PHYSICAL METHODS OF FOOD PRESERVATION.pptx

This presentation includes the methods of food preservation by physical methods such as asepsis, preserve by low and high temperatures, biopreservatives, desiccation, controlled atmosphere and anaerobiosis

1. Food preservation – physical method Submitted By - M.J. AFRA , I – MSc M i crobiology , TBAKC

2. METHODS OF FOOD PRESERVATION Asepsis, or keeping out microorganisms Removal of microorganisms Maintenance of anaerobic conditions, e,g ., in a sealed, evacuated container Use of high temperatures Use of low temperatures Drying; this includes the tying up of water by solutes, hydrophilic colloids, etc Use of chemical preservatives, either developed by microorganisms or added Irradiation Mechanical destruction of microorganisms, e.g., by grinding, high pressures, etc. (not used industrially)

3. PRINCIPLES OF FOOD PRESERVATION Prevention or delay of microbial decomposition By keeping out microorganisms (asepsis) By removal of microorganisms, e.g., by filtration By hindering the growth and activity of microorganisms, e.g., by low temperatures, drying, anaerobic conditions, or chemicals d By killing the microorganisms, e.g., by heat or radiation Prevention or delay of self-decomposition of the food By destruction or inactivation of food enzymes, e.g., by blanching By prevention or delay of purely chemical reactions, e.g., prevention of oxidation by means of an antioxidant Prevention of damage because of insects, animals, mechanical causes, etc., a subject beyond the scope of this text

4. APPLICATIONS OF FOOD PRESERVATION By introducing as few spoilage organisms as possible, i.e., by reducing the amount of contamination; the fewer organisms present, the longer the lag phase. By avoiding the addition of actively growing organisms (from the logarithmic phase of growth). Such organisms might be growing on unclean containers, equipment, or utensils that come in contact with foods. By one or more unfavorable environmental conditions: unfavorable foods, moisture, temperature, pH, or O-R potential, or presence of inhibitors. The more unfavorable the conditions, the longer the delay of the initiation of growth By actual damage to organisms by processing methods such as heating or irradiation. Thus, for example, bacteria or their spores subjected to sublethal heat treatments have been found to require a better culture medium for growth than do the unheated organisms. Often a combination of methods for delaying the initiation of growth is enough to give a food the desired storage life.

5. METHODS OF FOOD PRESERVATION Physical Method Chemical Method

6. Physical method .

7. PHYSICAL METHODS Asepsis Preservation by drying Preservation by irradiation Preservation by low temperatures Preservation by high temperature

8. asepsis .

9. 1. ASEPSIS In nature there are numerous examples of asepsis, or keeping out microorganisms, as a preservative factor. The inner tissues of healthy plants and animals usually are free from microorganisms, and if any microorganisms are present, they are unlikely to initiate spoilage. If there is a protective covering about the food, microbial decomposition is delayed or prevented. Examples of such coverings are the shells of nuts, the skins of fruits and vegetables, the husks of ear corn, the shells of eggs, and the skin, membranes, or fat on meat or fish. It is only when the protective covering has been damaged or decomposition has spread from the outer surface that the inner tissues are subject to decomposition by microorganisms. Packaging of foods is a widely used application of asepsis. The covering may range from a loose carton or wrapping, which prevents primarily contamination during handling, to the hermetically sealed container of canned foods, which, if tight, protects the processed contents from contamination by microorganisms

10. REMOVAL OF MICROORGANISM For the most part the removal of microorganisms is not very effective in food preservation, but under special conditions it may be helpful. Removal may be accomplished by means of filtration, centrifugation (sedimentation or clarification), washing, or trimming.

11. CENTRIFUGATION Centrifugation, or sedimentation, generally is not very effective, in that some but not all of the microorganisms are removed. Sedimentation is used in the treatment of drinking water but is insufficient by itself. When centrifugation (clarification) is applied to milk, the main purpose is not to remove bacteria but to take out other suspended materials, although centrifugation at high speeds removes most of the spores.

12. WASHING Washing raw foods can be helpful in their preservation but may be harmful under some conditions. Washing cabbage heads or cucumbers before their fermentation into sauerkraut and pickles, respectively, removes most of the soil microorganisms on the surface and in this way increases the proportion of desirable lactic acid bacteria in the total flora. Washing fresh fruits and vegetables removes soil organisms that may be resistant to the heat process during the canning of these foods. Obviously the removal of organisms and of food for them from equipment coming into contact with foods, followed by a germicidal treatment of the apparatus, is an essential and effective procedure during the handling of all kinds of foods. Washing foods may be dangerous if the water adds spoilage organisms or increases the moisture so that growth of spoilage organisms is encouraged.

13. TRIMMING Trimming away spoiled portions of a food or discarding spoiled samples is important from the standpoint of food laws and may be helpful in food preservation. Although large numbers of spoilage organisms are removed in this way, heavy contamination of the remaining food may take place. Trimming the outer leaves of cabbage heads is recommended for the manufacture of sauerkraut.

14. DRYING Microorganisms require water to grow. If exposed to sunlight or exposed to dehydration the moisture present in the food is eliminated and the amount of water is reduced to a predetermined amount. This stops development of microorganisms, and thus causing food spoilage. Drying food is among the oldest methods used from early times. This process involves exposure of food items to the sun and air until the food is dry. It’s an extremely efficient and cost-effective method. Drying and dehydration and ‘dehydration’ refer to the process of removing water. Drying is the process of removing moisture through the use of alternative energy sources such as wind and sun. Dehydration is the process of removing moisture through the application of artificial heat in controlled conditions of humidity, temperature as well as airflow

15. TREATMENT OF FOODS BEFORE DRYING Selection and sorting based on size, maturity, and overall health Cleaning, particularly fruits and vegetables Peeling fruits and vegetables with a hand, machine, or knife Subdivide into halves, shreds, slices or cubes. Scalding or blanching of vegetable and certain fruits, such as peaches and tomatoes The sulphuration of light colored fruits and vegetables through exposure to sul-phur di-oxide gas

16. TYPES OF DRYING Sun Drying Sun-drying absorbs sunlight’s heat, but it’s a lengthy process that is prone to spoilage and contamination. The problem with sun drying is the availability of a climate that has a hot sun and dry climate Mechanical / Artificial Drying Artificial drying is the process of passing of hot air and controlled moisture over food items that is to be dried , or the passing of food items through the air. SPRAY DRYING:  Eggs and milk are dried into a powder in spray dryers where it is then atomized before being sprays into steaming hot air or fast drying. FOAM MAT DRYING:  foam mat drying can be commercially used to preserve tomato and orange juice. In this method, a tiny portion of the edible sta-bilizer employed. The foam is then spread into thin layers and then dried in a hot steam of air. The product is separated into tiny particles upon cooling. DRYING VIA OSMOSIS :  osmo-sis occurs when the fish is salted heavily. In this instance the moisture is drained away from all cells. The water then bonds to the solute, making it unobtainable to microorganisms. In the process of osmotic dehydration, which is a method of this method involves partial dehydration of fruits via osmosis in sugar solution that is concen-trated or a syrup. FREEZE DRYING:  Freeze drying is the process of removing water from frozen products by sublimation is referred to as freeze drying. Foods that are freeze dried are of high-quality with a soft and porous texture

17. filtration Filtration is the only successful method for the complete removal of organisms, and its use is limited to clear liquids. The liquid is filtered through a previously sterilized “ bacteriaproof ” filter made of sintered glass, diatomaceous earth, unglazed porcelain, membrane pads, or similar material, and the liquid is forced through by positive or negative pressure. This method has been used successfully with fruit juices, beer, soft drinks, wine, and water. The three main filtration stages are pre-filtration, fine filtration and sterile filtration PRE-FILTRATION – It refers to the removal of unwanted large particles FINE FILTRATION – It refers to the use of pleated filter catridge with a filtration accuracy of 1 to 33 microns according to the beverage composition STERILE FILTRATION – Final filtration step before bottling to clarify the beverages and remove residual yeasts and microbial contamination

18. radiation The aim of irradiation to kill microorganisms and deactivate enzymes, without altering the nutritional content of the food. Food irradiation is a low temperature sterilizing process. In this instance, sterilization can be accomplished at the temperature of room. The food we eat is exposed to extremely high energy radiation known as gamma rays, or electrons that are fast moving, killing insects,  fungi  and bacteria. In some instances radiation delays the ripening process of fruits. The main benefit of Irradiation is that it is able to be carried out after food is sealed and packaged. It has been utilized in pasteurizing or sterilizing perishable food items like fish, meat as well as fruits, and prolonging their shelf life for lengthy durations. It can also be used for inhibiting the sprouting process in potatoes, onions, etc. Cobalt-60 or Cesium-137 , also known as electrons-producing machines are primary sources of ionizing radiations employed for food irradiation.

19. Preserving food by low temperature .

20. 2. Preservation by low temperature The metabolism of living tissue is determined by the temperature in the environment. Low temperatures are used to slow down chemical and enzymatic reactions that occur in food products. Furthermore, lowering the temperature slows or stops the development as well as activity of microorganisms within the food. The lower temperatures, the lower is the rate over natural activity. Cooling slows or prevents the degradation of food. The use of refrigeration and freezing is among the most ancient ways for preservation. Mechanical ammonia refrigeration systems developed in 1875 enabled the development of commercial refrigerated warehouses and freezing

21. Methods of low temperature CELLAR STORAGE TEMPERATURE (15°C):  Cellar storage temperature (15degC) is typically used for storage of food surpluses such as potato, root crops, apples, onions etc. for a limited time. REFRIGERATION/ CHILLING TEMPERATURE (0 to 5°C):   Foods stored at this temperature reduce the activity of microbial organisms and chemical changes that cause the spoilage. Refrigeration or cold storage that is mechanical is used to accomplish this. Examples include: eggs, meats, poultry fish fresh milk, dairy products fruit, vegetables, and so on. which can be kept for 2-7 days in refrigeration. 

22. Methods of low temperature 3) FREEZING FOOD PRESERVATION (-18 to -40°C):    When food is frozen, the water contained in food is transformed into the form of ice, which makes the food inaccessible for reactions to take place as well as for microorganisms and microbes to flourish. Most perishable foods like poultry, meats, fish, ice-creams, peas, vegetables, juice concentrates, etc. can be stored for several months in this climate. In vegetable products, enzymes could still cause negative effects on flavor and texture when frozen. Blanching and heating will, in turn, remove the enzymes before vegetables are frozen

23. Preserving food by high temperature .

24. 3. Preservation by high temperatures Heating was practiced for centuries before the mechanism was fully recognized. Food items are heated up or cooked. It is used to deactivate the organisms or enzymes that have a importance to spoilage in food items. Microorganisms are killed with heat, because the  heat’s application coagulates the proteins  in food and activates the enzymes that kill microorganisms, which leads to the destruction of microorganisms. Examples include all kinds of food cooked such as pasteurization, sterilization of milk with UHT (ultra high temperatures) as well as canning. The most crucial current applications of preservation of heat is  pasteurization of milk

25. Methods of high temperature PASTEURIZATION (TEMPERATURE BELOW 100°C) Pasteurization is a method of heat treatment using temperatures of less than 100degC which kills a small portion but not all microorganisms found in food. Milk, for instance, is typically heated to 63 degrees Celsius for 30 minutes or 71degC for 15 secs or UHT 138degC over 4 to 5 seconds. Examples include wine, milk beer, fruit juices and aerated water which are often pasteurized. The heating method can be hot water, steam dry heat, as well as electric energy. The products are quickly cooled following heating. Pasteurization is typically accompanied with other methods to extend the shelf-life of food product

26. Methods of high temperature METHODS OF PASTEURIZATION BOTTLE OR HOLDING PASTEURIZATION:   This technique is widely used to preserve fruit juices. The juice that is extracted is separated and then placed in bottles. The bottles are then sealed to keep them air tight and then pasteurized. OVER FLOW METHOD:   The juice is heated to approximately 2.5oC greater than the temperature of pasteurization and filled into hot sterilized bottles. The bottles that are sealed are sterilized at temperatures 2.5oC lower than the filling sealing temperature, and then chilled.

27. Methods of high temperature 2. BOILING (TEMPERATURE AT 100°C) The preparation of rice, veggies and meats, fish, etc. at home is typically accomplished through boiling food in water. It is done at an oven that is heated to about 100degC.

28. Methods of high temperature 3. CANNING (TEMPERATURE ABOVE 100°C) Canning is the method by which food items are cooked in sealed (airtight) cans or jars to a temperature which destroys microorganisms as well as inactivates enzymes that can pose dangerous to health or cause food to get spoiled. Tin-coated steel containers are frequently used. They are followed by glass containers. Today, containers made of aluminum and plastics, in the form of rigid containers or pouches are becoming more popular. Some examples of food that is preserved through canning are: all kinds of canned foods including soup meat cereal grains, beans legumes, nuts, and different dried food items such as coffee, fruits milk, soups meat, fish and vegetables.

29. Methods of high temperature Steps of canning involves Cleaning Blanching Filling Exhausting Sealing Sterilization Cooling Labelling

30. Methods of high temperature BLANCHING Blanching is a process of heating similar to pasteurization. This is accomplished by submerging the product under boiling hot water for 2 to 3 minutes at temperatures ranging from 180degF to 190degF. Blanching is focused on deaerating the product as well as activating enzymes that degrade before proceeding with process. Blanching is a crucial process to freeze food, because frozen food can take on flavors , loss of vitamins and changes in colour during storage. ADVANTAGES OF BLANCHING Stops the  growth of bacterial . Enhances vegetable’s natural color and keeps the color . The product shrinks, which is better to fill the container

31. desiccation .

32. 4.desiccation Desiccation is the state of extreme dryness, or the process of extreme drying. In biology and ecology, desiccation refers to the drying out of a living organism. Microorganisms cannot grow and divide when desiccated, but can survive for certain periods of time, depending on their features. After the addition of water, the bacteria will start growing again, so desiccation does not provide complete sterilization. Some bacteria, such as  Deinococcus radiodurans   and  Mycobacterium   ,  are extremely resistant to damage from prolonged desiccation while others, such as  Neisseria gonorrhoeae,  can survive only short periods of desiccation. Freeze-drying is performed using special equipment. Two components are common to all types of freeze-dryers: a vacuum pump to reduce the ambient gas pressure in a vessel containing the substance to be dried, and a condenser to remove the moisture by condensation on a surface cooled to −40º to −80ºC. Pharmaceutical companies often use freeze-drying as a desiccation tool to increase the shelf life of products, such as vaccines and other injectables. By removing the water from the material and sealing the material in a vial, the material can be easily stored, shipped, and later reconstituted to its original form. Preservation is possible because the greatly reduced water content inhibits the action of microorganisms and enzymes that would normally spoil or degrade the substance. Another example from the pharmaceutical industry is the use of freeze-drying to produce tablets or wafers.

33. anaerobiosis .

34. 5.anaerobiosis Anaerobic conditions can be established by removing or expelling air or oxygen from the given package and replacing the air with an inert gas such as CO₂ or nitrogen. The reduction of oxygen under these conditions impedes the growth of surviving bacteria as well as their spores. The reproduction of CO₂ at the time of fermentation as well as its accumulation on the surface area, makes the condition anaerobic to impede aerobic growth. Carbonation of beverages and storage of a controlled atmosphere of fresh food serve the exact purpose. Jam, where food is closed after the air is removed (suction), demonstrates this principle. However, anaerobic bacteria, as well as their spores, must be decapitated to prevent food spoilage. Oiling food prevents contact with the air and prevents the growth of microorganisms such as mould and yeast.

35. Controlled atmosphere .

36. 6.Controlled atmosphere A controlled atmosphere is an agricultural storage method in which the concentrations of oxygen, carbon dioxide and nitrogen, as well as the temperature and humidity of a storage room are regulated. Both dry commodities and fresh fruit and vegetables can be stored in controlled atmospheres. Controlled Atmosphere Storage is effective because the low temperatures involved in freezing food kill and prevent the growth of bacteria and other microorganisms and help to reduce nutrient loss. Drying foods can also achieve bacterial growth inhibition by removing moisture from the food which in turn slows down the enzyme activity. As well as the freezing or drying process maximizing the quality of the produce, the relative ratios of different atmospheric gases and humidity is also crucial during the storage of preserved foods. For dried products such as flour or cereals, storage of the food in specific, controlled mixture of gases, can extend shelf life by up to three times by inhibiting chemical reactions that lead to degradation and spoilage.

37. biopreservatives .

38. 7.biopreservatives Biopreservation  is the use of natural or controlled macrobiotics or antimicrobials as a way of preserving food and extending product shelf life. Desirable bacteria or the fermentation products produced by these bacteria are used in biopreservation to control spoilage and to inactivate pathogens in food. Nowadays, in the dairy industry and other industries involved in the production of fermented foods such as meat, spirits, vegetable products, and juices using starter culture to initiate the process of fermentation during food production. The microorganism used is selected depending on food type with the aim (providing attractive flavour properties for the consumer) and it must fulfil the standards of GRAS status. It is expected that a starter culture should have both the metabolic and antimicrobial qualities.

39. biopreservatives BACTERIOCINS Bacteriocins are ribosomally synthesized proteinaceous substances or antimicrobial peptides produced by bacterial strains which usually inhibit the growth of either closely related or similarly related bacterial species. They inhibit the growthof their target organism by attacking their cell envelope or by affecting their gene expression and protein productionin the cell Bacteriocins are generally considered to be more natural as they are believed to have been present in foods consumed since the olden times

40. biopreservatives ENZYMES Enzymes and other polypeptides with antimicrobial properties occur in animals, as well as in plants. Lytic enzyme lysozyme present in the hen’s egg is effective against several spoiling causing bacteria and foodborne pathogens. Studies indicate that the egg white enzyme effectively lyses and inhibits the growth of certain strains of L. monocytogenes thermophilic clostridia, C. botulinum. Lysozyme is attractive as a preservative due to its safe nature and its specific antibacterial activity. It is also used in certain hard cheeses to prevent the formation of gas and to prevent the cracking of the cheese wheels due to saccharolytic, butyric-forming clostridia, specifically Clostridium tyrobutyricum

41. biopreservatives SPICES AND HERBS Spices and herbs have been used in food since the dawn of agriculture. They are normally used in every household to flavor , season, provide health benefits, and improve the taste of foods in general. But they also play an important role in food preservation due to their strong preservative qualities. Garlic (Allium sativum), a well-known medicinal plant, has numerous benefits and it is proven to have antimicrobial properties. A study done to demonstrate the preservative effects of garlic concluded that it can effectively decrease microbial activity and extend the shelf life of fresh fish (Nile tilapia) for 3 days under suitable storage conditions. It also effectively deterred the emergence and development of maggots on the fish carcass.

42. biopreservatives YEAST Yeast are also known to have a bio preservative effect on food due to their competitive nature and antagonistic activities. The antagonistic activities are attributed mainly to pH alterations in the medium, competition for nutrients, tolerance of high ethanol concentrations, and the production of antimicrobial compounds called killer toxins also known as “mycotoxins” which are highly effective against the growth of foodborne pathogens and spoilage causing microorganisms in food.

43. biopreservatives LACTOFERRIN Lactoferrin ( Lf ), is an iron-carrying protein (glycoprotein) belonging to the family of transferrin with a molecular weight of about 80 KDa with several physiological properties. It plays an important role in the clinical industry due to its anticancer, antifungal, antimicrobial, and anti-inflammatory properties. CHITOSAN Chitosan, is a biopolymer derived from the exoskeleton of shellfish such as lobster, crab, and shrimp. It possesses certain antimicrobial properties and other beneficial qualities. It also recently garnered attention for being biodegradable, biocompatible, and non-toxic by nature. chitosan plays a fairly important role in the pharmaceutical industry due to its therapeutic qualities

44. Thank you M.J. AFRA