Wyniki 1-5 spośród 5 dla zapytania: authorDesc:"Jolanta Wawrzyniak"

Design of the Control System for Canned-Food Sterilization DOI:10.15199/65.2015.8.7


  A properly designed control system for canned-food sterilization is able to achieve the final desired level of bacterial inactivation, irrespective of any disturbances, e.g. in the form of undesired changes of the heating- -medium temperature, and with a minimum of over-processing. The feed-forward control system for canned- food sterilization was described in the article. The controller in such a system is able: (a) to anticipate the change of the final cumulative lethality in a situation when the disturbances of the process occurred during heating and (b) to take appropriate corrective actions that can eliminate such disturbances. The heating turn-off decisions in such a controller are based upon the prediction (in every second during heating) of cumulative lethality for the cooling stage. The prediction of the cooling phase is based on a simulation of temperature changes in the coldest point inside a can using the empirical m-th order step-response model.The most important factors in sterilization of food products are quality, safety, and low consumption of energy. Traditionally, sterilization of food refers to in container sterilization, in which a product is filled into a container, the container is hermetically sealed and heated to a temperature for a length of time such that living microorganisms are destroyed, and then it is cooled to room temperature for distribution. If the cumulative lethal effect delivered by a control system is under the desired best value, it may seriously endanger public safety and if it is over, energy is wasted and nutrient properties of the product are over-reduced due to overheating. Thermo-bacteriology defines an optimal level of bacterial inactivation in terms of cumulative lethality for every group of food products [2, 3, 16, 19]. There are several methods for the on-line calculation of bacterial inactivation but usually cumulative lethality (also called the sterilization value)[...]

Basics of Process Control: the On-Off Control System DOI:10.15199/65.2015.11.6


  This article explains the basic terms of process control: dynamic process as an object of control, process variable called also controlled variable, control (or manipulated) variable, control system, control with the feed-back loop as well as the principle of operation and quality indicators of the on-off control. To show indicators determining the quality of the on-off control, changes of process variable vs. time during this type of control were drawn. This was done based on: depicted static characteristic of a typical on-off controller, and parameters that characterize the dynamics of the object - a typical process of heat flow in a tank. Two parameters of the object (time-constant and time-delay) were drawn graphically using the step- -response characteristic of the above mentioned thermal-process.Food technology engineers have to depend not only on their knowledge of microbiology, food processing etc. but also on the basic principles of automatic control engineering [4, 5, 10]. Knowledge in this area can help them to work with control engineers and design control systems for the food industry. Unit processes in the technological lines of food processing cannot be conducted without proper supervision and automatic control because they should run in strictly defined ways. The course of the processes is frequently disturbed by various factors, therefore there is a need for constant control. Controlling of the course of unit processes can be assigned to a man or a machine. Assigning control of processes to a machine is called automation of these processes, i.e. self-performing (automatos in Greek). Selfperformed are mostly activities which are either dangerous, done in difficult conditions for a man or simple and monotonous and thus troublesome. BASIC TERMS The first aim of this article is to explain the basics of automatic control with minimal usage of mathematics based on literature database. The basis for analysis[...]

Drying Control Design - Case Study on the Near-Ambient Drying of Rapeseed DOI:10.15199/65.2017.4.4


  Rapeseed oil producers should be interested in the near-ambient method of drying because the quality of rapeseed dried using this method is higher than that dried using high temperature methods. The design of a generalized control strategy for drying seeds in bulk in the climate that is a mixture of maritime and continental climates (such as in Poland and many other European countries) in the form of the block diagram is shown in this article. Such a block diagram can serve as an interface between food processing engineers and control engineers enabling further implementation of the above mentioned control strategy in industry. It combines a model-based prediction units, two-position-like control actions and drying process to be controlled with slow dynamics and strong averaging properties. In this article some benefits of the application of a generalized control strategy for near-ambient drying of seed have been given (based on literature reviews) - mainly significant reduction of drying costs in comparison to other control strategies used for this method of drying.The producers of rapeseed oil require that the raw material retains a high quality throughout the whole season of storage and processing. Rapeseed is a very sensitive biomaterial because of its structure. Its quality depends mostly on the post-harvest processing conditions, especially the drying temperature and drying method. High drying temperature affects the acid and peroxide value, which are significant indicators of the quality of rapeseed. The application of high temperatures leads to oxidative changes lowering the quality of the obtained oil. The degradation of phytosterols in rapeseed dried in near-ambient temperature is on average two times lower in comparison to rapeseed dried with hot air in temperatures 60-100°C [3]. Thus, oil obtained from rapeseed that was dried using near-ambient method has higher quality than that obtained from rapeseed d[...]

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