Effects of Vacuum Dehydration on the Physicochemical Properties of Itama Stingless Bee Honey

Abstract

Background and Objective: At present, stingless bee honey has gained considerable attention as a product with high nutritional value and bioactive properties. However, its high moisture content remains a major limitation, affecting product quality and promoting fermentation. Therefore, moisture reduction is an essential process for extending shelf life and maintaining the quality of stingless bee honey. Conventional heat-based dehydration methods may adversely affect the physical and chemical properties as well as important bioactive compounds. In contrast, vacuum dehydration, which operates at low temperatures, has greater potential to preserve the quality and functional components of stingless bee honey. This study aimed to investigate the effects of vacuum dehydration at different processing times on the physical and chemical properties of stingless bee honey.

Methodology: This study used fresh stingless bee honey from the Itama species (Heterotrigona itama), collected from the Ban Phraiwan Stingless Bee Community Enterprise, Tak Bai District, Narathiwat Province, Thailand, in February 2025. The samples were stored at 4 °C prior to analysis. Before the experiment, the honey was filtered through sterilized muslin cloth and divided into five experimental groups. Moisture reduction was then performed using a vacuum system at a pressure of - 0.8 bar and a temperature of 30 ± 1 °C for 0, 1, 2, 3, and 4 h, respectively. The physical properties of the samples were evaluated, including viscosity using a Brookfield Viscometer and color values in the CIE Lab* system using a Chroma Meter. The chemical properties were determined by measuring moisture content using the AOAC (2000) method, total soluble solids using a refractometer, and pH using a digital pen-type pH meter. In addition, antioxidant properties were evaluated by determining total phenolic content using the Folin–Ciocalteu method, free radical scavenging activity using the DPPH assay, and total flavonoid content using the aluminum chloride colorimetric method. Sugar content was also analyzed by determining reducing sugars using the DNS method, total sugars using the anthrone method, and individual sugars, including fructose, glucose, and maltose, using HPLC. All data were expressed as mean ± standard deviation and statistically analyzed using one-way analysis of variance (One-way ANOVA) based on a Completely Randomized Design (CRD). Differences among means were determined using Duncan’s Multiple Range Test at a significance level of 0.05, in order to draw conclusions and identify the optimal conditions for the moisture reduction process of stingless bee honey.

Results: The study on the effects of vacuum moisture reduction time on fresh Itama stingless bee honey demonstrated that processing time significantly affected the physical, chemical, and bioactive properties of  the honey (p < 0.05). In particular, viscosity increased from 372 ± 2.00 cP at 0 h to 529.46 ± 14.49 and 532.90 ± 45.81 cP at 3 and 4 h, respectively, indicating increased concentration and thickness of the honey as moisture content decreased. Regarding color properties, the L* value decreased from 69.05 ± 3.24 to 58.33 ± 1.93, while the b* value decreased from 34.29 ± 0.59 to 22.63 ± 0.99, indicating that the honey became darker and less yellow with increasing moisture reduction time. In addition, the a* value increased from -3.02 ± 0.23 to -0.56 ± 0.26, reflecting changes in pigment composition within the honey color system. For chemical properties, moisture content decreased from 12.38 ± 0.23% to 11.29 ± 0.23%, whereas total soluble solids increased from 68.73 ± 0.25 to 70.77 ± 1.40 °Brix. The pH value decreased from 3.13 ± 0.06 to 2.80 ± 0.02, indicating increased acidity during processing. In terms of antioxidant properties, total phenolic content increased from 484.60 ± 0.10 to    505.90 ± 0.14 mg GAE/100 g, total flavonoid content increased from 17.84 ± 0.04 to 18.05 ± 0.03 mg QE/100 g, and antioxidant activity increased from 90.15 ± 0.01% to 91.16 ± 0.14% with increasing processing time. The sugar composition showed that reducing sugars slightly decreased from 30.79 ± 0.01% to 30.51 ± 0.03%, whereas total sugars increased from 55.30 ± 0.03% to 56.58 ± 0.01%. Fructose increased from 9.73 ± 0.01% to 11.41 ± 0.04%, and glucose increased from 12.98 ± 0.01% to 14.30 ± 0.01%, while maltose decreased from 32.78 ± 0.01% to approximately 30.20–30.48%. These results reflect changes in carbohydrate composition associated with moisture reduction in stingless bee honey.

Conclusions: Vacuum-based moisture reduction effectively reduced the moisture content of stingless bee honey after 4 h at a pressure of - 0.8 bar. In addition, this method was able to preserve antioxidant compounds and phenolic substances, which are important factors contributing to product quality. Furthermore, it helped reduce fermentation and extend the shelf life of stingless bee honey products.