Acrylamide formation in a cookie system as influenced by the oil phenol profile and degree of oxidation

The purpose of this study was to investigate the effect of the olive oil phenolic compounds as well as of thermoxidised oil on the formation of acrylamide in a cookies system. Three virgin olive oils having different phenolic profile and a thermoxidised sunflower oil were selected. Cookies were baked at 190 °C for different times (8–16 min) following a basic recipe where type of oil was the variable. Additionally to acrylamide (AA), other parameters such as colour, moisture, antioxidant activity (AOA), and hydroxymethylfurfural (HMF) were measured. Results showed that concentration and composition of phenolic moiety of virgin olive oil significantly affect the acrylamide formation, particularly at prolonged baking time. Virgin olive oil with a higher dihydroxy/monohydroxy ratio was more efficient in the AA mitigation and AA was reduced up to 20%. Colour and AOA were not significantly different among the three types of oils. However, AA is dramatically increased when thermoxidised oil is used with a parallel increase of browning and HMF. It was concluded that lipid oxidation products should be considered as an important factor in acrylamide formation during baking of fat-rich products.     

Mitigation measures for acrylamide reduction in dough-based potato snacks during their expansion by frying

ABSTRACT

Acrylamide (AA) can occur in fried and baked food products which contain reducing sugars and free asparagine. Recently, the European Commission established mitigation measures and benchmark levels for the reduction of AA in food. The content of reducing sugars in raw materials and the temperature and time of the expansion process by frying were considered in this study of the preparation of dough-based potato snacks, mainly destined for children. Final moisture and bulk density were also evaluated. An increase from 0.15 to 1.0% in reducing sugar content, due to the addition of micro-ingredients in the dough, caused a remarkable AA increase of five- to six-fold. During frying at temperatures between 175 and 195°C, AA was produced after only a few seconds; the AA content was affected more by process time than by temperature. The best temperature/time conditions for expansion by frying were 185°C for 8 s.     

Brown potato croquettes low in acrylamide by coating with egg/breadcrumbs

Potato croquettes are preparations of mashed potato or potato powder with milk powder or egg, fried in oil or baked in the oven. Product identity calls for fairly strong browning, which may cause high acrylamide contents. Prefabricates from the Swiss market resulted in products of intermediate acrylamide content (50–570 µg/kg), strongly depending on frying conditions. The potential of acrylamide formation of these products was modest, since the potato powder used was low in reducing sugars and asparagine. Defatted milk powder increased the 120 °C potential by 200–700 µg/kg (lactose), whereas egg was approximately neutral. Coating with egg/breadcrumbs resulted in stronger browning and at the same time in reduced acrylamide formation. It shields the potato from the heat by a material the browning of which is not linked with acrylamide formation. Croquettes prepared from fresh potato confirmed that coating with egg/breadcrumbs improves the product quality while strongly decreasing the acrylamide content.     

Effect of frying time on acrylamide content and quality aspects of French fries

The effect of frying time on quality and acrylamide (AA) content of French fried potatoes, obtained simulating home-cooking practices, was studied in order to investigate the optimal conditions to minimize the amount of produced toxicant together with the maintenance of good culinary quality. French fries were obtained from fresh potatoes using a domestic fryer with static basket; a 4:1 oil:product ratio and a fixed initial oil temperature of 180 °C were used. Several batches were fried at different times (3, 4, 5, 6, 7, 8, 9 min). During frying tests the oil, the sticks surface and core temperatures were measured by thermocouples. Analysis of water removal, oil uptake, colour, texture and AA content were carried out on fried final products. AA content increased exponentially increasing the frying time. In our working conditions after around 4 min of frying, when the temperature of potato surface and the oil bath reached, respectively, 120 and 140 °C, the increase of time became a key factor in terms of the quantity of AA and its formation rate. On the basis of colour, oil content and AA level the best culinary product was obtained after 5 min of frying.     

Quality Attributes of Muffins: Effect of Baking Operative Conditions

Muffins are sweet baked products highly appreciated by consumers because of their soft texture and characteristic taste. The aim of this work was to study the influence of baking conditions on muffins’ quality. Surface crust color was monitored during baking tests at oven temperatures ranging from 140 to 220 °C, and browning kinetics was modeled by means of a browning index, BI, which follows a logistic model; a joint analysis of core temperature profile and BI curve can assist in the prediction of baking time. Finally, weight loss, crust/crumb ratio, crumb and crust moisture content, porosity, crumb and global densities, and texture were measured in the already baked muffin. The water content in the crumb remains almost constant, while considerable dehydration occurs in the crust. Finally, the results showed that intermediate oven temperatures led to a more porous, aerated, and soft crumb, with intermediate textural properties.     

Color changes and acrylamide formation in fried potato slices

The objective of this work was to study the kinetics of browning during deep-fat frying of blanched and unblanched potato chips by using the dynamic method and to find a relationship between browning development and acrylamide formation. 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 acrylamide content and final color were measured. Color changes were recorded at different sampling times during frying at the three mentioned temperatures using the chromatic redness parameter a¹. Experimental data of surface temperature, moisture content and color change in potato chips during frying were fit to empirical relationships, with correlation coefficients greater than 90%. A first-order rate equation was used to model the kinetics of color change. In all cases, the Arrhenius activation energy decreases alongside with decreasing chip moisture content. Blanching reduced acrylamide formation in potato chips in ∼64% (average value) in comparison with control chips at the three oil temperatures tested. For the two pre-treatments studied, average acrylamide content increased ∼58 times as the frying temperature increased from 120 to 180 °C. There was a linear correlation between acrylamide content of potato chips and their color represented by the redness component a¹ in the range of the temperatures studied.     

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.     

Effects of Initial Moisture Content on the Oil Absorption Behavior of Potato Chips During Frying Process

During frying process, whether and how moisture content in materials affects oil absorption remain unclear. Herein, we provided direct evidence suggesting that although the initial moisture content had no significant effect either on the final oil content or oil fraction, the moisture content did greatly affect the rate of oil absorption. We analyzed the total oil (TO), surface oil (SO), structural oil (STO), penetrated surface oil (PSO), and oil distribution during frying process in once-fried and twice-fried potato chips, and found that SO fraction was lowest (about 0.90-1.66 %) among three different fractions of TO, while PSO was the dominant section (about 50 %) for TO. Surprisingly, there were no significant difference among the final TO, SO, STO, and PSO for two kinds potato chips (P > 0.05), a finding suggesting that the initial moisture content itself might have no effect on oil absorption. Compared with once-fried potato chips, twice-fried chips much quicker (around sevenfold) reached equilibrium at 180 °C, which might be attributed to no inner resistance of water evaporation in twice-fried potato chips. More importantly, our confocal laser scanning microscopy (CLSM) inspection established that oil of twice-fried chips entered the core faster than once-fried chips. Oil followed the cell shapes and located in cell walls and inside the intercellular spaces for both samples. Taken together, this study provided compelling new data to clarify the relationship between the initial moisture content and oil absorption during frying process, and laid the groundwork for introducing a pre-drying strategy to frying process in food industry.     

Mitigation of acrylamide formation in cookies by using Maillard reaction products as recipe modifier in a combined partial conventional baking and radio frequency post-baking process

This study aimed to mitigate acrylamide formation in cookies by lowering thermal energy input along with certain recipe modifications. Lowering temperature required longer cooking times as expected in order to achieve desired final moisture content. To shorten cooking time, conventional baking was combined with radio frequency post-baking process. Lack of development of surface browning in cookies during lower-temperature baking could be overcome by adding the Maillard reaction products (MRP) into dough. The MRP used to modify dough was prepared by heating a binary mixture of arginine and glucose at 100?°C for 6?h or by overbaking thin dough-layered disks. In comparison with control cookie baked at 205?°C for 11?min, combined conventional baking (205?°C for 8?min) and radio frequency post-drying process (45?s) decreased acrylamide formation in biscuits by up to 50?%. The use of Maillard reaction products to improve the visual acceptability of cookies to the consumer may have applications in food industry.     

Interaction between Maillard reaction products and lipid oxidation in starch‐based model systems

The effect of Maillard reaction products (MRPs) on the kinetics of lipid oxidation in intermediate‐moisture model systems containing pregelatinised starch, glucose, lysine and soybean oil has been studied. The samples, either containing all components or excluding one or more of them, were heated at 100 °C for different times. Lipid oxidation and browning indices were measured and the results confirmed the ability of MRPs to retard peroxide formation. Under the conditions adopted, the rate of the Maillard reaction was increased by the presence of the oil and its oxidation products. The antioxidant action of MRPs was also evaluated using a peroxide‐scavenging test based on crocin bleaching. The results demonstrated that antioxidant activity developed with increased browning of the samples. © 2000 Society of Chemical Industry     

Browning of salted sun-dried fish

The lipid of traditional salted, sun-dried fish is highly susceptible to oxidation during processing and storage at tropical ambient temperatures (25–30°C), leading to browning and potential loss of nutritional and economic value of the product. Determinations of extractable fluorescence and soluble brown colour have been found to be relevant indicators of the high degree of lipid oxidation in such fish. Studies on model systems consisting of aerated fish oil and a range of components natural to fish confirmed that, at 25°C, the products of lipid oxidation reacted with phospholipids and amino acids to produce significant fluorescence. Similarly, proteins and amino acids interacted with lipid oxidation products to produce browning, although at 25°C, this only occurred in the presence of water. Temperatures above 50°C are required for the development of browning of aerated fish oil alone. The level of free amino acids in salted, sun-dried fish was found to decrease during storage which correlates with amino acid involvement in fluorescence and colour production. The fluorescence/colour can be related mechanistically to the development of lipid oxidation products and hence provides a realistic basis for their acting as indicators of extensive lipid oxidation.     

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.     

EVALUATION OF THE TEXTURE OF FRIED POTATOES

Texture of potatoes with different shapes (slices and strips) were evaluated after frying and in some cases after baking. Blanched and unblanched potato slices (Bintje variety) were fried at four oil temperatures: 160, 170, 180 and 190C until reaching a moisture content of ∼1.7%. A puncture test with three point support for the slices was applied to measure the texture of potato chips using the following parameters extracted from the force versus distance curves: maximum force of break (MFB) and deformation of break (DB). These two parameters were useful to follow the changes in texture of the fried slices with moisture content at different frying temperatures. Blanched and unblanched potato strips were partially fried at 160C and 190C for 60, 90 and 120 s. The par-fried potatoes were frozen at -20C for one day after which they were baked at 200C for 15 min. The texture of the baked potato strips was evaluated using a bending test with two support points. From the force versus distance curves, two parameters were extracted: maximum force of deformation (MFD) and maximum deformation (MD). Significant higher MFB and lower DB values (P > 0.1) for unblanched fried slices indicate that these are crispier than blanched chips for moisture contents lower than 4% (6.59 N and 0.62 mm vs 5.74 N and vs 0.75 mm for unblanched and blanched chips, respectively, average values for the four frying temperatures employed). There was no effect of the frying temperature and the pretreatment (blanching or unblanching) on the texture of the frozen par-fried potatoes after baking when compared at the same residual moisture content, but blanched potato strips lost moisture more slowly both in frying and in baking.     

TIMED COLOR CHANGES AMONG RAW AND BAKED POTATO VARIETIES

Color changes in twenty two lines of potatoes by the browning reaction were measured and evaluated by Hunter color value and National Bureau of Standard (NBS) unit of color difference (ΔE). The relationship between color change and total solids content was evaluated (p < 0.05). CO87106–5 and AC87313–3 contained the highest solids content, while CO86218–2 and CO82142–4 had the lowest solids content. Overall color change in raw potatoes by browning showed CO86142–3 with the least color change and AC87084–2 with the most. Hunter color values for the browning reaction changed with time. As time increased, potatoes became darker, redder and bluer. Moreover, all of the Hunter color values were significantly changed by baking. Color of baked BC0894–2, CO86142–3 and CO87106–5 were the least changed, while that of the baked CO8001–5, Russet Norkotah and TC1406–1 were the most changed. Degree of browning in raw potato was not correlated with total solids content, but did show a negative relationship (r =−0.12). Also, rate of color change by the browning reaction in raw potato was not related to potato total solids (r =−0.10). Color change by baking also was not correlated with total solids content (r =−0.36). Raw potato color change was positively correlated to baked potato color change (r = 0.42). Genotype of the potatoes was closely related with     

The glass transition approach to determination of drying protocols for colour stability in dehydrated pear slices

Colour stability in dehydrated fruit is often attained by use of sulphite treatment to inhibit browning during processing and storage. However, colour stability may be able to be conferred on products by ensuring that the molecular mobility is restricted in dried fruit by drying to sufficiently low moisture to raise the glass transition temperature (under mild conditions). Pear slices were dehydrated at a low temperature (40 °C) to a low final moisture content (below 5%) after it was shown that, for a moisture content of 22% (which is the moisture content of commercial dehydrated pears) pretreatment with sulphite would be necessary to stabilise the colour. The use of longer drying regimes resulted in a moisture content where the food matrix would be closer to the glassy state and conferred colour stability on the dehydrated product compared to a product containing more moisture. For these low‐moisture products, pretreatment with sulphite would not be necessary to preserve colour stability.     

Determination of Hexanal—an Indicator of Lipid Oxidation by Static Headspace Gas Chromatography (SHS-GC) in Fat-Rich Food Matrices

Lipid oxidation is one of the most detrimental processes in food, occurring during production and storage, and influences food aroma and taste. Analysis of volatile lipid oxidation products provides an insight into the oxidation and some volatiles, such as hexanal can be markers of undergoing oxidation processes. A method for hexanal determination in oil, potato chips, and mayonnaise matrices with high fat content was developed. Water was used as a matrix for comparison of performance of oil, emulsion, or nonhomogenous matrix in hexanal release. Sample weight, mixing with water, equilibrium temperature, and time were determined for each matrix to provide the highest extraction efficiency. The developed method is characterized by detection limits of 0.06, 0.07, and 0.09 mg/kg for rapeseed oil, potato chips, and mayonnaise, respectively, and linearity for all matrices was 0.999 for a range of 0.1–50 (potato chips) or 200 mg/kg (rest of matrices). Repeatability of the method was in a range of 3.11–5.43 % and intermediate precision of 3.59–5.96 % depending on a fat-rich product analyzed. The developed method presents an easy and automated approach to determine hexanal as a marker for lipid oxidation in oils and high fat products.     

不同焙烤条件的烤马铃薯条品质对比

为了探究烤马铃薯条的焙烤工艺,对比分析了不同焙烤温度和时间组合下,马铃薯条的水分含量、水分状态、抗氧化性、总酚含量、风味物质、色度及质构特性的变化规律。结果表明,随着焙烤温度的升高和焙烤时间的缩短,烤马铃薯条的水分流动性和水分含量均呈现降低的趋势,硬度和咀嚼度呈现先下降后上升趋势,抗氧化性和总酚含量呈现上升的趋势;烤马铃薯条色泽逐渐加深。不同的焙烤条件组合对烤马铃薯条主要风味物质种类的影响不显著,但对风味物质含量的影响较为明显。其中160℃烤25 min条件下,马铃薯条硬度为1532.14 g;而DPPH自由基清除率为85.25%,总酚含量为279.18 mg/100 g,相对较高;且香味明显,色泽鲜亮,是比较合适的焙烤条件。该研究可为马铃薯在食用或加工中选择适宜的焙烤条件提供理论参考。     

Production of acrylamide in agricultural products by cooking

Some model studies were performed using various agricultural Products, to clarify the relation between cooking conditions and production of acrylamide (AA). Disc chips made from dried mashed potato, corn meal, wheat flour, rice flour (jyohshin-ko) and glutinous rice flour (shiratama-ko), and dried sesame (arai-goma) and dried almond were baked at 120-200 degrees C for 5-20 min, and the samples were analyzed for the levels of AA. When the samples were baked for 10 min, the highest production of AA was observed at 180-200 degrees C. When the samples were baked at 180 degrees C, AA levels in agricultural products except sesame were highest after baking for 10 min. Vegetables and fruit were baked at 220 degrees C for 5 min with a oven, high AA concentrations were found in baked potato, asparagus, pumpkin, eggplant and green gram sprouts. Concentrations of AA in potato, asparagus and green gram sprouts baked after being pre-cooked by microwave irradiation were higher than those in the products baked without being precooked. On the other hand, the precooking by boiling reduced the production of AA by baking to 1/10-1/4. Acrylamide was not found in microwaved or boiled vegetables. High free asparagine concentrations in crops tended to result in high concentrations of AA being produced by heating the agricultural products.     

Effects of Added Phenolics on the Lipid Deterioration and Antioxidant Content of Deep-Fried Potato Fritters

The health benefits of phenolic antioxidants justify their inclusion in foods like deep-fried potato fritters that are exposed to high heat during processing. In this study, phenolic antioxidants [quercetin, rutin or an apple phenolic extract (APE)] were incorporated into batters that were subsequently used in the preparation of deep-fried potato fritters. The fritters were deep fried at 180 °C for 2.5 min or 165 °C for 3 min using fresh or used canola oil. The study aimed to investigate the effect of added phenolic antioxidants on the lipid deterioration during deep frying potato fritters. The effectiveness of these phenolics against lipid deterioration was also examined for the potato fritters that have been left in the air at room temperature for 0.5 or 1 h after deep frying. The total oxidation (Totox) value (based on the peroxide value and p-anisidine value) and free fatty acid content of the oil extracted from the deep-fried potato fritters, as well as the total extractable phenolic content, of the fritters were evaluated. Results showed that APE, quercetin and rutin suppressed oil deterioration to different extents, and their effectiveness was influenced by deep-frying conditions, the number of times the oil had been used and the time period that the fritter was exposed to the air after deep frying. For the fresh or singly used oil, the recommended deep-frying parameters are 180 °C for 2.5 min (“high heat short time” approach). For oil used more than once, deep frying of potato fritters at 165 °C for 3 min (“low heat long time” approach) is generally recommended. Adding phenolics to the batter used for making potato fritters before deep frying increases product nutritional value and reduces oil oxidation, which indicates the feasibility of producing healthier potato fritters.     

Factors affecting wafer sheet quality

Wafers are low‐moisture‐baked foods. They are formed from a batter and baked between hot plates. The quality of wafer sheets is mainly controlled by flour property, water level and temperature, mixing action, baking time and temperature. The quality is judged by attributes of the batter such as the density, viscosity, holding time and temperature, and by properties of the wafer such as weight, surface colour, fragility and moisture content. In this study, the batter‐specific gravity of 1.11–1.19 was recorded. Water and gluten content did not affect density. Water level, but not gluten content, however affected viscosity. Batter holding time drastically changed viscosity. The temperature of plates did significantly affect bake time. For wafer sheets with a high quality, 155–165% water level, 170 °C baking temperature and 2 min of bake time were found to be adequate. Wafer sheets baked at the lower temperatures stuck to the plates and broke up to several pieces. At a lower water level (<145%) and baking temperature of 150 °C, tough and flinty sheets were obtained, whereas at a water level higher than 160% and a higher temperature (190 °C), fragile sheets were obtained.