Cryo-Scanning Electron Microscopy Investigation of the Texture of Cooked Potatoes
The texture of steam-cooked potatoes was investigated by examining the fracture planes of four different cultivars, using cryo-scanning electron microscopy (cryo-SEM), which yielded a good preservation of the hydrated structures in potato tissue . For all cultivars , fracturing after steam -cooking took place between cells preferentially alongside the cell walls. However, textural difference appeared from the degree of intercellular contact, the cell shape and the appearance of cell surfaces. Cells in the fracture planes of firm potatoes had large intercellular contacts. In this case, most of the cells were flat and cell surfaces showed folds and cracks . For mealy potatoes , it appeared that cells in the fracture planes had little intercellular contacts . The cells were round and turgid and had smooth surfaces . In conclusion, the structure of cell wall and middle lamella , and the starch content , appear to be important parameters to distingui sh firm and mealy cultivars. Key \Vords: Cell, cryo-scanning electron microscopy , potato, cultivar , steam-cooking, texture, fracture plane, pectin, starch, cell wall. Initial paper received March 19, 1992 Manuscript received September 8, 1992 Direct inquiries to J.T. van Marte Telephone number: 31 8370 75060 Fax number: 31 837
Food microstructure and starch digestion.
Microstructural characteristics of starch-based natural foods such as parenchyma or cotyledon cell shape, cell size and composition, and cell wall composition play a key role in influencing the starch digestibility during gastrointestinal digestion. The stability of cell wall components and the arrangement of starch granules in the cells may affect the free access of amylolytic enzymes during digestion. Commonly used food processing techniques such as thermal processing, extrusion cooking, and post-cooking refrigerated storage alter the physical state of starch (gelatinization, retrogradation, etc.) and its digestibility. Rheological characteristics (viscosity) of food affect the water availability during starch hydrolysis and, consequently, the absorption of digested carbohydrates in the gastrointestinal tract. The nonstarch ingredients and other constituents present in food matrix, such as proteins and lipids interact with starch during processing, which leads to an alteration in the overall starch digestibility and physicochemical characteristics of digesta. Starch digestibility can be controlled by critically manipulating the food microstructure, processing techniques, and food composition.
The parallel waveform relaxation stochastic Runge–Kutta method for stochastic differential equations
For large-scale non-autonomous Stratonovich stochastic differential equations, we study a very general parallel waveform relaxation process which is on the basis of stochastic Runge–Kutta (SRK) method of mean-square order 1.0 in this literature. The convergence of the whole parallel numerical iterative scheme can be guaranteed and the scheme provides better properties in terms of decreasing the load of the computation and operating speed. At the same time, the related limit method is also introduced as the continuous approximation derived from the iterative scheme. In the approximation interval, it is worth noting that the mean-square order of the parallel numerical iterative scheme can be kept consistent with the previous SRK method at any arbitrary time point, not just at discrete points. Some numerical simulations are presented to elaborate the computing efficiency of the parallel numerical iterative scheme.