Experimental Food Science Exam#1
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the application of the basic sciences and engineering to study the physical, chemical, and biochemical nature of foods and the principles of food processing.
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food science
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physical properties
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Firmness, Texture, Viscosity, Melting point, Boiling Point
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chemical properties
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Sugar, Acid, pH, Protein, Fat, Moisture, Carbohydrates, Micronutrients
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biochemical reactions
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Enzyme activity, Oxidative reactions, Degradation reactions
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the application of knowledge generated by food science in the selection, preservation, processing, packaging and distribution of foods as it affects the consumption of safe, nutritious and wholesome food.
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food technology
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qualities involved in selection of foods
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Variety or breed, Maturity, Climate, Harvesting technique
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processing techniques
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Washing, Peeling, Cutting, Blanching, Grinding, Extruding, Heating
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food preservation techniques
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Refrigeration, Freezing, Dehydration, Canning, Pickling, Fermentation
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Now, 1 farm worker produces enough food to feed how many people?
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130 people
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what percent of the U.S. workforce is involved in production agriculture
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less than 2%
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how many people do not have enough food to eat?
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2 billion
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how many people die daily due to starvation and disease related to malnutrition?
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40,000
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essential inputs to human life
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Food, Water, Oxygen (O2)
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essential inputs to plant life
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Nutrients, Water, O2 & CO2
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What is a good question for an experiment?
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One that is testable with the materials at hand
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What is a hypothesis?
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Your best thinking about how the change you make might affect another factor. Tentative or trial solution to the question. An if - then statement
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the variable that is purposely changed. It is the manipulated variable.
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independent variable
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the responding variable.
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dependent variable
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What are repeated trials?
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The number of times that a value of the independent variable is tested.
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Why are repeated trials necessary?
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They reduce the possibility of chance errors affecting the results.
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Numbers in the form of raw data displayed in data tables and graphs
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quantitative data
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They are what you perceive that occurred during the course of your experiment. They are identification of trends in the data.
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qualitative data
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Involves instrumentation and use of physical and chemical techniques to evaluate food quality.
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objective evaluation
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visible light spectrum
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390-760nm violet to red
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three dimensions of color
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hue, value/lightness, chroma/saturation
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brightness
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Value/Lightness
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purity of the color
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Chroma/Saturation
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dominant wavelength, typically referred to as "color"
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Hue
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up and down on munsell color system
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value
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around on munsell color system
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hue
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out from middle on munsell color system
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chroma
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sensed primarily by the feeling of touch, are related to the deformation, disintegration, and flow of the food under a force/stress and are measured objectively by function of mass, time and distance.
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texture
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types of stress
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tension, Compression, Shear
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measures the force to penetrate the flesh of fruit and vegetables
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puncture test
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Seven parameters can be determined from the texture profile analysis
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Fracturability, Hardness, Cohesiveness, Adhesiveness, Springness, Gumminess, Chewiness
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The science of flow and deformation of materials, both liquid and solid
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rhelogy
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three main categories of rehlogy
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Elasticity, viscosity, plasticity
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Resistance of a fluid to flowing freely, caused by the internal friction of a moving fluid
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viscosity
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distance a food flows under its own weight in a given time period
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Bostwick Consistometer
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A scientific discipline used to evoke, measure, analyze and interpret those responses to products that are perceived by the senses of sight, smell, touch, taste and hearing
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Sensory Evaluation
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Relies on the opinions of selected individuals to evaluate the products through various types of sensory tests
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Taste panels
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panelist selection
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Free of colds, chew no gum immediately before testing, not ingested any other food for at least 1 hour before testing, nonsmokers, not color blind, have no strong likes or dislikes for the food to be tested
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how are taste samples labeled?
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labeled with random 3-digit codes to avoid bias
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Are products different?
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Discrimination/Difference Tests
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If products are different, how are they different?
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Descriptive Tests
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What is the acceptability of a product? Is one product preferred over another?
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Affective/Acceptance Tests
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types of difference tests
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Given triangle, duo-trio or paired comparison tests
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Choose the sample that is most different
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triangle test
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Choose the sample that matches the reference
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duo-trio test
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Which sample is sweeter?
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Paired Comparison Test
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A small group of highly trained panelists are asked to rate particular aspects of a product on a scale
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descriptive tests
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Widely used in marketing research hedonic scales used to determine which product is preferred
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affective tests
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percentage of water in human body
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60-70%
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4 uses of water
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universal solvent, transfer medium for heat, chemical reactions, food processing techniques
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Largest amount of water; easily separated from food
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free water
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incorporated to the chemical structure of food (protein, starch, pectin, etc.); not easily removed; e.g., bread
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Bound Water
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the energy required to raise the temperature of 1 g of water by 1 ˚C
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specific heat of water
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a two phase system, where one phase (dispersed phase) is dispersed in the second phase (continuous phase)
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colloidal dispersion
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consists of two immiscible liquids, one of which is dispersed in the other as droplets
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emulsion
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the vapor pressure of water in food divided by vapor pressure of pure water at the same temperature
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water activity
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indicates the amount of water that is available to microorganisms in foods.
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water activity
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water activity of highly perishable foods
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0.95
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water activity of microbial growth
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.60 and above
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ways to lower water activity
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remove water, add solutes
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the relationship between water activity and water content at a given temperature
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Moisture Sorption Isotherm (MSI) Curve
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Glucose derived from photosynthesis is stored as starch granules in plants
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starch
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2 components of starch
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Amylose Amylopectin
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% amylose
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25%
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% amylopectin
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75%
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Linear component of starch Contains 1,4-α-glucosidic bonds
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amylose
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Branched component of starch Contains 1,4-α-glucosidic as well as 1,6-α-glucosidic bonds approximately every 20 glucose units
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amylopectin
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roots/tubers contain ________ amylopectin than cereals
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more
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where are starch granules made?
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cytoplasm of plant cells
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how are starch granules held together
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hydrogen bonds
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steps in gelatinization
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heat, h-bond interchange, swelling (increases w/ temp), amylose leaches out of granule, granules collapse
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factors affecting gelatinization
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Type of starch, Temp, Sugar Acid, Fat and proteins, Enzymes
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Worst thickening ability
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wheat starch
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potato starch
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Best thickening ability
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Gelatinization temperature reached at
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140-160F
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Gelatinization completed at
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190-194F
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type of heat for gelatinization
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moist
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delays gelatinization and decreases viscosity by competing with the starch for water
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sugar
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hydrolysis of starch to dextrin caused by dry heat
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dextrinization
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breaks down starch molecules, Less water absorption by starch granule, Decreases viscosity
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acid
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"waterproofs" starch granules so that water does not easily penetrate during gelatinization process
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fat
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enzyme acts anywhere on the starch chain
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α-Amylase
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enzyme that hydrolyzes 1,4-α-glycosidic linkage and 1,6-α-glycosidic linkage
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β-Amylase
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Free amyloses lose energy and form H-bonds, a network that holds the swelled granules in place
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gelatin
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starch regains its more ordered and crystalline structure (retrogradation), so product becomes firmer and more brittle
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stale
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Instant starch that has been gelatinized and then dried
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Pre-gelatinized Starch
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Decreases thickening power, but makes a strong gel because hydrogen bonds form more readily
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Acid-modified Starch
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Occurs when -OH groups of one chain bonds with -OH group on adjacent chain More resistant to low pH, high temperature, high shear, and retrogradation
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Cross-linked Starch
