopherols served as positive controls. Thermo-oxidative alterations were measured according to various physical and chemical parameters. Total polar compounds, free fatty acids, conjugated dienes, conjugated trienes, and colour (L*, b*) were evaluated for effectiveness of the antioxidants to stabilise the sunflower oil. The acrylamide concentration was evaluated for effectiveness of the antioxidants to reduce the acrylamide content in the deep-fried potato. Except for the decreased L* value (darkness of oil colour), these parameters all increased with the number of frying cycles. The order of effectiveness for inhibition of sunflower oil degradation and reduction of acrylamide formation in deep-fried potato was: rosemary extract > tocopherols > tertiary butylhydroquinone > butylated hydroxyanisole > control (P < 0.05). Total polar compounds, free fatty acid and acrylamide levels were significantly correlated with frying time (P < 0.05). The acrylamide formation in fried potatoes was significantly correlated with the formation of total polar compounds (P < 0.05) in the frying oil during the frying process.     

Improvement in the quality of used sunflower oil by organic and inorganic adsorbents

The objective of the present work was to improve the quality of used sunflower oil. Inorganic (normal and modified silica gel) and organic (normal and modified cellulose powder) adsorbents were used as regeneration agents. Sunflower oil was heated at 180 ± 5 °C, 4 h every day for five consecutive days. The adsorbent materials were individually added to use sunflower oil at 2% level (w/v). Some physico-chemical characteristics were measured to assess the quality of treated-used sunflower oil. The results indicated that all adsorbents under study were effective in improving the overall quality of used sunflower oil. Normal silica gel with small particle size permitted high adsorbing capacity and close to that induced with Magnesol XL which is used commercially in a large scale to improve oil quality. The polarity of the adsorbent substance had a remarkable effect on removing the secondary oxidation products of used sunflower oil. The mode of adsorbents action is discussed.     

高油酸葵花籽油煎炸过程中MCPD酯及缩水甘油酯的变化

以高油酸葵花籽油为煎炸用油对鱼排、鸡块和薯条进行煎炸实验,探究3-氯丙醇(3-MCPD)酯、2-氯丙醇(2-MCPD)酯和缩水甘油酯在煎炸过程中的变化。结果表明:原油中3-MCPD酯、2-MCPD酯及缩水甘油酯含量分别为0.26、0.05 mg/kg和0.58 mg/kg;在煎炸过程中2-MCPD酯含量与3-MCPD酯含量呈现极显著相关(p0.01);煎炸油中的MCPD酯在煎炸后有明显的生成;受煎炸材料的影响,3-MCPD酯含量在煎炸鱼排和鸡块体系煎炸12 h时达到最大值,分别为2.22 mg/kg和2.05 mg/kg,而后逐渐下降;3-MCPD酯含量在煎炸薯条体系中变化不大;缩水甘油酯含量则在所有体系中均下降,受煎炸材料的影响,缩水甘油酯分别在煎炸24 h(鱼排)、60 h(鸡块)和96 h(薯条)中基本降解完全。     

Optimisation of lipase-catalysed interesterification reaction for modulating rheological and heat transfer properties of frying oil

The present work reports the optimisation of enzyme interesterification reaction of rice bran oil (RBO) and refined, bleached, deodorized, palm olein (RBDPO) blend using immobilized 1,3-specific lipase, to improve the kinematic viscosity and heat transfer coefficient of oil, important for characterising heat transfer during the frying process. Four variables, namely RBO (20–80%) in RBO–RBDPO blend, reaction temperature (25–65 °C), enzyme concentration (1–13%, w/w) and reaction time (1–13 h) were selected and optimised using response surface methodology (RSM) coupled with central composite rotatable design (CCRD). The optimisation results predicted that optimum reaction conditions for preparing enzyme interesterified oil, having minimum kinematic viscosity (2.63 × 10⁻⁶ m² s⁻¹) and maximum heat transfer coefficient (262.0 Wm⁻² °C⁻¹) were at 62% RBO, temperature 65 °C, enzyme concentration 10% (w/w) and time 6.4 h. The predicted values were validated experimentally and corroborated with DSC melting profile and triacylglycerol molecular species data. This investigation could help snack food industries to develop suitable oils for frying operations.     

Effect of repeated frying on the viscosity, density and dynamic interfacial tension of palm and olive oil

The effect of deep-fat frying on the viscosity, density and dynamic interfacial tension (against air and water) of palm oil and olive oil was investigated. Repeated frying (up to 40 batches) at two different potato-to-oil ratios (1/7, 1/35 kg_potatoes/L_oil) was examined. Results were compared to those from simple heating the oils at the same temperatures. Viscosity increased during repeated frying for both oils. However, only palm oil viscosity was sensitive to potato-to-oil ratio. Due to the novelty of dynamic interfacial characterization of such systems a discussion was made about the appropriate timescales and deformation types for interfacial measurements. Significant effects of repeated frying on the dynamic interfacial tension at the oil/water interface were observed. Contrarily, changes in density were not significant. Results were assessed with respect to the evolving chemical profile of the oils determined in previous works. Possible implications of the determined properties on the frying process were discussed.     

Deterioration of sunflower seed oil under simulated frying conditions and during small-scale frying of potato chips

The changes occurring in sunflower seed oil under simulated frying conditions and during potato chip frying were monitored. The changes monitored were in: (a) fatty acid composition, (b) triglyceride content, (c) octanoate content, (d) titratable acidity, and (e) colour. To simulate frying conditions either argon or air, with or without steam, was bubbled through the hot oil. For the frying of potato chips, two methods of frying were used, viz continuous frying throughout 1 day and intermittent frying over a total of 10 days. It was found that whenever the hot oil was exposed to air, whether during simulated frying or the frying of potato chips, there was evidence of oxidative deterioration. Steam appeared to have an antioxidant effect in the simulated frying experiments. In all experiments the molar yield of acidity was comparable in magnitude with that of the octanoate. The correlation of octanoate production with the losses of linoleate and triglyceride is discussed.     

Suitability of contact angle measurement as an index of overall oil degradation and oil uptake during frying

The aim of the work was to investigate the suitability of contact angle measurement as an index of overall oil degradation phenomena and oil uptake of French fries during frying. In order to measure the contact angle, an image analysis method was developed and applied to four vegetable oils (palm oil, palm super olein, sunflower oil and a blend of hazelnut and high-oleic sunflower oil) in actual frying experiments. With liquid oils, contact angle modification proved to be a sound index of overall oil degradation, being inversely correlated with oil acidity, peroxide value, total carbonyl compounds, K₂₃₂, and viscosity. A significant correlation between contact angle and potato oil uptake was found for sunflower oil. For the other oils, factors such as the structure of food subjected to frying or the oil melting point and viscosity seem to be important in influencing oil uptake.     

脱色吸附剂对大豆脱色油返酸返色的影响

为对油脂精炼脱色加工提供参考,以活性白土、凹凸棒土以及二者复配作为脱色剂对大豆中和油进行脱色,测定脱色油的酸值、色泽,并通过返酸返色试验探究脱色吸附剂对大豆脱色油返酸返色的影响。结果表明：脱色油酸值与活性白土添加量和复配脱色剂中活性白土质量分数呈正相关,与凹凸棒土添加量呈负相关;脱色剂添加量越多,脱色效果越明显,但在活性白土或凹凸棒土添加量超过3%时,脱色效果增加较少;随活性白土或凹凸棒土添加量的增多,脱色油返酸总体呈先降后升趋势;脱色油会有不同程度的返色,与活性白土相比,凹凸棒土脱色返色程度更高。综上,在脱色过程中,通过调整脱色剂添加量和配比可在一定程度上控制成品油的返酸返色程度。     

Distribution and retention of phytosterols in frying oils and fried potatoes during repeated deep and pan frying

The retention and distribution of phytosterols in fried oils and French-fries during eight successive pan- and deep-frying sessions of pre-fried potatoes in sunflower oil, palm oil, cottonseed oil, virgin olive oil and a vegetable shortening were evaluated. Phytosterols (β-sitosterol, campesterol, stigmasterol, Δ⁵-avenasterol) were determined in the unsaponifiable fraction of frying oils and lipids extracted from French-fries by GC/FID after derivatization to trimethylsilyl ethers. French-fries were enriched with phytosterols due to the absorption of frying oil, with β-sitosterol predominating in both fried oils and potatoes. The amount of phytosterols decreased during frying, their overall retentions reaching 9.5–22.8% and 29.4–51.2% after eight successive pan- and deep-frying sessions, respectively, while their deterioration was found to be affected by frying time, frying technique, being more prolonged during pan-frying, and by the oils’ unsaturation, being more extended in polyunsaturated oils. Phytosterols were more or less uniformly distributed between the fried oil and the fried potatoes. The phytosterols dietary intake by consuming potatoes fried in the oils tested is discussed.     

HS-SPME-GC-MS分析冷榨和热榨葵花籽油的挥发性物质

采用顶空固相微萃取-气质联用法(HS-SPME-GC-MS)对冷榨葵花籽油和不同炒籽温度下的热榨葵花籽油的挥发性物质进行分析。结果表明:葵花籽油样品中共检测出59种挥发性物质,主要是萜烯类、醛酮类、烷烃类、杂环类及羧酸类物质;冷榨葵花籽油的挥发性物质主要是萜烯类、烷烃类及醛酮类物质,含量分别为38.96%、16.19%和12.20%;炒籽温度110、130、150℃下的热榨葵花籽油的主要挥发性物质的种类与冷榨葵花籽油的相似,但含量有很大区别,而170℃和190℃下的热榨葵花籽油的主要挥发性物质是吡嗪等杂环类物质和醛酮类物质。     

Simultaneous monitoring of the conventional qualitative indicators during frying of sunflower oil

Deterioration of sunflower oil during a 32 h frying was studied by monitoring the levels of polar compounds (total content, TPC; triglyceride polymers, TGP; triglyceride dimmers, TGD; oxidised triglyceride monomers, oxTGM; diglycerides, DG; and free fatty acids, FFA), carbonyl value (CV), oil/oxidative stability index (OSI), and conjugated diene value (CDV). The frying process increased the level of TPC in the oil from 2.8% to 28.9%. The TGP, TGD, oxTGM, DG, and FFA increased 186.5, 29.1, 6.1, 5.1, and 5.4 times, respectively. The CV, OSI, and CDV changed from 7.9 μmol/g, 2.7 h, and 10.6 mmol/l to 70.9 μmol/g, 1.2 h, and 61.6 mmol/l, respectively. The TPC or TGDP (TGD + TGP) contents were significantly correlated with the CV, OSI, or CDV. Finally, it was recommended that the sunflower oil should be discarded at 10% TGDP, 20% TPC, or 44 mmol/l CDV.     

Effect of fish (Catla catla) frying on the quality characteristics of sunflower oil

The quality of sunflower oil, as affected by fish (Catla catla) frying at 180 °C for 14 h was investigated. The purpose of the study was to find out the quality deterioration of sunflower oil with respect to time as affected by fish frying and to generate equations that can be used for predicting the quality parameters. The physico-chemical characteristics of sunflower oil were evaluated by drawing out the oil samples (75 ml) from the fryer at an interval of 2 h. The parameters evaluated were refractive index, colour, total polar material, free fatty acids, iodine value and peroxide value. There was a gradual increase in refractive index and colour with time of frying which was found to be significant (P < 0.05) in the latter. Iodine value decreased significantly (P < 0.05) with time of frying. Peroxide value first increased up to 12 h of frying and then decreased. After 10 h of frying, the total polar materials were 26.9%, indicating the need for replenishment or refinement of sunflower oil. Total polar material correlated well (r > 0.97) with colour, free fatty acids, peroxide value and time of frying. Free fatty acids correlated well (r > 0.96) with colour, total polar material and duration of frying. Fit of the equations was determined for total polar material and free fatty acids as a function of the respective correlated parameters.     

Some physical changes in Bajo Aragón extra virgin olive oil during the frying process

Changes of viscosity, transmittance spectra and colour of Bajo Aragón extra virgin olive oil, during the frying process, were studied, comparing them to the changes that occur during the frying process of high oleic sunflower oil. The studied oil was obtained from Empeltre variety olives. These changes, due to the deterioration of the oil during this process, were monitored by polar compounds measurement. Polar compounds content increased linearly with the frying cycle in both types of oil; however, the increase was faster in high oleic sunflower oil. The olive oil’s transmittance spectra, after the frying process, proved that, not only do the peaks corresponding to the carotenoids and the chlorophyll disappear but also that transformation of the chlorophyll occured. In high oleic sunflower oil spectra there were no changes. L* and b* colour parameters, measured on the CIELAB colour scale, showed the following behaviour: L* values increased for olive oil after frying while the opposite happened for high oleic sunflower oil. In the case of the b* parameter, the result was the same in both cases: when fried, more green and yellow colours appeared. The viscosity of both oils showed a non-linear increase with number of frying operations, which may correspond to a polynomial relationship. Despite their similar contents of oleic acid, olive oil was more stable to oxidation and there were some physical differences between the two types of oil.     

Use of sunflower oil mixed with jojoba and paraffin oils in deep-fat frying process

The aim of the present study was to increase the stability of sunflower oil during frying process and to obtain low-calorie fried foods. Therefore, sunflower oil was mixed separately with jojoba oil and paraffin oil at ratios of 9:1 and 8:2 (v/v). The frying process was conducted at 180 ° ± 5 °C for 12 h continuous heating time. Some physico-chemical properties (refractive index, viscosity, colour, acid value, peroxide value, thiobarbituric acid test, iodine value and polymer content) of non-fried and binary fried oil systems were measured at various heating periods. The results demonstrated that mixing sunflower oil with jojoba oil or paraffin oil increased the stability and hence improved the quality of sunflower oil during frying process.     

葵花籽油的超声波提取及抗氧化研究

研究了超声波强度、处理时间、溶剂用量、处理次数对葵 花籽油提取率的影响,得出最佳处理参数为:超声波强度 200kw/m2,处理15min,样品与溶剂比(g:mL)1:7,提取2 次,葵花籽油提取率较高。抗氧化研究采用SchaaI烘箱 法,即在葵花籽油中加入几种不同的抗氧化剂63±1℃条 件下进行加速氧化,结果表明,二丁基对甲苯酚、没食子 酸丙酯、特丁基对苯二酚对葵花籽油均有明显的抗氧化 作用,其中特丁基对苯二酚效果较好,柠檬酸对其具有协 同增效作用,添加50mg/kg柠檬酸抗氧化效果显著。     

煎炸对茶油品质指标及挥发组分的影响

目的：研究煎炸对茶油品质指标及挥发组分的影响，了解油脂的氧化情况；方法：通过顶空固相微萃取技术与GC／MS相结合，对煎炸加工导致的茶油理化指标和挥发组分的变化进行研究；结果：随着煎炸次数的增多，茶油的过氧化值及酸价均逐渐上升，同样K232值和K270值也随之变大，茶油挥发组分的总峰面积及出峰数也随着煎炸次数的增加而增大，大部分挥发物质的含量随着煎炸次数的增加而明显变大。可见煎炸强烈地影响着油脂的理化指标及挥发组分。     

葵花籽制油及综合利用

2003年世界葵花籽产量达到2 608.6万t,比1980年增加1.72倍.我国葵花籽产量比20年前增长2.2倍.葵花籽制油工业从无到有,在我国华北、西北和东北地区相继建成了30～300t/d规模的葵花籽制油加工厂,年加工葵花籽能力达500～800万t,葵花籽油年精炼能力达到20～30万t.葵花籽的制油工艺、设备水平接近国外20世纪80年代水平.葵花籽壳、仁、粕的综合利用处于起步状态.到2020年,我国葵花籽总产量可望增加到1 000万t,将为解决食用油产量不足的状况做出贡献.     

大豆油煎炸过程理化指标与煎炸时间相关性研究

针对食用植物油煎炸过程中理化指标是否可有效反映煎炸油品品质变化这一问题,以大豆油为煎炸油,薯条和鸡排为煎炸物质进行煎炸实验。随煎炸时间延长取不同程度煎炸油检测,研究酸值、羰基值、极性组分、p-茴香胺值、过氧化值和总氧化值等理化指标与煎炸时间相关性。结果表明:所研究理化指标中酸值、羰基值和极性组分3项指标与煎炸时间相关性较好,可有效反映油品变坏程度,p-茴香胺值、过氧化值和总氧化值相关性较差。