Kinetic Model for the Formation of Acrylamide during the Finish-Frying of Commercial French Fries

Acrylamide is formed from reducing sugars and asparagine during the preparation of French fries. The commercial preparation of French fries is a multistage process involving the preparation of frozen, par-fried potato strips for distribution to catering outlets, where they are finish-fried. The initial blanching, treatment in glucose solution, and par-frying steps are crucial because they determine the levels of precursors present at the beginning of the finish-frying process. To minimize the quantities of acrylamide in cooked fries, it is important to understand the impact of each stage on the formation of acrylamide. Acrylamide, amino acids, sugars, moisture, fat, and color were monitored at time intervals during the frying of potato strips that had been dipped in various concentrations of glucose and fructose during a typical pretreatment. A mathematical model based on the fundamental chemical reaction pathways of the finish-frying was developed, incorporating moisture and temperature gradients in the fries. This showed the contribution of both glucose and fructose to the generation of acrylamide and accurately predicted the acrylamide content of the final fries.     

Acrylamide in French fries: influence of free amino acids and sugars

The free amino acid profile and sugar (fructose, glucose, and sucrose) composition were determined in potato samples selected to give a large range of variation (a total of 66 samples). From these samples French fries were produced in a laboratory-scale simulation of an industrial process followed by a finish fry at 180 degrees C for 3.5 min using a restaurant fryer. The final product was blast frozen and analyzed for acrylamide. Acrylamide was detected in all samples, but its concentration varied significantly from 50 to 1800 ng/g. For isotope dilution (13C3) acrylamide analysis, samples were extracted with water, cleaned up on HLB Oasis polymeric and Accucat mixed mode anion and cation exchange SPE columns, and analyzed by LC-MS/MS. Statistical analysis of the data indicates that the effect of sugars and asparagine on the concentration of acrylamide in French fries is positive and significant (p < 0.001). It appears that one of the ways acrylamide formation in French fries can be effectively controlled is by the use of raw products with low sugar (and to a lesser degree, asparagine) content.     

Reduction of acrylamide level in french fries by employing a temperature program during frying

In this study, the effect of employing an oil temperature program during frying on the acrylamide content of French fries was investigated. The frying conditions that could lead to lower acrylamide levels in French fries were first simulated by means of an experimentally validated frying model. Then, experiments were conducted to test the simulated conditions in real frying process. Different time/temperature combinations (4 min at 170 degrees C, 2 min at 170 degrees C + 2 min at 150 degrees C, 1 min at 170 degrees C + 3 min at 150 degrees C, 1 min at 190 degrees C + 3 min at 150 degrees C) were employed for frying potato strips (8.5 x 8.5 x 70 mm), and the resultant acrylamide levels were determined with a gas chromatography-mass spectrometry (GC-MS) method. The results indicated that acrylamide levels in French fries can be reduced by half if the final stage of the frying process employs a lower oil temperature. Therefore, the method appears to be an effective way of controlling the acrylamide level in the final product.     

Influence of storage practices on acrylamide formation during potato frying

A number of parameters linked to storage of potatoes were evaluated with regard to their potential to influence the acrylamide formation in French fries. Acrylamide, which is a potential human carcinogen, is reported to be formed during the frying of potatoes as a result of the reactions between asparagine and reducing sugars. This study was conducted using three potato varieties (Bintje, Ramos, and Saturna) typically used in Belgium, The Netherlands, and the northern part of France for French fry and crisp production. Saturna, mainly used in crisp production, appeared to be the least susceptible for acrylamide formation during frying. Especially storage at low temperatures (4 degrees C) compared to storage at 8 degrees C seemed to enhance acrylamide formation due to a strong increase in reducing sugars caused by low-temperature storage. Because of the reversible nature of this physiological reaction, it was possible to achieve a significant reduction of the reducing sugars after a reconditioning of the cold-stored potatoes for 3 weeks at 15 degrees C. All changes in acrylamide concentrations could mainly be explained by the reducing sugar content of the potato (R2 = 0.84, n = 160). This means that, by ensuring a low reducing sugar content of the potato tuber, the risk for acrylamide formation will largely be reduced. Finally the use of a sprout inhibitor did not influence the composition of the potato, and thus acrylamide formation was not susceptible to this treatment.     

Addition of glycine reduces the content of acrylamide in cereal and potato products

The effects of adding amino acids on the content of acrylamide in potato crisps, French fries, flat breads, and bread crusts were investigated. Addition of glycine or glutamine during blanching of crisps reduced the amount of acrylamide by approximately 30% compared to no addition. No effect was found in French fries. Addition of glycine during doughmaking significantly reduced acrylamide in both flat breads and bread crusts. In bread crusts the reduction of acrylamide ranged from 50 to >90% depending on the baking condition. In flat breads the reduction varied between 60 and >95%.     

Addition of antioxidant of bamboo leaves (AOB) effectively reduces acrylamide formation in potato crisps and French fries

The present study was to demonstrate the efficiency of antioxidant of bamboo leaves (AOB) on the reduction of acrylamide during thermal processing and to summarize the optimal level of AOB applied in potato-based products. Potato crisps and French fries were immersed into different contents of AOB solution, and the frying processing parameters were optimized. The acrylamide content was determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The sensory evaluation was performed in double blind manner. Our results showed that nearly 74.1% and 76.1% of acrylamide in potato crisps and French fries was reduced when the AOB addition ratio was 0.1% and 0.01% (w/w), respectively. The maximum inhibitory rate was achieved when the immersion time was designed as 60 s. Sensory evaluation results showed that the crispness and flavor of potato crisps and French fries processed by AOB solution had no significant difference compared to normal potato matrixes (P > 0.05) when the AOB addition ratio was <0.5% (w/w). These results suggested that AOB could significantly reduce acrylamide formation in potato-based foods and keep original crispness and flavor of potato matrixes. This study could be regarded as a pioneer contribution on the reduction of acrylamide in various foods by natural antioxidants.     

Improving potato storage and processing characteristics through all-native DNA transformation

The dominant potato (Solanum tuberosum) variety for French fry production in the United States is the 131-year-old Russet Burbank. Market penetration of the higher yielding and more uniform Ranger Russet variety is limited to about one-fifth of that of the Russet Burbank because of two storage deficits: black spot bruise sensitivity and high levels of cold-induced sweetening. Here, these trait weaknesses are turned into strengths by simultaneously lowering the expression of Ranger Russet's tuber-expressed polyphenol oxidase (Ppo), starch-associated R1, and phosphorylase-L (PhL) genes. This genetic modification was accomplished without inserting any foreign DNA into the plant genome. French fries from the intragenic potatoes also contained reduced amounts of the antinutritional compound acrylamide while, unexpectedly, displaying enhanced sensory characteristics.     

Selection criteria for potato tubers to minimize acrylamide formation during frying

A number of parameters linked to the selection of potato tubers were evaluated with regard to their potential to influence acrylamide formation in French fries. The formation of acrylamide, which is a potential human carcinogen, can be minimized for a big extent by the selection of an appropriate tuber. This study focused on the following selection criteria: variety as influenced by storage time and soil type, underwater weight, and tuber size. A total of 16 varieties were compared, concerning their potential for acrylamide formation. From that survey, certain varieties, such as Tebina and Quincy, could be appointed as unsuitable for frying. The differences in the potential of acrylamide formation between the varieties could mainly be explained by the reducing sugar content of the potato (R2 = 0.82, n = 96). The investigated type of soil and storage time at 8 degrees C appeared to have a minor influence on the acrylamide formation during frying. On the other hand, the tuber size of the potato did contribute in a significant manner to the acrylamide formation. Smaller tubers were more susceptible to acrylamide formation and should be avoided in the frying process. The last selection parameter, the underwater weight, appeared to be of minor importance in the acrylamide formation. On the basis of these simple selection criteria, it is possible to make a first screening of potatoes to reduce the acrylamide formation during frying.     

Influence of fertilization on acrylamide formation during frying of potatoes harvested in 2003

The quality of the potato has been found to vary, when grown under different agricultural and environmental conditions, such as the level of fertilization. Consequently these factors may influence the acrylamide formation during the preparation of French fries. These assumptions were studied on three varieties: Bintje, Ramos, and Saturna from the harvest of 2003. Decreasing N fertilization caused increases in the reducing sugar concentration from 60% up to 100% on DM for all varieties studied. Due to a high correlation between the reducing sugar content and the generation of acrylamide during frying, this resulted in a parallel increase in the acrylamide concentration of the French fries. Thus by lowering the amount of N fertilizer, an increase of 30-65% of the acrylamide generation during frying could be observed. It seems of extreme importance to find an appropriate balance between the level of N fertilizer in order to diminish acrylamide formation but on the other hand to obtain an acceptable tuber and to consider the environmental impact. All results reported should be seen in the perspective of the warm growing season of 2003.     

Influence of thermal processing conditions on acrylamide generation and browning in a potato model system

Fried potato products such as French fries and chips may contain substantial amounts of acrylamide. Numerous efforts are undertaken to minimize the acrylamide content of these products while sensory properties such as color and flavor have to be respected as well. An optimization of the frying process can be achieved if the basic kinetic data of the browning and acrylamide formation are known. Therefore, heating experiments with potato powder were performed under controlled conditions (moisture, temperature, and time). Browning and acrylamide content both increased with heating time at all temperatures and moisture contents tested. The moisture content had a strong influence on the activation energy of browning and acrylamide formation. The activation energy strongly increased at moisture contents below 20%. At higher moisture contents, it was very similar for both parameters. At low moisture contents, the activation energy of acrylamide formation was larger as compared to the one for browning. This explains why the end of the frying process is very critical. Therefore, a lower temperature toward the end of frying reduces the acrylamide content of the product while color development is still good.     

Development of a stable isotope dilution assay for the quantitation of glycidamide and its application to foods and model systems

On the basis of a stable isotope dilution assay and derivatization with 2-mercaptobenzoic acid, the presence of the carcinogenic glycidamide ( 2) in processed foods was verified for the first time. Using (13)C-labeled 2 as the internal standard and the formation of the thioether derivatives, a new stable isotope dilution assay for the quantitation of 2 was developed. Application of the method on several potato samples revealed amounts between 0.3 and 1.5 mug/kg depending on the processing conditions. In a model experiment, the formation of 2 by an epoxidation of the double bond in acrylamide, that is, by a reaction with linoleic acid hydroperoxides, was established. This result was in good agreement with data showing that French fries processed in sunflower oil, which is high in linoleic acid, contained more 2 as compared to fries prepared in coconut oil. The derivatization procedure allows the simultaneous quantitation of acrylamide and glycidamide in foods.     

不同马铃薯品种的不同加工产品适宜性评价

中国是世界马铃薯生产和消费大国,2015年初,国家农业部因势而谋推进马铃薯主粮化战略,对提升马铃薯重要地位和推进马铃薯加工进步具有积极作用。系统研究马铃薯原料性状与制品品质间关系,对促进马铃薯产业发展和升级具有积极的借鉴意义。试验采用最大-最小归一化处理方法将马铃薯油炸薯片、油炸薯条及雪花全粉各个品质指标转化为一维的综合评价指标,分别与44个马铃薯原料品种的特征指标进行拟合并建立回归模型,建立的马铃薯油炸薯片综合品质评价模型决定系数R2=0.802,调整后决定系数R2=0.776,随机误差估计值σ=0.101;马铃薯油炸薯条综合品质评价模型决定系数R2=0.731,调整后R2=0.704,随机误差估计值σ=0.141;马铃薯雪花全粉综合品质评价模型决定系数R2=0.705,调整后R2=0.682,随机误差估计值σ=0.170;利用K-means聚类算法将44个品种按加工用途划分为最适宜、较适宜和不适宜3类,得出最适宜加工油炸薯片的15个品种,最适宜加工油炸薯条和雪花全粉各10个品种。结果表明,3个综合品质评价模型拟合度较高,误差较小,模型效果可靠,可用于实际马铃薯加工制品品质评价;K-means聚类结果与实际应用情况相符,可为筛选加工专用品种提供参考和借鉴。     

Influence of Nitrogen and Potassium Supply on Contents of Acrylamide Precursors in Potato Tubers and on Acrylamide Accumulation in French Fries

Fried potato products may accumulate substantial amounts of acrylamide due to high precursor contents, namely reducing sugars and asparagine. In a two-factorial experiment increasing N supply, increased the contents of reducing sugars in most cases, and resulted in higher contents of free amino acids. α -amino-N, which was tightly correlated with the contents of free amino acids, can be regarded a suitable rapid test for free asparagine for a given variety. Increasing K addition always raised the citrate contents, but lessened the contents of reducing sugars. Selected treatments were processed into French fries. Highest acrylamide contents were observed in tubers grown with high N and inadequate K supply, which also contained the highest contents of precursors. The experiment clearly demonstrates that nutrient supply has significant impact on the contents of acrylamide precursors and thus for the acrylamide formation during frying.     

Investigation of the influence of different moisture levels on acrylamide formation/elimination reactions using multiresponse analysis

The influence of water activity on the formation and elimination reactions of acrylamide was examined by means of multiresponse modeling on two different levels of complexity: basic equimolar asparagine-glucose systems and equimolar potato-based asparagine-glucose systems. To this end, model systems were first equilibrated to initial water activities in the range of 0.88-0.99 (corresponding roughly to the moisture gradient observed in French fries) and then heated at temperatures between 120 and 200 degrees C during different reaction times. For each sample, the concentration of acrylamide, glucose, asparagine, and aspartic acid was measured, as well as the extent of browning. A mechanistic model was proposed to model the five measured responses simultaneously. For both types of model systems, the model prediction was quite adequate, with the exception of the extent of browning, especially in the case of the potato-based model system. Moreover, the corresponding estimated kinetic parameters for acrylamide formation and elimination did not change significantly (based on a 95% confidence level) within the range of water activities tested, nor between the systems in the absence or presence of the potato matrix. The only remarkable difference was observed for the activation energy of acrylamide elimination, which was lower in the presence of the potato matrix, although not always significant. In general, these results confirm the generic nature of the model proposed and show that the influence of different moisture levels on acrylamide formation and elimination is minimal and that the addition of a potato matrix has little or no influence on the kinetic model and corresponding kinetic parameters.     

Influence of oil type on the amounts of acrylamide generated in a model system and in French fries

Acrylamide formation was studied by use of a new heating methodology, based on a closed stainless steel tubular reactor. Different artificial potato powder mixtures were homogenized and subsequently heated in the reactor. This procedure was first tested for its repeatability. By use of this experimental setup, it was possible to study the acrylamide formation mechanism in the different mixtures, eliminating some variable physical and chemical factors during the frying process, such as heat flux and water evaporation from and oil ingress into the food. As a first application of this optimized heating concept, the influence on acrylamide formation of the type of deep-frying oil was investigated. The results obtained from the experiments with the tubular reactor were compared with standardized French fry preparation tests. In both cases, no significant difference in acrylamide formation could be found between the various heating oils applied. Consequently, the origin of the deep-frying vegetable oils did not seem to affect the acrylamide formation in potatoes during frying. Surprisingly however, when artificial mixtures did not contain vegetable oil, significantly lower concentrations of acrylamide were detected, compared to oil-containing mixtures.     

Variation of hydrogen, carbon, nitrogen, and oxygen stable isotope ratios in an American diet: fast food meals

The stable isotopes of hydrogen, carbon, nitrogen, and oxygen provide insights into a heterotrophic organism's diet and geographic origin. Although the contribution of food delta (2)H and delta (18)O to the final tissue signal will not vary for constrained diets, it will for animals eating varied diets, that is, humans. This study surveyed the isotopic range in one portion of the American diet, fast food meals. Hamburger patties, buns, and French fries from national chain restaurants across the United States and from local restaurants (Salt Lake City, UT, and Charleston, SC) were analyzed for delta (2)H, delta (13)C, delta (15)N (patties only) and delta (18)O values. Patties and buns from local Utah restaurants were more depleted for delta (2)H, delta (13)C, and delta (18)O values than samples from other restaurants. There were no significant differences in delta values among French fries. All three components of the fast food meal displayed significant linear delta (2)H versus delta (18)O relationships (delta (2)H = 7.8delta (18)O - 237 per thousand, delta (2)H = 5.9delta (18)O - 258 per thousand, and delta (2)H = 3.3delta (18)O - 231 per thousand for patties, buns, and fries, respectively). The findings show that significant predictable variation exists in the stable isotopic composition of fast food meals. It is proposed that the variation in delta (13)C values of hamburger (beef) patties is indicative of differences in cattle-rearing practices, whereas delta (2)H and delta (18)O values are evidence of geographic variation in food sources. Although the patterns support the concept of a "continental" supermarket diet, there appears to be a strong regional component within the diet.     

Influence of processing conditions on acrylamide content in black ripe olives

The presence of acrylamide was investigated in different presentations of commercial black ripe olives, a well-known sterilized alkali-treated product. The analysis was performed by gas chromatography-mass spectrometry (GC-MS) after bromination of acrylamide, using (13C3)acrylamide as internal standard. In-house validation data for commercial ripe olives showed good precision and accuracy of the method, with repeatability below 3% and recoveries between 94 and 105%. Acrylamide was detected in all samples, but its concentration varied significantly from 176 to 1578 microg/kg of pulp. The effects of different processing conditions (two preservation methods and three darkening methods), cultivar (Hojiblanca or Manzanilla), and presentation form (pitted or sliced olives) on acrylamide content were evaluated in experiments performed in an olive-processing plant. All canned samples were sterilized at 121 degrees C for 30 min. Statistical analysis of the data indicated that the effects of darkening method and olive cultivar were the most pronounced. Acrylamide contents did not significantly differ after 6 months of storage. The small amounts of free amino acids and reducing sugars found in olives before sterilization did not significantly correlate with the acrylamide formed.     

Assessing phytoremediation potentials of selected tropical plants for acrylamide

Purpose  

Environmentally hazardous and health risk substances in animals and humans in the environment have increased as a result of continuing anthropogenic activities. Examples of these activities are food processing, laboratory, food production, industrial, and other relative activities that use various forms of acrylamide. All acrylamide in the environment are manmade. It is the building block for the polymer, polyacrylamide, which is considered to be a nontoxic additive. However, if the polymerization process is not perfect and complete, the polyacrylamide may still contain acrylamide which is toxic and may pose risks and hazards to the environment. Another form of acrylamide that may pose danger as well in the environment is the acrylamide monomer, which is also a very toxic organic substance that could affect the central nervous system of humans and is likely to be carcinogenic. Phytoremediation could be a tool to somehow absorb this neurotoxic agent and lessen the contamination in the soil. This technology could lessen the soil and water contamination by acrylamide thereby limiting the exposure of animals and humans. This study may also help solve the problem of disposing contaminated acrylamide waste materials. This study was conducted to achieve the following objectives: (1) to evaluate phytoremediation potentials of some selected tropical plants in acrylamide-contaminated soil, (2) to compare the performance of tropical plants in absorbing acrylamide through accumulation in their roots and shoots, and (3) to determine the outcome of acrylamide in the soil after treatment using the test plants with phytoremediation potentials.     

Intragenic crop improvement: combining the benefits of traditional breeding and genetic engineering

New crop varieties are developed by applying traditional breeding methods that rely on random genome modifications. These varieties combine multiple traits that support farm efficiency and acceptable yields but also contain genes associated with the production of toxins, allergens, and/or antinutritional compounds that were not considered during the selection process. Furthermore, existing cultivars frequently lack the functional genes required for specific sensory traits and the formation of health-promoting antioxidants. One new method efficiently addresses some of these issues by either silencing undesirable genes or enhancing the expression of genes that are linked to dormant beneficial traits. Rather than incorporating foreign DNA into the plant's genome, these methods transform crops with plant-derived transfer (P-) DNAs that consist of only native genetic elements. The genetic modification can be characterized molecularly so that any inadvertent transfer of undesirable DNA, as may be the case with traditional methods, is excluded. A recently developed intragenic potato plant is silenced for the polyphenol oxidase, dikinase R1, and phosphorylase-L genes in a tuber-specific manner. French fries derived from these tubers lack discolorations, display an enhanced potato flavor, and produce greatly reduced amounts of the suspected carcinogen acrylamide. It is argued that intragenic modification is unlikely to trigger phenotypic, biochemical, or physiological variation that is new to the species. Similarly, the targeted traits are similar to those that breeders select for and often have a history of domestication and reduced fitness. For these reasons, an updated regulatory system is proposed whereby intragenic crops are considered as low risk and should be cleared for commercial release in a timely and cost-effective manner. By using modern techniques to modify the same genetic material that is used by breeders, intragenic approaches may be perceived as an acceptable extension of traditional methods in crop improvement.     

Acrylamide in foods: occurrence,sources, and modeling

Acrylamide in food products-chiefly in commercially available potato chips, potato fries, cereals, and bread-was determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Samples were homogenized with water/dichloromethane, centrifuged, and filtered through a 5 kDa filter. The filtrate was cleaned up on mixed mode, anion and cation exchange (Oasis MAX and MCX) and carbon (Envirocarb) cartridges. Analysis was done by isotope dilution ([D(3)]- or [(13)C(3)]acrylamide) electrospray LC-MS/MS using a 2 x 150 mm (or 2 x 100 mm) Thermo HyperCarb column eluted with 1 mM ammonium formate in 15% (or 10% for the 2 x 100 mm column) methanol. Thirty samples of foods were analyzed. Concentrations of acrylamide varied from 14 ng/g (bread) to 3700 ng/g (potato chips). Acrylamide was formed during model reactions involving heating of mixtures of amino acids and glucose in ratios similar to those found in potatoes. In model reactions between amino acids and glucose, asparagine was found to be the main precursor of acrylamide. Thus, in the reaction between nitrogen-15 (amido)-labeled asparagine and glucose, corresponding (15)N-labeled acrylamide was formed. The yield of the model reaction is approximately 0.1%.