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Article

Powdered Kombucha Flavored with Fruit By-Products: A Sustainable Functional Innovation

by
Maria de Fátima Dantas Linhares
1,
Thatyane Vidal Fonteles
1,
Lorena Silva de Oliveira
1,
Samira Barros de Souza
1,
Emilio de Castro Miguel
2,
Fabiano André Narciso Fernandes
3 and
Sueli Rodrigues
1,*
1
Food Engineering Department, Federal University of Ceará, Campus do Pici Bloco 851, Fortaleza 60440-900, CE, Brazil
2
Department of Metallurgical Engineering and Materials (DEMM) and Analytical Center, Federal University of Ceará, Campus do Pici Bloco 729, Fortaleza 60440-900, CE, Brazil
3
Chemical Engineering Department, Federal University of Ceará, Campus do Pici Bloco 709, Fortaleza 60440-900, CE, Brazil
*
Author to whom correspondence should be addressed.
Processes 2025, 13(9), 3020; https://doi.org/10.3390/pr13093020
Submission received: 30 July 2025 / Revised: 5 September 2025 / Accepted: 19 September 2025 / Published: 22 September 2025
(This article belongs to the Section Food Process Engineering)
Browse Figures
Versions Notes

Abstract

Kombucha is a fermented beverage usually commercialized in liquid form. This study developed a powdered kombucha, flavored with grape (GKP) and mango (MKP) peel extracts—derived from fruit processing by-products—through spray drying with 20% (w/v) maltodextrin as a carrier. The spray drying conditions were set to 160 °C inlet temperature and 0.5 L/h feed flow, yielding a maximum powder recovery of 34% for GKP. All powders presented moisture contents below 5%, with values of 4.2% for KP and GKP and 4.02% for MKP, ensuring microbiological safety and long-term stability. Water activity (aw) was also significantly lower in MKP (0.283) compared to KP and GKP (both 0.317). After spray drying, GKP retained up to 93% of TPC, while MKP retained 87%, and KP 82%. Morphological analysis by Scanning Electronic Microscopy (SEM) showed that flavored powders, especially GKP, presented spherical particles with fewer surface defects. Powder flow test showed that MKP presented the best flowability (flow index If = 2.55) compared to GKP (If = 1.71) and KP (If = 1.64 ± 0.02). The results demonstrate that incorporating fruit residues into kombucha and applying spray drying improves the functional and technological properties of this product, with potential applications in functional food formulations and dietary supplements.

1. Introduction

Kombucha is a fermented beverage traditionally obtained by fermenting sweetened black or green tea with a symbiotic culture of bacteria and yeast (SCOBY) [1]. During fermentation, microbial metabolism leads to the production of organic acids (acetic, glucuronic, and lactic acids), ethanol, carbon dioxide, B vitamins, and various bioactive compounds, including polyphenol derivatives and antimicrobial peptides [2]. These metabolites are responsible for kombucha’s reported functional properties, including antioxidant activity and modulation of gut microbiota [3], as well as its alleged anticancer [4] and anti-inflammatory effects [5]. However, the dynamic nature of this microbial consortium also introduces challenges for product standardization, safety, and shelf stability.
In its traditional liquid form, residual microbial activity after bottling can continue fermentation, leading to unpredictable increases in acidity, carbonation, and even ethanol content, which often exceed regulatory limits [6]. These factors not only affect flavor and consumer acceptance but also impart significant hurdles for commercial distribution, particularly under ambient conditions, calling for reformulation strategies that preserve health benefits while enhancing palatability and stability.
Spray drying represents a technological solution for addressing these issues. As a thermal dehydration technique widely applied in the food and pharmaceutical industries, spray drying enables the encapsulation of bioactive compounds and microbial metabolites into a stable, rehydratable powder [7]. When combined with carrier agents such as maltodextrin, spray drying protects sensitive components from thermal degradation, reduces hygroscopicity, and allows precise control over moisture content, particle size, and solubility [8]. Additionally, depending on inlet temperatures and formulation, microbial viability can be either preserved (yielding probiotic powders) or selectively inactivated, generating postbiotic formulations with functional effects and improved safety [9].
From a commercial standpoint, powdered kombucha offers several clear advantages: a longer shelf life, ambient storage, reduced transportation costs, and greater application versatility (e.g., in supplements, beverages, or functional food blends). Furthermore, the inclusion of fruit processing by-products as natural flavoring and bioactive sources not only enhances the organoleptic profile but also adds nutritional and environmental value. This upcycling approach aligns with the principles of the circular economy and clean-label innovation, which are increasingly demanded by the food market.
This study aims to develop a powdered kombucha product using fruit-derived agro-industrial residues as flavoring and functional ingredients. By combining microbial fermentation, sustainable ingredient valorization, and drying technology, a novel formulation is proposed that addresses the limitations of traditional kombucha while offering an innovative, shelf-stable alternative for the health-oriented market.

2. Materials and Methods

2.1. Raw Materials

In the present study, kombucha was produced by fermenting green tea (Camellia sinensis) purchased from the local market (Fortaleza, CE, Brazil). The beverage was then flavored using extracts from fruit residues. Mango peels (Mangifera indica ‘Espada’) and cashew apple bagasse (Anacardium occidentale L. ‘CCP 76’) were obtained from the juice processing industry in Fortaleza, Ceará, Brazil, while grape peels were obtained from the wine processing industry (Nova Trento, SC, Brazil). These residues were frozen at −20 °C and then subjected to freeze-drying (LioTop freeze dryer, model L101, São Carlos, SP, Brazil) for 12 h before being ground for use.

2.2. Fruit Residue Extract Preparation

The extracts were prepared by suspending the fruit residue powder in water at a solid-to-liquid ratio of 1:8 (powder:water). This ratio was determined through preliminary tests for the study. The phenolic compounds were extracted using a probe sonicator (Ultronique QR500, 19 kHz, and a maximum power of 500 W—Indaituba, SP, Brazil), equipped with a 13 mm titanium tip macro. The extractions were carried out in a glass-jacketed reactor (250 mL). The intensity of ultrasonic energy dissipated by the titanium tip was 75.34 W/cm2. The temperature was maintained at 25 °C using an external circulating water bath.

2.3. Kombucha Fermentation and Flavoring

Green tea was prepared using 1% w/v dried Camellia sinensis leaves from the local market, which were infused in water heated to 90 °C for 15 min. Then, the tea was filtered using a voile cloth to remove the leaves. No sugar was added. After reaching room temperature, the tea was transferred to a glass container (15 × 20 cm) and was inoculated with 10% w/v SCOBY (Symbiotic Culture of Bacteria and Yeast) and 10% v/v of the previously fermented batch [3]. Fermentation occurred at 28 ± 1 °C for 7 days (first fermentation).
The SCOBY used was produced and maintained in-house. The production follows a modified protocol from Li et al. [10]. Briefly, 30 g/L of sucrose was added to a green tea infusion (prepared as described above). The sweetened tea was then inoculated with 10% (v/v) of a previously fermented kombucha and incubated in a glass vessel covered with cheesecloth at 28 ± 2 °C for 7 to 15 days to allow a new SCOBY formation.
The second fermentation (flavoring) occurred by adding 20% (v/v) of each fruit residue extract to the kombucha. The beverages were transferred to screw capped PET bottles and sealed for carbonation. The bottles were incubated at 28 ± 1 °C for 48 h. The beverages produced were named Grape Kombucha (GK) and Mango Kombucha (MK). An unflavored kombucha (control sample) also underwent a second fermentation for carbonation and was used as the control sample. After the second fermentation, the samples were stored at 4 ± 1 °C until they were dried.

2.4. Production of Kombucha Powder by Spray Drying

The kombucha powders were produced using a spray dryer (MSD 1.0, Labmac do Brasil, Ribeirão Preto, Brazil) equipped with a 1.2 mm diameter nozzle. The operational parameters were set to an air flow rate of 1.3 m3/min and a pressurized air flow of 30 L/min. Based on preliminary trials to optimize powder yield (Equation (1)), the inlet air temperatures of 140 °C, 160 °C, and 180 °C were evaluated. The volume dried was 700 mL. The maltodextrin concentration and the feed flow rate were also defined through preliminary tests (0.5 and 1.0 L/h). The maltodextrin concentration was set at 20% (w/v), and the selected feed flow rate was 0.5 L/h. Using these conditions, the unflavored (KP), grape-flavored (GKP), and mango-flavored (MKP) kombucha samples were dried.
Y i e l d   % = s o l i d   m a s s   i n   t h e   p o w d e r   s a m p l e s   s o l i d   m a s s   i n   t h e   l i q u i d   k o m b u c h a   ∗ 100

2.5. Physico-Chemical Analysis of Kombucha and Powder Properties

Kombucha fermentation was monitored by measuring pH, total soluble solids, and titratable acidity. The powdered samples were characterized in terms of moisture content, water activity (aw), powder flowability, and retention of total phenolic compounds. All measurements were performed in triplicate unless otherwise specified.

2.5.1. pH, Total Soluble Solids, and Titratable Acidity

The pH was measured using a benchtop pH meter (model mPA 210, MS Tecnopon, Piracicaba, SP, Brazil). Total soluble solids (TSSs) were measured using a refractometer (HI 96801, Hanna Instruments, Woonsocket, RI, USA). Total titratable acidity was determined using 0.1 N NaOH, and the results were expressed as a percentage of acetic acid.

2.5.2. Water Activity and Humidity

Water activity (aw) was measured with a Water Activity Meter at 25 °C (AquaLab Decagon CX-2, Pullman, WA, USA). Moisture content was measured on an infrared balance at 105 °C (ID50, Marconi).

2.5.3. Total Phenolic Compounds (TPC)

Total phenolic compounds (TPC) were determined using the Folin–Ciocalteu method [11], with modifications by [12]. The volume of 10 μL of kombucha was mixed with 200 μL of Folin–Ciocalteu reagent and 100 μL of 20% (w/v) sodium carbonate solution. The mixture was kept in the dark for 3 min at 25 °C, and the absorbance was measured at 700 nm. For the powdered samples, a 1:20 (w/v) dilution was prepared. A gallic acid (GA) calibration curve was used for quantification. Solid samples were previously diluted in water (1 g/100 mL). Total phenolic compounds retention was calculated as a percentage of the liquid kombucha to evaluate the impact of the spray drying process on the kombucha’s phenolic content.

2.5.4. Powder Flowability

The flow properties of the powder were measured using a Powder Flow Tester (PFT) from Brookfield Engineering Laboratories, equipped with the Software Power Flow Pro V1.2 Build 20. The analysis was fully automated and carried out using the Standard Flow Function Test. The normal stress applied to the powder surfaces ranged from 0 to 13.5 kPa. The major consolidation stress and unconfined flow strength, densities, and wall friction angles were used to calculate the Carr ratio index (% CI) [13], Equation (1), and the Hausner ratio (HR) [14], Equation (2), fluidity index (If) [15], Equation (3). The powders were classified according to their flowability as described in Table 1.
C I = ρ t − ρ b ρ b
H R = ρ b ρ t
I f = σ 1 σ C
where CI = Carr index (%); HR = Hausner ratio; ρ b = bulk density (kg/m 3); ρ t = tapped density (kg/m 3); If = flow index; σ 1 = major consolidation stress (kPa); and σ c = unconfined yield strength (kPa).

2.5.5. Scanning Electron Microscopy (SEM)

The morphological characterization of the powder was carried out using a scanning electron microscope (Quanta 450 FEG-FEI Company, Hillsboro, OR, USA) operating at an acceleration voltage of 25 kV, with a nominal resolution of 5 nm and a working distance of 10 nm. The spray-dried samples were placed in a thin layer onto carbon tape attached to a stub, without applying pressure. Excess material was removed, leaving o nly particles firmly adhered to the tape surface. The samples were then sputter-coated with a 20 nm layer of gold. The microscope automatically generated the scale bar.
For particle measurements, 150 particles from different images were chosen for observation. The measurements were performed using Fiji software (Image J 1.54f, Java 1.8.0-322, Bethesda, MD, USA) [16] The size calibration was performed according to the microscope parameters.

2.6. Statistical Analysis

All analyses were measured in triplicate. Tukey’s test was performed to compare the means of the kombucha powder samples. All statistical analyses were performed using STATISTICA software (StatSoft, v. 14.0). Results were expressed as mean ± standard deviation. Statistical significance was set at p < 0.05 for all analyses.

3. Results and Discussion

3.1. Kombucha Physicochemical Parameters

The physicochemical parameters of kombucha, including pH, °Brix, and acidity, play a crucial role in determining the overall quality of the beverage and significantly impact the spray drying process. A balanced pH is essential for the stability and flavor profile of kombucha; typically, a pH range of 2.5 to 3.5 is ideal for maintaining its characteristic pH and preventing spoilage. The °Brix level, which reflects the soluble solids content, including sugars and organic acids, directly impacts the fermentation process and the resulting sweetness, thereby affecting the sensory attributes of the final product. Table 2 presents these parameters at the end of the kombucha fermentation.
The results show that fermentation proceeded as expected, even without the addition of an external carbohydrate (sugar) source. The low pH is associated with the production of organic acids, which helps prevent contamination by inhibiting the growth of microorganisms that cause deterioration. Along with pH, titratable acidity indicates the total amount of acids dissolved in the beverage [17,18,19]. The higher content of TPC in grape and mango flavored kombuchas is attributed to phenolics from the extracts used to flavor the beverage.

3.2. Selection of Drying Temperature

Spray-dried beverages with high organic acid content, like kombucha, depend on critical parameters that influence the final powder’s quality and characteristics. These parameters include the concentration of drying agent (maltodextrin), drying temperature, feed flow rate, and the physicochemical properties of the beverage being dried. Each of these factors plays a significant role in determining the efficiency of the drying process and the quality of the resulting powder. The concentration of solids in the feed solution impacts the viscosity and drying efficiency during the spray drying process, making it a key parameter to consider. High sugar and acid content can lead to stickiness, which is mitigated by using maltodextrin as a drying aid. Additionally, the inlet air temperature also affects the processing; higher temperatures can enhance the drying rate but may also affect the properties of the resulting powder, such as particle size and bulk density. In the present study, we fixed the maltodextrin concentration at 20% (w/v) and changed the feed flow rate and the air inlet temperature. The highest feed flow rate (1.0 L/h) was too high for the kombucha drying process. The fermented kombucha leaked as a viscous liquid at the exit of the drying chamber, and no powder was collected at the equipment exit, even at the highest drying temperature (180 °C). Thus, the feed flow rate was fixed at 0.5 L/h, and the effect of temperature was evaluated. Figure 1 shows the powder yield of traditional kombucha powder (KP) and the retention of total phenolic compounds after spray drying at different inlet temperatures (140 °C, 160 °C, and 180 °C). In Figure 1, the highest powder yield was obtained at 160 °C (34.0 ± 1.7%), followed by 180 °C, and 140 °C, which presented the lowest value (27.4 ± 1.4%). Figure 1 presents the Total Phenolic Content of the kombucha powder. The differences among drying temperatures were statistically significant (p < 0.05).
Increasing the drying temperature from 140 °C to 160 °C resulted in a higher yield, possibly due to greater atomization efficiency and reduced powder adhesion to the walls of the drying chamber. Powder yield is a key variable to produce food powders, supplements, and pharmaceuticals, as it is directly related to production costs and process efficiency [20].
Similar results were reported by [21]. A yield of 36.92% was obtained when drying a cinnamon infusion with maltodextrin at 160 °C. The literature presents various conclusions regarding the effects of temperature, concentration, and type of encapsulating agent, as well as inlet and outlet drying temperatures. Another critical factor in the spray drying of foods is the matrix composition, particularly the presence of reducing sugars, which can affect the atomization characteristics, glass transition temperature (Tg), and thermal stability of the material. Therefore, the success of the spray-drying process depends on balancing operational conditions with the physicochemical properties of the food being processed [8,22,23]. Therefore, aiming for a higher yield, removing sugar from the fermentation process contributed to improving the drying performance. In sugar-containing beverages, powder stickiness and particle agglomeration tend to increase due to the low glass transition temperature (Tg) of sugars [24]. Regarding the bioactive compounds (TPC), the phenolic compounds were slightly better preserved at 140 °C and 160 °C (Figure 1), with retention values of approximately 85%. However, at 180 °C, there was a significant reduction (p < 0.05) in phenolic compound retention, indicating possible thermal degradation. Even so, phenolic retention remained above 80%. Similar results were reported by [25] using 10% (w/v) maltodextrin. Thus, 160 °C represented a balance point between higher yield and good preservation of phenolic compounds, and it was the selected temperature for producing flavored kombucha powders.

3.3. Properties of Kombucha Powders

3.3.1. Water Activity (aw) and Moisture

Figure 2 shows that the moisture content of the kombucha powders dried at 160 °C was 4.2% for KP and GKP, to 4.02% for MKP. Regarding water activity (aw), the MKP sample presented the lowest value (0.283 ± 0.050), while KP and GKP showed identical values (0.317 ± 0.000). Only MKP differed significantly (p < 0.05) from the other samples.
Moisture content is a critical factor in powdered foods because water acts as a plasticizer, reducing the glass transition temperature (Tg). It is well-established that food powders rich in sugars and organic acids, such as kombucha, exhibit low glass transition temperatures due to the presence of these low molecular weight amorphous components [26,27]. The high concentration of organic acids and residual sugars in the kombucha matrix strongly suggests a low Tg value, consistent with literature on similar acidic, sugar-containing food systems [28].
When the storage or processing temperature approaches or exceeds the glass transition temperature, amorphous materials transition from a glassy to a rubbery state, leading to increased molecular mobility and deteriorated powder handling properties [29]. This phenomenon is particularly pronounced in matrices containing fructose, glucose, and organic acids, which are known to depress glass transition temperatures significantly [30]. Lower Tg may cause physical changes during spray drying, such as wall deposition material, particle agglomeration, and lump formation. These phenomena can compromise product quality, favor undesirable chemical reactions, and reduce process yield. Therefore, achieving low moisture content during drying is essential [24]. Additionally, low water activity is crucial for product stability, as it minimizes the occurrence of biochemical reactions and microbial growth. When aw is below 0.3, such reactions are significantly limited, contributing to increased shelf life.
The results obtained in this study are consistent with the recommended values for fruit and vegetable powder products (moisture < 5%), ensuring microbiological safety and stability during long-term storage [31,32].

3.3.2. Morphology of Kombucha Powders

Studying particle morphology and size is essential in the characterization of powdered materials, as these parameters directly affect processing efficiency, final product quality, and consumer acceptability [33]. Characteristics such as flowability, bulk density, angle of repose, and compressibility depend on particle size and distribution, influencing key production steps such as packaging, transportation, mixing, and reconstitution [15]
Figure 3 presents scanning electron microscopy (SEM) images of kombucha powder samples: KP (A and B), GKP (C and D), and MKP (E and F), at two magnifications (100 µm and 20 µm). The images reveal spherical particles (yellow arrows) in all formulations, a typical characteristic of spray-dried powders. No surface cracks or ruptures were observed, indicating a strong physical structure that reduces gas permeability and helps protect bioactive compounds from oxidation and unwanted release [34].
The average particle size of the kombucha powders was 3.40 ± 0.93 µm (KP); 3.18 ± 0.91 µm (GPK), and 3.21 ± 0.87 µm (MPK). Among the samples, the non-flavored kombucha powder (KP), as shown in Figure 3A,B, exhibited a rougher surface appearance (green arrows in Figure 3B), accompanied by agglomerates (red arrow in Figure 3B) formed through the partial coalescence of smaller particles, resulting in a larger unfilled space (indicated by blue arrows). The presence of deformed particles and collapsed surfaces may reflect structural instability during drying. In contrast, the grape-flavored kombucha powder (GKP), Figure 3C,D, presented particles with greater particle size uniformity and smoother surfaces, with less evidence of agglomeration. On the other hand, the mango-flavored kombucha powder (MKP). Figure 3E,F, presented more spherical particles, fewer surface collapses, and a relatively homogeneous size distribution compared to the other samples.
A uniform and smooth surface, with minimal cracks and collapses, is the preferred structure in microencapsulation processes, as it ensures greater resistance to particle collapse and improves powder stability [35]. These morphological characteristics observed in the MKP sample can be attributed to differences in matrix composition [24].
Understanding the physical characteristics of kombucha powders flavored with fruit residues is essential to optimizing their functional performance, ensuring both technological quality and consumer acceptance.

3.3.3. Flowability of Flavored Kombucha Powders

Powder flowability is a complex phenomenon influenced by both intrinsic material properties and environmental factors, such as moisture [36,37]. Among the inherent factors directly affecting powder flow behavior are particle size and shape, surface roughness, material density, electrostatic characteristics, and chemical composition [33].
The flowability and compaction parameters of the kombucha powder formulations showed significant differences between the unflavored sample (KP) and the flavored samples prepared with aqueous extracts of fruit residues (GKP and MKP). Table 3 shows the results of apparent density, tapped density, compressibility index, Hausner ratio, and flowability index (If). Figure 4 and Figure 5 illustrate the unconfined flow resistance (σc) and wall friction angle, respectively.
The KP sample presented the lowest bulk density (275.25 ± 0.57 kg/m3) and tapped density (717.30 ± 0.4 kg/m3), indicating greater free volume between particles, lower cohesion, and higher compressibility. In contrast, GKP and MKP exhibited higher bulk densities (413.35 ± 0.52 and 390.45 ± 0.52 kg/m3, respectively) and tapped densities (930.30 ± 0.51 and 879.80 ± 0.55 kg/m3, respectively), indicating better compaction capabilities. Increasing the total solid content in the feed solution increases bulk density, thereby reducing transportation and packaging costs [38]. Conversely, low bulk density is associated with particle agglomeration and reduced flowability.
These trends were also reflected in the values of the flow index (If), compressibility index (Carr), and Hausner ratio. MKP showed the highest flow index (2.55 ± 0.02), followed by GKP (1.71 ± 0.02) and KP (1.64 ± 0.02), indicating better flow behavior in the presence of structuring compounds derived from mango extract. The Carr index values were higher for KP (45.71 ± 0.42%), followed by GKP (40.55 ± 0.22%) and MKP (38.80 ± 0.12%), confirming greater compressibility in the unflavored sample. The Hausner index followed the same trend, with decreasing values from KP (1.84 ± 0.01) to MKP (1.63 ± 0.01). The minor difference between the apparent and tapped densities in GKP and MKP suggests that the particles are more cohesive and stable [23], also highlighting that good packing, characterized by fewer voids between particles, favors higher bulk density.
The poor flowability observed in kombucha powders agrees with the well-documented behavior of amorphous food powders containing high concentrations of low molecular weight components [39,40]. It is well-established that such materials exhibit glass transition temperatures close to or below ambient conditions, leading to increased interparticle cohesion and deteriorated flow properties [41,42].
In small particles, van der Waals forces are the main contributors to interparticle interactions, directly influencing powder cohesiveness. Acidic food matrices, such as kombucha, are particularly susceptible to flow problems due to the combined effects of low pH on interparticle interactions and the presence of organic acids that contribute to reduced glass transition temperatures [43]. The compositional characteristics of kombucha powders—high organic acid content, residual sugars, and amorphous maltodextrin—create a matrix with predictably low Tg, explaining the observed flowability challenges [44].
The relationship between glass transition temperature and powder handling properties is well-established, with operation near or above Tg resulting in stickiness, caking, and poor flow characteristics [45]. The high concentration of amorphous sugars and organic acids in our kombucha product suggests a low Tg, a factor known to induce caking and reduced flowability in food powder systems [46,47]. This performance is directly related to the physical properties and composition of the particles, as observed in SEM images, which show more regular and less collapsed morphologies in the flavored samples, especially in GKP. This observation reinforces the importance of the relationship between apparent and compacted density in understanding powder behavior during processing and storage. According to Table 1, the kombucha powders are classified in terms of flowability as excessively difficult or difficult. However, this behavior aligns with that of other food powders. This classification is typical for fine food powders containing bioactive compounds and is consistent with similar studies on fruit-derived powders [48,49]. The jamun powder obtained using maltodextrin presented a Carr index (CI) of 28.33% and Hausner ratio HR of 1.40, classified as “Difficult” [50].
On the other hand, the powder produced with whey protein concentrate exhibited a CI of 35.91% and an HR of 1.56, indicating a “Very Difficult” flowability [51]. The moisture values for these powders ranged from 2.57% to 4.95%. The sapodilla pulp powders exhibited a “Very Difficult” fluidity in all formulations studied, with a CI ranging from 53.2% to 59.9% and an HR from 2.14 to 2.50 [20]. These values are considerably worse than those of most kombucha powders, indicating a significantly greater flow difficulty. The moisture of these powders was less than 1.6%.
The kombucha tea powder produced by foam-mat drying showed results for the Carr Index (CI) and Hausner Ratio (HR) ranging from “Acceptable to Difficulty” (CI 20.42%, HR 1.26) with Gum Arabic to “Difficulty” (CI 28.00%, HR 1.39) with Inulin-Gum Arabic. These ratings indicate a fluidity from reasonable to complex, depending on the formulation. The moisture of these powders ranged from 0.85% to 3.26% [52].
Complementing the analysis of the powder properties, the unconfined flow strength (σc) was evaluated to characterize the internal cohesion of the powders after consolidation. Figure 4 shows the σc values for the different samples. Although the MKP sample demonstrated better flowability, all samples exhibited high compaction potential, as indicated by progressive increases in flow strength with consolidation. This characteristic is related to the way the particles are organized, with more efficient packing resulting in a smaller volume of voids between them, thus requiring less force for compression. The observed morphology and the presence of natural compounds, such as polyphenols and fibers, contribute to greater cohesion [22,53].
Figure 5 illustrates the wall friction angle values, which reinforce the previously observed characteristics. The KP sample exhibited the highest wall friction angle under applied stresses, as GKP showed the lowest angle under higher stress conditions, with no significant difference between the flavored samples. Higher values indicate greater friction against equipment surfaces, impairing flowability, which is consistent with the behavior observed in the other flow parameters [22,54]. Overall, the results demonstrate that the addition of extracts from fruit residues directly affects the mechanical properties of kombucha powders. The improved flowability characteristics observed in flavored samples can be attributed to the presence of natural compounds that modify particle surface properties and interparticle interactions. These characteristics are essential for industrial processing applications, including powder handling, transportation, and storage operations [41].

3.4. Retention of Total Phenolic Compounds (TPCs)

Figure 6 shows the retention of total phenolic compounds (TPCs) in the different kombucha powder samples. The GKP sample (grape-flavored kombucha) presented the highest value, significantly higher (p < 0.05) than the MKP (mango-flavored kombucha) and KP (unflavored kombucha) samples. The results showed that the addition of plant extracts positively contributed to the preservation and/or retention of phenolic compounds during the spray-drying process.
The higher phenolic retention in the flavored samples can be attributed to the chemical composition of the matrix, as grape extract is known for its high content of polyphenols, including flavonoids and tannin compounds, which are widely studied for their antioxidant activity [55]. MKP also showed an increase in phenolic retention compared to unflavored kombucha. However, the values were lower than those of GKP, which can be explained by the differences in the phenolic profile between the two fruits. Thus, in addition to the quantity of compounds, the type of phenolic present can influence retention during drying, as simpler structures may be more susceptible to thermal degradation [56,57].
The enhanced retention of phenolic compounds in flavored samples may also be related to the protective matrix effect provided by the fruit extract components, which can act as natural antioxidants during the drying process [58]. Additionally, the interaction between phenolic compounds and maltodextrin through hydrogen bonding may contribute to improved stability and retention during spray drying [59].
The significant retention observed in the flavored samples, especially in GKP, confirms that the spray drying process is effective in preserving bioactive compounds even in complex food systems such as kombucha. These results reinforce the technological feasibility of producing powdered kombucha.

Comparison with Liquid Kombucha

To evaluate the bioactive preservation during the powder production process, the total phenolic content of the powdered samples was compared with that of liquid kombucha (Table 2). The spray drying process yielded retention rates of 82–93% (Figure 6) for total phenolic compounds, which is consistent with other studies on the preservation of bioactive compounds during spray drying [41]. This high retention rate suggests that the powdered kombucha maintains significant functional properties compared to the original liquid product, making it a viable alternative for consumers seeking the health benefits of kombucha in a more stable and convenient form [60].
Comparing the TPC retention and the SEM images (Figure 3), the powder with the most ideal structure, the grape-flavored kombucha (GKP), exhibited the highest retention of total phenolic compounds (TPC) at 93.33% (Figure 6). This can be attributed to its uniform, smooth-surfaced spherical particles (Figure 3C,D). On the other hand, the sample with the lowest TPC retention (82.46%) was the unflavored powder (KP), which exhibited the most surface defects and particle agglomeration (Figure 3A,B). This behavior is explained by the principle of microencapsulation, where a well-formed particle acts as a more effective protective barrier. The smooth, intact surface of the GKP particles can better preserve the sensitive phenolic compounds from thermal degradation and oxidation during the spray-drying process. At the same time, the structural defects in the KP powder compromised this barrier, leading to higher phenolic losses. Therefore, the addition of fruit extracts appears to enhance the structural integrity of the microcapsules, thereby improving their ability to preserve the bioactive compounds.

4. Conclusions

The present study demonstrated that the production of kombucha powder by spray drying, using fruit residues as flavoring extracts, directly influences the physicochemical, mechanical, and functional properties of the final product. The addition of grape and mango extracts to the kombucha contributed to an increase in total phenolic compound content.
The characteristics observed in the flavored kombucha powders in this study reveal promising technological potential for various food applications. The improved flowability, enhanced phenolic retention, and stable particle morphology make these powders suitable for incorporation into functional food formulations, dietary supplements, and beverage mixes. The sustainable use of fruit processing by-products as flavoring agents aligns with circular economy principles while adding functional value to the final product.
To improve powder flowability for industrial applications, post-processing techniques such as granulation can be employed. Granulation agglomerates fine particles into larger, more porous structures, improving fluidity by reducing interparticle forces and optimizing wetting properties while decreasing hygroscopicity and caking tendencies. Additionally, the incorporation of anti-caking agents such as silicon dioxide or calcium stearate can minimize cohesion and improve flow properties. Strict moisture control during processing and storage remains essential, as slight variations in water content can significantly affect the flow capacity of the powder.

Author Contributions

M.d.F.D.L.: Data curation, Investigation, Methodology, Writing—original draft, Writing—review and editing. T.V.F.: Methodology, Investigation, Writing—original draft. L.S.d.O. and S.B.d.S.: Investigation, Methodology, E.d.C.M.: Data curation, Investigation, Methodology, S.R. and F.A.N.F.: Conceptualization, Investigation, Methodology, Project administration, Resources, Writing—review and editing. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES)—Finance Code 001. The authors thank CNPq and the National Institute of Tropical Fruits (INCT-FT/CNPq) for financial funds and scholarships.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Acknowledgments

The authors thank Central Analytica—UFC for the SEM analysis.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
KPTraditional kombucha powder
GPKGrape-flavored kombucha powder
MKPMango-flavored kombucha

References

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Processes 13 03020 g001
Figure 1. Powder yield of traditional kombucha powder (KP), and retention of total phenolic compounds after spray drying at different inlet temperatures (140 °C, 160 °C, and 180 °C). Different lowercase letters indicate significant differences for Yield, and different uppercase letters indicate significant differences for TPC (p < 0.05).
Figure 1. Powder yield of traditional kombucha powder (KP), and retention of total phenolic compounds after spray drying at different inlet temperatures (140 °C, 160 °C, and 180 °C). Different lowercase letters indicate significant differences for Yield, and different uppercase letters indicate significant differences for TPC (p < 0.05).
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Figure 2. Moisture and water activity (aw) of traditional kombucha (KP), grape kombucha powder (GKP), and mango kombucha powder (MKP) powders obtained by spray drying. Different letters indicate significant differences according to the Tukey test (p < 0.05).
Figure 2. Moisture and water activity (aw) of traditional kombucha (KP), grape kombucha powder (GKP), and mango kombucha powder (MKP) powders obtained by spray drying. Different letters indicate significant differences according to the Tukey test (p < 0.05).
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Figure 3. Scanning electron microscopy of dried kombucha. (A,B)—non-flavored kombucha (KP); (C,D)—grape kombucha (GKP); (E,F)—mango kombucha (MKP), showing spherical particles (yellow arrows), unfilled space (blue arrows), rough surfaces (green arrows), and agglomerates (red arrows). The particles are spherical and approximately the same size in all kombucha powders.
Figure 3. Scanning electron microscopy of dried kombucha. (A,B)—non-flavored kombucha (KP); (C,D)—grape kombucha (GKP); (E,F)—mango kombucha (MKP), showing spherical particles (yellow arrows), unfilled space (blue arrows), rough surfaces (green arrows), and agglomerates (red arrows). The particles are spherical and approximately the same size in all kombucha powders.
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Figure 4. Unconfined flow limit of unflavored kombucha (KP) and flavored with grape and mango residue (GKP and MKP) powders. The results were expressed as mean values with standard deviation.
Figure 4. Unconfined flow limit of unflavored kombucha (KP) and flavored with grape and mango residue (GKP and MKP) powders. The results were expressed as mean values with standard deviation.
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Figure 5. Wall friction angles of flavored kombucha powders. Tukey’s test was performed to compare sample means. Different letters indicate statistically significant differences (p < 0.05).
Figure 5. Wall friction angles of flavored kombucha powders. Tukey’s test was performed to compare sample means. Different letters indicate statistically significant differences (p < 0.05).
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Figure 6. Retention of total phenolic compounds in kombucha powders. Tukey’s test was performed to compare sample means. Different letters indicate statistically significant differences (p < 0.05).
Figure 6. Retention of total phenolic compounds in kombucha powders. Tukey’s test was performed to compare sample means. Different letters indicate statistically significant differences (p < 0.05).
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Table 1. Classification of powder fluidity according to Compressibility index (%) and Hausner ratio [13].
Table 1. Classification of powder fluidity according to Compressibility index (%) and Hausner ratio [13].
FlowabilityCarr Index (%)Hausner Ratio
Excellent<101.00–1.11
Good11–151.12–1.18
Adequate16–201.19–1.25
Acceptable21–251.26–1.34
Difficult26–311.35–1.45
Very difficult32–371.46–1.59
Excessively difficult>38>1.60
Table 2. Physicochemical parameters (total soluble solids, pH, titratable acidity, and TPC) at the end of kombucha fermentation. Data are presented as mean ± standard deviation.
Table 2. Physicochemical parameters (total soluble solids, pH, titratable acidity, and TPC) at the end of kombucha fermentation. Data are presented as mean ± standard deviation.
KombuchaGrape KombuchaMango Kombucha
pH3.70 ± 0.05 a3.50 ± 0.05 b3.30 ± 0.05 c
°Brix0.20 ± 0.05 a0.20 ± 0.01 a0.30 ± 0.01 a
Acidity (%)0.22 ± 0.01 a0.23 ± 0.05 a0.23 ± 0.05 a
TPC143.94 ± 2.62 a227.34 ± 2.11 b165.77 ± 2.14 c
Different letters in the same line mean a significant difference (p < 0.05).
Table 3. Bulk density, tapped density, compressibility index, Hausner ratio, and flow index (If) of traditional kombucha powder, grape-flavored kombucha powder, and mango-flavored kombucha powder.
Table 3. Bulk density, tapped density, compressibility index, Hausner ratio, and flow index (If) of traditional kombucha powder, grape-flavored kombucha powder, and mango-flavored kombucha powder.
KPGKPMKP
Bulk density (kg/m3)275.25 ± 0.57 c413.35 ± 0.52 a390.45 ± 0.52 b
Tapped density (kg/m3)717.30 ± 0.4 c930.30 ± 0.51 a879.80 ± 0.55 b
Carr’s index (%)45.71 ± 0.42 a40.55 ± 0.22 b38.80 ± 0.12 c
Hausner ratio1.84 ± 0.01 a1.68 ± 0.01 b1.63 ± 0.01 b
Flow index (If)1.64 ± 0.02 b1.71 ± 0.02 b2.55 ± 0.05 a
Different letters indicate statistically significant differences (p < 0.05) in the same line.
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MDPI and ACS Style

Linhares, M.d.F.D.; Fonteles, T.V.; de Oliveira, L.S.; de Souza, S.B.; de Castro Miguel, E.; Fernandes, F.A.N.; Rodrigues, S. Powdered Kombucha Flavored with Fruit By-Products: A Sustainable Functional Innovation. Processes 2025, 13, 3020. https://doi.org/10.3390/pr13093020

AMA Style

Linhares MdFD, Fonteles TV, de Oliveira LS, de Souza SB, de Castro Miguel E, Fernandes FAN, Rodrigues S. Powdered Kombucha Flavored with Fruit By-Products: A Sustainable Functional Innovation. Processes. 2025; 13(9):3020. https://doi.org/10.3390/pr13093020

Chicago/Turabian Style

Linhares, Maria de Fátima Dantas, Thatyane Vidal Fonteles, Lorena Silva de Oliveira, Samira Barros de Souza, Emilio de Castro Miguel, Fabiano André Narciso Fernandes, and Sueli Rodrigues. 2025. "Powdered Kombucha Flavored with Fruit By-Products: A Sustainable Functional Innovation" Processes 13, no. 9: 3020. https://doi.org/10.3390/pr13093020

APA Style

Linhares, M. d. F. D., Fonteles, T. V., de Oliveira, L. S., de Souza, S. B., de Castro Miguel, E., Fernandes, F. A. N., & Rodrigues, S. (2025). Powdered Kombucha Flavored with Fruit By-Products: A Sustainable Functional Innovation. Processes, 13(9), 3020. https://doi.org/10.3390/pr13093020

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