FUNCTIONAL PROPERTIES OF TABLE SUGARS DERIVED FROM THE SAP OF THE INFLORESCENCES OF 03 COCONUT (COCOS NUCIFERA.L) CULTIVARS IN CÔTE D'IVOIRE

1. Marc Delorme Research Station for coconut, National Centre of Agronomic Research (CNRA), Abidjan, Côte d'Ivoire. 2. Laboratory of Biochemistry and Food Sciences, UFR Biosciences, University Felix Houphouët Boigny, Abidjan, Côte d'Ivoire. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History Received: 01 September 2020 Final Accepted: 05 October 2020 Published: November 2020


ISSN: 2320-5407
Int. J. Adv. Res. 8 (11), 254-263 255 Among the many ways of adding value to the coconut tree, in Asia, the sap from the inflorescence occupies an important place and is of growing interest. With 13 to 17% carbohydrates, it is almost as rich as sugar cane juice (Konan and al., 2014; Xiaet al., 2011)and is almost acid-base neutral, containing water-soluble vitamins (Hebbarand al., 2015).
In Côte d'Ivoire, with the exception of the recent work carried out on the biochemical properties of the sap of coconut inflorescences, its valorization into table sugar has not yet been done. However, in view of the drop in copra prices, the diversification of coconut uses is essential.
Much work has been done in Asia on the biochemical properties of coconut sugar.
However, the protocols on the method of producing crystal sugar from sap are ambiguous and very imprecise, making them non-reproducible.
In addition, no study has been done on sugars derived from the sap of the different varieties of coconut palm popularized in Côte d'Ivoire. However, at the genetic, agronomic and morphological levels, diversities are observed in these coconut cultivars.
In addition, the alarming evolution of metabolic diseases has raised public health policy concerns. Thus, the search for alternatives aimed at developing natural sweeteners to replace industrial sugars is encouraged.
Consequently, the general objective of this study is to determine the functional characteristics of crystalline sugars derived from the sap of inflorescences of three coconut cultivars (Cocos nucifera. L) as a function of the time/temperature couple in Côte d'Ivoire.

Hardware Biological material
The biological material consisted of sap from the inflorescences of row 8 ( Figure 17) of three coconut cultivars. These came from plots 043, 034 and 064 of the CNRA Station Marc-Delorme which are located respectively 1.8, 2 and 1.5 km from the laboratory. These cultivars are: 1. -Great West Africa (GOA), originating from West Africa, which has an earliness of 7 years with a yield of 0.7 t to 1.5 t copra/ha/year. It was planted in 1998 on plot 043. 2. -The PB121 + hybrid resulting from the cross between the Malaysian Yellow Dwarf (MJD) and the improved GOA was created by WHRI-assisted pollination in 1964 (De Nuce and Rognon, 1986). Its improved version was created in 1992. It has the best average yield per hectare in the world (4 t copra/year). It is the most widespread coconut palm in the world (Konan, 2005). On plot 064, the trial that houses it was planted in 1996. 3. -The PB113 + hybrid, resulting from a cross between the Red Dwarf of Cameroon (NRC) and the improved Grand Rennel (GRL). It produces 4 t copra/year. It was also created in 1992 and has been planted on plot 034 since 1996.
This choice is motivated by the fact that the GOA cultivar is traditionally the most widespread local variety in Côte d'Ivoire and is used as a control in all experiments on large coconut trees. PB121+ and PB113+ are the hybrids that the CNRA has popularized worldwide for their high productivity and tolerance to certain biotic and abiotic stresses.
Samples of commercially available white sugar (Tém B) and brown sugar (Tém R) from sugar cane were used as controls.

Equipment for harvesting and processing the sap of coconut inflorescences:
To harvest the sap, a ladder was used to reach the spathe, it was tied with a wire and a knife was used to cut it. Cans were used to collect the sap. An electric hot plate (TRIOMPH) equipped with a temperature and time regulator was used to vaporize the sap. The heating of the sap also required a frying pan and stainless spatulas.

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Methods:-Coconut sugar production methods Sap from the inflorescences of the three coconut cultivars was collected and processed using the Okoma and al.
(2019) method. The freshly collected sap was first sprayed for 30 minutes at an increasing temperature of 60-140 °C. The sap was then processed by the Okoma method [7]. One liter of sap was boiled for two, three, five, eight and twelve minutes at 60, 80, 100 and 120 and 140°C respectively.
At the end of this step, a syrup is obtained, then kneaded with a wooden spatula to aerate the medium and cooled at room temperature (25°C) for 10 minutes. This resulted in a viscous mass which was sprayed a second time at 60°C for 30 minutes followed by mixing with a spatula for 20 minutes.
However, variations in the final temperatures coupled with different firing times were carried out in order to evaluate the effect of the time/temperature couple on the studied parameters.
Thus, three different time/temperature pairs or treatments were applied.

Constitution of sugar batches
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 per campaign and two batches of sugars (brown and white) of cane were sampled. In total, 27 batches of coconut crystal sugar were produced and six batches of cane sugars were analyzed. The physico-chemical parameters were repeated three times and each lot was analyzed.

Functional characterization Total protein
The protein contents were obtained by the Kjeldahl method(AOAC 1990), using the total nitrogen content of the sample. The method consists of several steps, including mineralization, distillation and titrisol NaOH (0.1N) assay. Two grams of sugar sample were dried in an oven at 70° C for 10 hours to determine the dry matter content (% DM). The test sample (PE) thus corrected (PNe) was then used for the nitrogen determination.
The following formulas were used to determine the protein content.

Total polyphenol content
The determination of total polyphenols in the sugar samples was carried out according to the Singleton and Rossi, (1965) method using the ciocalteus folin reagent. The processing of the samples was done in two phases.
In the first phase, all the polyphenolic or non-polyphenolic compounds, capable in alkaline medium of reducing the reagent of folin ciocalteuwere measured. For this purpose, 10 g of crystalline sugar was dissolved in 90 mL of distilled water ( S1 ). Then, 100 µL of S1 was introduced into test tubes and 500 µL of folin reagent ciocalteus diluted 1/10 with distilled water was added. After two minutes, 400 µL of 20% (w/v) sodium carbonate (Na2CO3) was added to start the redox reaction. The mixture was then placed in a 40°C water bath for five minutes and kept in the dark for 30 minutes at room temperature. This allowed the development of a blue coloration characteristic of the presence of polyphenols.
Two mL of dilute sugar solution ( S1) was taken from centrifuge wells to which 0.1 g PVPP was added. The mixture was homogenized and then centrifuged at 5000 rpm for 10 min. The supernatant was collected and 100 µL was removed to undergo the same treatment described in Phase 1.
The OD reading was taken at 760 nm with the spectrophotometer. The control contained distilled water in place of the sample. The difference between the ODs obtained with PVPP and without PVPP was used to determine the true ODs of the total polyphenols in the samples. A calibration curve obtained from different concentrations of a standard phenolic compound, gallic acid (or 3,4,5 -trihydroxybenzoic acid) with an initial concentration of 0.5 mg/mL, was used to determine the total polyphenol contents of the crystal sugar samples.

Dosage of flavonoids
The determination of flavonoids was performed according to the method described by Meda and al. (2005). A 1:10 diluted crystalline sugar extract solution was prepared from 10 g sugar and 90 mL distilled water. Subsequently, 0.5 mL of the resulting solution was introduced into a test tube.
To the contents of the tube were added successively 0.5 mL distilled water, 0.5 mL 10% (w/v) aluminum chloride, 0.5 mL 1 M potassium acetate and 2 mL distilled water. The tube is left standing for 30 min in the dark and the OD is read at 415 nm against a blank. A standard range established from a quercitrine stock solution (0.1 mg/mL) under the same conditions as the assay was used to determine the amount of flavonoids in the sample.

Statistical Analysis
The statistical analysis of the data consisted of univariate analyses.In this case, the descriptive analysis of the functional 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 followedby the post-ANOVA test of the smallest significant difference (ppds).

Results:-
Protein content Table 1 shows that the protein contents of the coconut sugars studied vary from 0.2±0.04 (PB121+, T1) to 0.67±0.16 g/100g (GOA, T3) regardless of the treatment applied. They are statistically superior to those of brown cane sugar (0.13±0.04 and 0.14±0.08 g/100g). No protein was determined in white cane sugar.

Flavonoid contents
The flavonoid contents of the studied coconut sugars reported in Table 1 range from 2.87±0.98 (PB121+, T3) to 7.25±1.95 mg/100g (PB113+, T1). Significant differences exist between the sugars of the studied coconut cultivars and those of the sugarcane controls (Pinter< 0.001).
Regardless of the treatment applied; 1.2 or 3, the PB113+ hybrid (7.25±1.95; 4.44±0.83 and 3.54±0.75 mg/100g) provides sugars that are statistically richer in flavonoids than the sugars of the other two cultivars.
The first group consists of the sugars produced by treatment 1. Thus, PB113+ (7.25±1.95 mg/100g), PB121+ (6.31±1.02 mg/100g) and GOA (4.60 mg/100g) contain respective levels of flavonoids at treatment T1 (7.25 ; 6.31 and 4.60±0.88 mg/100g), which are higher than the sugars of the second group, from treatment 2, (4.44±0.83; 3.92±0.13 and GOA 3.22±0.44 mg/100g; respectively for the same cultivars). The lowest levels are recorded with the sugars from treatment 3. In general, the protein acts as a substrate in the Maillard reactions that occur in the production of coconut sugar. Thus, high levels could influence the quality of coconut sugar (Naknean andMeenune, 2016).
Sugars or carbohydrates, of general formula (CHO)n, are generally the macromolecules that are primarily biosynthesized by plants. They constitute the major energy reserve that supports the metabolism of plants.
In addition, several metabolic cycles, including the glyoxylate cycle, convert proteins and lipids into carbohydrates.
Thus, the energy value (EV) of coconut crystal sugar is mainly dependent on its carbohydrate content. It has been shown that white cane sugar is more energetic than coconut sugars. However, for a given cultivar, the energy value increases with temperature. Indeed, heat treatments, especially cooking, increase the protein, lipid and ash content of food (Antoine et al., 2010). These molecules have been used in the calculation of the energy value of sugars and even participate, as far as proteins and lipids are concerned, in neoglucogenesis.
Over the past decade, there has been considerable interest in bioactive compounds in foods. The various researches on the phytochemical profiles of foods have focused on the role of their consumption in the prevention of diseases related to oxidative stress.
Among these compounds of nutritional interest, polyphenols have been widely highlighted for their health benefits (Acosta-Estradaet al., 2014).
The results of this study reveal that sugars from coconut cultivars are much richer in polyphenols than brown cane sugar, which contains very little polyphenols while its white counterpart does not.
The different cane sugar refining operations for the removal of impurities and decolorization of raw sugar would affect the amount of polyphenols in the cane sugars. On the other hand, there is a temperature depressing effect on the polyphenol content of coconut sugars with a decrease of about 50% from the first to the third treatment.
Most thermal processes lead to a degradation of phenolic compounds.

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These differences could be due to the fact that the sap from coconut inflorescences contains more polyphenols than the water in the nuts. Due to its greater involvement in the plant's life, coconut sap contains more polyphenolic elements than coconut water (Konan et al., 2013).
Among all phenolic compounds, flavonoids are the most abundant.
The flavonoid contents of coconut sugars, like total polyphenols, are all higher than those of brown cane sugar. The PB113+ hybrid is also predominant. The presence of polyphenols is more marked in the sugars from the first treatment.
This is thought to be due to the degradation of certain polyphenolic molecules under the effect of heat and the action of polyphenol oxidase enzymes (Konan et al., 2013), which are activated when the firing temperature is between 60 °C and 100 °C.
Polyphenolic compounds such as flavonoids are important antioxidants that protect biological macromolecules from degradation (Xia et al., 2011).
In addition, various epidemiological studies have shown the existence of an inverse correlation between the consumption of polyphenol-rich foods and the risk of developing cardiovascular disease.
However, the available data on the effects of polyphenols on human cancers are more disparate. Their action on human cancer cell lines is frequently protective and induces a reduction in the number of tumors and their growth

Conclusion:-
Our results reveal that within each cultivar, the different treatments applied induce an increase in energy value. On the other hand, the total polyphenol and flavonoid contents decrease when the temperature increases. The functional characterization of crystalline sugars from the sap of three coconut cultivars according to the time/temperature couple shows that these sugars are an important source of total polyphenols with contents varying from 34.64 to 143.12 mg/100g.
It is treatment 1 that provides a significant amount of polyphenols.
No polyphenolic compounds have been dosed into the white cane sugar. Regardless of the treatment applied; 1,2 or 3, the PB113+ hybrid (7.25±1.95; 4.44±0.83 and 3.54±0.75 mg/100g) provides sugars that are statistically richer in flavonoids than the sugars of the other two cultivars.
Coconut sugars from treatment 1 are less energetic (332.47 to 336.17 Kcal/100g) than those from the other two treatments. On the other hand, brown (386 Kcal/100g) and white (401 Kcal/100g) sugars from sugar cane are more energetic than those from coconut.
In view of all the above, coconut sugars, especially those from treatment 1, are natural sweeteners with a low energy value. In addition, they are rich in polyphenols and flavonoids, unlike refined cane sugar and its red counterpart which contains very few nutrients.

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Thus, coconut sugars produced in Côte d'Ivoire can be considered as a phytonutrient substitute, capable of replacing sugarcane sugars.

Contribution of the authors
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.