A study of the baking process by differential scanning calorimetry

The denaturation of the components of a baked product such as cake or bread can be observed under simulated baking conditions by differential scanning calorimetry. When starch or protein denaturation occurs, an increased flow of heat shows the temperature range over which that process takes place. Experimental results are presented for angel cake. In the absence of sucrose, the egg-white proteins are denatured predominantly near 65 and 85°C. For wheat flour, starch denaturation is observed near 65°C, and protein denaturation over a broad range from 80 to 110°C. In the presence of the concentration of sucrose used in a standard batter, both the starch and the major portion of the egg-white proteins are denatured near 95°C, at approximately the maximum temperature attained by the cake when it reaches maximum volume in the oven. Apparently, the main function of sucrose in an angel cake is to raise the denaturation temperature ranges of the starch and protein. Decreasing the amount of sucrose in batters designed for high altitudes causes denaturation of starch and protein at the lower maximum temperatures attained at those altitudes. This assures formation of a structural framework of denatured starch and protein which will not allow the cake to “fall” after it attains its maximum volume.     

Effects of sucrose on egg white protein and whey protein isolate foams: Factors determining properties of wet and dry foams (cakes)

The effects of sucrose on the physical properties of foams (foam overrun and drainage ½ life), air/water interfaces (interfacial dilational elastic modulus and interfacial pressure) and angel food cakes (cake volume and cake structure) of egg white protein (EWP) and whey protein isolate (WPI) was investigated for solutions containing 10% (w/v) protein. Increasing sucrose concentration (0–63.6 g/100 mL) gradually increased solution viscosity and decreased foam overrun. Two negative linear relationships were established between foam overrun and solution viscosity on a log–log scale for EWP and WPI respectively; while the foam overrun of EWP decreased in a faster rate than WPI with increasing solution viscosity (altered by sucrose). Addition of sucrose enhanced the interfacial dilational elastic modulus (E′) of EWP but reduced E′ of WPI, possibly due to different interfacial pressures. The foam drainage ½ life was proportionally correlated to the bulk phase viscosity and the interfacial elasticity regardless of protein type, suggesting that the foam destabilization changes can be slowed by a viscous continuous phase and elastic interfaces. Incorporation of sucrose altered the volume of angel food cakes prepared from WPI foams but showed no improvement on the coarse structure. In conclusion, sucrose can modify bulk phase viscosity and interfacial rheology and therefore improve the stability of wet foams. However, the poor stability of whey proteins in the conversion from a wet to a dry foam (angel food cake) cannot be changed with addition of sucrose.     

鸡蛋蛋黄的功能及其制品

鸡蛋富含营养价值高的蛋白质，脂质，也是维生素和矿物质的良好来源，特别是其中的蛋白质人体吸收率达99．7％，且必需氨基酸十分丰富。鸡蛋不仅是个营养宝库，而且作为快餐食品，糕点和面包的食品原料，蛋白与蛋黄的热凝笥，蛋白的起泡性，蛋黄的乳化性等特性在食品工业上也得到普遍的应用。     

Rheological studies of high ratio cake batters to investigate the mechanism of improvement of flours by chlorination or heat treatment

The rheological changes taking place in cake batters between 70 and 90°C have been studied using chlorinated, heat-treated (120°C for 7 min) and untreated flours. It was shown that, in an aqueous sucrose solution of equivalent concentration to that found in cake batters, the untreated flour forms a weaker gel system than the treated flours. This difference was probably due to the slower and less extensive swelling of the starch granules. Egg proteins were shown to contribute significantly to the overall gel strength of the cake matrix. The effect of the egg proteins was significantly greater with the treated flours than with the untreated flours.     

Wheat batter physical properties as influenced by starch/flour types and egg contents

Batter liquid–solid phase interactions can play a critical role in determining the functionality, including adherence, appearance and texture of end use coated product. Batter chemical composition is a key factor affecting batter characteristics. The effect of substituting wheat flour with fractions of rice flour, native corn starch, modified waxy corn starch, tapioca starch and lupine flour ranging from 26 to 56% of the solid phase and egg levels ranging from 6 to 35% of the liquid phase on the rheological properties of batter systems was studied. Results indicated that lupine flour had the greatest water holding capacity (WHC) ranging from 93.9 to 119.3% of various lupine flour percent to egg levels used. Flow behaviour index of batter flour treatments ranged from 0.91 to 1.87; values that were significantly (P?<?0.05) greater than a 100% control wheat flour. Consistency coefficient of treatments ranged from 0.01 to 0.37 mPa sⁿ; values that were significantly lower than wheat flour (i.e., 5 mPa sⁿ). Egg level used in this study had minimal effect on treatment rheological properties. The changes in WHC and viscoelastic properties of treatments were attributed to changes in protein and fibre contents and structure as a result of replacing wheat flour with starch/flour. Protein–starch–lipid matrix formation and variation in water absorption kinetics of treatments most probably wrought batter functionality. The increase in pasting properties with the increase in starch/flour contribution suggested an increased contribution of starch in forming a net effect of batter treatments pasting viscosities. Results of this study provide vital information for the potential use of starch types to enhance the rheological properties of coating applications including adhesion and water holding capacity of substituted batter treatment.     

Dielectric properties of microwave-baked cake and its constituents over a frequency range of 0.915–2.450 GHz

There is a large market for microwave foods, with one of the most prevalent growth areas being low-density bakery products. The dielectric constant and loss factor of Madeira cake batter and its constituents (sugar, cake concentrate, margarine, flour, egg) were measured at a range of moisture contents (0.429–1.000 kg kg⁻¹, dry basis), temperatures (20–80 °C), and over a frequency range of 915–2450 MHz. In general, for a given material, the dielectric properties of samples increased with increasing frequency. Irrespective of frequency and sample moisture content, the dielectric constant of batter and flour was relatively independent of sample temperature, whereas that of the sugar samples increased with increasing temperature, particularly within the lower moisture range. At 2450 MHz the loss factor of batter and flour samples decreased by a limited amount as temperature was increased, whereas at 915 MHz they were relatively unaffected. The sugar samples showed a significant decrease in loss factor with increasing temperature, irrespective of frequency. During microwave baking, the dielectric properties of Madeira cake batter initially increased sharply and then decreased steadily until the end of the baking process.     

Effects of sucrose and sodium chloride on foaming properties of egg white proteins

Egg white proteins are extensively utilised in the food industry as foaming agents. A number of factors, singly or in combination, can affect the foaming characteristics of egg albumen. In this study, egg white protein solutions heated at various temperatures in the presence of variable concentrations of sucrose and NaCl were whipped for different periods of time. All factors had a significant impact on the foaming properties of egg albumen. Increasing NaCl content and whipping time enhanced protein adsorption at the air–water interface. The presence of sucrose delayed foam formation but contributed to the stability of the aerated system. Controlled denaturation of the protein solutions induced by mild heat treatment enhanced the foaming properties of egg white proteins. This data indicates that the foaming properties of egg white proteins can be manipulated by altering the effect of extrinsic factors in order to achieve optimal formulations for food industrial applications.     

Foams Prepared from Whey Protein Isolate and Egg White Protein: 2. Changes Associated with Angel Food Cake Functionality

ABSTRACT:  The effects of sucrose on the physical properties and thermal stability of foams prepared from 10% (w/v) protein solutions of whey protein isolate (WPI), egg white protein (EWP), and their combinations (WPI/EWP) were investigated in wet foams and angel food cakes. Incorporation of 12.8 (w/v) sucrose increased EWP foam stability (drainage 1/2 life) but had little effect on the stability of WPI and WPI/EWP foams. Increased stability was not due to viscosity alone. Sucrose increased interfacial elasticity ( E  ') of EWP and decreased E' of WPI and WPI/EWP combinations, suggesting that altered interfacial properties increased stability in EWP foams. Although 25% WPI/75% EWP cakes had similar volumes as EWP cakes, cakes containing WPI had larger air cells. Changes during heating showed that EWP foams had network formation starting at 45 °C, which was not observed in WPI and WPI/EWP foams. Moreover, in batters, which are foams with additional sugar and flour, a stable foam network was observed from 25 to 85 °C for batters made from EWP foams. Batters containing WPI or WPI/EWP mixtures showed signs of destabilization starting at 25 °C. These results show that sucrose greatly improved the stability of wet EWP foams and that EWP foams form network structures that remain stable during heating. In contrast, sucrose had minimal effects on stability of WPI and WPI/EWP wet foams, and batters containing these foams showed destabilization prior to heating. Therefore, destabilization processes occurring in the wet foams and during baking account for differences in angel food cake quality.     

Development and evaluation of products from cassava flour as new alternatives to wheaten breads

Egg white with margarine, and xanthan gum, have been used to produce alternative breads from cassava flour fortified with 200 g kg^?1 soya flour. All the additives increased the amount of air entrapped in the cassava batters at the mixing stage, as indicated by their lower batter densities. The lower the batter density the higher was the maximum gas retention volume attained in the 60 min fermentation stage. However, final loaf volume also depends on the stability of the batter; egg white primarily acts as a stabiliser. Margarine, and more significantly egg white, reduced the extent of starch gelatinisation and solubilisation in the bread. Breads made with locally available egg white and margarine are sensorily acceptable to Nigerian consumers and have very good keeping qualities.     

Effect of batter freezing conditions and resting time on cake quality

The aim of the present study was to investigate the effects of batter freezing and conditions and resting time before baking on quality of two kinds of cakes (layer and sponge cakes), including freezing temperature (−18 °C, −26 °C), storage time at sub-zero temperatures (30 and 100 days), and resting time (60 and 120 min). Characteristics of the batter (pH, density, viscosity, and microstructure) and cakes (density, texture, and colour) were analysed. Freezing process increases batter density and viscosity, and consequently decreases cake volume and height, but increases hardness. Cakes from frozen batters have a darker and more yellow crumb and lighter-coloured crust than cakes from non-frozen batters. Freezing process has a greater effect on batter and cake quality characteristics than storage/freezing conditions or resting time. In layer cakes, freezing mainly affected volume and colour, whilst in sponge cakes, there was a more marked effect on texture. Differences between the two kinds of cake could be related to a distinct internal structure. Resting time mainly affected batter characteristics, although there were no apparent differences in the quality of the cakes obtained.     

Factors determining the physical properties of protein foams

Protein foams are an integral component of many foods such as meringue, nougat and angel food cake. With all these applications, the protein foam must first obtain the desired level of air phase volume (foamability), and then maintain stability when subjected to a variety of processes including mixing, cutting and heating. Therefore, factors determining foamability and stability to mechanical and thermal processing are important to proper food applications of protein foams. We have investigated the effects of protein type, protein modification and co-solutes on overrun, stability and yield stress. The level of overrun generated by different proteins was: whey protein isolate hydrolysates >whey protein isolate=β-lactoglobulin=egg white>α-lactalbumin. The level of yield stress generated by different proteins was: egg white>whey protein isolate hydrolysates≥β-lactoglobulin>whey protein isolate>α-lactalbumin. Factors that decreased surface charge (pH∼pI or high ionic strength) caused a more rapid adsorption of protein at the air–water interface, generally increased dilatational viscoelasticity and increased foam yield stress. The elastic component of the dilatational modulus of the air–water interface was correlated with foam yield stress. The properties of foams did not predict performance in making angel food cakes. A model for foam performance in angel food cakes is proposed.     

A model approach to starch and protein functionality in a pound cake system

Different modified wheat starches were used in a model pound cake recipe. The properties of the starches were linked to differences in batter viscosity, cake height and protein extractability during baking, collapse during cooling and final cake quality. The impact of incorporation of 30% cross-linked (CL) starches on batter properties during baking was much smaller than that of incorporation of the same level of hydroxypropylated (HP) starches. Incorporation of HP starches with various degrees of modification in the recipe caused batter viscosity during baking to start rising from 92 or 88 °C rather than at 96 °C and diminished oven rise significantly. Furthermore, the extractability of the protein in cakes containing HP starch was significantly higher. During cooling, control cake collapsed less than did CL starch-containing cake, which itself collapsed significantly less than did HP starch-containing cake. Presumably, most of the cake collapse takes place before the starch gel is formed during cooling. Protein and starch apparently function in determining cake quality, by providing the cell walls with structural material and high resistance to collapse. Starch does not prevent cake collapse, but still co-determines crumb structure, whereas a strong correlation was found between the gel-forming capacity of starch blends and intrinsic crumb firmness (r = 0.99). Furthermore, a strong negative correlation was found between springiness and percentage of extractable protein in final cakes (r = −0.95). We conclude that the combination of a protein network, formed during baking, with a starch gel, formed during cooling, makes up the crumb cell walls and determines cake quality.     

The effect of short term storage on the albumen quality of shell eggs

Certain physical changes occur naturally in the albumen of shell eggs when stored under cool conditions which cause the thick white to become thin. The whipping characteristics of the albumen are changed during this process but the functional performance of the albumen as measured by the angel food cake method is not affected to any marked degree. Three 10-day storage trials were undertaken using day-old shell eggs which demonstrated that a significant loss of albumen performance did not occur until the storage temperature reached 18 ºC. This conclusion clearly indicates the importance of maintaining shell eggs under cool conditions between collection at the farm and commercial distribution by the egg floors, particularly during the summer season.     

Effect of ascorbic acid on the foaming and gelling of globular proteins

Foam expansion and foam stability of plasma and egg albumen proteins were enhanced in the presence of increasing concentrations of ascorbic acid (0.1–1.0%). BSA showed the greatest improvement in foaming properties following treatment with ascorbic acid, whilst foaming properties of egg albumen were improved to a limited extent. A combination of partial acid hydrolysis and treatment with 1% ascorbic acid was required to dramatically improve the foaming properties of bovine blood plasma. In the presence of sucrose, foam expansion of both native and ascorbic acid-treated blood plasma was decreased. In contrast the foam expansion of ascorbic acid-treated egg albumen was greater although this effect decreased slightly on incubation. the gelation of ascorbic acid treated proteins increased with increasing temperatures over 80–90°C, particularly for BSA and blood plasma, and with increasing concentrations of ascorbic acid. Ascorbic acid-treated proteins exhibited enhanced surface and exposed hydrophobicity and reduced numbers of sulphydryl groups indicating the involvement of these factors in foam and gel formation.     

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.     

Structural development of sucrose‐sweetened and sucrose‐free sponge cakes during baking

The influence of sucrose, wheat starch and sorbitol upon the heat‐ and mass‐exchanging processes forming the structure of sponge cake was studied. Under the influence of wheat starch and sorbitol the structure of the sucrose‐free sponge cake was formed at more uniform total moisture release. This process was done at lower temperatures and smoother change of the sponge cake height with respect to the sucrose‐sweetened sponge cake. The porous and steady structure of both cakes was finally formed at identical time – between 18^th and 19^th minute, at the applied conditions for baking of each batter (metal pan with diameter 15.4 cm and depth 6.2 cm containing 300 g of batter and placed in an electric oven “Rahovetz – 02”, Bulgaria for 30 min at 180°C). The water‐losses at the end of baking (10.30% and 10.40% for the sucrose‐sweetened cake and sucrose‐free cake, respectively) and the final temperatures reached in the crumb central layers (96.6°C and 96.3°C for the sucrose‐sweetened cake and sucrose‐free cake, respectively) during baking of both samples were not statistically different. The addition of wheat starch and sorbitol in sucrose‐free sponge cake lead to the statistically different values for the porosity (76.15% and 72.98%) and the volume (1014.17 cm³ and 984.25 cm³) of the sucrose‐sweetened and sucrose‐free sponge cakes, respectively. As a result, the sucrose‐free sponge cake formed during baking had a more homogeneous and finer microstructure with respect to that of the sucrose‐sweetened one.     

Alkaline extraction of starch from Australian lentil cultivars Matilda and Digger optimised for starch yield and starch and protein quality

The Australian lentils, Lens culinaris: Matilda (Green Lentil) and Digger (Red Lentil) contain 44–45% starch (HPLC method) and 30–33% protein (LECO Analyser). This paper describes, first, the identification of optimum starch extraction conditions where yield is high and starch and protein damage is acceptable and, second, the properties of the starch and protein recovered. Starch was extracted from the flour of each variety with water at four temperatures (ambient 22, 30, 35 and 40 °C) and at five pH conditions (distilled water and pH adjusted with NaOH to 8, 8.5, 9.0 and 9.5). Extraction at pH 9.5, for all temperatures, achieved the maximum starch yield (85–95%) for both varieties. Digger gave a lower starch yield than Matilda when extracted in distilled water at all four temperatures. The yields of Digger starch were not significantly different at the four alkaline pHs. Matilda flour showed gradual increase in % starch yield with increase in extraction temperatures and pH (significant to 95% confidence level). Protein yield achieved, from both Digger and Matilda flour, was relatively low: 43–60% of the analysed protein content for Digger and 48–63% for Matilda. No significant difference was observed for extracted Digger protein at the various extraction pHs and temperatures. Matilda protein yields were significantly different between the various extraction conditions. The % starch damage was high for both varieties when extracted at higher temperature and pH. The DSC ΔH value increased with increasing pH and temperature. Extraction at higher pH resulted in a smoother and more symmetrical peak, denoting the absence of protein adhering to the starch surface. Even though low pH and low temperature caused less starch damage, these conditions were undesirable because they resulted in lower starch and protein yields. Taking all factors into account, pH 9.0 at 30 °C was chosen as an optimum extraction condition for Matilda while pH 8.5 at 35 °C was chosen for Digger.     

Egg Albumen Proteins Interactions in an Angel Food Cake System

The foaming properties of six albumen proteins were tested singly and in combinations in an angel food cake system. Physicochemical characteristics and foamability of the protein solutions and volume of cakes were determined. Solutions containing only globulins had good foaming properties and produced a large cake with excellent texture. Solutions of ovalbumin incorporated air after a long whip time and produced a large, coarse textured cake. Ovomucin, lysozyme, ovomucoid, and conalbumin had little or no foaming capacity. Association of ovomucin with globulins favored foam formation; however, cake volume was drastically reduced. Lysozyme, by complexing with ovomucin, depressed foaminess of the protein solutions but considerably larger cakes were produced. Lack of heat coagulative properties of the protein film was primarily responsible for low cake volumes.     

Effect of Shell Eggs Storage on Ovomucin Extraction

Ovomucin, one of the major egg white proteins, has wide potential applications in food, functional food and nutraceutical industries due to its unique physicochemical properties and bioactivities. A new two-step method was recently developed to prepare high purity ovomucin; in this study, effect of shell egg storage on ovomucin extraction was investigated. The composition of ovomucin extracts from egg white was determined by gel filtration chromatography. Both storage temperature and time could significantly (p < 0.05) affect the purity and yield of the ovomucin. After 9 weeks of storage at 4 °C, the content of the ovomucin in the extract decreased from 92.5% to 82.4%, and the yield of ovomucin decreased from 214 to 120 mg/100 g of egg albumen (egg white). After 5 weeks of storage at 22 °C, the content of ovomucin extract decreased from 92.5% to 73.0%, and the yield of ovomucin decreased from 214 to 112 mg/100 g of egg albumen. Increase in egg white pH during prolonged storage leading to degradation of ovomucin is very likely responsible for the decreased extractability of ovomucin.     

Effect of Whey Protein Concentrate on the Rheological and Baking Properties of Eggless Cake

Effect of substitution of wheat flour with whey protein concentrate (WPC) at the level of 10, 20, and 30% as an egg replacer and its influence on physical properties of cake batter and quality characteristics of eggless cake were studied. The apparent viscosity of the eggless cake batter decreased with the increase in the level of WPC. The evaluation of eggless cake batter for density showed that incorporation of WPC decreased the batter density. The photomicrographs of eggless cake batters with WPC showed an increase in number of air cells and even distribution when compared with the control indicating lighter batter. Eggless cake with 20% WPC was rated the best.