Microstructural analysis of deep-fat fried formulated products by confocal laser scanning microscopy (CLSM) and fluorescent labelling

摘要

The controlling importance of microstructure in deep-fat frying has been greatly recognized when studying oil absorption mechanisms. This knowledge should be considered when designing novel fabricated products and the use of non-destructive microscopic techniques could be helpful in doing so. Food products formulation by the combination of components derived from raw agricultural materials, or food building blocks, could enable the localization of the specific components prior the process by the use of different fluorochromes with separated emission wavelengths, which could be followed through multi-channel confocal laser scanning microscopy (CLSM) observation. The objective of this work is to characterize the microstructure of different formulated products by means of fluorescent labelling of their main components prior to formulation and microscopy observation. Two fried products were formulated using different proportions of native wheat starch and wheat gluten. For each product, both ingredients were labelled prior to formulation by non-destructive procedures with Rhodamine B and fluorescein-5-isothiocyanate (FITC). The products were observed under CSLM. The acquired images enabled to observe the main components in the raw products, where the gluten network was distinguishable from wheat starch. In the crust of the fried product, native starch granules entrapped in the coagulated gluten network were observed. The inner region of the products was mainly constituted by gelatinized starch and gluten. This work demonstrates that the fluorescent labelling approach in the study of food ingredients functionality is a useful tool that could be used to understand and control the structural characteristics of formulated fried product and could be valuable in the design of novel products with tailor-made characteristics.