Value Added Gummy Jelly from Palmyra Palm (Borassus flabellifer Linn.)

The palmyra palm (Borassus flabellifer Linn.) is a multipurpose tree. It is commonly found along the coasts of Africa, South Asia and Southeast Asia due to its strong tap root system’s ability to store a large volume of water and raise the water table level in the surrounding area. Several uses of this plant include beverages, food, medicine, fiber and timber. Unfortunately, due to the short shelf-life of palmyra palm fruit, more than 60% of the annual fruit yield is lost within 10 days of harvesting, and there is limited commercial use of ripe palm fruit. As a result, the physical properties, physicochemical properties, and proximate composition of value-added gummy jelly from palmyra palm were evaluated. The results showed that up to 26% (w/w) of fruit juice (prepared by mixing the mesocarp of ripe palmyra fruit with water (at a 1:1 w/w ratio) and then removing the insoluble pulp) can be added to the gummy jelly recipe with significant effects on textural and color characteristics, as well as changes in moisture, protein, carbohydrate and energy content. Keyword. Palmyra palm, gummy jelly, value added product


Introduction
The palmyra palm (Borassus flabellifer Linn.) is a sugar palm that is commonly grown in Africa, South Asian (including India, Bangladesh and Sri Lanka), and Southeast Asia (for example, Thailand, Myanmar, Vietnam, Cambodia, Indonesia and Malaysia) [1,2]. This plant is also called by various names depending on different languages, such as, Talgachh and Tarkajhar in Hindi and Bangali, Lulu or Tadi in Telugu, Karimpana in Malayalam, Fan palm, Toddy palm, Tala palm and Brab tree in English [3]. This perennial plant has a maximum life span of 100 years. It can reach a height of 30 meters and bear fruit in 15 and 25 years in areas with adequate water and in arid areas, respectively [4]. Palmyra trees are typically planted near waterbodies such as lakes, rivers, and wells since their strong tap root system can penetrate up to 5 ft radially round the topsoil and 5-10 ft deep in the soil, bind the sandy soil around them, absorb moisture and store water. As a result, water resources are protected [4,5], storm or hurricane speeds are reduced, and soil erosion is prevented [3].
Palmyra trees have nearly 800 applications, including beverages, food, medicine, fiber, and timber [6]. Palmyra products are claimed to have a variety of pharmacological properties, including antiinflammatory, antiarthritic, cytotoxic, antibacterial, analgesic, antioxidant, antipyretic and hypoglycemic activities [7]. The pharmacological properties of each part of the palmyra palm are listed in Table 1. Table 1. Pharmacological properties of each part of palmyra palm.

Part of the palmyra palm
Pharmacological properties Ref.
Seed and seed coat extract Antimicrobial activity [3,8] Male inflorescence (flower) Anti-inflammatory activity [3] Young roots Diuretic agents, anthelmintic, coolant, and treatment of respiratory diseases [9] Palm fruit Anti-inflammatory, anti-oxidant and hydration properties, prevention of malnutrition on children and adults [10,11] Fruit pulp Reduction of skin inflammations, treatment of nausea and vomiting [3] Spadix (blossom) Treatment of heartburn and enlarged spleen and liver [3] Flower sap Tonic, laxative, diuretic agents, stimulant, and amebicide [3,12] Palm sugar Treatment of liver disorder [12] Toddy Ulcer treatment [9] Neera (palm nectar, juice) Controlling gastric problems and ulcer treatment [3] According to the palm sugar global market trajectory and analysis report [13], the palm sugar market was valued at USD 1.7 billion in 2020 and is expected to reach USD 2 billion by 2027, with a compound annual growth rate (CAGR) of 2.1% from 2020 to 2027. Aside from palm sugar, all parts of the palmyra tree provide several useful products, as presented in Table 2. The total income from one palmyra palm is approximately USD 230-256. In one acre of land, 400-500 palmyra trees can be planted [14]. An acre of land with palmyra palms could generate a total annual income of USD 92,000-128,000. As a result, this plant can provide a year-round source of income for agricultural families.  [3,4,14] The most valuable part of the palmyra palm is the fruit. Like all Borassus species, the palmyra palm has male and female flowers on separate plants. Fruits with a black to brown husk and a diameter of 10-18 cm develop after pollination. Each fruit contains 1-3 seeds [8], as shown in Fig. 1. The seeds (endosperm) of an unripe fruit can be eaten as a fruit [9]. The unripe fruit of the palmyra palm is extremely difficult to consume since the hard rind and fibrous portion must be removed before consumption [15]. However, when the fruit is ripe, the fibrous outer layer of the fruit can also be eaten raw, roasted, or boiled [9].
The edible pulp of the ripe palmyra palm is a soft orange-yellow mesocarp that accounts for approximately 51.07% of the total fruit (Fig. 1). This sugary part is slightly bitter and rich in vitamin C and β-carotenoids at 16.9 mg per 100 g of fruit pulp and 3 ppm per g of fruit pulp, respectively [1,2,[16][17][18]. Moreover, it is considered to be a good source of pectin, iron, phosphorus, calcium, magnesium and antioxidants [19].
The pulp can be extracted manually or with a fruit pulp extractor using a pulp-to-water ratio of 1:1 or 1:2 [16,20,21]. It can be processed into soft beverages, toffee, cakes, jam, jelly, ice cream, sweets, cordials and other delicious food products [19,[22][23][24]. Unfortunately, over 60% of the annual fruit yield of the palmyra palm is lost within 10 days after harvesting due to its high moisture content, resulting in a short shelf-life [1,2,16] and limited commercial use of ripe palm fruit [16]. It is estimated that approximately 10,000 tons of fruit pulp are wasted each year [18]. The global market for jellies and gummies was valued at USD 13.9 billion in 2018, and it is expected to expand at a CAGR of 3.5% between 2019 and 2025. This market's size has grown as a result of the growing candy industry, the vegan population, and increased consumer spending. The main factors affecting consumers' purchasing decision are usually distinctive flavors, shape, textures, product design, packaging and sugar content [26].
Gummy jelly is one of the confectionery products, often containing high sugar (especially sucrose and glucose syrup) as well as one or more gelling components, flavorings, coloring and food acid [27,28]. This product is usually produced by heating a sugar solution with gelling components, pouring it into various shapes of molds, and then removing it with powder after hardening [29]. In confectionery gels, sucrose is used as a sweetener while glucose syrup is often added more than sucrose to slow down sucrose crystallization and sucrose molecule migration [29,30]. Moreover, glucose syrup is used to reduce water activity, which prevents microbial growth [31].
The gelling components used in confectionery gels are polysaccharides, such as thin-boiling starch, pectin, amylopectin, agar, and gum arabic [29]. Pectin, a linear chain of galacturonic acids, is usually extracted from apple pomace or citrus peel [32]. In confectionery gels, high methoxyl pectin or pectin with a degree of esterification greater than 50% is combined with sugar and food acid in order to produce a firm gel [29]. Some of the most common food acids are malic acid, citric acid, fumaric acid, adipic acid and tartaric acid. Food acids can also lower pH and improve product shelf life. In confectionery production, a 50% citric acid solution is usually added at the end of gel processing [29,31].
Several studies have recently developed gummy jelly containing natural plant extracts and fruit juice, such as Psidium guajava leaf extract [33], pineapple and papaya peel powders [34], strawberry syrup [35], honey and propolis [36], Thunbergia laurifolia L. extract [37], rosemary (Rosmarinus officinalis L.) extract [38] and Babbler's Bill leaf [39]. The purpose of this study was to investigate the physical properties, proximate composition, and energy content of a value-added gummy jelly product made from palmyra palm fruit pulp.

Preparation of palmyra palm fruit juice
Ripe palmyra palm fruits (Borassus flabellifer Linn.) were harvested approximately 2-3 months after pollination in Baan Lard district, Phetchaburi province in Thailand. Each fruit weighed 1-2 kg. The fruits were washed under running tap water and the exocarp ( Fig.1) was peeled. The seeds were removed, and the fruit pulp (mesocarp in Fig.1) was then manually extracted into water (pulp:water ratio = 1:1) [16]. After that, the extract was sieved to remove the insoluble pulp and obtain palmyra palm fruit juice. The juice was pasteurized at 65ºC for 5 min [1,40] and stored at -18ºC until used.

Determination of pH and aw
In order to determine pH, 5±1 g of samples were cut into thin slices and mixed with distilled water (sample:water = 1:3, w/w) [41]. The mixture was heated at 60±2 °C and constantly stirred until completely dissolved. It was cooled at 25°C before being measured with a pH meter (pH510, Eutech Instruments, Klang Selangor D.E., Malaysia), which had previously been calibrated with buffer solutions of pH = 7 and 4 [42].
The water activity of gummy jelly samples was determined at 25±2°C using a water activity meter (Aqualab, CX-2, Decagon Device, Inc., Pullman, WA, USA), which had previously been calibrated with standard solutions of aw = 0.250 (13.4 mol/kg LiCl), aw = 0.5 (8.57 mol/kg LiCl), and aw = 0.984 (0.5 mol/kg KCl) [42]. 2±0.5 g of food product was placed in the sample holder of the water activity meter. All analyses were performed in triplicate.

Color analysis
Color values of samples were measured at room temperature using a Hunter colorimeter (Color Quest 45/0, Hunter Associates Laboratory, Inc., Reston, VA) as described by Charoen et al. [44]. The instrument was calibrated prior to measurement using standard white and black reflector plates [33]. Four readings per sample were conducted by changing the position of the sample. Three samples of each formulation were measured in each replicate. CIE L*a*b* color parameters (L*: lightness, a*: a positive a* represents redness and a negative a* represents greenness, and b*: a positive b* represents yellowness and a negative b* represents blueness) for 10° vision angle and D65 illuminant were measured.

Carbohydrate(%) = 100 -(moisture+ash+lipid+protein) (1)
The energy content of each sample was calculated by multiplying the percentages of lipid, protein and carbohydrate by 9, 4 and 4, respectively, and then adding all of the multiplied products together. The energy content in calories was then multiplied by a factor of 4.185 to convert it into kJ [46].

Statistical analysis
Every analysis was carried out in triplicate, with three subsamples. Significant differences among averages were analyzed in a completely randomized design (CRD) with one-way analysis of variance (one-way ANOVA) and Duncan's multiple range test (DMRT) at a 95% confidence level using IBM SPSS Statistics 26 (IBM Corporation, Armonk, NY). Table 4 presents the pH and aw of gummy jelly with different concentrations of palmyra palm fruit juice. In this research, citric acid was added to every sample to obtain a pH of ≈ 2.0-3.7, which is the recommended pH range for gelation of high methoxyl pectin [47]. In acidic conditions, pectin chains have lower electrostatic repulsive forces since there is less dissociation of carboxyl groups of galacturonic acid residues [48]. Gummy jelly samples with the addition of palmyra palm fruit juice had a slightly higher pH than the sample without fruit juice (p<0.05). Since the pH of palmyra fruit juice was 4.52-4.87, the addition of fruit juice could lead to a slight increase in the pH of the final product. As concentrations of palmyra palm fruit juice increased, aw of the samples tended to slightly increase since palmyra palm fruit pulp had a high moisture content of 82.13±0.42%. Some gummy jelly products supplemented with natural extracts, such as Psidium guajava leaf extract, Babbler's Bill leaf, and juçara and passion fruits, also have aw of 0.7-0. 8 [44, 39, 49]. *The fruit juice was prepared by mixing the mesocarp of ripe palmyra fruit with water (at a 1:1 w/w ratio) and the insoluble pulp was then removed.

pH and aw
Data are presented as mean ± SD (n = 3). Different superscripts within the same row indicate significant difference between the samples in the Duncan's multiple range test (p < 0.05).

Texture profile analysis
Texture profiles are one of the important factors affecting consumer acceptability. The texture profiles of gummy jelly with and without the addition of palmyra palm fruit juice are shown in Table 5. The texture profiles studied in this research included hardness, adhesiveness, springiness, cohesiveness and chewiness. The force required to compress a food product by a given amount is referred as its hardness [41].
Adhesiveness is defined as the energy required to overcome the attractive forces between the food surface and the surface of other materials contacting the food [50]. Springiness is elastic recovery when the compressive force is removed. Cohesiveness is the strength of the internal bonds in the food sample. Chewiness is the amount of energy required to chew a solid food product until it is ready for swallowing [41].
The samples with 23-26% (w/w) fruit juice tended to have higher hardness, springiness, cohesiveness, and chewiness as compared to the gummy jelly without the addition of fruit juice. Since there is approximately 11.6-13.3% sugar found in palmyra fruit pulp [3], the addition of fruit juice to the product can also increase the sugar concentration of the product. Sugar concentration in confectionery products can reduce the hydration of pectin molecules [51]. The hydrophobic interactions of methoxyl groups could also stabilize the gel structure [48]. Furthermore, because palmyra palm fruit is a good source of pectin [19,52,53], adding the fruit juice can increase pectin in the food system, resulting in a slight increase in gel strength and, as a result, increasing the hardness, springiness, cohesiveness, and chewiness of the product. A previous study on gummy candies enriched with pineapple and papaya peel powders also found that the modified candies were firmer and more elastic than the control samples [34]. Unlike other texture profiles, the adhesiveness of samples decreased as concentrations of palmyra palm fruit juice increased. In gummy jelly, adhesiveness is usually undesirable [53], since high adhesiveness indicates that the food product would stick to other non-food surfaces, such as the teeth, palate and tongue [50]. Therefore, the product with 26% (w/w) fruit juice, which provided the lowest adhesiveness, was highly recommended over the gummy jelly without fruit juice. *The fruit juice was prepared by mixing the mesocarp of ripe palmyra fruit with water (at a 1:1 w/w ratio) and the insoluble pulp was then removed.
Data are presented as mean ± SD (n = 3). Different superscripts within the same row indicate significant difference between the samples in the Duncan's multiple range test (p < 0.05).

Color
The color parameters (L*, a*, b*) of gummy jelly with various concentrations of palmyra palm fruit juice are presented in Table 6. As concentrations of fruit juice increased, all parameters significantly increased (p<0.05). The products with palmyra palm fruit juice were orange-yellow (Fig.3) since the fruit pulp is bright yellow or orange (Fig.1) according to the high amount of pro-vitamin A, carotenoids [1,18,54]. Srithuvaragan and Anuluxshy could extract pigments from palmyra palm fruit pulp and the yield of β-carotene determined in the literature was 3 ppm per g of fruit pulp [18]. As a result, the palmyra fruit pulp can also be used as a natural food colorant. *The fruit juice was prepared by mixing the mesocarp of ripe palmyra fruit with water (at a 1:1 w/w ratio) and the insoluble pulp was then removed.
Data are presented as mean ± SD (n = 3). Different superscripts within the same row indicate significant difference between the samples in the Duncan's multiple range test (p < 0.05).

Fig. 3.
Gummy jelly with 26% palmyra palm fruit juice. Table 7 presents the proximate composition of the gummy jelly with different concentrations of palmyra palm fruit juice. There was no significant difference in lipid, ash and crude fiber between samples with and without the addition of fruit juice (p≥0.05) since there were low levels of these compositions in the fruit pulp (approximately 2.03-2.06% of lipid, 1.23-1.27% of ash and 0.49-0.52% of fiber) [2]. The addition of fruit juice increased the moisture and protein content of the product while significantly reducing the carbohydrates, resulting in a lower energy content. Although the palmyra palm fruit is high in sugar and carbohydrates [2,3], the pulp must be extracted using water [16,20,21], resulting in the diluted fruit juice and a reduction of carbohydrates in the final product. *The fruit juice was prepared by mixing the mesocarp of ripe palmyra fruit with water (at a 1:1 w/w ratio) and the insoluble pulp was then removed.

Proximate composition
Data are presented as mean ± SD (n = 3). Different superscripts within the same row indicate significant difference between the samples in the Duncan's multiple range test (p < 0.05).
ns The samples were not significantly different (p≥0.05).

Conclusions
Ripe palmyra fruit pulp can be used to produce gummy jelly with significant effects on the textural and color characteristics of the product, as well as a slight increase in moisture and protein content, but a decrease in carbohydrate and energy content. Furthermore, the addition of fruit juice could also reduce the undesired adhesiveness of the final product. The palmyra palm fruit juice concentration in the product is recommended to be up to 26% (w/w) of fruit juice (prepared by mixing the mesocarp of ripe palmyra fruit with water (at a 1:1 w/w ratio) and then removing the insoluble pulp). This product's production could be potentially profitable for agricultural families.