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Scanning Electron Microscopy (SEM) has been applied to the morphological study of various microcapsule systems. In addition to using standard preparation techniques for the examination of the outer structure of microcapsules, a new embedding and microtoming technique has been developed to allow the study of the inner structure of fractured capsules. The technique uses a new nonpolar embedding resin, Lowicryl HM-20, which is compatible with the microcapsule shell material, and does not introduce artifacts associated with the use of epoxy resins. We demonstrate the potential of SEM techniques as a tool for selection of wall materials, for the study of core materials distribution in microcapsules, and for elucidating the mechanisms of capsule formation and the effects of water-vapor uptake on microcapsule properties.

Microstructure was studied on spray‐dried microcapsules with wall systems consisting of mixtures of whey protein isolate (WPI) and maltodextrins (DE 5, 10, 15) or corn syrup solids (DE 24). Structure of microcapsules was appreciably affected by type of carbohydrate and by the WPI‐to‐carbohydrate ratio. The extent of surface indentation was inversely related to the proportion of WPI in the wall system. Ratio of low‐to‐high molecular weight solutes in the wall system affected structure. At a WPI‐to‐carbohydrate ratio of 1:1 or higher, whey proteins improved the surface‐smoothness and decrease surface indentation of maltodextrin‐based microcapsules. Combinations of WPI with high‐DE value carbohydrates were more effective than those with carbohydrates of low DE value in limiting surface‐dents formation.

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