Regulation of Sugar Content and Glass Transition in Jujube Slices via CP-Assisted Pulsed Vacuum Drying: Effects on Physicochemical Properties and Blood Glucose Regulation

Abstract

Although red dates (Ziziphus jujuba Mill.) are rich in nutrients and have both edible and medicinal properties, during the drying process, due to their high sugar content, they often result in a lower glass transition temperature (Tg), enhanced hygroscopicity, surface agglomeration, and a decline in storage quality, severely limiting the shelf stability of the products and the improvement of the processing quality. Cold plasma (CP) can form cavities through surface etching, promoting water migration, thereby increasing the drying rate and diffusion coefficient. Vacuum pulsation drying (PVD) has a higher drying rate, stronger mass transfer ability, and better quality retention effect compared to ordinary drying methods. Based on these characteristics, we believe that CP and PVD have a synergistic enhancing effect in the drying of date slices. Therefore, in this study, CK-PVD (without plasma pre-treatment, direct vacuum pulsation drying) was used as the control group, and CP-PVD (after plasma pre-treatment, vacuum pulsation drying), A1, A2, and A3 (after plasma treatment, soaking in different concentrations of ethanol and then vacuum pulsation drying) were used as experimental groups to study the effects of CP pre-treatment combined with ethanol extraction on the sugar composition, glass transition temperature (Tg), physical stability, and reduce blood sugar activity of dried date slices. The results showed that CP pre-treatment significantly improved the material transfer efficiency (confirmed by the increases in the areas of T22 and T23 peaks). Compared with the control group, the low-sugar group (A2) exhibited reduced total sugar content, the gel point increased to 35.6 °C, and the microscopic structure changed from regular and smooth to dense and irregular, thereby significantly enhancing the water retention stability. To further evaluate the biological activity of low-sugar red date tablets, an in vivo hypoglycemic experiment was conducted using the zebrafish model. And the zebrafish experiment further confirmed that 0.05 mg/mL of low-sugar date slices could reduce blood sugar by 11.66%, showing lower blood sugar activity. The optimized low-sugar processing conditions (70% ethanol, 50 °C, solid–liquid ratio 1:15, 2.5 h) provided scientific basis and technical support for the development of dry date products with excellent physical stability and health benefits and offered valuable references for the high-value-added processing and functional utilization of high-sugar fruit resources.