THERMAL and PHYSICAL PROPERTIES of TORTILLA CHIPS AS A FUNCTION of FRYING TIME

The objective of this study was to determine the thermal conductivity, specific heat, density (true and bulk), and the texture characteristics of tortilla chips and to study the effects of moisture content, oil content, and frying time on these properties. Tortilla chips were fried in fresh soybean oil for different times at 190C. Results showed that the values of thermal conductivity of tortilla chips decreased from 0.23 to 0.09 W/mC, specific heat from 3.36 to 2.31 kJ/kgC, and bulk density from 880 to 579 kg/m³ as frying time increased. In general, the crispness of tortilla chips increased as frying time increased.     

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.     

真空油炸胡萝卜脆片基本特性的研究

真空油炸技术可用于生产高品质的果蔬脆片．主要研究了油炸温度和真空度对胡萝卜片水分质量分数、脂肪质量分数、色泽及质构的影响．试验表明：随着油炸温度和真空度的升高，其干燥和脂肪吸收速度相应提高，且两者呈一定的相关性．统计分析可知：油炸温度和真空度并不显著性影响脆片的白度（L）、红度（a）、黄度（b）值（P〉0．05）；对于脆片的破碎力而言，真空度具有显著性影响（P〈O．05），而油炸温度不具有显著性影响（P〉0．05）．     

Deep‐fat frying of cassava: influence of raw material properties on chip quality

Thirteen cultivars of cassava (Manihot esculenta Crantz) were used to obtain chips by deep frying slices of fresh cassava flesh in palm oil. The cultivars were representative of three different levels of four major characteristics (water, cyanide, starch and amylose content) in parenchyma. The effects of raw material composition and crop age (10 and 12 months) on mass transfer (dehydration and oil uptake), texture and colour were assessed for 1.5 mm thick chips with a final water content of 0.04 kg kg⁻¹ wet basis, corresponding to a water activity of about 0.3. Frying time varied from 70 to 90 s and oil bath temperature from 140 to 160 °C. All cultivars gave a high frying yield (>0.5 kg chips kg⁻¹ fresh cassava) and a chip fat content of between 0.23 and 0.37 kg kg⁻¹ wet basis, with the highest frying yields and lowest fat contents being obtained from roots with the lowest water content and cyanide content. The intensity of darkening reactions increased in accordance with the level of reducing sugars, while the rigidity modulus of the chips was negatively correlated with the fibre content. The other characteristics (starch, amylose and total sugar content) were either not or poorly correlated with any of the chip quality parameters studied. Cyanoglucosides were only partially eliminated during frying (over 40% retention), so cultivars with a high cyanide content gave bitter chips. For a similar composition, drying rates and cooking rates were much lower when crop age increased. This could be attributed to a structural effect characterising crop age. © 2000 Society of Chemical Industry     

Total frying-use time effects on soybean-oil deterioration and on tortilla chip quality

Refined soybean oils were degraded at 190°C for 60h to a total polar material of 61.54%. The effect of fresh to highly degraded oil on the physical and thermal properties of the oil as well as on the Final quality of tortilla chips was determined. Surface tension decreased significantly with oil degradation (P < 0.05). Colour readings also changed significantly with oil degradation (P < 0.05) and were more pronounced after 30h of frying. Foam and off-flavour developed between 20 and 30h of degradation suggesting that the oil should have been discarded when the total polar material reached 27%. The convective heat transfer coefficient changed more rapidly after 30h of frying. The values of the convective heat transfer coefficient correlated highly with viscosity (−0.98). The oils, whether fresh or degraded, behaved as Newtonian fluids. Viscosity was significantly affected by oil degradation time and temperature (P < 0.05). The effect of temperature on the viscosity of the oils was described by an Arrhenius equation. Viscosity changed more rapidly with temperature as the degradation time increased. Tortilla chips were fried in fresh and degraded soybean oils. Total oil content and fracturability of tortilla chips were not affected significantly by oil degradation time (P < 0.05). However, the oil content adhering to the surface of the tortilla chips was significantly higher (P < 0.05) in the tortilla chips fried in degraded oil than in fresh oil.     

Comparison of vacuum and atmospheric deep-fat frying of wheat starch and gluten based snacks

Vacuum frying was compared with atmospheric frying in the development of wheat starch and gluten based snacks in terms of oil uptake, texture, expansion, and color development. The comparison was based on the concept of equivalent thermal driving force (ETDF) (i.e., keeping a constant difference between the oil temperature and boiling point of water at the working pressure). Vacuum fried snacks were observed to absorb lower oil content at all ETDFs and as low as 27% less of atmospherically fried samples and lighter in color. A very strong relationship existed between texture and oil content on one hand; and expansion and oil content on the other hand for fried matrices from both technologies. SEM was used in validating the result. Vacuum frying can be used for the development of acceptable fabricated fried snacks from wheat starch and gluten with lower oil content and acceptable textural and color properties.

     

茶多酚在油炸过程中对马铃薯片品质及其贮藏稳定性的影响

以感官品质、质构特性、理化特性、风味特性以及丙烯酰胺含量为指标,研究茶多酚在连续油炸过程中对马铃薯片品质的影响,并进一步探究茶多酚对马铃薯片贮藏稳定性的影响。结果表明,茶多酚对连续油炸过程中马铃薯片感官品质及硬度值的下降具有抑制作用;茶多酚对连续油炸过程中马铃薯片水分含量和含油率的增加具有明显的抑制作用,并且降低了薯片的含油率,茶多酚组T₂₄批次的马铃薯片含油率为41.96%±2.00%,显著低于空白组的46.29%±1.06%(P<0.05)。同时,与空白对照组相比,茶多酚抑制了马铃薯片劣变风味的产生,明显抑制了马铃薯片中有害物丙烯酰胺的生成。此外,茶多酚能够增加油炸马铃薯片的贮藏稳定性,平均货架期能够延长8 d。初步分析,茶多酚在油炸过程中对油脂品质的保护作用是其能够提高马铃薯片品质的重要原因。     

Effect of superheated steam prefrying treatment on the quality of potato chips

Superheated steam drying (SSD) was used as a prefrying treatment prior to deep‐fat frying for potato slices. The effect of SSD at 130, 150 or 180 °C and steam velocity of 2.0 m s^?1 on the fat uptake, colour and texture of fried potato chips was evaluated; microstructure and degree of starch gelatinization were also evaluated to help explain the fat uptake results. SSD and frying yielded potato chips with the fat content from 0.263 ± 0.002 to 0.304 ± 0.002 kg kg^?1 (d.b.), while frying without SSD led to chips with the fat content as high as 0.359 ± 0.003 kg kg^?1 (d.b.). SSD did not promote starch gelatinization. Lower fat uptake was correlated to modified surface structure and lower moisture content of potato slices prior to frying. Frying with/without SSD pretreatment yielded potato chips of similar hardness, crispness and lightness. On the other hand, SSD significantly increased redness and yellowness of the fried chips.     

Technological evaluation of new cultivars for potato chips manufacturing

Potato tubers of cvs. Condor, Diamont, Baraka, Mondial and Draga were used to produce chips of 1.0 mm slice thickness using an industrial slicer. Half of the slices quantity was immediately blanched in water at 100°C for approximately 5 min. Frying was carried out at 165–170°C in cotton seed oil. Both cvs. Diamont and Condor were the best varieties in the nutritional composition, since they contained the highest content of total solids (24.2 and 22.8%), crude protein (10.9 and 10.2%), total free amino acids (270 and 246 μmol/g DM), ascorbic acid (1.5 and 1.4 mg/100 g DM) and digested protein (49.8 and 49.6% for pepsin enzyme as well as 76.0 and 78.3% for trypsin enzyme). In contrast, they contained the lowest level of reducing sugars i.e. 0.8 and 0.9%, respectively. The same both varieties produced the maximum final yield of chips from both unblanched and blanched slices (50.0 and 47.4% as well as 48.9 and 45.8%, respectively) with the lowest final oil content i.e. <42%. Slightly differences in the final moisture content of chips were noticed. Blanching before frying led to a decrease in the final oil content of chips produced from all potato varieties. Sensory evaluation of the produced chips revealed that the favourable chips with the best quality attributes i.e. lighter and uniform in colour, lower final oil content, natural odour, more crisp and better in taste can be produced by using slices from cvs. Condor and Diamont. Furthermore, blanching before frying reduced significantly the oil content of chips and improved both colour and texture (more crispness) of the produced chips.     

Prediction of Mechanical Properties of Corn and Tortilla Chips by Using Computer Vision

Deep-fat frying is a unit operation which develops unique sensorial attributes in foods. For instance, texture is the principal quality parameter of tortilla and corn chips. On the other hand, computer vision is a useful tool for quality evaluation and prediction of some physical properties in different either raw or processed foods. The objective of this research was to characterize corn and tortilla chips by using computer vision, and to build proper mathematical models which permit to predict mechanical properties of these chips (maximum force, such as hardness, and distance to maximum force, such as toughness) by using chromatic features extracted from their corresponding digital images. Corn and tortilla chips (thickness of 2 mm; diameter of 37 mm) were made from masa of maize and fried at constant oil temperatures of 160, 175, and 190 °C. A high linear correlation (R ² > 0.9400) was obtained between mechanical properties and some image features (Hu, Fourier, and Haralick moments). Cross-validation technique demonstrated the repeatability and good performance (>90%) of the models tested, indicating that can be used to predict the textural properties of the tortilla and corn chips by using selected features extracted from their digital images, without the necessity of measuring them in a texture analyzer.     

Proximal composition and in vitro starch digestibility in flaxseed‐added corn tortilla

BACKGROUND: The effect of addition of flaxseed flour (10:90, 15:85 and 20:80, w/w) on the chemical composition and starch digestibility of corn tortilla was investigated. Tortillas were baked and frozen in liquid nitrogen, freeze‐dried, ground and analyzed for fat, protein, ash, total starch (TS), available starch (AS) and resistant starch (RS) contents as well as for starch hydrolysis rate and predicted glycemic index (pGI). Tortillas made from commercial nixtamalized corn flour were used as control sample. RESULTS: Flaxseed flour addition increased the fat and protein content of tortilla, whereas TS and AS decreased. TS was 15.25% lower in the 20% flaxseed‐containing tortilla as compared to the control sample. The AS content was 12.65% lower in the composite tortilla. RS content in the samples ranged between 1.92% for the control sample and 5.08% for the tortilla containing 20% flaxseed. The reduced enzymatic starch hydrolysis rate and pGI recorded for the flaxseed‐added tortilla, indicated slow digestion features. CONCLUSIONS: Flaxseed‐added tortilla might be used to increase the consumption of α‐linolenic acid in the daily diet and modulate starch digestibility of corn tortilla. This kind of product may be used by people with special diet reqirements. Copyright © 2008 Society of Chemical Industry     

Oil uptake and texture development in fried potato slices

The objective of this work was to study oil absorption and the kinetics of texture development of fried potato slices during frying. Prior to frying, potato slices were blanched in hot water at 85 °C for 3.5 min. Unblanched slices were used as the control. Control and blanched potato slices (Panda variety, diameter: 37 mm, width: 2.2 mm) were fried at 120, 150 and 180 °C until reaching moisture contents of 1.8% (total basis) and their texture and oil content were measured periodically. Oil uptake was higher in 15% for blanched samples than for control samples after 20 s of frying. Besides, the higher the frying temperature, the lower the oil absorption in control samples. Textural changes in fried potato slices were followed by the parameter maximum force (MF) extracted from the force vs. distance curves corresponding to different sampling times. Normalized maximum force (MF*) was used in modeling textural changes in the potato slices during frying in both the initial tissue softening process and the later crust development process. Higher temperatures accelerated these processes; however neither the temperature nor the pre-treatment had a significant effect (P > 0.05) over the final texture of the fried potato chips.     

Effects of processing conditions on the quality of vacuum‐fried carrot chips

The effects of pretreatment and vacuum frying conditions on the quality of fried carrot chips were studied. The moisture and oil contents of fried carrot chips were significantly (p < 0.05) reduced when blanched carrot slices were pretreated by immersion in fructose solution and freezing prior to vacuum frying. Furthermore, more uniform porosity was observed on the vertical cross‐section of carrot chips when examined by scanning electron microscopy. During vacuum frying, the moisture content, colour and breaking force of carrot chips decreased while the oil content increased with increasing frying temperature and time. However, there was no apparent change in Hunter ΔE with time when the frying temperature was below 100 °C and the frying time was below 25 min. Results of this study suggest that vacuum frying at moderate temperature (90–100 °C) for 20 min can produce carrot chips with lower moisture and oil contents as well as good colour and crispy texture. Copyright © 2005 Society of Chemical Industry     

Sensory and Quality Evaluation of Traditional Compared with Power Ultrasound Processed Corn (Zea Mays) Tortilla Chips

Power ultrasound reduces the traditional corn steeping time from 18 to 1.5 h during tortilla chips dough (masa) processing. This study sought to examine consumer (n = 99) acceptability and quality of tortilla chips made from the masa by traditional compared with ultrasonic methods. Overall appearance, flavor, and texture acceptability scores were evaluated using a 9‐point hedonic scale. The baked chips (process intermediate) before and after frying (finished product) were analyzed using a texture analyzer and machine vision. The texture values were determined using the 3‐point bend test using breaking force gradient (BFG), peak breaking force (PBF), and breaking distance (BD). The fracturing properties determined by the crisp fracture support rig using fracture force gradient (FFG), peak fracture force (PFF), and fracture distance (FD). The machine vision evaluated the total surface area, lightness (L), color difference (ΔE), Hue (°h), and Chroma (C*). The results were evaluated by analysis of variance and means were separated using Tukey's test. Machine vision values of L, °h, were higher (P < 0.05) and ΔE was lower (P < 0.05) for fried and L, °h were significantly (P < 0.05) higher for baked chips produced from ultra‐sonication as compare to traditional. Baked chips texture for ultra‐sonication was significantly higher (P < 0.05) on BFG, BPD, PFF, and FD. Fried tortilla chips texture were higher significantly (P < 0.05) in BFG and PFF for ultra‐sonication than traditional processing. However, the instrumental differences were not detected in sensory analysis, concluding possibility of power ultrasound as potential tortilla chips processing aid.     

香菇脆片真空油炸过程中传质规律

真空油炸过程中传质现象对真空油炸果蔬脆片的品质和安全控制极为重要。研究了油炸温度（80、90、100℃）、真空度（0.075、0.085、0.095 MPa）、预处理方式（漂烫,漂烫+浸渍+涂膜）对香菇脆片真空油炸过程中水分扩散和油脂吸收的影响,结果表明:香菇脆片的含水率随油炸时间的增加而逐渐降低,采用Pabis经验模型能较好模拟香菇脆片真空油炸过程中的水分变化;利用菲克定律建立模型,得到香菇真空油炸的水分有效扩散系数为2.47×10-9~7.70×10-9 m2/s,并且随着油炸温度和真空度的升高而增大;采用浸渍和涂膜处理降低了水分有效扩散系数。香菇片的油脂含量随着油炸时间的增加而逐渐升高,一段时间后达到稳定值;浸渍和涂膜处理降低了真空油炸香菇脆片的含油率。Pabis经验模型能够较好的模拟真空油炸香菇脆片的油脂含量变化,油炸温度和真空度对香菇脆片的平衡含油率（Y_max）影响不大,油脂吸收系数（K_Y）随着油炸温度和真空度的升高而增加。     

Mechanisms of oil uptake during deep frying and applications of predrying and hydrocolloids in reducing fat content of chips

Deep frying resulting in high-fat content is extensively used in the food industries and domestic households, and becoming an integral diet globally. The physical and chemical changes and oil uptake contributes to the unique taste and texture of fried food. Consumption of food high in fat is a health concern due to the increasing rate of obesity and cardiovascular diseases. Consumer awareness has led food industries to aim at fat reduction while maintaining the organoleptic properties of fried foods. This article reviews recent findings in reducing fat content emphasising on pretreatments. Modification of product surface was proven to lower fat content, reducing moisture content by 10% after predrying results in 54% fat reduction, while hydrocolloids coating in potato chips reduces fat content by 57% after deep frying. Although current technology, vacuum frying and air frying have a promising result in using less oil, but the initial cost is high.     

稻米油调和油煎炸应用研究

通过与棕榈油对比180℃下炸制薯片以及评估薯片感官喜好度、质构、口感及粘牙性等差异来评价稻米油调和油的煎炸应用性能。结果表明:采用稻米油调和油煎炸的薯片中多不饱和脂肪酸含量显著高于棕榈油(P<0.05),且其薯片的整体感官喜好度、质构口感、酥脆度、粘牙喜好度,均显著优于棕榈油薯片(P<0.05)。在加速氧化条件下,采用稻米油调和油炸制的薯片的酸价、过氧化值均与棕榈油炸制的薯片无显著性差异(P>0.05),且远低于GB 16565-2003的规定。在加速存储过程中,谷维素却得到了很好的保留。总之,稻米油调和油具有良好的煎炸性能。     

Effect of Microwave Frying on Acrylamide Generation,Mass Transfer,Color, and Texture in French Fries

The objective of this work was to evaluate the effect of microwave power on acrylamide generation, as well as moisture and oil fluxes and quality attributes of microwave-fried potatoes. Concretely, 25 g of potato strips, in 250 mL of fresh oil (at room temperature), were subjected to three different microwave powers (315, 430, and 600 W) in a conventional microwave oven. Microwave frying resulted in an acrylamide reduction ranged from 37 to 83% compared to deep-oil frying. Microwave-fried French fries presented lower moisture and higher fat content than deep-oil fried potatoes. Concretely, microwave-fried potatoes presented values of moisture and texture more similar to potato chips than French fries, nonetheless with lower fat levels (less than 20 g/100 g wb) and acrylamide content (lower than 100 μg/kg wb) at the reference time. This study presents an alternative way of frying to address the production of healthier potato chips.     

Mitigating effect of amaranth (Amarantus hypochondriacus) protein on acrylamide formation in foods

The effect of addition of amaranth flour and amaranth protein isolate to both a glucose/asparagine model system and real foods (cookies, fried tortilla chips, and baked tortilla chips) was studied to analyse the acrylamide mitigating potential of this underexploited plant with attractive nutraceutical properties. Addition of amaranth flour, with a relatively low protein content (16.45%), did not mitigate acrylamide in either the model system or the studied foods. On the contrary, addition of amaranth protein isolate decreased acrylamide content by 35–40% in the model system, 89% in cookies, 51% in fried tortilla chips, and 62% in baked tortilla chips. This acrylamide reduction was obtained without change in the colour or the texture of the cookies. On the contrary, colour remained unchanged in tortilla chips, but the addition of amaranth protein isolate increased the hardness (16–36%) of the produced tortillas. Although a much more detailed sensory evaluation of cookies and tortilla chips prepared using amaranth protein isolate is needed, the above results suggest that the use of amaranth protein may be an interesting way to both mitigate acrylamide formation and improve nutritional properties of foods.     

Functionality of batters containing different starch types for deep-fat frying of chicken nuggets

The effect of various starch types (amylomaize, corn, waxymaize, pregelatinized tapioca) on quality attributes (texture, moisture content, oil content, color, coating pick up, cooking yield, volume and porosity) of deep-fat fried chicken nuggets were studied. Chicken samples, 0.04 m in diameter and 0.015 m in thickness, taken from the breast portion, were coated with batters composed of a 3:5 solid to water ratio by immersion. The solid content of batter formulations contained equal amounts of corn and wheat flour, 5.0% starch, 1.0% salt and 0.5% leavening agent. As control, batter without starch addition, was used. Samples were fried at 180°C for 3, 6, 9 and 12 minutes. Crispness and oil content of chicken nuggets increased, whereas moisture content decreased with increasing frying time. Starch addition to the formulations increased crispness of the product significantly at the last stages of frying. The highest porosity and oil content was obtained when corn starch was used. Pregelatinized tapioca starch was found to provide a product with the lowest oil content, the highest moisture content, coating pick up and volume.