Effect of different concentrations of pulverized mesocarp of Citrus paradisi Macf. on the bromatological characteristics of spray‐dried lemon juice powder

Abstract The aim of this research was to evaluate the effect of different concentrations of pulverized mesocarp of Citrus paradisi Macf. as a drying aid on the bromatological characteristics and yield of spray‐dried lemon juice powder. Five concentrations of grapefruit mesocarp encapsulant (0.4, 0.8, 1.2, 1.6, and 2.0% (w / w)) and maltodextrin DE 10 (1.2%, w / w) were evaluated as encapsulant agents. The highest yield (46.76%) was obtained with 1.2% of grapefruit encapsulant. Water activity and ash content were inversely proportional to the added encapsulant concentration. The highest moisture value was obtained with 0.4% and the highest soluble solids with 2.0%. For all treatments, the pH level did not change, except at 0.4% (it was lower). The concentrations of the encapsulants significantly affected the evaluated characteristics, except for the proteins.

main components, calculated in relation to the dry matter, are 44% sugars, 33% cellulose, and 20% peptic substances. It also contains flavonoids, amino acids, and vitamins (Fennema, 1993). However, apart from these nutritional properties, this material is currently wasted during the processing of the grapefruit.
The limited availability of materials used as encapsulating agents and the fact that they have a high cost evidences the need to identify unconventional sources of biomolecules or the like, with functional characteristics similar to those existing. This, along with the nonutilization of by-products generated in the industrial processing of citrus fruits, led to the development of Alcantara and Escotto's (2014) study, in which an encapsulating agent was obtained from the grapefruit mesocarp.
As a follow-up to the aforementioned study, the present investigation proposes the evaluation of different concentrations of the encapsulating agent (obtained from the grapefruit mesocarp by Alcantara & Escotto, 2014), which are evaluated in the spraydrying of Persian lemon juice. This is proposed as an alternative to the existing encapsulants in the market, so as to take advantage of a by-product generated in the industrial processing of grapefruits, add value, and enable the industrialization and commercialization of a more durable, alternative product that conserves the maximum properties of the encapsulated juice.
Citrus fruits are seasonal; therefore, prices usually fall at the peak of production. For producers, this represents significant losses as the prices do not compensate the production costs. The short shelf life of these species causes losses and can negatively influence trade and consumer confidence (Alcantara & Tejada, 2012). For instance, in a given period, lemons disappear from the market or reach prices so high that most consumers cannot afford. The same happens with other tropical fruits, such as avocado, mango, pineapple, and others.
An alternative to mitigate the inconveniences faced by lemon producers and consumers is processing the fruits during the high-production season. Dehydration of Persian lemon juice was performed due to its nutritional characteristics, short shelf life, and variability in the behavior of prices, given the seasonality of its production.

| Raw materials
The fruits of Citrus latifolia Tanaka were acquired in Santiago de los Caballeros, Dominican Republic, and were used to obtain the drying aid, according to Alcantara and Escotto's (2014) methodology. Maltodextrin DE 10 was used for the encapsulation of the control treatment.

| Experimental design
For this study, a completely randomized design was used to evaluate the effect of five concentrations of encapsulant from Citrus paradisi (0.4, 0.8, 1.2, 1.6, and 2.0%) as independent variables on yield, physicochemical characteristics (pH level, water activity, and solids soluble), and composition (moisture, protein, ash, carbohydrate content, total phenolic compounds, total flavonoids, and ascorbic acid) of the encapsulated lemon juice. Additionally, 1.2% maltodextrin 10 DE was used as a control. In total, there were six treatments with three replicates, resulting in 18 experimental units.

| Process for the lemon (Citrus latifolia Tanaka) juice encapsulation
The fruits of C. latifolia Tanaka were received in the Food Processing Plant of ISA University and then weighed and selected according to color, size, and appearance (without physical defects). After selection, they were treated with a sodium hypochlorite solution at 100 ppm and allowed to drain for 10 min. Then, they were weighed again and split into two halves. The juice was extracted using manual juicers and filtered using a No. 32 mesh Tyler sieve.
The treatments were prepared by adding 0.5% of tricalcium phosphate as an anti-adherent (to avoid stickiness and decrease the encapsulated product's hygroscopicity), and the concentration corresponded to the encapsulating agent (i = 0.4, 0.8, 1.2, 1.6, and 2.0% pulverized grapefruit mesocarp; 1.2% maltodextrin DE 10). The percentages were established based on the lemon juice. It was mixed in an Osterizer 4655 electric mixer at full speed for a minute, filtered through a No. 32 Mesh Tyler sieve, to retain any possible particles and avoid obstructions in the atomization needle, and then dried in the Spray Dehydrator YC-015 SD.
The drying conditions were kept constant: inlet air temperature 130°C, spray air pressure of 3.4 bar, air blower: 4 kg/cm 2 , feed rate: 0.9 L/hr, outlet air temperature 75°C. The particle size was 0.7 mm.
The obtained powder was immediately packed and vacuum sealed in bags. It was stored at 25°C until evaluation.

| Yield
Yield was evaluated using the methodology described by Lozano (2009), applying the following formula: The values of grams offered were calculated from the grams of material, and the juice volume was used as the starting material, according to the following equation:

| Physicochemical variables
Samples were prepared by dissolving 1 g of encapsulated lemon juice in 10 ml of water for the evaluation of the physicochemical variables, except for water activity, moisture, protein, and ash, for which the powder was used directly.
pH: This determination was made by potentiometry at 20°C using a Hach SensION+ 5050T pH meter.

%Yield = Grams obtained
Grams offered × 100 Water activity was determined using the Rotronic HygroPalm (HP-23), by placing 1 g of encapsulated lemon juice in the cell of the device and waiting for the reading.
Soluble solids were determined using the method 11-15 of Hart and Fisher (1971), using a refractometer (Atago).

| Compositional variables
Moisture was determined according to the International AOAC Method (934.01), using the following formula: Proteins were determined according to Method 2001.11 of the International AOAC.
Ash was determined using Method 923.03 of the International AOAC.
Carbohydrates were determined by applying the phenol-sulfuric method (Dubois, Gilles, Hamilton, Rebers, & Smith, 1956). The intensity of the orange color was read at 480 nm on a Hach DR 3900 spectrophotometer, against a target prepared in the same manner using water. The amount of carbohydrates present in the sample was calculated from a standard curve prepared with the carbohydrate of interest, treated in the same way as the problem.
Total phenolic compounds were determined using the Folin-Ciocalteu technique (AOCS, 1990). The calibration curve was prepared using a gallic acid standard solution (0.1 mg/ml); to determine the phenols in the sample, the absorbance was measured at 760 nm on the Hach DR 3900 spectrophotometer. The results were expressed as mg of gallic acid equivalent per g sample.
Flavonoids content was determined using Liu et al.'s (2002) method: a calibration curve was prepared using a standard quercetin solution (0.1 mg/ml). The absorbance was measured at 510 nm immediately before 30 min, using the Hach DR 3900 spectrophotometer. The results were expressed as mg of quercetin equivalent per g sample.
Ascorbic Acid: was determined using the method reported by Hung and Yen (2002). The calibration curve was prepared with ascorbic acid, oxalic acid, and distilled water. Absorbance was adjusted to zero, samples were prepared (100 μl aqueous extract, with 900 μl of 2,6 dichlorophenolindofenol), and vitamin C was measured on the Hach DR 3900 spectrophotometer at a wavelength of 515 nm. The results were expressed as mg of ascorbic acid equivalent per gram of sample.

| Statistical analysis
The obtained data were evaluated by one-way ANOVA. Means were separated using Tukey's test (p < 0.05). These analyses were performed using Statistix version 8.0. For the representation of the results, the arithmetic mean was used as the central measure ± SD of three replicates; for the means separation, the Tukey test was applied with a 95% reliability. Figure 1 shows the results of the encapsulated lemon juice yield obtained in this investigation. The yield ranged from 28.15% to 46.76%, corresponding the highest value to the T 12 treatment, followed by the T 20 treatment (38.31%) and the control (36.67%).

| Effect of different concentrations of encapsulant retrieved from Citrus paradisi Macf. mesocarp on yield of spray-dried lemon juice
These results can be explained by Caliskan and Dirim's (2013) argument, who state that an increase in the amount of encapsulating agent after a certain interval is not efficient in yields but increases the process cost. Similarly, Fang and Bhandari (2012) found that increasing the maltodextrin concentration above 30% does not have a significant effect on the increase in obtained product yield, considering this concentration as the amount required for a successful drying process of berry juice. In contrast, Mendoza (2015) Moisture Content(%) = Wet sample weight − Dry sample weight Wet sample weight × 100 F I G U R E 1 Yield of Spray-dried Lemon Juice stated that as the concentration of maltodextrin increases from 20% to 30%, the yield of the product increases because the content of solids in the formulation increases. This is because maltodextrin also causes an increase in the particles size, which makes them less fine; the lowest yield (48.08%) was obtained using 15% of maltodextrin, while the highest value was 74.85% for the treatment, with 30% of this encapsulant.
The yield values found in this study are similar to those obtained by Rivas (2010)

| Effect of different concentrations of encapsulant retrieved from Citrus paradisi mesocarp on the physicochemical characteristics of spray-dried lemon juice
According to the results of the physicochemical characteristics of encapsulated lemon juice (Table 1), the concentration of pulverized mesocarp from C. paradisi Macf. significantly affects the studied variables. Tonon, Brabet, and Hubinger (2008) argue that the final characteristics of a powdered product obtained by spray-drying depend on some process variables, such as liquid characteristics (solids and viscosity). Zapata, Rojano, and Cortes (2015) ensure that through the drying processes, to which the fruit juices are subjected, various physicochemical changes are generated; they indicate that because the heat directly interferes with spray-drying, thermal degradation is the most important deteriorating phenomenon.
The results of the present study are corroborated by what was observed by Mendoza (2015), who indicated that all his response variables presented significant differences with respect to the percentage of maltodextrin used to spray-dry a whey-based and mango pulp-based products.
The mean pH values of the treatments of this research (Table 1) are statistically equal to those of the control, with the exception of the T 04 treatment (juice with 0.4% of encapsulating agent of grapefruit mesocarp); they are also similar to those found by Badillo (2011) for Persian lemon dehydrated in microwaves and dehydrated in trays, corresponding to 3.2-3.5, respectively. Badillo (2011) expresses that acidity increases in dehydrated products because their salts dissociate. The results obtained could also be due to the occurring temperature gradients that cause water diffusion and change its properties in the interior of the foods (Rocca, 2010).
Regarding water activity ( TA B L E 1 Results for the physicochemical characteristics of spray-dried lemon juice formed, which undergo some collapse during the drying process, giving high values of water activity; the lowest values corresponded to the treatments with higher encapsulant concentrations perhaps because in these cases, the particles showed more stability against the temperature, resulting in a more efficient drying. Mendoza (2015) suggests that at a high spray rate (26,000 rpm) and constant temperature, the increase in the maltodextrin concentration leads to the formation of larger particles, with greater area of heat and mass transfer, decreasing product moisture and its aw. This argument is also confirmed by Torres (2009), who states that drying and concentration processes are used to reduce the water content of a food. Thus, he found that the composition and inlet air temperature influence the value of aw of the dehydrates by increasing solutes concentration and decreasing water activity; he concluded that with a high additive amount (22% maltodextrin) and high inlet air temperature (150°C), lower values (0.165) and therefore more stable solids are obtained.
Additionally, Rodriguez, González, Grajales, and Ruiz (2005) tested for the atomized fig juice, whose dry powder particles were very hygroscopic when the particles had little amount of additive, so that once the powder was formed, being suspended in the humid air, they could be partially hydrated.
The evaluated samples presented aw values between 0.3310 and 0.3687, similar to those obtained by Mendoza (2015), who obtained values between 0.205 and 0.368; these values are also close to those reported by Queck, Chok, and Swedlund (2007) in the drying of watermelon juice (aw ~ 0.3), which according to the mentioned author, allows to consider these food products as microbiologically stable, having a lower water content available for the development of biochemical reactions (aw < 0.6). Marques, Ferreira, and Freire (2007) and Caliskan and Dirim (2013) report that values from 0.2 to 0.4 ensure the stability of the product against reactions of darkening and hydrolytic reactions, lipid oxidation, autoxidation, and enzymatic activity.
The soluble solids' results obtained in this research (Table 1) show that the treatments evaluated are statistically equal to control, except for the treatment with 2.0% of encapsulating agent. These values are within the range reported by Kimball (2002) andMendoza (2003) for dehydrated lemon (8 and 15°Brix). However, these are lower than the value published by Rivas (2010) Mendoza (2015) asserts that the proportion of nutrient content in the products evidences the influence of the materials and processing process. The moisture content of all the treatments evaluated in this study is similar (2-6%) to that reported by Castro (2014) for spraydried clarified purple nopal juice and to that observed by Saenz, Tapia, Chávez, and Robert (2009) for drying of nopal juice. They are also congruent with those found by Mendoza (2015), who reported values between 1.48% and 5.84%, the highest corresponding to the lowest concentrations of maltodextrin used; additionally, the product moisture changed from 4.70% to 2.52% by increasing the maltodextrin concentration from 20% to 30%. Similarly, Mishra, Mishra, and Lata (2013) reported that the increase in maltodextrin concentration significantly decreases the moisture content of the powder obtained from amla currant juice (5.6%-3.8%, with maltodextrin values of 5%-9%).

| Effect of different concentrations of encapsulant retrieved from Citrus paradisi mesocarp on spray-dried lemon juice composition
These facts can be explained with what is exposed by Abadio, Domingues, Borges, and Oliveira (2004), who state that in a spraydrying system, the water content of the feed effects the final moisture content of the powder obtained. The authors explain that the addition of maltodextrin to feed before drying increases the total solids content and reduces the amount of water available for evaporation, which according to Queck et al. (2007), means that powders with lower moisture content could be obtained by increasing the percentage of added maltodextrin. Table 2 shows that the concentration of the encapsulating agent used does not affect the protein content of the dehydrated product; the treatments evaluated are statistically equal to the control. The values found are higher than reported by Caez and Jaraba (2012) for mango juice encapsulated with maltodextrin (0.59%) and close to that observed by Mendoza (2015) for the powdered product obtained from whey and mango pulp (2.56%).
On the other hand, Naddaf et al. (2012) found that the best protective matrix of proteins was the maltodextrin at 5% and 7% when spray-drying natural orange juice using maltodextrin and gum arabic.
Concerning the ash content, only the treatment with 0.4% of the encapsulating agent is different from the control and is the one with the highest value (16.07%). In general, the ash content decreased as the concentration of the added encapsulating agent increased.
The ash percentages found are higher than the values obtained by Caez and Jaraba (2012), who reported 0.429% of ash in mango juice microencapsulated with maltodextrin DE 19. These values are also higher than those obtained by Rivas (2010) in enzymatically stabilized cherimoya juice that was microencapsulated using 50% of maltodextrin, corresponding to values between 1.23% and 2.12%.
Contrary to what was published by Badillo (2011), who expresses that the ash percentage increases with dehydration because of the desiccation progresses, the water content decreases in Persian lemon dehydration in microwaves and trays, allowing the minerals elements be in higher concentration.
The results obtained for carbohydrates show that only the T 04 and T 12 treatments are equal to the control; the others present a greater amount of carbohydrates, indicating that the pulverized grapefruit mesocarp has greater protective effect of this variable. According to the results obtained for ascorbic acid content, Table 2 shows that only the treatment with 0.4% of pulverized grapefruit mesocarp has a lower content of ascorbic acid than the control, so that the other treatments provide better results, which favors the research.
The data shown further suggest that the ascorbic acid content also increased as the encapsulant concentration is increased. The treatment that showed greater protection to ascorbic acid was the encapsulating agent of grapefruit with a concentration of 2.0%.
In Gonzalez, Gonzalez, and Rosales's (2011) spray-dried study of watermelon juice (Citrullus lanatus Thunb) using maltodextrin and gum arabic as encapsulating agents at concentrations of 0.5% and a mixture of both at the concentration of 0.5%, they determined that the treatment corresponding to 0.5% of the mixture of maltodextrin DE 10 and gum arabic (1: 1) w / w was better; they stated that in this treatment, the volatile compounds in the spray-dried powdered watermelon product did not show significant difference against the original extract.
The findings in this study are also confirmed by Liu (2014), who states that the pectin-starch relation influences the physical and functional properties of the encapsulated ascorbic acid microparticles; their results suggested that the proportion of starch-pectin influenced the encapsulation efficiency of ascorbic acid more than the type of starch.

| CON CLUS ION
The yield of the encapsulated lemon juice is significantly influenced using different concentrations of pulverized grapefruit mesocarp (0.4, 0.8, 1.2, 1.6, and 2.0%). The concentrations of pulverized mesocarp from creole grapefruit (C. paradisi Macf.), used in this research, significantly affect the evaluated physicochemical characteristics (pH, water activity, and soluble solids) of the encapsulated lemon juice. Raising the encapsulant concentration increases the pH level and decreases the water activity of the encapsulated juice.
Using different concentrations of pulverized grapefruit mesocarp (0.4, 0.8, 1.2, 1.6, and 2.0%) has a significant influence on the composition of the encapsulated lemon juice (percentage of moisture, ash, carbohydrate content, total phenolics, flavonoid content, and ascorbic acid content), except for the protein content of the juices.
As the concentration of drying aids increases, so does the content of bioactive components. From the doses used in this research, it was determined that 1.2% of grapefruit mesocarp could be used as an encapsulant for lemon juice during spray-drying.

ACK N OWLED G M ENTS
The authors thank Murcia and ISA Universities, and the FONDOCYT of the Dominican Republic.

E TH I C A L S TATEM ENTS
This study does not involve any human or animal testing.

CO N FLI C T O F I NTE R E S T
None declared.