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Sensory Properties of Table Sugars Derived from the Inflorescences Sap of Three Coconut (Cocos Nucifera.L) Cultivars in Côte d'Ivoire

Okoma D.Muriel.J*, Konan K. Jean.Louis, Assa Rebecca.R

Marc Delorme Research Station for Coconut, National Centre of Agronomic Research (CNRA), Abidjan, Côte d'Ivoire

Abstract: The present study aimed to determine the acceptability of crystalline sugars from the sap of coconut inflorescence (Cocos Nucifera.L) hybrids PB121⁺, PB113⁺ and cultivar GOA by the consumer. They were produced for 45, 40 and 35 minutes at temperatures ranging from 60-120; 60-140 and 60-160°C respectively for T1, T2 and T3 treatments. The results of the sensory characterization show that coconut sugars are better accepted than white (6.06) and brown (5.5) cane sugars. The perception of the descriptors reveals that coconut sugars as a whole have a finer texture than cane sugars. This increases their pleasantness in the mouth. Those from treatment 1 have a white color and are characterized by a subtle coconut aroma and a pronounced caramel aroma. The sugars from treatments 2 and 3 are blond and dark brown respectively, with a very pronounced coconut aroma. Thus, coconut sugar has organoleptic assets that make it an alternative to cane sugar. These properties make it an ingredient that can be used in pastry making for cakes, ice cream, in sweet culinary recipes and to sweeten drinks.

Keywords: sensory analysis - coconut sap sugar

Received August 08, 2020; Revised September 01, 2020; Accepted November 19, 2020

Citation: Okoma D.Muriel.J, Konan K. Jean.Louis, Assa Rebecca.R, Sensory Properties of Table Sugars Derived from the Inflorescences Sap of Three Coconut (Cocos Nucifera.L) Cultivars in Côte d'Ivoire. American Journal of Food and Nutrition, 8 (3). 90-100. January 2020. doi:10.12691/ajfn-8-3-6

1. Introduction

The valorization of the sap of the inflorescences of the most cultivated coconut trees in Ivory Coast has been undertaken, in order to diversify the uses of the plant. Thus, this sap, rich in carbohydrates [1] was dehydrated and crystallized into table sugar by [2].

The physico-chemical and nutritional characterization of coconut sugar produced by [2] in comparison with brown and white sugars from sugar cane shows that coconut sugar is an important source of polyphenols. In addition, it is less energetic than brown and white sugars from cane. Mineral analysis of table sugar from the inflorescences of coconut palms grown in Côte d'Ivoire reveals the presence of 12 minerals including 8 macroelements (Na, Mg, Si, P, S, Cl, K and Ca). Potassium (K) is the majority macroelement of coconut sugars. White cane sugar does not contain any minerals. The trace elements in coconut sap sugar are iron, copper, zinc and bromine. These trace elements are in small quantities in brown sugar and do not exist in white cane sugar. Four water-soluble vitamins (C, B1, B2 and B6) have been determined in coconut crystal sugar. On the other hand, no vitamin was identified in cane sugar. Vitamin C is the most abundant in coconut sugar. The oses contained in coconut crystal sugar are sucrose, glucose and fructose. The sweetness index of cane sugars is close to that of coconut trees [3].

In view of all the above, coconut sugars are natural sweeteners with a low energy value. In addition, they are rich in polyphenols, vitamins and minerals unlike refined cane sugar which is essentially composed of sucrose and its red counterpart which contains very few nutrients.

Thus, coconut sugars produced in Côte d'Ivoire can be considered as a phytonutrient substitute, capable of replacing sugarcane sugars. Indeed, thanks to their sweetening power close to saccharose, the coconut sugars produced can be used as sweetening ingredients in pastries, confectionery, beverages and culinary preparations.

However, in order to determine the acceptability of this new ingredient by consumers, the determination of the sensory profile of coconut sugar from the inflorescences of the most cultivated coconut trees in Côte d'Ivoire was carried out in this study.

2. Hardware

2.1. Biological Material

The biological material consisted of crystalline sugars from the sap of the inflorescences of 03 coconut cultivars. These were the PB113⁺, PB121⁺ and GOA hybrids. White and brown sugars from sugar cane were taken as controls.

3. Methods

3.1. Coconut Sap Production Methods

Sap from the inflorescences of the three coconut cultivars was collected according to the method of [1]. Indeed, the sap is extracted from the spathe of row 8 (Figure 1A). It corresponds to the unopened one located above the newly opened spathe. It must first be ligated at its convex edge with a rigid thread and firmly attached to an underlying palm. It is then gradually tilted for a week, to bring its tip to a lower elevation than the peduncle, forming an obtuse angle with the coconut trunk (Figure 1B). When the spathe is sufficiently inclined, a section about 15-20 cm from its apical part is made (Figure 1C), to allow the sap to flow out. After cutting off the end of the spathe, the remaining part of the spathe should then be introduced into a plastic container through a circular opening made specifically for this purpose, the diameter of which is a function of the diameter of the spathe for sap collection (Figure 1D). The harvests were carried out 03 times a day, at 7, 12 and 5 o'clock. Only the 12 and 5 o'clock harvests were used for the production of table sugar. The 07h harvest is consecutive to the 14h harvest, the action of fermentable micro-organisms has led to an increase in reducing sugars. This makes the crystallization of such sap impossible. The freshly collected ochre-colored sap (Figure 1E) becomes whitish (Figure 1F) after more than 12 hours of draining, a sign of spontaneous fermentation. Indeed, as soon as it leaves the spathe, coconut sap contains essentially saccharose (9.4% to 12.24%) and traces of fructose and glucose that would have spontaneously undergone fermentation by microorganisms. Sucrose molecules are easily hydrolyzed into reducing sugars (glucose and fructose) under the enzymatic action of invertase, which would be produced by certain yeasts of the genus saccharomyces or moulds of the genus Aspergillus.

The collection containers must first be sanitized with water heated to 100°C in a boiling bath and replaced after each collection.

3.2. Coconut Sap Sugar Production Methods

The sap is freshly collected (Figure 2A) and processed into table sugar without freezer conservation using the [2] method. However, variations in final temperatures coupled with distinct cooking times were carried out in order to evaluate the effect of the time/temperature couple on the sensory criteria studied.

Thus, three different time/temperature pairs or treatments were applied. Indeed, one liter of sap is transformed into crystalline sugar during 45, 40 and 35 minutes at temperatures varying from 60-120; 60-140 and 60-160°C respectively for treatments T1, T2 and T3.

Indeed, the sap is boiled until a syrup is obtained (Figure 2B). The syrup is kneaded with a wooden spatula (Figure 2C) to aerate the medium before being cooled to room temperature (25°C).

This results in a viscous mass (Figure 2D) that will be crystallized. The coconut sugars crystals (Figure 2E) are destemmed, crushed and dried at room temperature (25°C) for 24 hours.

The use of freshly collected sap is necessary because without preservatives, even frozen, the use of sap results in the formation of a gelled mass that does not crystallize.

Figure 1. Steps of production of the sap of coconut inflorescences

Figure 2. Different steps of production of sap sugar from coconut inflorescences

3.3. Sensory Analysis Methods

According to the French standard [4], sensory analysis is defined as the examination of the organoleptic properties of a product by the five sense organs of sight, hearing, smell, taste and touch. In practice, the approach has consisted of carrying out hedonic and descriptive tests on samples of coconut crystal sugar which were compared to white and brown sugar from sugar cane. The tastings took place at the Félix Houphouët-Boigny University. The tests were carried out according to the modified method of [5]. The [6] standards on the layout of the premises, the size of the jury [7] and its training [8] were applied.

3.3.1. Experimental Device

The T1, T2 and T3 treatments applied generated three (3) batches of sugars per variety. The study covered three campaigns during the year 2017, January, June and December. Nine batches of coconut crystalline sugar were produced and two batches of sugars (brown and white) of cane were sampled per campaign.

Sensory analysis was carried out on 9 samples of coconut sugar from treatments 1, 2 and 3 of one kilogram each per cultivar. Of these, a total of 27 lots of coconut crystal sugar were produced and six lots of cane sugars were analyzed. The physico-chemical parameters were repeated three times and the analyses were carried out on each of the batches. The tests were performed by a panel of 31 untrained tasters for hedonic characterization and 14 trained tasters for descriptive analysis.

3.3.2. Hedonic Tests

Hedonic tests were performed to assess the general acceptance of the tasters with respect to four descriptors of the sugar samples studied. These were texture, color, flavour and aroma. The tests were conducted at the Félix Houphouët-Boigny University in Abidjan with the 31 untrained tasters. The room used was arranged according to the provisions of the [9] standard. It was equipped with individual booths allowing the isolation of the judges. The booths were equipped with lighting.

The tasting room was set up to ensure maximum comfort and concentration for the judges, such as light colors, no frames, decorations, distractions, odors and noises. It was equipped with an air conditioner that allowed for ventilation by maintaining the temperature at 20°C. For each taster, the analysis consisted of tasting the coded samples of 33 sugars (27 for the 3 cultivars and 6 for the controls).

For each sample, the taster was asked to rate his appreciation of each descriptor and his general acceptance of the product on a nine-point hedonic scale [10] using rating sheets distributed for this purpose. On this scale, the number one meant that the sample was "extremely unpleasant" while the nine meant "extremely pleasant" in relatio to the corresponding descriptor. Panelists were given the opportunity to add observations to their evaluation on the tasting sheet.

The samples were presented one by one in a precise tasting order (balanced experiment design) in order to limit the rank effect.

3.3.3. Sensory Profile

The sensory profile of the coconut crystal sugar samples was established on the basis of the four descriptors indicated. Recognition of the perception levels of these descriptors in the sugar required trained tasters.

• Recruitment and jury selection

Recruitment was carried out using a questionnaire based on the model proposed by [11].

Forty (40) volunteers were registered among the teachers, administrative staff and students of the Félix Houphouët-Boigny University of Cocody. They were then subjected to triangular and "2 out of 5" tests.

For the first test, the volunteers were given three samples, one of which was doubled. For the second test, they were offered five samples, two from the same batch and the other three from another batch. They were then asked to identify the intruding sample for the triangular test and to group identical samples by lot for the "2 out of 5" test. The tests were carried out by ortho-nasal (by illumination) and retro-nasal (in the mouth) methods.

Criteria such as availability, sensory perception skills such as visual difficulties, the wearing of dentures or signs of an allergy such as colds, and motivation to participate in the study were determining factors in the choice of panelists. These factors were indeed likely to alter the perception of characteristics considered important. Following these tests, twenty-eight (28) panelists out of the 40 volunteers at the start of the study were pre-selected to carry out the tests to determine the perception thresholds.

• Training and evaluation of panelists

Panelist training was conducted in two sessions of 2 hours each. The twenty-eight (28) pre-selected individuals were subjected to basic taste recognition tests and tests to determine their perceptibility and identification thresholds.

After grouping the attributes, a 10 cm linear scale was used to quantify the intensity of each descriptor. Quantification was performed against reference food products known to be very low or very high in intensity relative to a given attribute.

Thus, as references, fine corn powder was chosen for the texture, toasted coconut cakes, sugar cane juice and caramel candies for the coconut, sugar cane and caramel flavors respectively. The salty, sweet, bitter and sour flavors were referenced by sodium chloride, sucrose, quinine sulfate and citric acid respectively.

Mineral water was used for the preparation of the control solutions at different concentrations. Increasing dilutions from A to F of the geometric series were prepared from these (Table 1) and packaged in containers coded by the test organizer. Each flavour was prepared in duplicate to confirm the taster's ability to distinguish it. The different dilutions were presented in increasing order of concentration. A total of 24 dilutions (6 dilutions x 4 flavours) were tested per subject.

The tasting consisted of putting a quantity of about 15 mL of test solution into the mouth, followed immediately by the indication on a form of the type of flavour or the intensity of the perceived taste sensations. For the color attribute, the subjects were inspired by a form with a range of colors allowing them to assign a precise color to the sample. At the end of these tests, 14 people including 9 women out of the 28 pre-selected panelists were selected to constitute the final panel.

• Conducting the descriptive analysis of the sugars studied

During the analysis, 15 g of each sugar was presented to the 14 selected panelists in disposable, pre-coded plates. They were distributed to each in a pre-established order of presentation known only to the organizers. During the tasting, a questionnaire was made available to each panelist. Each sample was tested on a 10-point linear scale according to the intensity of perception of each of the descriptors evaluated. Thus, the left end of the scale represented the lowest intensity of the attribute, and the right end indicated the highest intensity. References were positioned at these extremes. After tasting each sample, the panelist was asked to taste wholemeal bread and rinse their mouth with mineral water to let the previous sensations disappear before moving on to the tasting of the next sample.

3.4. Statistical Analysis of the Data

The statistical analysis of the data consisted of univariate analyses. In this case, the descriptive analysis of the sensory parameters of coconut sugar. This concerned the determination of the minimum, maximum, coefficient of variation of the quantitative parameters and the frequency of modalities of the different qualitative parameters.

Next, the comparative analysis of the three cultivars was performed using the single criterion analysis of variance (ANOVA 1). Indeed, this ANOVA test is preceded by the MANOVA (Multiple Analysis of Variance) in order to check if the variables taken together make it possible to highlight the existence of a significant difference between the cultivars on the basis of the analyzed parameters. The ANOVA 1 test was followed by the post-ANOVA test of the smallest significant difference (ppds).

All the statistical tests were performed with XLSTAT version 7.5.3 and Statistica 7.1.

4. Results

4.1. Hedonic Tests

The general acceptability of coconut sap sugars ranges from 6.41±0.62 to 8.55±0;54 on a nine-point scale, regardless of the treatment applied (Table 2).

Coconut sap sugars from treatment 1 are significantly more appreciated than those from the other two treatments in all cultivars. In contrast, white and brown cane sugars are moderately accepted (Table 2). The analysis of variance shows that the degree of satisfaction of the panelists decreases with the sugar treatments for a given cultivar (Figure 3). In general, regardless of the cultivar and the treatments applied, coconut sugars are better accepted than white and red cane sugars.

Table 1. Dilutions of acid, bitter, salty and sweet flavour control substances

Table 2. Panelist' taste preference for the crystalline sugars studied.

Figure 3. Diagram showing the general acceptability of the sugars studied (A: sugar from hybrid PB121⁺; B: sugar from hybrid PB113⁺; C: sugar from cultivar GOA; Tém B: white cane control sugar; Tém R: brown cane control sugar; T1, T2 and T3: treatments 1, 2 and 3.)

4.2. Sensory Profiles

4.2.1. Sensory profile of sugars from the T1 treatment

Regardless of the descriptor, the sensory profile of coconut sap sugars produced by the T1 treatment differs from that of white and red sugars from cane. Analysis of the scores given by the tasting panel showed significant differences (p < 0.05) for all sensory descriptors. Also, there are similarities between the different sugars for a given attribute (Table 3).

Indeed, all the sugars in coconut sap have a granular texture which was perceived to have statistically similar intensities on a ten (10) point scale. Their intensities for this parameter are significantly lower than those of brown and white sugars from sugar cane, which have statistically identical degrees (Table 3).

The white coloration was strongly perceived at similar levels according to ANOVA in PB121⁺, PB113⁺ and GOA sugars (Table 3). They are identical to white cane sugar.

Table 3. Perception indices of the descriptors of crystalline sugars from treatment 1

Figure 4. Sensory profile of coconut sugars from treatment 1 (A1: PB121+ hybrid sugar from processing 1; B1: PB113⁺ hybrid sugar from processing 1; C1: GOA hybrid sugar from processing 1; Tém B: white cane control sugar; Tém R: brown cane control sugar)

The coconut aroma is perceived at a significantly higher intensity in the sugar of the PB113+ hybrid than in the other two cultivars. This aroma is non-existent in the control sugars. These are marked by a subtle cane aroma in the white sugar and a pronounced cane aroma in the brown sugar. On the other hand, the caramel aroma was statistically more perceived in the PB113⁺ hybrid with intensity. Its presence was identified moderately in PB121⁺ and GOA sugars. This aroma was weakly perceived in brown cane sugar, whereas it was not identified in its white counterpart (Table 3).

Flavors were perceived differently in the sugars studied. The sweet flavor was identified with significantly higher intensity than the other three flavors in all cultivars studied. Its degree of perception was statistically higher in white cane sugar. Regarding the bitter, sour and astringent flavors, their perception is low in the sugars of the coconut beans studied and is non-existent in the two controls (Table 3).

The sensory profile of coconut sugars from treatment 1 is shown in Figure 4.

4.2.2. Sensory Profile Of Sugars from T2 Treatment

The average scores given by tasters for the sensory descriptors of coconut sugars from Treatment 2 are shown in Table 4. These scores made it possible to define the sensory profile of the sugars of the 3 cultivars studied, represented in Figure 5. The granular texture of coconut sugars was perceived with statistically identical intensities in all cultivars. These values are lower than those of brown and white sugars from sugar cane.

In addition, blond coloration was strongly identified in coconut sap sugars with statistically identical intensities. However, their intensities for this criterion are statistically higher than that of brown cane sugar which was perceived with a value of 6.50± on a ten (10) point scale. Brown coloration is relatively perceived with statistically identical intensities in coconut sugars. Regardless of the cultivar, coconut and caramel aromas were perceived exclusively in sugars produced with statistically identical intensities. The sugarcane flavor is perceived differently in sugars from cane. Indeed, its intensity is statistically higher in brown sugar compared to white sugar.

The sweet flavor is perceived with a statistically higher intensity than the bitter, acidic and astringent flavors. Coconut sugar has statistically higher sweetness intensities than brown cane sugar. On the other hand, the bitter, acidic and astringent flavors are weakly perceived in coconut sugars (Table 4).

Table 4. Perception indices for descriptors of crystalline sugars from treatment 2

Figure 5. Sensory profile of sugars from treatment 2 (A2: sugar of hybrid PB121⁺ from treatment 2; B2: sugar of hybrid PB113⁺ from treatment 2; C2: sugar of cultivar GOA from treatment 2; Tém B: white cane control sugar; T2: brown cane control sugar)

4.2.3. Sensory Profile of Sugars from T3 Treatment

The scores of all the sensory attributes of coconut sugars for Treatment 3 (Table 5) allowed the development of the sensory profile represented in Figure 6.

The granulometry of coconut sugars is statistically smaller than that of cane sugars. The values obtained for brown and white sugars from cane are statistically identical. In addition, the white, blond and brown color perception indices vary significantly from 0 to 9.43±1.20 between samples. The white color was strongly perceived exclusively in white cane sugar.

Only brown cane sugar presented a blond color of intensity. On the other hand, the brown coloration was strongly identified by the panelists with statistically identical degrees in coconut sugars. It was nil in white sugar and weak in brown sugar.

Figure 6. Sensory profile of coconut sugars from treatment 3 (A3: sugar of hybrid PB121+ from treatment 3; B3: sugar of hybrid PB113+ from treatment 3; C3: sugar of cultivar GOA from treatment 3; Tém B: white cane control sugar; T2: brown cane control sugar.)

Table 5. Perception indices of the descriptors of crystalline sugars from treatment 3

Independently of the cultivar, the coconut aroma is strongly perceived in the coconut sugars. This aroma is absent in cane sugars. However, the caramel aroma is statistically more perceived in the sugars of PB121⁺ and PB113⁺ hybrids than in the GOA cultivar. The intensity of the sweet flavor is predominant in all sugars with statistically identical values in coconut sugars. As for the bitter and astringent flavours, their perception is weak in coconut sugar and non-existent in the two controls (Table 5).

4.2.4. Comparative Analysis of the Descriptors of the Sugars Studied

The sugars of the three coconut cultivars from treatments 1, 2 and 3 were compared with each other, attribute by attribute. Table 6 presents the results of the comparative analysis and Figure 7 shows their sensory profiles.

Regardless of the treatment applied, all coconut sugars have a statistically identical particle size ranging from 1.98±0.21 to 3.14±0.37. These values are lower than those of brown and white cane sugar. The coloring of coconut sap sugars varies significantly from white, to blond and brown depending on the treatment applied. Thus, all the coconut sugars resulting from the T1 treatment have a white coloration of statistically identical intensity to that of white cane sugar. The T2 treatment provides coconut sugars with a blond color whose intensity is higher than that of brown cane sugar. On the other hand, sugars from the T3 treatment are marked by a brown color intensity statistically higher than the other colorings.

Considering all the cultivars studied, the intensity of coconut aroma is statistically lower in the sugars from the T1 treatment than those from the other two treatments. The highest intensities for this aroma are recorded in the samples from T3. The caramel flavor is mostly identified in the sugars from the T1 treatment. On the other hand, the cane flavor is exclusively perceived in cane sugars to a statistically higher degree in the red than in the white.

The sweet taste was strongly identified in all the coconut sugars. However, its perception is statistically lower in the sugars from the T1 treatment compared to those from the other two treatments. Brown cane sugar has statistically the same sweetness intensity as coconut sugars from treatment 1, and white cane sugar has statistically the same sweetness intensity as coconut sugars from treatments 2 and 3. As for the acid taste, its perception is statistically lower in the sugars from treatment 1 than those from treatments 2 and 3, which are statistically identical. Concerning the astringent flavor, its perception is statically weak in the coconut sap sugar. However, the bitter, sour and astringent flavors were not perceived in white and brown cane sugars (Table 6).

Table 6. Comparison of the perception indices of the descriptors of crystalline sugars from treatments 1, 2 and 3

Figure 7. Sensory profile of coconut sugars from treatments 1, 2 and 3 (A1: sugar of hybrid PB121⁺ from treatment 1; B1: sugar of hybrid PB113⁺ from treatment 1; C1: sugar of cultivar GOA from treatment 1; A2: sugar of hybrid PB121⁺ from treatment 2; B2: sugar of hybrid PB113⁺ from treatment 2; C2 : Sugar of cultivar GOA from treatment 2; A3: Sugar of hybrid PB121⁺ from treatment 3; B3: Sugar of hybrid PB113⁺ from treatment 3; C3: Sugar of cultivar GOA from treatment 3, T1: white cane control sugar; T2: brown cane control sugar.)

5. Discussion

In general, whatever the cultivar and the treatments applied, coconut sugars are better accepted than white and red cane sugars. People's behavior and eating habits did not influence their appreciation of coconut sugars. In fact, consumer acceptance of sugar is said to be strongly influenced by its color, taste, aroma, texture, and ease of melting in the mouth [12] The perception of granulometry shows that all coconut sugars have a finer texture than cane sugars whatever the treatment applied. Indeed, the panelists indicated that in general, the finer texture of the coconut sugars studied would give them the ability to melt easily in the mouth compared to sugars from cane. This would increase their enjoyment.

However, depending on the treatment applied, the sugars of the cultivars produced were variously appreciated. The analysis of variance shows that the degree of satisfaction of the panelists decreases with the treatments for the sugars of a given cultivar. These properties depend to a large extent on the processing technology. Indeed, those resulting from treatment 1 were significantly more accepted regardless of the variety. In the opinion of the tasters, these sugars would be characterized by a white coloration and a pronounced caramel aroma with a subtle presence of the coconut flavor that would increase their pleasantness.

Indeed, considering treatments 1, 2 and 3, the panel of trained tasters indicated that the coconut sap sugar had a white, blond and dark brown color respectively. This difference in colouring could be explained by the cooking temperature and the high content of reducing sugars and proteins in the different types of sugars produced. The samples from Treatment 3 have higher levels of reducing sugars and protein, both of which are substrates for the Maillard reaction. Indeed, the rise in temperature will promote the hydrolysis of sucrose, which will lead to an increase in the content of reducing sugars. The latter will react with proteins during the Maillard reactions to produce brown pigments or melanoidins. It is these pigments that contribute to the dark brown coloration of coconut sugars [13] resulting from treatment 3. The sugars from this treatment were also less well appreciated than those from the other two treatments.

According to the jury, the pronounced presence of the coconut aroma and the intensity of the sweet taste too high in these sugars would diminish the pleasure in the mouth.

Indeed, the comparison of aroma perception shows that the caramel and coconut aromas are more intense in the sugars from treatments 1 and 3 respectively.

This difference would be due to the nature of the aromatic compounds that develop in each of these sugars at the time of cooking. Our results are similar to those of Arifin et al, [14] who studied the sensory characteristics of dark chocolates formulated with coconut sugar compared to cane sugar. These authors revealed that coconut sugar obtained at 120°C gave dark chocolate a caramel aroma that was not perceived by tasters in the one formulated with cane sugar. Indeed, [12] identified fifteen (15) aromatic compounds in coconut crystal sugar including furfural, 2-furan-methanol, 4-methyl-2(5H)-furanone, 5-methyl-2-furanemethanol, Furaneol and especially maltol which would be responsible for the caramel aroma in coconut sap sugar. These heterocyclic compounds are generally derived from the Maillard reaction produced during the heating process. According to [15] and [16], pyrazine derivatives such as 2, 3-dimethylpyrazine, 2, 5-dimethylpyrazine and 2-ethyl-3,5-dimethylpyrazine would be responsible for the coconut flavor in coconut sugar.

Moreover, the typical sugar cane aroma has been identified only in brown and white sugars from sugar cane. As in coconut sugars, the aroma of sugar cane would be formed during the Maillard reaction. According to [17], cane sugar owes its flavor to the presence of aromatic compounds such as 3-hydroxy-2-methyl-4-pyranone, 2-hydroxy-3-methyl-2-cyclopentenone and sotolone in cane sugar when they have not been assayed in the juice. They would be formed by condensation of pyruvate and 2-oxobutyrate, 2-oxoglutarate or glutamate which are present in the cane juice.

Among the four flavors tested, the sugars studied generally have a more intense sweetness than the bitter, acidic and astringent flavors. In fact, the sweet taste is perceived with relatively the same intensity as the total sugar content of the samples analyzed. This could be justified by the fact that the dry matter of the sugars studied is mainly composed of carbohydrates, mainly sucrose. However, the sweetness depends primarily on the sucrose content.

The results show that the sugars from treatment 1 have a less pronounced sweet taste than those from the other two treatments. The intensity of the sweetness would increase with temperature.

As for the acid taste, its perception is statistically lower in sugars from treatment 1 compared to those from treatments T2 and T3.

The indices attributed by the tasters are comparable to the titratable acidity values evaluated by titrimetry. Thus, the acids that constitute the majority of volatile organic compounds would be strongly involved in the expression of its flavor, contrary to [18] according to which, this flavor would depend primarily on esters.

The poorly perceived astringency in the sugars of the coconut palms studied would be due to the presence of acetic acid in them. Indeed, this acid has been identified in coconut sap and sugar in numerous studies [19,20]. Moreover, the polyphenol richness of coconut sugars is believed to influence their astringency. Some authors [21,22] have reported the role of polyphenols, especially flavonoids, in food bitterness and astringency. According to them, flavonoids and particularly anthocyanins and flavonols play an important role in the quality of red wines. Indeed, their molecular weight has an influence on the astringency and relative bitterness of the wine. Indeed, the monomers are more bitter than astringent, whereas the opposite is true for high molecular weight derivatives.

6. Conclusion

The results of the sensory characterization show that coconut sugars are better accepted than white (6.06) and brown (5.5) cane sugars. Nevertheless, those from treatment 1 are significantly more appreciated in all cultivars with degrees varying from 8.20 to 8.55.

Considering all the treatments, the lowest appreciations are recorded with the sugars of the third treatment. The degree of satisfaction of the panelists decreases according to the treatments for sugars of a given cultivar.

The perception of the descriptors reveals that coconut sugars as a whole have a finer texture than cane sugars. This increases their pleasantness in the mouth.

Those from treatment 1 have a white color and are characterized by a subtle coconut aroma and a pronounced caramel aroma. The sugars from treatments 2 and 3 are blond and dark brown respectively, with a very pronounced coconut aroma in treatment 3 (8.95). The sweet taste was strongly perceived in all the coconut sugars. In addition, it was relatively perceived with the same intensity as the total sugar content of the samples of our three cultivars. As for the acidic flavour, its perception is statistically lower in the sugars from treatment 1 compared to those from treatments T2 and T3. As for the astringent and bitter flavors, their perception is very low in coconut sugar.

Coconut sugar, regardless of the cultivar studied, in addition to its interesting nutritional profile, has organoleptic assets that allow it to be an alternative to cane sugar anchored in eating habits. These properties make it an ingredient that can be used in pastry making for cakes, pancakes, ice creams, in sweetened culinary recipes and to sweeten drinks. Considering the three treatments, the sugars from the first treatment were better appreciated by the tasters. These sugars are characterized by a white color and by a subtle coconut aroma and a pronounced caramel aroma. Treatment 1 is therefore recommended for the production of coconut sugar.

This is an opportunity for the coastal populations who have more than 80% of the Ivorian coconut groves to produce quality sugar.

Authors' Contribution

This work was carried out in collaboration among all authors. Authors ODMJ, ARR and KKJL designed and wrote the study protocol. Author ODMJ conducted the documentary research, conducted the laboratory analyses, the statistical analysis and the first draft and revised the manuscript. Authors KKJL and ARR took part in the interpretation of the results and provided a major contribution in the elaboration of the final document.

Acknowledgements

To the Centre National de Recherche Agronomique (CNRA), for having provided us with the funds and infrastructure necessary for the design of this study and the drafting of the manuscript. At the University Félix HOUPHOUET-BOIGNY (UFHB), for their involvement in the analysis and interpretation of the results.

Conflict of Interest

The authors have no conflicts of interest to declare.

Informed Consent

Written informed consent was obtained from all study participants.

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