Changes in the Physicochemical Properties of Wheat- and Soy

Further reproduction prohibited without permission

Food Engineering and Physical Properties

JFS:Food Engineering and Physical Properties

Changes in the Physicochemical Properties of

Wheat- and Soy-containing Breads During

Storage as Studied by Thermal Analyses

E. VITTADINI AND Y. VODOVOTZ

ABSTRACT: Adding soy ingredients to baked products influences textural and sensorial properties. The changes in

physical properties of bread modified with soy flour during 7-d storage at ambient temperature were investigated

using thermoanalytical techniques (differential scanning calorimetry and dynamic mechanical analysis). An in-

crease in loaf density, moisture content, and FW content, and a decrease in amylopectin recrystallization were

observed with increased addition of soy flour. Addition of soy shifted the main thermal transition (0 °C, mainly due

to ice melting) to slightly lower temperatures (both in differential scanning calorimetry and dynamic mechanical

analysis analysis) and decreased its temperature range (increased homogeneity). These observations suggest a role

for soy in modulating bread staling.

Keywords: bread staling, soy bread, DSC, DMA, freezable water

Introduction

OY IS A POPULAR COMPONENT OF THE ASIAN DIET AND MORE

recently has found increasing acceptance in Western diets due

to the Food and Drug Administration claim of linking the con-

sumption of soy protein with a lower risk of heart disease (FDA 1999).

Additionally, soy products are being recognized as having potential

roles in the prevention and treatment of chronic diseases, most

notably cancer (Fukutake and others 1996; Appelt and Reicks

1999), osteoporosis, and kidney disease (Omi and others 1994;

Draper and others 1997), and reduction of blood cholesterol levels

(FDA 1999).

Soy has been successfully incorporated in various products in-

cluding chicken-meat analogs, cereals, pasta, and imitation bacon

bites, but its use in bakery products (especially bread) has been

limited because of unacceptable sensory and textural properties.

The effects of adding soy ingredients to bread have been charac-

terized by sensory analysis (Buck and others 1987; Dhingra and

Jood 2001), nutritional parameters (Dhingra and Jood 2001), loaf

volume, density measurements (Erdman and others 1977; Fleming

and Sosulski 1977; Buck and others 1987; Brewer and others 1992),

and texture analysis (Buck and others 1987; Brewer and others

1992). Notably, a significant decrease in loaf volume was observed

with the addition of soy (Erdman and others 1977; Fleming and

Sosulski 1977; Buck and others 1987; Brewer and others 1992),

which was correlated to a change in the water absorption of the soy

ingredients (Chen and Rasper 1982; Doxastakis and others 2002)

and/or dilution of the gluten fraction (Knorr and Betschart 1978).

The changes (especially firming) occurring in breads during stor-

age have been attributed to several factors including recrystalliza-

tion of amylopectin (Maga 1975; Kulp and others 1981), moisture

redistribution (Leung and others 1983; Baik and Chinachoti 2001),

changes in gluten functionality (Maga 1975; Kulp and others 1981),

and the state of the amorphous phase (Slade and Levine 1991; Hall-

berg and Chinachoti 1992). Hallberg and Chinachoti (2002) have

shown that starch recrystallization may contribute to staling but

that other indicators such as moisture migration and changes in the

amorphous phase are more likely to be the cause of bread firming.

Additionally, the role of gluten in staling has come into question

because breads made with alternative proteins (soy and milk) in-

creased in firmness during storage at the same rate (Gerrard and

others 2001) as traditional breads containing gluten proteins.

When changing a processing and/or preservation method, it is

critical to understand the resulting changes to the physicochemi-

cal and molecular properties of the food material to ensure an ac-

ceptable product. These properties are the tangible manifestation

of changes that take place in the product at both structural and

molecular levels. Thermal analysis techniques such as differential

scanning calorimetry (DSC) and dynamic mechanical analysis

(DMA) have been shown to be particularly well suited for such

characterization.

Differential scanning calorimetry monitors changes in physical

or chemical properties of a material as a function of temperature by

detecting the heat changes associated with such processes. Phase

transitions such as starch gelatinization, amylopectin recrystalliza-

tion, amylose-lipid complex formation, and FW have all been quan-

tified in various carbohydrate systems (Russell 1983; Levine and

Slade 1988; Vodovotz and Chinachoti 1998). Such phase transitions

proved important in wheat bread storage studies, identifying an

increase in crystalline amylopectin and decrease in FW with increas-

ing storage time (Vodovotz and others 1996).

Dynamic mechanical analysis has been introduced to study

thermomechanical changes in food (MacInnes and Roulet 1988;

Roulet and others 1988; Kalichevsky and others 1992; Vodovotz and

others 1996; Vodovotz and Chinachoti 1998). Dynamic mechanical

analysis is a thermoanalytical technique that applies a dynamic

stress at a given frequency to a sample of known geometry. The

resulting strain has 2 components: in phase (elastic, E9) and out of

phase (viscous, E0; Wendlandt and Gallagher 1981). Food polymers

are mostly viscoelastic with stress and strain being out of phase with

respect to each other by a phase angle (d). Tan d is defined as the

ratio of E0/E9. E0 is the loss modulus that reflects the energy dissi-

pated as the material is deformed, and E9 is the storage modulus

that indicates the storage of energy (Murayama 1978; Hamann and

others 1990). Dynamic mechanical analysis has proven to be a pow-

17503841, 2003, 6, Downloaded from https://ift.onlinelibrary.wiley.com/doi/10.1111/j.1365-2621.2003.tb07012.x by Ohio State University Ohio Sta, Wiley Online Library on [27/01/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License

Vol. 68, Nr. 6, 2003

—

JOURNAL OF FOOD SCIENCE 2023

Food Engineering and Physical Properties

JFS

is available in searchable form at

www.ift.org

Soy bread staling by thermal analyses . . .

erful tool for distinguishing between the effects of drying and ag-

ing on the thermomechanical properties of bread (Hallberg and

Chinachoti 1992; Chinachoti 1994; Vodovotz and others 1996). The

tan d (T) curves for aged and fresh bread of similar moisture con-

tents were very different in the transition temperature range, that

is, the curve for aged bread was found to be broader (Vodovotz and

others 1996). The storage modulus (E9) transition region for various

bakery products was fitted using a model equation (based on Fer-

mi’s distribution function; Peleg 1993; Vodovotz and others 2000).

Differences in the firmness among the samples were quantified

using this method (Vodovotz and others 2000). More detailed dis-

cussion on application of this technique to bread staling analysis

can be found in Hallberg and Chinachoti (1992).

The objective of this study was to investigate the effect of soy

flour on the physicochemical properties of soy bread as compared

with a wheat control by using DSC and DMA techniques.

Materials and Methods

Bread production

Formulations shown in Table 1 were used to produce 0.9-kg

bread loaves. Breads loaves were produced with an automated

bread machine (Zojirushi America Corp., Commerce, Calif., U.S.A.)

and allowed to cool on racks at room temperature for 1 h before anal-

ysis or packaged into polyethylene bags for storage at room tem-

perature. Bagged breads loaves were kept at 25 °C for up to 7 d.

Bread loaves were analyzed at predetermined time intervals (0, 1,

2, 4, and 7 d postproduction). Two to five breads loaves were pro-

duced for each bread formulation.

Water-holding capacity

Water-holding capacity for the different flour mixtures (0%, 20%,

30%, and 40% substitution of soy flour for the wheat flour) was ob-

tained according to the method of Quin and Paton (1983). Five

grams of the flour mixtures were weighed into a 50-mL centrifuge

tube to which 30 mL water was added. The slurry was stirred for 5

min and then allowed to stand for 30 min at ambient conditions.

The flour mixture was then centrifuged at 4500 rpm for 25 min and

the weight of free liquid measured. The retained weight was ex-

pressed as the amount of water absorbed per gram of sample on dry

basis.

Moisture content determination

Moisture content of bread was determined by vacuum oven dry-

ing (AOAC 2002, Method 925.09). Duplicates of preweighed samples

were placed over silica gel overnight and then vacuum oven–dried at

60 °C for 24 h. The final weight of each sample was determined and

moisture content calculated from weight loss (Eq. 1):

(1)

Loaf volume

Loaf volume was determined by rapeseed replacement (AACC

2000, Method 10-05).

Differential scanning calorimetry

Differential scanning calorimetry curves were obtained with a

DSC 2920 cell of TA Instruments (New Castle, Del., U.S.A.) purged

with nitrogen gas. Bread samples (10 to 15 mg) were placed in her-

metically sealed aluminum pans (PerkinElmer Instruments LLC,

Shelton, Conn., U.S.A.) quench cooled inside the DSC furnace

equipped with a refrigerated cooling system and then heated at 5 °C/

min from –50 °C to 110 °C. At least triplicate samples were analyzed

for each bread loaf at a given time. The following parameters were

obtained from the DSC thermogram (Vodovotz and others 1996):

“Freezable” water (FW). Presence of an endothermic melting

peak around 0 °C corresponded to ice melting (Reid and others

1993), and the enthalpy of this transition was used to calculate FW

using Eq. 2.

(2)

“Unfreezable” water (UFW ). Calculated from the difference

between % moisture content and % FW.

Recrystallized amylopectin. The melting peak at around 60 °C

was assumed to correspond to recrystallized amylopectin (Russell

1983). The enthalpy of this peak was measured (W/g) using Ad-

vantage Software (TA Instruments).

Dynamic mechanical analysis

Bread crumb (approximately 1-cm thick) was compressed with a

Carver press at room temperature to approximately 3-mm thick-

ness and cut with a die into the appropriate sample shape

(3 × 10 × 18 mm). A sample was then inserted into a dual cantilever

attachment of a DMA instrument (DMA 2980, TA Instruments) in

the float mode and locked down with thumbscrews. The sample was

cooled to –80 °C in the oven of the DMA using liquid nitrogen be-

fore heating at 2 °C/min up to 120 °C in the bending mode. Stor-

age modulus (E9), loss modulus (E0), and tan d (E9/E0) were record-

ed (Vodovotz and others 1996). The storage modulus was further

characterized by fitting the curve with a modified Fermi equation,

(Peleg 1993), Eq. 3:

(3)

where E

is the normalized E9, a is the slope of the line, b is a con-

stant, T is the temperature, and Tc is the temperature at the inflec-

tion point of the curve.

Results and Discussion

Bread macroscopic properties

Cooked and cooled control wheat bread was found to weigh

about 800 g and to have a loaf volume of 2820 cm

. The density of

the bread loaves was calculated for each product to account for the

differences in formulation (Table 1) and are presented in Figure 1.

Table 1—Breads’ formulation expressed as % total

Wheat Soy 20% Soy 30% Soy 40%

Wheat flour 55.8% 43.4% 38.0% 31.7%

Defatted soy flour 0% 10.9% 16.3% 21.7%

Water 34.9% 37.7% 37.7% 37.7%

Sugar 4.6% 4.0% 4.0% 4.0%

Shortenings 2.6% 2.1% 2.1% 2.1%

Dry yeast 1.1% 0.9% 0.9% 0.9%

Salt 1.0% 1.0% 1.0% 1.0%

2024 JOURNAL OF FOOD SCIENCE—Vol. 68, Nr. 6, 2003

Food Engineering and Physical Properties

JFS

is available in searchable form at

www.ift.org

Soy bread staling by thermal analyses . . .

Density of the bread loaves increased with an increase in soy flour

addition. These findings are consistent with prior work comparing

the loaf volume of soy and wheat breads (Sosulski and Fleming

1979; Klein and others 1980; Buck and others 1987). The density

increase was speculated to be caused by greater water absorption

of the soy ingredients (Doxastakis and others 2002) and lower glu-

ten content of soy added breads (Gerard and others 2001) with

consequent reduction of gluten network formation resulting in lower

loaf volume (Knorr and Betschart 1978). Higher bread density (de-

creased specific loaf volume) has been correlated to a more pro-

nounced firmness during storage (Axford and others1968).

Moisture content and FW

Moisture content of the wheat (control) bread crumb during stor-

age at room temperature was measured and decreased as expected

(Baik and Chinachoti 2001), from 38.5% to 34.2% during 7 d of stor-

age (Figure 2). The changes in moisture content were confirmed by

thermogravimetry on the same samples (data not shown).

The reduction of moisture content in the bread crumb has been

attributed to moisture migration from the wetter bread crumb to

the drier bread crust (Baik and Chinachoti 2001). The crumb of

fresh soy-containing bread had similar moisture content as the

wheat control (Table 2). The moisture content of soy-containing

bread was also found to decrease during storage but to a lesser

degree than the wheat control (Figure 2). The reduction in % mois-

ture content was proportional to the amount of soy added to the

formulation (that is, 4.2%, 3.1%, 2.5%, and 1.7% moisture decrease

in 0%, 20%, 30%, and 40% soy bread, respectively, over 7 d of stor-

age; Figure 2). It can be speculated that a larger amount of water

held in the bread matrix in the presence of soy (increased water-

holding capacity, Table 2) is strongly associated with the bread com-

ponents and therefore not easily removed by vacuum oven–dry-

ing. Similarly, in previous studies, addition of soy increased the

water-holding capacity of standard bread formulations (Fleming

and Sosulski 1977; Porter and Skarra 1999; Doxastakis and others

2002).

Differential scanning calorimetry curves indicated the presence

of a major endothermic transition about 0 °C that was attributed

mainly to ice melting (Li and others 1996; Vodovotz and others 1996;

Baik and Chinachoti 2001). Typical curves for the ice-melting tran-

sition in fresh wheat bread and 40% soy bread are shown in Figure

3, insert A, and indicate that the transition developed over a similar

Table 2—Effect of soy addition on water absorption of flour,

moisture content, and % “unfreezable” water in fresh

bread

Moisture “Unfreezable”

Water-holding content water

capacity of flour of fresh bread of fresh bread

% Soy (%) (%) (%)

0 77.0 6 0.5 38.4 6 0.2 15.2 6 0.3

20 88.6 6 1.0 38.9 6 0.5 15.4 6 0.5

30 98.8 6 0.7 36.9 6 0.4 12.6 6 0.5

40 112.8 6 1.2 37.6 6 0.5 12.6 6 0.3

Figure 1—Density of bread loaves as function of soy flour

content

Figure 2—Percent moisture content change in bread crumb

containing different amounts of soy flour during storage

at room temperature for 7 d

Figure 3—“Freezable” water (differential scanning calorim-

etry [DSC] analysis) of bread crumb containing different

amounts of soy flour during storage at room temperature.

Typical DSC thermograms emphasizing the endothermic

transition approximately 0 °C for wheat bread (solid line)

and 40% soy bread (dotted line) at day 0 are shown in in-

sert A.

Vol. 68, Nr. 6, 2003

—

JOURNAL OF FOOD SCIENCE 2025

Food Engineering and Physical Properties

JFS

is available in searchable form at

www.ift.org

Soy bread staling by thermal analyses . . .

temperature range. Temperature onset of the transition was slightly

lower in the soy-containing breads (Table 3). The overall transition

was more skewed to lower temperatures in the soy-containing

breads (Figure 3, insert A), suggesting the existence of a possible

second transition in these samples. As reported earlier, such tran-

sition may be tentatively attributed to a glass transition (Tg) occur-

ring at temperatures slightly lower than the ice-melting transition

or to the melting of ice crystals in freeze-concentrated domains

(Zeleznak and Hoseney 1987; Levine and Slade 1988; Roos and

Karel 1991; Li and others 1996; Vodovotz and others 1996; Baik and

others 1997a, 1997b; Baik and Chinachoti 2001).

“Freezable” water (as analyzed by DSC analysis) of bread crumb

during storage at room temperature is shown in Figure 3. Fresh

wheat control bread was found to have slightly lower FW content

(23.2% 6 0.2%) than soy-containing bread. Addition of soy flour to

the bread formulation caused a slight increase in FW content in the

bread in proportion to the amount of soy substitution (that is,

23.5 6 0.5%, 24.3% 6 0.6%, and 25.0% 6 0.1% in the 20%, 30%, and

40% soy, respectively). The higher moisture content in the soy-con-

taining products may account for the slightly greater amount of FW.

FW decreased with increasing storage time in all samples as pre-

viously reported for white bread (Baik and Chinachoti 2000, 2001).

Wheat control bread showed a greater reduction (5.1%) in FW during

7 d of storage than in soy-containing bread (2.0% to 3.8%), suggest-

ing higher stability of the latter. The % UFW content also was calcu-

lated (Table 2) and did not seem to reflect the greater water-hold-

ing capacity of the soy/wheat flour mixtures (Table 2). Additionally,

the UFW content did not change significantly during storage, sug-

gesting that only the more available water (the FW) may have un-

dergone detectable changes during storage. This is consistent with

the measured decrease in moisture content in the bread crumb dur-

ing storage (Figure 1). These results differ from those of Hallberg

and Chinachoti (2002) who found the UFW content of standard

white bread increasing with storage. The discrepancy is probably

due to the lengthy storage time (0 to 17 mo) used in that study.

Amylopectin recrystallization

The endotherm of amylopectin recrystallization (endothermic

peak at approximately 40 to 70 °C in the DSC curve; Figure 4, insert

A) was found to increase in all samples during storage. The en-

thalpy associated to amylopectin recrystallization in the control

wheat bread increased from 0.6 to 3.8 W/g during 7 d of storage, and

it was similar to previous findings (Longton and LeGrys 1981; Rou-

let and others 1988). The increase in amylopectin recrystallization

was significantly decreased by the presence of soy flour in the

bread formulation (Figure 4). The lower amount of amylopectin

initially present in the soy-containing breads cannot alone explain

the significantly lower extent of the amylopectin recrystallization.

For example, a 40% amylopectin reduction is expected in the 40%

soy-containing bread, and it should lead to a 40% reduction in the

enthalpy of recrystallized amylopectin melting. This was not ob-

served in the experimental results (Figure 4). At 2 d of storage, for

example, the enthalpy of the recrystallized amylopectin peak (40%

soy sample) should be 1.5 W/g (40% reduction from 2.5 W/g of the

wheat control), whereas only 0.6 W/g are measured by DSC.

Baik and Chinachoti (2001) had previously suggested a correla-

tion between lower amylopectin recrystallization and lower mois-

ture gradient between bread crumb and crust. Also in the present

study, a lower moisture loss in soy-containing bread crumb was

observed during storage (Figure 2), suggesting a different moisture

redistribution during storage in the soy-containing bread. Zeleznak

and Hoseney (1987) reported that starch crystallinity is controlled

by the water present during retrogradation with maximum crystal

formation at moisture contents of 40% to 50%. It is thus possible

that the high affinity of soy components for water (higher water-

holding capacity; Table 2) resulted in less water available for the

starch component, decreasing the recrystallization rate during stor-

age. Alternately, Ryan and others (2002) proposed that hydrated

soy fractions in bread interacted strongly with starch, thus interfer-

ing with the ability of the soy protein to form complexes with the

gluten fraction. According to these authors, therefore, the soy pro-

tein/starch interactions precluded starch/starch interactions,

thereby hindering amylopectin recrystallization during storage.

Dynamic mechanical analyzer results

A typical DMA curve for wheat bread is show in Figure 5. A major

transition was observed at 0 °C as indicated by the drop in E9 and

E0 values and a peak in the tan d curve. As previously reported, this

transition was attributed mainly to ice melting, but may have con-

tributions from a second-order transition such as glass transition

(Hallberg and Chinachoti 1992; Vodovotz and Chinachoti 1996). At

temperatures above 100 °C, moisture evaporated from the sample,

resulting in cracking and hardening of the sample (jagged lines)

and increase in E9.

Tan d (T) curves observed in this study did not show significant

differences during storage, possibly due to the relatively short stor-

age time. The reported changes in the tan d (T) line shape

Table 3—On-set and max peak T of differential scanning

calorimetry (DSC) ice-melting peak in wheat control and

soy-enriched breads

Onset T Peak T

Control –13.5 6 1.2 –4.7 6 1.6

Soy 20% –15.2 6 1.8 –4.6 6 1.5

Soy 30% –14.6 6 2.5 –4.7 6 1.5

Soy 40% –15.2 6 1.0 –5.1 6 1.2

The values are the average of all DSC results over 7 d of storage 6 standard

deviation.

Figure 4—Recrystallized amylopectin melting of bread

crumb containing different amounts of soy flour during

storage at room temperature. Typical differential scanning

calorimetry thermograms emphasizing the endothermic

transition approximately 60 °C for wheat bread (solid line)

and 40% soy bread (dotted line) at day 7 of storage are

shown in insert A

2026 JOURNAL OF FOOD SCIENCE—Vol. 68, Nr. 6, 2003

Food Engineering and Physical Properties

JFS

is available in searchable form at

www.ift.org

Soy bread staling by thermal analyses . . .

(Vodovotz and others 2000) in wheat bread were significant and

measurable only after 12 d of storage.

Figure 6 shows the change in stiffness (or E9 [T] values) at 25 °C

for wheat and 40% soy bread during storage. E9 (T) for wheat bread

was found to be slightly higher (stiffer) than in soy-containing

bread during storage. Stiffness in breads as measured by compres-

sion tests has been inversely correlated to an increase in loaf spe-

cific volume (Axford and others 1968) and lower moisture content

(Rogers and others 1988). However, as mentioned previously, the

soy-containing breads had a greater density (lower loaf specific

volume) and similar initial moisture content compared with the

wheat bread, yet resulted in lower initial stiffness detected by

DMA. During storage, the moisture content of the wheat bread

decreased to a greater extent than the soy-containing bread and

therefore may, at least partially, account for the greater stiffness

observed for the wheat bread (Baik and Chinachoti 2001). It is also

important to point out that E9 (T) is measuring segmental mobili-

ty, which is an indication of stiffness on a molecular level and,

therefore, the greater amount of water retained in the soy-contain-

ing bread may act as plasticizer of macromolecules, resulting in a

lower molecular stiffness. Density is a function of the arrangement

of the different components (protein, carbohydrate, air, water, and

so on) in the sample that may not correlate with molecular stiffness

but only with macroscopic stiffness (texture analysis).

E9 (T) DMA data were further characterized by fitting the storage

modulus curves in the transition region with a modified Fermi

equation, as previously reported (Peleg 1993; Vodovotz and others

2000). This equation describes the change in stiffness (E9) with

temperature within a range of storage times. In all cases, the fitting

gave an r

$ 0.98. Fitting results of wheat and soy-containing bread

during storage are shown in Table 4. The fitted parameters Tc and

a did not significantly change over time (Table 4), and their aver-

aged values over 7 d of storage will be used in this discussion. Tc,

the temperature at the inflection point in the curve, decreased with

the addition of soy to the bread formulation, indicating a shift of

the transition region to lower temperatures, as also suggested by

DSC results. This lower transition temperature may reflect the

greater ability of water to plasticize soy-containing bread compo-

nents. The steepness or the slope of the curve, a, was found to be

greatest for the wheat bread reflecting a more gradual drop in E9

(T) that may be due to greater heterogeneity of this sample as com-

pared with the soy added formulations. The presence of glycerol, a

plasticizer, decreased the slope of the transition region of E9 (T) in

Meal Ready to Eat (MRE) bread (a = 26) compared with white bread

(a = 73) (Vodovotz and others 2000), indicating a more homoge-

neous transition in the MRE bread. Such an effect may have been

caused by the incorporation of glycerol as a plasticizer in this ex-

tended shelf life bread. Further work (such as the use of nuclear

magnetic resonance) is required to determine the origin of these

transitions.

Table 4—Results of fitting of E9 (T) of wheat and soy (20%,

30%, and 40%) bread with Fermi equation during storage

Storage time (d) Slope

a Tc

Control 0 10.8 6 0.7 –28.7 6 1.0

1 11.2 6 0.5 –28.9 6 1.2

2 11.0 6 0.3 –27.4 6 0.9

4 11.3 6 0.2 –26.6 6 2.8

7 11.5 6 1.1 –24.8 6 3.2

Average 11.1

6 0.6 –27.5

6 2.2

Soy 20% 0 7.1 6 0.8 –28.2 6 3.0

1 9.5 6 0.5 –31.2 6 0.7

2 9.4 6 0.6 –30.35 6 0.8

4 9.9 6 1.0 –29.7 6 2.8

7 9.8 6 1.1 –31.5 6 2.9

Average 8.9

6 1.4 –30.1

6 2.6

Soy 30% 0 9.0 6 1.1 –32.7 6 1.9

1 9.3 6 0.6 –33.3 6 1.5

2 9.3 6 0.6 –33.2 6 1.7

4 9.1 6 0.2 –30.8 6 2.0

7 9.4 6 0.1 –31.6 6 0.4

Average 9.2

6 0.7 –32.5

6 1.7

Soy 40% 0 8.2 6 0.4 –32.7 6 1.4

1 8.6 6 0.4 –33.6 6 0.4

2 8.7 6 0.1 –33.3 6 1.1

4 8.6 6 0.1 –32.7 6 0.4

7 8.8 6 0.7 –31.4 6 3.0

Average 8.5

6 0.4 –32.7

6 1.5

The average represents the average of all individual fitting for all samples

during storage 6 standard deviation.

Figure 6—E9 (T) Dynamic Mechanical Analysis at 25 °C for

wheat bread (circles, solid line) and 40% soy bread (tri-

angles, dashed line) during storage at room temperature

Figure 5—Typical differential scanning calorimetry thermo-

gram for fresh wheat bread

tan

Vol. 68, Nr. 6, 2003

—

JOURNAL OF FOOD SCIENCE 2027

Food Engineering and Physical Properties

JFS

is available in searchable form at

www.ift.org

Soy bread staling by thermal analyses . . .

Conclusions

HE ADDITION OF SOY FLOUR TO BREAD APPEARED TO HAVE A

mixed impact on the physicochemical properties of the final

product. An increase in the density of the bread was observed in

proportion to the amount of soy flour substitution. This negative

outcome may be offset by various factors. Addition of soy flour

helped retain moisture in the final product during storage as seen

by smaller changes in FW and moisture content than in the wheat

control. Furthermore, the addition of soy significantly decreased

the amylopectin crystallization during storage. Finally, soy ap-

peared to increase the homogeneity of the bread components as

demonstrated by the DMA storage modulus. Collectively, the

changes in water distribution and amylopectin recrystallization

indicate that soy may play a role in modulating the staling mecha-

nism of bread.

References

[AACC] American Assn. Cereal Chemists. 1983. Method 74-09. In: Approved

method of the AACC. 8th ed. St. Paul, Minn.: AACC.

[AOAC] Assn. of Official Analytical Chemists. 2002. Method 925.09. In: Official

methods of analysis. 17th ed. Volume II. Washington D. C.: AOAC.

Appelt LC, Reicks MM. 1999. Soy induces phase II enzymes but does not inhibit

dimethylbenz[a]anthracene-induced carcinogenesis in female rats. J Nutr 129:

1820–6.

Axford DWE, Colwell KH, Cornford SJ, Elton GA. 1968. Effect of loaf-specific vol-

ume on the rate and extent of staling in bread. J Sci Fd Agric 19:95-101.

Baik MY, Chinachoti P. 2000. Moisture redistribution and phase transition during

bread staling. Cereal Chem 77(4):484–8.

Baik MY, Chinachoti P. 2001. Effects of glycerol and moisture gradient on thermo-

mechanical properties of white bread. J Agric Food Chem 49:4031–8.

Baik MY, Kim KJ, Cheon K, Ha YC, Kim WS. 1997a. Effect of moisture content on

recrystallization of rice starch gels. Korean J Food Sci Tech 29:939–46.

Baik MY, Kim KJ, Cheon KC, Ha YC, Kim WS. 1997b. Recrystallization kinetics and

glass transition of rice starch gel systems. J Agric Food Chem 45:4242–8.

Brewer MS, Potter SM, Sprouls G, Reinhard M. 1992. Effect of soy protein isolate

and soy fiber on color, physical and sensory characteristics of baked products.

J Food Qual 15:245–62.

Buck JS, Walker CE, Watson KS. 1987. Incorporation of corn gluten meal and soy

into various cereal based foods and resulting product functionality. Sensory

and protein quality. Cereal Chem 64(4):264–9.

Chinachoti P. 1994. Probing molecular and structural thermal events in cereal-

based products. Thermochim Acta 246:357–69.

Dhingra S, Jood S. 2001. Organoleptic and nutritional evaluation of wheat breads

supplemented with soybean and barley flour. Food Chem 77:479–88.

Doxastakis G, Zafiriadis I, Irakli M, Marlani H, Tananaki C. 2002. Lupin, soya and

triticale addition to wheat flour doughs and their effect on rheological proper-

ties. Food Chem 77:219–27.

Draper CR, Edel MJ, Dick IM, Randall AG, Martin GB, Prince RL. 1997. Phytoestro-

gens reduce bone loss and bone resorption in oophorectomized rats. J Nutr

127:1795–9.

Erdman JM, O’Connor MP, Solomon LW, Nelson AI. 1977. Production, nutritional

value and baking quality of soy-egg flours. J Food Sci 964–8.

Fleming SE, Sosulski FW. 1977. Breadmaking properties of flour concentrated

plant proteins. Cereal Chem 54(5):1124–40.

[FDA] Food and Drug Administration. 1999. Food labeling: health claims; soy

protein and coronary heart disease. Final rule. 21 VFR Part 101. Washington,

D.C.: Dept. of Health and Human Services.

Fukutake M, Takahashi M, Ishida K, Kawamura H, Sigimura T, Wakabashi K. 1996.

Quantification of genistein and genistin in soybeans and soybeans products.

Food Chem Toxic 34:457–61.

Gerrard JA, Abbot RC, Newberry MP, Gilpin MJ, Ross M, Fayle SE. 2001. The effect

of non-gluten proteins on the staling of bread. Starch 53:278–80.

Hallberg LM, Chinachoti P. 1992. Dynamic mechanical analysis for glass transi-

tions in long shelf-life bread. J Food Sci 57:1201–4.

Hallberg LM, Chinachoti P. 2002. A fresh perspective on staling: The significance

of starch recrystallization on the firming of bread. J Food Sci 67:1092–6.

Hamann DD, Purkayastha S, Lanier TC. 1990. Applications of thermal scanning

rheology to the study of food gels. In: Harwalkar VR, Ma CY, editors. Thermal

analysis of foods. New York: Elsevier Science. p 306.

Kalichevsky MT, Jaroszkiewicz EM, Ablett S, Blanshard JMV, Lillford PJ. 1992. The

glass transition of amylopectin measured by DSC, DMTA and NMR. Carbohydr

Polym 18:77–88.

Klein BP, Perry AK, Van Duyne O. 1980. Composition and palatability of breads

made with ground soybean products. Home Econ Res J 9(1):27–35.

Knorr D, Betschart AA. 1978. The relative effect of an inert substance and pro-

tein concentrations upon leaf volume of breads. Lebens Wiss u Technol 11:198–

204.

Kulp K, Ponte JG, D’Appolonia BL. 1981. Staling of white pan bread: fundamental

causes. CRC Crit Rev Food Sci Nutr 15:1–48.

Leung HK, Magnuson JA, Bruinsma BL. 1983. Water binding of wheat flour doughs

and breads as studied by deuteron relaxation. J Food Sci 48:95–9.

Levine H, Slade L. 1988. Influences of the glassy and rubbery states on the ther-

mal, mechanical and structural properties of doughs and baked products. In:

Faridi H, Faubion JM, editors. Dough rehology and baked product texture. New

York: Van Nostrand Reinold. p 157–330.

Li S, Dickinson C, Chinachoti P. 1996. Proton relaxation of starch, gluten and their

mixture by solid-state nuclear magnetic resonance. Cereal Chem 73:736–43.

Longton J, LeGrys GA. 1981. Differential scanning calorimetry studies on the

crystallinity of ageing wheat starch gels. Stärke 33:410–4.

MacInnes WM, Roulet PH. 1988. Dynamic mechanical properties of starch gels.

In: Giesekus M, Hibbed MF, editors. Progress and trends in rheology. II. Pro-

ceedings of the 2nd Conference of European Rheologists; 17 June 1986; Pra-

gue. New York: Darmstradt, Steinkepff Verlag. p 431–4.

Maga JA. 1975. Bread staling. CRC Crit Rev Food Tech 8:443–86.

Murayama D. 1978. Dynamic mechanical analysis of polymeric material. Am-

sterdam: Elsevier Scientific. 40 p.

Omi N, Aoi S, Murata K, Ezawa, I. 1994. Evaluation of the effects of soybean milk

and soybean milk peptide on bone metabolism in the rat model with ovariec-

tomized osteoporosis. J Nutr Sci Vit 40:201–11.

Peleg M. 1993. Mapping the stiffness-temperature-moisture relationship of sol-

id biomaterials at and around their glass transition. Rhelog Acta 32:575–80.

Porter MA, Skarra LL. 1999. Reducing costs through the inclusion of soy flour in

breads. Cereal Foods World 44:632–7.

Reid DS, Hsu J, Kerr W. 1993. Calorimetry. In: Blanshard JMV, Lillford PJ, editors.

The glassy state in foods. Nottingham, U.K.: Nottingham Univ. Press. p 123–32.

Roos Y, Karel M. 1991. Plasticizing effect of water on thermal behavior and crys-

tallization of amorphous food models. J Food Sci 56:38–43.

Rogers DE, Zeleznak KJ, Lai CS, Hoseney RC. 1988. Effect of native lipids, short-

ening and bread moisture on bread firming. Cereal Chem 65(5):398–401.

Roulet PH, MacInnes WM, WŸrsch P, Sanchez RM, Raemy AA. 1988. Comparative

study of the retrogradation kinetics of gelatinized wheat starch in gel and

powder form using X-rays, differential scanning calorimetry and dynamic

mechanical analysis. Food Hydrocoll 2:381–96.

Russell PL. 1983. A kinetic study of bread staling by differential scanning calo-

rimetry and compressibility measurements: The effect of different grists. J

Cereal Sci 1: 285–96.

Ryan KJ, Homco-Ryan CL, Jenson J, Robbins KL, Prestat C, Brewer MS. 2002.

Effect of lipid extraction process on performance of texturized soy flour added

wheat bread. J Food Sci 67:2385–90.

Slade L, Levine IL. 1991. A food polymer science approach to structure-property

relationship in aqueous food systems: Non-equilibrium behavior of carbohy-

drate-water systems. In: Levine IL, Slade L, editors. Water relationships in

foods: advances in the 1980s and trends for the 1990s. New York: Plenum Pub-

lishing Corp. p 29-101.

Sosulski FW, Fleming SE. 1979. Sensory evaluation of bread prepared from com-

posite flours. Bakers Dig 53(3):20–1, 24–5.

Vodovotz Y, Baick MY, Vittadini E, Chinachoti P. 2000. Instrumental techniques

used in bread staling analysis. In: Chinachoti P, Vodovotz Y. editors. Bread stal-

ing. Boca Raton: CRC Press. p 93–111.

Vodovotz Y, Chinachoti P. 1996. Thermal transitions in gelatinized wheat starch

at different moisture contents by dynamic mechanical analysis. J Food Sci.

61:932–7.

Vodovotz Y, Chinachoti P. 1998. Glassy-rubbery transition and recrystallization

during aging of wheat starch gels. J Agric Food Chem 46(2):446–53.

Vodovotz Y, Hallberg L, Chinachoti P. 1996. Effect of aging and drying on thermo-

mechanical properties of white bread as characterized by dynamic mechani-

cal analysis (DMA) and differential scanning calorimetry (DSC). Cereal Chem

73:264–70.

Wendlandt WW, Gallagher PK. 1981. Instrumentation. In: Turi EA, editor. Ther-

mal characterization of polymeric materials. New York: Academic Press p 3–

25.

Zeleznak KJ, Hoseney RC. 1987. The glass transition in starch. Cereal Chem

64(2):121-4.

MS 20030042 Submitted 1/22/03, Revised 3/24/03, Accepted 5/8/03, Received

5/8/03

The authors would like to thanks Abdulah Sinan Colakoglu for his help with the thermal

analysis experiments. Additionally, the DSC press used in these experiments was obtained

through a grant awarded by the NASA Food Technology Commercial Space Center.

Author Vittadini is with Univ. degli Studi di Parma, Dept, di Chimica

Organica e Industriale, Parma Italy. Author Vodovotz is with the Food Sci-

ence and Technology Dept. The Ohio State Univ., 110 Parker Food Science

and Technology Bldg., 2015 Fyffe Court, Columbus, Ohio 43210. Direct in-

quiries to author Vodovotz (E-mail: vodovotz.1@osu.edu).