Assessment of the Fermentative Performance of Traditional Fresh Moroccan Sourdoughs and Their Freeze-Dried Forms Using Online Monitoring Device: Panigraph

Abstract

The fermentative activity of sourdoughs and their stabilities are some of the main concerns of professionals in food science. The aim of this study was to evaluate the fermenting capacity of three traditional fresh sourdoughs and their freeze-dried forms with different compositions prepared by housewives in three different regions of Morocco. A device equipped with several sensors was developed to monitor several parameters simultaneously and in real time (the pH, dough rise, loss of mass, CO₂ and ethanol release). The results showed that the duration of dough fermentation was long, ranging from 594 to 1210 min, with the specific volume ranging from 0.9 to 3.35 cm³/g⁻¹. A strong and positive correlation between dough rise and CO₂ release was observed, while ethanol release did not contribute directly to dough rise. The fresh sourdough FS1 showed better fermentative performance than the others, while the freeze-dried sourdough FDS3 was also of interest for bread making. The system used to generate the graphical fingerprints enabled us to read the main fermentation parameters directly in the same graph, as well as to compare several sourdoughs at once and choose the one best suited to our needs.

1. Introduction

Sourdough bread making is an ancient technique, and over the last three decades or so, there has been a flurry of research activity aimed at rediscovering the potential of sourdough fermentation and transferring this technology [1]. Sourdough is described as a mixture of flour and water, spontaneously fermented by a diverse microbial population composed mainly of lactic acid bacteria and yeasts [2,3].

Household microbiota, flour type, additional ingredients and tap water are the main microbial sources for establishing the potential of natural sourdough [4,5]. The microbial species diversity of sourdoughs is influenced by the producer’s domestic microbiota, geographical origin and propagation conditions [6]. The microbial consortia in sourdough first evolve in the fermentation stage and then in the refreshment stage, both resulting in successions of microbial populations until the microbiota become stable [7]. Some domestic sourdoughs are characterized by the presence of uncommon species [8].

Sourdough bread making involves the development and maintenance of a diversified and complex sourdough culture, hence the need for refreshment [9]. The production of fresh type I sourdough is costly, unstable and time-consuming [2] and requires periodic refreshing. Therefore freeze drying could be used to stabilize these sourdoughs to ensure a longer shelf life and store them for later use [10,11]. It is also an interesting method for preserving the viability of lactic acid bacteria (LAB) [12]. Producing sourdough bread with a consistently high quality, improved flavor and taste, extended shelf life and better resistance to spoilage requires the optimization and control of the bread-making processes determined by endogenous and exogenous factors [13]. A few studies have been carried out on traditional sourdoughs in Morocco with only three scientific articles cited by Arora in the last thirty years [1].

With this in mind, our study commences with a biochemical characterization of three traditional type I fresh sourdoughs, which are meticulously prepared by housewives in various regions of Morocco and primarily used for artisan bread production. Subsequently, we will assess and compare their fermentative capabilities in real time. To achieve this, we will initially compare the key biochemical parameters of these sourdoughs, including their pH, TTA (total titratable acidity), moisture content, and dough yield. This comparison is integral to elucidating the disparities that will emerge during the assessment of their fermenting capacity, which encompasses dough rise, gas release and reduction in pH. Following this initial analysis, we will proceed to freeze dry these sourdough starters in our laboratory. This freeze-drying process aims to evaluate their ability to endure the stress of dehydration. The ultimate goal of our research is to monitor the kinetics of various physical and biochemical parameters throughout the bread-making process in real time.

2. Materials and Methods

2.1. Raw Materials

Three samples of traditional, fresh sourdoughs, each over one year old, were collected from three regions in Morocco: Rabat, Guelmim and Tangier. These sourdoughs were prepared by housewives at home in a traditional manner with daily refreshments.

Table 1. Composition (%) of traditional fresh sourdoughs collected from households.

Fresh Sourdough Code	Housewives’ Regions	Water	Soft Wheat Flour	Dried Grapes	Durum Wheat Flour Complete	Fermented Milk (Lben)
FS1	Rabat	55.00	43.50	1.50	-	-
FS2	Guelmim	26.00	-	1.00	47.00	26.00
FS3	Tanger	50.00	49.00	0.93	-	-

displays the composition of the sourdoughs provided by the housewives. A 1 kg quantity of sourdough was collected from households before each analysis, and the samples were transported to the laboratory in a cooled container (4 °C) within 12 h.

2.2. Lyophilization

Fresh sourdough samples FS1, FS2, and FS3 were initially frozen at −18 °C and subsequently dehydrated using a SCIENTZ-12N freeze dryer at a temperature of −50 °C under a vacuum pressure of 10 Pa. No cryoprotective agents were employed. The resulting freeze-dried sourdough samples are designated as FDS1, FDS2 and FDS3, respectively.

2.3. Fermentation Monitoring System

An oven equipped with multiple sensors was developed for online monitoring of fermentation parameters, including dough rise (cm), CO₂ and ethanol release (ppmv), pH and mass loss (g). The data collected were stored in a database using software developed and installed on a computer connected to the oven [14]. Figure 1 shows the device used in this study.

2.4. CO₂ and Ethanol Release

The quantity of gases (CO₂ and ethanol) released during the bread-making process is measured in real time by sensors installed inside the panigraph. Based on the volume concentration values measured, their respective outputs were calculated using the following formula [15]:

Gas volume (mL) = Gas concentration (ppmv) × Volume (m³)

(1)

2.5. Total Titratable Acidity (TTA)

The doughs tested (10 g) were thoroughly mixed with 90 mL of distilled water, and 2–3 drops of phenolphthalein solution were added to the mixture. Total titratable acidity (TTA) was estimated as the amount of 0.1 N NaOH in milliliters (mL) required to neutralize the mixture [16].

2.6. Preparation of Bread Dough

The composition of the doughs is provided in

Table 2. The composition (in %) of the doughs used for bread-making tests (220 g each).

Dough Code	Sourdough Code	Water	Soft Wheat Flour	Table Salt	Baking Powder	Sourdough
DS1	FS1	34.40	55.50	1.00	0.10	9.00
DS2	FS2	34.40	55.50	1.00	0.10	9.00
DS3	FS3	34.40	55.50	1.00	0.10	9.00
DF1	FDS1	34.40	55.50	1.00	0.10	9.00
DF2	FDS2	34.40	55.50	1.00	0.10	9.00
DF3	FDS3	34.40	55.50	1.00	0.10	9.00
Control	without	38.90	60.00	1.00	0.10	0.00

; each dough weighed 220 g. A baker’s yeast (Saccharomyces cerevisiae) powder content of <0.2% was used to preserve the sourdough designation, in accordance with French legislation, especially article 4 of Decree no. 93-1074, dated 13 September 1993. An unleavened dough is used as a control. The leavening agent used for dough fermentation is fresh sourdough, which contains both yeast and endogenous bacteria.

2.7. Dough Rising (cm)

This parameter was measured directly by a device set up to calculate the dough’s rising capacity (DRC), following the formula mentioned by [17]. A minor modification was made, which involved substituting ‘volume’ with ‘dough height’. The glass vessel containing the dough has a cylindrical shape with an internal diameter of 14 cm.

$$DRC (\%)=(\mathrm{f}\mathrm{i}\mathrm{n}\mathrm{a}\mathrm{l} \mathrm{h}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}-\mathrm{i}\mathrm{n}\mathrm{i}\mathrm{t}\mathrm{i}\mathrm{a}\mathrm{l} \mathrm{h}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t})/\mathrm{i}\mathrm{n}\mathrm{i}\mathrm{t}\mathrm{i}\mathrm{a}\mathrm{l} \mathrm{h}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\left(100\right)$$

(2)

2.8. Dough Yield (DY)

The DY was calculated for each sourdough based on the composition provided by households (Table 1), and this value was used to determine each dough’s consistency. It represents the amount of water in the dough and is defined as follows [18]:

$$DY (\%)=\mathrm{f}\mathrm{l}\mathrm{o}\mathrm{u}\mathrm{r} \mathrm{q}\mathrm{u}\mathrm{a}\mathrm{n}\mathrm{t}\mathrm{i}\mathrm{t}\mathrm{y}+\mathrm{w}\mathrm{a}\mathrm{t}\mathrm{e}\mathrm{r} \mathrm{q}\mathrm{u}\mathrm{a}\mathrm{n}\mathrm{t}\mathrm{i}\mathrm{t}\mathrm{y}\left)\right(100)/(\mathrm{f}\mathrm{l}\mathrm{o}\mathrm{u}\mathrm{r} \mathrm{q}\mathrm{u}\mathrm{a}\mathrm{n}\mathrm{t}\mathrm{i}\mathrm{t}\mathrm{y})$$

(3)

2.9. Dough Fermentation Temperature and Duration

The temperature inside the oven during dough fermentation was set to 30 °C for all tests [19], and the maximum duration of bread making was limited to 1440 min.

2.10. Dough Moisture

Moisture content was measured for the following samples: fresh and freeze-dried sourdoughs as well as the doughs both before and after fermentation. A total of 10 g of each sample was placed in an OHAUS MB45 moisture meter, with a reading accuracy of 0.001 g and a repeatability of 0.015%.

2.11. Statistical Analysis of Data

Results are expressed as means (±standard deviations), and differences between theoretical means were tested using ANOVA 1 followed by Tukey’s test to identify any homogeneous groups of means. All tests were performed at a significance level of 5%. Principal component analysis (PCA) was used to determined correlations between bread-making parameters. The various measurements were carried out with three repetitions, and statistical analyses were performed using ExcelStat V2016.02 software.

3. Results

3.1. Sourdough Characterization

Our results in

Table 3. Mean values (±standard deviations) of the key parameters that characterize fresh sourdough samples.

Fresh Sourdough Code	TTA (mL NaOH/10 g of Dough)	pH	Moisture (%)	DY (%)	Consistency
FS1	14.12 ± 5.03 a	3.44 ± 0.09 a	54.57 ± 1.00 a	226.87 ± 1.80 c	Liquid
FS2	39.24 ± 2.91 b	3.79 ± 0.05 b	55.74 ± 1.29 ab	155.31 ± 0.70 a	Farm
FS3	14.28 ± 1.47 a	3.36 ± 0.07 a	57.12 ± 0.34 b	202.60 ± 1.11 b	Soft

Values in the same column with at least one letter (a–c) in common are not significantly different at the 5% probability level.

, which presents the mean values (±standard deviations) of the parameters obtained by the fresh sourdoughs, demonstrate the significant influence of the fresh sourdough composition on the studied parameters.

The DY of the FS1, LF2 and LF3 sourdoughs ranged from 154.6 to 228.60%, with an average of 226.87% for FS1, 155.31% for FS2 and 202.60% for FS3, allowing us to assess their consistency. The moisture levels ranged from 53.41% to 57.51% for the fresh sourdoughs. FS3 had a higher moisture content (57.12 ± 0.34%) than FS1 (54.57 ± 1.00%), despite the latter having a higher DY. The average TTA ranged from 10.86 to 42.05. The FS2 sourdough had the highest TTA value (39.24 ± 2.91), while FS1 and FS3 had similar average TTA values (14.20 ± 3.32). The average pH ranged from 3.27 to 3.85 for the fresh sourdoughs. Although FS2 had a higher TTA than FS1 and FS2, its pH was higher than those of the latter.

Table 4. Mean values (±standard deviations) of the key parameters characterizing freeze-dried sourdough samples.

Freeze-Dried Sourdough Code	TTA (mL NaOH/10 g of Dough)	pH	Moisture (%)
FDS1	37.71 ± 0.76 a	2.98 ± 0.02 a	8.05 ± 0.82 b
FDS2	74.20 ± 0.85 b	3.57 ± 0.20 b	7.21 ± 0.32 b
FDS3	37.24 ± 0.73 a	3.03 ± 0.06 a	3.10 ± 0.64 a

Values in the same column with at least one letter (a, b) in common are not significantly different at the 5% probability level.

shows the biochemical characteristics of the freeze-dried sourdoughs used in the laboratory bread-making tests. The sourdough composition has a significant effect on the TTA, pH and moisture.

The average TTA of the freeze-dried sourdoughs ranged from 36.66 to 75.13, with FDS2 (74.20 ± 0.85) showing a higher acidity following its high initial acidity when fresh. The average pH of the freeze-dried sourdoughs ranged from 2.96 to 3.8. Their moisture content ranged from 2.61 to 8.99%, with FDS1 and FDS2 having a higher average moisture content (7.63 ± 0.60%) compared to FDS3 (3.10%).

3.2. Assessment of Fermentation Capability

The fermentative performance of the sourdoughs was assessed by their ability to leaven the dough, release CO₂ and ethanol, raise TTA levels and reduce the final pH of the dough [20]. Figure 2 shows the online monitoring of the bread-making process.

A panigraph can monitor the dough rise, mass loss, CO₂ and ethanol release, reductions in pH and conductivity of dough, enabling us to assess the fermentative capacity of the sourdoughs studied. Figure 3a,b show an example of breads obtained by baking doughs fermented with fresh or freeze-dried sourdough, respectively.

3.2.1. Dough Rise during Bread Making

The results in Figure 4, illustrating the dough leavening during the bread-making process, demonstrate that the leavening progresses through four phases: induction phase I, rapid swelling phase II, stabilization phase III and a slight decrease in volume during phase IV for certain doughs.

Figure 4 depicts the values of the primary physical parameters of the doughs at the end of the bread-making process (as presented in

Table 5. Mean values (±standard deviations) of the key physical characteristics of doughs at the end of the bread-making process.

Dough Code	Dough Rise (cm)	End of Bread Making (min)	Specific Volume (cm3/g−1)	Loss Mass (%)
Control	3.44 ± 0.66 a	655.67 ± 55.61 d	2.78 ± 0.50 a	2.2 ± 0.01 a
DS1	2.42 ± 0.42 abc	738.67 ± 21.13 d	2.26 ± 0.24 ab	2.9 ± 0.01 a
DS2	1.89 ± 0.47 bc	1020.67 ± 47.38 abc	1.65 ± 0.38 bc	2.8 ± 0.01 a
DS3	2.42 ± 0.27 abc	914.67 ± 7.51 c	2.18 ± 0.27 ab	2.8 ± 0.01 a
DF1	2.54 ± 0.40 ab	1076.33 ± 94.79 ab	2.17 ± 0.33 ab	3.1± 0.01 a
DF2	1.25 ± 0.19 c	1151.67 ± 51.07 a	1.01 ± 0.13 c	2.1 ± 0.01 a
DF3	2.55 ± 0.50 ab	927.33 ± 60.05 bc	2.14 ± 0.42 ab	2.7 ± 0.01 a

Values in the same column with at least one letter (a–d) in common are not significantly different at the 5% probability level.

), corresponding to the beginning of the flattening of these curves (the onset of phase III).

The sourdough type had a significant effect on the dough rise (Table 5), with means ranging from 1.25 to 3.44 cm. The control dough exhibited the best rise (3.44 ± 0.66 cm), followed by FDS3 (2.55 ± 0.5 cm) and FDS, which had an average rise of (2.54 ± 0.4 cm). DS1 and DS3 showed a similar average dough rise of around (2.42 cm), while DS2 and its freeze-dried form, FDS2, showed the lowest rises (1.89 and 1.25 cm, respectively).

3.2.2. Bread-Making Duration

The type of sourdough significantly affects the duration of bread making, with an average duration ranging from 655.67 to 1151.67 min, which was considered to be a long fermentation period. The times obtained for the freeze-dried sourdoughs (867.82 to 1274.74 min) were higher than those for their fresh forms (717.54 to 1087.05 min). The control doughs and DS1 doughs required similar bread-making times, from 600 to 760 min, while the others required longer bread-making times (907 to 1203 min). DS2 and its freeze-dried form (FDS2) required longer average bread-making times (1020.67 and 1151.67 min, respectively). It should be noted that the LF2 sourdough did not perform as well in terms of its bread-making time than its freeze-dried forms (FDS1 and FDS3). DS1 required less bread-making time than DS3, despite having the same composition except for the hydration rate (Table 2), while FDS3 required less bread-making time (927.33 min) than FDS1 (1076.33 min).

3.2.3. Specific Volume

The effect of the sourdough type and composition on the doughs’ specific volume was significant, with mean values ranging from 1.01 to 2.78 cm³/g⁻¹. The control had the highest specific volume (2.78 ± 0.51 cm³/g⁻¹). The FDS1 and FDS3 sourdoughs and their freeze-dried forms had the same specific volume, ranging from 1.77 to 2.5 cm³/g⁻¹, while the FS2 fresh sourdough and its freeze-dried form presented the lowest specific volume (0.88 to 2.03 cm³/g⁻¹).

3.2.4. Loss of Mass

The different sourdough types showed no significant differences in their dough mass losses at the end of the bread-making process, with an average mass loss rate of 2.66%.

3.3. Biochemical Characterization of Dough

3.3.1. CO₂ Release during Bread Making

The results in Figure 5, which illustrates the CO₂ release as a function of time during the bread-making process, reveals a difference in the shape of the CO₂ release curves. This figure shows the average values of CO₂ released at the end of the bread-making process, as well as its average speed (

Table 6. Mean values (±standard deviations) of CO₂ released at the end of bread-making process.

Dough Code	CO2 Released (L/kg−1 of Dough)	Speed Release of CO2 mL/(100 g/h)−1
Control	0.62 ± 0.10 ab	5.55 ± 0.42 a
DS1	0.66 ± 0.20 a	5.19 ± 1.51 ab
DS2	0.48 ± 0.08 ab	2.77 ± 0.51 bc
DS3	0.52 ± 0.26 ab	3.32 ± 1.67 abc
DF1	0.44 ± 0.15 ab	2.37 ± 0.81 c
DF2	0.19 ± 0.01 b	1.01 ± 0.07 c
DF3	0.59 ± 0.14 ab	3.70 ± 0.89 abc

Values in the same column with at least one letter (a–c) in common are not significantly different at the 5% probability level.

).

The type of sourdough had a significant effect on the amount of CO₂ released at the end of the bread-making process, with average amounts produced ranging from 0.18 to 0.78 L/kg⁻¹ of dough and the average speed varying from 0.94 to 6.18 mL/100 g/h. Although the DS1 dough was able to produce the greatest amount of CO₂ (0.66 L/kg⁻¹ of dough) compared to the control (0.62 L/kg⁻¹ of dough), its sourdough was unable to leaven it in the same way as the latter. The FDS2 dough produced the lowest amount of CO₂ (0.19 L/kg⁻¹ of dough), which explains its low specific volume (1.01 cm³/g⁻¹) and long bread-making time (1151.67 min). Figure 6 shows the dough rise as a function of the CO₂ release during the bread-making process.

The results in Figure 6 illustrate the close relationship between the dough leavening and the CO₂ released during the bread-making process. However, for the same amount of CO₂ released, leavening does not hold the same significance for various doughs, especially during the swelling (phase II) and stability (phase III) phases.

3.3.2. Ethanol Release during Bread Making

The results in Figure 7 illustrate the kinetics of the ethanol release during the bread-making process.

Figure 7 presents both the average values of ethanol released at the end of the bread-making process and its average rate of release, as summarized in

Table 7. Mean values (±standard deviations) of ethanol released at the end of the bread-making process.

Dough Code	Ethanol Released (L/kg−1 of Dough)	Speed Release of Ethanol mL/(100 g/h)−1
Control	5.58 ± 0.89 bc	49.76 ± 3.77 a
DS1	3.92 ± 0.33 ab	30.88 ± 1.82 bcd
DS2	5.90 ± 0.78 a	33.86 ± 5.89 b
DS3	5.27 ± 0.92 bc	33.60 ± 5.93 bc
DF1	3.32 ± 1.90 a	18.05 ± 10.03 cd
DF2	3.27 ± 0.62 a	16.54 ± 3.30 d
DF3	3.75 ± 0.76 ab	23.59 ± 4.60 bcd

Values in the same column with at least one letter (a–d) in common are not significantly different at the 5% probability level.

.

The type of sourdough had a significant effect on the quantity and rate of ethanol released, with quantities ranging from 1.28 to 6.66 L/kg⁻¹ of dough and rates from 6.68 to 52.89 mL/(100 g/h)⁻¹. The release of ethanol continued after the end of the bread-making process (Figure 7), but it had no effect on the dough volume (Figure 4). Figure 7 also demonstrates an increase in the ethanol amount of the control after the end of the bread-making process, probably due to the bursting of the dough network. This is confirmed by the slight decrease in dough volume following deflation (Figure 4).

3.3.3. Variation in pH and TTA of Fermented Doughs

The sourdough type had a significant effect on the initial dough pH and pH variation, but no significant effect on the final pH. The initial pH ranged from 3.83 to 5.61, while final pH averaged 3.69, with an average decrease of 0.63. The freeze-dried sourdough doughs had a lower initial pH, ranging from 3.84 to 4.1, which is due to the initially high acidity of freeze-dried sourdoughs, while the fresh sourdough doughs had a similar initial pH, ranging from 4.15 to 4.41. The control dough had the highest initial pH, with an average of 5.58. However, the control required around 400 min to reach this value. The pH drop was greater for the control (1.52), resulting in a final pH of 4.06. FDS2, with its initially low pH, had a lower specific volume than that of DS2. Figure 8 shows the evolution of dough pH during the bread-making process.

Table 8. Mean values (±standard deviations) for pH and acidity of doughs at the end of bread-making process.

Dough Code		pH		TTA (mL NaOH 0.1 N (10 g)−1)
	Initial (pH_i)	Final (pH_f)	Decrease	Initial (ATT_i)	Final (ATT_f)	Increase
Control	5.58 ± 0.03 a	4.06 ± 0.59 a	1.52 ± 0.62 a	2.19 ± 0.21 d	4.05 ± 0.11 e	1.85 ± 0.28 d
DS1	4.37 ± 0.04 b	3.57 ± 0.01 a	0.80 ± 0.05 ab	3.37 ± 0.12 c	8.27 ± 0.03 c	4.90 ± 0.14 c
DS2	4.20 ± 0.05 b	3.51 ± 0.09 a	0.70 ± 0.10 b	5.52 ± 0.41 b	15.02 ± 0.91 a	9.50 ± 0.52 a
DS3	4.31 ± 0.06 b	3.44 ± 0.11 a	0.88 ± 0.16 ab	3.68 ± 0.11 c	9.96 ± 0.26 b	6.28 ± 0.20 b
DF1	3.94 ± 0.16 c	3.76 ± 0.43 a	0.18 ± 0.27 b	5.23 ± 0.41 b	6.58 ± 0.26 d	1.35 ± 0.58 de
DF2	3.86 ± 0.02 c	3.72 ± 0.07 a	0.14 ± 0.07 b	8.89 ± 0.50 a	9.57 ± 0.42 b	0.68 ± 0.29 e
DF3	3.94 ± 0.01 c	3.70 ± 0.10 a	0.23 ± 0.10 b	5.10 ± 0.39 b	6.56 ± 0.12 d	1.45 ± 0.34 de

Values in the same column with at least one letter (a–e) in common are not significantly different at the 5% probability level.

shows the average pH and ATT values measured at the start and end of fermentation.

The type of sourdough had a significant effect on initial and final TTA, as well as on its increase. The initial TTA of the doughs varied from 1.96 to 9.43 (mL 0.1 N NaOH per 10 g of dough), while the final TTA varied from 3.92 to 15.69 with an increase ranging from 0.39 to 9.96. FDS2 had the highest initial TTA value (8.89), while the control had the lowest initial TTA value (2.19). The DS2 dough had the highest final TTA value (15.02), while the control dough presented the lowest value (4.05) due to the high production of biogenic acids, whereas their production was very low in the control. Despite FDS2 having the highest initial TTA (8.89), its fresh form was able to acidify the dough more, with the greatest TTA increase (9.50), while its freeze-dried form achieved the lowest TTA increase (0.68). The FS2, FDS1 and FDS3 doughs had a similar average initial acidity of around (5.52); however, FDS2 was able to significantly increase the final TTA of the dough (15.02), while FDS1 and FDS3 only slightly increased it (6.58).

3.4. Correlations of Bread-Making Parameters

The results in Figure 9a,b show the projection of the ten bread-making parameters (taking into account the initial and final values for the pH and TTA) and the six sourdoughs (including the control) on the principal plane (80.05%) of a principal component analysis (PCA). A strong positive correlation was observed between the bread-making time and initial TTA. The highest values for this first group of parameters were obtained for the DF1, DS2 and DF2 doughs. Similarly, positive correlations were recorded between the dough rise, specific volume, initial pH and CO₂ released. The highest values for this second group of parameters were obtained for the control, DS1, DF3 and DS3 doughs. The two groups of variables showed negative correlations. Interestingly, the amount of ethanol released did not appear to correlate with the other bread-making parameters.

3.5. Individual Panigram of FS1 and FDS3 Sourdoughs

Based on the analysis of the bread-making tests, it becomes evident that the FS1 fresh sourdough and FDS3 freeze-dried sourdough outperform the other sourdough variants. Figure 10 and Figure 11 illustrate the kinetics of the primary bread-making parameters for the FS1 and FDS3 doughs, respectively.

The individual panigrams (Figure 10 and Figure 11) allow for the direct reading of the main parameters on the same graph during the bread-making process, enabling the determination of the end of the process. Furthermore, they facilitate the study of the doughs’ behavior beyond the final stage of the bread-making process.

3.6. Vertical Panigram of All Doughs

A vertical chart is another way to compare the fermentative performance of several sourdoughs. Figure 12 displays the main bread-making parameters of the different doughs.

This graph can be used as an easy tool for mapping the main bread-making parameters, both visually and numerically.

4. Discussions

4.1. Sourdough Comparisons

The TTA, pH and humidity values of a sourdough depend on its composition. The FS2 sourdough has a high TTA, which is explained by the presence of large quantities of LAB bacteria due to the use of whole wheat whey and flour. Similar findings were observed by [21]. The high acidity of the FS2 sourdough does not correlate with its pH. This was explained by the buffering effect of the medium following the reduction of the H+ proton by the constituents of the sourdough, notably gluten [22].

The freeze drying of the three fresh sourdough samples led to the concentration of biogenic acids through the evaporation of water. Consequently, there was an increase in TTA and a decrease in pH. According to [23], this could potentially reduce their fermentation performance due the inhibition of existing microorganisms, particularly yeasts, which are highly sensitive to dehydration and acidic pH levels. Therefore, it is essential to control the initial acidity of the leaven and optimize the freeze-drying process by adding cryoprotective agents or by revitalizing freeze-dried sourdoughs before using them for bread making. Freeze drying resulted in an average reduction in moisture content ranging from 2.61 to 8.99%. According to [24], this level of moisture reduction ensures the stability and extended storage of type III sourdoughs by preventing undesirable biochemical and microbiological reactions. The variations in moisture content observed among the freeze-dried sourdoughs can be attributed to differences in their textures, which affect water release during the dehydration process.

4.2. Bread Fermentation Performance Tests

The tested sourdough samples exhibited a dough rising capacity (DRC) exceeding 100%, indicating their capability to produce bread dough. The higher specific volume observed in the FS1 and FS3 doughs may be attributed to the increased CO₂, as suggested by [25], resulting from adequate dough acidification, which enhances the gluten’s gas-retaining ability. Conversely, the excessive acidity of the FS2 and FDS2 sourdoughs hindered their fermentation performance, a phenomenon elucidated by [22], who explained it as the inhibitory effect of acidity on the main yeasts responsible for CO₂ production. The authors of [26] also reported a similar trend, in which firm-consistency sourdoughs like the FS2 fresh sourdough promoted the production of acetic acid, which had a strong negative influence on the yeast activity.

The FDS2 dough exhibited a reduced specific volume in comparison to its fresh FS2 counterpart. This phenomenon can be elucidated, according to [27], by the adverse impact of the simultaneous presence of an acidic pH and a high ethanol concentration on yeast growth.

The delay in proofing observed in phase I of the freeze-dried sourdoughs (approximately ±200 min) can be attributed to the presence of injured and stressed cells, which are found in reduced numbers in freeze-dried sourdoughs, as explained by [28] in their study. To address this issue, the authors of [24] suggest employing pretreatments such as rehydration or the refreshment of leavens to activate them effectively and ensure their fermentative activity. Additionally, the use of cryoprotective agents during the freeze-drying process is recommended. It is also worth noting that the acidity level of fresh sourdough appears to have a significant impact on the fermentation capabilities of its freeze-dried counterpart. For instance, FS2, with a TTA of 39.24, exhibited a shorter bread-making time compared to FDS2, which has a TAA of 74.20.

The extended fermentation time observed in the doughs of the freeze-dried sourdoughs can be elucidated through the findings of [29]. They proposed that this phenomenon is attributed to the presence of organic acids generated by rapidly proliferating bacteria, which inhibit the fermentation activity of less acid-tolerant species. Furthermore, in [12], Caglar reported a high mortality rate among microorganisms due to the freeze-drying process. Conversely, an extended fermentation period enables certain freeze-dried sourdoughs to approach the level of dough rise achieved by specific fresh sourdoughs.

The decline in dough volume observed in certain sourdough types during phase IV can be attributed to the rupture of the network and the release of CO₂ outward; this phenomenon is indicative of the dough reaching its point of porosity.

The FS1 dough requires less bread-making time than FS3, confirming the significant role of hydration in the microbial ecology and the metabolic function of the sourdough. However, the FDS3 dough exhibited a shorter bread-making time than FDS1. This discrepancy could be attributed to a higher mortality rate of the microorganisms in the FDS1 sourdough, resulting from its slightly elevated hydration level and the consequent cell wall rupture of the microorganisms during freezing, which precedes the freeze-drying process [30,31]. From these observations, it can be inferred that while the liquid form of the fresh sourdough holds promise for bread making, its freeze-dried form may not be necessary yield the same benefits. The kinetics of dough rise are analogous with the release of CO₂, thus affirming its important role in dough expansion, which aligns with the findings presented by [32] in their study. Nevertheless, when an equal amount of CO₂ is liberated, the extent of dough expansion varies notably among different dough compositions, especially during phases II (swelling) and III (stability); this variation can be attributed to the discrepancies in their gas retention capacities and elasticity stemming from leavening agents. Consequently, the sole criterion of producing a substantial quantity of carbon dioxide does not suffice to predict the extent of dough rise. The production of CO₂ was, on average, nine times lower than that of ethanol at the end of the bread-making process. This suggests that ethanol has no significant effect on the dough rise, and CO₂ remains the primary gas responsible for its expansion [32]. This can be attributed to the gaseous state of CO₂ within the dough under the bread-making conditions, in which the saturation vapor pressure (Pvs) of CO₂ is 56.45 atm at 20 °C. In contrast, ethanol exists in liquid form within the dough because of its Pvs (0.05 atm at 20 °C). Consequently, ethanol is present as a volatile fraction quantified by the sensor and exists in phasic equilibrium (liquid–gas) on the surface of the dough’s crust. Due to this difference in state, ethanol does not directly contribute to the rise of the dough. Therefore, CO₂ remains the primary gas responsible for the swelling of the dough. However, ethanol does play a role in strengthening the overall structure of the dough, resulting in a soft and airy texture in the crumbs of the sourdough bread [33].

The average initial pH of doughs is typically below 4.6, which is generally considered the optimal pH for phytic acid degradation [34]. As noted by Chron [35], a long-term and acidifying fermentation process enables the significant degradation of phytic acid, enhancing the bioavailability of minerals. Additionally, the final pH of the doughs obtained (3.69) plays a vital role in reducing the staleness of the bread as discussed by Arendt [36]. The decrease in pH was more pronounced in the control, primarily attributed to the activity of endogenous bacteria, which faced less competition from baker’s yeast (S.C) due to its low incorporation rate of only 0.1%.

The FDS2 dough exhibited the highest initial TTA value (8.89). This can be attributed to the initially high acidity of the FDS2 dough used as the seeding agent. Conversely, the control sample displayed the lowest initial value of TTA (2.19), which can be attributed to the low initial acidity of the flour, the sole source of acids in this case. The addition of FS1 enabled an increase in the final TTA of the dough (8.27) without acidifying it. This level of acidity is considered very acceptable in terms of its organoleptic properties [37].

The vertical panigram represents an innovative approach for efficiently assessing various parameters in sourdough bread making simultaneously. It generates a digital map illustrating the fermentation performance of different sourdoughs in a visually comprehensive manner. Consequently, this tool offers a rapid and effective means of making informed decisions when selecting the most efficient and appropriate sourdough for achieving high-quality bread products.

Individual panigrams derived from the panigraph enable the real-time monitoring of fermentation kinetics and facilitate predictions regarding the completion of the bread-making process. Furthermore, they allow for the establishment of a comprehensive database for professionals and researchers to compare the performance and stability of their respective sourdoughs.

5. Conclusions

In this study examining the fermentative capabilities of traditional fresh sourdoughs produced by households in various regions and their freeze-dried counterparts, the FS1 fresh sourdough demonstrated notable advantages compared to the control. These advantages included a reduced bread preparation time, a high specific volume and a very satisfactory final bread quality. The FDS3 sourdough exhibited a dough rise similar to that of fresh sourdoughs but with a somewhat longer bread preparation time, which could be enhanced through revitalization. Utilizing a panigraph for the real-time, simultaneous monitoring of various bread-making parameters allowed for the creation of individual and vertical panigrams for the different sourdough types. These panigrams, likened to unique fingerprints, facilitated a straightforward visual comparison of the fermentative capabilities of various sourdough varieties. Future research should explore the integration of sensory and microbiological criteria within these panigrams.