Influence of vegetable shortening and emulsifiers on the unfrozen water content and textural properties of frozen French bread dough

The influence of vegetable shortening (VS) and emulsifiers (calcium stearoyl-2-lactylate (CSL) and polysorbate 80 (PS80)) on frozen French bread dough has been studied. Eight formulations without yeast were used with different quantities of VS, CSL and PS80. Dough was prepared by mixing all ingredients in a dough mixer at two speeds. The fresh dough was divided into 60 g pieces and molded. Fresh dough samples were also collected for water content and textural analyses. The dough pieces were packed, frozen in a freezer at −30°C and stored at −18°C up to 56 days. After 2, 7, 21, 28 and 56 days of frozen storage, samples were removed from the freezer, thawed at ambient temperature and textural analyses were conducted.The enthalpy of freezable water on fresh bread dough was determined by Differential Scanning Calorimetry (DSC) at the heating rate of 3°C/min, temperature range of −40°C to 20°C. The value of unfrozen water was 0.30–0.34 g H₂O/g solids and additives used during the storage up to 56 days significantly affected the textural properties of frozen dough.     

The effect of par‐baking and frozen storage time on the quality of cup cake

The effects of frozen storage and initial baking time of par‐baked cake on baking loss, volume, moisture, colour and textural properties of cake obtained after thawing and rebaking were investigated. Cakes, par‐baked at 175 °C for 15, 20 and 25 min, were stored at ?18 °C for 3, 6 and 9 months. After storage, par‐baked cakes were thawed and rebaked at 175 °C for 10, 15 and 20 min. Baking loss, moisture content, L and +b colour values, firmness, gumminess and chewiness of the resulting full‐baked cakes were significantly affected by both par‐baking and frozen storage time, while specific volume, cohesiveness, springiness and resilience values were significantly affected by frozen storage time. The increase in the time of frozen storage of the par‐baked cake leads to a decrease in the quality of the rebaked cake, namely an increase of baking loss and cake crumb firmness, and a loss in the moisture content and specific volume. Moisture of cake crumb, L and +b colour values, firmness, gumminess and chewiness significantly increased as the par‐baking time increased. However, regarding baking loss, specific volume, moisture content and textural properties, 3‐month intermediate storage at ?18 °C and 20‐min initial baking time gave the best result among the cakes produced by using the two‐step baking procedure.     

A comparison of the ability of several small and large deformation rheological measurements of wheat dough to predict baking behaviour

The rheological characteristics of twenty wheat flour samples obtained from four organic flour blends and a non-organic control were compared in relation to their ability to predict subsequent loaf volume in the baked bread. The flour samples considered had protein contents that varied between 11–14 g/100 g. Four different rheological methods were employed. Oscillatory stress rheometry on the protein gel extracted from the wheat flour, oscillatory stress rheometry and creep measurement on undeveloped dough samples and biaxial extensional measurements on simple flour–water doughs. None of the fundamental rheological parameters correlated with loaf volume. There was a correlation between the storage modulus of the gel protein and storage modulus for the undeveloped dough (r = 0.85). There was a weak negative correlation between protein content and biaxial extensional viscosity (r = −0.62). Stepwise multiple regression related loaf volume to dough stability time (measured on the Farinograph) and tan (phase angle) for the undeveloped dough samples (overall model r² = 0.54). The results indicate that the four rheological tests considered could not be used as predictors of subsequent loaf volume when the bread is baked.     

Effects of freezing treatments on the fermentative activity and gluten network integrity of sweet dough

The effect of freezing treatments on sweet dough was studied. The dough was frozen at ?20 °C, ?30 °C and ?40 °C in air-blast freezer cabinet and by immersion in liquid nitrogen. The yeast viability, gassing power, dough volume and dough network integrity from fresh and thawed sweet doughs were assessed. The results showed that both parameters depend on the freezing rate, which controls ice crystals size and location. Dough volume loss after freezing was attributed to reduced yeast fermentative activity and gluten network alteration in frozen dough. Fermentative activity reduced significantly in frozen dough using liquid nitrogen, causing 70% decrease on yeast population. Gluten integrity seemed to be affected by slow freezing treatment, i.e. ?20 °C and ?30 °C. Gas loss was also evaluated as a decrease of 25% ± 2 in dough volume. A correlation was observed between the freezing rate and osmotic pressure effects which influence strongly the yeast viability.     

Extending shelf life of chapatti by partial baking and frozen storage

The effect of conventional and partial baking and storage at two different temperatures (ambient and −18 °C) on the texture of wheat flour chapatties was evaluated using tensile deformation and the extent of retrogradation was studied using DSC. The extensibility of the conventionally baked chapatti decreased by 58.7% and 20.15%, respectively after storage of 24 h at ambient and frozen temperature. The partially baked chapatti showed a much lower decrease of 3.7% and 0.01% in extensibility when stored under the same conditions. Chapatties, both conventionally and partially baked stored at ambient temperature showed higher retrogradation enthalpy than their counterparts kept at −18 °C. Extended frozen storage of the chapattis from partially baked chapatti resulted in a progressive increase in the extensibility whereas the extensibility of the conventionally baked chapatties was not affected. Lowest water absorption index of 4.60 was observed in partially baked chapatti stored for 24 h at ambient temperature indicating that maximum retrogradation (4.19 J/g) had taken place. Frozen partially baked chapatties after thawing and rebaking exhibited texture equivalent to that of conventionally baked chapatties therefore they could be considered a better option than frozen conventionally baked chapatties for retarding staling.     

流态起酥油对冷冻面团烘焙特性的影响研究

使用冷冻面团生产面包具有经济、方便、快捷,产品质量稳定的特点,冷冻面团的主要缺点是:面团的醒发时间随着冷冻储存时间的延长而延长,且面包比容小.起酥油系统是提高冷冻面包面团储存稳定性的关键因素之一,流态起酥油具有良好的功能性和流动性,可以满足食品工业自动化生产的要求.研究了一种流态起酥油对冷冻面团烘焙特性的影响,结果表明在冷冻面团研究开发中使用流态起酥油可以很好地改善冷冻面团面包的烘焙特性,使得用冷冻面团制得的面包与新鲜面包在制作参数和口感上相比没有很大的区别,冷冻面团在冷冻储存期间烘焙品质的下降可以用一种专用于冷冻面团的起酥油系统来弥补.     

Effect of Lactobacillus brevis-based bioingredient and bran on microbiological,physico-chemical and textural quality of yeast-leavened bread during storage

The effects of wheat bran and of a Lactobacillus brevis-based bioingredient (LbBio), obtained after growth in flour-based medium, on quality of yeast-leavened wheat bread (WWB) were investigated. Bran was used in bread formulation by substituting a part (20 g/100 g) of white wheat flour (WBB), while LbBio was used instead of the water content (WWB + LbBio and WBB + LbBio). The use of LbBio in WWB resulted in the biological acidification of the dough due to lactic, phenyllactic and OH-phenyllactic acid contents determining a high fermentation quotient value and an improved bread texture and microbiological quality. Conversely, wheat bran reduced the specific volume and crumb hardness during storage at 25 °C, and affected the antibacterial ability of LbBio during 30 °C storage. Our findings demonstrated that LbBio counteracted the negative effects of bran and allowed to obtain an enriched fibre bread with specific volume and soft crumb comparable to bread without bran.Industrial relevanceBread is a perishable food with a short microbiological and physico-chemical shelf-life. The main microbiological alteration occurring into few days after baking is the “rope spoilage” caused by spore-forming bacteria originating from raw materials. This phenomenon, often misinterpreted as a sign of unsuccessful dough leavening and not visible from outside, is more common under industrial production conditions during the hot season causing large economic losses in the warm climates of Mediterranean countries, Africa and Australia. The use of sourdough often controls this alteration even if the industrial application of this traditional process is limited by the long leavening times. In this study, an innovative procedure for the preparation of yeast-leavened bread comprising the addition of a fermentation product from Lactobacillus brevis grown in a flour-based medium has been applied. The resulting fermentation product (LbBio bioingredient) acts as a sourdough acidifying the dough and improving the textural, physico-chemical and microbiological properties of the resulting bread. The application of bioingredient LbBio could represent an innovative strategy in industrial bread production to obtain acidified yeast-leavened products, thus, preventing the ropy spoilage and reducing the negative effects of bran addition.     

Use of applied air pressure to improve the baking properties of whey protein isolates in angel food cakes

Whey protein isolate (WPI) possesses limited application in angel food cake baking compared to liquid egg white (LEW). This study was conducted to determine whether applying air pressure in the oven during baking would improve the baking properties of WPI in angel food cakes. A special oven was designed for baking at oven air pressures up to 1.5 bar. Control angel food cakes were formulated with LEW (100/0) as its protein source and WPI-containing cakes were formulated with a mixture of 75 mL/100 mL LEW and 25 mL/100 mL WPI solution (75/25) or a mixture of 50 mL/100 mL LEW and 50 mL/100 mL WPI solution (50/50). Cakes were baked at atmospheric air pressure (AP) and at constant applied air pressure (CAP) or variable applied air pressure vs. baking time (VAP) to prevent overexpansion and collapse of WPI-containing cake batter. Cakes 75/25 and 50/50 baked at VAP exhibited improved physical, textural and sensory properties compared to those baked at AP or CAP conditions. Cakes 75/25 baked at VAP compared well with control angel food cakes baked at AP. Although 50/50 cakes baked at VAP were improved slightly over those baked at AP, none of them exhibited satisfactory properties. Therefore, additional research is needed to optimize baking conditions for cakes formulated with less than 75 mL/100 mL LEW.     

Effect of baking conditions and storage with crust on the moisture profile,local textural properties and staling kinetics of pan bread

To investigate the impact of baking conditions on staling kinetics and mechanical properties, pan breads were baked at 180 °C/34 min and 220 °C/28.6 min using a ventilated oven and metallic moulds. After baking, bread slices were stored with and without crust at 15 °C in hermetic boxes for 9 days. This investigation provides a textural and physical analysis by examining the Young's modulus, crumb density and crust/crumb ratio during storage. In order to understand the relationship between firmness and moisture content, a moisture profile and a Young's modulus profile were determined during the storage of bread. To fit the staling, a first order model was used. It was found that the kinetics were faster for samples baked with a fast heating rate than for those baked with a slow heating rate. Moreover, the staling rate of bread stored with crust was faster than for bread without crust and the outer crust area staled more rapidly than the centre of the bread slice. These results suggest that the firming of the crumb is related to moisture distribution between the crumb and crust and to the impact of local baking conditions on local firmness.     

Visible/near-infrared hyperspectral imaging prediction of textural firmness of grass carp (Ctenopharyngodon idella) as affected by frozen storage

Textural firmness is a primary determinant of consumer acceptance for evaluating freshness quality of fish fillet flesh. The objective of this study was to investigate the potential of using visible and near-infrared hyperspectral imaging (400–1000 nm) for non-destructive prediction of firmness quality of grass carp fillet as affected by frozen storage. Fillet samples were frozen at − 20 °C for 24 h and then stored at 4 °C for thawing over five days. Hyperspectral images were obtained at different thawing stages and their corresponding spectral data were extracted. Two calibration models were established between the extracted spectral data and the reference firmness values measured by the traditional mechanical method by using partial least squares regression (PLSR) and least-square support vector machine (LS-SVM) analysis. Three approaches of regression coefficients (RC) from PLSR analysis, genetic algorithm (GA) and successive projection algorithm (SPA) were utilized to recognize the most important wavelengths that possessed the greatest influence and sensitivity on the firmness prediction based upon the whole spectral range. By comparing the above-mentioned three variable selection methods, seven optimal wavelengths (450, 530, 550, 616, 720, 955 and 980 nm) were selected by GA and its corresponding simplified prediction model of GA-LS-SVM was also obtained, showing the best performance with the highest determination coefficient (R²_P) of 0.941 and the lowest root mean square error estimated by prediction (RMSEP) of 1.229. The overall results of this study suggested that hyperspectral imaging technique has a potential for fast and non-destructive prediction and analysis of textural firmness of grass carp fillets as affected by frozen storage.     

The bubble size distribution and its evolution in non-yeasted wheat flour doughs investigated by synchrotron X-ray microtomography

Determination of the bubble size distribution at the end of mixing and controlling its changes are the basis for improving bread quality before it is fully manufactured. X-rays from a synchrotron source (Biomedical Imaging and Therapy beamline, Canadian Light Source) were used to rapidly characterize the bubble size distribution and its evolution in non-yeasted dough subsamples as a function of time for 3 h following mixing. A complete X-ray microtomography scan was completed within 120 s. The higher number density of bubbles in dough compared to results previously reported in the literature was attributed to the better contrast and higher resolution (smaller pixel size, 8.75 μm) of the reconstructed X-ray images generated from synchrotron X-rays. The bubble size distribution was very well characterized with a lognormal distribution function. This distribution had a median bubble radius of 22.1 ± 0.7 μm at 36 min after the end of mixing which increased to 27.3 ± 0.7 μm over 162 min, a trend indicative of transport of gas in the dough due to disproportionation. This is the first time disproportionation in non-yeasted wheat flour doughs has been monitored directly under bulk conditions relevant to dough in bakery conditions. These results show that the diffusion-driven dynamics of bubbles in non-yeasted bread doughs can be followed by X-rays from a synchrotron source via feature extraction using image analysis software.     

Bread from composite cassava-wheat flour: I. Effect of baking time and temperature on some physical properties of bread loaf

The use of composite cassava-wheat (CCW) flour for commercial breadmaking purposes and consumption of CCW bread are relatively new in Nigeria. This study investigated the effect of baking temperature and time on some physical properties of bread from composite flour made by mixing cassava and wheat flour at ratio of 10:90 (w/w). A central composite rotatable experimental design was used while the baking temperature and time investigated ranged from 190 to 240 °C and 20 to 40 min, respectively. Loaf volume, weight and specific volume varied significantly (p < 0.001) from 440 to 920 cm³, 162 to 183 g and 3.31 to 5.32 cm³/g, respectively. The tristimulus color parameters such as L¹ (lightness) and brownness index (BI) of the crust varied significantly (p < 0.01) from 31 to 72 and 68 to 123, respectively. Moreover, Fresh crumb moisture, density, porosity and softness as well as the dried crumb hardness were also significantly (p < 0.01) affected by both the baking temperature and time with values ranging from 34% to 39%, 0.16 to 0.20 g/cm³, 0.69 to 0.80, 13.00 to 18.05 mm and 0.90 to 2.05 kgf, respectively. Due to the complex effect of temperature and time combination, most of the measured properties could not be reliably predicted from the second order response surface regression equations except the loaf weight and crumb moisture. Further studies are required to optimize the CCW bread baking process based on some storage and consumption qualities.     

Physical properties of breads containing hydrocolloids stored at low temperature: II—Effect of freezing

Bread types such as dough samples (DB), semi-baked (SB) and full-baked (FB) breads were frozen stored for a week and further baked (DB or SB). Structure stabilizers such as xanthan (X), hydroxypropylmethylcellulose (HPMC), guar gum (GG) or locust bean gum (LB) were also added to the dough. Baking stage is important for bread quality after storage; additionally hydrocolloids provide stability in many frozen foods. Fresh bread samples were prepared for comparison. Yield in baked product, dough characteristics, specific volume, porosity, textural properties of both crumb/crust, moisture content of crumb/crust and finally crust thickness and colour were measured. Data grouping was performed using PCA analysis and correlations among the properties measured were found. X and LB addition resulted in the most stable dough, since strength and dough extensibility change during storage was low. Hydrocolloid stabilizers’ (HS) influence on final bread characteristics was more pronounced in DB and SB breads. Crust moisture content was higher in SB breads, and it reached values 11–19% higher in control and galactomannan-containing breads than in DB respective samples. Bread specific volume was highly correlated to the crumb moisture content, to the crumb/crust textural characteristics and to the yield in the baked product. It was not correlated to crust moisture content and thickness. Porosity and bread colour were not correlated to any of the other properties. Bread type and HS selection are important factors for improving stability during storage.     

Impact of process conditions on the structure of pre-fermented frozen dough

The volume change of partially fermented dough exposed to refrigeration has been investigated. Lean dough pieces (70 g) were exposed to pre-fermentation at 30 °C during selected time to reach expansion ratios of 2, 3 and 4. The pre-fermented dough were exposed to cooling at 4 °C for 2 h. Dough pieces were then frozen, thawed and baked. The evolution of the volume of the dough during the different stages of the time-temperature history has been measured. Image analysis (cell distribution), of both pre-fermented dough in frozen state and baked bread obtained with these dough, were carried out and used to assess the impact of the degree of pre-fermentation on the stability of the dough and of the baked bread. Results showed that increasing the degree of pre-fermentation results in a reduction in the final dough and bread volume. Freezing applied to pre-fermented dough resulted in a baked bread with larger and less numerous gas cells. However, it was observed that applying a chilling step (4 °C for 120 min) before freezing the pre-fermented dough minimized the loss in bread volume (−40.5% vs. −27.5% in comparison to reference bread - direct baking).     

麦芽糖淀粉酶对面包品质及面团特性的影响

研究枯草芽孢杆菌来源的麦芽糖淀粉酶对面包品质及面团特性的影响,为深入了解酶制剂在烘焙产品中的作用提供理论依据。本实验主要研究了麦芽糖淀粉酶(添加量0%、0.02%、0.04%和0.06%)对面包比容、质构、贮藏期间面包保水性、质构、感官品质及面团流变学特性的影响。结果表明:面包保水性随麦芽糖淀粉酶添加量的增加而显著提高(P<0.05),而且麦芽糖淀粉酶能显著延缓面团黏度和回生值的增加(P<0.05),改善面团品质。当面包贮藏天数的增加,麦芽糖淀粉酶还能延缓面包硬度和咀嚼性的增加,减缓贮藏期面包品质下降(P<0.05)。其中,添加0.04%的麦芽糖淀粉酶能够明显延缓面包老化,对面团淀粉糊化特性影响较小。面包贮藏第7 d时,能减少水分损失36.92%,保持面包弹性。因此,麦芽糖淀粉酶能够延缓面包老化和面包品质下降。     

Effect of Amino Acids and Peptides on Mixing and Frozen Dough Properties of Wheat Flour

Free amino acids, peptides, and vital wheat gluten were investigated to determine their effect on the mixing and frozen dough baking properties of wheat flour. Addition of 1% cysteine and aspartic acid decreased and glutamic acid, histidine, arginine, and lysine increased the mixing tolerance of flour. Cystine, methionine, tryptophan, and phenylalanine increased but isoleucine, histidine, glycine, arginine, glutamic acid, aspartic acid, and lysine decreased loaf volume of nonfrozen dough breads. However cystine, methionine, tryptophan, and phenylalanine did not increase loaf volume of bread prepared from frozen dough. Vital wheat gluten increased mixing tolerance and bread loaf volume only for the nonfrozen dough. However, wheat gluten hydrolysate, corn, and bonito peptides decreased mixing tolerance after optimum mixing time and were effective in increasing loaf volume for both frozen and nonfrozen dough. As the amount of corn and bonito peptide increased, specific loaf volumes also increased. Addition of 2.5% corn peptide was most effective in increasing loaf volume of frozen dough bread. Crust browning and crumb stickiness increased, whereas crumb softness decreased with addition of peptides. Addition of less than 1% peptide did not adversely affect the aftertaste and off‐flavor of bread. These results suggest that addition of peptides are effective for improving the baking quality of frozen dough, whereas amino acids and gluten have no effect.     

Water vapor transport properties during staling of bread crumb and crust as affected by heating rate

In order to develop a mathematical model to simulate mass transfer occurring between the crumb and the crust during bread staling, water vapor sorption properties, i.e., moisture diffusivity, WVP and sorption of bread crumb and crust were investigated at 15 °C. Two types of bread baked with two heating rates (7.39 °C/min and 6.32 °C/min) were considered. Sorption and desorption isotherms were determined using Dynamic Vapor Sorption (DVS) and FF and GAB models were applied in the range of 0–0.95 a_w, to fit isotherm curves. Diffusivity was determined from sorption isotherms by using Fick's law and WVP was measured by two methods (gravimetric and from sorption data). Results exhibited maximum values of D_eff in the range of 0.1 and 0.14 g/g d.b. moisture contents. They varied between 0.88 × 10^? 10 and 0.92 × 10^? 10 m²/s for the crust and between 2.24 × 10^? 10 and 2.64 × 10^? 10 m²/s for the crumb, baked respectively at 220 °C and 240 °C. Results of WVP showed that the crust baked at 240 °C was significantly more permeable than the crust baked at 220 °C. This fact was attributed to the difference in porosity and the molecular structure due to heating effects. Also, the presence of steam in the oven atmosphere enhanced the development of higher porosity in the crust, leading to different structures and properties. Moreover, SEM images showed that starch granules were intact and less swelled in the upper crust when baking at 240 °C, resulting in higher WVP.     

Influence of frozen storage and packaging on oxidative stability and texture of bread produced by different processes

The influence of packaging barrier properties and frozen storage on phenolic and phytosterol content, oxidative stability and crumb texture of frozen dough, part-baked and fully baked frozen bread was investigated in comparison to conventionally produced bread. Samples were stored either in blue coloured high density polyethylene (PE-HD) or transparent polyester-polyethylene-ethylene-vinyl alcohol copolymer (PET-PE/EVAL/PE) pouches for 22 days at −18 °C. Packaging materials were different in oxygen permeability: 3.67 cm³m⁻²day⁻¹ bar⁻¹ for PET-PE/EVAL/PE and 2080 cm³m⁻²day⁻¹ bar⁻¹ for PE-HD material, which did not significantly change during storage. Total phenolic content and oxidative stability of bread samples decreased during storage depending on the process. Frozen dough bread had the lowest phenolics decrease and the highest oxidative stability. Total phenolic content and oxidative stability of frozen breads during 8 days were similar to conventional bread. The phenolics reduction was higher for samples stored in PET-PE/EVAL/PE laminate than in PE-HD packaging. Total sterol content did not significantly change during bread storage in investigated packaging and did not contribute to the oxidation. Bread firmness was affected only by the process and not by the storage time and packaging material.     

Effect of Honey as Partial Sugar Substitute on Pasting Properties,Consumer Preference and Shelf Stability of Cassava-Wheat Composite Bread

The effect of partial substitution of sugar with liquid honey on the pasting properties of cooked dough made from cassava-wheat composite (10:90) flour as well as the sensory preference and shelf stability of its bread was investigated. Sucrose (S) in the bread recipe formulation was substituted with honey (H) at levels 0, 10, 20, 30, 40 and 50%, respectively to give 6 treatments, namely 0H:100S, 10H:90S, 20H:80S, 30H:70S, 40H:60S and 50H:50S. Amylograph pasting properties of the dried crumbs were determined using standard analytical procedures. Fresh bread samples were subjected to sensory evaluation and fungal count during storage (6 days). Peak, final and setback viscosities of bread crumb decreased (32.29 to 25.33, 58.54 to 43.00 and 30.96 to 23.66 RVU), respectively as the level of honey inclusion increased. Honey substitution levels used did not significantly (p > 0.05) affect aroma and texture of the bread samples but composite bread with 20% level of honey substitution was most preferred in terms of colour while composite bread with 30% level of honey substitution was most acceptable in terms of taste and overall acceptability. Fungal count in stored honey-cassava-wheat bread varied significantly (p < 0.05) from 0.6 to 4.0 × 10², 1.0 to 6.9 × 10², 2.2 to 57.0 × 10², 32.0 to 135.7 × 10², 34.0 to 140.0 × 10² and 42.0 to 159.3 × 10²) cfu/ml from day 1 to day 6, respectively. From the study, it was concluded that substitution of sugar with honey in dough formulations significantly (p < 0.05) affects dough pasting properties, improves acceptability of the composite bread and reduces staling rate.     

Fibre-rich additives--the effect on staling and their function in free-standing and pan-baked bread

BACKGROUND: The use of dietary fibre in bread products is increasing because of consumer demand for healthier products. However, an increase in dietary fibre level changes the rheological properties of the dough and also the quality properties of the final bread product. In this study, effects on dough and bread staling were followed after replacing 3% of wheat flour by fibre‐rich additives (fine durum, oat bran, rye bran and wheat bran). Free‐standing and pan‐baked loaves were baked to compare the influence of baking method and loaf shape. RESULTS: All additives increased dough stability, with oat bran giving the greatest stability and longest development time. Parameters measured during storage were distribution, migration and loss of water, cutability, crumbliness, firmness and springiness. Furthermore, amylopectin retrogradation and amylase‐lipid complex formation were assessed. Oat bran provided similar or better results than the control for all staling parameters, while other additives gave no general improvements. Cutability reached a plateau when crumb firmness was ≥ 4 N. CONCLUSION: Small amounts of fibre‐rich additives had a significant influence on staling. However, the baking method (free‐standing or pan‐baked bread) had a greater impact on staling than the additives, thus displaying the importance of the baking method. Cutability was found to be related to firmness. Copyright © 2011 Society of Chemical Industry