Effect of Cooking Method (Baking Compared with Frying) on Acrylamide Level of Potato Chips

ABSTRACT:  The effect of cooking method (baking compared with frying) on acrylamide level of potato chips was investigated in this study. Baking and frying experiments were conducted at 170, 180, and 190 °C using potato slices with a thickness of 1.4 mm. Raw potatoes were analyzed for reducing sugars and asparagine. Surface and internal temperatures of potato slices were monitored during the experiments to better explain the results. Fried and baked chips were analyzed for acrylamide content using an LC-MS method. The results showed that acrylamide level of potato chips prepared by frying increased with frying temperature (19.6 ng/g at 170 °C, 39 ng/g at 180 °C, and 95 ng/g at 190 °C). In baking, however, the highest acrylamide level was observed in potato chips prepared at 170 °C (47.8 ng/g at 170 °C, 19.3 ng/g at 180 °C, and 29.7 ng/g at 190 °C). The results showed that baking at 170 °C more than doubled the acrylamide amount that formed upon frying at the same temperature, whereas at 180 and 190 °C, the acrylamide levels of chips prepared by baking were lower than their fried counterparts.     

Characterization of Thermal Properties of Potato Dry Matter–Water and Starch–Water Systems

ABSTRACT: Potato dry matter samples of varying moisture contents were analyzed by differential scanning calorimetry (DSC). One endothermic and one exothermic transition were observed when the moisture content was < 50% (w/w) in the dry matter–water system. Both endothermic and exothermic transitions of potato dry matter were influenced by moisture content. One endothermic transition at about 66 °C was observed when the samples were reheated after 2 wk of storage at 5 °C. Gelatinization and retrogradation of starch are chiefly responsible for the endothermic transitions in the potato dry matter. The exothermic transition may originate from chemical reactions such as Maillard and caramelization during heating of a potato dry matter–water system when water is limited (< 50%, w/w) and at temperatures > 120 °C     

New potato fibre for improvement of texture and colour of wheat bread

The aim of this project was to compare the functional properties of five fibre fractions by baking of wheat bread by substitution 0, 4, 8 and 12 w/w% of wheat flour using dry potato pulp (Fibre 1), a commercial potato fibre (Fibre 2), two fibre prepared from potato pulp by enzymatic hydrolysis (Fibre 3 and 4), and one solubilised fibre (Fibre 5). The effect of chemical composition of fibre on texture, colour, specific weight and volume of wheat bread was studied using objective methods for measurement of texture characteristics, colour (L, a, b) and sensory analysis. Dry potato pulp, Potex (Fibre 2) and two enzymatically prepared fibre powders (Fibre 3 and 4) with a high concentration of lignin and insoluble non-starch polysaccharides (INCP) had a detrimental effect on bread quality by substitution of more than 8% of the wheat flour by fibre. The detrimental effect was mainly due to increased hardness, deformation energy, modulus and gumminess. Multiple linear regression analysis with forward selection was used for determination of the relationship between quality characteristics and of soluble non-starch polysaccharides (SNSP), insoluble non-starch polysaccharides (INCP), cellulose and lignin. The enzymatic solubilised fibre (Fibre 5) with a high concentration of soluble fibre and a low concentration of cellulose and lignin could be used for substitution of at least 12% wheat flour for baking of bread with an attractive colour, delicious texture and flavour.     

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。     

Effects of Cooking Conditions on the Lycopene Content in Tomatoes

ABSTRACT:  Raw tomato contains a high level of lycopene, which has been reported to have many important health benefits. However, information on the changes of the lycopene content in tomato during cooking is limited. In this study, the lycopene content in raw and thermally processed (baked, microwaved, and fried) tomato slurries was investigated and analyzed using a high-performance liquid chromatography (HPLC) method. In the thermal stability study using a pure lycopene standard, 50% of lycopene was degraded at 100 °C after 60 min, 125 °C after 20 min, and 150 °C after less than 10 min. Only 64.1% and 51.5% lycopene was retained when the tomato slurry was baked at 177 °C and 218 °C for 15 min, respectively. At these temperatures, only 37.3% and 25.1% of lycopene was retained after baking for 45 min. In 1 min of the high power of microwave heating, 64.4% of lycopene still remained. However, more degradation of lycopene in the slurry was found in the frying study. Only 36.6% and 35.5% of lycopene was retained after frying at 145 and 165 °C for 1 min, respectively.     

Improvement of the AOAC 2009.01 total dietary fibre method for bread and other high starch containing matrices

The dietary fibre (DF) content in wheat grain based food products have been established with both the classical AOAC 985.29 dietary fibre and the new AOAC 2009.01 total dietary fibre protocol. There is a good agreement between the high molecular weight dietary fibre (HMWDF) contents measured with the AOAC 2009.01 method and (DF) content measured with the classical AOAC 985.29 method in wheat grain based food products. With the AOAC 2009.01 method also a significant amount of low molar weight dietary fibre (LMWDF), ranging from 1% to 3% w/w, was measured which is not quantified with the AOAC 985.29 method.     

Comparative analysis of fruit-based functional snack bars

The aim was to develop snack bars with high dietary fibre (DF) and polyphenol contents. Snack bar base was formulated without (control bar) or with fibre (inulin or apple DF bar). Snack bar filling was formulated with or without apple polyphenol extract (APE). Nutritional assessment of snack bars was based on the total DF, phenolics, protein, fat, uronic acid (UA) and moisture contents, water activity, Hunter L^∗a^∗b^∗ colour, hardness, and phenolic composition. Results showed that snack bars with added apple DFs gave the highest amount of total DF (∼5.3% w/w). Good quantities of phenolics were also retained in the snack bars with added apple DF and APE after baking. With APE in the bar filling, the snack bars enhanced with apple DF or inulin had higher levels of extracted phenolics (2.87 and 2.22 mg catechin equivalent (CtE)/g bar) than the control bars (1.45 mg CtE/g bar). The phenolic profiles of snack bars obtained by HPLC resembled that of the APE ingredient. The Hunter L^∗a^∗b^∗ colour and water activity values suggested that the addition of APE did not cause extra browning and the resultant snack bars would possess a good shelf life. Therefore, snack bars enhanced with apple DF and APE may be a convenient functional food, offering a good source of DF and apple polyphenols.     

Pressurized liquid extraction of flavonoids from spinach

ABSTRACT:  Pressurized liquid extraction (PLE) using water and a 70:30 mixture of ethanol and water over the temperature range of 50 to 190 °C was used to extract flavonoids from dried spinach. The total phenolic content, antioxidant capacity, color, and browning indices of the extracts were also evaluated. PLE using a 70:30 mixture of ethanol and water was more effective than water in extracting flavonoids from spinach. Flavonoids were effectively extracted over the temperature band of 50 to 130 °C with water and 50 to 150 °C with ethanolic solvent. Levels of total phenolics and ORAC values increased with increasing extraction temperature, indicating that flavonoids were minor contributors to antioxidant capacity at elevated extraction temperatures. Browning of ethanolic extracts correlated highly with ORAC values over the temperature range of 50 to 190 °C, and the ORAC values of the large molecular weight fraction (> 1000 Da) increased linearly over the temperature range, indicating that Maillard polymers were the major contributors to antioxidant capacity. The results illustrate that PLE temperatures of < 130 °C for water or < 150 °C for ethanolic solvent may be used to extract flavonoids, followed by a high temperature (> 170 °C) extraction to generate antioxidant-rich moieties.     

Physicochemical characterisation of dietary fibre components and their ability to bind some process-induced mutagenic heterocyclic amines,Trp-P-1, Trp-P-2, AαC and MeAαC

The physicochemical properties of potato fibre, wheat bran and oat samples were investigated, along with their binding capability to heterocyclic amines (HCAs). Potato fibre displayed highest total dietary fibre content (71.8/100 g dry weight basis, dwb), followed by wheat bran (57.2/100 g dwb) and oat sample 2 (53.0/100 g dwb). Oat samples 1, 3 and 4 displayed considerably lower dietary fibre content (20.5–28.8/100 g, dwb). Oat samples 3 and 4 displayed highest soluble fibre content (70–83%), and oat sample 3 also displayed highest swelling and water retention capacity (WRC). Dietary fibre samples, except samples 3 and 4, displayed improved binding to HCAs as sample weight increased. The behaviour of wheat bran and potato fibre was similar to oat samples 1 and 2. Binding of MeAαC was comparatively greater than that of other HCAs. Dietary fibre fractions with high insoluble fibre and functional groups of HCAs may significantly contribute to the binding capacity.     

Characterisation of peach dietary fibre concentrate as a food ingredient

Insoluble and soluble dietary fibre (DF) fractions of peach DF concentrate, obtained by an enzymatic-chemical method, were analysed for neutral sugars, uronic acids and Klason lignin. Proximate composition, energy value, colour and water- and oil-holding capacities were also determined. Total DF constituted 31–36% dry matter (DM) of the concentrate and insoluble DF was its major fraction (20–24% DM). The high proportion of soluble fraction (11–12% DM) in the peach DF concentrate, in comparison with cereal brans, was noticeable. Insoluble and total dietary fibre contents significantly decreased throughout the harvest time of the original fresh fruit. Results suggested that peach DF concentrate may be not only an excellent DF source but an ingredient in the food industry because it showed a high affinity for water (9.12–12.09 g water/g fibre) and low energy (3.723–3.494 kcal/g). However, the use of this material could affect the colour and pH of the final product.     

Osmotic Dehydration of Tomato in Sucrose Solutions: Fick's Law Classical Modeling

ABSTRACT:  Osmotic dehydration of tomato was modeled by the classical Fick's law including shrinkage, convective resistance at the interface and the presence of water bulk flow. Tomato slices having 8 mm thickness were osmotically dehydrated in sucrose solutions at 50, 60, and 70 °Brix and at 35, 45, and 55 °C. Other experiments were done in a 70 °Brix sucrose solution at 35 °C with tomato slices of 4, 6, and 8 mm thickness and at different motion levels (velocities 0, 0.053, and 0.107 m/s). Tomato weight, water content, and °Brix of the products were measured as a function of processing time (20, 40, 80, 160, and 320 min). Results showed that temperature, concentration, thickness, and solution movement significantly influenced water loss and sucrose gain during the osmotic dehydration of tomato. The model predicted the modifications of soluble solid content and water content as a function of time in close agreement with the experimental data. Experimental Sherwood number correlations for sucrose and water were determined as Sh _s = 1.3 Re ^0.5 Sc _s^0.15 and Sh _w = 0.11 Re ^0.5 Sc _w^0.5, respectively. The effective diffusion coefficients of water (4.97 10⁻¹¹– 2.10 10⁻¹⁰ m²/s) and sucrose (3.18 10⁻¹¹– 1.69 10⁻¹⁰ m²/s) depended only on temperature through an Arrhenius-type relationship.     

Effect of germination and probiotic fermentation on nutrient composition of barley based food mixtures

Food mixtures formulated from non-germinated and germinated barley flour, whey powder and tomato pulp (2:1:1w/w) were autoclaved, cooled and fermented with 5% Lactobacillus acidophilus curd (10⁶ cells/ml) at 37 °C for 12 h. The cell count was found significantly higher (8.88 cfu/g) in the fermented food mixture formulated from germinated flour as compared to the non-germinated barley based food mixture. A significant drop in pH with corresponding increase in titratable acidity was found in the germinated barley flour based food mixture. Processing treatments like germination, autoclaving and probiotic fermentation did not bring about any significant change in ash and fat contents, but significant decrease was noticed in crude protein, crude fibre, starch, total and insoluble dietary fibre contents. The combined processing caused significant improvement in reducing sugar, thiamine, niacin, lysine and soluble dietary fibre contents of barley based food mixtures. In conclusion, a combination of germination and fermentation is a potential process for enhancing the nutritional quality of food mixtures based on coarse cereals.     

The influence of water activity on thermal stability of horseradish peroxidase

The thermal stability of horseradish peroxidase in the solid state was studied as a function of water activity, from 0.11 to 0.88. At all activities the enzyme was found to be much more stable in the solid state than in solution. Inactivation temperatures were in the range of 140–160°C. Inactivation curves show a biphasic behaviour which can be described by a model assuming two fractions (heat labile and heat stable) with independent first order inactivation kinetics. The labile fraction represents approximately 30% of the total activity. The z-value for both stable and labile fractions depends on water activity (moisture content) and has a maximum at a_w= 0.76 (44.4°C and 43.8°C, respectively).     

Water desorption isotherms of two varieties of sweet potato

Water desorption isotherms were determined for New Zealand sweet potato at 25, 40 and 55°C, and for Philippines sweet potato at 28°C. The isotherms were sigmoid in shape and of type II according to the BET classification. The data were fitted to eight two-parameter equations reported in the literature. The effect of water activity, a_w, and temperature, T °C, on the equilibrium moisture content, M _e g water/100g dry solids, was best described for New Zealand sweet potato by: Me = 20.51 T-^0.204 (a_w/(1-a_w)0.39 for a_w= 0.06–0.81     

Properties of extruded blends of wheat dried distiller grain flour with other flours

Zero, 10, 20 and 40% dried distiller grain (DDG) from wheat was blended with corn, potato, rice, and wheat flours at total moisture levels of 15 and 22% and extruded in a Brabender laboratory single screw extruder at three sets of barrel temperatures of 80, 130, 160°C; 100, 160, 210°C and 120, 190, 250°C at a constant screw speed (100 r.p.m.), screw configuration (3:1 compression ratio) and die size (3.175 mm). Resulting torque, yield, radial expansion (RA), longitudinal expansion index (LEI), density, water absorption index and colour were measured.
All the blends were successfully extruded over a wide temperature range. As the amount of DDG increased, in general torque, yield and RE decreased, and colour darkened while density and LEI increased. Wheat flour was the base material found to vary most from the above trends.     

Low-energy and high-fibre liver paté processed using potato pulp

Danish liver paté was processed using water and potato pulp from the processing of potato flour as fat substitute. The spreading characteristics of the patties were improved using Citrem as emulsifier and satisfactory texture characteristics were obtained using fibre soaked in ten times its own weight. Colour and texture were measured using a Minolta Chroma Meter for determination of the Hunter Lab values and a Farnell Quality Test System for measurement of texture characteristics. Baking loss decreased at low water to fibre ratios (water:fibre) from 3 to 4 and then increased with increasing water:fibre. No clear relationships were observed between the water:fibre and yellowness, lightness or redness. Three factors extracted by factor analysis depended especially on hardness–water:fibre, adhesion–water:fibre and cohesiveness–water:fibre, respectively. Generally, all textural characteristics were inversely correlated to water:fibre. Hardness 1 and 2, deformation energy 1 and 2, gumminess and modulus decreased in similar fashion with respect to to water:fibre, whereas adhesiveness, cohesiveness and springiness varied in relation to water:fibre. The effect of emulsifier on the texture was less than that of water:fibre. The patties with water:fibre of 10–11 were easy to spread on bread and had very attractive sensory properties. The increased substitution of fat by potato pulp and water decreased the energy content by 27% and increased the yield of baked patties by 33% (w/w).     

Significance of lipid binding on the functional and nutritional profiles of single and multigrain matrices

Lipid fractions and starch- and protein-lipid binding of single and blended oat, rye, buckwheat and wheat flour, dough and bread matrices were investigated, and results correlated with the functional and nutritional properties of the grain matrices during mixing and baking. Non-starch lipid was the most prominent fraction in terms of absolute content and as a percentage of total lipids. Free lipids, starch lipids and bound lipids were, respectively, the major, intermediate and minor lipid fractions in flours, doughs and breads. Great differences in total lipid content due to sampling result in divergences amongst lipid fraction content and distribution, especially for starch and bound lipid fractions. Lipids bound to proteins during dough mixing are translocated and bound to starch during baking. In blended samples, the higher fibre content seems to provoke a reduction of the lipid–protein and lipid–starch linkages due to interactions between fibres and endogenous biopolymers. Starch lipid showed the most significant correlations with parameters related to dough and bread performance during breadmaking, especially over the mixing step. Valuable fresh bread functional characteristics, such as high specific volume and high sensory score for softness and overall acceptability, correspond to a starch lipid’s increase due to mixing. The higher the free and starch lipids decrease by reason of temperature treatment—baking—the larger the starch hydrolysis and the higher β-glucans and total dietary fibre contents.     

Structural changes and shrinkage of potato during frying

Summary Light microscopy was used to study changes in cell size, blister formation and crust evolution during potato frying. Frying experiments with both French fries and crisps of different thickness (1–5 mm) were performed at temperatures of 140 and 180 °C. Thickness, volume and density changes were also measured. The formation of crust in French fries starts after the potato surface reached approximately 103 °C, and then the crust thickness increased linearly with the square root of frying time, this increase being faster at 180 °C. The potato volume decreased during frying, although in the late stages the volume may increase because of oil uptake and cell separation caused by entrapped water vapour. Shrinkage was adequately described by the Weibull model with a residual value, with shrinkage rate increasing with temperature and decreasing with potato thickness. The residual volume was not affected by temperature (65% for French fries and 59–30 for crisps, depending on thickness). Volume appeared to decrease mainly as the result of water loss, except for very low water content, and thus potato density changes were very small.     

Structure Oil-Absorption Relationships During Deep-Fat Frying

ABSTRACT Analysis of the oil-absorption process in deep-fat fried potato cylinders (frying temperatures of 155°C, 170°C, and 185°C) allowed to distinguish 3 oil fractions: structural oil (absorbed during frying), penetrated surface oil (suctioned during cooling), and surface oil. Results showed that a small amount of oil penetrates during frying because most of the oil was picked up at the end of the process, suggesting that oil uptake and water removal are not synchronous phenomena. After cooling, oil was located either on the surface of the chip or suctioned into the porous crust microstructure, with an inverse relationship between them for increasing frying times.     

Dielectric Properties of Potatoes and Potato Chips

SUMMARY— Dielectric properties (dielectric constant, ɛ'_r; loss tangent, tans; and dielectric loss factor, ɛ"_r) were determined for raw potatoes and for potato chips, using the precision slotted line technique. Measurements on raw potatoes were made at 77°F (25°C) and at frequencies of 300, 1,000, and 3,000 MHz (megahertz). Measurements on potato chips were made at three moisture levels; at 77°F (25°C), 125°F (51.6°C), and 180°F (82.2°0; and at frequencies of 300, 1,000, and 3,000 MHz. Moisture, total lipids, and nitrogen contents are reported for both the raw potatoes and the potato chips.
As would be expected from their high moisture content and the presence of various dissolved salts, the raw potatoes possess extremely high dielectric values.
Potato chips show a rapidly decreasing dielectric loss as moisture content is reduced; the loss values of the chips approach those of the oil used for frying them after moisture has been reduced to approximately 3% and the oil content has been increased accordingly.
For finish drying of potato chips, a frequency of 3,000 MHz will result in 3–4.5 times greater power production in the chips than will the use of a frequency of 1,000 MHz (in the moisture and temperature range at which the data were obtained). However, this difference in power production is due almost entirely to the difference in frequency since the difference in dielectric loss values at the two frequencies is quite small.