Introduction

In West Africa, fermented foods form an important part of the diet, and are often referred to as traditional foods due to the fact that their preparation dates back to prehistoric times1. Traditional food fermentation improves nutritional characteristics of dishes, through changes in aroma, flavor and texture2. Fermented seeds constitute significant low cost sources of protein foods in some parts of the world3. Because of their sensory characteristics and high nutritional value, they are used as flavor-enhancing condiments or as substitutes for fish and meat in food2,4. Many fermented condiments are found in Burkina Faso such as Maari (fermented seeds of Adansonia digitata), Bikalga (fermented seeds of Hibiscus sabdariffa), Mantchoua (fermented seeds of Ceiba pentandra) and Soumbala (fermented seeds of Parkia biglobosa)5,6. Among them, Soumbala is the best-known and most popular condiment in West Africa, precisely in Burkina Faso2,4,7,8. Also, fermented Zamné is one of these fermented food condiments obtained by processing and fermentation of Senegalia macrostachya seeds, found in the central region of Burkina Faso9,10. According to Guissou et al.10, fermented Zamné had physico-chemical (pH) and microbiological characteristics and nutritional composition similar to soumbala. Fermented Zamné is rich in protein (48.91 ± 0.74 g/100 g DM), potassium and magnesium (1076.74 ± 37.49 mg/100 g DM and 111.63 ± 06 mg/100 g DM respectively), with an appreciable iron content (26.27 ± 0.06 mg/100 g DM)10. However, little information is known about the Sensory properties of fermented Zamné. In fact, the lack of adequate knowledge of the culinary and sensory properties of most indigenous foods hampers their promotion in human diets11. The aim of the present study was to test the acceptability of fermented Zamné in comparison with soumbala.

Materials and methods

Products

Zamné (Senegalia macrostachya) seeds and fresh Soumbala (Soumbala market) were purchased at Naabi-yaré, a local market in Ouagadougou. Soumbala market is produced by the traditional process involving first boiling for 24 h before dehulling12. Mature and dry seeds of Parkia biglobosa were harvested from Péni, Nobéré and Louda, three localities in Burkina Faso10. The seeds were then dehulled with a dehulling machine (Departement de Mechanisation, IRSAT, CNRST, Ouagadougou, Burkina Faso). The Dehulling in the process of production of Soumbala considerably decreased the first boiling step from 24 to 6 h12. The samples were analyzed fresh, dry and in broths. Fresh and dry products were evaluated, because the characteristics can change with drying, and some consumers prefer the fresh product, which has specific characteristics. Dry form is better for preservation and/or marketing. For broths, this form was used because fermented condiments are used as seasoning for sauces and dishes. The aim here was to detect the presence of the condiment in the broth.

Fermented seeds processes

The production of the fermented seeds was carried out in workshop-pilot of Department of Food Technologies10. For each type of seed, two productions trials were carried out, and each trial consisted of two parallel fermentations. For the production of soumbala (soumbala DTA), the dehulled and cleaned seeds of Parkia biglobosa were cooked for 6 h, drained, washed, cooked a second time for 30 min with addition of potash (1%). Cooked seeds were then drained and left to fermented naturally at room temperature. Fermentation takes place in fermentation tun for 48 h, fermented seeds were further sun dried for 72 h.

Concerning the production of fermented Zamné, the cleaned seeds were cooked a first time for 30 min, drained and washed. These are then cooked a second time for 30 min with addition of potash (1%), drained, inoculated with soumbala (2%) and left to fermented at room temperature in fermentation tun for 48 h. Finally, the resulting product was sun dried for 72 h.

Broths production

The broths were prepared with a dose of fermented condiments as described by Sawadogo-Lingani (2004) in her study13. Broths were used in this study, because it is a simple prepared dish, with few ingredients. This allow a better perception of fermented condiments characteristics. In fact, many others showed that fermented condiments are largely used to enhance the flavour of many dishes including soups, sauces and stews3,14,15. To prepare the broths, beef (2 kg) was cooked in water (5 L) with onions and salt as condiments. The meat was removed at the end of cooking and the broth was divided into 04 parts. The first part was the control broth (without condiment), the second part was mixed with fermented Zamné, the third part with Soumbala DTA and the last part with Soumbala market. Raw Zamné (Senegalia macrostachya) seeds, dehulled seeds of Parkia biglobosa and the samples are ullustrated in Fig. 1.

Fig. 1
figure 1

Analysis samples. (a) Raw Zamné (Senegalia macrostachya) seeds; (b) dehulled raw seeds of Parkia biglobosa; (c) Fermented zamné; (d) Soumbala produced at DTA; (e) Soumbala purchased at the market; (f) powder of Fermented seeds (1—Fermented zamné, 2—Soumbala produced at the DTA, 3—Soumbala purchased at the market); (g) Broths (1—with fermented zamné, 2—with Soumbala produced at the DTA, 3—with Soumbala purchased at the market, 4—control).

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Analysis methods

Ethical clearance and recruitment of participants

This study was approved on August 2nd, 2024 by the ethics committee for health-related research of the Health Ministry of Burkina Faso, clearance number: 2024-05-143. The study participants for the sensory test were drawn from a trained panel of professionals in the production and analysis of soumbala, staff from the Food Technology Department and students from Ouagadougou universities, all of whom were experienced in carrying out sensory analyses. All methods were carried out in accordance with the sensory analysis methods according to test type. Informed consent was obtained from all the participants (age > 18 years) involved in the study.

Sensory analysis

Four (04) test were retained for the sensory analysis, namely the sensory profile, the hedonic test, the ranking test, and the difference test. These tests were carried out at the sensory analysis laboratory of Department of Food Technology (Institute of Research in Applied Sciences and Technologies, Burkina Faso), and all methods were performed in accordance with the relevant guidelines and regulations. The panel of consumers was determined according to the number of samples.

Sensory profil (properties) were evaluated according to ISO 1103516. Only fermented Zamné was subjected to this test. The aim was to describe the new product and give it an identity. The panel of tasters was a trained panel, composed of 07 professionals involved in soumbala production and 12 researchers from the Department of Food Technology who are regular attendance at sessions of tasting fermented condiments. The minimum required is respectively 18 and 24. The definition of sensory descriptors were given in Table 1. The descriptor is a term that refers the subject to an element of product perception that can be evaluated on an intensity scale17.

Table 1 Scales of sensory descriptors.
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Hedonic tests and ranking tests were conducted at the same time. Both flyers were given with the same samples. Tasters were asked to rank the samples at the end of hedonic tests. Hedonic tests are designed to measure degree of liking for a product by choosing the appropriate category. Ranking tests require panelists to order samples according to the perceived intensity of a sensory characteristic17. All samples were subjected to this test. The 03 fresh condiment (fermented Zamné, Soumbala DTA, and Soumbala market) were served together on the same plate; the 03 powder of dry condiments together and the 03 broth with the control. The sensory panel was composed of 43 volunteers (professionals involved in soumbala, students from University Joseph Ki-Zerbo, and personnel from the Department of Food Technology). Hedonic and ranking scales were given in Table 1.

Difference tests are designed to determine whether two samples can be distinguished from each other by sensory analysis (appearance, flavour, texture)17. In this study, difference tests were conducted as a culinary test according to the method described by Sawadogo-Lingani13. This test consisted in preparing a broth with a dose of fermented condiments. These broths were then evaluated by the tasters. The 04 samples were submitted at the same time to the tasters, who compared them 02 by 02 (with the control broth), saying whether they were identical or different on the basis of taste, odour and color. The sensory panel was composed of 43 volunteers (professionals involved in soumbala, students from University Joseph Ki-Zerbo, and personnel from the Department of Food Technology). The scales were given in Table 1.

Samples were coded using a three (03) digit code, and the same quantities of samples were presented in identical bowls17,18. A tablespoonful of each sample was served in a coded bowl, and the bowls bearing different codes were placed on plate and served to each taster together with a pen, some mineral water (to rinse their mouths between the evaluations of the different products), and the flyer. Also, samples were arranged and presented in different combinations. Each panelist received the flyer with a precise order code numbers. The panelists were instructed to evaluate samples in the order indicated on the flyer17. A space on the flyer was given to the participants to provide any additional remarks.

Determining color values (L*, a*, b*)

The color parameter values of different Samples (powder) of fermented Zamné, Soumbala DTA and Soumbala market were determined using a colorimeter (PCECSM 3, PCE instruments, I’m Langel 4, D-59872 Meschede, Deutschland) based on the color system of the International Commission on Illumination (CIELAB): L*, a*, b* and C*, h. The parameters lightness (L*), redness (a*) and yellowness (b*) were measured in triplicates for each sample by placing the objective of the colorimeter on a homogeneous surface of the products.The hue component (h*) represents a true color, 0° is red, 60° is yellow, 120° is green, 180° is cyan, 240° is blue, and 300° is magenta according to the classical layout19.

Statistical analysis

The data were collected using Microsoft Excel 2019. Analysis of variance (ANOVA) was performed using XLSTAT 2016.02.27444 to study the degree of difference between the variables17. In the event of a significant difference between the parameters studied, the classification of the means (homogeneous groups) was carried out using Tukey’s test at a significance level (α) of 0.05. Statistical differences with a probability value of less than 0.05 were considered significant. All analyses were performed in three replicates.

Results and discussion

Panel composition

The Table 2 summarizes the panel’s composition. The sensory panel was composed of 19 tasters (females and males) for sensory profile, and 43 tasters females and males, aged from 15 to over 40 for the other tests.

Table 2 Panel composition.
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Sensory profile of fermented Zamné

The sensory profile of fresh fermented Zamné is summarized in Table 3. According to the panel, the color of fermented Zamné is dark-brown (75% of the panel). it is characterized by a strong smell (41.7%) and an alkaline taste (58.3%). The texture is appreciated “not sticky” (75% of the panel), with no whitish coating (75% of the panel); for some tasters, a good soumbala should have this whitish color. A statistically significant difference is observed between the different assessments.

Table 3 Sensory profile of fermented Zamné.
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Results of hedonic tests and ranking of fermented condiments

The results of the hedonic test are presented in Table 4 (fresh condiments) and Table 5 (dry condiments). Concerning fresh condiments, the color of fresh fermented Zamné scored lower (2.27) than those of Soumbala. Fermented Zamné was less appreciated by the tasters for all parameters. Thus, they were ranked third with a score of 2.54 behind Soumbala labo (2.04) and market soumbala (1.54).

Table 4 Hedonic profile and ranking of fresh samples.
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Table 5 Hedonic profile and ranking of dry products.
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For dry condiments (Table 5), dry fermented Zamné scored poorly (2.29) against Soumbala market (1.61) and Soumbala DTA (1.48) concerning color. Similar results were obtained for texture, dry fermented Zamné scored poorly (2.29) against dry soumbala market (1.65) and dry Soumbala DTA (1.62). With a score of 2.45, the odor of dry fermented Zamné was less appreciated than those of Soumbala market (1.48) and Soumbala DTA (2.13). The taste was appreciated in a similar way, the dry fermented Zamné obtained a low score (2.48) compared to soumbala DTA (2) and soumbala market (1.42). The fermented Zamné was ranked third with a score of 2.77 behind soumbala DTA (2.1) and soumbala market (1.13). A statistically significant difference was observed between the color and texture of dry fermented Zamné and those of dry Soumbala market and dry soumbala DTA. A statistically significant difference was observed between the three samples for the rest of the parameters evaluated. The panel found its characteristics very different from those of soumbala.

Results of hedonic tests and ranking of broths

The results of the hedonic profile of broths are showed in Table 6. The control broth (without condiment) scored poorly (2.59) against broths seasoned with fermented Zamné (2.41), soumbala DTA (1.76) and soumbala market (1.72) for color. Similar results were obtained for smell, texture, taste and rank. The three fermented condiments performed better than the control broth for all the parameters. There was no significant difference in likeness for the color, the smell, the texture and the taste of control broth and the broths seasoned with fermented Zamné. Concerning rank, broth prepared using fermented Zamné performed better than control broth, with a significant difference.

Table 6 Hedonic profile and ranking of fermented condiments in broths.
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Figure 2 shows the results of the difference test (a: Taste; b: Smell; c: Color). Concerning the difference test, the three broths with condiments differed from the control broth for all the analyzed parameters. These differences vary in degree according to product and parameter, although an overlap in appreciation is observed (no statistically significant difference). Broth seasoned with fermented Zamné is different from control broth on the basis of taste (42.3% of the panel), and extremely different on the basis of smell (34.6% of the panel) and color (42.3% of the panel). Broth seasoned with Soumbala market is different (30.8% of the panel) from contol broth on the basis of taste and very different on the basis of smell (30.8% of the panel) and color (42.3% of the panel). Broth seasoned with Soumbala DTA is very different (30.8% of the panel) from control broth on the basis of taste and color (38.5% of the panel) and different on the basis of smell (34.6% of the panel).

Fig. 2
figure 2

Difference test with control results (a: Taste; b: Odour; c: Color).

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Figure 3 shows the PCA biplot of fresh condiments, dry condiments and broths seasoned with fermented condiments in relation to sensory characteristics, with 94.83% representativeness on axes 1 and 2. Samples are grouped by product type, whatever their condition. All parameters (color, texture, taste, smell) were used to assess fermented Zamné. The assessment of Soumbala market focused more on color and texture. Taste and smell were the parameters that most influenced the assessment of Soumbala DTA.

Fig. 3
figure 3

PCA biplot of fresh, dry and broths seasoned with fermented condiments in relation to sensory characteristics.

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There was also a positive correlation between the various parameters (Table 7). A strong correlation was observed between taste and smell (0.946), with texture and color (0.937) being the most important. The high correlation between rank and smell (0.88) and between rank and taste (0.85) indicates that sample ranking is based primarily on product smell and taste; texture and color being secondary parameters). Indeed, according to Appiah et al.15, aroma, which consists of taste and smell, is the most important predictor of the acceptability of fermented condiments.

Table 7 Correlation between different analysis parameters.
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Color parameters of fermented seed powder samples of Senegalia macrostachya and Parkia biglobosa

The results of the color parameters of fermented seed powder samples are presented in Table 8.

Table 8 Color parameters of fermented seed powder samples of Senegalia macrostachya and Parkia biglobosa.
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The results of instrumental analysis of color of samples (Table 8) ranged from 21.84 ± 0.01 to 22.31 ± 1.15 for L* for fermented Zamné powerd and Soumbala Market powder respectively without significant difference; from − 0.18 ± 0.01 to − 0.58 ± 0.08 for a*, for Fermented Zamné powerd and Soumbala Market Powder, respectively with significant difference; from − 1.27 ± 0.12 to − 1.48 ± 0.18 for b* for Soumbala DTA Powder and Market Soumbala powder, respectively; from 1.44 ± 0.04 to 1.56 ± 0.12, for C* for Market Soumbala powder and the other two, respectively without significant difference; from 246.33 ± 0.82 to 252.35 ± 0.82 for h* for fermented Zamné powder and Soumbala DTA powder, respectively without significant difference. The color difference value (a/b*) of the samples is from 0.33 ± 0.11 to 0.94 ± 0.01 for Soumbala Market powder and for Soumbala DTA powder with a significant difference.

Discussion

The difference in color, texture, odor, and taste of fermented dry zamné and those of dry soumbala market and dry soumbala DTA observed by tasters could be due to the difference in the substrate. One of the major changes during the production of alkaline fermented products is that which occurs in the texture of the products. Mbajunwa et al.20 and Njoku et al.21 showed that B. subtilis has the ability to soften the tissues of African oil beans, which allows obtaining the desired texture of Ugba. This is due to the fact that B. subtilis may possess pectic and proteolytic enzymes that readily hydrolyze the pectin and protein components of the beans. fermented Zamné is less appreciated than soumbala DTA and soumbala market. This could be related to the strong aroma of fermented Zamné, as previously indicated by the results of sensoriel profil. In fact, during the sensory evaluation of Beninese condiments, Azokpota et al.22 found that for a good quality of the investigated condiments, according to the preference of consumers, the best and most appropriate odour is whose intensity was neither too strong nor too weak. This could be also related to the habits of consumers, who were familiar with the consumption of Soumbala. These results are similar to those of Appiah et al.15, who found that fermented seeds of Parkia biglobosa performed better than fermented seeds of Glycine max and Treculia africana for overall acceptability, during the Comparative assessment of their performances. According to Beaumont23, fermented condiments exhibit sensory properties resulting from unique flora (Bacillus spp.) and processing technologies. Flavour characteristics of these fermentations are derived in part from the liberation of ammonia, concurrent with protein hydrolysis to free amino acids and peptides. Moreover, Achi24, also reported that specific variations in the fermentation process of condiments result from environmental conditions and the type of substrate. Soumbala market performed better than soumbala DTA. In a study on the effect of mechanical hulling on the fermentation of Parkia biglobosa seeds, Sawadogo-Lingani et al.12 also obtained the same results, Soumbala from the traditional process was better for consumers than Soumbala produced with seeds dehulled by mechanical dehulling machine. In terms of colour, soumbala DTA performed better than Soumbala market and fermented Zamné. This difference could be related to dehulling, so, the dehulling can be used to improve the colour of fermented zamné. According to Parkouda et al.25, Maari, fermented baobab (Adansonia digitata L.) seeds, were not dehulled before the fermentation, contrary to many fermented condiments produced from African locust beans (Soumbala, Afitin, Iru, Sonru and Netetu); this can lead to a difference in the chemical content and the profile of volatile compounds. Volatile compounds are one of the most valuable traits contributing to the quality and sensorial attributes of fermented condiments23.

Concerning the broths, the three broths with fermented condiments performed better than the control broth for all parameters. This means that the 3 fermented seeds are acceptable condiments, and can be used to enhance the flavour of dishes. These results are similar to those of Appiah et al.15 for the evaluation of stew. They showed that the stew prepared using the 3 condiments (fermented seeds of Parkia biglobosa, Glycine max and Treculia africana) scored better than the stew without condiment.

Finally, the results of difference tests showed that the broths prepared using fermented Zamné, Soumbala DTA and Soumbala market differed from the control broth in all the analyzed parameters. This means that the addition of fermented condiments to a broth leads to a change in taste, color and odour. These differences were higher for the broth with fermented Zamné than the broths with Soumbala. This implies that fermented Zamné has strong intensity sensory attributes, so, it must be used in lower quantities than soumbala in dishes. Also, to improve the sensory attributes of fermented Zamné, an extension of fermentation time could be considered. In fact, many othors reported that some African food condiments were fermented for 72 h, contrary to fermented Zamné which were fermented for 48 h in this study. Tayohounta type 1 produced in Benin is a fermented product made with baobab kernels. The processed kernels are left for 72 h of fermentation26. For the production of Ogiri, a food condiment produced in Nigeria, boiled melon seeds (Citrullus vulgaris) are left to ferment for 3 days 75. Moreover, Appiah et al.15 reported that for the production of three fermented condiments produced from Parkia biglobosa, Glycine max and Treculia africana seeds in Ghana, the beans of the crops were boiled and then fermented for 72 h20. Furthermore, Parkouda et al.25 reported that Maari is produced by processing baobab (Adansonia digitata L.) seeds and left to ferment spontaneously (first fermentation) for 72 h. The strong correlations between rank and odor (0.88) and between rank and taste (0.85) indicate that the ranking of samples is based mainly on the odor and taste of the product, texture and color are secondary parameters. Indeed, according to Appiah et al.15, aroma, which consists of taste and odor, is the most important predictor of the acceptability of fermented condiments. Color is an important parameter that can guide consumer preferences when making food choices. Indeed, sensory evaluation of color relies on sight, while color detection requires instrumental analysis rather than the human eye. The luminance L* is low for the fermented seed powder samples of Senegalia macrostachya and Parkia biglobosa and tends towards black. All the values of the parameter a* obtained are negative. These samples tend towards greenish because, according to Granato and Masson27, the color parameter a* takes positive values for reddish colors and negative values for greenish colors. For the parameter b*, it takes positive values for yellowish colors and negative values for bluish colors27. All the values found for the color parameter b* are all negative. The color of the samples therefore tends towards bluish. The index C* indicates brightness and dullness. The C* values of the samples are low, which indicates that their colors are dull. The a*/b* parameter indicates good food quality when its value is low28. After analyzing the a*/b* parameter, it is found that the powder samples of fermented Zamné and Soumbala market are significantly different from those of Soumbala DTA. fermented Zamné and Soumbala market were darker. The results of this study indicate that although soumbala was the most acceptable, similar condiments could be produced using zamné.

Conclusion

The study has shown that fermented Zamné is a dark-brown condiment with strong odour and alkaline taste. Its texture is not sticky, with no whitish layer. The characteristics of fermented Zamné differ from those of traditional soumbala (market), which was the most liked condiment. Fermented Zamné can be used as a seasoning agent, however, it must be used in lower quantities than soumbala because of its intense sensory characteristics. To improve the acceptability of this condiment, the seeds of Senegalia macrostachya could be dehulled before fermentation, with an extension of the fermentation time.