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© 2007 Institute of Food Technologists The Science of Food Speaker Name Speaker Title Date (optional) Speaker Name Speaker Title Date (optional)
© 2007 Institute of Food Technologists 2 What is Food Science? Food Science is the discipline in which biology, physical sciences, and engineering are used to study the nature of foods, the causes of their deterioration, and the principles underlying food processing.
© 2007 Institute of Food Technologists 3 What is Food Technology? Food Technology is the application of food science to the selection, preservation, processing, packaging, distribution, and use of safe, nutritious, and wholesome food.
© 2007 Institute of Food Technologists 4 What does a Food Scientist do? A Food Scientist studies the physical, microbiological, and chemical makeup of food. Depending on their area of specialization, Food Scientists may develop ways to process, preserve, package, or store food, according to industry and government specifications and regulations.
© 2007 Institute of Food Technologists 5 The science of food Food Chemistry is the study of: The composition of raw materials in foods The composition of the end-products of food production The changes which occur in food during its production, processing, storage and cooking Examples of the science of food in everyday life: Emulsions: Butter, ice cream, milk, mayonnaise Foams: Ice cream, marshmallows, whipped cream, meringue Gels: Gelatin desserts, Pimento’s in olives, pudding, gummy candies
© 2007 Institute of Food Technologists 6 Emulsions Oil and water don’t mix! But we are surrounded by foods that are made by mixing oil and water. Salad dressing, butter, ice cream, and milk are all oil-in-water mixtures that don’t separate under normal conditions. So how can we explain this? All of these foods are emulsions.
© 2007 Institute of Food Technologists 7 Emulsions An emulsion is a colloid in which liquids that do not normally mix are spread throughout each other. Emulsifying is done by slowly adding one ingredient to another while simultaneously mixing. This disperses and suspends tiny droplets of one liquid (known as the dispersed phase) through another (known as the continuous phase). A colloid is a mixture of very tiny particles that are dispersed in another substance but do not settle out of that substance Oil Water Dispersed Phase Continuous Phase
© 2007 Institute of Food Technologists 8 Emulsions To prevent the mixture from separating, an ingredient, known as an emulsifier, which is attracted to both oil and water, is added, thus allowing the two to mix. The emulsifier functions by surrounding the oil droplets to form a protective coat which holds the oil droplets in suspension. One part of the emulsifier molecule (the polar end) is soluble in water and one part is soluble in the oil (the non-polar end). Oil Non-polar end Polar end Water
© 2007 Institute of Food Technologists 9 Mayonnaise Mayonnaise is an example of an oil-in-vinegar emulsion. The basic ingredients in mayonnaise are: Large quantities of oil (dispersed phase) Small quantities of an acid (continuous phase), such as vinegar or lemon juice, and Egg yolk (the emulsifier) Other ingredients may be added for flavor
© 2007 Institute of Food Technologists 10 Mayonnaise The egg yolk is added because it contains lecithin (phosphatidyl choline), a naturally occurring emulsifier. The lecithin functions by surrounding the oil droplets to form a protective coat which holds the oil droplets in suspension. One part of the lecithin molecule (the polar end) is soluble in water and one part is soluble in the oil (the non-polar end). Since lecithin is attracted to both the oil and the water it prevents them from separating. Polar End Non-Polar End
© 2007 Institute of Food Technologists 11 Foams A foam is a type of colloidal dispersion in which very tiny particles of gas are dispersed (scattered) in a liquid or solid substance and do not settle out of that substance. Examples of foods that are considered foams include ice cream, whipped cream, foamed milk, marshmallows, and beaten egg white.
© 2007 Institute of Food Technologists 12 Foams A foam is made by agitating a liquid (by beating or mixing) which in turn traps air inside the liquid film. As air is trapped in the liquid the dispersion increases in volume. This increase in volume is known as overrun.
© 2007 Institute of Food Technologists 13 Egg White Foam Egg white foam is a type of foam used in meringues, soufflés, foamy omelets, angel food cake, and sponge cakes to make them light and porous (airy). An egg white foam is a colloid of bubbles of air surrounded by part of the egg white protein (albumen) that has been denatured during beating. Denaturation is the change of a protein’s shape under stress
© 2007 Institute of Food Technologists 14 Egg White Foam: Preparation To prepare an egg white foam, egg whites are initially beaten (with a wire wisk or electric mixer) until they become frothy. Then an acid (such as cream of tarter) and salt are added. These ingredients are not added at the beginning because they delay foam formation. The beating of the egg white foam then continues. The foam increases in volume and the air bubbles become smaller and more evenly distributed.
© 2007 Institute of Food Technologists 15 Egg White Foam: Preparation Several factors affect the formation and stability of egg white foams. These include: Fat: The addition of even a small amount of fat will interfere with the formation of a foam. Fat is present in the egg yolk so it is very important that all of the egg yolk is separated from the egg white prior to foam preparation. Salt: Salt is added to egg white foams for flavor. pH: Addition of an acid (such as cream of tarter) will decrease the pH of the egg white foam to near the isoelectric point of the egg white proteins. At the isoelectric point, the proteins are least stable and more sensitive to denaturation.
© 2007 Institute of Food Technologists 16 Egg White Foam: Preparation Several factors affect the formation and stability of egg white foams. These include: Temperature: An egg white foam is formed and reaches greater volume more quickly when egg whites are at room temperature rather than at refrigerator temperature. The stability of egg whites beaten at room temperature, however, is not as great as those beaten at colder temperatures. Sugar: Sugar is added during foam preparation because it creates a smooth, stable foam – one that will not collapse and drain quickly (i.e. syneresis will be delayed). Sugar is believed to contribute to the stability of the foam because of its ability to hold onto water that might escape from the foam. Sugar does, however, increase the beating time of an egg white foam because it delays the denaturation of the egg proteins.
© 2007 Institute of Food Technologists 17 Gels Gels are defined as more-or-less rigid colloidal systems In the case of gels, solid particles are dispersed in a liquid. The solid particles form a network structure which traps the liquid and gives the gel its shape. In food preparation, gels are often formed by the proteins of eggs or flour in such products as puddings, batters, and doughs. Gelatin, a type of protein found in the bone and skin tissue of animals, also forms gels. Some types of carbohydrates such as alginate, starch, and pectin, also form gels. A colloid is a mixture of very tiny particles that are dispersed in another substance but do not settle out of that substance
© 2007 Institute of Food Technologists 18 Alginate Gels Alginate is a type of polysaccharide that occurs naturally in all brown algae as a skeletal component of their cell walls. Alginate is used in food because it is a powerful thickening, stabilizing, and gel-forming agent. Some foods that may include alginate are ice cream, fruit-filled snacks, salad dressings, pudding, onion rings, and even the pimento strips that are stuffed into green olives. Ingredients: Olives, Water, Minced Pimento (Sodium Alginate, Guar Gum, Calcium Chloride), Salt, Lactic Acid.
© 2007 Institute of Food Technologists 19 Alginate Gels Most alginate used in foods is in the form of sodium alginate. In order to form a gel, sodium alginate needs to come into contact with divalent ions such as calcium (Ca 2+ ). As soon as sodium alginate (Figure 1) is added to a solution of calcium chloride a gel forms as the sodium ions (Na + ) are exchanged with calcium ions (Ca 2+ ) and the polymer becomes crosslinked (Figure 2). CO 2 - CO 2 - Figure 1. Alginate polymer in NaCl solution (no crosslinking) (Waldman et al. 1998) Na + Ca 2+ Figure 2. Alginate polymer in CaCl 2 solution (crosslinking) (Waldman et al. 1998)
© 2007 Institute of Food Technologists 20 Alginate Gels The calcium ions are able to crosslink the alginate polymers because they can form two bonds, as opposed to monovalent ions such as sodium which can only form one bond. The longer the alginate is in contact with the calcium chloride solution, the more rigid the gel will become, as more crosslinks are formed. Also, depending on the concentration of calcium ions, the gels are either thermoreversible (low concentrations) or not (high concentrations).
© 2007 Institute of Food Technologists 21 Alginate Gels Remeber the pimentos? Now, take a closer look at the ingredients… Ingredients: Olives, Water, Minced Pimento (Sodium Alginate, Guar Gum, Calcium Chloride), Salt, Lactic Acid.
© 2007 Institute of Food Technologists 22 Careers in Food Chemistry Job Titles: Food Chemist Scientist Employers: Food processors Ingredient manufacturers/suppliers Academia (Higher Education) Contract research laboratories/development firms Self-employed/Consultant Responsibilities: Analyze processing and packaging methods Study effect of processing on the appearance, taste, aroma, freshness, and vitamin content of the food Test samples to make sure foods meet food safety laws and experiment with new foods, additives, and preservatives Responsibilities: Analyze processing and packaging methods Study effect of processing on the appearance, taste, aroma, freshness, and vitamin content of the food Test samples to make sure foods meet food safety laws and experiment with new foods, additives, and preservatives
© 2007 Institute of Food Technologists 23 Careers in Product Development Job Titles: Product Development Scientist Scientist Employers: Food processors Ingredient manufacturers/suppliers Academia (Higher Education) Contract research laboratories/development firms Self-employed/Consultant Responsibilities: Bench-top development Testing Plant scale-up Commercialization Troubleshooting Responsibilities: Bench-top development Testing Plant scale-up Commercialization Troubleshooting
© 2007 Institute of Food Technologists 24 Want to learn more? Visit: http://www.ift.org http://school.discovery.com/foodscience/ Find a Food Scientist: A database of IFT members who are willing to provide more information about the field of food science to you http://members.ift.org/IFT/Education/TeacherResources/findafoodscientist.htm
© 2007 Institute of Food Technologists 25 Questions?
© 2007 Institute of Food Technologists 26 Activity I Second That Emulsion Baffling Beaters Alginate Gummies Photos courtesy of Peter Machado, University of Maryland
© 2007 Institute of Food Technologists 27 References Belitz HD and Grosch W. Food Chemistry. Berlin: Springer, 1999. Himich Feeland-Graves, J and Peckham, GC. Foundations of Food Preparation. 6th edition. Prentice Hall: Englewood Cliffs, NJ, 1996. Waldman AS, Schechinger L, Govindarajoo G, Nowick JS, and Pignolet LH. 1998. The Alginate Demonstration: Polymers, Food Science, and Ion Exchange. Journal of Chemical Education. 75(11): 1430-1431.
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