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78-453: Ultra-high temperature processing ( UHT ), ultra-heat treatment , or ultra-pasteurization is a food processing technology that sterilizes liquid food by heating it above 140 °C (284 °F) – the temperature required to kill bacterial endospores – for two to five seconds. UHT is most commonly used in milk production, but the process is also used for fruit juices, cream, soy milk, yogurt, wine, soups, honey, and stews. UHT milk

156-488: A characteristic appearance of a swelled pillow formed out of metal. A waste heat recovery unit (WHRU) is a heat exchanger that recovers heat from a hot gas stream while transferring it to a working medium, typically water or oils. The hot gas stream can be the exhaust gas from a gas turbine or a diesel engine or a waste gas from industry or refinery. Large systems with high volume and temperature gas streams, typical in industry, can benefit from steam Rankine cycle (SRC) in

234-450: A constant temperature but still allows for the heat exchanger to accept additional heat. One example where this has been investigated is for use in high power aircraft electronics. Heat exchangers functioning in multiphase flow regimes may be subject to the Ledinegg instability . Direct contact heat exchangers involve heat transfer between hot and cold streams of two phases in the absence of

312-439: A few may cause problems for some individuals, including sulfites, artificial sweeteners, artificial colors and flavors, sodium nitrate, BHA and BHT, olestra, caffeine and monosodium glutamate — a flavor enhancer. When designing processes for the food industry the following performance parameters may be taken into account: Food processing industries and practices include the following: Heat exchanger A heat exchanger

390-438: A greater transfer of heat and a decrease in pressure. 4. Condensers and Boilers Heat exchangers using a two-phase heat transfer system are condensers, boilers and evaporators. Condensers are instruments that take and cool hot gas or vapor to the point of condensation and transform the gas into a liquid form. The point at which liquid transforms to gas is called vaporization and vice versa is called condensation. Surface condenser

468-408: A heat exchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant flows through radiator coils and air flows past the coils, which cools the coolant and heats the incoming air . Another example is the heat sink , which is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or

546-447: A hermetic bottling technique that would preserve food for French troops which ultimately contributed to the development of tinning, and subsequently canning by Peter Durand in 1810. Although initially expensive and somewhat hazardous due to the lead used in cans, canned goods would later become a staple around the world. Pasteurization , discovered by Louis Pasteur in 1864, improved the quality and safety of preserved foods and introduced

624-490: A large profit potential exists for the manufacturers and suppliers of processed food products. Individuals may see a benefit in convenience , but rarely see any direct financial cost benefit in using processed food as compared to home preparation. Processed food freed people from the large amount of time involved in preparing and cooking "natural" unprocessed foods. The increase in free time allows people much more choice in life style than previously allowed. In many families

702-420: A liquid coolant. There are three primary classifications of heat exchangers according to their flow arrangement. In parallel-flow heat exchangers, the two fluids enter the exchanger at the same end, and travel in parallel to one another to the other side. In counter-flow heat exchangers the fluids enter the exchanger from opposite ends. The counter current design is the most efficient, in that it can transfer

780-478: A noncritical temperature (70–80 °C [158–176 °F] for milk), and then quickly heated to the temperature required by the process. There are two types of heating technologies: direct , where the product is put in a direct contact with the hot steam, and indirect , where the product and the heating medium remain separated by the equipment's contact surfaces. The main goals of the design, both from product quality and from efficiency standpoints, are to maintain

858-418: A second flowpath ( the 'Shell side'). Plate and shell technology offers high heat transfer, high pressure, high operating temperature , compact size, low fouling and close approach temperature. In particular, it does completely without gaskets, which provides security against leakage at high pressures and temperatures. A fourth type of heat exchanger uses an intermediate fluid or solid store to hold heat, which

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936-475: A shelf life of about two weeks from processing, or about one week from being put on sale. The most commonly applied technique to provide a safe and shelf-stable milk is heat treatment. The first system involving indirect heating with continuous flow (125 °C [257 °F] for 6 min) was manufactured in 1893. In 1912, a continuous-flow, direct-heating method of mixing steam with milk at temperatures of 130 to 140 °C (266 to 284 °F; 403 to 413 K)

1014-627: A single phase , heat exchangers can be used either to heat a liquid to evaporate (or boil) it or used as condensers to cool a vapor and condense it to a liquid. In chemical plants and refineries , reboilers used to heat incoming feed for distillation towers are often heat exchangers. Distillation set-ups typically use condensers to condense distillate vapors back into liquid. Power plants that use steam -driven turbines commonly use heat exchangers to boil water into steam . Heat exchangers or similar units for producing steam from water are often called boilers or steam generators. In

1092-399: A solid heat exchanger similar to those used for pasteurization. However, as higher temperatures are applied, it is necessary to employ higher pressures in order to prevent boiling. There are three types of exchangers in use: For higher efficiency, pressurized water or steam is used as the medium for heating the exchangers themselves, accompanied with a regeneration unit which allows reuse of

1170-414: A stream that must be cooled to another stream that must be heated, such as distillate cooling and reboiler feed pre-heating. This term can also refer to heat exchangers that contain a material within their structure that has a change of phase. This is usually a solid to liquid phase due to the small volume difference between these states. This change of phase effectively acts as a buffer because it occurs at

1248-452: A study published in " Food & Nutrition Research " in 2010, meaning more of their food energy content is retained within the body. Processed foods also tend to be more allergenic than whole foods, according to a June 2004 "Current Opinion in Allergy and Clinical Immunology" article. Although the preservatives and other food additives used in many processed foods are generally recognized as safe,

1326-619: A study published in " The American Journal of Clinical Nutrition " in December 2007. Foods that have undergone processing, including some commercial baked goods, desserts, margarine, frozen pizza, microwave popcorn and coffee creamers, sometimes contain trans fats . This is the most unhealthy type of fat, and may increase risk for high cholesterol, heart disease and stroke. The 2010 Dietary Guidelines for Americans recommends keeping trans fat intake as low as possible. Processed foods may actually take less energy to digest than whole foods, according to

1404-405: A thin sheet of metal welded to the thicker surface of a tank or vessel, or two thin sheets welded together. The surface of the plate is welded with a regular pattern of dots or a serpentine pattern of weld lines. After welding the enclosed space is pressurised with sufficient force to cause the thin metal to bulge out around the welds, providing a space for heat exchanger liquids to flow, and creating

1482-494: A tube-based heat exchanger is common when one of the working fluids is a low-pressure gas, and is typical for heat exchangers that operate using ambient air, such as automotive radiators and HVAC air condensers . Fins dramatically increase the surface area with which heat can be exchanged, which improves the efficiency of conducting heat to a fluid with very low thermal conductivity , such as air. The fins are typically made from aluminium or copper since they must conduct heat from

1560-404: A tubes & fins configuration. 3. Plate Heat Exchanger A plate heat exchanger contains an amount of thin shaped heat transfer plates bundled together. The gasket arrangement of each pair of plates provides two separate channel system. Each pair of plates form a channel where the fluid can flow through. The pairs are attached by welding and bolting methods. The following shows the components in

1638-468: A waste heat recovery unit, but these cycles are too expensive for small systems. The recovery of heat from low temperature systems requires different working fluids than steam. An organic Rankine cycle (ORC) waste heat recovery unit can be more efficient at low temperature range using refrigerants that boil at lower temperatures than water. Typical organic refrigerants are ammonia , pentafluoropropane (R-245fa and R-245ca), and toluene . The refrigerant

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1716-415: Is a plate and shell heat exchanger, which combines plate heat exchanger with shell and tube heat exchanger technologies. The heart of the heat exchanger contains a fully welded circular plate pack made by pressing and cutting round plates and welding them together. Nozzles carry flow in and out of the platepack (the 'Plate side' flowpath). The fully welded platepack is assembled into an outer shell that creates

1794-471: Is a system used to transfer heat between a source and a working fluid . Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. They are widely used in space heating , refrigeration , air conditioning , power stations , chemical plants , petrochemical plants , petroleum refineries , natural-gas processing , and sewage treatment . The classic example of

1872-446: Is boiled by the heat source in the evaporator to produce super-heated vapor. This fluid is expanded in the turbine to convert thermal energy to kinetic energy, that is converted to electricity in the electrical generator. This energy transfer process decreases the temperature of the refrigerant that, in turn, condenses. The cycle is closed and completed using a pump to send the fluid back to the evaporator. Another type of heat exchanger

1950-433: Is called " (dynamic) scraped surface heat exchanger ". This is mainly used for heating or cooling with high- viscosity products, crystallization processes, evaporation and high- fouling applications. Long running times are achieved due to the continuous scraping of the surface, thus avoiding fouling and achieving a sustainable heat transfer rate during the process. In addition to heating up or cooling down fluids in just

2028-512: Is commonly used in the dairy industry for cooling milk in large direct-expansion stainless steel bulk tanks . Nearly the entire surface area of a tank can be integrated with this heat exchanger, without gaps that would occur between pipes welded to the exterior of the tank. Pillow plates can also be constructed as flat plates that are stacked inside a tank. The relatively flat surface of the plates allows easy cleaning, especially in sterile applications. The pillow plate can be constructed using either

2106-428: Is different from that of pasteurized milk , which prevents it from separating in cheese making. Two studies published in the late 20th century showed that UHT treatment causes proteins contained in the milk to unfold and flatten, and the formerly "buried" sulfhydryl (SH) groups, which are normally masked in the natural protein, cause extremely-cooked or burnt flavours to be sensed by the human palate. One study reduced

2184-724: Is less popular in Northern Europe and Scandinavia, particularly in Denmark, Finland, Norway, Sweden, the United Kingdom and Ireland. It is also less popular in Greece, where fresh pasteurized milk is the most popular, due to legislation and societal attitudes. While most regular milk sold in the United States is pasteurized, a significant share of organic milk sold in the US is UHT treated (organic milk

2262-518: Is made at home, in a small bakery, or in a large factory, is an example of secondary food processing. Fermenting fish and making wine , beer , and other alcoholic products are traditional forms of secondary food processing. Sausages are a common form of secondary processed meat, formed by comminution (grinding) of meat that has already undergone primary processing. Most of the secondary food processing methods known to humankind are commonly described as cooking methods . Tertiary food processing

2340-1110: Is necessary to make most foods edible while secondary food processing turns ingredients into familiar foods, such as bread . Tertiary food processing results in ultra-processed foods and has been widely criticized for promoting overnutrition and obesity , containing too much sugar and salt , too little fiber , and otherwise being unhealthful in respect to dietary needs of humans and farm animals. Primary food processing turns agricultural products, such as raw wheat kernels or livestock, into something that can eventually be eaten. This category includes ingredients that are produced by ancient processes such as drying , threshing , winnowing and milling grain, shelling nuts , and butchering animals for meat. It also includes deboning and cutting meat, freezing and smoking fish and meat, extracting and filtering oils, canning food, preserving food through food irradiation , and candling eggs , as well as homogenizing and pasteurizing milk . Contamination and spoilage problems in primary food processing can lead to significant public health threats, as

2418-655: Is not necessary to limit the sugars found naturally in whole, unprocessed foods like fresh fruit, eating too much added sugar found in many processed foods increases the risk of heart disease, obesity, cavities and Type 2 diabetes. The American Heart Association recommends women limit added sugars to no more than 420 kilojoules (100 kilocalories), or 25 grams, and men limit added sugars to no more than 650 kJ (155 kcal), or about 38.75 grams, per day. Currently, Americans consume an average of 1,490 kJ (355 kcal) from added sugars each day. Processing foods often involves nutrient losses, which can make it harder to meet

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2496-439: Is only truly possible on a wide scale because of food processing. Transportation of more exotic foods, as well as the elimination of much hard labor gives the modern eater easy access to a wide variety of food unimaginable to their ancestors. The act of processing can often improve the taste of food significantly. Mass production of food is much cheaper overall than individual production of meals from raw ingredients. Therefore,

2574-557: Is produced at fewer locations and consequently spends more time in the supply chain and could therefore spoil before or shortly after being sold if pasteurized). UHT milk contains the same amount of calories and calcium as pasteurized milk . Some loss of vitamin B 12 , vitamin C (of which milk is not a significant source), and thiamin can occur in UHT milk. UHT milk contains 1 μg of folate per 100 g , while pasteurized milk contains 9 μg . UHT milk's protein structure

2652-443: Is produced. Plates are produced in different depths, sizes and corrugated shapes. There are different types of plates available including plate and frame, plate and shell and spiral plate heat exchangers. The distribution area guarantees the flow of fluid to the whole heat transfer surface. This helps to prevent stagnant area that can cause accumulation of unwanted material on solid surfaces. High flow turbulence between plates results in

2730-447: Is the plate heat exchanger . These exchangers are composed of many thin, slightly separated plates that have very large surface areas and small fluid flow passages for heat transfer. Advances in gasket and brazing technology have made the plate-type heat exchanger increasingly practical. In HVAC applications, large heat exchangers of this type are called plate-and-frame ; when used in open loops, these heat exchangers are normally of

2808-468: Is the commercial production of what is commonly called processed food . These are ready-to-eat or heat-and-serve foods, such as frozen meals and re-heated airline meals . Food processing dates back to the prehistoric ages when crude processing incorporated fermenting, sun drying, preserving with salt , and various types of cooking (such as roasting, smoking, steaming, and oven baking), Such basic food processing involved chemical enzymatic changes to

2886-402: Is the most common type of condenser where it includes a water supply device. Figure 5 below displays a two-pass surface condenser. The pressure of steam at the turbine outlet is low where the steam density is very low where the flow rate is very high. To prevent a decrease in pressure in the movement of steam from the turbine to condenser, the condenser unit is placed underneath and connected to

2964-617: Is then moved to the other side of the heat exchanger to be released. Two examples of this are adiabatic wheels, which consist of a large wheel with fine threads rotating through the hot and cold fluids, and fluid heat exchangers. This type of heat exchanger uses "sandwiched" passages containing fins to increase the effectiveness of the unit. The designs include crossflow and counterflow coupled with various fin configurations such as straight fins, offset fins and wavy fins. Plate and fin heat exchangers are usually made of aluminum alloys, which provide high heat transfer efficiency. The material enables

3042-493: The thiol content by immobilizing sulfhydryl oxidase in UHT-heated skim milk and reported, after enzymatic oxidation , an improved flavor. Two US authors prior to heating added the flavonoid compound epicatechin to the milk, and reported a partial reduction of thermally generated aromas. Food processing The Nova classification groups food according to different food processing techniques. Primary food processing

3120-502: The 20th century, automatic appliances like microwave oven , blender , and rotimatic paved way for convenience cooking . In western Europe and North America, the second half of the 20th century witnessed a rise in the pursuit of convenience. Food processing companies marketed their products especially towards middle-class working wives and mothers. Frozen foods (often credited to Clarence Birdseye ) found their success in sales of juice concentrates and " TV dinners ". Processors utilised

3198-661: The LMTD is not available and the NTU method is used. Double pipe heat exchangers are the simplest exchangers used in industries. On one hand, these heat exchangers are cheap for both design and maintenance, making them a good choice for small industries. On the other hand, their low efficiency coupled with the high space occupied in large scales, has led modern industries to use more efficient heat exchangers like shell and tube or plate. However, since double pipe heat exchangers are simple, they are used to teach heat exchanger design basics to students as

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3276-558: The United States. In the American market, consumers are uneasy about consuming milk that is not delivered under refrigeration, and reluctant to buy it. To combat this, Parmalat is selling its UHT milk in old-fashioned containers, unnecessarily sold from the refrigerator aisle. UHT milk is also used for many dairy products. In 2008, the UK government proposed to produce nine units out of every ten as UHT by 2020, which they believed would significantly cut

3354-628: The adults are working away from home and therefore there is little time for the preparation of food based on fresh ingredients. The food industry offers products that fulfill many different needs: e.g. fully prepared ready meals that can be heated up in the microwave oven within a few minutes. Modern food processing also improves the quality of life for people with allergies, diabetics , and other people who cannot consume some common food elements. Food processing can also add extra nutrients such as vitamins . Processing of food can decrease its nutritional density. The amount of nutrients lost depends on

3432-581: The basic structure of food in its natural form, as well served to build a barrier against surface microbial activity that caused rapid decay. Salt-preservation was especially common for foods that constituted warrior and sailors' diets until the introduction of canning methods . Evidence for the existence of these methods can be found in the writings of the ancient Greek , Chaldean , Egyptian and Roman civilizations as well as archaeological evidence from Europe , North and South America and Asia. These tried and tested processing techniques remained essentially

3510-438: The body's needs if these nutrients are not added back through fortification or enrichment. For example, using high heat during processing can cause vitamin C losses. Another example is refined grains, which have less fiber, vitamins and minerals than whole grains. Eating refined grains, such as those found in many processed foods, instead of whole grains may increase the risk for high cholesterol , diabetes and obesity, according to

3588-405: The dimensions and configurations the boilers are manufactured. Several boilers are only able to produce hot fluid while on the other hand the others are manufactured for steam production. Shell and tube heat exchangers consist of a series of tubes which contain fluid that must be either heated or cooled. A second fluid runs over the tubes that are being heated or cooled so that it can either provide

3666-449: The exchanger. The exchanger's performance can also be affected by the addition of fins or corrugations in one or both directions, which increase surface area and may channel fluid flow or induce turbulence. The driving temperature across the heat transfer surface varies with position, but an appropriate mean temperature can be defined. In most simple systems this is the " log mean temperature difference " (LMTD). Sometimes direct knowledge of

3744-405: The flow-induced vibrations. There are several variations of shell-and-tube exchangers available; the differences lie in the arrangement of flow configurations and details of construction. In application to cool air with shell-and-tube technology (such as intercooler / charge air cooler for combustion engines ), fins can be added on the tubes to increase heat transfer area on air side and create

3822-400: The fluids, as it creates a larger temperature differential when used under otherwise similar conditions. The figure above illustrates the parallel and counter-flow flow directions of the fluid exchanger. 2. Shell-and-tube heat exchanger In a shell-and-tube heat exchanger, two fluids at different temperatures flow through the heat exchanger. One of the fluids flows through the tube side and

3900-490: The food and processing method. For example, heat destroys vitamin C . Therefore, canned fruits possess less vitamin C than their fresh alternatives. The USDA conducted a study of nutrient retention in 2004, creating a table of foods, levels of preparation, and nutrition. New research highlighting the importance to human health of a rich microbial environment in the intestine indicates that abundant food processing (not fermentation of foods) endangers that environment. One of

3978-418: The fundamental rules for all heat exchangers are the same. 1. Double-pipe heat exchanger When one fluid flows through the smaller pipe, the other flows through the annular gap between the two pipes. These flows may be parallel or counter-flows in a double pipe heat exchanger. (a) Parallel flow, where both hot and cold liquids enter the heat exchanger from the same side, flow in the same direction and exit at

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4056-568: The gasket type to allow periodic disassembly, cleaning, and inspection. There are many types of permanently bonded plate heat exchangers, such as dip-brazed, vacuum-brazed, and welded plate varieties, and they are often specified for closed-loop applications such as refrigeration . Plate heat exchangers also differ in the types of plates that are used, and in the configurations of those plates. Some plates may be stamped with "chevron", dimpled, or other patterns, where others may have machined fins and/or grooves. When compared to shell and tube exchangers,

4134-446: The heat exchanger. In single channels the configuration of the gaskets enables flow through. Thus, this allows the main and secondary media in counter-current flow. A gasket plate heat exchanger has a heat region from corrugated plates. The gasket function as seal between plates and they are located between frame and pressure plates. Fluid flows in a counter current direction throughout the heat exchanger. An efficient thermal performance

4212-471: The heat or absorb the heat required. A set of tubes is called the tube bundle and can be made up of several types of tubes: plain, longitudinally finned, etc. Shell and tube heat exchangers are typically used for high-pressure applications (with pressures greater than 30 bar and temperatures greater than 260 °C). This is because the shell and tube heat exchangers are robust due to their shape. Several thermal design features must be considered when designing

4290-405: The high product temperature for the shortest period possible, and to ensure that the temperature is evenly distributed throughout. Direct systems have the advantage that the product is held at a high temperature for a shorter period of time, thereby reducing the thermal damage for sensitive products such as milk. There are two groups of direct systems: In indirect systems, the product is heated by

4368-472: The main sources for sodium in the diet is processed foods. Sodium, mostly in the form of sodium chloride , i.e. salt, is added to prevent spoilage, add flavor and enhance the texture of these foods. Americans consume an average of 3436 milligrams of sodium per day, which is higher than the recommended limit of 2300 milligrams per day for healthy people, and more than twice the limit of 1500 milligrams per day for those at increased risk for heart disease. While it

4446-431: The medium and energy saving. After heating, the hot product is passed to a holding tube and then to a vacuum chamber , where it suddenly loses the temperature and vaporizes. The process, referred to as flash cooling , reduces the risk of thermal damage, inactivates thermophilic microbes due to abruptly falling temperatures, removes some or all of the excess water obtained through the contact with steam, and removes some of

4524-452: The milk. This reduces milk's tendency to form cream at the surface, and on contact with containers enhances its stability and makes it more palatable for consumers. UHT milk has seen large success in much of Europe, where across the continent seven out of ten people consume it regularly. In countries with a warmer climate such as Spain, UHT milk is preferred due to the high cost of refrigerated transportation and "inefficient cool cabinets". UHT

4602-455: The most heat from the heat (transfer) medium per unit mass due to the fact that the average temperature difference along any unit length is higher . See countercurrent exchange . In a cross-flow heat exchanger, the fluids travel roughly perpendicular to one another through the exchanger. For efficiency, heat exchangers are designed to maximize the surface area of the wall between the two fluids, while minimizing resistance to fluid flow through

4680-416: The need for refrigeration, and thus benefit the environment by reducing greenhouse gas emissions . The milk industry opposed this, however, and the proposition was abandoned. Ultra-high-temperature processing is performed in complex production plants, which perform several stages of food processing and packaging automatically and in succession: In the heating stage, the treated liquid is first pre-heated to

4758-570: The nuclear power plants called pressurized water reactors , special large heat exchangers pass heat from the primary (reactor plant) system to the secondary (steam plant) system, producing steam from water in the process. These are called steam generators . All fossil-fueled and nuclear power plants using steam-driven turbines have surface condensers to convert the exhaust steam from the turbines into condensate (water) for re-use. To conserve energy and cooling capacity in chemical and other plants, regenerative heat exchangers can transfer heat from

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4836-428: The other fluid flows outside the tubes, but inside the shell (shell side). Baffles are used to support the tubes, direct the fluid flow to the tubes in an approximately natural manner, and maximize the turbulence of the shell fluid. There are many various kinds of baffles, and the choice of baffle form, spacing, and geometry depends on the allowable flow rate of the drop in shell-side force, the need for tube support, and

4914-781: The perceived value of time to appeal to the postwar population, and this same appeal contributes to the success of convenience foods today. Benefits of food processing include toxin removal, preservation, easing marketing and distribution tasks, and increasing food consistency. In addition, it increases yearly availability of many foods, enables transportation of delicate perishable foods across long distances and makes many kinds of foods safe to eat by de-activating spoilage and pathogenic micro-organisms. Modern supermarkets would not exist without modern food processing techniques, and long voyages would not be possible. Processed foods are usually less susceptible to early spoilage than fresh foods and are better suited for long-distance transportation from

4992-626: The product and the package are sterilized separately and then combined and sealed in a sterile atmosphere, in contrast to canning, where product and package are first combined and then sterilized. In 1983, the UK Parliament passed the Importation of Milk Act 1983 , following a successful appeal to the European Court of Justice that prevented the government from banning the importation of UHT milk. In June 1993, Parmalat introduced its UHT milk to

5070-496: The resulting foods are used so widely. However, many forms of processing contribute to improved food safety and longer shelf life before the food spoils. Commercial food processing uses control systems such as hazard analysis and critical control points (HACCP) and failure mode and effects analysis (FMEA) to reduce the risk of harm. Secondary food processing is the everyday process of creating food from ingredients that are ready to use. Baking bread , regardless of whether it

5148-433: The same end. This configuration is preferable when the two fluids are intended to reach exactly the same temperature, as it reduces thermal stress and produces a more uniform rate of heat transfer. (b) Counter-flow, where hot and cold fluids enter opposite sides of the heat exchanger, flow in opposite directions, and exit at opposite ends. This configuration is preferable when the objective is to maximize heat transfer between

5226-515: The same until the advent of the Industrial Revolution . Examples of ready-meals also date back to before the preindustrial revolution, and include dishes such as Cornish pasty and Haggis . Both during ancient times and today in modern society these are considered processed foods. Modern food processing technology developed in the 19th and 20th centuries was developed in a large part to serve military needs. In 1809, Nicolas Appert invented

5304-491: The source to the consumer . When they were first introduced, some processed foods helped to alleviate food shortages and improved the overall nutrition of populations as it made many new foods available to the masses. Processing can also reduce the incidence of food-borne disease. Fresh materials, such as fresh produce and raw meats, are more likely to harbour pathogenic micro-organisms (e.g. Salmonella) capable of causing serious illnesses. The extremely varied modern diet

5382-493: The stacked-plate arrangement typically has lower volume and cost. Another difference between the two is that plate exchangers typically serve low to medium pressure fluids, compared to medium and high pressures of shell and tube. A third and important difference is that plate exchangers employ more countercurrent flow rather than cross current flow, which allows lower approach temperature differences, high temperature changes, and increased efficiencies. A third type of heat exchanger

5460-439: The system to operate at a lower temperature difference and reduce the weight of the equipment. Plate and fin heat exchangers are mostly used for low temperature services such as natural gas, helium and oxygen liquefaction plants, air separation plants and transport industries such as motor and aircraft engines . Advantages of plate and fin heat exchangers: Disadvantages of plate and fin heat exchangers: The usage of fins in

5538-444: The tube along the length of the fins, which are usually very thin. The main construction types of finned tube exchangers are: Stacked-fin or spiral-wound construction can be used for the tubes inside shell-and-tube heat exchangers when high efficiency thermal transfer to a gas is required. In electronics cooling, heat sinks , particularly those using heat pipes , can have a stacked-fin construction. A pillow plate heat exchanger

5616-568: The tubes in the shell and tube heat exchangers: There can be many variations on the shell and tube design. Typically, the ends of each tube are connected to plenums (sometimes called water boxes) through holes in tubesheets. The tubes may be straight or bent in the shape of a U, called U-tubes. Fixed tube liquid-cooled heat exchangers especially suitable for marine and harsh applications can be assembled with brass shells, copper tubes, brass baffles, and forged brass integral end hubs. (See: Copper in heat exchangers ). Another type of heat exchanger

5694-432: The turbine. Inside the tubes the cooling water runs in a parallel way, while steam moves in a vertical downward position from the wide opening at the top and travel through the tube. Furthermore, boilers are categorized as initial application of heat exchangers. The word steam generator was regularly used to describe a boiler unit where a hot liquid stream is the source of heat rather than the combustion products. Depending on

5772-403: The volatile compounds which negatively affect product quality. The cooling rate and quantity of water removed is determined by the level of vacuum, which must be carefully calibrated. Homogenization is part of the process specifically for milk. Homogenization is a mechanical treatment which results in a reduction of the size, and an increase in the number and total surface area, of fat globules in

5850-558: The wine, beer, and milk preservation. In the 20th century, World War II , the space race and the rising consumer society in developed countries contributed to the growth of food processing with such advances as spray drying , evaporation , juice concentrates, freeze drying and the introduction of artificial sweeteners, colouring agents, and such preservatives as sodium benzoate . In the late 20th century, products such as dried instant soups, reconstituted fruits and juices, and self cooking meals such as MRE food ration were developed. By

5928-494: Was first developed in the 1960s and became generally available for consumption in the 1970s. The heat used during the UHT process can cause Maillard browning and change the taste and smell of dairy products. An alternative process is flash pasteurization , in which the milk is heated to 72 °C (162 °F) for at least fifteen seconds. UHT milk packaged in a sterile container has a typical unrefrigerated shelf life of six to nine months. In contrast, flash-pasteurized milk has

6006-517: Was packaged in sterile cans. In the 1960s, APV launched the first commercial steam infusion system under the Palarisator brand name. In 1952, in Sweden, Tetra Pak launched tetrahedral paperboard cartons. They made a commercial breakthrough in the 1960s, after technological advances, combining carton assembling and aseptic packaging technologies, followed by international expansion. In aseptic processing,

6084-417: Was patented. However, without commercially available aseptic packaging systems to pack and store the product, such technology was not very useful in itself, and further development was stalled until the 1950s. In 1953, APV pioneered a steam injection technology, involving direct injection of steam through a specially designed nozzle which raises the product temperature instantly, under brand name Uperiser; milk

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