Presentation on theme: "INTRODUCTION TO FOOD SCIENCE II 1204"— Presentation transcript:
1 INTRODUCTION TO FOOD SCIENCE II 1204 Luke Howard, PhDProfessorDepartment of Food ScienceUniversity of Arkansas
2 IntroductionThis module is an abbreviated version of the freshman college course entitled “Introduction to Food Science; 1103” using the notes of Dr Luke Howard and narration by Steve SeidemanIt briefly covers the area of food science from the chemistry of foods, nutrition, regulations, microbiology, packaging, quality, processing and biotechnology.
3 Food ChemistryFood is composed of biochemicals -chemicals related to life.These may come from both plant and animal sources.The 5 main classes of food chemicals include; water, carbohydrates, protein, lipids and vitamins/ minerals.
4 WaterWater is by far the most abundant of the classes representing 75% of the earths surface.Water is also the most abundant class of chemicals found in food.It is considered “the universal solvent” since most other classes of food chemicals are dissolved in it.
5 Carbohydrates Carbohydrates are hydrates of carbon atoms. The chemical formula is a multiple of Cx(H2O)y.
6 Types of Carbohydrates SugarsDextrinsStarchesCelluloseHemicellulosePectinsGums
7 Categories of Carbohydrates Monosaccharides (C6H12O6). There are a large variety of monosaccharides based on hydroxyl (OH) configurations. Glucose is the most common.Disaccharides- These are 2 monosaccharides joined in a “glycosidic linkage”. Examples are sucrose, maltose and lactoseReducing sugars- All monosaccharides and some disaccharides which can react with amino acids from proteins to cause colors and flavors in foods. This is called the Malliard Reaction.
8 Categories of Carbohydrates Polysaccharides- These are long chains of sugar molecules (glucose)Amylose-straight chain polysaccharide (1-4 bonds)Amylopectin-branched chains with mostly1-4 bonds and some 1-6 bonds.Dextrin-Intermediate length linear chains
9 A glucose molecule written out in 2 formats A glucose molecule written out in 2 formats. Glucose is the simplest of all carbohydrates..
10 Sucrose (table sugar) and lactose (milk sugar) are simply 2 glucose molecules differing in the linkage between the 2 glucose molecules.
11 Amylopectin is a long, branched chain made of glucose molecules.
12 Properties of Sugars Add sweetness Soluble in water Crystalline structureSource of energyPrevent microbial growth in high concentrationsBrown when heatedAdds body and mouthfeel to foodsPart of the browning (Malliard) reactionFermentable
13 Properties of Starches Not sweet to tasteNot soluble in cold waterForms pastes and gels in hot waterSource of energyHave a granulated structure
14 Proteins Proteins are made of chains of amino acids. They contain an “amine” (NH2) group on one side.Proteins comprise most of our skin, hair, cartilage, nails and musclesThere are 20 amino acids used by our bodies. Eight of them are essential meaning we cannot synthesize them in our bodies. Must be obtained from external sources (e.g. eating).Protein structures are linear, coiled or as globules.
15 ProteinsProteins undergo one major alteration that being denaturation. Denaturation is when the protein changes its “native state” which is usually irreversible.Denaturation can be caused by heat, chemicals, excessive stirring and acid/alkali conditions.Examples would include cooking meat or eggs (heat coagulates the protein meaning the protein is denatured).
16 These are the 20 amino acids used to make up proteins.
17 These are some of the common amino acids These are some of the common amino acids. Glycine is the simplest of all amino acids.
18 Lipids Lipids are food components also known as fats and oils. Fats are solid at room temperature because they have no double bonds.Oils are liquid at room temperature because they contain at least one double bond.Sources of lipids include milk fat, vegetable oils, oil seeds and animal fatsLipids are smooth and greasy so they provide for a smooth mouthfeel. That is why good foods are high in fat.
19 Lipids Lipids are composed of fatty acids. Fatty acids are long chains of carbon atoms with an organic acid end group (carboxyl group- COOH).There are a number of fatty acids and their name is often determined by the number of carbons in the chain.
20 Some common fatty acids Some common fatty acids. The number of carbons and number of double bonds is on the left. The common name is on the right.
21 Some Common Saturated Fatty Acids Acetic CH3COOHPropionic CH3CH2COOHCaproicCH3 (CH2)4COOHCapricCH3(CH2)8COOHLauricCH3(CH2)10COOHPalmiticCH3(CH2)14COOHStearicCH3(CH2)16COOHArachinicCH3(CH2)18COOHRead the slide
22 Some Common Unsaturated Fatty Acids Oleic CH3(CH2)5CH=CH(CH2)7COOHLinoleicCH3(CH2)4CH=CHCH2CH=CH(CH2)7COOHLinolenicCH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOHArachidonicCH3(CH2)4CH=CHCH2CH=CHCH2CH=CHCH2CH=CH(CH2)3COOHRead the slide
23 Lipids Fatty acids can be either Cis or Trans. Cis –Chains are attached to the same side of the double bond. These are natural occurring.Trans-Chains are attached to the opposite sides of the bond.
25 TriglyceridesA triglyceride consists of 3 fatty acids bonded to a glycerol backbone.Sometime only one or two fatty acids are bonded to a glycerol molecule and are called monoglycerides or diglycerides, respectively.
26 This is an example of a triglyceride This is an example of a triglyceride. Note the 3 fatty acids off a glycerol backbone.
27 LipidsIn organic chemistry, compounds may be classified as either polar or non-polar.Whether a compound is polar or non-polar is dependent on their end group.Polar means they are soluble in water and some alcohols.Non-polar means typically soluble in other organic solvents ( hexane, benzene) and some alcohols.
28 LipidsAs a rule of thumb, if a group of compounds has a low molecular weight and has a hydroxyl group (OH), it is polar.Sugars are polarProteins are mostly non-polarFats are have both polar and non-polar ends
29 Lipids Lipids are subject to oxidation. This is essentially a free radical (an electron) moving about that causes oxidative damage resulting in off flavors and odors also referred to as rancidity.It is a chain reaction that is very difficult to stop.
30 Lipid Oxidation Lipid oxidation can be influenced by; Oxygen concentrationLightMetals –FeUnsaturated fatty acids in lipidFree fatty acidsTemperature-heat makes lipids more susceptibleSurface areaMoisture content
31 VitaminsVitamins are classified as either water soluble or fat soluble.Food processing (heat, stirring, time etc) is detrimental to the vitamin content of food.Many foods are now fortified or enriched.* Many B vitamins in bread to preventpellagra.*Vitamin D fortified milk to preventrickettes
32 VITAMINS Water soluble Vitamins; Ascorbic acid-from fruit sources Thiamine (B1)- from vegetables, fruit &grainRiboflavin (B2)- very stable to processingNiacinB6Folic acidB12 –from animal sources
37 NutritionWe should eat from all these sources each day since no single food can supply all of the needed nutrients.Carbohydrates from grains, vegetables, fruits and dairyProteins from grains, dairy and protein groupsFat from dairy and protein groupsVitamins and minerals from all groups.
38 Nutrition Food is the only source of energy for humans. Energy in foods is measured in calories.A calorie is the amount of heat required to raise the temperature of one gram of water one degree celsius (C).Kilocalorie is 1000 caloriesThe energy content of foods is measured in a calorimeter where the food is basically burned and the heat generated is measured and converted to calories.
39 Nutrition Energy From Food Constituents; Carbohydrates= 4 kcal/gram Protein= 4 kcal per gramLipids/fat=9 kcal/ gramBased on the RDA diet, lipids supply 30% of our energy needs, carbohydrates supply 60%. Protein supplies the remaining 10%.
41 Why are Food Regulated? To ensure safety and wholesomeness To prevent fraud and deceptionTo inform consumers about nutritional content of foods
42 U.S. Regulatory Agencies Food and Drug Administration (FDA)- oversees most foods.United States Department of Agriculture (USDA)-Oversees most meat and poultry.Bureau of Alcohol, Tobacco and Firearms (ATF)-AlcoholEnvironmental Protection Agency(EPA)- pesticide regulation and waste water
43 Major Food Legislation Federal Food, Drug and Cosmetic Act (1938)-Authorized the creation of the FDA for food regulation.Federal Meat Inspection Act (1906)-mandatory inspection of animal, slaughtering conditions and processing facilities.Federal Poultry Products Act (1957)-
44 Major Food Legislation -Continued Federal Trade Commission (1938)-regulates against false advertising.Nutritional Labeling and Education Act (NLEA, 1990)- uniform and consistent labels.Food Quality Protection Act (FQPA)-regulates pesticide use in foods.
45 Role of Federal Regulations Ensure that foods are;*Safe*Pure*Wholesome*Sanitary*Honestly labeled
46 Activities of Federal Agencies Works with industry to interpret regulations.Helps industry establish control measures.Makes inspections of food plantsExamines food from interstate shipments.Issues and enforces regulations on food additives.Approves and certifies acceptable food colors.
47 Activities of Federal Agencies-Continued Tests for pesticide residuesExamines imported foods.Advises state and local inspection agencies.Works with state and local agencies in times of disaster to dispose of contaminated foods.Sets up “standards of identity” to promote honesty and value of food products.
48 Food Labeling Types of food label information. *Mandatory labeling information*Optional information which is regulated ifpresent.*Voluntary –unregulated information (recipes, preparation info etc)
49 Required Label Information 1)Common food name without confusing adjectives.2)Net quantity of contents3)Ingredients –list of ingredients in descending order by weight.4)Company name and address.5)Product dates- “sell by” or “use by”6)Nutritional information7)Other information-copyrights, trademarks, religious symbols.
52 Label Claims Every adjective has a well-defined definition; *Fat free- <0.5 gram fat per serving*Low-fat- have less than 3 gram fat perserving.*Light- product to have 33% fewer caloriesthan a standard reference product.Other examples include “fresh”, “good source of ___.”
54 Food Safety 30 million people become ill from foodborne pathogens. 9,000 people die each year in the U.S.$10-83 billion spent per year to treat foodborne illnesses.
55 Types of Microorganisms Molds or fungi-grains, nuts, fruit,vegetables.Yeasts- high sugar and acid foodsBacteria-high protein, meat products.Viruses- requires a living host.
56 Good Microbes Lactobacillus Acidophilus-used to make yogurt. Saccharomyces cerevisiae- used to make breadPenicillium-used to make cheese
57 Bad Microbes Salmonella-in raw poultry and meat. E coli 0157:H7- found in meat andvegetables.Campylobacter- found in poultryListeria monocytogenes- in ready-to-eatfoods.
58 Growth Rates of Microorganisms Microbes grow in 4 phases- the lag phase, the exponential growth phase, the stationary phase and the death phase.If microbes are placed in a growth media, their numbers will remain constant for a period as they adjust to the environment.Then their numbers increase exponentially as the microbes reproduce at their maximum rate.At some point the microbes cannot be supported and their numbers level off and then they begin to die.
61 Food ProcessingRaw foods typically arrive at a food processing facility in a fragile state. They must be quickly stabilized to prevent deterioration.Most non-meat and non-dairy product “respire” (breathe) meaning they use oxygen and sugar and convert it to carbon dioxide and water.Storing foods under controlled conditions can reduce or eliminate this reaction.
62 Common Receiving Operations Unloading-trucks and railcars carrying raw material must be off-loaded by dumping, pumping or conveyor operations.Grading- Products must be graded in some way depending on its future use. In addition, weeds, rocks and debris must be removed.Preliminary processing- drying, peeling, pitting, slicing, coring, pureeing, juicing among others.Storage-Raw food must be stored properly before processing.
63 Requirements for Food Processing plants Water- rule of thumb-It takes 2.5 gal of water to process one lb of raw material.EnergyWasteEnvironmentLaborTransportationTechnology
64 DryingDrying is the removal of water by natural or artificial means to further preserve a food product.Dehydration is the almost complete removal of waterConcentration is the removal of only portions of water from the food.
65 How Drying WorksHeat and Mass transfer- the combination of these two processes is very complex.In most cases, the product is heated and the heat will convert water into vapor which will migrate through the food to the surface.At this point, the vapor is absorbed into the air stream.The heating is referred to as “heat transfer” and the migration of moisture is referred to as “mass transfer”.
66 Water ActivityWater activity is a measurement of the available water in a food.Water activity is expressed as “Aw”.It ranges from 1.0 (pure water) to 0.0 (totally dry).Salt, sugar and similar compounds reduce the Aw.
67 Minimum Aw for Microbes Molds 0.80Yeasts 0.88Bacteria 0.90
68 Heat Processing Types of heat treatments include *Blanching- light heat treatment toinactivate enzymes.*Pasteurization- more severe heat treatmentto kill most microbes.*Commercial Sterilization- massive heat torender the product totally microbe-free
69 Changes in Microbial Population During Exposure to High Temperature Initially, only vegetative cells are destroyed.After a lag period, spore forming bacteria begin to be destroyed.See the next chart of the number of bacteria killed over time at a fixed temperature
71 Survivor Curve for Microorganisms The next slide will show the response of bacteria over time at a fixed temperature.The “D-Value”is the decimal reduction time or time to kill 90% of the population.The higher the “D-Value”, the more resistant the microbial population.
72 D-ValueD-Value is the decimal reduction time (time required to reduce the microbial population 90% at a constant temperature).D-Values varies for each microorganism and temperatureThe units of measurement are in minutes.The larger the D-Value, the more resistant the microbes are to heat.
75 Cold Preservation and Processing Timeline*Way Back- Refrigeration and freezing have been around for centuries using ice.*1875- The first mechanical, ammonia refrigeration system was developed.*1920s- Clarence Birdseye developed processes for quick-freezing foods and frozen food packaging.
76 Refrigeration and Freezing Refrigeration –storage of foods at 16 to –2C (61-28F). Most household refrigerator are set at 5C (40F).Frozen storage – Food held well below its freezing point, typically –18CMicroorganisms do not reproduce or grow at freezer temperatures but become dormant to grow again upon thawing.
79 The Major Roles of Food Packaging Preserve the foodProtect the food against physical damageProtect the food against microbes, insects etcProtect the food against environmental hazards.Add convenience to the consumerProvide information to the consumer.
80 PermeabilityPackages, especially those with plastic films will allow oxygen and other gases to penetrate the film at certain rates.
81 Types of Food Containers Primary- that which comes in direct contact with the food (jar, can etc)Secondary-outer box, case, wrapperTertiary-Contains secondary containers (pallets, bulk storage).
82 Types of Food Packaging Materials Metal-cans, foilGlass- jars and bottlesPaper-cartonsPlastic-rigid or semi rigid cans, bottles, bags, pouches and wraps.Laminates-combinations of more than one type.
84 Principle Constituents of Cow’s Milk Water %Fat %Protein %Carbohydrates %LactoseMinerals (ash) %
85 Amount of Milk Necessary to Make Dairy Products ButterCheesePowdered MilkIce Cream (1 gallon)Cottage cheeseMSNF (milk solids. no fat)22.810.07.66.86.2511.0
86 Bovine Growth Hormone (BGH or BST) Hormones regulate growth in cows and milk production.The synthetic version was developed by Monsanto and approved by FDA in 1993.Increases milk production by 10-15%.Some studies have shown 30% of humans are allergic to BGH
88 CheeseCheese is made by the coagulation of milk protein (casein) with an enzyme (rennin) and acid (usually lactic acid). Various types of cheeses are made by the addition of pressure, salt, aging,and fermentation with other microorganisms.Cheese is hardened (based on water content) and ripened (through the addition of microorganisms).
89 Steps in Making CheeseSetting the milk- Lactic acid bacteria are added to milk at 85F. After 30 minutes, the rennin is added. The curd develops.Cutting the curd-The curd is cut into small cubes so they the whey can be removed more easily.Cooking- The cubes are cooked for a period, usually 1 hour.Draining-Whey is drained.
90 Steps in Making Cheese- Continued Milling and Salting- The curd is milled into small pieces and salt is added to draw more whey out of the curd, reduce bacterial activity and improve the flavor.Pressing- The cheese is shapedCuring- Cheese is then stored for at lest 60 days and up to 1 year or more.
92 Animal ConsumptionMeat is loosely defined as the skeletal muscle of meat-type animals.Production of animals for human consumption is much more energy intensive than producing plants for human consumption.Worldwide, animal consumption is directly related to affluence.Feed requirements for species accounts for the relative price differences;Chicken – 2 lb feed per lb gainPork- 4 lb feed per lb gainBeef- 8 lb feed per lb gain.
93 Meat Processing Includes beef, hogs, sheep and goats. Animals are inspected, slaughtered and carcasses chilled.Carcasses are fabricated into major cuts;Beef- chuck, rib, loin, roundHogs- Shoulder, loin, belly and hamMajor or primal cuts can be send to retail outlets to be made into steaks, roast and chops.Trim is used to make sausage
94 Beef GradingAll carcasses are USDA inspected for safety and wholesomeness.- MandatorySome carcasses are graded by the USDA to predict eating quality-Optional.Grades are based on maturity and marbling (intramuscular fat flecks).Young- Prime, Choice, Select, StandardOld- Utility, Commercial, Utility, Cutter, CannerSome carcasses are yield graded to predict cutout yield.
95 Poultry ProcessingIncludes meats from chickens, turkeys, ducks and geese.Broilers can be raised for slaughter in 6 weeks.Poultry is inspected like all meat products.Product can be sold as;*Bone-in product (legs, quarters, wings)*Boneless whole muscle products(Breasts)*Comminuted Products (nuggets, patties)
96 EggsHens can produce 260 eggs per year. Over 70 billion eggs produced in US per year.Pasteurization- Eggs and egg whites are pasteurized by holding at 60C for min.Salmonella is the target microbe.Grading – Eggs are graded based on size (Extra large, large etc) and quality. Candling allows the inspector to see if there are blood spots, fertilized yolk or cracks in the shell.
97 Egg Composition Overall- 65% water; 12% protein; 11% fat White- 88% water; 11% protein; 0.2% fatYolks- 48% water; 17.5% protein; 32.5% fat.Almost all the fat is contained in the yolk. Eggs contain considerable amounts of vitamins and minerals.
99 Cereals Cereals are plants that yield edible grains. They are consumed worldwide and make up a majority of the worlds calories and 50% of protein consumption.Rice is the world’s most important food with wheat not far behind.In the U.S., corn is the leading grain but most is used for animal production while wheat is used directly for human consumption.
100 Composition of Some Cereals (%) GrainCornWheatOatsRiceMoisture Carbohydrates Protein Fat
101 Physical Characteristics of Grain Starchy endosperm- main part of the grain or kernel.Protective outer layers- bran or hullEmbryo or germ- typically located at the bottom of the kernel.
102 WheatWheat is classified into one of two types –Hard wheat is higher in protein than soft and produces a better dough. Soft wheat is better for batters.Wheat milling uses a succession of pulverizing steps to break down the endosperm. The bran and germ is also removed in the milling process.
103 RiceRice is unusual compared to other grains in that it is not ground into flours before consumption.The milling process is designed to remove only the outer bran layer without breaking the kernel.It is often used in the U.S. as a carbohydrate source for making beer.
104 Corn Corn is consumed as both whole kernels or as a flour. It can be dry-milled like wheat or wet-milled. Wet milling is popular and is used to make corn syrups and high fructose corn syrup
105 Legumes and OilseedsLegumes (beans and peas) and oilseeds are much higher in protein than grains and oilseeds are much higher in fat than grains.Soybeans are legumes that have oilseed characteristics.
106 SoybeansSoybeans are very versatile food products used for both animal and human foods.Soybeans can have up to 23% fat.Soy protein is quite extensively used for animal feed as a protein source.
107 PeanutsPeanuts contain 25% protein and 50% oil. They are used mainly to produce peanut butter (50% of the crop).They can also be used to make flour and used for oil.
109 Vegetables and FruitsFruits and vegetables are cultivated and processed similarly.Many vegetables are fruits by the truest botanical definition.Fruits are defined as those portions of a plant which houses the seeds-tomatoes, cucumbers, peppers, okra, sweet corn etc.
110 Vegetables and FruitsVegetables are those plant items usually eaten with the main course of a meal.Fruits are those plant items usually eaten alone or as a dessert.
111 Classification of Certain Vegetables Generally classified by their location on a plant.Are classified as earth, herbage or fruit vegetables.The next chart shows the classification system of vegetables.
113 Composition Fruits and vegetables have similar compositions They are very high in water content, their structures are derived from carbohydrates, they are low in fat and usually contain useful vitamins.The carbohydrate portion can be further broken down into digestible and indigestible parts (sugars and starches vs pectins and cellulose material).Vitamin A is found in yellow-orange fruits and vegetables and leafy, green vegetables.Vitamin C is found in citrus fruits, tomatoes and green, leafy vegetables.
115 Structural FeaturesCells- The cells of the edible portion of most fruits and vegetables are characterized by a large, water filled vacuole. Sugars and other water-soluble compounds may also exist in this area. Cellulosic material (complex carbohydrates) surround the vacuoles and also form the cell wall. Protein is also in the cell walls.
116 Structural FeaturesTurgor- The rigidity of cells is due to being filled with water. The cell membranes are elastic and “give and take” with changes in water content. Living plants have a high turgor, resulting in crispness. When plant tissues are damaged or destroyed by storage, freezing, cooking or other causes, turgor pressure is lost, leaving the tissue soft and wilted.
117 Structural FeaturesCellulose, Hemicellulose and Lignin- Young plants have little hemicellulose (and are softer than mature plants). Mature plants contain lignin which does not soften much during cooking. Cellulose, hemicellulose and lignin are basically complex carbohydrates that develop with age.
118 Structural FeaturesPectic substances- Pectins are naturally occuring in fruits and act to “cement” the cells together. Pectins has a gel-like action when cooked and are used to make jellies. An enzyme (pectin methyl esterase) also occurs and will react with pectin to reduce the gel-forming ability. The enzyme’s activity may be reduced or eliminated by blanching.
119 Color and Color Changes Chlorophylls- Imparts the green color to vegetables. Changes to pheophylin (olive or brown in color) under acid conditions or when heated. Creating alkaline conditions can preserve the green color but is not used very much because the texture may become soft and vitamins are destroyed.
120 Color and Color Changes Carotenoids- Imparts the yellow, orange and red colors to vegetables. It is fat-soluble and a precursor to vitamin A. Fairly resistant to heat, pH and leaching but sensitive to oxidation. Examples are carrots, corn, apricot, peaches, citrus, tomatoes and watermelons.
121 Color and Color Changes Anthocyanins- Imparts purple, red and blue pigments to vegetables. It is a flavonoid compound. Color is dependent on pH (blue in alkaline to red in acid). Compounds are very water soluble and easily leached.Examples include grapes, berries, plums, eggplant and cherries.
122 Color and Color Changes Flavonoids- Similar to anthocyanins. Imparts yellowish color. Examples are apple, potatoes and yellow and red onions.
123 Color and Color Changes Tannins- Naturally colorless but forms dark compounds in the presence of metals and at certain pHs. Examples are grape juice , tea and coffee.
125 Why are Beverages Consumed? Nutritive valueThirst-quenching propertiesStimulating effectsPleasure
126 Major Beverage Consumption Carbonated Soft DrinksCoffeeMilkBeerBottled WaterSelected Fruit JuicesTeaFruit drinks, cocktailsWineGallons/person/year48.824.323.722.116.014.28.47.91.9
127 Juice ProcessingExtraction-Fruit is pressed or ground to yield the juice.Clarification- Resulting juice may contain small particles of pulp and other debris. Typically, commercial enzymes are added to the juice to digest the suspended particles . Then the juice is centrifuged to remove the denser particles.
128 Juice Processing- Continued Deaeration- Air is removed to prevent oxidation and losses in vitamin C.Pasteurization- performed to reduce microbial counts and inactivate enzymes.
129 Fruit Juice Concentrates Since most juices have a very low solids content, the juice may be concentrated to provide a more valuable product for shipping. The water that is evaporated contains significant amounts of volatile flavor compounds. These are recaptured and added back to the juice or used as flavorings for other products.
130 Quality Factors in Foods and Sensory Evaluation
131 Quality Factors in Foods Appearance Factors- may be interpreted differently by different people. It has some highly subjective measures and some highly objective measures.1)Size and Shape- sizers and weight2)Color and Gloss- light transmission, colorcharts and colorimeters.3)Consistency- viscometers
132 Quality Factors in Foods Textural FactorsRefers to factors we feel with our fingers, teeth, tongue etcAlso called “rheological properties”Ex Crispiness, chewiness, stickiness etcMeasured by rheometers-viscometers and texture analyzers
133 Quality Factors in Foods Flavor FactorsCombination of taste and smell-very hard to measureMost flavor compounds are highly volatile (easily evaporated from foods).Many times, flavor is associated with color.Taste panels may be used to distinguish between different flavors
134 Sensory EvaluationSensory evaluation is the scientific discipline used to evoke, measure, analyze and interpret those reactions to characteristics of foods and materials as perceived through the senses of sight, smell, taste, touch and hearing.
135 Sensory Perception Step by Step Stimulus; appearance, flavor, textureSensation; Sensitivity of individual, not under the control of the brain.Perception; Mental treatment of the signal.Response; Expression of the perception.
136 Perception of Taste and Flavor The basic tastes are perceived on the tongue. Aroma and flavors are perceived through the nasal cavity.
137 Taste and PerceptionThe perception of basic tastes (salt, sour, bitter and sweet) are perceived on the tongue and involve compounds that are soluble in water or oil.Receptors are located primarily on the tongue but some are also present on the surface of the palate and in areas of the throat.
138 Taste and PerceptionRecovery time varies between seconds but certain bitter compounds may remain on the receptor for hours.There are 9,000 taste buds on the tongue. Sensitivity is not related to the number of taste buds. The areas marked on the following chart are where the receptors of a particular type predominate.
140 Sensory Evaluation There are three basic categories of Sensory tests. 1)Discrimination- “Are products different in any way”2)Descriptive-”How do products differ in specific sensory characteristics”3)Affective-”How well are products liked or which products are preferred”
141 Discriminative Testing Triangle Test- Applications*Used to determine if a difference exists between two products.*Is our reformulated juice blend identical to the original formulation?*After what storage duration can we see a difference between a stored potato chip and a freshly processed product?
142 Discriminative Testing Triangle Test –Method1)Three coded samples are presented.2)Subjects are instructed that two samples are identical and one is different.3)Subjects should taste the samples and select the odd sample.
143 Descriptive AnalysisAll descriptive methods involve the detection and quantification of sensory characteristics present in a product or a set of products.In some cases, one can differentiate two products based upon the sensory characteristics present (detection).In most practical applications, two products will exhibit the same sensory characteristics.
144 Descriptive AnalysisOne can then differentiate between products based on the intensity reported for each attribute.Descriptive analysis is the most sophisticated sensory method available and is the only method allowing discrimination between products based upon intensity differences
145 Affective Testing-Consumer Testing It is the ultimate test for a food product.Consumers are difficult to understandTheir preferences are different.Panelists used are not trained but ordinary consumers.Highly unreliable- Requires a large number of consumers (>200).
147 Irradiation We take our food safety for granted. We have the safest food supply in the world but we still have reported cases of foodborne illnesses.Foodborne illnesses are reported to range from million cases per year.
148 IrradiationIrradiation works like x-rays. The food product is passed through a radiation field in which the gamma rays destroy most microorganisms and insects.Irradiation gives processors and consumers much more flexibility in their food-handling operations. In some cases, a food is made shelf-stable for longer periods of time. In other cases, the food benefits from more than just a microbial hurdle. Fruits, for example, will remain fresher longer if it has been e-beam pasteurized.
149 Irradiation Foods are NOT made radioactive Irradiated foods do not pose a health risk.Irradiation does not kill all microbes-safe food handling practices are still necessary.There are some consumer concerns such as worry about unusual, harmful compounds being generated, sanitation at food processing facilities will be sacrificed, it will cause a nuclear accident etc.
152 Organic Foods“Organic” is a labeling term that denotes products produced under the authority of the Organic Foods Production Act. The principle guidelines for organic production are to use materials and practices that enhance the ecological balance of natural systems and that integrates the parts of the farming system into an ecological whole.
153 Organic Foods“Organic” does not refer to the food itself but to how it is produced. Organic food production is based on a system of farming that maintains and replenishes the fertility of the soil. Organic foods are produced without the use of synthetic pesticides and fertilizers. Organic foods are minimally processed to maintain the integrity of the food without artificial ingredients, preservatives or irradiation.
154 Is Organically Grown Produce Healthier than other Produce? Certified organic produce is not essentially healthier than produce that has been grown under non-organic conditions. The nutritional content of a particular vegetable doesn’t change. But the lack of synthetic pesticide residues on organically grown produce may make for a safer product. Organic products may also have higher incidences of pathogenic bacteria.
156 BiotechnologyAgricultural Biotechnology is a collection of scientific techniques, including genetic engineering, that are used to create, improve or modify plants, animals and microorganisms. Using conventional techniques such as selective breeding, scientists have been working to improve plants and animals for human benefit for hundreds of years. Modern techniques now enable scientists to move genes (and therefore desirable traits) in ways they could not before and with greater ease and precision.
157 Benefits of Biotechnology Crop resistance to disease, pests etcImproved shelf life of foodsOptimization of the enzymes used in food processingEnvironmental impacts through lower energy costs and less pesticide/ herbicide use.Improved health through dietary impacts.
158 Negatives of Biotechnology Who owns the control of patented genes and biotechnology techniques?Cross-contamination with plants and insectsAllergenicityNew toxins
159 Crops that have been Genetically Modified Soybeans-reduced saturated fatSoybeans-resistant to pestsSoybeans- resistant to herbicidesCorn-resistant to pestsCorn-resistant to herbicidesTomatoes- resistant to pestsTomatoes-delayed ripeningGolden rice-beta-carotene added to rice
160 SUMMARYThis module has covered numerous topics within the area of Food Science. Topics covered included the chemistry of foods, nutrition, government regulations, microbiology, packaging, quality, processing and biotechnology.