Deteriorative change processing

The deteriorations and the deteriorative reactions of proteins have been studied by scientists in many different fields for many centuries. In order to give proper tribute to the almost ancient importance of proteins, it would be necessary to summarize the history of agriculture, medicine, food processing, and much of industry. Scientists and technologists have long recognized both the adverse and beneficial facets of deteriorative changes in proteins. 

Deteriorative Changes of Proteins During Soybean Food Processing and Their Use in Foods... 

Deterioration of the physical properties of proteins during food processing or food storage can be ascribed primarily to an irreversible insolubilization of proteins. However, a deteriorative change for one purpose can be a favorable one for another purpose. In Japan, for instance, the irreversible insolubilization of soybean proteins has been utilized effectively for production of soybean protein foods, such as tofu, kori-tofu, and yuba. 

The estimation performance of a statistical model will deteriorate when process characteristics change. Therefore, soft-sensors should be updated as process characteristics change. However, redesign of them is very laborious and it is difficult to determine when they should be updated. To cope with these problems, recursive PLS was proposed (Qin, 1998). Whenever both new input and output variables, and Pnew measured, the recursive PLS updates the model by using... 

The chemical nature of food components is of crucial importance for all aspects of food quality. It decides on the nutritional value of the product, its sensory attractiveness, the development of desirable or deteriorative changes due to interactions with other constituents and to processing, and the susceptibility and resistance to spoilage during storage. Food components that contain reactive groups, many of them essential for the quality of the products, are generally labile and... 

SPC only deals with the monitoring of the process and the identification of nonrandom variability sources in the process output. SPC does not deal directly with the adjustment of process parameters to compensate process deteriorations due to out-of-control conditions. Process adjustment (Del Castillo 2002) is instead the primary activity of engineering or automatic process control (EPC-APC). Recently researchers have advocated integrating SPC with EPC tools, which regularly change process inputs to improve process performance. 

The change of a material over time under defined natural or synthetic environmental conditions, leading to improvement or deterioration of properties. Also, changes caused by exposure to physical and chemical factors (viz., light, temperature, chemicals, weather), leading to irreversible deterioration. A process of exposing plastics to natural or artificial environmental... 

Adaptive Control. An adaptive control strategy is one in which the controller characteristics, ie, the algorithm or the control parameters within it, are automatically adjusted for changes in the dynamic characteristics of the process itself (34). The incentives for an adaptive control strategy generally arise from two factors common in many process plants (/) the process and portions thereof are really nonlinear and (2) the process state, environment, and equipment s performance all vary over time. Because of these factors, the process gain and process time constants vary with process conditions, eg, flow rates and temperatures, and over time. Often such variations do not cause an unacceptable problem. In some instances, however, these variations do cause deterioration in control performance, and the controllers need to be retuned for the different conditions. 

The Smith predictor is a model-based control strategy that involves a more complicated block diagram than that for a conventional feedback controller, although a PID controller is still central to the control strategy (see Fig. 8-37). The key concept is based on better coordination of the timing of manipulated variable action. The loop configuration takes into account the facd that the current controlled variable measurement is not a result of the current manipulated variable action, but the value taken 0 time units earlier. Time-delay compensation can yield excellent performance however, if the process model parameters change (especially the time delay), the Smith predictor performance will deteriorate and is not recommended unless other precautions are taken. 

In important process pumps, the grease in a bearing should be changed every 12 to 18 months. This will a,ssure a reliable pump operation and service because time alone causes certain deterioration in the lubricating ability of grea.se. 

Corrosion reactions in aggressive organic solvents are becoming a more frequent occurrence owing to developments in the chemical and petrochemical industries, and these reactions can lead to the deterioration of the metal and to undesirable changes in the solvent. This aspect of corrosion has recently been the subject of an extensive review by Heitz who has considered the mechanisms of the reactions, the similarities between corrt ion in organic solvents and in aqueous solutions, the methods of study and the occurrence of the phenomenon in industrial processes. 

---