Food Structure


S. H. Yiu


Fluorescence microscopy was used to analyze the structural and microchemical organization of oat constituents in cooked and uncooked products of whole grain and three commercial ly available rolled oats. Results of the microscopic examination indicated that proteins and lipids in the endosperm tissue were most susceptible to processing. Instead of being individually packaged in distinct structural units like those found in unprocessed groats, both proteins and lipids appeared as aggregated masses after processing. Cooking induced further aggregation. Starch grains in the uncooked rolled oat samples still retained their granular. polygonal structures. although some compound grains were broken up into individual starch granules in quick rolled oats Partial gelatinization of starch was observed in instant rolled oat samples. Cooking resulted in many starch granules losing their original struc tural organization and their anisotropic charac teristics Most endospermic cell walls in the rolled oat samples were fractured due to the impact of mechanical processing; cooking released some of the 6 - glucans Not all the 6-glucans in rolled oats were dispersed by cooking; most of them remained associated with the fragmented cell walls. The aleurone and sub- aleurone walls were relatively resistant to processing and cooking Phytin and phenolic compounds were abundant in the sturdy aleurone layer of old fashioned rolled oats. Additional flaking, as in the production of quick and instant rolled oats, induced more cell wall breakage in the aleurone layer, leading to the exposure of its cell contents Cooking reduced the detectable number of phytin globoids in rolled oat samples whereas phenolic compounds remained strongly bound to the aleurone wall.

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