Criterion for Oil Uptake during Deep-fat Frying

The effect of added powdered cellulose and methyl cellulose on oil uptake during deep-fat frying of donuts and falafel balls was determined. A new criterion, U_R, expressing the oil uptake ratio between the weight of oil uptake and the weight of water removed was introduced. This criterion was valuable in assessing effectiveness of reducing oil uptake during deep-fat frying. Methocel was significantly more effective than powdered cellulose in reducing oil uptake.     

Gel-strength in Restructured Potato Products Affects Oil Uptake during Deep-fat frying

A controllable food system consisting of a restructured potato product was employed to study the effect of gel-strength on oil uptake. Water loss and oil uptake were affected markedly by gel-strength. Oil uptake decreased as gel-strength increased. The oil uptake ratio, U_R′ (weight ratio of the oil uptake to the water evaporated during frying) was utilized to assess the effectiveness of reducing oil absorption during frying. This criterion was useful for comparison of restructured potato products with different initial or final moisture contents.     

Development of Healthy Low-Fat Snacks: Understanding the Mechanisms of Quality Changes During Atmospheric and Vacuum Frying

Excess consumption of fat, a main component in fried food, is a key dietary contributor to coronary heart disease and perhaps some types of cancer. Although consumers are interested in healthier snacks, they are not willing to sacrifice organoleptic properties. Vacuum frying might be an alternative for the production of nutritious, healthy, palatable, and novel snacks. The objective of this review is to discuss the effect of atmospheric deep-fat frying on the main microstructural components and quality parameters of fried food, to understand how quality can be improved by lowering the operating pressure and, therefore, the processing temperature.     

Oil Uptake in Deep Fat Frying as Affected by Porosity

The porosity of a restructured potato product ranged from 0.089 to 0.168 after fluctuating subfreezing storage temperatures. A linear relation was found between oil uptake during frying and porosity prior to frying. Bulk and particle density, and porosity were monitored for up to 5 min during deep-fat frying. Particle density increased gradually, bulk density decreased and porosity increased noticeably. After an initial short period, oil uptake correlated linearly with porosity of the fried product. A new term, “net porosity” which excluded the void volume occupied by oil was developed for describing the oil uptake mechanism.     

Oil Absorption During Frying of Frozen Parfried Potatoes

A tracer method was used to assess the uptake of oil by commercial frozen parfried potatoes fried (180 °C, 150 s) in colza oil (CO) involving a short post-frying immersion in hot coconut fat (CF). CO and CF were determined directly in the crust by differential scanning calorimetry (crystallization temperature and enthalpy −42.7 °C/50 J/g and 10 °C/71 J/g, respectively). Oil uptake by the crust during frying in CO or CF was similar (average 25.3%). Potato samples transferred immediately after frying in CO to the CF bath had most of the CO absorbed replaced by CF after a 10 s post-frying, meaning that CO was readily accessible in the crust structure. Samples fried in CO and cooled for up to 60 s before transfer to hot CF showed only partial replacement of CO. Oil wetting the surface of the sample at the end of frying was estimated as 70 to 80% of the total oil uptake. Formation of the crust (frying time > 1 min) was required for oil to migrate into intercellular spaces that are dynamically formed during frying and thus accessible to CF and solvents.     

Structure Oil-Absorption Relationships During Deep-Fat Frying

ABSTRACT Analysis of the oil-absorption process in deep-fat fried potato cylinders (frying temperatures of 155°C, 170°C, and 185°C) allowed to distinguish 3 oil fractions: structural oil (absorbed during frying), penetrated surface oil (suctioned during cooling), and surface oil. Results showed that a small amount of oil penetrates during frying because most of the oil was picked up at the end of the process, suggesting that oil uptake and water removal are not synchronous phenomena. After cooling, oil was located either on the surface of the chip or suctioned into the porous crust microstructure, with an inverse relationship between them for increasing frying times.     

The Dielectric Property of Soybean Oil in Deep-Fat Frying and the Effect of Frequency

ABSTRACT: :
Suitability of the dielectric constant for real time and continuous evaluation of frying oil was investigated. Measurements of the dielectric capacitance, in the frequency range 1 kHz to 100 kHz, were made on soybean oil heated at several temperatures (180, 200, 220, and 240 °C) for a few d. Frequency dependence was also measured between 50 Hz and 30 MHz. The dielectric constant of the soybean oil increased with increase in the heating time, and was well correlated with acid value, density, and relative viscosity. Our equipment for measuring capacitance would be available for real time and continuous evaluation of frying oil quality in the food industry.     

油炸过程中淀粉功能特性的变化

采用深层油炸模型,研究了油炸过程中淀粉的溶解度、膨胀度、冻融稳定性和透光率等功能特性的变化。结果表明,在试验范围内,初炸100 s的淀粉溶解度最高,其次是初炸75 s的淀粉,复炸80 s的淀粉溶解度最低。随冻融循环次数的增加,不同油炸处理淀粉的析水率均增大,但不同处理的淀粉析水率增幅不同;初炸25 s的淀粉糊析水率始终高于其他油炸处理的淀粉。当初炸时间在25~75 s时,淀粉的透光率随初炸时间的延长,而逐渐增大;随复炸时间的增加,淀粉的透光率却逐渐下降。     

煎炸油在薯片煎炸过程中的品质变化

以煎炸油为研究对象,以薯片为煎炸原料,研究煎炸油煎炸过程中理化指标变化及各指标间的相关性。结果表明:在煎炸过程中,煎炸油的折光指数、色泽、酸值、羰基值和极性值均随时间的延长而增大;过氧化值随着煎炸时间延长先增大后逐渐减小;碘值随时间的延长而降低;比重、黏度、皂化值在煎炸过程中的变化无明显规律。酸值、羰基值、极性值、色泽和折光指数彼此之间有极显著的正相关性,且相关系数均大于0.9;煎炸油极性值的变化可通过色泽和酸值进行预测。     

Virgin Olive Oil as Frying Oil

Frying is one of the oldest cooking procedures and is still among the most popular ones for food preparation. Due to their unique sensory characteristics, fried foods are consumed often and with pleasure. During frying, part of the oil is absorbed by the food, thereby becoming part of our diet; most interestingly, in the Mediterranean area approximately 50% of total fat intake is provided by cooking fats. Olive oil is the key lipid component of the Mediterranean diet, the health‐promoting effects of which have been largely attributed to olive oil intake. Olive oil is unique among vegetable oils due to its desirable lipid profile and some of its minor components. Scientific evidence now indicates that during frying olive oil behavior is usually equal or superior to that of refined vegetable oils. Herein, an overview of virgin olive oil performance under frying is given, with special reference to the fate of olive oil microconstituents. The compositional changes of foods fried in olive oil are also reviewed and discussed in detail.     

地沟油检测方法的研究进展

近年来,食品安全问题越来越受到人们的重视,其中地沟油是目前最受关注的热点之一,已经形成了产业链,而食用地沟油会对人体造成极大的危害。目前,由于不法商贩加工地沟油手段的多样性以及检测方法的局限性,地沟油问题彻底解决仍然需要进一步研究。本文参阅近年来国内外有关地沟油研究文献,对地沟油中各指标的检测方法进行综述,并对不同方法进行归纳总结和分析。以期找到一种能够对油样进行多组分、多指标同步分析的检测方法,为地沟油的研究提供科学的参考。     

A Comparative Study of the Characteristics of French Fries Produced by Deep Fat Frying and Air Frying

Air frying is being projected as an alternative to deep fat frying for producing snacks such as French fries. In air frying, the raw potato sections are essentially heated in hot air containing fine oil droplets, which dehydrates the potato and attempts to impart the characteristics of traditionally produced French fries, but with a substantially lower level of fat absorbed in the product. The aim of this research is to compare: (1) the process dynamics of air frying with conventional deep fat frying under otherwise similar operating conditions, and (2) the products formed by the 2 processes in terms of color, texture, microstructure, calorimetric properties, and sensory characteristics. Although, air frying produced products with a substantially lower fat content but with similar moisture contents and color characteristics, it required much longer processing times, typically 21 min in relation to 9 min in the case of deep fat frying. The slower evolution of temperature also resulted in lower rates of moisture loss and color development reactions. Differential scanning calorimetry (DSC) studies revealed that the extent of starch gelatinization was also lower in the case of air fried product. In addition, the 2 types of frying also resulted in products having significantly different texture and sensory characteristics.     

A different perspective to study the effect of freeze, air, and osmotic drying on oil absorption during potato frying

ABSTRACT:  The objective of this article is to assess the effect of different dehydration pretreatments on oil absorption and illustrate how the different ways results can be reported may even drive to opposite conclusions. To do so, potato cylinders were blanched in hot water and dried until a moisture content of 62% (w.b.) by either freeze-drying, air drying, and osmotic drying with a sucrose solution or osmotic drying with a NaCl solution. Control (blanched) and dried potatoes were deep-fat fried at 170 °C for time periods between 1 and 5 min. Water removal and total oil uptake were determined and 2 oil fractions were distinguished: superficial oil and penetrated oil. Compared to the control, freeze dried samples increased oil uptake in 15.4% (d.b.) whereas air-dried samples reduced it in 11.2% (d.b.). Similarly, osmotic dehydrated samples showed a high reduction in oil uptake compared to the control (up to 27%[d.b.] when using a sucrose solution). However, this high decrease in oil absorption was attributed to the increase in solids content occurring during the osmotic dehydration process rather than a reduction in the amount of oil taken up. In fact, when the amount of oil absorbed per cylinder was determined, it was verified that oil uptake of osmotically dehydrated samples was even higher than the control, as opposed to what has been previously reported in the literature. These results highlight the importance of selecting an adequate basis to carry out comparisons properly.     

茶油深层煎炸稳定性的研究

以棕榈油作对照,采用精炼茶油进行深层煎炸。测定煎炸用以及薯条中的油脂在煎炸过程中的主要化学指标,即酸值、过氧化值、羰基价、碘价、皂化值、K值及极性化合物含量等的变化;分析煎炸用茶油的挥发性成分的变化;评价薯条的感官品质。试验结果表明:连续煎炸30h(120批次),茶油及棕榈油的酸值、过氧化值、羰基价、极性化合物含量和K值均逐渐升高,碘价和皂化值则逐渐降低;总挥发物含量逐渐增加,而一些小分子质量挥发物呈先升后降的趋势;用新鲜油煎炸的薯条的总体得分较高;除过氧化值外,薯条中茶油的其它测定指标的变化滞后于煎炸用油的变化。对照国标GB7102,24h时除茶油中的羰基价超标外,其它指标至30h时仍处于规定限值范围。茶油的深层煎炸寿命为24h(96批次)。用茶油煎炸的薯条易被消费者接受。     

Functional Characterization of Steam Jet-Cooked β-Glucan-Rich Barley Flour as an Oil Barrier in Frying Batters

ABSTRACT:  The effect of steam jet-cooking on the hydration, pasting, and rheological properties of barley flour was investigated. The thermo-mechanical shear during steam jet-cooking led to significant increases in the water absorption, water solubility, and swelling power of the barley flour. Also, the pasting profile showed elevated initial viscosity and reduced final viscosity. In addition, the suspensions of the steam jet-cooked barley flour demonstrated typical shear thinning and dynamic viscoelastic responses of random coil polysaccharides with entanglements. The steam jet-cooked barley flour was also evaluated as an oil barrier in fried foods. Its incorporation into frying batters increased batter pickup and viscosity while the moisture loss of fried batters was reduced. These combined effects significantly lowered the oil uptake of batters.     

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.     

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.     

五香油鸽的炸制工艺优化

为了优化五香油鸽的炸制工艺参数,本研究以新疆本地塔里木鸽为实验材料,将油炸时间、油炸温度、油焖时间为影响因素,以炸制后五香油鸽的出品率、油脂含量及感官评价为考察指标,在单因素试验基础上筛选出较适宜的油炸条件与油焖时间,进一步采用Box-Behnken试验设计构建多项式回归方程模型,通过响应面分析确定五香油鸽的最佳炸制工艺参数。研究表明油炸时间为28.68 s、油炸温度为153.24℃、油焖时间为35 min时模型预测出品率为73.93%、油脂含量为4.40%及感官评分为9.37,而实际出品率为74.28%、油脂含量为3.62%及感官评分为9.54,与预测结果的相对偏差仅为1.81%、2.84%及1.86%。此条件下,炸制出的五香油鸽口感与品质最佳,平衡了产品出品率与营养品质之间的关系。如何将五香油鸽的制作工艺更好地应用到鸽肉产品工业化生产中,是今后所研究解决的重点问题。     

可食性膜降低油炸鱼块含油量的研究

通过研究3 种可食性膜对降低油炸鱼块含油量的影响,探讨不同可食性膜、可食性膜在挂糊时的添加次序、可食性膜的质量分数以及不同比例的混合可食性膜复配后对油炸鱼块含油量的影响及其抑油效果。研究表明：3 种可食性膜与对照组相比均有显著的抑油效果(P ＜ 0.05),其中羧甲基纤维素钠(CMC-Na)效果最好,海藻酸钠次之,阿拉伯胶最小,其质量分数2% 的抑油率分别达到21.33%、16.97% 和9.99%;3 种可食性膜均在挂糊中添加的抑油效果最好;复配后按照CMC-Na:海藻酸钠=1:2 的比例配制的挂糊液抑油效果最好,其1% 质量分数的抑油率达到34.54%。