Govt. of India identified Controlled Atmosphere Technologies as one of the technologies to fund in-order to reduce these losses (India-2020 by Dr Abdul J Kalam).
Virtual System for Concurrent Monitoring and Control of Multiple Controlled Atmosphere Chambers K.S.N. Rao, S. Sadistap, Sai Krishna, Santosh Kumar Central Electronics Engineering Research Institute, Pilani. Abstract
Indian agricultural scientists have immensely contributed to innovation in agriculture in the disciplines of nutrition, breeding, genetic engineering, disease control, weed and pest eradication. This has made India self-sufficient in food grain production. The population of India has touched one billion and the need of our is more food grain production. This can be achieved by introducing state of art electronic technologies in agriculture production and processing. It is universal fact, losses is one of the main contributor for depleting the yield of any process. Agriculture is not an exception. The loss starts from harvesting, storage, distribution and consumption. Among these, looses during storage of food grains amounts to 10%. The losses without storage in India consist of some thousands of Crores/year (Approximately). Food storage also serves to protect against such occurrences as: Food shortages, natural disasters, unemployment, strikes, civil unrest, breakdown of food production and distribution. During the last few decades there has been an explosive growth in the market for fresh prepared fruit and vegetable products with prolonged shelf lives. The main driving force for this market growth is the increasing consumer demand for fresh, healthy, convenient and additive free prepared product items. However, fresh prepared produce items are highly perishable and prone to the major spoilage mechanisms of enzymatic disclosation, moisture loss and microbial growth. In order to meet these challenges, Govt. of India planning commission has funded CSIR to develop appropriate technologies for food storage. This paper dwells with controlled atmosphere (CA) storage automation. 1. Introduction India has immensely contributed in the field of agriculture through a series of innovative R&D program, which have resulted in self-sufficiency, higher yield, and better nutritional quality. Similar efforts have been made in the field of horticulture, floriculture, dairy and other products. In spite of our best efforts the yield of our crops are very low as compared to developed countries. Moreover, there are huge losses in handling storage, packaging, and transportation etc. of the agri-produce crops. There are 20-40% losses in these crops which amounts to 20-40 thousand crores of rupees per annum. Our export potential is less than 1%, due to low shelf-life of the horticulture crops during storage using traditional methods, which results in early ripening, mechanical damage, change in flavor and taste. It is a well-known fact that fresh fruits, vegetables and ornamental crops have living tissues, which begin to deteriorate immediately after harvest. Horticulture crops have high water contents and are thus subject to desiccation and mechanical injury, which leads to the growth of bacteria, fungus, and other microorganisms. Since India is the second largest producer of these products there is a great need to develop appropriate technology suiting Indian agri environment. Proper sorting, grading, storing, packing and non-destructive evaluation of quality aspects in fruits, vegetables, grain and foods are important and vital to satisfy the consumer needs, extend the shelf life, quality enhancement to generate more revenue. The estimated storage losses in the fruit and vegetable sector are around 25%. The projected losses by 2020 in terms of rupees is around 5900/ cr/yr. Govt. of India identified Controlled Atmosphere Technologies as one of the technologies to fund in-order to reduce these losses (India-2020 by Dr Abdul J Kalam) 2.Present Trends Presently sorting and grading is done by visual inspection of human experts, and storing is done in cold stores. This causes large variations in quality parameters and often become unfit for export. However new technologies offer solution for Storing of the fruits and vegetables in controlled environment lead to extension of shelf life and open up revenues for export by sea route at lower price. Good maintenance and handling practices along with the appropriate use Modified and Controlled Atmosphere are relatively effective in inhibiting these spoilage mechanisms, there by extending shelf life and higher quality. Shelf life extension also results in the commercial benefits of less wastage in manufacturing and retail display, long distribution channels, improved product image and ability to sell convenient, added value, fresh prepared produce items to the consumer with reasonable remaining chilled storage life. The technology of Modified Atmosphere (MA) and Controlled Atmosphere (CA) is widely used for the storage, transport and packaging of several types of foods. The principle of Modified Atmosphere refers to any atmosphere that is different than the normal air (20-21% O2, 0.03% CO2, 78% N2 and trace quantities of other gases). Once the gas mixture is introduced, no further control of the gas composition is exercised and the composition inevitably changes. So after changing the gas composition, the food items may be spoiled. Usually the modified and controlled atmospheres involve an atmosphere with reduced concentration of O2 and an elevated concentration of CO2. In order to maintain the food quality we should adopt the Controlled Atmosphere where the atmosphere composition is
maintained and controlled throughout the storage time. Using this we can increase the shelf life food items, retarding of metabolic processes such as ripening in fruits and vegetables, retardation of the loss of some nutritional substances such as vitamins, decay control, insect control and control of some physiological disorders such as chilling injury in some fruits and vegetables. 3.Factors affecting the processing parameters of Food Storage Parameters such as ambient conditions around the chamber and ambient conditions inside the chamber will affect the fruits under storage. The effect of some of the parameters on the fruits under store is given below. 3.1 Relative Humidity: Relative Humidity is the ratio of the actual water vapor pressure present in the air to the saturation vapor pressure at the prevailing temperature. It is usually expressed as a percentage. The relative humidity (RH.), at given water content, on temperature. Psychometer is best suited for the measuring of relative humidity in process industry (tea, mushroom etc.,) where the temperature ranges are from 0 to 70°C. Required RH levels can be maintained in several ways. The first is to keep our storage location air-conditioned during the warm and humid times of the year. The second is to package the goods in storage containers impervious to moisture and then to deal with the moisture trapped inside. Relative humidity needs to be monitored and controlled in storage. Recommended RH is 85-90% for fruits, 90-95% for vegetables (except dry onions and garlic). The addition of water vapor to a cold storage chamber can be controlled automatically with a humidistat. Temperature: Temperature measurement is not only used to detect active deterioration but also gives, along with moisture content, an indication of the potential for deterioration. Respiration and metabolic rates are directly related to room temperatures within a given range. Respiration can be described as the oxidative breakdown of the more complex materials present in cells, such as starch, sugars and organic acids into simpler molecules such as CO2 and water with the concurrent production of energy and other molecules which can be used by the cell for synthetic reactions. The higher the rate of respiration, the faster the produce deteriorates. Lower temperatures reduce respiration rates and the ripening and senescence processes, which prolong the storage life of fruits and vegetables. Low Temperatures also slow the growth of pathogenic fungi, which cause spoilage of fruits and vegetables in storage. The key to prolonging the storage life of edibles lies in lowering the temperature of the area in which they are stored. Ethylene: Ethylene, a natural hormone produced naturally by all plants and some other organs and also produced by some fruits as they ripen, promotes additional ripening of produce exposed to it. The damaged or diseased fruits produce high levels of ethylene and stimulate the other apples to ripen too quickly. As the fruits ripen, they become more susceptible to disease. Ethylene "producers" should not be stored with fruits, vegetables, or flowers that are sensitive to it. The result could be loss of quality, reduced shelf life and specific symptoms of injury. Ethylene producers include apples, apricots, avocados, ripening bananas, honeydew melons, papayas, peaches, pears, plums and tomatoes. Low temperature decreases production and action of ethylene. Nitrogen (N2): The use of liquid nitrogen as a refrigerant 100% N2 at 0 0C. N2 is a tasteless gas and is mostly used in Controlled Atmosphere as a filter gas because of its low solubility. N2 is almost insoluble in water and fat and will not absorb in to the food product. N2 is used to displace O2 from air with O2 sensitive products and as an alternative to vacuum to inhibit the growth of aerobic microorganisms. Oxygen: If the oxygen is permitted to go too low the produce becomes anaerobic, the tissue dies and begins to ferment causing permanent damage. This point can occur between 0.5% and 5%. 4. Controlled Atmosphere Storage (CA) CA is derived from Gas Control where levels of certain gasses around the stored items in chamber are monitored and maintained. In CA storage method, the levels of gasses such as O2, CO2, C2H4 along with Temperature and RH are continuously monitored and required % levels of O2, CO2 and C2H4 are maintained for a particular temperature and RH. Simply speaking CA storage is nothing but the effects of varying levels of O2 and CO2 on stored food items. In spite of biochemical, physiological and technological studies conducted on CA systems, it is still not yet known how it actually works. Controlled atmosphere (CA) is a well-known technique and an important alternative to chemical preservatives and pesticides. It has a great potential for reducing post-harvest losses and for maintaining both nutritional and market value. Thus it will be worth to develop a system for monitoring and control of various parameters responsible for proper storing.
Monitoring and controlling of parameters like oxygen, carbon dioxide, humidity, temperature, and ethylene are of utmost importance for proper storing of agricultural produce like fruits and vegetables to minimize their quality deterioration and spoilage. Moreover, monitoring and control of these parameters is also important in proper ripening of fruits. The environmental factors, which affect the storage of fruits & vegetables, are: Ethylene (0-15 ppm), CO2 (2-25%), O2 (2-10%), Temperature (-2 to 18° C), Relative humidity (80-100%) and Light (Wavelength selective).
Fig1: Mimic diagram of the Single Chamber Controlled Atmosphere Storage Chamber. At CEERI Pilani a system that monitors and controls the various parameters of a CA Storage chamber is developed and installed at CSIO Chandigarh and is undergoing field trials. Initially the system was developed for a single CA chamber and later extended to multiple CA chambers. Fig1. shows the mimic diagram of the CA system. Basically the whole system consists of a CA chamber along with refrigeration unit and humidifier, CO2 scrubber for absorbing excess CO2, Ethylene scrubber for absorbing excess Ethylene, Nitrogen generator for maintaining Oxygen, Sampling chamber for sensing various gas parameters , manual controller for manual control and a centralized controller along with solenoid Valve panel. Fig.2 shows the CA chamber along with centralized controller and manual controller.Fig3. shows the Auto/Manual controller Fig.4 shows the sensing chamber where in the sensors of Oxygen, Carbon dioxide and Ethylene are fitted on the sensing chamber. Air from CA chamber will be pumped in by means of a suction pump and after passing through the sensing chamber reenters the CA chamber. Fig.5 shows the solenoid valve panel. An individual valve serves each Gas and each valve can receive commands from manual controller as well as central controller. A bright LED indicates valve on/off position.
Fig.2 CA chamber along with centralized Controller
Fig.3 Auto/Manual Controller
Fig.4 Sensing Chamber
Fig.5. Solenoid valve panel
The whole application software is developed using virtual instrumentation concepts. The development platform used is LabVIEW. Stand-alone traditional instruments such as oscilloscopes and waveform generators are very powerful, expensive, and designed to perform one or more specific tasks defined by the vendor. Virtual instruments, by virtue of being PC-based, inherently take advantage of the benefits from the latest technology incorporated into off-the-shelf PCs. Virtual Instrument/system is more flexible. A traditional instrument might contain an integrated circuit to perform a particular set of data processing functions; in a virtual instrument, these functions would be performed by software running on the PC processor. You can extend the set of functions easily, limited only by the power of the software used. By employing virtual instrumentation solutions, you can lower capital costs, system development costs, and system maintenance costs, while improving time to market and the quality of your own products Basically the application software consists of: • Data Acquisition • Data Storage • Parameter Display • Process Mimic Diagram • Trend Graphing • User Graphical Interface • Control • Networking 5.Multiple CA storage System In most of the applications fruits will be stored in various small containers instead of a single big container. This helps them easy to handle and transport hence the need of a system, which can simultaneously monitor and control multiple CA chambers. The following sections describe the features of a Virtual system developed at CEERI for Concurrent monitoring and control of a multiple CA Storage chambers. Here we are providing the concurrent controlling, monitoring of Food storage chambers. So that one can monitor and control multiple chambers concurrently. Network facilities are also there to exchange data, which enable user to store and retrieve data more frequently and in less time. The data generated is stored in the database so that the user can retrieve the data later for analyzing purpose. The following are the monitored and controlled parameters for all the chambers. Each individual chamber will be provided with separate sensors and valves along with scrubbers but have one centralized controller. Fig.6 shows the schematic diagram of the system. The following are the monitored and controlled parameters of each CA Storage chamber. Monitored Parameters: To monitor the process parameters of food storage house such as Temperatures (T1, T2, T3), O2, RH, CO2, N2, and C2H4 Control Features: Initially ON/OFF control signals will be implemented for the following • Control of Temperature and RH by an independent unit supplied along with the CA system • Control Air inlet • Control of Nitrogen gas • Control of air through CO2 scrubber • Control of air through C2H4 scrubber Data acquisition modules: To provide Data Acquisition card link between local sensing Hardware and Central PC for monitoring and controlling the process parameters.
Database Connectivity: To store all the values generated by the system in to the database for further analysis. To provide on-line Trend graphs for analysis of data. Networking: The storage house developed would be deployed in large numbers and at different locations. Keeping in view this requirement, a network design using Virtual Private Network (VPN) concepts has been prepared. Using this network, it would be possible to monitor status of all the storage houses at any point in the network. Display: Process status display by mimic diagram on the PC screen. 6. Concurrent Monitoring, Control and Networking of multiple controlled Atmosphere (CA) storage Chambers The aim of Concurrent monitoring and networking of multiple controlled Atmosphere (CA) storage system is to develop a software module for monitoring and controlling the controlled Atmospheric (CA) parameters for food storage house using LabVIEW from one centralized controller. It can monitor and control multi chambers ( presently three) which are working concurrently. It also provides the facility of switching from one chamber to another for monitoring and controlling. In case of any emergency situation i.e. if in some chamber the level of temperature, oxygen, carbon dioxide, ethylene changes below or above some specified min or max range then the alarm sounds and the user will take necessary action to control the atmosphere in that chambers.
Fig 6. Block diagram of Multiple Controlled Atmosphere Chambers . Each chamber of multiple controlled atmosphere consists of same hard modules of a stand-alone CA chamber except a common centralised controller serving all the CA chambers. Efforts are being made to sharing of scrubbers , nitrogen generator and sensing chambers by all so that cost will be reduced. Working principle of controller: As already mentioned the main function of the controller is to maintain require % of gasses inside the CA chamber by properly regulating the respective control Valves of CO2 scrubber, C2H4 scrubber and required Temperatures and RH inside the CA chamber. Fig.1 shows the flow diagram of the application software. Initially the operator enters the required profile for the commodities under storage through the keyboard of the controller. Profile generally contains set points of O2; CO2; C2H4, Temp, RH and storage time along witch alarm limits of critical process parameters. After getting the storage profile the first operation the controller does is purging. In this operation it closes all valves except air valve and allows the atmospheric airflow freely through the CA chamber. Purging will continue until the operator acknowledges purging stop message. After receiving acknowledgement from operator, the controller closes all the valves including air valve and flashes message to load the material in the CA chamber. Once the operator acknowledges the storage of material, the controller enters into continuous control made. It tries to control Temp, RH, CO2, O2 and C2H4 by comparing individual set points with their respective on line values. Level of CO2 is maintained by opening or closing the CO2 valve and the levels of Ethylene are also maintained by opening or closing it scrubber valve. In the case of Oxygen its levels are maintained by controlling the Nitrogen valve or air valve as the case demands. Finally one the storage time is complete, the controller flashes message and starts shutdown procedure.
Broadly the main features of the system are as follows • • • • •
Monitoring on line, all process parameters Predicting the quality of the stored grain ( under development ) Wireless technology for interfacing sensors Data logging and demand prediction and Networking facility with other storage houses present in the area and mandis.
The proposed project envisages to modernize the grain, fruits and vegetables storage houses with wireless technology based on control system with facilities to link with other storage houses along with decision support systems for assisting food grain, fruits and vegetables managers. It also envisages developing technology for energy efficient storage houses and automated refrigeration system. Features such as vertical integration and wide viewing through web will be incorporated. .
Conclusion
Using the developed software module we can concurrently monitor the data of each Chamber (depending on the requirement) accurately and reliably. Using this system and data generated for various varieties of fruits it is planned to develop a storage model by means of which one can predict the quality of the produce under store without using -destructive methods. Using the proposed system we can increase the life period of grains, fruits and vegetables at least 4 to 10 times without deterioration of the food and to increase the quality of food and control the food conditions. Presently the system is undergoing field trials at CSIO, Chandigarh. The system will be utilized to generate storage profiles initially of Apples then for other fruits. Using the system storage, databases will be generated for predicting online quality of the fruits under storage. The Networking facility enables to view the status of the CA chamber from any corner of the country. Acknowledgements The authors thank CSIR for providing the necessary funds for developing the system. Thanks are also due to Director CEERI Pilani for his encouragement and continuous support. 1.
References Control System for Controlled Atmosphere Storage (CA) K.S.N.Rao etal International Conference on Instrumentation Dec. 2004
