Effect of Moisture Content on Viscoelastic Properties of Hydrated Gliadin

The effect of moisture content on the linear viscoelastic properties of gliadin hydrated to 30 and 40% moisture content [gliadin(30%) and gliadin(40%), respectively] was determined. These two moisture contents bracketed the equilibrium moisture content of gliadin, which was 37.6%. Time‐temperature‐superposition was used to develop master curves of the elastic modulus (G′), viscous modulus (G″), dynamic viscosity (η′), and tan δ (G″/G′) from isothermal frequency sweep data obtained at 25–80°C. Smooth master curves were obtained for all of the viscoelastic functions for both gliadins. G′ and G″ showed a power law dependency on frequency (with G″ > G′) for frequencies <0.1 rad/sec for gliadin(30%) and <1 rad/sec for gliadin(40%). The low‐frequency‐limiting slopes on log‐log coordinates for G′ and G″ were 0.700 and 0.646 for gliadin(30%), respectively. Corresponding values were 0.658 and 0.614 for gliadin(40%). G′ crossed over G″ at a frequency of ≈0.3 rad/sec for gliadin(30%), while G′ and G″ for gliadin(40%) only became congruent at higher frequencies. Both gliadin samples showed appreciable frequency dependence of η′ over the entire frequency range, while η′ was greater for gliadin(30%) than for gliadin(40%) at all frequencies, but especially at the lowest frequencies. Tan δ increased gradually from a value of ≈1 at 0.1 rad/sec to ≈2 at the lowest frequency of 0.0002 rad/sec for both gliadins, but tan δ decreased rapidly for gliadin(30%) for frequencies >0.1 rad/sec. Thus, the main difference between gliadin(30%) and gliadin(40%) was that elastic effects (G′ > G″ and decreased tan δ were more prominent for gliadin(30%) at the higher frequencies. In addition, the frequency dependence of G′, G″, η′, and tan δ for the two gliadin samples was compared directly with two samples of poly(dimethylsiloxane) (PDMS) a linear silicone‐based entangled polymer with molecular weights (MW) of 140,000 and 385,000. The substantial differences in the magnitude and overall patterns of the frequency dependence of the viscoelastic functions between the gliadin and PDMS samples was attributed to the dominant effect that noncovalent secondary associations apparently have on the linear viscoelasticity of the gliadins. The energy of activation for flow (determined from the temperature dependence of the shift factors) for the gliadin samples for the range 25–45°C was higher than is typical for entangled linear polymer melts. The activation energy decreased for temperatures greater than ≈60°C for gliadin(30%) and ≈50°C for gliadin(40%). Thus, hydrated gliadin cannot be considered to be a simple viscoelastic liquid.     

Effects of Salt and Alkaline Reagents on Dynamic Rheological Properties of Raw Oriental Wheat Noodles

To gain further understanding of the functionality of ingredients in oriental wheat noodles, the rheological properties of raw noodles made using high protein (Red Bicycle) or low protein (Sandow) wheat flours and various additives (salt or alkaline reagents at concentrations of 0, 0.1, 0.5, 1.0, 2.0, 3.0, and 4.0%) were investigated using frequency sweep and temperature sweep oscillatory tests. Generally, both the elastic modulus(G′) and viscous modulus (G″) of raw noodles increased when various levels of salt or alkaline (kansui and NaOH) reagents were included in the formulation, with the exception of Red Bicycle noodles where the G″ was not significantly affected by the salt. The G′was significantly decreased in the presence of sodium chloride at concentrations ≤4.0% and kansui at <0.5%. The change in rheological properties of raw noodles was related to the wheat flour quality, type, level of additive, and frequency. The G′, G″, phase angle, and complex viscosity changed in a similar pattern when raw noodles were heated from 25 to 100°C. These parameters decreased initially with increasing temperature until they reached a valley and then increased either to a plateau or continuously in noodles containing kansui. The appearance of valley points at 75.5 and 77.2°C during heating of Sandow and Red Bicycle noodles containing salt, and 89.4, and 83.2°C during heating of Sandow and Red Bicycle noodles containing kansui, respectively, was not associated with starch gelatinization as determined using differential scanning calorimetry. The continuous increase in G′, G″, and complex viscosity observed with noodles containing kansui during the hold period at 100°C was attributed to the high pH environment and not to the inactivation of α‐amylase.     

Influences of Baking and Thawing Conditions on Quality of Par‐Baked French Bread

We examined the effects of baking time and temperature for the preparation of par‐baked French bread, and of thawing and second baking conditions on the characteristics of bread prepared from par‐baked bread. Par‐baked French bread with loaf volume and crumb structure comparable to fully baked bread (control) was obtained with ≥6 min baking at 218°C, which increased the crumb temperature to 97°C. Freezing, thawing, and second baking of par‐baked bread decreased loaf volume by ≥100 mL. The second baking time of par‐baked bread, which was adjusted to have the bread crumb subjected to 97°C for 14 min based on the crumb temperature profile, produced a darker crust of bread compared with the control. The par‐baked bread with 6 min of initial baking at 218°C and frozen at ‐30°C required 12 min of second baking after thawing for 180 min to ≈20°C to produce crust color, crumb moisture, and firmness comparable to that of the control. When thawing time of par‐baked bread was shortened from 180 to 0 min, the second baking time required to yield crust color similar to the control increased from 12 to 16 min. The crumb moisture content was higher in bread baked for 16 min without thawing par‐baked bread than those baked after thawing for 45 or 180 min. Lowering the initial baking temperature of par‐baked bread from 246 to 163°C with the adjustment of baking time from 4 to 12 min decreased crumb firmness of the re‐baked (218°C, 16 min) bread from 2.5 to 1.5 N at 2 hr after baking and from 9.8–10.3 to 6.2–6.3 N at 48 hr.     

Amylose and Amylopectin Interact in Retrogradation of Dispersed High-Amylose Starches

Retrogradation of three high-amylose starches (HAS: ae du, ae V, and ae VII) and common corn starch (CCS) was examined by dynamic oscillatory rheometry (7.5% [w/w] starch in 20% [v/v] dimethyl sulfoxide [DMSO]), differential scanning calorimetry (DSC; 30% [w/w] starch in water), and turbidity (0.5% [w/w] starch in 20% [v/v] DMSO). Nongranular lipid-free starch and starch fractions (amylose [AM], amylopectin [AP], and intermediate material [IM]) were studied. Gels were prepared by dispersing starches or fractions in 90% DMSO and diluting with water, followed by storage for seven days at 4°C. For AM from each starch, the elastic modulus (G′) was similar when heated from 6 to 70°C. The G′ of HAS AP gels at 6°C was higher than for CCS AP gels. For nongranular CCS and ae du gels, G′ dropped dramatically (≈100×) when heated from 6 to 70°C, less (≈10×) for ae V gels, and least (≈5×) for ae VII gels. By DSC, each AM endotherm had a peak temperature of ≈140°C, whereas all AP endotherms were complete before 120°C. Endotherms >120°C were not observed for any nongranular starch despite the high AM content of some starches. After cooling starch suspensions from room temperature to 5°C and subsequent rewarming to room temperature, each AM and the ae VII nongranular starch remained highly turbid. Each AP and the remaining nongranular starches lost turbidity during rewarming. Our work suggests that branched molecules of CCS and HAS influence gel properties of nongranular starches by inhibiting or altering AM-AM interactions.     

Glucose Oxidase in Breadmaking Systems

The mechanism of glucose oxidase action in breadmaking was investigated by studying the baking performance of glucose oxidase, the active ingredient that it produced, and its effect on the rheological properties of dough. Glucose oxidase improved the loaf volume of bread made by 45-, 70-, and 90-min fermentation processes. Although the increase in loaf volume was significant, it was less than that obtained with an optimum level of KBrO₃. With the 90-min fermentation process, the crumb grain of bread was similar for loaves oxidized with optimum levels of glucose oxidase or KBrO₃. The rheological properties of doughs containing glucose oxidase and doughs containing no oxidant were compared. Doughs made with glucose oxidase had higher G′ and G″ and lower tan δ values than doughs made without an oxidant. Hydrogen peroxide was responsible for a drying effect in doughs. This drying effect of glucose oxidase was reduced significantly by incorporation of free radical scavengers into the dough.     

Relationships Between Gluten Rheological Properties and Hearth Loaf Characteristics

The rheological properties of fresh gluten in small amplitude oscillation in shear (SAOS) and creep recovery after short application of stress was related to the hearth breadbaking performance of wheat flours using the multivariate statistics partial least squares (PLS) regression. The picture was completed by dough mixing and extensional properties, flour protein size distribution determined by SE‐HPLC, and high molecular weight glutenin subunit (HMW‐GS) composition. The sample set comprised 20 wheat cultivars grown at two different levels of nitrogen fertilizer in one location. Flours yielding stiffer and more elastic glutens, with higher elastic and viscous moduli (G′ and G″) and lower tan δ values in SAOS, gave doughs that were better able to retain their shape during proving and baking, resulting in breads of high form ratios. Creep recovery measurements after short application of stress showed that glutens from flours of good breadmaking quality had high relative elastic recovery. The nitrogen fertilizer level affected the protein size distribution by an increase in monomeric proteins (gliadins), which gave glutens of higher tan δ and flatter bread loaves (lower form ratio).     

Rheological and Thermal Properties of Aged Starch Pastes from Three Waxy Maize Genotypes

The rheological and thermal properties of aged starch gels (15:85 starch-water) from three waxy maize genotypes (wx, wx sh1, and du wx) during storage (4°C for up to 25 days) were studied. After storage, changes of storage modulus (G′) and phase angle (δ) of the gels as a function of temperature were measured using oscillatory rheometry. For the du wx samples, G′ at 25°C increased rapidly during the first four days of storage at 4°C, compared to the gradual increases over the 25-day storage period for the wx and wx sh1 samples. A peak in G′ at 45°C was observed during heating for the du wx samples after 10 days of storage and for the wx sample stored for 25 days. The G′ peak may have been due to syneresis in the gels. Retrogradation of amylopectin of the aged starch samples was examined using differential scanning calorimetry. The du wx starch had greater retrogradation enthalpies than the other two samples (which showed similar retrogradation behavior) throughout the storage. The retrogradation enthalpy of the du wx samples increased rapidly during the first seven days, followed by a slower increase through the rest of storage. For the wx and wx sh1 samples, no endotherm was observed during the first four days of storage, after which the enthalpy increased steadily as a function of storage time. Addition of sucrose delayed the formation of gel networks for all three starches. The greater tendency for gelling and retrogradation of the du wx starch might be attributed to the greater proportion of DP20–30 chains of the amylopectin.     

Neutral Lipids in Free,Bound, and Starch Lipid Extracts of Flours,Sourdough, and Portuguese Sourdough Bread Determined by NP‐HPLC‐ELSD

A detailed analysis was developed, focused on the neutral lipids (NL) in free (FL), bound (BL), and starch lipid (SL) extracts of maize and rye flours, sourdough, and broa (a traditional bread manufactured in Portugal). Selective sequential extraction of said lipids with hexane at 20°C, water‐saturated n‐butanol at 20°C, and n‐propanol‐water (3:1, v/v) at 100°C was performed to clean the lipid extracts from extraneous impurities, and isolation thereof from glyco‐ and phospholipids was by solid phase extraction of NL; these classes were then quantitatively assayed by HPLC, using evaporative light scattering detection, with calibration curves prepared with standard mixtures of NL. The BL and SL contents in the original flours increased and that of FL decreased throughout the fermentation and baking processes. The dominant NL class was not the same in all lipid extracts; the highest concentrations of triacylglycerols and the lowest concentrations of free fatty acids were detected in FL—with the former accounting for 82, 76, and 71% of the total FL in flours, sourdough, and bread, respectively. Triacylglycerols and free fatty acids also accounted for the highest concentrations found in BL: these, together with diacylglycerols, contributed up to 84% of the total neutral BL. High levels of free fatty acids and low levels of the remaining NL classes were typically found in SL: free fatty acids, triacylglycerols, sterol esters, and diacylglycerols accounted for ≈90% of the total SL.     

Extensional Rheology and Stability of Gas Cell Walls in Bread Doughs at Elevated Temperatures in Relation to Breadmaking Performance

The rheological properties of gas cell walls in bread doughs are considered to be important in relation to their stability and gas retention during proof and baking. Large deformation rheological properties of gas cell walls were measured using biaxial extension for a number of doughs of varying breadmaking quality at constant strain rate and elevated temperatures of 25–60°C. Strain hardening and failure strain of cell walls both decreased with temperature, with cell walls in good breadmaking doughs remaining stable and retaining their strain hardening properties at higher temperatures (60°C), while the cell walls of poor breadmaking doughs became unstable at lower temperatures (45–50°C) and had lower strain hardening. Strain hardening measured at 50°C gave good correlations with baking volume, with the best correlations achieved between rheological measurements and baking tests that used similar mixing conditions. As predicted by the Considere failure criterion, a strain hardening value of 1 defines a region below which gas cell walls become unstable, and discriminates well between the baking quality of a range of commercial flour blends of varying quality. This indicates that the stability of gas cell walls during baking is strongly related to strain hardening properties, and that extensional rheological measurements can be used as indicators of baking quality.     

Oat Bran Fermentation by Rye Sourdough

Hydration of oat bran including fermentation by rye sourdough was studied. Three types of oat bran suspensions were prepared (a control, one with whole meal rye flour added, and one with rye starter added). The suspensions were incubated for 1, 2, 3 and 4 hr. β‐Glucan content and solubilities of protein and β‐glucan were analyzed. Viscosity of the supernatants of oat bran suspensions was determined. Neither the rye sourdough nor the rye flour alone had a significant effect on the total β‐glucan content of oat bran suspensions. However, the addition of rye, either as whole meal rye flour or as sourdough starter, markedly increased the solubility of β‐glucan and proteins and simultaneously decreased the viscosity of the water‐soluble fraction of oat bran suspension. This suggests that a hydrolysis of β‐glucan had occurred that could change the rheological properties of oat bran in baking and the physiological potential of oat bran in nutrition.     

Thermal Expansion of Flour-Water Dough Measured with a Dynamic Mechanical Analyzer

Thermal expansion of a wheat flour-water dough was measured with a dynamic mechanical analyzer (DMA) at a temperature scan range of 25 to 160°C, in 5°C/min increments. Dough water-absorption levels were increased from 50 to 70% (14% mb) in 4% increments. A standard breadbaking method was used, and loaf volume was measured for regression analysis. The thermal expansion pattern of flour-water dough during heating included four stages with changes in the thermal expansion coefficient: gas thermal expansion (GTE) (25–60°C), starch gelatinization-gluten matrix formation (GMF) (60–100°C), vapor pressure expansion (VPE) (100–120°C), and structure fixation-crust formation (SCF) (>120°C). The onset temperature (T_o) between each stage and the thermal expansion coefficient (C_e) of each stage were affected significantly by dough water content. The onset temperature () from GTE to GMF (the starting temperature of gelatinization of starch in dough) decreased from 68 to 55°C as water absorption increased from 50 to 70%. The thermal expansion coefficient () of flour-water dough during GMF was highly correlated (r² = 0.886) to bread loaf volume. The ratio () of thermal expansion coefficient during the GMF stage to the coefficient during the GTE stage also was significantly correlated (r² = 0.882) to baking volume. Thus, DMA measurement of dough thermal expansion has the potential to be a powerful method of predicting baking quality in cultivar screenings, baking simulations, and scale-up studies.     

Effect of Baking Method and Fermentation on Folate Content of Rye and Wheat Breads

The effect of baking method on folates of rye and wheat breads, as well as the effect of sourdough fermentation of rye, were examined. Sourdough fermentations were performed both with and without added yeast, and samples were taken throughout the baking process. Samples were analyzed microbiologically for their total folate content after trienzyme extraction. Individual folate vitamers were determined by HPLC after affinity chromatographic purification. The lowest folate contents for both rye and wheat breads were found from breads baked without added yeast. Total folate content increased considerably during sourdough fermentation due to increased amounts of 10‐HCO‐H₂folate, 5‐CH₃‐H₄folate, and 5‐HCO‐H₄folate. Baker's yeast contributed markedly to the final folate content of bread by synthesizing folates during fermentation. Proofing did not influence total folate content but changes in vitamer distribution were observed. Folate losses in baking were ≈25%. The variety of sourdoughs and baking processes obviously lead to great variation in folate content of rye breads. The possibilities to enhance natural folate content of rye bread by improving folate retention in technological processes and by screening and combining suitable yeasts and lactic acid bacteria should be further investigated.     

Effect of Sucrose on Glass Transition,Gelatinization, and Retrogradation of Wheat Starch

Differential scanning calorimetry (DSC) was used to study the effect of sucrose on wheat starch glass transition, gelatinization, and retrogradation. As the ratio of sucrose to starch increased from 0.25:1 to 1:1, the glass transition temperature (T_g, T_g′) and ice melting enthalpy (ΔH_ice) of wheat starch‐sucrose mixtures (with total moistures of 40–60%) were decreased to a range of −7 to −20°C and increased to a range of 29.4 to 413.4 J/g of starch, respectively, in comparison with wheat starch with no sucrose. The T_g′ of the wheat starch‐sucrose mixtures was sensitive to the amount of added sucrose, and detection was possible only under conditions of excess total moisture of >40%. The peak temperature (T_m) and enthalpy value (ΔH_G) for gelatinization of starch‐sucrose systems within the total moisture range of 40–60% were increased with increasing sucrose and were greater at lower total moisture levels. The T_g′ of the starch‐sucrose system increased during storage. In particular, the significant shift in T_g′ ranged between 15 and 18°C for a 1:1 starch‐sucrose system (total moisture 50%) after one week of storage at various temperatures (4, 32, and 40°C). At 40% total moisture, samples with sucrose stored at 4, 32, and 40°C for four weeks had higher retrogradation enthalpy (ΔH) values than a sample with no sucrose. At 50 and 60% total moisture, there were small increases in ΔH values at storage temperature of 4°C, whereas recrystallization of samples with sucrose stored at 32 and 40°C decreased. The peak temperature (T_p), peak width (δT), and enthalpy (ΔH) for the retrogradation endotherm of wheat starch‐sucrose systems (1:0.25, 1:0.5, and 1:1) at the same total moisture and storage temperature showed notable differences with the ratio of added sucrose. In addition, T_p increased at the higher storage temperature, while δT increased at the lower storage temperature. This suggests that the recrystallization of the wheat starch‐sucrose system at various storage temperatures can be interpreted in terms of δT and T_p.     

Comparison of Small and Large Deformation Measurements of Whole Meal Rye Doughs

The rheological properties of rye flour-water-salt doughs prepared from different flour types (different falling number and coarseness) at different water levels were studied after mixing and after 90 min of incubation (30°C and 80% rh). Both the effect of water and the coarseness of the flour had significant effects on storage modulus (G′) measured by oscillatory test in the linear viscoelastic region and on compressional force measured at large deformation. The results of the two rheological methods correlated very well with each other (correlation coefficients varied in the different doughs at r = 0.975–0.999). Dough rheological measurements suggested that falling number did not have a statistically significant effect on dough rheology after mixing or incubation. Although the two rheological methods correlated well, the responses for incubation were different. In the small deformation method, the storage modulus of all doughs, independent of the falling number, decreased during incubation, whereas in the large deformation method, only the hardness of doughs made from flours with lower falling number decreased during incubation. The rheological measurements of doughs after mixing and the viscosity measurements of flourwater suspension at 30 and 40°C did not correlate with each other. Total pentosans have great effect on viscosity measurements of flour-water suspensions, whereas flour particle size and soluble pentosans correlated more with rheological properties of doughs (r = 0.851 between G′ and soluble pentosans).     

Volatile Compounds in Crumb of Whole‐Meal Wheat Bread Fermented with Different Yeast Levels and Fermentation Temperatures

The influence of fermentation temperatures (8, 16, and 32°C) and yeast levels (2, 4, and 6%) on the formation of volatile compounds in the crumb of whole‐meal wheat bread was investigated. Volatile compounds were extracted by dynamic headspace extraction and analyzed by gas chromatography–mass spectrometry. Results were evaluated with multivariate data analysis and ANOVA. Bread fermented at a high temperature (32°C) had higher peak areas of the Maillard reaction products 2‐furancarboxaldehyde, 2‐acetylfuran, 2‐methylpyrazine, and phenylacetaldehyde compared with bread fermented at lower fermentation temperatures. Bread fermented at low temperatures (8 and 16°C) was characterized by having higher peak areas of the fermentation products 3‐methylbutanal, 2‐methylbutanal, ethyl acetate, ethyl hexanoate, ethyl propanoate, and 3‐methylbutanol. Fermentation of bread with 6% yeast resulted in a higher peak area of the important fermentation product 2‐phenylethanol. It also reduced the peak areas of important lipid oxidation products. The peak area of 2,3‐butanedione was also relatively higher in bread fermented with 6% yeast compared with lower yeast levels; however, an interaction was seen between the high yeast level and all three fermentation temperatures. In contrast, fermentation with a low yeast level (2%) resulted in bread with relatively higher peak areas of 2‐ and 3‐methylbutanal, as well as (E)‐2‐nonenal and (E,E)‐2,4‐decadienal, which are important lipid oxidation compounds in bread.     

Centrifuged Liquid and Breadmaking Properties of Frozen‐and‐Thawed Bread Dough

Breadmaking properties (bread height, mm, and specific volume, cm³/g ) showed marked deterioration when bread dough was frozen and stored at ‐20°C for one day. However, these properties of bread dough baked after storage for three to six days were not further deteriorated as compared with that baked after one day of storage. A large amount of liquid was oozed from the frozen‐and‐thawed bread dough. The liquid was separated from the bread dough by centrifugation (38,900 × g for 120 min at 4°C), and collected by tilting the centrifuge tube at an angle of 45° for 30 min. There was a strong correlation between the amount of centrifuged liquid and breadmaking properties (bread height and specific volume). The mechanism responsible for the oozing of liquid in frozen‐and‐ thawed bread dough was studied. The presence of yeast and salt in bread dough was suggested to be closely related to the amount of centrifuged liquid, and fermented products particularly had a large effect on the amount of centrifuged liquid.     

Factors influencing acrylamide content and color in rye crisp bread

An industrial baking procedure for yeast-leavened whole-grain rye crisp bread was adapted to local laboratory conditions to study the effect of time and temperature of baking and the addition of fructose, asparagine, and oat-bran concentrate on the acrylamide content and color of the bread. Baking time and temperature affected acrylamide content that increased from 10 to 30 mug/kg of bread at the combination of a long time and high temperature, with a significant interaction between the two factors (p < 0.008). Added asparagine had a significant effect (p < 0.001) on the formation of acrylamide, but fructose did not. There was a correlation between acrylamide content and color of the milled bread in the time-temperature experiment, but this correlation was not observed in the experiment with added precursors. Added oat-bran concentrate with high content of mixed-linkage beta-glucan did not influence the acrylamide content in the breads.     

Hearth Bread Characteristics: Effect of Protein Quality,Protein Content,Whole Meal Flour,DATEM, Proving Time,and Their Interactions

The effects of protein quality, protein content, ingredients, and baking process of flour blends on hearth loaves were studied. The flour blends varied in protein composition and content. Flours of strong protein quality produced hearth loaves with larger loaf volume, larger bread slice area, and higher form ratio (height/width) than flours of weak protein quality. The effect of protein content on hearth loaf depended on the size distribution of the proteins. Increasing protein content was associated with increased percentage of the largest glutenin polymers, and loaf volume and slice area increased significantly. The form ratio, however, remained unchanged with increasing flour protein content. Strong protein quality flours tolerated addition of whole meal flour better than weak protein quality flours. Increased amount of flour with strong protein quality improved hearth bread characteristics to a larger extent than increased protein content. Diacetyl tartaric acid ester of monoglycerides (DATEM) improved hearth bread characteristics, but the effect was small compared with the effect of protein composition.     

Differential Scanning Calorimetry Glass Transition Temperatures of White Bread and Mold Growth in the Putative Glassy State

Differential scanning calorimetry (DSC) was used to determine the onset and end temperatures of the glass transition (T_g) for white bread equilibrated between 53 and 84% rh. Calorimetric T_g end values were ≈20°C higher than onset values, indicating that it is probably more correct to refer to a “glass transition range” rather than a glass transition temperature. Slices of white bread inoculated with a mixture of xerophilic molds were equilibrated to 75% rh (equilibrium moisture content of 14.5 g of water/100 g of dry material) and stored at 26°C. In a parallel experiment, some of the equilibrated bread samples were stored without mold inoculation and subjected to spontaneous contamination from the immediate surroundings. As suggested by measured T_g, bread stored at 75% rh and 26°C appeared to be glassy. After storage, samples of bread (inoculated or not) were spoiled by xerophilic molds, suggesting that T_g, as measured by DSC, cannot be considered as an absolute threshold for mold growth inhibition.     

Effects of Baking Temperature on Crumb-Staling Kinetics

This study evaluated the effects of bread baking temperature on the staling kinetics of crumb. Bread dough was leavened and baked in sealed molds. Cooking trials were performed at various temperatures ranging from 90 to 110°C. The crumb samples were then stored at 20°C at constant moisture, and staling was evaluated by measuring crumb elastic modulus (using an Instron dynamometer) and starch retrogradation degree (using differential scanning calorimetry). Results show that the cooking temperature greatly influences bread staling. The lower the cooking temperature, the lower the staling rate, both in terms of crumb hardening and of starch retrogradation. Starch and protein solubility was evaluated on crumb cooked at 90 and 110°C. An increase in cooking temperature resulted in an increase in protein insolubilization and starch granule disruption.