Acrylamide reduction in potato chips by using commercial asparaginase in combination with conventional blanching

In this research acrylamide reduction in potato chips was investigated in relation to blanching and asparaginase immersion treatments before final frying. Potatoes slices (Verdi variety, diameter: 40 mm, thickness: 2.0 mm) were fried at 170 °C for 5 min (final moisture content of ∼2.0 g/100 g). Prior to frying, potato slices were treated in one of the following ways: (i) Rinsing in distilled water (control I); (ii) Rinsing in distilled water plus blanching in hot water at 85 °C for 3.5 min; (iii) Rinsing in distilled water plus immersion in an asparaginase solution (10000 ASNU/L) at 50 °C for 20 min; (iv) Rinsing in distilled water plus blanching in hot water at 85 °C for 3.5 min plus immersion in an asparaginase solution (10000 ASNU/L) at 50 °C for 20 min; (v) Rinsing in distilled water plus blanching in hot water at 85 °C for 3.5 min plus immersion in distilled water at 50 °C for 20 min (control II). Blanching in hot water (ii) was almost as effective as asparaginase potato immersion (iii) in order to diminish acrylamide formation in potato chips (acrylamide reduction was ∼17% of the initial acrylamide concentration). When potato slices were blanched before asparaginase immersion, the acrylamide content of the resultant potato chips was reduced considerably by almost 90%. We have demonstrated that blanching of potato slices plus asparaginase treatment is an effective combination for acrylamide mitigation during frying. It seems to be that blanching provokes changes in the microstructure of potato tissue leading to an easier and more effective diffusion of asparaginase.     

Development of a computer vision system to measure the color of potato chips

The objective of this research was to design and implement an inexpensive computer vision system for measuring the color of a highly heterogeneous food material not only in shape as well in color such as potato chips in L^*a^*b^* units from RGB images. The system was composed of (i) a digital color camera for acquiring the images in a digital format, (ii) a computer for storage the images, (c) image analysis routines integrated into a software programmed in Matlab that converts the color RGB of the food image into L^*a^*b^* units. In this way the color of potato chips can be calculated in L^*a^*b^* units over representative areas and in a reproducible way. The kinetics of color changes in potato slices during frying at four temperatures was followed using the implemented computer vision system (CVS). Color values in L^*a^*b^* units were recorded at different sampling times during frying at the four oil temperatures using the total color change parameter (ΔE). Chips fried at higher temperatures get darker as expected and showed by the CVS. The implemented computer vision system can be used to study as well foods different from potato chips by selecting their proper settings for image acquisition and digital image processing.     

预处理对云南脆皮薯条中丙烯酰胺形成的抑制效果研究

目的探究预处理对云南脆皮薯条中丙烯酰胺形成的抑制效果。方法通过选取油炸温度、油炸时间和淀粉水溶液浓度的3个梯度设计单因素实验,对其品质变化进行测定以及感官综合评分法评定,建立云南脆皮薯条的最佳加工工艺。为有效控制丙烯酰胺,在热加工前,将马铃薯分别进行热烫(85℃下热烫10 min)、半胱氨酸浸泡(常温下于3 g/L的半胱氨酸溶液中浸泡10 min)、热烫+半胱氨酸浸泡(在85℃下浸泡于3g/L半胱氨酸溶液中10min)预处理,以未处理为对照组。热加工后,分别对云南脆皮薯条样品的风味品质指标:水分含量、水分活度、质量、颜色、还原糖含量、天冬酰胺、半胱氨酸等进行测定,分析不同预处理方式对云南脆皮薯条风味品质的影响,并对丙烯酰胺含量进行测定,比较3种预处理方式对云南脆皮薯条中丙烯酰胺的抑制情况。结果用热烫+半胱氨酸浸泡的预处理方式处理马铃薯后制作云南脆皮薯条,水分含量、颜色、还原糖、天冬酰胺与未处理组相比没有统计学差异(P0.05);半胱氨酸含量与其他预处理组对比显著增加;丙烯酰胺含量与单独热烫、未处理组相比明显减少(P0.05)。结论运用半胱氨酸溶液浸泡并联热烫预处理云南脆皮薯条能有效降低食物中的丙烯酰胺同时保留食物风味品质。     

Reduction of acrylamide formation by vanadium salt in potato French fries and chips

The effects of vanadyl sulphate on the formation of acrylamide have been studied in fried potato products, such as French fries and chips. Acrylamide formation was inhibited by 30.3%, 53.3% and 89.3% when the sliced potato strips were soaked in 0.001, 0.01 and 0.1 M vanadyl sulphate (VOSO₄) solutions, respectively, for 60 min before frying. Moreover, 57.7%, 71.4% and 92.5% inhibition of acrylamide formation was observed when chips were soaked in the respective vanadyl sulphate solution before frying. In a separate model reaction, a solution containing an equimolar concentration of l-asparagine and d-glucose showed a significant inhibition of acrylamide formation when heated at 150 °C for 30 min in the presence of vanadyl sulphate (VOSO₄). The results indicate that the binding of VO²⁺ to asparagine and the decrease in the pH of the potato samples resulted in a significant reduction of acrylamide formation in fried potato products.     

Factors dominating adhesion of NaCl onto potato chips

ABSTRACT:  In this study, the adhesion factors examined were time between frying and coating, surface oil content, chip temperature, oil composition, NaCl size, NaCl shape, and electrostatic coating. Three different surface oil content potato chips, high, low, and no, were produced. Oils used were soybean, olive, corn, peanut, and coconut. After frying, chips were coated immediately, after 1 d, and after 1 mo. NaCl crystals of 5 different particle sizes (24.7, 123, 259, 291, and 388 μm) were coated both electrostatically and nonelectrostatically. Adhesion of cubic, dendritic, and flake crystals was examined. Chips were coated at different temperatures. Chips with high surface oil had the highest adhesion of salt, making surface oil content the most important factor. Decreasing chip temperature decreased surface oil and adhesion. Increasing time between frying and coating reduced adhesion for low surface oil chips, but did not affect high and no surface oil chips. Changing oil composition did not affect adhesion. Increasing salt size decreased adhesion. Salt size had a greater effect on chips with lower surface oil content. When there were significant differences, cubic crystals gave the best adhesion followed by flake crystals then dendritic crystals. For high and low surface oil chips, electrostatic coating did not change adhesion of small size crystals but decreased adhesion of large salts. For no surface oil content chips, electrostatic coating improved adhesion for small salt sizes but did not affect adhesion of large crystals.     

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.     

Browning prevention in rehydrated freeze-dried non-blanched potato slices by electrical treatment

Freeze-drying (lyophilization) has many advantages. The color of the freeze-dried product resembles that of the fresh tissue, in contrast to the frequently darker color resulting from conventional oven-drying. However, freeze-dried non-blanched potato slices suffer from considerable browning following rehydration. Electrical treatment of the fresh tissue (40 V/cm for 1 min) without heating and before lyophilization reduced its browning after rehydration: L* values (lightness) of the untreated and electrically treated rehydrated tissues were 50.4 ± 0.3 and 84.3 ± 0.8, respectively. Image processing revealed that the porosity of the freeze-dried potato is not significantly influenced by the prior electrical treatment. Compression of any of the treated freeze-dried specimens always yielded characteristic sigmoid stress–strain curves. The freeze-dried blanched potato specimen was tougher than both the freeze-dried fresh potato and its electrically treated counterparts.     

Reduction of acrylamide formation in potato slices during frying

Reduction of acrylamide formation in potato chips was investigated in relation to frying temperature and three treatments before frying. Potato slices (Tivoli variety, diameter: 37 mm, width: 2.2 mm) were fried at 150°C, 170°C and 190°C until reaching moisture contents of ∼1.7 g water/100 g (total basis). Prior to frying, potato slices were treated in one of the following ways: (i) soaked in distilled water for 0 min (control), 40 min and 90 min; (ii) blanched in hot water at six different time-temperature combinations (50°C for 30 and 70 min; 70°C for 8 and 40 min; 90°C for 2 and 9 min); (iii) immersed in citric acid solutions of different concentrations (10 and 20 g/l) for half an hour. Glucose and asparagine concentration was determined in potato slices before frying, whereas acrylamide content was determined in the resultant fried potato chips. Glucose content decreased in ∼32% in potato slices soaked 90 min in distilled water. Soaked slices showed on average a reduction of acrylamide formation of 27%, 38% and 20% at 150°C, 170°C and 190°C, respectively, when they were compared against the control. Blanching reduced on average 76% and 68% of the glucose and asparagine content compared to the control. Potato slices blanched at 50°C for 70 min surprisingly had a very low acrylamide content (28 μm/kg) even when they were fried at 190°C. Potato immersion in citric acid solutions of 10 and 20 g/l reduced acrylamide formation by almost 70% for slices fried at 150°C. For the three pre-treatments studied, acrylamide formation increased dramatically as the frying temperature increased from 150°C to 190°C.     

Microstructural changes of potato cells and starch granules heated in oil

A method that mimics the frying operation was implemented to observe microstructural changes in potato cells and starch. Isolated cells were obtained by successive treatments of potato tissue with acid and alkali solutions. Potato cells were heated in oil at a rate of 40 °C/min or directly in hot oil (180 °C) using a hot stage attached to a light microscope and studied by video-microscopy. Starch granules in cells underwent rapid gelatinization, deformation and compaction into one mass that occupied the whole volume of the cell. After dehydration cells showed a distinctive outer zone and a homogeneous core. Cell walls showed no signs of disruption but at temperatures >100 °C a reduction in cell area occurred. Immersion of cells in hot oil resulted in rapid swelling of starch. Relative projected area increased by 12% after 45 s of heating. Wet isolated starch granules began to expand and gelatinize at 65 °C and became disrupted at 120 °C. No changes were observed in dry starch granules subjected to a similar treatment.     

CMI系列酶制剂在浸水中的应用研究

将自制的CMI系列浸水酶制剂应用于黄牛盐湿皮浸水工序中,并与其它浸水酶制剂进行了对比实验;采用多媒体显微镜对酶浸水后生皮的微观结构进行了观察;采用氨基酸分析仪对酶浸水后废液的蛋白质总量和氨基酸组成进行了分析。实验结果表明:自制的CMI系列浸水酶制剂在对生皮间质蛋白的水解能力、生皮的回水能力等应用性能上接近于对比浸水酶制剂,在废液中的蛋白质吸光度、羟脯氨酸吸光度、对生皮的脱脂效率等应用性能甚至更好;通过对酶浸水后生皮的切片观察可以发现自制的CMI-1浸水酶制剂可以使生皮的脂肪物质得到部分水解,对生皮的弹性纤维也有一定的作用。     

Determination of acrylamide in potato chips by a reversed-phase LC–MS method based on a stable isotope dilution assay

Potato-based products represent an important part of the daily intake of food-derived acrylamide, mainly on adolescent population from western countries. A reversed-phase liquid chromatography-mass spectrometry based on a stable isotope dilution assay was used for acrylamide analysis. Aqueous sample extraction, cleaning with Carrez solution and solid phase extraction with methanol was applied. The ratio potato/NaCl solution is critical during extraction where the optimum ratio is 0.125 g/ml NaCl 2 M solution. The use of virgin olive oil, as retaining matrix, during methanol desiccation was critical to achieve high recoveries. The method performance was validated for limit of detection (23.2 μg/kg) and quantitation (91.8 μg/kg), linearity (r > 0.999, 25–1000 μg/kg), recovery (98.8%). The method was applied on commercial potato chips; the intra-day repeatability was set at 3.9% and values were corrected with a labeled internal standard (¹³C₃-acrylamide). No significant differences on the acrylamide content were observed between industrial-scale and local-scale processed potato chips.     

Study of colour and acrylamide formation in coffee,wheat flour and potato chips during heating

The effects of heating on colour generation measured as CIE colour space parameters of L* a* b* and acrylamide formation were studied in various food matrices including green coffee, wheat flour and potato chips at different temperatures. Changes in both the acrylamide concentration and the redness parameter a* during heating at relatively higher temperatures followed a typical kinetic pattern in which an initial increase to an apparent maximum followed by a subsequent decrease was observed. The similarities between the changes in acrylamide and redness parameter a* during heating revealed that colour may be a reliable indicator of acrylamide levels in thermally processed foods. The overall results suggest that both acrylamide and redness parameter a* form as intermediate products during Maillard reaction. Since an apparent decrease was observed in its level during prolonged heating at certain temperatures, prediction of acrylamide level in foods during processing should be based on realistic reaction mechanism, instead of simple linear regression model.     

Exergy,energy and economic analysis of a V-groove assist rotating tray type solar cabinet dryer for drying potato chips

In this present work we have studied the exergy, energy and economic performance of a V-grooved type air collector with rotating trays type of solar cabinet dryer for drying potato chips in the sunny days of winter season at Bhubaneswar (20.2961° N, 85.8245° E), Odisha. The obtained results from this experiment were also compared with the performance of a flat plate air collector with rotating trays used in the same dryer. The average energy efficiency of the solar air collector (SAC) and drying chamber (DC) was found to be 73.3% and 24.8% in case of V-grooved and 60.1% and 19.3% in case of plane collector respectively. The average exergy inflow, outflow, loss and efficiency of the drying chamber in case of V-grooved collector was found as 19.7 W, 11.82 W, 7.88 W and 58.14% where as it was 22.3 W, 12.96 W, 9.34.88 W and 56.12% in case of plane collector respectively. Similarly the average exergy inflow, outflow, loss and efficiency of the SAC in case of V-grooved was found as 845 W, 20.1 W, 824.9 W and 1.99% where as it was 830 W, 22 W, 808 W and 2.28% in case of plane collector respectively. The average exergy and energy efficiency of the V-grooved type chamber are found to be 3.47% and 22.17% higher respectively as compared to plane collector. The air temperature at the inlet and outlet of the SAC and DC mainly affects the exergy value.     

On-line monitoring of fat,dry matter and acrylamide contents in potato chips using near infrared interactance and visual reflectance imaging

The contents of dry matter, oil and acrylamide are some of the most relevant parameters in the quality control of potato chips. Near infrared spectroscopy (NIR) is a common technique for routine analysis of bulk chemistry in different raw materials and products because it allows a fast and non-destructive analysis of samples. The objective of this research was to investigate the possibilities of using on-line NIR monitoring of acrylamide, moisture and oil content in potato chips. Sixty samples of potato chips from individual frying runs were measured on-line using a VIS/NIR interactance line scanner. The same samples were analysed in the laboratory to determine their corresponding moisture, acrylamide and oil contents. The mean VIS and NIR spectra for the 60 samples were modelled against the reference values for acrylamide, fat and dry matter using partial least squares regression (PLSR), and the regression models were validated using full cross-validation. On-line NIR interactance was found to predict fat and dry matter of potato chips with high accuracy, i.e. prediction errors of 0.99 and 0.86% (w/w), respectively. The corresponding correlations between predicted values and reference values were 0.99 and 0.97 for fat and dry matter. For acrylamide an average prediction error of 266 μg/kg was achieved using NIR and VIS signals in combination. The correlation between predicted values and reference values was 0.83 for this model. The system may be used to separate samples with very high acrylamide contents from samples with average to low contents.     

Impact of additives to lower the formation of acrylamide in a potato model system through pH reduction and other mechanisms

The impact on acrylamide formation of several additives was investigated as well as the mechanisms behind it. In a potato powder model system, sodium acid pyrophosphate, citric, acetic and l-lactic acid significantly reduced the final acrylamide content, merely due to the lowering of the pH. Free glycine, l-lysine and l-cysteine also lowered acrylamide, while keeping the pH at its original level. l-glutamine increased the formation of acrylamide. A synergistic acrylamide lowering effect was observed, adding citric acid and glycine or l-lysine to the model system. Yet, a combination of these amino acids with acetic acid appeared to induce a restricted antagonistic acrylamide lowering effect. Calcium and magnesium ions induced a supplementary acrylamide reduction in addition to a lower pH of the food matrix. No lowering effect was however observed upon NaCl addition to the model system.     

Development of a rapid colorimetric method for the determination of chlorogenic acid in freeze-dried potato tubers

After-cooking blackening (ACB) in potato cultivars results from the formation of complex compounds of chlorogenic acid and iron ions. At present the estimation of chlorogenic acid content represents the most reliable method for predicting the extent of ACB in material in a potato breeding programme to allow subsequent selection. A number of methods for determining chlorogenic acid levels, including high performance liquid chromatography, sodium nitrite and other colorimetric and chromatographic assays, are evaluated. A rapid screening method for the direct determination of chlorogenic acid levels is described, and its application within a breeding programme and the results obtained from a number of cultivars are discussed.     

Probabilistic representation of the exposure of consumers to Clostridium botulinum neurotoxin in a minimally processed potato product

We have examined the potential of a well-specified, minimally processed potato product as a vehicle for the exposure of consumers to Clostridium botulinum neurotoxin. The product is a relatively simple combination of raw potato flakes, flour, starch and other minor ingredients and has an extended lifetime under refrigeration conditions. A combination of information and data, from a variety of sources that includes the manufacturer, has shown that the product is particularly safe with respect to non-proteolytic C. botulinum hazards. The model concentrates on a simple end point, the toxicity of an individual retail unit of the product at the point of consumer preparation, which is related to an individual risk. The probabilistic analysis was built using Bayesian Belief Network (BBN) techniques.     

Probabilistic representation of the exposure of consumers to Clostridium botulinum neurotoxin in a minimally processed potato product

We have examined the potential of a well-specified, minimally processed potato product as a vehicle for the exposure of consumers to Clostridium botulinum neurotoxin. The product is a relatively simple combination of raw potato flakes, flour, starch and other minor ingredients and has an extended lifetime under refrigeration conditions. A combination of information and data, from a variety of sources that includes the manufacturer, has shown that the product is particularly safe with respect to non-proteolytic C. botulinum hazards. The model concentrates on a simple end point, the toxicity of an individual retail unit of the product at the point of consumer preparation, which is related to an individual risk. The probabilistic analysis was built using Bayesian Belief Network (BBN) techniques.