Chapter 1 Food Processing.pptx

svbf

1. History and Trends of Food Preservation & Processing

2. Activity Why does fresh bread go bad? Why do fresh donuts go bad? Why do packaged bread or donuts not go bad?

3. Food Processing Techniques used to slow deterioration and allow people to enjoy foods in a variety of forms around the year and around the globe. Process of turning raw agricultural product into attractive and consumable food.

4. Food Preservation Methods of treating foods to delay the deterioration of the food. Changing raw products into more stable forms that can be stored for longer periods of time. Allows any food to be available any time of the year in any area of the world.

5. Historical Methods of Food Preservation Primitive and tedious methods Drying Salting Sugaring Pickling Cold storage

6. Drying Oldest form of food preservation. Methods Sun drying Hot air drying – mechanical dehydrator Fluidized-bed drying Drum drying – milk, fruit, veg. juices, cereals Spray drying – milk, eggs, coffee, syrups Freeze drying - Puff drying – Fruit or vegetable juices

7. Drying Used to preserve fruit, vegetables, meats, and fish. Mainly used in the south – warmer climate. Causes the loss of many natural vitamins.

8. Salting Used extensively for pork, beef, and fish. Costly due to high price of salt. Done mainly in cool weather followed by smoking.

9. Sugaring Used to preserve fruits for the winter. Jams and jellies. Expensive because sugar was scarce commodity in early times.

10. Pickling Fermenting Used to preserve vegetables. Use mild salt and vinegar brine. Increases the salt content and reduces the vitamin content of the food. Oldest form of food preservation.

11. Cold Storage Used extensively in the northern U.S. Root cellars were used to store vegetables at 30-40 degrees F. Root cellars were replaced by ice boxes in the mid 1800’s.

12. Refrigeration Early time, ice and snow was used. Now the most popular method of food preservation. 85% of all foods are refrigerated. Greatly changed our eating habits.

13. Refrigeration 13 Refrigerators should be set to below 4°C to control the growth of micro-organisms in foods. This lowered temperature also reduces the respiration rate of fruits and vegetables, which retards reactions that promote spoilage. 

14. Refrigeration is generally used to: reduce spoilage during distribution of perishable foods; increase the holding period between harvesting and processing; and extend the storage life of commercially processed foods. Not all foods benefit from cold temperatures. For example, bananas turn black and bread goes stale when refrigerate d 14

15. However, if foods are continuously exposed to warmer temperatures, such as the opening and closing of freezer doors, then heat shock occurs. Heat shock is when ice melts and re-forms into larger ice crystals. The best example is ice cream, which has a gritty texture if large ice crystals have developed .

16. What is the importance of food processing to human health? increases variety increases convenience improves quality of food

17. What are five common food-processing methods? Fermentation - Production of CO2 through anaerobic respiration, also produces lactic acid alcohol in the process. Canning - Sterilize food by getting it to a temperature of 212-250 F, then putting it into airtight containers Dehydration - Lowers moisture content to inhibit growth of microorganisms Irradiation - Uses gamma rays to kill insects, bacteria, fungi, etc. in food products. Blanching - Briefly scald food to inactivate enzymes that cause undesirable changes.

18. Method- Fermentation Advantages Improves taste Adds value to crops, such as cucumber Disadvantages Rather lengthy process in comparison to other food processing techniques.

19. Heating Started in 1800’s. Known as canning – putting hot food in jars to seal. Food is cooked to extremely high temperatures, put into jars and lids are placed on them. Lids are sealed from the heat and this prevents bacteria from growing and spoiling the food.

20. Method- Canning Advantages Increases shelf life 2 years is considered normal shelf life Disadvantages Weight of product Requires specially treated metal cans or appropriate glass jars.

21. Method-Dehydration Advantages Increases shelf life up to 2 years Lighter weight Lower volume Disadvantages Changes taste and texture of food Typically requires preparation to reconstitute food.

22. Method-Irradiation Advantage Gamma rays pass through without heating or changing it, therefore no heat sensitive nutrients are lost in the process Disadvantages High cost Perception of irradiation

23. Irradiation is generally used for: prevent sprouting in potatoes and onions; control insect infestation of wheat flour and reduce the microbial load of ground spices. 23

24. If irradiation becomes more widespread among various other food products, it is expected to replace fumigation, ensure hygienic quality and reduce the dependence on refrigeration.

25. Blanching Used for vegetables. Heat the food with steam or hot water to 180-190 degrees F. This prevents bacteria from growing. Hot food is cooled in ice water.

26. Benefits of Blanching Shrinks the product, better for filling the container. Destroys enzymes in the food. Fixes the natural color of vegetables – holds their color.

27. Method-Blanching Advantage Improves taste Increases availability of out of season foods Disadvantage Storage limits Fruits & veggies 1 year Meat 3-6 months Freezing temperatures required for storage

28. Vacuum Packaging Removes oxygen. Oxygen reacts with food causing undesirable changes in color and flavor.

29. Chemicals Salt was first chemical used to preserve foods. NaCl – salt; makes water unavailable to microorganisms. Changes the pH of the food not allowing microorganisms to live.

30. Chemical Additives sodium nitrate fatty acids sulfur dioxide sorbic acid diethyl pyrocarbonate oxidizing agents benzoates antibiotics antioxidants

31. Salt Oldest known food additive. Used in meats, cheeses, bread. Americans consume 10-12 grams per day; 10 pounds per year. Prevents spoilage.

32. Salt 3 basic properties Flavor Protein extraction Microbial control

33. Sterilization 33 It destroys all pathogenic and spoilage micro-organisms in foods and inactivates enzymes by heating. All canned foods are sterilized in a retort (a large pressure cooker). This process enables food to have a shelf life of more than two years.

34. Pasteurization 34 It is the process of heating a food-usually a liquid-to or below its boiling point for a defined period of time. The purpose is to destroy all pathogens, reduce the number of bacteria, inactivate enzymes and extend the shelf life of a food product. 

35. Foods with a pH of less than 4.6, such as milk and spaghetti sauce, can be pasteurized.  Permanent stability-that is, shelf life of about two years-is obtained with foods that can withstand prolonged heating, such as bottled juices.  35

36. There is a greater loss of flavour from foods that are exposed to a longer time-temperature relationship. Therefore, temporary stability (that is, limited shelf life) is only obtained with some foods where prolonged heating would destroy its quality. These foods, such as milk, usually require subsequent refrigeration.  36

37. "High temperature short time" (HTST) and "ultra high temperature" (UHT) processes have been developed to retain a food's texture and flavour quality parameters. 37

38. Microwaving 38 Microwave ovens are rarely used for processing large quantities of food. They are mainly of interest when the products such as frozen foods are used..  Microwave ovens use electromagnetic radiation to excite water molecules in food. The actual waves penetrate only about 10 inches from the source of the radiation. Within the food, the waves only penetrate 3�4 to 1 inch on all sides. As a result, the actual ovens must be limited in size. Heat is produced within the food by the friction of water molecules, which spreads to the centre of the food by conduction. 

39. Small portions are cooked rapidly in microwave ovens. As the quantity of food increases, however, the efficiency is lost. 39

40. Frying 40 It involves cooking in hot oil. Because of the big difference between the temperature of the oil and the food, as well as the small size of the food pieces, cooking is completed in a relatively short time-anywhere from 20 seconds to six minutes.  Fried foods are known for their characteristic crispy outer surface as well as their high fat content.

41. The fat that is absorbed by the food product varies from 10 percent to 40 percent, depending on the time the food is immersed in the oil. Continuous fryers are often used in the food industry. 41

42. Evaporation 42 It is the partial removal of water from liquid foods by boiling. When the operation is done under vacuum, boiling is avoided and the food's flavour qualities are retained.  Some of the foods that have undergone evaporation are evaporated milk, tomato paste and juice concentrates.

43. This process is carried out for three main reasons: to reduce the weight and, therefore, reduce storage and transport costs; to preserve foods by decreasing the water activity and increasing the solids content; and to provide consumers with convenient foods. 43

44. Dehydration 44 Dehydration-or drying-is the nearly complete removal of water from solid foods. One of the oldest methods of food preservation, it was traditionally carried out by the sun.   This application is used for the same reasons that liquid foods undergo evaporation-preservation, convenience and cost savings. Dried soup mixes, dried fruit, powdered milk and spices are just a few examples of dehydrated foods.

45. Spray drying and freeze drying are two drying methods used widely today. Spray drying is when a liquid food is atomized into a fine, dry powder . Examples include natural and artificial flavours and milk powders. Freeze drying involves first freezing the food and then driving off the ice, leaving a high quality, porous dried food such as instant coffee. 45

46. Emulsions 46 An emulsion is a system containing two liquid phases that don't mix, where one phase (disperse phase) is distributed throughout the other phase (continuous phase) in the form of very small droplets.

47. Generally there are two types of emulsions: oil in water (O/W) water in oil (W/O) An example of an O/W emulsion is salad dressing, and an example of a W/O emulsion is butter.

48. Homogenization 48 It is used to stabilize an emulsion. More specifically, it is the reduction in size and the increase in number of droplets of the dispersed phase by the application of intense shearing forces.  Generally, it is applied to change the functional properties or improve the texture of emulsions. For example, most fluid milk sold at the retail level is homogenized to improve its stability, and most caramel fillings are homogenized to increase their smoothness

49. Extrusion 49 Extrusion is the process in which a food is compressed and worked to form a semi-solid mass. This mass is then forced through a restricted opening, or die, to create a desired texture or shape. The purpose of this application is simply to provide a greater variety of textured foods to consumers.  Food may also be cooked while extruded. This is referrred to as extrustion cooking or hot extrusion. Some extruded food products are licorice, puffed wheat and cornflakes.

50. Hurdle or Combination Processing 50 Hurdle technology is a concept that was developed to address the consumer demand for more natural, fresh-like foods. It is a way for food processors to employ only mild preservation techniques to their food products.   The idea is to use deliberate low-level combinations of existing and novel preservation techniques ("hurdles") to eliminate the growth of micro-organisms. Lower-intensity individual methods can be used because of the collective effect of the combined methods .

51. Some of the more common hurdles include: pasteurization; water activity (aw); salt; blanching; freezing; modified atmosphere packaging (MAP); pH; preservatives; refrigeration; and irradiation. 51

52. Some micro-organisms present will be able to survive the individual treatments applied. However, no microorganism will be able to overcome all of the combined hurdles. Thus the food is stable and safe.  The only way to ensure that the correct combination of hurdle technologies is used is to make sure that a qualified resource conducts quality and safety shelf-life studies. 52

53. Examples of hurdle processing can be found in traditional and recently developed foods, such as yogurt and prepackaged fresh salads. The hurdles employed in yogurt manufacture include low temperatures, high acid and competitive microbial flora. Those used to prepare prepackaged fresh salads include low temperatures and modified atmospheres. 53