ارزیابی تغییرات ویژگی‌های کیفی پودر عسل در فرآیند خشک کردن پاششی

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 highly hygroscopic and sticky material, making its storage, handling, and industrial application difficult. Spray drying is an effective technique for converting liquid honey into powder, improving shelf life, flowability, and product stability. However, the high sugar content and low glass transition temperature of honey often cause stickiness and wall deposition during drying. Maltodextrin is commonly used as a carrier to overcome these limitations. Although previous studies have mainly focused on inlet air temperature and carrier concentration, the influence of atomizer pressure has received limited attention. Therefore, this study investigated the combined effects of inlet temperature, maltodextrin concentration, and atomizer pressure on the physicochemical properties of spray-dried honey powder.
Materials and Methods
Honey (Azar Kando, Iran) was mixed with maltodextrin at 15, 32.5, and 50% (w/w) and dried using a laboratory-scale spray dryer. Process optimization was performed using a Box–Behnken response surface design with three independent variables: inlet air temperature (120–180 °C), atomizer pressure (0.5–1.5 bar), and maltodextrin concentration (15–50%). Seventeen experimental runs were conducted. The responses included moisture content, water activity, bulk density, flowability, pH, sucrose, fructose/glucose (F/G) ratio, hydroxymethylfurfural (HMF), and color parameters (L*, a*, and b*).
Results and Discussion
Response surface models adequately described all responses, with inlet air temperature identified as the most influential processing factor. Increasing temperature and maltodextrin concentration significantly reduced moisture content and water activity, while higher atomizer pressure further enhanced drying by producing finer droplets. The lowest moisture (<2%) and water activity (<0.30) were achieved at high temperature, high carrier concentration, and high pressure. Bulk density and flowability improved with increasing temperature and maltodextrin concentration. Higher atomizer pressure also enhanced powder flowability through the formation of smaller and more uniform particles. A slight increase in pH was observed with increasing temperature and maltodextrin concentration. Sucrose content increased under higher temperature and carrier levels, indicating better sugar retention during drying. In contrast, the fructose/glucose ratio decreased with increasing temperature and pressure because fructose is more susceptible to thermal degradation, whereas higher maltodextrin concentrations protected fructose and helped preserve this ratio. HMF formation increased markedly at temperatures above 150 °C due to enhanced sugar degradation and non-enzymatic browning. Nevertheless, increasing maltodextrin concentration and atomizer pressure partially reduced HMF formation by shortening drying time and protecting sugars from excessive thermal damage. Color was also affected by processing conditions. Increasing temperature reduced lightness (L*) and increased redness (a*), reflecting stronger browning reactions. Maltodextrin improved lightness by protecting color compounds, while atomizer pressure showed only a minor influence on color compared with temperature. Unlike most previous studies, this work demonstrated that atomizer pressure is an important process variable. Although its effect was generally smaller than that of temperature, optimizing atomizer pressure significantly improved moisture removal, water activity, flowability, and HMF control, thereby enhancing overall powder quality.
Conclusion
The physicochemical quality of spray-dried honey powder was mainly governed by inlet air temperature, followed by maltodextrin concentration and atomizer pressure. High temperature improved drying efficiency and powder flowability but promoted HMF formation and darkening. Maltodextrin protected sugars, improved powder stability, and enhanced lightness. Most importantly, this study confirmed that atomizer pressure, a parameter rarely investigated in previous honey spray-drying studies, plays a significant role in improving drying performance and final product quality. Multi-response optimization indicated that inlet temperatures of 170–180 °C, 45–50% maltodextrin, and 1.0–1.5 bar atomizer pressure provided the best balance between low moisture, low water activity, high flowability, acceptable HMF levels, and desirable color characteristics. These findings provide practical guidance for industrial production of high-quality honey powder and emphasize the importance of incorporating atomizer pressure into future spray-drying optimization studies.