Freezing is a process by which the temperature of the raw fish is reduced from the initial level to between 16 0 C and 18 0 C, and most of the fluid in it is converted to ice.
The eutectic point of food products, that is the minimum temperature at which all the fluid in it is turned to ice, is 550 to 650C, but such a low temperature cannot generally be reached in the food industry. Heat transfer during freezing is accompanied by mass transfer. Consequently, freezing must be regarded as a complex process of both heat and mass transfer.
The biochemical and physical changes in the fish during freezing, the refrigeration conditions (speed, duration, final temperature of the frozen fish), power consumption, and the peculiarities of the refrigeration method used- all are very significant factors in preparing high quality frozen fish.
Only live and perfectly fresh fish should be taken for freezing. It is also essential that they be graded by species and size.
Biological and chemical changes in fish during freezing. The freezing of fish is accompanied by important biological and chemical changes. The biological changes include the inhibition of micro-organisms at the surface and the interior of the fish, and even a reduction in the number of bacteria at the surface immediately after freezing. Owing to the low temperatures and the changes that result in the state of aggregation in the product, freezing is more lethal to micro-organisms than chilling, and frozen fish therefore will keep for a long time.
Biochemical reactions take place more slowly at low temperatures, but are not arrested even when the product is frozen. Glycogen breaks down during freezing and lactic acid forms. The maximum accumulation of lactic acid occurs in the temperature range between 2.50 C and 3.70C known as the critical range. With slow freezing, that is, at a comparatively high temperature, glycogen breaks down quickly.
During refrigeration substantial protein changes occur- the protein becomes denatured, as a result of which solubility changes drastically and the capacity of the product to swell and retain tissue juices is reduced. All this detracts from the food quality of fish, the flesh becomes dry and hard and loses certain properties essential for further processing particularly for canning.
Methods of fish refrigeration. The methods and equipment for commercial freezing are very varied. Freezing in a cold air medium, for example, may be carried out in natural conditions, or in a freezing chamber where low air temperature is maintained by artificial means, or in a special freezer in which cold air is circulated fairly rapidly. If a cold liquid medium (brine) is used as coolant, the fish may either be placed in direct contact with the brine, or may be separated from it by heat-conducting surface. Both ice and brine may sometimes be used for either contact, or indirect freezing. Lastly, new methods of freezing with a boiling coolant are being developed.
Freezing by natural frost is used in very cold climates, where fish are caught under ice and immediately laid out alive on the ice in a single layer, so as to expose as much of their surface as possible to heat transfer with the atmosphere and ice.
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Blast freezing. In old-style freezers fish are frozen on tubular racks in a refrigerating chamber. In these conditions in which part of the fish is in contact with metal, and part with slowly circulating air, freezing is slow and uneven. In modern freezers the rack method has been replaced by a blast of cold air. Various apparatus and installations have been developed not only ensuring high heat transfer coefficient, but also providing mechanical means for loading and unloading the fish.
Ice-and-salt freezing uses the principle of spontaneous cooling of a mixture of ice and salt (NaCl). The processes taking place simultaneously in the mixture are ice melting and salt-melting, both of which absorb heat. For a complete interaction between the constituents of the mixture the contact surface between them should be as large as possible. The technology of this method of freezing is simple: fish are placed in the mixture layer by layer and are either kept in direct contact with it (contact freezing) or are separated from it by a heat conducting wall (indirect contact freezing).
WAYS OF COOKING FISH
Baking. Large whole fish, thick fillets and slices of fish are suitable for baking. Whole fish are sometimes stuffed. Oven temperature of 3500 F. is recommended, with the length of time depending on the size and thickness of the fish. Sometimes higher temperature (around 5000 F.) is suggested for baking small fish or fillets and steaks, but at this temperature the baking time must be very short. Otherwise, the protein will be hardened and the connective tissue will be softened too much.
Broiling. A good method for cooking small thin fish, large fish that have been split and laid open, and shellfish like lobster and scallops is by broiling. A moderate temperature is achieved by keeping the surface of the fish several inches from the source of heat.
Cooking in water. Pieces of large fish and some shellfish, such as lobster and shrimp, may be cooked in water. The water surrounding the fish is held at simmering temperature in order to carry out the moderate-temperature rule of cooking foods high in protein content.
Cooking in steam. The same type of fish that is cooked in water may be steamed. In this method, the fish is placed on a perforated plate over boiling water and is surrounding with steam. The pan holding the fish must be tightly covered. This method of cooking fish is often called poaching.
Pan-frying. A suitable method for cooking small whole fish, fillets and steaks of larger fish is pan-frying. Frequently, the fish is coated with flour, corn meal or with milk or egg and fine breadcrumbs so that the surface will become crisp and brown. The fat must not be heated so hot that it smokes.
Deep-fat Frying. Small and fairly thin pieces of fish and scallops, clams, oysters, and shrimp may be deep-fat fried. The fish should be coated with egg and fine crumbs. This coating makes the outside crisp and attractively brown in color and also helps to prevent the absorption of fat by the pieces of fish. The temperature of the fat for deep-fat frying is in the moderate range of 350 to 375 degrees F., according to the sizes of the pieces. In general, the larger pieces are fried at the lower temperature.
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MARINADING OF FISH
All marinades may be divided into two groups: a) cold or salt, and b) warm marinades prepared from pre-fried, pre-cooked, or pre-smoked fish. Cold marinades are extensively used, because they keep well and are easier to prepare. Warm marinades are in fact made-up cooked dishes, and they will not be discussed here.
The preservative action of vinegar and vinegar- salt solution. The development of putrefactive micro-organisms is greatly delayed in an acid medium with a vinegar concentration of 1 to 2 per cent. With a higher proportion of acid, a number of bacteria die. The various micro-organisms react differently to being kept in an acid medium; some, like yeasts and mould, for example, will even thrive. Mould develops readily in an acid medium, and we know from experience that marinades are frequently affected by them. Moulds gradually decompose the acetic acid and thereby create favourable conditions for development of putrefactive bacteria.
Marinades are prepared from edible acetic acid (essence or vinegar) at a strength of 80 per cent. The acid is obtained either by dry distillation of wood or synthetically from acetylene. Its basic requirements are that it must be colourless and transparent, with no resinous odour, and contain no mineral acids or salts of heavy metals. Acetic acid is completely miscible with water.
Sometimes wine vinegar obtained by fermenting wine or diluted alcohol is used for marinades. Wine vinegar has a better taste and flavour, but as it contains only 3 to 5 per cent of acetic acid, it cannot be used unless it is produced on spot.
Marinading technique. Cold marinades may be prepared from both fresh and salted fish. It is usually considered that fresh fish gives a pleasant taste, but the better opportunities offered today for processing light salted intermediate products have led to the bulk of marinades being prepared from lightly cured fish.
Fish used for marinading include herrings, whitefish, and sardines, i.e. mainly those types that mature through salting. Marinades may be prepared from whole fish or from dressed ones. The dressing of the fish gives a good quality product and is also economically profitable. Gutted fish keep better, and some methods of dressing give the fish an attractive appearance. Defects due to mechanical damage are eliminated through dressing. Fish for marinading are gutted, gibbed, or cut up into trunks, pieces, or fillets.
Processing fresh fish. If fish are marinated fresh, they are dressed and washed, and then placed in a vat with a vinegar and salt solution. As a result, they are preserved and acquire a salty-sour taste. The salt and acid are chosen according to the season and to the type of flavour required. The marinades preferred in Russia are more salty than sour; the salt concentration in the vat therefore varies from 12 per cent to 18 per cent. In Western Europe, on the other hand, solutions contain 6 per cent salt and up to 6 per cent vinegar.
Packing fish in containers. The usual container for cold marinading fish is a wooden cask or a keg. Since marinades are fairly perishable, casks should be scrupulously clean. Wooden barrels can be a source of mould infection for fish, so they must be made of good quality wood and be thoroughly washed before use. The best method of treating them is with live steam.
Small-sized fish, or fish cut up into small pieces, are poured into the barrel and merely spread out in it. The fish may be fixed with condiments either on tables or during filling of the barrel. Large-sized fish (herrings) are packed in rows, and each row sprinkled with the condiment mixture.
QUALITY CONTROL IN THE FISH INDUSTRY
Quality control (QC) is now common in the fish industry and its use is increasing steadily as a demand for uniformly high quality products increases. Since fish is more variable than most other foods, the need to apply QC is correspondently greater. As customers and government become more particular about their food requirements, the fish industry must keep pace with these requirements not to lose out in the competition with other foods; it is therefore important that the principles of QC become widely appreciated in the industry.
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Quality control can be defined as maintenance of quality at a level that satisfies the customer and that is economical to the producer or seller. Quality is normally controlled by designated trained staff that have a clear knowledge of what the customer wants.
Process specification is a written description, mainly for the benefit of the producer, of how the product is to be made.
Product specification is a written description of what the customer wants.
Inspection is a part of QC and means examination of raw material or finished product to make sure it meets the specification.
Process control is a part of QC; it means checking the process, as distinct from the raw material or finished product, to ensure that all operations on the fish are done correctly and consistently to a set standard that is usually described in the process specification.
Quality is difficult to define, since it means different things to different people. One general definition is degree of excellence. In commerce, quality limits are set by what the customer is prepared to pay for; generally the customer will pay more for fish that he considers to be of higher quality, and will continue to buy as long as quality remains constant. Some of the more important factors that determine quality from the customers point of view are: species, ease of preparation, appearance, odour, flavour, freshness, size, presence or absence of bones, blood and filth, absence of specific microorganisms, condition, packaging, composition. Some aspects of quality are controlled by legislation, for example certain chemical additives or colouring materials may be prohibited in fish and fish products offered for sale or, in some countries, the maximum number of bacteria permitted may be specified.
The objective of QC is to assist the maintenance or improvement of profitability by minimizing customer complaints about quality, and hence to avoid the resulting lost business.
The complexity of QC depends on the size of company and the kind of products it is handling. However, four main stages at which QC is applied can be identified: 1) drawing up a product specification, 2) inspecting or testing raw material, 3) processing, 4) inspecting or testing finished products. Not all these stages necessarily will be present in every case.
INSPECTION OF RAW MATERIAL AND PRODUCT
Methods of inspecting and testing quality are of two main types, sensory or organoleptic tests, and instrumental and chemical tests. The first type employs only the human senses of sight, smell, taste and touch, whereas the second employs instruments like thermometers and chemical apparatus which are largely independent of human responses. Generally it is obvious which type should be used, and in the fish industry sensory methods are used most widely. One of the most important factors in choosing a method is the time available for testing. Thus the assessment of freshness in wet fish must often be made within an hour or two, whereas several days may be required for testing frozen fish. Sensory methods have disadvantages; for example the results can be variable and they depend on the operator. The main advantage of chemical methods is that when there is doubt or dispute about sensory measurements they can serve as reference methods.
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Sensory methods are of two types: subjective and objective. With a subjective method, the inspector makes a personal assessment; for example he may say whether he likes the sample of fish or not, how much he likes or dislikes it, and whether he would buy it. With an objective sensory method, the inspector attempts to assess the fish dispassionately and without prejudice by concentrating his attention on specific quality factors, for example degree of saltiness. Training and experience are necessary to enable him to do this accurately and reproducibly; he must become an expert.
Freshness. Freshness is a most important quality factor to the consumer; thus assessment is vital in QC. Freshness means how much the fish or fish product has spoiled when held in the wet state; when applied to frozen or canned fish, it means freshness of the fish before canning or freezing. Fish kept frozen for a long time may taste unpleasant because it develops off flavours in store, but these are not the same as those associated with stale wet fish.
MY SPECIALITY
Im a second-year student of the applied biotechnology faculty of the Voronezh State Technological Academy. My future speciality is a technology- engineer of Meat and Meat Products at the food enterprise. I consider my speciality to be one of the most interesting in our academy. The students of our faculty study many different subjects such as: Mathematics, Chemistry, Physics, Economics, Elements of Machines and Strength of Materials. To become qualified engineers we must know all the latest achievements in science and engineering. Now we study methods of meat processing, types of meat and meat products, meat composition, the history of meat production, the development of meat production in different countries, meat processing equipment. We get to know how to produce bacon, sausage, frankfurters, ham and cured meat. We get acquainted with such technological processes as anesthetizing, slaughtering, dehairing, dressing, cutting, sorting of parts, drying, curing, smoking, cooling, freezing, ageing. Except studying different disciplines we also do some theoretical and practical researches in our field. We write course-papers and collect materials for our future graduation paper under the guidance of our scientific supervisors.
The full academic course lasts five years. At the end of the course well present our graduation papers and defend them before an examination board. In such a way well get our diplomas and finally become graduates.
After graduating from the Academy I am going to work at a food enterprise as an engineer or a foreman. I can also work at research institutes or at experimental offices. Of course, its very difficult to find a good job due to many reasons but I hope for the best.
Besides studies we get practical training at meat plants of Voronezh and the Voronezh Region. We are introduced to the real production processes and latest achievements in Meat Industry to help us learn modern technological methods and handle the meat processing equipment. Of course, it will help us in future.
Some of the students who are interested in research and are successful in their studies have opportunities to be trained abroad. They also take part in research through the Students Scientific societies. The result of their work may be even published in our Academys Conference materials. Some graduates are admitted to a post-graduate training course where they continue their researches.
The teaching staff of the Academy do their best to educate highly qualified specialists for food and chemical industries.
The scientists of the Academy are doing fruitful work to make better use of food technologies, they conduct fundamental studies in physics, chemistry, biology and so on. As a result of these researches, different new devices for food technology have been designed; various modifications of installations have been worked out and manufactured.
BLOOD TYPE DIET
The Blood Type Diet, popularized by the best-selling book Eat Right for Your Type by Peter DAdamo, is based on the theory that people with different blood types respond differently to specific foods. Dr. DAdamos ideas are rooted in evolutionary history, and, specifically, the observation that different blood types (Type O, Type A, Type B, and Type AB) emerged as the environmental conditions and eating styles of our ancestors changed. Between 50, 000 BC and 25, 000 BC, all humans shared the same blood type Type O. These early humans were skilled hunters, and thrived on a meat-based diet. The Type A blood type emerged between 25, 000 BC and 15, 000 BC, a necessary adaptation to a more agrarian lifestyle. Climatic changes in the western Himalayan mountains led to the appearance of Type B, and the blending of Type A and Type B blood types in modern civilization resulted in the appearance of the Type AB blood type. Dr. DAdamo believes that our ancestors successful adaptation to environmental changes hinged on the relationship between diet and blood type. As a result, he believes that the key to optimal health is to eat as our ancestors with the same blood type ate. For example, DAdamo recommends that people with Type O blood eat a diet rich in meat and people with Type A blood follow a grain-based, low-fat, vegetarian diet. In the Blood Type Diet, foods are divided into 16 categories: meats and poultry; seafood; dairy and eggs; oils and fats; nuts and seeds; beans and legumes, cereals, breads and muffins; grains and pasta; vegetables; fruit; juices and fluids; spices; condiments; herbal teas; and miscellaneous beverages. Foods in these categories are then labeled as highly beneficial, neutral, or avoid according to each of the four blood types.
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Many people follow this diet to improve their overall level of health. Although weight management is not the focus of the diet, Dr.DAdamo believes that weight loss is a natural consequence of following a diet tailored to your blood type.
Dr. DAdamo has spent years researching the physiological effects of substances called lectins. Lectins are proteins found in many commonly eaten foods, particularly the seeds of leguminous plants; they can be absorbed intact from the digestive tract into the bloodstream. According to Dr.DAdamo, certain lectins are incompatible with certain blood types. The incompatibility allegedly causes the lectin to attract and clump red blood cells, a process known as agglutination. Dr.DAdamo blames lectin-caused agglutination as the origin of many common health complaints. Dr. DAdamo has tested most common foods for blood- type reactions. He organized the results of this testing into food lists that allow people to avoid eating foods containing lectins that are incompatible with their blood type.
Some physicians and nutritionists argue that Dr.DAdamos theory about lectins lacks solid scientific support. These critics point out that the research that has been done on lectins has been performed mostly in test tubes. Therefore, it is not yet known what, if any, physiological effects lectins have in humans. Furthermore, many food lectins are destroyed by cooking and/or digestive enzymes, so many critics argue that the number of lectins absorbed intact through the digestive system is minimal. Other critics point out that Dr. DAdamos emphasis on the ABO blood-typing system is somewhat arbitrary. In a book review, Alan Gaby, MD, points out that the ABO system is only one of many different blood-typing methods, and to date, more than 30 unique markers have been identified on the surface of red blood cells. Consequently, if Dr.DAdamo had based his diet on a different marker, his diet recommendations may have been very different.
Most critics believe the diet is associated with no real health hazards. However, critics caution that people with Type O blood may increase their risk of heart disease by adhering to Dr.DAdamos Type O diet recommendations.
Although most critics concede that the Blood Type Diet produces weight loss in some people, they argue that this diet is merely a calorie-restricted diet. As with any other low calorie diet, weight loss is likely to occur.
HEALTHY EATING WITH THE SEASONS
Seasons form the natural backdrop for eating. All of the Worlds Healthiest Foods are seasonal. Imagine a vegetable garden in the dead of winter. Now imagine this same garden on a sunny, summer day. How different things are during these two seasons of the year! For ecologists, seasons are considered a source of natural diversity. Changes in growing conditions from spring to summer or fall to winter are considered essential for balancing the earths resources and its life forms. But today its so easy for us to forget about seasons when we eat! Modern food processing and worldwide distribution of food make foods available year-round, and grocery stores shelves look much the same in December as they do in July.
In a research study conducted in 1997 by the Ministry of Agriculture, Fisheries and Food in London, England, significant differences were found in the nutrient content of pasteurized milk in summer versus winter. Iodine was higher in the winter; beta-carotene was higher in the summer. The Ministry discovered that these differences in milk composition were primarily due to differences in the diets of the cows. With more salt-preserved foods in winter and more fresh plants in the summer, cows ended up producing nutritionally different milks during the two seasons. Similarly, researches in Japan found three-fold differences in the vitamin C content of spinach harvested in summer versus winter.
Eat seasonally! To enjoy the full nourishment of food, you must make you menu a seasonal one. In different parts of the world, and even in different regions of one country, seasonal menus can vary. But here are some overriding principles you can follow to ensure optimal nourishment in every season:
Ø In spring, focus on tender, leafy vegetables that represent the fresh new growth of this season. The greening that occurs in springtime should be represented by greens on your plate, including Swiss chard, spinach, Romaine lettuce, fresh parsley, and basil.
Ø In summer, stick with light, cooling foods in the tradition of traditional Chinese medicine. These foods include fruits like strawberries, apple, pear, and plum; vegetables like summer squash, broccoli, cauliflower, and corn; and spices and seasonings like peppermint and cilantro.
Ø In fall, turn toward the more warming, autumn harvest foods, including carrot, sweet potato, onions, and garlic. Also emphasize the more warming spices and seasonings including ginger, peppercorns, and mustard seeds.
Ø In winter, turn even more exclusively toward warming foods. Remember the principle that foods taking longer to grow are generally more warming than foods that grow quickly. All of the animal foods fall into the warming category including fish, chicken, beef, lamb, and venison. So do most of the root vegetables, including carrot, potato, onions and garlic. Eggs also fit in here, as do corn and nuts.
In all seasons, be creative! Let the natural backdrop of spring, summer, fall and winter be your guide.
GENETICALLY MODIFIED FOOD
The 20th of November 1997 became a special day in the history of the Science Museum in London. On that day a new exhibition on Future Foods to show how genetically modified foods are made, what concerns some people have and what benefits such foods offer was opened there.
In todays busy world convenience and technology go hand in hand. Mobile phones, microwavesthe fruits of scientific research are everywhere. Food scientists are also doing their bit, working constantly to provide improved food products. The latest arrivals on the scene are so-called designer foods- foods which genetically modified or contain genetically modified ingredients. These foods are increasingly finding their way onto supermarket shelves.
All living things contain genes. We inherit them from our parents. Genes are the blueprints that carry the information for proteins that are the building blocks of all the structures and functions that make up the body of all organisms, from bacteria to humans. Genes and the proteins they make have coevolved together to form an extremely complex network of finely-balanced functions, which scientists are only just beginning to understand.
Unlike normal methods of reproduction, genetic modification is done in the laboratory by cutting, joining and transferring genes between totally unrelated living things. As a result, combinations of genes which would never occur naturally are produced.
Everyone has heard of Dolly the sheep and experiments in the medical field, but genetic modification is also happening in the food industry. It is possible to isolate and transfer different characteristics between unrelated species or between plants and animals. For example, the introduction of an anti-freeze gene from an Arctic fish into tomatoes or strawberries made them resistant to frost.
Around 40% of the worlds total crop production is lost to pests and diseases, despite the heavy use of pest-killing chemicals. Cauliflower is no exception, and suffers damage from aphids and other insects. Scientists have looked to nature to find a solution to this problem and discovered that snowdrops are able to survive attacks from some of the most devastating pests. Snowdrops produce a substance called lectin, which affects insects by interfering with their digestive systems. The task is to transfer the gene for lectin production, and thus the property of insect resistance, into cauliflowers.
It is known that tomatoes, carrots and peppers are all rich in carotenoids, which help prevent cancer and coronary heart disease. To make things easier for us, scientists are working to produce vegetables that are genetically modified to contain increased carotenoid levels. They have already succeeded in creating tomatoes with more than three times the normal anti-cancer power.
When salmon were modified with the gene for cold resistance from the flounder fish, they grew 10 times as fast as normal salmon because the inserted gene had inherited with their growth hormone gene. A pig was modified with a human gene to make it grow faster and leaner. But these efforts have resulted in numerous problems and serious diseases among the experimental animals.
People have different points of view about whether the genetic modification of food is a good thing in fact it is quite a controversial topic. Those involved in the biotechnology business insist it is safe and that genetic modification can increase yields, reduce waste and improve the flavour and keeping qualities of products. For example, soft fruits can be made firmer to prevent spoilage during transportation. People in favour of genetic modification also say that better use can be made of agricultural land as crops can potentially be modified to grow in hostile conditions, such as those of a drought; this will help in feeding the world. The latter is a vital issue. The same goes for improving the nutritional value of foods. More than 800 million people still go hungry, and 82 countries (half of them in Africa) neither grow enough food, nor can afford to import it. In India alone, 85% of children under five live below the normal, acceptable state of nutrition.
