Fisheries, Aquaculture Refrigerate Techniques
Refrigerate, freeze and fisheries will be built to hold, the most important element of refrigeration and cold storage cold storage of the property are as follows.
Selection of Cold Storage
Cold storage issues are taken into consideration in the selection of any business organization will be established in the region and the place taken into account.
– Be close to the harbor
– The train station, the airport, its proximity to the road or the road is within easy reach
– There is enough space in the storage area, easy entry and exit of vehicles
– To prevent the traffic of the center
– Does not harm the environment
– Be firm on the ground that the establishment Warehouse
Cold rooms for Fisheries
Cold stores for storing Fisheries are different from those for other food products. According to the amount of time because of the many variables to be stored Fisheries storage capacity and the number of rooms in the warehouse it is different. Great room and more room should be rather small.
Different refrigeration systems are used according to the product’s capability and market demand.
Refrigerate with natural Airflow
A method has been used since old times. Room shelves arranged on both side walls. This will be frozen on the shelf Water Products subject. ways left for work between shelves. Cold air mass in the evaporator tubes, are distributed to the other side of the room by natural air flow. heat possessed by the material to be frozen in another words, to the vicinity of the transport path evaporator pipes is spread by means of natural air flow. heat absorbed by the refrigerant in the evaporator. The freezing temperature of -25 ‘OC’ should be below. The density of the surrounding cold air mass Evapat more, because it is less dense warm air mass at the bottom of the room, above the cold air going down the hot air upwards interests. In this way the cycle (recirculation) is provided.
– Full breezy Refrigerate: Refrigerate is made tunnel-shaped chamber. This is referred to as the maintenance of the freezing tunnel. The substances to be frozen slowly passed through the tunnel on pallets. Meanwhile, around -35 ° C and -40 ° C evaporator temperature with cold air in, with the help of ventilators 4-6 m / s are sent quickly into the tunnel. Tunnel from the donor material. Best freezing -37 ° C wherein the 5 m / s is carried by the air stream with a like speed.
– Half breezy Refrigerate: Full-inspired refrigerate while losing a lot of moisture from the frozen material, although short, half-inspired freezing method for the same reasons as the amount of frozen material to be developed. Ceiling evaporator pipes placed. The two sidewalls are placed on the shelves as natural airflow freezing. The substances to be frozen are placed on these shelves.Evaporator pipes placed in front of a fan about 3 m / s air flow is provided. each side of the material inside the tank that this speed of airflow is not effective unfrozen simultaneously. If the profit for the quick freezing of the frozen internal organs without removing the internal organs of the fish must be turned in the direction from which the air flow.
– Plate in Unit Cooler Ice: breezy is another type of refrigerate. Curved pipe with the evaporator tube bundle is inserted into a thin plate and is mounted in front of a fan. Such evaporators are defined as singles plate evaporator. Plate evaporators, refrigerate is placed in a room outside the room. The effect of the cold air mass is formed around the evaporator fans to be sent through the pipes freezing. Fan breeze created by the loss of moisture will affect the food directly into the food becomes more. Furthermore, the internal heat generated by electric motor driving the fan in its refrigerant reduces the cooling capacity of the system.
Refrigerate with Saline
– The main part of refrigeration system is sodium chloride solution tank. After pre-cooling structures 20 baumes sodium chloride solution is transferred by the pump to the tank.
– In the tank bottom curved evaporator refrigerant solution in the pipe constant with the help of -18 oC stay it is provided.
– Also the solution at all points of the tank to be at the same temperature to be stirred with a pump.
– Products to be frozen is immersed in cold saline solution were placed into baskets.
– Quickly washed with water to remove salts on equipment after waiting for a certain time and thus the product.
– Product retention time of ice solution varies depending on the type of product. view consisting of salt crystals on the surface of the frozen product and may be a foam layer is not good.
Liquid Nitrogen Freezing
– Thermoforming temperature of 70-80 ° C up to temperatures of -18 C can reduce nutrients removed in 5 minutes.
– This is done by utilizing the latent heat of vaporization of the liquid nitrogen. However, it is very expensive. Therefore widely used in practice.
– Boiling point at atmospheric pressure of the liquid nitrogen -195.8 C, heat of vaporization of 47.6 kcal / kg melting temperature 20,1’C de 57.72 kcal / kg. Warming temperatures are 0.24 kcal / kg.
– Fish that have completed their pre-treatment prior to the preparation of refrigerate 0 ° C until placed in the room where the temperature is expected to drop to 1C of fish.
– Fish reduced to a desired temperature in the temperature range of Preparation B – 35 – -40 C which is placed in the freezing chamber. Freezing time; product thickness to be frozen, freezing pan on the structure of the product oil ratio, the freezing temperature varies depending on the reservoir to airflow.
– Fish coated with ice and taken from the room after the shock freezing process is complete cold is removed from the tank.
Ice Coating Frozen Aquatic Products
– Frozen fish products in cold storage if ever admitted to being applied to a process will cause some changes. dry surface of the fish, its unique smell disappears, the surface oxidized fats in fish. Water vapor, forms a layer of snow gathered around the evaporator and cooling difficult. revealed abnormalities called burn freeze. ice coating for all to avoid these drawbacks (Glazing) called the process is done.
– Ice the size of frozen fish in the coating process must be suitable water container. Water into the water container is filled and the temperature is lowered up to 2 ° C using ice. The formation of the water temperature is high, the fish on the surface of the ice layer becomes difficult.
– If the room temperature where the ice coating should be between 0 ° C and -5 ° C. Room temperature higher layer of ice crystals within the ice melts as not fully formed fish meat, the meat is tender.
– Frozen fish is big into water until the water is kept within the individual batırılır.3-6 seconds and removed. Meanwhile, just a layer of ice formed on the surface because of a low temperature of the frozen fish.
– Small fish are often frozen in the pan. Pan pan separation of frozen fish mold pouring water over the frozen fish is provided. Fish are kept immersed in water 3-6 seconds into the mold.
– Most of the ice coating frozen fish are removed once dipped into water 3 times with an interval of 5-10 seconds. The ice layer is more robust than would be the third layer.
– If a thick layer of ice on the frozen fish can be broken easily. It loses moisture through the cracks occurred. If it can not melt a very thin layer of ice on the surface of the fish. The best ice layer thickness is 3-5 mm.
Fisheries Solving defrost Process
Freezing fish meat during Changes
The structure of the meat during the freezing of the fish meat, the smell, significant change in color and nutritional value occurs.
During Freezing fish meat Chemical and Biological Changes
– When freezing fish meat nutritional value changes in physical and biological changes and chemical changes occur next.
– Fiziksek change: Fish flesh turns into ice in the water when freezing meat. Therefore increases the volume of the meat. The water in which fish contain about 1/9 up.
– Biological changes: ice crystals, cell fragments formed during the conversion of ice water in the meat. fungi and parasites in the meat of the dead. Bacteria do not die but stops the activity and proliferation.
– Changes in nutritional value: no great change in the proportion of various nutrients. However, vitamin C ratio is quite low. Vitamin C cryogenic temperatures easily separable.
– Liquid cells that break the ice crystals during the defrost frozen meat and interests of small-molecule substances out of flavors together.
Change the color of the meat
giving color to red blood cells in the frozen meat pieces by the effect of lower temperatures.Oxidation of hemoglobin in red meat with which the effects of enzyme that facilitates the oxidation also causes discoloration of the meat. After dark before the flesh turns gray.
Fisheries Taste Changes
cells lysed by ice crystals frozen meat. During defrost the meat softens. Remove the meat out of the cell fluid that is defrosting. This meat taste changes seen reason.
Exchange of proteins
protein molecules and become ice water in the environment in meats deteriorates. Impaired protein ratio freezing temperature after freezing will vary depending on storage time and storage temperature.
Change the oil
Fats found in fish stored in cold or frozen at lower temperatures oxidized and hydrolyzed. the burning of fat oxidation of fat in general is also called. changes result in reduced fat indirectly in the quality of the meat. At the end of changes in fat increases the acid value, iodine value of such a change would be minimal. Too much acid value is due to the hydrolysis of fats in meat frozen.
Changes occurring in fat frozen fish meat;
– Acid value of oil more iodine value varies very little. I.e. hydrolysis of the frozen fish meat more, oxidation is low.
– Freezing methods vary according to the rate of change in oil.
– The frozen product is dipped into the salt solution is more variation in fat. Because salt enhances the rate of the enzyme.
– Frozen fish meat covered with ice and reduced change the oil to prevent water loss in meat and fish.
ice crystals they have given back when they leave the heat shakin frozen food melted. Defrosting is the opposite of refrigerate. Defrost process;
– Natural defrost
– Defrost heating
– Done in three ways, namely electric defrost
Fisheries Natural defrost
– Air defrosting frozen food is left in the air inside. Air temperature of frozen food flows. Ice crystals in the food melts. Air temperature is high immediately soluble surfaces of bulky food. Inside, the interior remains undissolved ice crystals. softening the surface part begins bacterial activity.Resolving the outer parts of the interior could begin until the end of putrefaction.
– Water In defrosting iced water, made under normal temperature defrost water and warm water.During defrosting of frozen fish in the water, the impact on fish of airborne dust and bacteria is not in question. This is better than the maintenance of the air defrost method. temperature defrost the icy water made for slow autolysis rate in fish is low. However, more time is required for dissolution.Frozen fish, packed during the defrost frozen if they are not affected by water. However frozen fish lose their water-soluble protein in water without waiting packaging. Meat, absorbs water and softens.
Heating with Defrost
The method usually applied to a small piece of frozen product. Frozen products are thrown into boiling water, on the water or sprayed in the air is heated. In this method, it is not possible to control the degree to defrost end. Frozen fish central heating is not stopped when the temperature of -1 C.Proteins on the frozen fish deteriorates Faced with a sudden high temperatures (kuagül A) happen.yellowing of the environment, such as shell fish. nourishing fluid does not leave the fish in the fish.This is a good method and direction.
Low-frequency electric current, and there are 2 types of high-frequency electrical current to be me.Frozen food, dissolves rapidly starting from the center. It is a good method to prevent the liquid out of food.
Source: MEGEP, Fisheries Refrigerate