Water–solid interactions in amorphous maltodextrin-crystalline sucrose binary mixtures

Abstract

Amorphous and crystalline solids are commonly found together in a variety of pharmaceutical and food products. In this study, the influence of co-formulation of amorphous maltodextrins (MDs) and crystalline sucrose (S) on moisture sorption, deliquescence, and glass transition (Tg) properties of powder blends was investigated. Individual components and binary mixtures of four different molecular weight MDs with sucrose in 1:1 w/w ratios were exposed to various relative humidity (RH) environments and their equilibrium and dynamic moisture contents were monitored. The deliquescence point (RH0) and dissolution behavior of sucrose alone and in blends was also monitored by polarized light microscopy and second harmonic generation imaging. In S:MD blends, the deliquescence RH of sucrose was lower than the RH0 of sucrose alone, and synergistic moisture sorption also occurred at RHs lower than the RH0. Intimate contact of sucrose crystals with the amorphous MDs resulted in complete dissolution of sucrose at RH < RH0. When blends were stored at conditions exceeding the Tg of the individual MDs (25 °C and 60%, 49% and 34%RH for MD21, MD29 and MD40, respectively), the Tg of the blends was lower than that of individual MDs. Thus, co-formulation of amorphous MDs with crystalline sucrose sensitizes the blend to moisture, potentially leading to deleterious changes in the formulation if storage conditions are not adequately controlled.

Moisture‐Mediated Interactions Between Amorphous Maltodextrins and Crystalline Fructose

“…To facilitate moisture sorption data collection at smaller RH intervals, an automated multisample moisture sorption analyzer SPS‐x (Projekt Messtechnik, Ulm, Germany) with a 23 sample‐handling tray was also used to generate equilibrium moisture sorption isotherms of the MDs, F, and F:MD mixtures at 25 °C as described elsewhere (Ghorab and others , b). Samples were pre‐equilibrated in desiccators over Drierite TM for 2 wk (22 °C), and then the initial moisture contents of the samples were determined as described previously.…”

“…Physical instability at lower RHs than expected based on individual ingredient behavior has been reported for blends of deliquescent and amorphous ingredients. For instance, co‐formulating crystalline sucrose or sodium chloride with amorphous maltodextrins (MDs) decreased the RH 0 of the crystal (Ghorab and others , b). When dry blended with amorphous green tea powder, dissolution of citric acid and ascorbic acid crystals occurred at RHs below their RH 0 s (Ortiz and others ; Hiatt and others ).…”

“…Synergistic moisture uptake by binary blends of sucrose:MD and NaCl:MD also occurred at RHs below RH 0 (moisture sorption by the blends was higher than an additive model based on individual ingredients), and when these samples were equilibrated at the same RH and temperature conditions, the T g s of the blends were often lower than the T g s of the MDs alone. The lower T g s could be accounted for by the higher water uptake in the blends (Ghorab and others , b). …”

“…Fructose, a reducing sugar, is such an ingredient, with a low RH 0, reported as 61% RH to 63% RH at 22 °C, a high solubility, and a conversion into 4 tautomeric forms in aqueous solution (Mauer and Taylor ; Barclay and others ). Because of the widespread use and presence of fructose in the food industry, as well as the potential to better understand the relationship between RH 0 , T g , and moisture sorption in complex blends, it was of interest to investigate the moisture‐mediated interactions between crystalline fructose and amorphous maltodextrins and compare the results for fructose to those observed for other deliquescent crystals in similar blends (Ghorab and others , b). …”

Encapsulation of orange terpenes investigating a plasticisation extrusion process

“…Since decades, maltodextrins, simple sugars, and modified food starches have been used as carbohydrate matrix material (Risch, 1988). The combination of a high molecular weight carbohydrate such as maltodextrin or starch with a low molecular weight carbohydrate such as sucrose, lactose or maltose is often reported to work well in flavour encapsulation (Blake and Attwool, 1996;Gunning et al, 1999;Uhlemann and Reiss, 2010;Zuidam and Shimoni, 2010;Ghorab et al, 2014). Physical characteristics of importance of a maltodextrin/sucrose mix at different ratios and their effect in batch mixing and hot melt extrusion are reported in (Tackenberg et al, 2014b(Tackenberg et al, , 2015.…”