Rehydration of food powders: Interplay between physical properties and process conditions

Effect of maltodextrin on the oxidative stability of ultrasonically induced soybean oil bodies microcapsules

Introduction

Encapsulation of soybean oil bodies (OBs) using maltodextrin (MD) can improve their stability in different environmental stresses and enhance the transport and storage performance of OBs.

Methods

In this study, the effects of different MD addition ratios [OBs: MD = 1:0, 1:0.5, 1:1, 1:1.5, and 1:2 (v/v)] on the physicochemical properties and oxidative stability of freeze-dried soybean OBs microcapsules were investigated. The effect of ultrasonic power (150–250 W) on the encapsulation effect and structural properties of oil body-maltodextrin (OB-MD) microcapsules were studied.

Results

The addition of MD to OBs decreased the surface oil content and improved the encapsulation efficiency and oxidative stability of OBs. Scanning electron microscopy images revealed that the sonication promoted the adsorption of MD on the surface of OBs, forming a rugged spherical structure. The oil-body-maltodextrin (OB-MD) microcapsules showed a narrower particle size distribution and a lower-potential absolute value at an MD addition ratio of 1:1.5 and ultrasonic power of 250 W (32.1 mV). At this time, MD-encapsulated OBs particles had the highest encapsulation efficiency of 85.3%. Ultrasonic treatment improved encapsulation efficiency of OBs and increased wettability and emulsifying properties of MD. The encapsulation of OBs by MD was improved, and its oxidative stability was enhanced by ultrasound treatment, showing a lower hydrogen peroxide value (3.35 meq peroxide/kg) and thiobarbituric acid value (1.65 μmol/kg).

Discussion

This study showed that the encapsulation of soybean OBs by MD improved the stability of OBs microcapsules and decreased the degree of lipid oxidation during storage. Ultrasonic pretreatment further improved the encapsulation efficiency of MD on soybean OBs, and significantly enhanced its physicochemical properties and oxidative stability.

Effect of Macroscopic Surface Heterogeneities on an Advancing Contact Line

The shape of a liquid-air interface advancing on a heterogeneous surface was studied experimentally, together with the force induced by the pinning of the contact line to surface defects. Different surfaces were considered with circular defects introduced as arrays of cocoa butter patches or small circular holes. These heterogeneous surfaces were submerged in aqueous ethanol solutions while measuring the additional force arising from the deformation of the advancing contact line and characterizing the interface shape and its pinning on the defects. Initially, the submersion force is linear with submerged depth, suggesting a constant defect-induced stiffness. This regime ends when the contact line depins from the defects. A simple scaling is proposed to describe the depinning force and the depinning energy. As the defect separation increases, the interface stiffness is found to increase too, with a weak dependency on the defect radius. This interaction between defects cannot be captured by simple scaling but can be well predicted by a theory considering the interface deformation in the presence of a periodic arrays of holes. Creating a four-phase contact line by including solid defects (cocoa butter) reduced pinning forces. The radius of the defect had a nonlinear effect on the depinning depth. The four-phase contact line resulted in depinning before the defects were fully submerged. These experimental results and the associated theory help to understand quantitatively the extent to which surface heterogeneities can slow down wetting. This in turn paves the way to tailoring the design of heterogeneous surfaces toward desired wetting performances.