Study of acrylamide in coffee using an improved liquid chromatography mass spectrometry method: Investigation of colour changes and acrylamide formation in coffee during roasting

An improved analytical method for the determination of acrylamide in coffee is described using liquid chromatography coupled to mass spectrometric detection (LC-MS). A variety of instant, ground and laboratory roasted coffee samples were analysed using this method. The sample preparation entails extraction of acrylamide with methanol, purification with Carrez I and II solutions, evaporation and solvent change to water, and clean-up with an Oasis HLB solid-phase extraction (SPE) cartridge. The chromatographic conditions allowed separation of acrylamide and the remaining matrix co-extractives with accurate and precise quantification of acrylamide during MS detection in SIM mode. Recoveries for the spiking levels of 50, 100, 250 and 500 µg/kg ranged between 99 and 100% with relative standard deviations of less than 2%. The effects of roasting on the formation of acrylamide and colour development were also investigated at 150, 200 and 225°C. Change in the CIE (Commission Internationale de l'Eclairage) a* colour value was found to show a good correlation with the change in acrylamide. CIE a* and acrylamide data was fitted to a non-linear logarithmic function for the estimation of acrylamide level in coffee. Measured acrylamide levels in commercial roasted coffees compared well with the predicted acrylamide levels from the CIE a* values.     

Acrylamide and methylglyoxal formation in potato chips by microwaving and frying heating

In our present paper, the effect of important α‐dicarbonyl compounds of methylglyoxal on the formation of acrylamide was quantified in potato chips systems. Methylglyoxal was regarded as the main α‐dicarbonyl compound, and its formation was detected by HPLC method. There heating methods were used to study the effect on acrylamide formation. The results showed that microwaving treatment could form more acrylamide compared with frying method. After 2 min of microwaving treatment at 700 W, the acrylamide content was sharply increased from 1.77 ± 0.37 to 72.93 ± 0.72 μmol kg^?1. Microwaving treatment would promote the formation of methylglyoxal compared with frying treatment at 160 and 180 °C in potato chips. A typical linear growth curve prepared by plotting acrylamide levels vs. methylglyoxal content formed under different heating condition was observed: y = ?41.33 + 0.17x (r = 0.965). This study revealed for the first time that there is a significant correlation between methylglyoxal and acrylamide in potato chips, thus confirming the important role of dicarbonyls in the formation of acrylamide in potato chips.     

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.     

Effect of formulation and processing parameters on acrylamide formation: A case study on extrusion of blends of potato flour and semolina

Acrylamide formation in extruded snacks prepared using blends of potato flour:semolina in ratios ranging from 30:70 to 70:30 showed maximum acrylamide formation in the 70:30 blend. The extrusion was carried out at a screw speed of 120 rpm, temperature of 170 °C and moisture content of 18%. Further, the influence of extrusion processing parameters on the acrylamide formation in extruded snacks prepared from a 70:30 blend of potato flour:semolina was investigated using response surface methodology (RSM). The feed moisture was varied from 12.6% to 19.4%, die temperature from 163 to 197 °C and screw speed from 106 to 173 rpm. The extrudates so obtained showed acrylamide content ranging from 704 to 1560 μg/kg. The effect of different additives such as citric acid, calcium salts, amino acids, vitamins and their combinations on the mitigation of acrylamide formation showed calcium chloride at 50 μmol/g flour blend to reduce acrylamide formation by 65% without altering the sensory properties of the extrudates.     

Computer vision-based image analysis for the estimation of acrylamide concentrations of potato chips and french fries

In this study, digital colour images of fried potato chips and french fries were analyzed to estimate acrylamide levels based on the correlation with analyses using liquid chromatography-mass spectrometry. In fried potato images, bright yellow (Region 1), yellowish brown (Region 2) and darker brown (Region 3) regions were clearly visible, having different kinds of image pixels with characteristic mean values of red, green and blue components. Pixels of the fried potato image were classified into three sets (Set 1, Set 2 and Set 3) by means of semi-automatic and automatic segmentation. There was a strong correlation between acrylamide concentration and NA2 value, which is defined as the number of pixels in Set 2 divided by the total number of pixels of the entire fried potato image. To verify the applicability of this approach, a linear regression equation was used to estimate the acrylamide concentrations of a number of commercial potato chips and home-made french fries. Mean differences between the measured and predicted acrylamide concentrations were found to be +4 ± 14% and −14 ± 24% for commercial potato chips and home-made french fries, respectively.     

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.     

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.     

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.     

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.     

RVA study of mixtures of wheat flour and potato starches with different phosphorus contents

A rapid visco analysis (RVA) system was used to study the pasting properties of mixtures of wheat flour and potato starches with high phosphorus (HPS), medium phosphorus (MPS) and low phosphorus (LPS) contents, different granule sizes and different amylose contents. The peak viscosities, trough and breakdown, final viscosities, setback viscosities and peak times of control potato starches were found to be higher than those of wheat flour. The peak viscosities were increased significantly with increase of potato starches in the mixtures. Thus, the peak times decreased with increase of potato starch in the mixtures. The breakdown viscosities increased significantly with increase of potato starches in the mixtures and the values were found to be higher in HPS-wheat, followed by MPS-wheat and LPS-wheat mixtures. The final viscosities of HPS-wheat mixtures were highest, followed by MPS-wheat and LPS-wheat mixtures. The setback viscosities of LPS-wheat were significantly higher than those of MPS-wheat and HPS-wheat mixtures at 30 to 50% potato.     

Effect of radiofrequency heating on acrylamide formation in bakery products

This work was addressed to study the influence of radiofrequency (RF) heating on acrylamide (AA) formation in bakery products. To this purpose, leavened cakes and short dough biscuits were baked to a final moisture of 3.5 and 3.0%, respectively, by means of conventional convection heating or different combinations of conventional and RF heating. Results showed that, with respect to the baking process entirely carried out in an air-circulating oven, the RF-assisted baking process, i.e. the application of RF heating in the last stages of the baking process, resulted to be a promising strategy to keep low the AA levels in the bakery products. In particular, the best results were obtained for products which were moved from the hot-air baking to the RF heating when their residual moisture was still fairly high (around 10%). Results also suggested that, when very low values of residual moisture are required, this technological intervention is more suitable to thin bakery products, such as biscuits, than to thick products, such as leavened cakes, because of excessive browning in the internal portion as a consequence of the RF heating.     

马铃薯虾片的研制

为提高马铃薯的利用率，丰富虾片品种，改善虾片品质，采用正交试验和单因素试验，对制作马铃薯虾片的添加剂用量及工艺条件进行了研究，结果表明：生产马铃薯虾片的最佳添加剂用量为小苏打0．6％；CMC-Na0．6％；明矾0.5％：蔗糖酯0．6％。最佳工艺条件为老化时间24h；半成品中水分含量9％；油炸温度190～200℃。     

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。     

Effect of added calcium hydroxide during corn nixtamalization on acrylamide content in tortilla chips

This study has analyzed the influence of lime (Ca(OH)₂) concentration used during nixtamalization process on the physicochemical properties of nixtamalized corn flours and its effect on the acrylamide content in tortilla chips prepared from them. Flours prepared from nixtamalized corn with 0.5 and 1.0 g/100 g of Ca(OH)₂ showed higher levels of insoluble fiber, lower concentrations of calcium and ash, and a pH close to neutral. The acrylamide content of tortilla chips was correlated with the physicochemical properties of the flours. The results showed that acrylamide content was mainly affected by the ash, calcium, soluble fiber concentration in flour, as well pH value (p < 0.05). In comparison with tortilla chips made of flours prepared from nixtamalized corn with lime concentration of 1.0 g/100 g, a reduction of 52 and 36% in acrylamide content in tortilla chips made with flours prepared from nixtamalized corn with lime concentrations of 1.5 and 2.0 g/100 g, was obtained. The results suggest that controlling the concentration of Ca(OH)₂ during nixtamalization process can be used as an effective strategy for reducing acrylamide formation in fried products produced from nixtamalized corn flour.     

Effects of sulphur nutrition during potato cultivation on the formation of acrylamide and aroma compounds during cooking

Lack of sulphur nutrition during potato cultivation has been shown to have profound effects on tuber composition, affecting in particular the concentrations of free asparagine, other amino acids and sugars. This is important because free asparagine and sugars react at high temperatures to form acrylamide, a suspect carcinogen. Free amino acids and sugars also form a variety of other compounds associated with colour and flavour. In this study the volatile aroma compounds formed in potato flour heated at 180 °C for 20 min were compared for three varieties of potato grown, with and without sulphur fertiliser. Approximately 50 compounds were quantified in the headspace extracts of the heated flour, of which over 40 were affected by sulphur fertilisation and/or variety. Many of the 41 compounds found at higher concentrations in the sulphur-deficient flour were Strecker aldehydes and compounds formed from their condensation, whereas only one compound, benzaldehyde, behaved in the same way as did acrylamide and was found at higher concentrations in the sulphur-sufficient flour. The reasons for these effects are discussed.     

Enzymatic mitigation of acrylamide in fried potato chips using asparaginase from Aspergillus terreus

Acrylamide in foods is declared as carcinogen. In the present work, the effect of enzymatic pretreatment and other parameters like enzyme concentration, frying conditions with respect to temperature and time, size of potato chips, and effect of sodium chloride and citric acid on mitigation of acrylamide were studied. The concentration of acrylamide in fried potatoes after the pretreatment was found to be 815.63 μg kg^?1. The optimised asparaginase concentration for the mitigation of acrylamide was calibrated as 4 U mL^?1, and optimised frying time and temperature were 15 min and 170 °C, respectively. An in‐depth kinetic relationship for the effect of asparaginase on the mitigation of acrylamide was studied. The prime novelty of the project is focused on the immobilisation of asparaginase to nanomagnetic particles for redundant usage with stabilised enzyme activity. The work projected three stables cycles of asparaginase activity and on further usage of the immobilised enzyme resulted in decreased activity. The repeated use of immobilised asparaginase provides the advantage of decreasing cost in processing.     

The conditioning of wheat. The influence of conditioning temperature on flour yield,moisture content and colour

Two UK wheats of similar protein content but differing in hardness have been conditioned at temperatures of 4, 10.5, 19 and 28°C to a moisture content of 15.5%, using lying times in the range 2 to 24h. The milling performance of the wheats has been assessed in terms of flour yield, moisture content and grade colour figure (GCF). Flour yield was expressed as straight-run milling yield (SR) and also as total yield (TE) which included flour from the impact finishing of by-products. The use of a conditioning temperature of 28°C increased TE and SR for the hard wheat and TE for the soft wheat, but decreased SR for the latter. Both types showed a reduction in flour yield when a lying time of 2h was employed. The use of temperatures above or below 19°C led to improved GCF results. The combination of low temperatures and short lying times brought about reductions in flour moisture content but these reductions were shown to be only partially responsible for the accompanying decreases in flour yield.     

A methodology for evaluating the formation and human exposure to acrylamide through fried potato crisps

Potato crisps are a popular snack food which have been implicated as a potential source of acrylamide. This study develops a farm-to-fork human exposure assessment model for acrylamide in fried potato crisps for Irish consumers. The model used Monte Carlo simulation techniques to model the various stages from on farm production of potatoes, storage, processing, crisp production and final human consumption of potato crisps. A baseline model is created and a number of scenarios are subsequently created to look at the impact of different model assumptions and input parameters. The baseline model found that the mean level of acrylamide in potato crisps in Ireland was 720 μg/kg. Irish consumer exposure to acrylamide in potato crisps was estimated to be 0.052 and 0.064 μg/kg bw/day for males and females, respectively. A sensitivity analysis revealed the important parameters influencing the model predictions. The initial level of reducing sugars was found to be the most important parameter (correlation coefficient 0.58 and 0.57 for glucose and fructose, respectively), highlighting the importance of selecting cultivars with low reducing sugar levels for crisp production. The cooking regime had a significant impact on model predictions, highlighting the need for further research into the impact of different time and temperature combinations. Blanching and soaking of potatoes were also identified as important risk reduction processes.     

Impact of chemical pre-treatments on the acrylamide formation and sensorial quality of potato crisps

Several components were added to the blanching water of potato crisps. Calcium ions, sodium acid pyrophosphate, citric, acetic and l-lactic acid significantly reduced the final acrylamide content, as well as free glycine and l-lysine. The acids, NaCl and calcium-containing additives also lowered the oil absorption, which may have led to a reduced heat transfer and acrylamide contamination in the final product. Textural and compositional product changes may thus also influence acrylamide formation. By means of sensory analyses of these crisps, a successful combination was demonstrated between acrylamide mitigating treatments and crisps of acceptable or even superior product quality, compared to control crisps blanched in water. However, the applied components and concentration levels should be well chosen in order not to generate product-foreign flavours or undesired product colour.     

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.