Application of Fermented Wheat, Acorns, and Sorghum in Processing of Couscous: Effect on Culinary Quality, Pasting Properties, and Microstructure

Abstract

This study explores the application of three fermented plant materials—wheat, acorns, and sorghum—in couscous preparation, as well as their impact on its properties. A survey was conducted in some localities in Algeria. The aim is to reproduce the diagrams for the manufacture of different types of couscous incorporated with fermented materials and to evaluate the pasting properties, culinary qualities, and microstructure of each type of couscous produced. The survey identified four couscous formulations made with durum wheat semolina: couscous 1 (4% sorghum, 4% wheat, 8% acorns), couscous 2 (8% acorns), couscous 3 (0.8% sorghum, 6% acorns), and couscous 4 (4% wheat, 4% acorns). A comparative study of the four types of couscous showed significant differences in their physicochemical and microstructural properties. Formulations C3 and C4 showed the best functional performance among all the couscous samples studied. In terms of the swelling index, measured at 25 °C and 95 °C, C3 reached 131.11% and 165.55%, respectively, while C4 recorded 124.9% and 157.0%. Furthermore, these two formulations had the highest viscosity values: initial viscosity of 25 mPas (C3) and 27 mPas (C4), maximum viscosity of 31 mPas (C3) and 30 mPas (C4), and final viscosity of 49 mPas (C3) and 46 mPas (C4). Analysis of the cooking loss revealed higher values for couscous 1 and 2. The microstructure of couscous 2 revealed the presence of native starch particles, open porosity, and a state of partial gelatinization. The study revealed that formulations C3 and C4 significantly (p < 0.05) impact couscous structure by enhancing functionality while preserving quality. It also maintained ancestral knowledge and offered valuable insights for future industrial applications.

1. Introduction

Couscous, a staple food widely consumed in various African countries, is a processed product made from native cereal particles [1]. Its production involves a series of unit operations combining physical treatments, such as mixing and rolling, and hydrothermal treatments, including hydration, steaming, and drying. These physicochemical transformations induced by wet agglomeration give couscous its techno-functional and organoleptic characteristics [2,3,4,5,6]. The quality of couscous is defined by a homogeneous and regular grain size, a color ranging from amber yellow (for durum wheat couscous) to brown (for couscous made with fermented plant materials), and excellent cooking properties, characterized by the grains maintaining their individuality without disintegration or clumping [2,3,7,8]. The composition and preparation methods of couscous vary geographically. In West Africa, a variety of cereals are used, including sorghum (Sorghum bicolor), millet (Pennisetum glaucum), maize (Zea mays), and fonio (Digitaria exilis) [9]. In North Africa, durum wheat semolina (Triticum durum) is the main ingredient [10]. In Algeria, durum couscous enriched with fermented materials has gained significant popularity.

Fermentation is a biotechnological process recognized for its multiple beneficial effects, including improved organoleptic quality (flavor), nutritional enrichment, extended shelf life, reduction in undesirable compounds (detoxification), and development of health-promoting properties [11,12]. Several types of fermented plant materials are traditionally employed in the production of various couscous varieties, including sorghum, acorns, and durum wheat [3,13]. Fermented durum wheat, locally known as «Lemzeïet» has been the subject of limited research. To date, there are only two studies that have explored the preparation of Lemzeïet couscous [3,14]. While Becila et al. [3] have extensively studied Lemzeïet couscous, other traditional fermented varieties deserve further scientific investigation. Acorns and sorghum, when fermented through traditional methods, present a promising avenue for the development of functional foods [13]. Fermentation improves the functional properties of plant materials, facilitating their transformation and product shaping. It enriches the sensory profile with aromatic compounds and prolongs shelf life as a result. Nutritionally, it reduces antinutritional factors and improves the bioavailability of micronutrients. It is essential to investigate the effects of these modifications on food products. According to a survey conducted by Belmouloud et al. [13], couscous emerges as the most prevalent product derived from fermented acorns and sorghum.

In this context, the main objective of this work was to describe the traditional steps for manufacturing different types of couscous based on durum wheat semolina, incorporating fine semolina from fermented wheat, as well as flours from fermented acorns and fermented sorghum. The findings are based on a survey of couscous producers across three provinces in northeastern Algeria. Preserving this traditional knowledge is crucial for communities. Beyond enriching the diverse culinary heritage, it also provides helpful strategies for solving challenges concerning food security and long-term ecological balance. In addition, this study aimed to reproduce these traditional couscous varieties and evaluate their culinary qualities, pasting properties, color characteristics, and microstructure.

2. Materials and Methods

2.1. Raw Materials

The raw materials used in this study included durum wheat semolina (Triticum durum) from the local Algerian market (Jijel province) containing 14.50% moisture, 13.00% protein, 1.00% lipids, and 0.90% ash content. Fermented wheat fine semolina (FW), sourced from a shop in the Constantine province (Algeria) and prepared according to the spontaneous fermentation process, at ambient temperature, with a complete immersion in water of wheat under anaerobic conditions for 3 to 6 months, as reported by Merabti [15], contained 10.97% moisture, 14.50% protein, 1.29% lipids, and 1.00% ash. Fermented acorns (FA) flour (Quercus ilex) was supplied by local artisans (Benyahia K., Ziama Mansouriah, Jijel, Algeria) and fermented using the spontaneous fermentation process, at ambient temperature, acorns were completely immersed in water under anaerobic conditions for 5 months, followed by natural solar drying at the end of the fermentation period, as described by Belmouloud et al. [13]. The flour obtained had a composition of 10.47% moisture, 5.40% protein, 13.59% lipid, and 1.29% ash. Fermented sorghum (FS) flour (Sorghum bicolor), sourced from local artisans (Roula N., Texenna, Jijel, Algeria) and fermented according to the spontaneous fermentation process, at ambient temperature, sorghum underwent complete immersion in water under aerobic conditions for 8 months, after which natural solar drying was applied at the end of the fermentation period, as reported by Belmouloud et al. [13], contained 9.17% moisture, 9.91% protein, 3.65% lipids, and 2.50% ash. Iodized salt (Entreprise Nationale Algérienne du sel, Constantine, Algeria) was used.

2.2. Investigation of the Couscous Production Diagram

2.2.1. Survey Area and Data Collection

A survey focused on three provinces in northeast Algeria: Jijel, Skikda, and Bejaïa (Figure 1), was conducted between April and December 2022. The choice of these regions was based on a pre-survey carried out in nine provinces in northeastern Algeria, where only people from the selected regions participated in the survey. The selected regions are the most popular in terms of production and consumption of fermented couscous.

This survey explored local couscous-making practices using fermented wheat, acorns, and sorghum. To carry out this study, 200 women with experience in making traditional couscous were selected in the target province. These women, aged between 21 and 83, constituted our representative sample. Data were collected through individual interviews with experienced couscous makers, ensuring accurate and dependable information due to their thorough understanding of the various couscous preparations.

The chosen people consented to participate voluntarily. A purposive sampling method was employed to select respondents from diverse areas, including housewives. The participants were chosen based on their knowledge of the product, customary practices, and consumption behaviors. The local language was employed to facilitate effective communication and precise data collection. Individuals without knowledge of the examined traditional practice were excluded.

The questionnaire was submitted to a sample of 40 women experienced in couscous-making during a pre-survey. The first version used during this pre-survey was more general and focused mainly on the use of fermented flours, their quantities, and the preparation of raw materials. It did not contain predefined production steps; instead, it relied on open-ended interviews where respondents described their process step by step. Specific questions during this phase included the type of flour used in couscous making, the use of fermented flours in which quantities, the raw material preparation (sieving), the step-by-step description of the preparation process, etc.

Following this evaluation, significant modifications were made, leading to the validation of the final version of the questionnaire. In this revised version, additional specific questions were added to cover each identified step of the production diagram. These included the steam step of coarse semolina before using it in the couscous-making process; if this step is omitted, the key indicators to judge that a step is complete (e.g., texture, smell, appearance, etc.). The questionnaire combines both multiple-choice and open-ended formats and is organized into two distinct sections: (i) the socio-demographic profile of the respondents, aimed at characterizing the surveyed population (age, education level, source of knowledge, region), and (ii) the technical and practical aspects of couscous production.

For the production process, the study covered the entire production process, from the initial preparation of flour and semolina to the final packaging of the finished product. Particular attention was devoted to the traditional techniques employed (sieving, hydration, rolling, and drying) and the tools used.

2.2.2. Reproduction of Traditional Couscous Making

The manufacturing steps (Figure 2) have been reproduced on the basis of information gathered during the survey. The utensils used are detailed in the following sections. Four sieves were used for particle sizing and grading, each characterized by a specific mesh opening. These sieves are known locally as “azzel” (500 µm), “reffad” (1000 µm), “meâaoudi” (1130 µm), and “sekkat” (1280 µm).

To ensure the stability of couscous samples prior to analysis, they were stored in airtight containers, in the dark, and at room temperature.

2.3. Characterization of the Produced Couscous

2.3.1. Color Determination

Colorimetric evaluation of couscous was carried out in 3 replicates in accordance with the AACC standard method 14-22.01 [16]. The parameters L*, a*, and b* of the CIE-Lab color space (D65/2°) were determined using a 4Wave CR30-16 colorimeter (Planeta, Tychy, Poland). Prior to each measurement session, the colorimeter was calibrated using the manufacturer’s standard white calibration tile (reference standard) and a black calibration plate (zero calibration), as recommended by the manufacturer. This ensured accuracy and repeatability of the color readings. The degree of browning was quantified by the following brownness index (BI) Equation (1):

BI = 100 − L,

(1)

where L is lightness.

2.3.2. Culinary Quality Assessment

Swelling Index

A kinetic study on the swelling of couscous grain was conducted following couscous grain swelling, which was carried out using the method described by Chemache et al. [17]. Samples of 20 g of dry couscous were placed in 200 mL test tubes. A total volume of 100 mL of distilled water was added in two stages, with vigorous stirring between each addition to ensure homogeneous hydration. The samples were then incubated in a thermostatic water bath (Wise bath, WB100-1, Daihan Scientific, Seoul, Republic of Korea) at 25 °C and 95 °C for 60 min. Volumetric measurements were taken at regular time intervals (t = 0, 5, 10, 15, 20, 25, 30, 40, 50, and 60 min). This was performed to monitor swelling kinetics as a function of time and temperature. The swelling index (SI) was determined in triplicate according to the following Equation (2):

SI (%) = [(FV − IV)/IV] × 100,

(2)

where FV is the final volume (mL) of couscous read from the test tube and IV is the initial volume (mL) of dry couscous read from the test tube.

Disintegration Degree

Assessment of couscous disintegration during cooking was carried out in triplicate using a method from Chemache et al. [17], which measures the amount of solids that dissolve in water. For this, 10 g of dry couscous was soaked in 16.5 mL of boiling distilled water mixed with 5 g/L of sodium chloride in saline solution (ACS reagent. J.T. Baker, distributor Avantor Performance Materials Poland SA, Gliwice, Poland). The mixture was then incubated at 90 °C for 12 min in a covered beaker. After incubation, 50 mL of distilled water at 25 °C was added to the couscous, and the whole mass was subjected to continuous stirring for 6 min using a magnetic stirrer. The supernatant, containing solubilized compounds, was separated from the couscous particles by filtration through a 1000 μm sieve. A 10 mL aliquot of the filtrate obtained was taken and dried at 100 °C until weight stabilization. Percentage decay (DD%) was calculated according to the following Equation (3):

DD% = (DR × 10 × 100)/(100 − H),

(3)

where DR represents the mass of the dry residue (g) from the filtrate, and H is the initial water content of the dry couscous (%).

2.3.3. Pasting Properties

The pasting properties of couscous were carried out in 2 replications. A Brabender Micro Visco-Amylo-Graph analyzer (Brabender GmbH & Co. KG, Duisburg, Germany) was used. The pasting properties of ground couscous samples were characterized by following an adaptation of the protocol described by Bouasla et al. [18]. A total of 10 g of each sample was dispersed in 100 mL of distilled water. The pasting properties were evaluated at a constant rotation speed of 250 rpm with a sensitivity of 235 cmg. The temperature profile consisted of heating from 30 to 93 °C at a rate of 7.5 °C/min, holding at 93 °C for 5 min, cooling from 93 to 50 °C at a rate of 7.5 °C/min, and holding at 50 °C for 1 min. Brabender Viscograph software (version 4.1.1) was used to determine pasting properties. The following characteristics were evaluated: viscosity at the start of gelatinization, maximum viscosity, and final viscosity.

2.3.4. Microstructure

To study the surface morphology of couscous grains in detail, scanning electron microscopy was used according to the method described by Agrahar-Murugkar and Dixit-Bajpai [19]. This high-resolution imaging technique involves scanning the sample surface with a focused electron beam. The electron beam interacts with the material, causing it to release secondary electrons, which are then detected and amplified to create a detailed image of the surface’s shape. To prepare the samples, the couscous grains were dried, powdered samples were mounted on aluminum specimen stubs with double-sided adhesive silver tape, and then sprayed with gold using Sputter Coater Emitech K550X (Emitech, Essex, UK) to improve electrical conductivity and avoid electrostatic charges that can degrade image quality. Microstructure observations were made with a Vega Tescan LMU (Tescan, Brno, Czech Republic) working at an accelerating voltage of 20 keV at different magnifications (×200 and ×600). This procedure made it possible to analyze both the general surface characteristics and the details of the grains’ internal microstructure.

2.4. Data Analysis

The data collected were statistically analyzed using Epi Info statistical software (version 7.2, CDC, Atlanta, GA, USA) to identify the traditional process. Study results were expressed as the means of three replicates, with standard deviation (SD) calculated in Excel 2007. Means were compared using a one-factor analysis of variance (ANOVA), followed by a post hoc Fisher minimum significant difference (LSD) test performed with Minitab 19.1.1 software (Minitab Inc., State College, PA, USA). Significance of differences between groups was tested at the p < 0.05 level.

3. Results and Discussion

3.1. Survey Results

3.1.1. Socio-Demographic Profile of Respondents

In the survey carried out in the region of Jijel, Skikda, and Bejaïa, 200 women completed the questionnaire. The characteristics and socio-demographic profiles of the participants are detailed in

Table 1. Socio-demographic profile of the survey population.

Population Surveyed	Number (Percentage%)
Age group
21–39	19 (9.50%)
40–59	162 (81.00%)
60–83	19 (9.50%)
Education level
Lettered	54 (27.00%)
Primary/secondary	111 (55.50%)
University	35 (17.50%)
Activity
Active	42 (21.00%)
Not active	158 (79.00%)
Origin (province)
Jijel	174 (87.00%)
Skikda	17 (8.50%)
Bejaïa	9 (4.50%)
Source of knowledge
Mother	159 (79.50%)
Grandmother	15 (7.50%)
Mother in law	26 (13.00%)

. All respondents demonstrated good knowledge of couscous making and preparation.

The age of the respondents ranged from 21 to 83 and was divided into three categories: under 40 s, 40 s to 59 s, and 60 s and over. Younger manufacturers represented 9.50% of the sample, while the 40–59 age group made up more than three-quarters (81.00%) of respondents. Finally, 9.50% of participants were women aged 60 and above. In terms of education level, the survey results showed that 27% of participants were illiterate, 55.50% had a primary or secondary education, and 17.50% had a university degree. The majority of respondents were housewives (79.50%), while 21% were employed outside the home.

According to this study, couscous originated in the province of Jijel (87.00%). Couscous is mainly passed down from mother to daughter (79.50%), but also from mother-in-law to daughter-in-law (13.00%) and, to a lesser extent, from grandmother to granddaughter (7.50%). Women from Béjaïa and Skikda often learned how to prepare it from their mothers-in-law from the province of Jijel.

3.1.2. Main Stages of Traditional Couscous Production

The couscous manufacturing process, as determined by the survey results (Figure 2), is presented taking into account the proportions of significantly higher responses (p < 0.05).

Raw Materials Preparation

According to the survey results, all respondents (100%) begin the couscous-making process by selecting and classifying the semolina (Figure 2). This process involves separating coarse semolina (>500 µm) from fine semolina (<500 µm) using a sieve with a mesh size of 500 µm. Out of the women interviewed, 25.37% steam the coarse semolina before using it, which matches findings from Benatallah et al. [20] and Chemache et al. [2] for durum wheat couscous. In contrast, 74.63% used the semolina directly without steaming, similar to what Becila et al. [3] found for Lemzeïet couscous.

Fine semolina (<500 µm) was mixed with fermented plant materials. The resulting mixture is called fine mix “dkak”. Traditionally, “dkak” is the name used to designate the mixture of materials smaller than 500 µm. The fermented plant materials included: fine semolina form fermented durum wheat, flour from fermented acorns and flour from fermented sorghum.

The survey identified four types of couscous; each produced from a distinct blend of fermented materials (

Table 2. Traditional couscous formulations.

Couscous	C1	C2	C3	C4
Respondents (%)	48.81	25.60	13.69	10.71
Fermented materials incorporation rates
FA (%)	8	8	6	4
FS (%)	4	0	0.8	0
FW (%)	4	0	0	4
Total incorporation rates (%)	16	8	6.8	8
Wheat semolina incorporation rate
Wheat semolina (%)	84	92	93.2	92
Total formulation (%)	100	100	100	100

C: couscous; FS: fermented sorghum; FW: fermented wheat; FA: fermented acorns.

). The most commonly used blend, reported by 48.81% of respondents, corresponds to type 1 couscous (C1), which contains 4% FS (fermented sorghum), 4% FW (fermented wheat), and 8% FA (fermented acorns). This is followed by type 2 couscous (C2), made by 25.60% of respondents, in which only 8% FA were incorporated. Type 3 couscous (C3) was produced by 13.69% of respondents, with an incorporation rate of 0.8% FS and 6% FA. Finally, type 4 couscous (C4), made by 10.71% of respondents, incorporates 4% FW and 4% FA. According to the results of the survey, the percentage of fermented materials (fermented wheat, acorns, and sorghum) in fine mix (fine durum-wheat semolina, fine semolina from fermented wheat, flour from fermented acorns, and flour from fermented sorghum) does not exceed 16%.

On the other hand, according to the work of Lemzeïet cited by Bekhouche et al. [14], fine mix is composed of 100% fermented wheat. On the other hand, the study by Zohra [21] reported a formulation made with 50% fermented wheat.

In terms of the origin of the fermented acorns, 78.11% of participants buy commercially fermented acorns, while 21.89% use self-fermented acorns. A total of 11.92% of respondents use commercially fermented flour passed through a sieve, while 88.08% use it directly, without prior sieving. Water is used at room temperature (18–25 °C). According to the survey results, 90.53% of women add salt directly to the water, while 9.47% incorporate it into the mixture when preparing fine mix. The introduction of salt into the water modifies its physicochemical properties, particularly the electrostatic charge of the particles and the surface characteristics of the water, such as surface tension and contact angle. These changes favor the agglomeration of semolina. Salt also helps to improve the preservation and sensory profile of couscous, notably by enhancing its taste [2].

Humidification

A calibrated granulometric fraction of durum wheat semolina, characterized by particles with a size greater than 500 µm, is introduced into a large wooden container. Hydration is initiated by the progressive addition of salt water (at a concentration of 1.5%), ensuring even distribution of the liquid by manual mixing. Controlling the amount of water added is crucial to inhibit the formation of pasty masses, in line with the results of studies by Chemache [22] and Becila et al. [3]. This hydration process induces the formation of a hydrogel around each semolina particle. This occurs because the semolina ingredients, particularly starches and proteins, absorb water, causing them to expand and form a stretchy, gel-like structure [23].

Grain Formation (Rolling and Grading)

The results showed that making couscous grains involved several steps: mixing and breaking apart, then two different rolling stages, each followed by sizing. This sequence is broadly in line with the work of Chemache [22] and Benatallah [24] regarding durum wheat couscous. However, there is a discrepancy with the study by Zohra et al. [21] of Lemzeïet couscous, which carried out mixing and first rolling consecutively, without an intermediate disaggregation phase.

Once the hydrogel is formed around the coarse semolina particles, a controlled mixture of fine mix and salted water is gradually added in a mass ratio of 200/100 g/g: fine mix/water. Each addition is followed by gentle manual mixing using the fingertips to ensure even dispersion of the ingredients. This important step initiates the wet agglomeration process, leading to the formation of the first aggregated structures called nuclei, and then coalescence occurs, where fine mix particles stick to wet semolina particles, helping the clumps grow [25].

A total of 64% of those surveyed perform a sieving step to break up the lumps formed. This mechanical process breaks up the lumps by forcing them through the mesh of a 1280 µm sieve. For wheat couscous, the study by Benatallah et al. [20] used the same sieve (1280 µm), while the study by Chemache et al. [2] used a sieve with mesh sizes ranging from 2860 to 3300 µm. The concomitant addition of the flour mixture at this stage plays an essential role in controlling lump cohesion. By dispersing between the particles, the flours help reduce the forces of inter-particle attraction. This action improves sieving efficiency by facilitating the passage of particles through the mesh and optimizing the disaggregation process.

The mixture of flours and salt water is added again. The subsequent rolling step is performed using the flat of the hands, applying light pressure to the particles in an arched back-and-forth motion. Following calibration (sieve 1130 µm), a second rolling operation is performed. This time, stronger pressure is applied with the flat of the hands in a repeated back-and-forth movement to structure and homogenize the particles. Once the wet agglomerates are homogeneous, rolling stops. The wet couscous agglomerates are then calibrated (sieve 1000 µm) to obtain a homogeneous particle size. Residual non-agglomerated particles are isolated using a sieve (500 µm), then reintroduced into the next rolling process.

Finishing

The finishing stage, which involves rolling the wet couscous grains and incorporating texturizing agents to even out their grain size and improve final texture, has been described in the work of Chemache et al. [2] in the context of durum wheat couscous and by Becila et al. [3] for Lemzeïet couscous. However, the results of our study show that this practice is not widespread: a significant proportion of participants (58.52%) do not carry out this step. Among the 41.48% who do, the texturizing agents used vary considerably: soft wheat flour is preferred by 18.52% of respondents, followed by starch (16.30%) and durum wheat fine semolina (6.67%).

Pre-Cooking Couscous

When intended for storage, all respondents (100%) reported precooking couscous by steaming. Of these, 61.54% continue cooking until a soft texture is obtained, 23.07% adjust the cooking time to between 10 and 15 min, and 15.38% prolong cooking until a marked increase in steam production is observed. Pre-steaming is an essential step in consolidating the structure of moist grains. This process leads to significant biochemical changes, including starch gelatinization, protein cross-linking, and the formation of amylose-lipid complexes. These transformations promote particle cohesion by acting as binding agents [5,26].

Once the couscous had cooled, granulometric calibration was carried out using a sieve with a 1280 µm mesh opening. The primary aim of this operation is to prevent coalescence of the couscous grains. This practice is consistent with findings of Benatallah [24], who also employed a 1280 µm sieve for this stage. Chemache et al. [2] further specified that the sieve used must allow all couscous grains to pass through.

Drying

Precooked couscous is then air-dried in a thin layer. Among the respondents, 34.94% reported drying it in the shade, 60.24% in direct sunlight, and 4.82% used a combined method. Drying continues until a hard couscous is obtained, thus guaranteeing the physicochemical and microbiological stability of the couscous grains. Finally, the dried couscous is checked on a 500 µm sieve to remove any fine, non-agglomerated particles, then packed in canvas bags, as reported by 86% of respondents, and stored in a dry place at room temperature.

3.2. Characteristics of Manufactured Couscous

3.2.1. Color Parameters Results

The values of the colorimetric parameters of the different manufactured couscous are presented in

Table 3. The color profile of manufactured couscous.

Couscous	C1	C2	C3	C4
Color Parameters
L*	60.66 ± 0.90 c	63.12 ± 0.89 b	70.36 ± 1.49 a	63.55 ± 0.67 b
a*	5.80 ± 0.13 a	5.25 ± 0.06 b	4.86 ± 0.17 c	5.68 ± 0.10 a
b*	10.42 ± 0.35 d	10.84 ± 0.43 c	16.03 ± 0.36 a	11.86 ± 0.28 b
BI	39.34 a	36.88 b	29.64 d	36.45 c

C: couscous; L*: lightness; a*: red pigmentation; b*: yellow pigmentation; BI: browning index. Letters ^a–d indicate significant differences for values on the same line at a 0.05 level.

.

The color profile of the tested couscous (Table 3) represents a determining quality criterion influencing consumer acceptability and preferences [27,28]. In general, all manufactured couscous exhibited high brightness L*, ranging from 60.66 for C1 to 70.36 for C3 (p < 0.05). A low yellowing index b* was observed for all couscous (from 10.42 for C1 to 16.03 for C3) and low values for red pigmentation a* (from 4.86 for C3 to 5.80 for C1). The browning index (BI) ranged from 29.64 for C3 to 39.34 for C1. Belmouloud et al. [13] evaluated the color of fermented sorghum and acorns. The results indicated high L* parameters for both flours (FA and FS values were 62.25 and 71.54, respectively).

The elevated browning index observed in the C1, C2, and C3 couscous samples can be attributed to the proportion of fermented wheat and acorns incorporated. This browning happens because phenolic compounds undergo a chemical change, creating brown pigments called ortho-quinones during fermentation [21]. Although couscous made from fermented materials is appreciated for its brown color [7,21], the C1 sample (FSF, FWS, and FAF) presents a particularly prized color.

The results obtained for the colorimetric profile of the different couscous formulas are consistent with consumer sensory expectations, as color represents a key element of visual appeal and product acceptability. The preference for C1, with its darker, brown hue, reflects consumers’ association of this color with authenticity, cultural tradition, and the sensory characteristics expected of fermented products. Similar findings have been reported in other studies on fermented cereal-based foods, where brownish tones were linked to perceptions of richer aroma, superior nutritional value, and greater overall acceptability [29]. This alignment confirms that the color attributes of fermented couscous play a crucial role in meeting consumer sensory expectations, in agreement with previous observations in comparable research.

The survey results reveal that the most commonly used formulation is type 1 couscous (C1), adopted by 48.81% of respondents. This formulation is distinguished by its high fermented material content (16%), which gives it a more pronounced acidity than other types. Instrumental analyses indicate that sample C1 (formulated with FSF, FWS, and FAF) also has the highest browning index value, reflecting a brown color that is particularly appreciated by consumers [7,21]. Although formulations C3 and C4 showed the highest swelling indices, indicating better absorption of sauces and therefore a softer, more desirable texture, consumer preferences seem to be mainly influenced by the brown color and tangy flavor characteristic of fermented couscous.

3.2.2. Culinary Quality Results

Swelling Index Results

The effect of temperature (25 °C and 95 °C) on the swelling index of the different couscous formulations is illustrated in Figure 3. The study of the swelling kinetics of the couscous samples revealed distinct behaviors as a function of temperature. All samples reached an equilibrium swelling state at 25 °C (Figure 3a) after 20 min, with swelling indices ranging from 104.71 to 131.11%. Raising the temperature to 95 °C resulted in an increase in the swelling indices for the four couscous samples studied (Figure 3b). Under these conditions of temperature, swelling stabilization was observed after 15 min, with swelling index values ranging from 139.41 to 165.55%.

Comparison with published data on durum wheat couscous reveals variations in SI according to the formulations. At 25 °C, the four formulations studied have higher SI than those reported by Benatallah [24] but lower than those observed by Chemache et al. [17]. At 95 °C, a formulation C2 has a swelling index similar to that of Benatallah et al. [20], while C3 and C4 have higher swelling indices, and C1 has a lower SI. The drop in the swelling index might be linked to the rise in the amount of gluten-free flours in the couscous formulations (acorn and sorghum), as a higher swelling index tends to happen when there is less of it.

The swelling index is a key indicator of couscous quality. High-quality couscous is characterized by its strong ability to swell and effectively absorb sauces. This ability, crucial for its culinary quality, is influenced by the nature of the raw materials used during its manufacturing [30,31]. The swelling index is affected by several factors, including starch, which is the main part of flours and is made up of amylose (straight chains) and amylopectin (branching chains) arranged in granules. The amount of these two components changes depending on the type of plant and directly affects the swelling index. A high starch content, particularly amylopectin fractions, promotes a higher swelling index. The swelling index also reflects the intensity of non-covalent bonds within the starch granules [32]. Other factors, such as the size of the flour particles, the type of plant used, how the plant material is processed, and the presence of non-starch substances like fats and proteins, affect how starch interacts with water and, as a result, its swelling properties [33,34,35].

In the case of couscous, different formulations and flour blends have a significant impact on the swelling index. The mixture of various flours can result in synergistic interactions (increase in the swelling index) or antagonistic interactions (decrease in the swelling index) during cooking. The study suggests that mixtures of fermented acorns/fermented sorghum (C3) and fermented acorns/fermented wheat (C4) may form a looser network and retain more water compared to fermented acorns alone (C2). Conversely, the mixture of fermented acorns/fermented sorghum/fermented wheat (C1) seems to have the lowest swelling index.

Disintegration Degree Results

The disintegration degree values for the four couscous formulations are presented in Figure 4. Cooking loss is mainly attributed to the dissolution and release of gelatinized starches from the surface of the couscous grains into the cooking water [31].

The disintegration degree (DD), expressed as a percentage of released components into water, was evaluated and varies between 3.27% and 5.20%. The disintegration degree (DD) increased significantly (p < 0.05) with the level of incorporation of fermented acorn flour. The incorporation of 8% fermented acorn flour (C1) resulted in the highest DD value (p < 0.05), reaching 5.2%.

The other combinations present the following values: C2 (8% fermented acorns)—3.96%, C3 (6% fermented acorns)—3.43%, and C4 (4% fermented acorns)—3.27%. These results remain lower than those reported by Zohra [21] for couscous with fermented wheat. It should be noted that the combination of fermented acorn flour and fermented wheat in sample C4 resulted in a decrease in DD, while the combination of three materials (fermented acorns, wheat, and sorghum) in sample C1 resulted in the highest DD values. It should be noted that the lowest percentage of fermented acorns in combination with 4% fermented wheat resulted in the lowest DD (C4), while the addition of fermented sorghum in C1 with an increased percentage of fermented acorns gave the highest DD. During heating, couscous grains absorb water. The heat allows the starch granules to swell and gelatinize. The granules release the more mobile amylose, which then diffuses into the cooking water.

Disintegration may be directly associated with the release of amylose. When amylose leaches out of the starch granules, the structural integrity of the couscous grains is compromised, making them more susceptible to disintegration [24]. High-quality couscous should exhibit low disintegration [22]. Furthermore, sample C1, which had the highest incorporation rate of gluten-free flours (16%), exhibited the highest degree of disintegration. It is widely known that the increase in the degree of disintegration can result from a reduction in gluten content, leading to a decrease in the cohesion forces between couscous particles, making them more fragile [26].

3.2.3. Pasting Properties Results

The viscoamylographic test was used to provide information about the starchy components’ behavior after the couscous was made. The results are illustrated in

Table 4. Pasting properties of couscous.

Couscous	C1	C2	C3	C4
Initial Viscosity (mPas)	15.60 ± 0.32 d	24.00 ± 0.50 c	25.00 ± 0.00 b	27.00 ± 0.00 a
Maximum Viscosity (mPas)	24.20 ± 0.39 d	26.00 ± 1.50 c	31.00 ± 0.50 a	30.00 ± 1.86 b
Final Viscosity (mPas)	37.00 ± 1.60 d	40.00 ± 0.00 c	49.00 ± 1.20 a	46.00 ± 3.00 b

C1: couscous with fermented sorghum, fermented wheat, and fermented acorns; C2: couscous with fermented acorns; C3: couscous with fermented sorghum and fermented acorns; and C4: couscous with fermented wheat and fermented acorns. The letters ^a–d indicate significant differences for values in the same row at a 0.05 level.

. The initial viscosity of the different types of couscous ranged between 15.60 and 27.00 mPas, reflecting a partial gelatinization of the starch granules in all formulations. Among the samples studied, couscous made from fermented acorns and wheat (C4) has the highest initial viscosity (27.00 mPas), followed by couscous made from fermented acorns and sorghum (C3) (25.00 mPas), and then couscous made from fermented acorns (C2) (24.00 mPas). The couscous made from fermented sorghum, wheat, and acorns (C1) has the lowest (p < 0.05) initial viscosity (15.60 mPas). A high initial viscosity of the couscous is a sure sign of excellent water absorption during the first cooking stage, leading to the ideal expansion of the starch granules. This observation is corroborated by the swelling index results, obtained at 25 °C and 95 °C, which place samples C3 and C4 in first place, followed by C2 and C1, in line with their initial viscosity. The presence of more damaged starch in dry couscous facilitates rapid water absorption. This property favors rapid expansion of starch granules, leading to starch gelatinization at rather low temperatures [18].

Maximum viscosity indicates the optimal swelling of starch granules [36]. As it cools, amylose molecules that come out of the starch granules stick together, creating a thick mixture and raising the final viscosity [37]. Although this increase was observed for all couscous samples, between the maximum viscosity (between 24.20 and 31.00 mPas) and the final viscosity (between 37.00 and 49.00 mPas), the couscous made from fermented acorns and sorghum (C3) has the highest (p < 0.05) value (31.00 and 49.00 mPas for maximum and final viscosity, respectively), followed by couscous made from fermented acorns and wheat (C4) (with 30 and 46 mPas for maximum and final viscosity, respectively). The couscous incorporating fermented acorn flour (C2) ranked third with 26.00 and 41.00 mPas for maximum and final viscosity, respectively. Finally, the couscous C1, incorporating three fermented materials, presents the lowest values, with 24.20 and 37.00 mPas for maximum and final viscosity, respectively. The couscous viscosity values remain low compared with the viscosity reported by Belmouloud et al. [13] for fermented flours (266, 255, and 314 mPas for FAF, FSF, and FWS, respectively).

The succession of several stages accounts for this difference. Pre-cooking is an important step that induces partial starch gelatinization. Specifically, the hydration and swelling of starch granules during pre-cooking leads to the release of amylose and amylopectin. Extensive pre-cooking can promote amylose retrogradation, thereby increasing the starch’s crystalline structure. In addition, the grinding of couscous grains after drying, prior to viscosity analysis, probably contributed to a reduction in viscosity through the breaking of starch chains. This observation is consistent with the results of Hayes et al. [38]. The observed decrease in viscosity has direct implications for simulated gastric emptying. Indeed, low viscosity is associated with moderate emptying speed [38], suggesting a more gradual digestion for C1 couscous.

3.2.4. Microstructure of Couscous

The external microstructure and surface texture of the couscous grains from different formulations were analyzed using scanning electron microscopy (SEM), as shown in Figure 5. The results show that the microstructure varies according to the proportion and type of fermented materials added. Couscous grains produced from three fermented starchy flours in sample C1—fermented acorn (8%), fermented sorghum (4%), and fermented wheat (4%)—exhibited a regular and smooth microstructure. Here, the native particles of the starchy powders were no longer discernible, making the grain structure very dense, with reduced or even imperceptible porosity. However, this visual compactness observed under SEM may reflect a surface densification rather than effective internal gelatinization, which aligns with the functional properties showing the highest loss of components and the lowest viscosity values.

A close look (×600) at the surface of the agglomerates showed that there were regular and smooth areas interspersed with a few intact starch granules, with diameters ranging from 13.51 to 34.05 µm. This dimensional heterogeneity suggests the involvement of three distinct botanical sources, each characterized by specific morphological and dimensional properties as described in the literature. Sorghum starch granules are described as having polygonal, irregular, angular, and spherical shapes, with dimensions ranging from 5 to 30 µm [39]. The presence of granules within this dimensional range in our sample supports the hypothesis of a partial origin from fermented sorghum starch.

Additionally, acorn starch exhibits granules that are mostly spherical, elliptical, or irregular, characterized by smooth and crack-free surfaces. These granules vary significantly in size, from 3.3 to 126.2 µm [35]. The detection of large granules, particularly those exceeding 30 µm in sample C1, could reflect acorn starch that has undergone a fermentation process. The particle size distribution, characterized by narrower diameters compared to unfermented starch, could result from this biochemical transformation [40]. Finally, durum wheat starch is known for its predominantly spherical granules, with sizes ranging from 1 to 20 µm [5]. The presence of granules located in the lower part of our particle size distribution (close to 13.51 µm) could thus be attributed to durum wheat starch.

When couscous has been enriched with 8% of fermented acorn flour (C2), it exhibits a microstructure characterized by native durum semolina and acorn flour particles that are interconnected but still visible and identifiable. This configuration appears to have created an open porosity at the grain surfaces. The resulting image showed that the semolina and flour components—primarily proteins and starch—have been partially gelatinized. At higher magnification (×600), smooth areas with a melted structure appearance can be seen. Some slightly gelatinized starch granules remain visible, while others, still intact, show sharp contours. The starch granules have a diameter of 23.67–28.72 µm, which could indicate an origin from fermented acorn flour. Taib and Bouyazza [35] reported that acorn starch has a considerably wider diameter range, ranging from 3.3 to 126.2 µm, and a variety of morphologies, including irregular, elliptical, and spherical shapes. The fermenting process might be the cause of the smaller diameters seen in our samples.

The addition of a mixture of fermented acorns and sorghum (C3) at 6% and 0.8%, respectively, resulted in couscous agglomerates formed by the association of particles adhering to each other. Some small native particles remain and give a granular roughness. However, at ×600 magnification, a dense network of fused proteins coming from durum semolina (in this sample, the total amount of gluten-rich wheat was the highest) can be seen enclosing swollen or gelatinized starch granules that have lost their natural structure. The production of couscous depends largely on the functional properties of starch, particularly its ability to absorb water and gelatinize [5]. According to Yang et al. [41], during thermal treatment, protein fractions, especially those from sorghum, can unfold and contribute to the formation of a three-dimensional protein network capable of retaining water, enhancing cross-linking through disulfide bonds. In the case of C3, this phenomenon appears to have promoted the formation of a coherent starch–gluten matrix, as seen in the lower regions of the granule in Figure 5. These observations about the tiny structure match the highest viscosity values seen for this sample, which might show that a stable and stretchy protein-starch network was created during heating. The slight surface roughness could be attributed to localized incomplete fusion or the presence of residual particles, but overall, the internal structure appears to be well-formed and functionally cohesive. Proteins’ ability to retain water interferes with starch’s ability to gelatinize [41,42]. This phenomenon is exacerbated by the functional properties of sorghum flours. Belmouloud et al. [13] reported low swelling and viscosity capacities for these flours, which indicate that these flours do not absorb much water and have low thickness. This is due to their slow water absorption and the weak connections between protein and starch. Consequently, the texture of couscous made with addition of fermented sorghum flours (0.8%) with reduced starch gelatinization inhibits the formation of a smooth and homogeneous structure, accentuating the rough and irregular surface of the couscous grains.

Finally, the grains in couscous enriched with a mixture of 4% fermented wheat and 4% fermented acorns, designated as C4, displayed a more fused and denser microstructure, with agglutination areas and less porosity. However, the surface still showed roughness and scattered areas in some places, with few singular starch grains visible imbedded in the melted mass. In the C4 sample, the amount of components leaching to water during preparation was the lowest, and the results may be explained by the consistent structure of this type of couscous due to increased gelatinization. Furthermore, fermentation is known to modify the structure of starch by increasing its water absorption capacity and water solubility index through mechanisms such as enzymatic hydrolysis, loss of crystallinity, and exposure of hydrophilic groups. These changes promote more efficient water uptake and swelling during cooking. Additionally, the presence of fermented wheat proteins likely contributed to better matrix cohesion and may have contributed to a more homogeneous structure, reflecting a higher degree of starch gelatinization specific to the C4 composition. This gelatinization reduces the proportion of starch granules that have escaped this process.

The traditional method of making couscous, which involves manually rolling semolina with water and salt to form grains, followed by sieving, pre-cooking with steam, and drying, can be transferred to industrial production by mechanizing and automating each phase. This involves the use of industrial granulators for rolling, vibrating sieves for calibration, continuous steam cookers for pre-cooking, and industrial hot air dryers for final drying, all under rigorous quality control to ensure consistent particle size, texture, and moisture content, thereby replicating artisanal expertise on a large scale while guaranteeing hygiene and efficiency.

4. Conclusions

The production of couscous enriched with fermented acorns, sorghum, and wheat goes through a series of transformations, including hydration of semolina and flours, agglomeration, calibration, pre-cooking, and drying and storage. Four main types of couscous were developed by partially substituting durum wheat semolina with various fermented flours: C1 uses fermented sorghum flour, fermented wheat, and fermented acorns; C2 uses only fermented acorn flour; C3 combines fermented sorghum flour and fermented acorns; and C4 mixes fermented wheat semolina with fermented acorns. The incorporation of these materials modified the physicochemical properties and microstructural characteristics of couscous. Although some formulations improved specific aspects such as color (C1) or swelling index and viscosity in C3 and C4, they can also negatively affect porosity (C1). Formulas rich in mixtures of fermented materials tend to reduce porosity while increasing antiparticle cohesion. Additionally, the incorporation of fermented acorn and wheat flours (C4) was found to promote a smoother and denser texture, whereas the addition of fermented sorghum (C3) appeared to accentuate the roughness and unevenness of the couscous grains. The experimental reproduction of couscous enriched with fermented wheat, sorghum, and acorns has shown that traditional ways of making it can still work and that the final quality of the couscous can be assessed. This approach also helps to preserve the valuable fermented foods derived from ancestral practices. In addition, this research highlighted the benefits of utilizing naturally fermented raw materials in the production of affordable goods for consumers, as well as the adoption of effective agro-ecological practices to increase the incomes of small local farmers. In the future, it will be essential to gather data on food safety and the regulatory and economic viability of fermented materials as an emerging natural and functional ingredient to develop a diverse range of new food products.