Microstructural approach to Food Drying Operations- A quantitative approach

Microstructural approach to Food Drying Operations- A quantitative approach

Grape dehydration is practiced widely in the food industry with large yields of sultanas produced globally. This investigation examines the relationship between drying times and temperatures on grape microstructure. Grapes dried progressively over ten hours at two different temperatures were examined using scanning electron microscopy (SEM). Detailed images of the microstructure were obtained, and a unique image processing algorithm was developed to quantitatively analyse the properties of this microstructure. Two main methods were developed to obtain the complex boundaries of cells present in the grape tissue in over 36 SEM images. Segmentation of the binary image using an adapted watershed function obtained the most consistent and accurate morphological shape. This was compared to a secondary method which used Canny’s edge detection function, morphological closing and skeletonizing to outlines the cellular microstructure. MATLAB was utilised to convert these boundaries into measurable areas so that quantitative data on average cell area, perimeter and cell axis lengths was acquired. It was found that over drying time cell area and perimeter reduced as expected. Furthermore, that in general the higher temperature samples had smaller microstructural elements. Some variability in the data was clear due to only single samples being analysed for each temperature and time combination. Further images could be processed to obtain smoother and more convincing data in the future.

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