5种精制食用油在煎炸薯条过程中的品质变化

以大豆油、菜籽油、棕榈液油、棉籽油和煎炸调和油为研究对象,以薯条为煎炸原料,通过研究5种精制食用油在高温煎炸过程中理化指标的变化,从而反映出不同精制食用油在煎炸过程中品质的变化。结果表明:色泽可以作为一个最直观的指标反映食用油的煎炸程度;用酸值来评价煎炸油的品质具有滞后性和多变性;过氧化值的高低并不能完全反映油脂的煎炸程度,仅可作为判断食用油煎炸品质的参考指标;羰基值随着煎炸时间的延长整体呈线性正相关趋势,说明羰基值是一个判断煎炸油热劣变程度的灵敏指标;5种精制食用油一旦经过煎炸,氧化诱导时间迅速缩短,与油脂的煎炸程度没有很好的相关性,因此氧化诱导时间不能作为评价油脂煎炸品质的可靠指标;极性组分的含量是评价煎炸油热劣变程度的可靠手段之一。在煎炸过程中,棕榈液油的煎炸稳定性明显高于其他4种食用油。     

食用植物油煎炸过程中的品质变化北大核心CSCD

利用花生油、大豆油、调和油、棕榈油4种食用植物油作为煎炸油对豆腐、裹粉鸡柳、油条3种食材进行煎炸,研究煎炸时间对煎炸油极性组分含量及羰基值的影响,确定煎炸油时间预警点,同时研究了不同煎炸油品种、不同食材对煎炸油极性组分含量的影响。结果表明:极性组分含量、羰基值均与煎炸时间呈正相关(r_(极性组分)=0.809,r_(羰基值)=0.859,P=0.000);煎炸6~11 h煎炸油极性组分含量均值从初始的11.85%增至20.96%,最大值为34.10%,可作为煎炸油质量不达标的时间预警点;煎炸12 h,极性组分含量从低到高依次为花生油、棕榈油、调和油、大豆油,含量分别为21.1%、24.1%、26.8%、27.8%,豆腐、裹粉鸡柳、油条煎炸油中极性组分含量分别为17.7%、25.0%、32.2%;煎炸18 h,极性组分含量增大程度由低到高为棕榈油/调和油、大豆油、花生油,煎炸食材用油为豆腐煎炸油、裹粉鸡柳煎炸油、油条煎炸油。     

Physical and thermal properties of potato chips during vacuum frying

Vacuum frying (1.33 kPa), with the aid of a de-oiling mechanism, was used to produce low-fat potato chips.The kinetics of oil absorption and oil distribution in the potato chips was studied so that effectiveness of the de-oiling system could be established. Non-linear regression was used to fit the experimental data to the models used to describe oil absorption in potato chips with time.Moisture content, oil content, microstructure, diameter and thickness expansion, bulk density, true density, and porosity of chips fried at different temperatures (120, 130, and 140 °C) was performed to evaluate the effect of process temperature on the product. The convective heat transfer coefficient at the oil-chip interface was determined for the same temperature range.The final oil content of the potato chips was 0.072 ± 0.004, 0.062 ± 0.003, and 0.059 ± 0.003 g/g solid for frying temperatures of 120, 130, and 140 °C, respectively. These values are lower (80-87% less) than those found in the not de-oiled potato chips, which indicates that the de-oiling mechanism is crucial in vacuum frying processing. A significant difference (P < 0.05) was observed in oil content and oil distribution within temperatures. The rate of change in product quality attributes was greatly affected by temperature; however, the final values of moisture content, bulk density, true density, porosity, diameter shrinkage, and thickness expansion were not affected by temperature.During vacuum frying, the convective heat transfer coefficient changed considerably as frying progressed; moreover, it increased with temperature reaching a maximum between 2200 and 2650 W/m² K depending on frying temperature.     

Physicochemical properties and oxidative stability of frying oils during repeated frying of potato chips

Physicochemical properties and oxidative stability of refined coconut oil (RCO), refined soybean oil (SBO), pure olive oil (POO), and vegetable shortening (VST) during repeated frying of potato chips were determined. Polyunsaturated fatty acids of all the oils significantly decreased after frying. Tocopherols in SBO, POO and VST, and DPPH radical scavenging activities of POO and VST significantly decreased after frying. L* values of the oils significantly decreased, and a* and b* values significantly increased after 80 times repeated frying. Conjugated dienes and p-anisidine value of SBO after 80 times repeated frying were 21.8 mmol/L and 47.7, respectively, the highest among the oils. Levels of total polar compounds of all the oils after 80 times repeated frying were between 8.1 and 9.5%, not exceeding rejection limit after frying. Compositions and contents of alkanals, 2-alkenals, and 2,4-alkadienals in the oils during frying were largely affected by their fatty acid compositions.     

食用植物油煎炸过程中的品质变化

为降低小酥肉油脂含量,本实验在小酥肉糊料基础配方中添入葛根粉,以感官评分、含水率、含油率、色差为指标,对油炸后小酥肉的品质进行单因素实验,结合响应面-主成分分析法优化小酥肉糊料配方。结果表明,以糊料总重为基准,小麦粉添加量20%、葛根粉添加量4%、泡打粉添加量0.6%、水分添加量为59%时,感官评分为88,肉芯含水率为62.24%,含油率为4.38%,整体含水率为50.16%,含油率为14.22%,较未加葛根粉含水率提高了80.62%,含油率降低了61.46%,规范化综合得分为1.60,与预测的数值基本一致。该糊料配方对开发高营养、低脂油炸挂糊类产品有指导意义。

     

Changes in oil and potato chips during frying

The effect of frying of potato chips (batch processing during 12 h) on the chemical characteristics and fatty acid composition of the used oil were determined. Samples of the fried oil and potato chips were taken at various time periods. The volatile carbonyl compounds of the aroma concentrate of each sample were isolated and their oxime derevatives were prepared and subsequently estimated by UV absorption for the total oximes and conjugated diene carbonyl oximes. The development of the volatile carbonyl compounds in both frying oil and fried potato chips was increased on continued frying. Concerning the frying oil this increase was found to be in coincident with the decrease in the linoleic and linolenic acid percent.     

Porous media based model for deep-fat vacuum frying potato chips

Vacuum frying is an alternative method to the traditional atmospheric deep-fat frying that offers the health benefits associated with lower concentrations of acrylamide and less adverse effects on oil quality while still preserving the natural color and flavor of the product.     

The possibility of lowering oil content of potato chips by combining atmospheric frying with postfrying vacuum application

Four protocols involving the application of low pressures, either toward the end of frying or after frying, were investigated with the aim of lowering the oil content of potato chips. Protocol 1 involving frying at atmospheric pressure followed by a 3 min draining time constituted the control. Protocol 2 involved lowering of pressure to 13.33 kPa, 40 s before the end of frying, followed by draining for 3 min at the same pressure. Protocol 3 was the same as protocol 2, except that the pressure was lowered 3 s before the end of frying. Protocol 4 involved lowering the pressure to 13.33 kPa after the product was lifted from the oil and holding it at this value over the draining time of 3 min. Protocol 4 gave a product having the lowest oil content (37.12 g oil/100 g defatted dry matter), while protocol 2 gave the product with highest oil content (71.10 g oil/100 g defatted dry matter), followed by those obtained using protocols 1 and 3 (68.48 g oil/100 g defatted dry matter and 52.50 g oil/100 g defatted dry matter, respectively). Protocol 4 was further evaluated to study the effects of draining times and vacuum applied, and compared with the control. It was noted that over the modest range of pressures investigated, there was no significant effect of the vacuum applied on the oil content of the product. This study demonstrates that the oil content of potato chips can be lowered significantly by combining atmospheric frying with draining under vacuum.     

食用油在煎炸过程中的化学变化

煎炸技术是一种古老的食物烹饪方式,其以油脂为传热介质使食物从外到内加热至成熟。但是,煎炸过程的高温、多水和富氧环境会使食用油发生氧化、水解,以及聚合或裂解等多种化学反应。1氧化反应油脂变质是导致食用油产生毒害性的关键因素,而脂类氧化是油脂变质的主要原因之一。     

Comparative study of physical and sensory properties of pre-treated potato slices during vacuum and atmospheric frying

The objective of this research was to study the effect of different processing conditions on physical and sensory properties of potato chips. Potato slices of Desirée and Panda varieties (diameter: 30 mm; thickness: 3 mm) were pre-treated in the following ways: (i) control or unblanched slices without pre-drying; (ii) blanched slices in hot water at 85 °C for 3.5 min and air-dried at 60 °C until a final moisture content of ∼0.6 kg water/kg dry solid; (iii) control slices soaked in a 3.5 kg/m³ sodium metabisulphite solution at 20 °C for 3 min and pH adjusted to 3. Pre-treated slices were fried at 120 and 140 °C under vacuum conditions (5.37 kPa, absolute pressure) and under atmospheric pressure until they reached a final moisture content of ∼1.8 kg water/100 kg (wet basis). An experimental design (3 × 2³) was used to analyze the effect of pre-treatment, potato variety, type of frying and frying temperature over the following responses: oil content, instrumental color and texture and sensory evaluation. Vacuum frying increased significantly (p < 0.05) oil content and decreased instrumental color and textural parameters. Sensory attributes, flavor quality and overall quality, were significantly improved using vacuum frying. The higher frying temperature (140 °C) increased ΔE, maximum breaking force, hardness and crispness and decreased L^* and b^* values. On the other hand, Panda potato variety improved the color of the product. A great improvement on color parameters was obtained using sulphited potato slices instead of the other pre-treatments. Although, the better flavor was obtained for control potato chips, no significant differences were found for overall quality between control and sulphited potato chips. Significant correlations (p < 0.01) between sensory and instrumental responses were found.     

Antioxidant efficiency of oregano during frying and storage of potato chips

The effect of oregano on the oxidative stability of cottonseed oil during frying of potato chips and on the storage stability of the produced chips was studied. The ground spice or an ethanol‐derived extract thereof was added to the oil at a concentration of 2 g l^?1 (dry basis) before frying. The results showed that both ground oregano and its ethanol‐derived extract decreased the rates of accumulation of conjugated dienes, polar compounds, polymerised triglycerides, dimeric triglycerides as well as p‐anisidine value (p‐AV) of the frying oil. The major decrease was observed in the accumulation of polymerised and dimeric triglycerides. The accumulation of oxidised triglycerides showed a low decrease with the addition of oregano, while the hydrolytic compounds formed during frying were not affected. No significant difference (at 95% significance level) between ground oregano and its ethanol‐derived extract was observed. The storage stability of potato chips removed from the fryer at various time intervals was estimated by the rates of increase in peroxide value and conjugated dienes of the oil absorbed in the chips. Both rates were depressed when oregano was added to the frying oil; the protective action of oregano extract was considerably greater (at 95% significance level) than that of ground oregano. Copyright © 2003 Society of Chemical Industry     

Quality and safety driven optimal operation of deep-fat frying of potato chips

Increasing oil temperature and heating duration in deep-fat frying of potato chips can improve textural quality but worsen the chemical safety of acrylamide formation. Optimal design of this complex process is formulated as a non-linear constrained optimization problem where the objective is to compute the oil temperature profile that guarantees the desired final moisture content while minimizing final acrylamide content subject to operating constraints and the process dynamics. The process dynamics uses a multicomponent and multiphase transport model in the potato as a porous medium taken from literature. Results show that five different heating zones offer a good compromise between process duration (shorter the better) and safety in terms of lower acrylamide formation. A short, high temperature zone at the beginning with a progressive decrease in zone temperatures was found to be the optimal design. The multi-zone optimal operating conditions show significant advantages over nominal constant temperature processes, opening new avenues for optimization.     

Structural changes and shrinkage of potato during frying

Summary Light microscopy was used to study changes in cell size, blister formation and crust evolution during potato frying. Frying experiments with both French fries and crisps of different thickness (1–5 mm) were performed at temperatures of 140 and 180 °C. Thickness, volume and density changes were also measured. The formation of crust in French fries starts after the potato surface reached approximately 103 °C, and then the crust thickness increased linearly with the square root of frying time, this increase being faster at 180 °C. The potato volume decreased during frying, although in the late stages the volume may increase because of oil uptake and cell separation caused by entrapped water vapour. Shrinkage was adequately described by the Weibull model with a residual value, with shrinkage rate increasing with temperature and decreasing with potato thickness. The residual volume was not affected by temperature (65% for French fries and 59–30 for crisps, depending on thickness). Volume appeared to decrease mainly as the result of water loss, except for very low water content, and thus potato density changes were very small.     

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.     

Effects of frying parameters on physical changes of tapioca chips during deep-fat frying

The interrelationships of the effects of frying time, oil temperature, and initial moisture content on moisture loss, oil absorption, and linear expansion of a tapioca starch chip half-product during deep-fat frying have been studied. Both oil absorption and linear expansion were affected, in different ways, by moisture loss. Oil absorption was essentially a quantitative water replacement process. On the other hand, linear expansion occurred as a result of rapid vaporization of water in the initial stages of frying, but reached a plateau before maximum moisture loss. Critical frying times, temperatures, and initial moisture contents, below which virtually no physical change occurred, were observed. The optimum set of frying parameters for maximum linear expansion appears to be a frying time of 40 s, an oil temperature of 200°C, and an initial moisture content of 15% (dry basis).     

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     

Quality changes in trans and trans free fats/oils and products during frying

The physico-chemical changes occurring during simulated frying conditions at 180 °C for 24 h in trans free speciality fat, trans rich vanaspati and PUFA rich sunflower oil were evaluated. The samples became darker, the polar components and viscosity increased as the time of heating increased. The oxidative stability as determined by peroxide, anisidine values and TOTOX number, increased, whereas the total unsaturated fatty acids and iodine value decreased with time of heating in all the samples. The trans free speciality fat was as stable as vanaspati showing similar quality parameters, while sunflower oil showed a higher degree of deterioration. The layered fat used for traditional products such as Chiroti dough consisted 14% trans fatty acids (TFA), which was reduced to 4–7%, and correspondingly 18:2 was increased in the product upon frying in sunflower oil. Accordingly, trans fatty acids increased in the medium from 0 to 7.5%. Chiroti when fried in vanaspati with TFA 18%, their content in both products (16%) and in medium (17%) remained similar.     

Microstructural approach to understand oil absorption during vacuum and atmospheric frying

Crust microstructure plays a critical role in oil uptake of atmospheric fried food and seems to play an important role in vacuum fried products. The objective of this study was to understand the relationship between key microstructural parameters and oil absorption, after atmospheric and vacuum frying of different vegetable tissues. The effect of drainage and centrifugation in oil-uptake reduction was also analyzed. Key microstructural parameters were determined using gas adsorption at cryogenic temperatures, while oil location and surface roughness were studied using confocal laser scanning microscopy and area-scale fractal analysis, respectively. Overall, we found a linear relationship between porosity and final oil content in vacuum and atmospheric fried chips. However, this relationship could not be extended when analyzing the whole set of data, since oil absorption was significantly higher in atmospheric fried chips. Centrifugation allowed reducing oil-uptake up to 73% in atmospheric fried chips and up to 64% in vacuum fried ones.     

Effect of pore characteristics on oil absorption behavior during frying of potato chips

Developing an adequate understanding of oil absorption helps in producing healthier fried foods, however mechanism of oil absorption is required to be clarified. In this study, influence of porous structure on oil penetration and distribution of potato chips during frying was investigated. The results showed that pores with diameters 10–100 μm owned 49.37%–67.36% of total pore volume and its proportion increased during frying. Oil content increased to 61.20% at the frying time of 160 s, and oil gradually permeated samples during frying. Additionally, the pores with diameters of 10–100 μm and 100–200 μm possessed the positively correlation with oil content (p < 0.01). While pores with diameters of 0.3–10 μm was negatively correlated with oil content (p < 0.05). Bulk density decreased, while porosity, pore volume, and pore size increased during frying. This study provided a new insight into illustrate oil absorption of fried foods.     

基于同步荧光光谱法对食用油和煎炸油鉴别研究

快速鉴别食用油和煎炸油,选用市售大豆油、花生油、调和油以及不同煎炸条件下煎炸后的大豆油、花生油和调和油作为试验样品,采用Gray Eclipse荧光光度计对样品进行扫描处理,运用SPSS 16.0软件和Origin 8.0软件对样品的同步荧光光谱数据进行分析。结果表明,食用油煎炸后,荧光峰位置发生红移;与原油相比,煎炸后的大豆油与调和油的荧光峰强度降低,花生油的荧光强度在300~400之间波动;同一煎炸温度下,随煎炸时长的增加,煎炸油的荧光峰向波长增加的方向移动;同一煎炸时长下,随煎炸温度的增加,与原油相比,煎炸油发生红移的距离增大。判别分析对食用油和煎炸油的正确判别率为100%。可见利用同步荧光光谱法结合化学计量学方法可以有效区分食用油和不同煎炸条件下的煎炸油。