Evaluation of Quality Changes in Honey Powder During the Spray Drying Process

The high viscosity and inherent stickiness of honey pose substantial challenges for handling, transport, packaging, and its incorporation as a food ingredient. Converting honey into a powder can mitigate many of these constraints and broaden its practical applications. This study aimed to produce honey powder via spray drying and to characterize the physicochemical quality of the resulting product. Spray drying was conducted at three inlet air temperatures (120, 150, and 180 °C), three atomization pressures (0.5, 1.0, and 1.5 bar), and three maltodextrin carrier levels (15, 32.5, and 50% w/w, based on honey dry matter). Process conditions were optimized using response surface methodology, with particular emphasis on atomization pressure as a key operating variable. The powder was evaluated for moisture content, water activity, bulk density, flowability, color parameters, pH, sucrose content, fructose-to-glucose ratio, and hydroxymethylfurfural (HMF) concentration. Analysis of variance indicated that inlet air temperature and maltodextrin concentration significantly affected (p < 0.05) most quality attributes. Temperature influenced 9 of the 11 measured responses and was the dominant factor overall, with pronounced effects on moisture, water activity, bulk density, flowability, HMF formation, and color indices. Maltodextrin concentration significantly affected water activity, pH, sucrose content, fructose-to-glucose ratio, and yellowness. Atomization pressure also contributed significantly to several critical responses, including moisture content, bulk density, water activity, yellowness, and HMF concentration. Multi-response optimization identified optimal conditions at an inlet air temperature of 170–180 °C, atomization pressure of 1.0–1.5 bar, and maltodextrin concentration of 45–50%. Under these settings, the process yielded honey powder with moisture content below 2%, water activity below 0.30, high flowability, desirable lightness, and low HMF levels.
Introduction:
Honey is a high-viscosity, hygroscopic natural sweetener, and its inherent stickiness complicates pumping, storage, transportation, and incorporation into food formulations. Converting honey into a powdered form offers clear functional benefits, including improved flowability, reduced tackiness, extended shelf life, easier handling, and broader applicability in dry food systems. Among available technologies, spray drying is considered particularly suitable for producing honey powder because it enables rapid moisture removal through efficient heat and mass transfer while helping to preserve product quality.
Despite these advantages, spray-drying honey remains technically challenging. Honey’s high sugar content, low glass transition temperature, and pronounced hygroscopicity promote stickiness, wall deposition, and agglomeration during drying, which can reduce powder yield and compromise quality. To mitigate these issues, carrier materials—most commonly maltodextrin are routinely added to increase the glass transition temperature, reduce stickiness, and improve powder stability.
While prior studies have largely focused on the influence of inlet air temperature and carrier concentration, the effect of atomizer pressure has received comparatively limited attention. Atomizer pressure is a critical operational variable because it governs droplet size distribution, drying kinetics, and particle morphology, which in turn affect key quality attributes of the resulting powder. Accordingly, the present study addresses this gap by examining the combined effects of inlet temperature, maltodextrin concentration, and atomizer pressure on the physicochemical properties of spray-dried honey powder.
Materials and Methods:
Pure honey (Azar Kando; Golshad Co., Iran) was blended with maltodextrin at three carrier levels (15, 32.5, and 50% w/w, based on honey dry matter). Spray drying was performed using a laboratory-scale spray dryer (Dorsa Behsaz, Iran) fitted with a cylindrical cyclone chamber (65 × 43 × 110 cm).
Process optimization was conducted using a Box–Behnken response surface methodology (RSM) design with three independent variables: inlet air temperature (120, 150, and 180 °C), atomizer pressure (0.5, 1.0, and 1.5 bar), and maltodextrin concentration (15, 32.5, and 50%). In total, 17 experimental runs were carried out according to the experimental design. The resulting powders were collected and stored at 4 ± 1 °C until further analyses.
Response variables included moisture content, water activity, bulk density, flowability (Carr Index and Hausner Ratio), pH, sucrose content, fructose-to-glucose (F/G) ratio, hydroxymethylfurfural (HMF) concentration, and color attributes (L*, a*, and b*). All measurements were performed in accordance with AOAC procedures and relevant Iranian national standards.

The statistical analysis confirmed the adequacy of the fitted RSM models, as indicated by high coefficients of determination and non-significant lack-of-fit values. Among the investigated variables, inlet air temperature was identified as the most influential factor, significantly affecting 9 out of the 11 measured quality attributes. Maltodextrin concentration also exerted a significant impact on several key parameters, while atomizer pressure, although less dominant overall, played a statistically meaningful role in determining critical quality characteristics.

Moisture content and water activity decreased significantly with increasing inlet air temperature and maltodextrin concentration. Higher temperatures enhanced the driving force for moisture evaporation, while increased carrier content facilitated the formation of a protective matrix that reduced hygroscopicity. The lowest moisture content (below 2%) and water activity (below 0.30) were achieved at an inlet temperature of 180 °C, maltodextrin concentration of 50%, and atomizer pressure of 1.5 bar. Increasing atomizer pressure further contributed to reduced moisture levels, likely due to the formation of finer droplets with larger surface areas, leading to more efficient drying.

Bulk density increased with increasing inlet temperature and maltodextrin concentration, which can be attributed to the formation of more compact and less porous particles. Under these same conditions, powder flowability improved significantly, as reflected by lower Carr Index and Hausner Ratio values. Higher atomizer pressure also enhanced flowability, probably by producing smaller and more uniform particles with reduced interparticle cohesion. The best flowability characteristics were observed at high temperature (180 °C), high maltodextrin content (50%), and an atomizer pressure of 1.5 bar.

The pH of honey powder showed a slight increase with increasing inlet air temperature and maltodextrin concentration. This behavior may be explained by dilution of organic acids due to carrier addition and possible buffering effects of maltodextrin. Sucrose content increased at higher temperatures and carrier levels, suggesting improved sugar retention and reduced degradation under optimized drying conditions.

The fructose-to-glucose (F/G) ratio decreased with increasing inlet air temperature and atomizer pressure, indicating a higher susceptibility of fructose to thermal degradation. In contrast, higher maltodextrin concentrations helped preserve fructose, resulting in higher F/G ratios. Maintaining an adequate F/G ratio is important for minimizing crystallization and caking during storage, and the most favorable preservation of this ratio was achieved at lower temperatures and pressures combined with higher carrier content.

Hydroxymethylfurfural (HMF), a key indicator of thermal degradation and non-enzymatic browning in honey, increased significantly at inlet air temperatures above 150 °C. However, both maltodextrin addition and increased atomizer pressure were effective in mitigating HMF formation. Maltodextrin likely acted as a protective matrix, reducing the exposure of sugars to high temperatures, while higher atomizer pressure shortened residence time by accelerating moisture removal. Acceptable HMF levels (below the regulatory threshold of 40 ppm) were maintained at inlet temperatures of 150 °C or lower when combined with high maltodextrin content and atomizer pressures of at least 1 bar.

Color analysis revealed that increasing inlet air temperature led to a decrease in lightness (L*) and an increase in redness (a*), reflecting intensified browning reactions. Conversely, maltodextrin significantly improved lightness, demonstrating its protective effect on color preservation. Atomizer pressure exerted a moderate influence on color attributes, possibly due to changes in particle structure and light-scattering behavior. The brightest powders with minimal browning were obtained at lower temperatures, lower atomizer pressure, and higher carrier concentration.

One of the most notable findings of this study was the demonstrated importance of atomizer pressure as a key processing variable. While previous studies have primarily focused on inlet air temperature and carrier concentration, the present results highlight that atomizer pressure plays a crucial role in governing droplet size distribution, drying efficiency, particle morphology, and ultimately, powder quality. Increasing atomizer pressure from 0.5 to 1.5 bar improved powder homogeneity, reduced moisture content and water activity, enhanced flowability, and contributed to lower HMF formation.

Multi-response optimization using the desirability function approach identified the optimal spray-drying conditions as an inlet air temperature of 170–180 °C, maltodextrin concentration of 45–50%, and atomizer pressure of 1.0–1.5 bar. Under these conditions, the produced honey powder exhibited moisture content below 2%, water activity below 0.30, excellent flowability, desirable lightness, and low HMF levels, satisfying key quality requirements for honey powder intended for food applications.

This study shows that inlet air temperature, maltodextrin concentration, and atomizer pressure collectively govern the physicochemical and functional quality of spray-dried honey powder. Inlet temperature was the most influential parameter across the measured responses; however, atomizer pressure—an operating variable that has received limited attention in prior work—was also critical for regulating moisture content, water activity, flowability, and hydroxymethylfurfural (HMF) formation.
Multi-response optimization identified the following conditions as optimal for producing high-quality honey powder: an inlet air temperature of 170–180 °C, maltodextrin concentration of 45–50%, and atomizer pressure of 1.0–1.5 bar. Under these settings, the resulting powder achieved moisture levels below 2%, water activity below 0.30, excellent flowability, high lightness, and acceptable HMF concentrations, meeting the relevant quality requirements for honey powder.
Overall, the results underscore the need to explicitly incorporate atomizer pressure into future spray-drying optimization frameworks for honey and similarly heat-sensitive, sticky, and sugar-rich materials.