大豆油和棕榈油在高温煎炸过程中流变特性研究

以大豆油、棕榈油作为煎炸油,薯条、鸡块和鱼排作为煎炸材料,研究煎炸油黏度影响因素、高温煎炸过程中油样的流动性及黏温特性,分别采用Arrhenius、Lioumbas、Andrade-Arrhenius和Williams-Lander-Ferry模型对其黏温特性曲线进行拟合。结果表明:煎炸过程中,煎炸油整体呈牛顿流体(10~1 000 s-1);煎炸中大豆油黏度增加快于棕榈油,煎炸荤食的油黏度增加快于煎炸素食的油黏度,煎炸时间的延长均促进油黏度增加;煎炸油黏温变化速率随煎炸时间延长而加快,整体黏度趋于上升;比较4种模型发现Lioumbas模型拟合煎炸过程最佳。     

食用油在持续煎炸过程中品质的变化与评价

以大豆油为研究对象,探讨在(200±5)℃交替煎炸骨肉相连串和土豆片,持续煎炸48 h过程中油的感官指标和理化指标的变化,为餐饮业合理使用煎炸油提供依据。结果表明:色泽可以作为最直观反映煎炸油品质的指标;煎炸组油样的酸价不断上升,在42 h突破国家食用植物油卫生标准限值;过氧化值在煎炸过程中处于波动状态,但并未超过国家食用植物油卫生标准限值,不能单独作为判断煎炸油品质的指标;在煎炸过程中油样的砷含量随着时间的延长逐渐升高,在12 h达到最高并超过国家食用植物油卫生标准限值,但随着时间的延长转而逐渐下降,其可能与煎炸食物的来源、种类以及煎炸温度和时间有关。     

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。     

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。     

基于多项式拟合对煎炸油质量的预测

通过测定煎炸油理化指标确定煎炸油质量过程较为繁琐,因此寻找一种方法快速确定煎炸油质量情况十分必要。通过在160、175、190、205、220 ℃等五个温度下进行大豆油煎炸实验获得酸价、羰基价、极性组分等理化指标数据,进行多项式拟合建模。在初次拟合模型的基础上,对删除学生化残差绝对值 > 3或Cook距离 > 1的异常数据进行剔除,并用其余数据再次进行多项式拟合建模,使用模型预测其他未知时间点的理化指标值。酸价和极性组分均采用二次多项式拟合,羰基价采用三次多项式拟合,通过拟合结果,R2在0.8628以上。各温度分别取三个未知油样,测定它们的三个理化指标作为测量值,计算各模型获得的拟合方程作为拟合值进行验证实验,相关性达到0.9968以上。表明模型稳定,能够很好地对未知油样进行预测。     

不同存储时长的两批煎炸油理化指标数据可视化分析

本文针对存储时长为18个月和3个月的大豆油在煎炸过程中分别测出来的酸价、羰基价和极性组分数据进行了计算和相应可视化分析，以观察煎炸过程中的两批油同等实验条件下的理化指标在相应时间点上的变化关系，为煎炸油的安全监控提供依据。首先根据三个理化指标已经测得的数据进行了统计描述分析和箱线图可视化，其次对两个批次油的三个指标进行了曲线拟合可视化，最后进行了“时间-温度-指标值”的曲面和相应等高线可视化分析等。结果表明，箱线图可视化过程中，总体观察到存储时间长的油在同一个煎炸温度下的理化指标值的变化范围更大；曲线拟合可视化过程中，发现酸价变化最规律，可以用来根据一个批次油在煎炸过程中的酸价值去估计同等实验条件下另一个批次油的酸价值，从而也可以用来根据已知一个批次油的存储时长去估算另一批次油的存储时长；曲面可视化和等高线可视化过程中，发现190 ℃是温度的一个分界点，190 ℃以上的煎炸过程中，存储时间长的油的理化指标值增长的更快、氧化速度增加、油更加不稳定；同时，也发现20 h是时间的一个分界点，20 h后，存储时间长的油的理化指标值增长的更快。说明连续煎炸的情况下，温度尽量不要超过190 ℃，煎炸时长最好不要超过20 h。     

煎炸过程中油脂劣变的影响因素研究

分别对煎炸时间、煎炸方式、煎炸温度、煎炸食材及煎炸油种类对煎炸油极性组分含量和酸值的影响进行研究,分析控制煎炸过程中油脂劣变的有效措施。结果表明：煎炸油的极性组分含量、酸值随煎炸时间的延长而升高,且连续性煎炸优于间歇性煎炸;煎炸温度越高,油脂劣变速度越快,油脂的极性组分含量、酸值升高越快,为保证煎炸食品的卫生质量,延长煎炸油的使用寿命,控制煎炸温度低于200 ℃;不同煎炸食材对煎炸油品质劣变速度的影响大小依次为鱼饼>鸡腿排>薯条;不同煎炸油在煎炸过程中极性组分含量、酸值的变化均不同,多不饱和脂肪酸含量高的大豆油比稻米油、棕榈油更容易发生水解和氧化,稻米油的煎炸周期接近棕榈油。     

栀子果油煎炸过程中的品质变化及对油条和薯条的感官影响

为了探究栀子果油煎炸过程中的品质变化,本文选择薯条和油条两种代表性煎炸食材,将栀子果油在煎炸20h内每隔2h的酸价、羰基价、过氧化值和极性组分与大豆油、棕榈油在同等条件下煎炸的理化指标进行比较,结果表明：棕榈油煎炸后的品质较高,栀子果油和大豆油比较相似,栀子果油可以作为煎炸油。但栀子果油连续煎炸12 h时极性组分超过国家现有煎炸油的卫生标准,因此其连续煎炸时间不能超过12 h。同时对1、10、20h煎炸出来的油条和薯条进行感官评价,结果表明：煎炸食材相同时,三种食用油的感官评分无显著性差异（P>0.05）,说明栀子果油对油条和薯条的品质无不良影响,适合作为煎炸油。     

煎炸调和油的研究与开发

选用花生油、菜籽油、稻米油、玉米油、大豆油和棕榈油等油样,通过不同的复配比例制得4种试验用煎炸调和油:调和油2-3、调和油3-1、调和油4和调和油5。经过180℃煎炸油条之后,比较4种调和油的感官指标、酸价、过氧化值、苯并芘、反式脂肪酸以及脂肪酸组成变化,考察煎炸油品质。综合各项检测指标,调和油5劣变程度最小,色泽浅、烟点高、反式脂肪酸含量低、脂肪酸组成合理,煎炸稳定性强,煎炸寿命长,油炸食品感官效果好,可以作为一种新型煎炸调和油。     

TGP在煎炸油质量评价中的应用研究

现有煎炸油质量评价指标存在特征指标专一性不强、适用范围有限等缺陷。对煎炸油中极性组分与TGP相关性进行研究,结果表明,极性组分与TGP随煎炸时间的延长呈线性增加关系。通过试验得出多次使用的煎炸老油中TGP含量远高于新鲜煎炸油,用TGP含量评价煎炸油质量具有可行性。相较PCs指标,TGP的稳定性更能使其客观反应油脂的新鲜程度。     

Studies of the changes in edible fats during heating and frying

For detecting the changes in edible fats during the frying operation and for quality assessment of used frying fats 5 relatively simple methods were proposed: determination of polymer content by gel permeation chromatography, measurement of total polar artefacts by TLC followed by densitometry or by adsorption column chromatography, determination of decrease in essential fatty acid concentration and photometric measurement of absorbance at 232 nm. Using the above methods degradation of sunflower oil, rapeseed oil and lard was investigated by running 12 laboratory experiments with different heating or frying conditions. The results showed that both the composition of fat and the frying parameters greatly influence the rate of deterioration. Study of relationships between values obtained by different methods (using data from 110 samples) indicated that high, linear correlations depending on the nature of fat can be found. Correlation coefficients and equations of regression lines were calculated.     

Machine learning workflow for the oil uptake prediction of rice flour in a batter-coated fried system

Machine learning algorithms were applied to predict the oil uptake of rice flour in batter-coated fried foods, depending on its physicochemical features before frying (amylose content, pasting parameters, and batter viscosity). Low coefficients of Pearson correlation (0.29–0.61) were observed between the oil uptake of rice frying batters and other physicochemical parameters. Based on an exhaustive search method by the regsubsets function, the four experimental features (amylose content, peak time, peak temperature, and final viscosity) were selected as the best subset to affect the oil uptake of rice batters after frying, and then subjected to two machine learning algorithms – multivariable linear regression and multilayer perceptron neural network. Based on K-fold cross-validation, the experimental results were divided into 5 datasets consisting of each 80% training and 20% testing dataset. Compared to the multivariable linear regression (R² = 0.6204–0.7219), the iterative application of the multilayer perceptron model made a relatively higher prediction (R² = 0.7388–0.7781) of the oil uptake of rice flour frying batter. Thus, the multilayer perception model with a hidden layer outperformed the multivariable linear regression by showing higher R² and lower relative error.     

电子鼻快速检测煎炸油品质

利用PEN3型电子鼻系统分析了高温煎炸过程中大豆色拉油挥发性成分的动态变化规律。大豆色拉油于180℃油浴锅控温无料煎炸,每隔6h取样电子鼻检测分析。结果发现,随着煎炸时间的延长,油中芳香苯类、氨氧化物、氨类、烷烃、硫化氢、乙醇等挥发性成分均有一定升高,尤其是氨氧化物、氨类、烷烃、硫化氢、醇类是煎炸油气味变化及品质恶化的主要来源。利用主成分分析方法(PCA)及线性判别分析方法(LDA)对不同煎炸时间的大豆色拉油进行归类区分,发现LDA分析效果优于PCA。采用负荷加载(Loadings)分析可判别不同传感器对于第一、第二主成分的贡献率及相关性,S1、S2、S3、S5、S6、S7、S8、S9等可作为优选传感器应用于分析煎炸油品质变化。因此利用电子鼻系统快速分析辨别煎炸油新鲜程度及品质是可行的。     

气相色谱-质谱联用结合化学计量学分析棕榈油煎炸过程中化学成分的变化

为了探究棕榈油在煎炸过程中化学成分的变化与极性组分之间的相关性,采用气相色谱-质谱联用技术获取了不同煎炸时间煎炸油的化学成分信息,结合化学计量学软件进行数据筛选、主成分分析与聚类分析。结果表明：经过筛选后的数据,不同煎炸时间煎炸油在主成分得分图上区分明显;聚类分析可将煎炸不同时间的煎炸油分成三类,每类之间化学成分差异明显,其中过度煎炸组极性组分含量基本大于27%;初步鉴别出9种煎炸过程中产生的差异性化合物,这些化合物的含量变化均与极性组分含量呈明显的线性关系（R2＞0.95）。研究表明,煎炸油在煎炸过程中化学成分会发生变化,部分变化与极性组分含量呈线性相关,极性组分含量可以作为评判煎炸油劣变程度的有效依据。     

Application of Chromatographic Techniques in the Detection and Identification of Constituents Formed during Food Frying: A Review

Frying is one of the most popular food processing methods. However, many physicochemical reactions occur during frying, forming complex products in both the frying oil and the fried food. Chromatographic techniques have been successfully applied to characterize the products formed during food‐frying or during a simulated frying process. In this review, the specific products analyzed by gas chromatography (GC) and high‐performance liquid chromatography (HPLC) are elucidated in detail. The most studied components are polar compounds (such as volatile compounds, hydrolysis products, oxidized triacylglycerol [TAG] decomposition products, oxidized TAG monomers, sterol oxides, oxygenated TAG polymers, and acrylamide) and nonpolar compounds (such as cyclic fatty acid monomers and trans isomers), which are classified based on their polarity. However, the definite structures of TAG polymers and sterol oxides, and polymers analyzed by GC or HPLC‐based methods are only investigated in modeled reactions. Furthermore, some of the sample pretreatments and chromatographic methods are only used to analyze the known products. A number of earlier trace amounts of undetected products need to be investigated by more effective detection techniques. The development of multidimensional chromatographic techniques and elaborate mass spectrometry detectors makes composition analysis possible for the food‐frying process, which may effectively promote the development of quality monitoring and nutrition evaluation for the fried foods.     

一阶导数紫外光谱法快速监测煎炸油品质

为实现煎炸油的快速方便监测,对加热过程中植物油的一阶紫外导数光谱变化与传统理化指标的相关性进行了研究。结果表明,大豆油和调和油在煎炸到一定时间后,370 nm处一阶导数吸光度与煎炸时间呈线性相关,花生油煎炸到8 h时370 nm处的吸光度基本不变,在大于370 nm处有明显的吸收峰出现。结合传统的植物油质量评价指标,大豆油和调和油在呈线性相关的1 h后,其极性化合物均已超标;而花生油在煎炸8 h后过氧化值超标,极性化合物没有明显增加。同时对其他植物油进行了一阶导数光谱扫描,发现未使用的油在370 nm均无吸收。因此,可采用一阶紫外光谱进行煎炸油质量监测,其中370 nm处的吸光度可以作为一个生要指示。     

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