NDFS 250 Exam 2

Define and explain the flour treatments: aging/oxidation, bleaching, and enrichment.

Aging/oxidation: increases disulfide bonds to get stronger easier to handle (less sticky) dough. Bleaching: color changes, yellow xanthophylls removed. Enrichment: addition of thiamin, riboflavin, niacin, iron, and folate.

State the deteriorative changes that occur during egg storage and explain how egg quality is measured.

Air cell enlarges (due to water loss), pH rises from 7.6 to 9.6 (due to CO2 loss), yolk flattens (due to thinning of vitelline membrane), thick white thins (due to disulfide bonds breaking and CO2 loss), chalazae is less pronounced/yolk is off-centered in shell egg

Define antioxidant; state the names and acronyms of common antioxidants; explain how they work.

An antioxidant is a molecule that donates a hydrogen atom to quench free radicals--naturally or synthetically occurring. BHA: butylated hydroxyanisole; BHT: butylated hydroxytoluene; TBHQ: tertiary butylhydroquinone; PG: propyl gallate; Vitamin E: alpha-tocopherol

Define emulsion, including types of emulsions, and give examples.

An emulsion is a mixture of water and lipid (fat or oil); it is a colloidal dispersion of one liquid in another, where the two liquids are naturally immiscible. Ex. oil in water (mayo, most foods), water in oil (butter, margarine). 2. Explain emulsion formation. Emulsion formation requires the addition of an emulsifier which is mixed with the continuous phase, followed by agitation (shaking, mixing, blending), then slowly adding the dispersed phase. Emulsifiers lower the interfacial tension of one liquid more than the other.

Explain why food preservation is beneficial despite any related nutrient losses.

Availability, variety, quality, convenience, cost

Explain proper food handling techniques (clean, separate, cook, and chill).

1. Clean: wash hands and surfaces often 2. Separate: don't cross-contaminate (ready to eat vs. raw) 3. Cook: cook foods to proper temperature 4. Chill: refrigerate foods promptly

Explain the types and causes of emulsion instability.

1. Coalescence: merging of oil droplets-- oil/vinegar dressings that are temporary emulsions 2. Creaming: separation into two phases-- unhomogenized milk or whipping cream in the refrigerator 3. Inversion: change of emulsion type: o/w←→ w/o--churning of cream to butter

State the types of low temperature preservation and recommended temperatures.

1. Common or cellar storage (<15 deg C...slightly cooler than outside), short term, for root crops, potatoes, cabbage, celery, apples 2. Refrigeration (0-10 deg C), weeks to months, most foods 3. Freezing (<-18 deg C), months to 2 years, most foods

State and explain the variables that must be known to preserve food using heat.

1. Effect of heat on microorganisms (to inactivate them)--depends on nature of bacteria 2. Heat penetration properties of each specific food in its container (how it affects food texture, its size, etc.)

State the three types of leavening gases and explain how they are generated/incorporated into food.

1. Air (physically by creaming, folding, beating...), 2. Steam (phase change when water is heated), and 3. Carbon dioxide (chemical/biological reactions: baking powder, baking soda, yeast, or bacteria).

State six examples of endogenous food enzymes and the reactions they catalyze, including substrate(s) and products (words, not structures).

1. Amylase: flours for bread. 2. Pectinase: fruit juice clarification. 3. Chymosin: cheese. 4. Lactase: low-lactose milk. 5. Papain: meat tenderization. 6. Glucose isomerase: high fructose corn syrup. 7. Invertase: candies. 8. Glucose oxidase: glucose removal to prevent Maillard browning.

State three general categories of food safety concerns and give examples of each.

1. Biological (ex. Biotechnology/GMO's, bacteria and pathogens) 2. Chemical (ex. natural toxins, pesticides, food additives, accidental chemical contamination, toxic metals) 3. Physical (ex. Pieces of foreign non-food objects, etc.)

State the basic causes of food deterioration.

1. Biological (microorganisms or infestation by rodents, parasites, insects) 2. Chemical (nonenzymatic reactions, such as lipid oxidation and Maillard browning, and enzymatic reactions) 3. Physical/environmental (incorrect storage temperatures, gain/loss of moisture, reactions with oxygen or light, physical stress, time)

List and explain the basic steps of flour milling.

1. Blend (types of wheat mixed for specific flours), 2. Clean (wash/remove non-wheat), 3. Temper (water added and held 6-24 hrs.), 4. Break (corrugated rolls break wheat into coarse particles), 5. Purify (air currents and sieves remove bran and classify particles by size/weight), 6. Reduce (smooth rolls reduce middlings into flour), and 7. Sift (broken wheat separated through successive screens of increasing fineness).

State the four main structural components of cereal grains.

1. Bran (fiber containing, outer protective layer), 2. Germ (unsaturated fat and vitamins), 3. Endosperm (starch in a protein matrix), and 4. Aleurone cells (cells separating bran from endosperm; high in amylase and protein). Think "GABE."

State the functional properties of eggs.

1. Emulsifying: there are phospholipid surfactants in the yolk (lecithin). 2. Foaming, leavening: egg whites increase 6-8 times in volume when beaten (unless yolk is present; yolk lip is prevent foaming). 3. Binding: proteins coagulate, binding ingredients (ex. meatloaf, breading). 4. Thickening: proteins coagulate, thickening mixtures (ex. Hollandaise sauce). 5. Gelation: proteins coagulate, forming a gel (ex. custard). 6. Color, flavor, nutritive value, etc.: yolk adds yellowish color to baked goods; fat provides flavor and inhibits staling; yolks and whites provide nutritional value.

State the functions of fat in food.

1. Flavor and satiety 2. Texture (flakiness, tenderness), 3. Leavening of batters/doughs 4. Emulsifier 5. Transfer of heat (ex. frying) 6. Prevention of sticking

Explain hydrogenation, interesterification and superglycerination of fats and their significance.

1. Hydrogenation: addition of hydrogen gas (H2) to the double bonds of unsaturated fats, converting them to saturated fats. Oil is heated with a finely divided nickel catalyst. System is evacuated and H2 gas is admitted. Changes texture and improves stability. 2. Interesterification: Process of heating fat in the presence of a suitable catalyst to hydrolyze the fatty acids and re-esterify them with glycerol in a more random order. Molecules become more heterogeneous, resulting in smaller crystals and a wider plastic range. 3. Superglycerination: process of incorporating a 3-6% emulsifier (glyceryl monostearate) into shortening to improve its baking qualities (ex. shortening).

Explain the various methods of freezing, including the effect of freezing rate.

1. Immersion freezing: direct immersion of food—liquid nitrogen and CO2. 2. Cryogenic freezing: liquid nitrogen or CO2 sprayed directly on food—creates "snow" and vapor that remove heat through phase change. 3. Individually Quick Frozen (IQF): rapid freezing of individual pieces—1) fluidized bed and 2) continuous contact/blast freezer. Effect of freezing rate: rapid freezing gives best quality and texture—chemical reactions limited quickly and ice crystals numerous and small so less damage to texture.

Explain the two types of rancidity and their mechanisms.

1. Oxidative rancidity: due to lipid oxidation; requires oxygen (causes are heat, metals, and light--pro-oxidants--or oxidative enzymes: lipoxygenase). Occurs near double bonds between carbons. 2. Hydrolytic rancidity: due to lipid hydrolysis; requires water (causes are heat and hydrolytic enzymes: lipases). Only require a small amount of fat and greatly shorten shelf life/deteriorate food. Occurs when short-chain fatty acids are hydrolyzed from the glycerol.

Explain processing techniques: retort (pressure canner), aseptic, hot fill and hold, and boiling water bath; explain the need to vent retorts.

1. Retort: large pressure cooker, holding hundreds of cans or other food containers, used to heat process packaged foods. Pressure canner= large pressure vessel for heat processing LOW ACID foods in bottles/cans. Need to VENT retorts:venting= removing air from retort to ensure it contains only steam (no air). Aka exhausting; removes oxygen and creates a vacuum for safety. 2. Aseptic processing: commercial sterilization and cooling—food added to sterile container in aseptic chamber (less heat required—advantages: better nutrient retention, higher sensory quality, less energy required, and plastic can be used). 3. Hot fill and hold: hot food filled into container, sealed, inverted, and held before cooling to sterilize lid. Used with acidified foods where C. botulinum not a concern, such as jam/jelly. 4. Boiling water bath: foods at pH 4.6 or lower (high acid foods like berries)—get temperature up without destroying foods.

Explain flour classification based on physical characteristics and use.

1. Texture (hard: >12% protein, soft: <11% protein), 2. Color (red or white), 3. Season (winter, planted in fall, or spring, planted in spring), and 4. End use (common or club for flour, or durum used to make semolina for pasta).

State the general nutritional content of egg.

8% fat, 12% protein, 62% cholesterol, no carbs, and a little sodium and potassium; good source of riboflavin, phosphorus, and vitamin D (and vitamin B12). Also other traces of vitamins and minerals. Takeaway: many vitamins and minerals, low in calories, high in cholesterol and protein; some fat. High quality protein for complete balance of essential amino acids.

State the types of starch modifications, including their applications.

Acid-modified (Thin-boiling starch prepared by heating starch below its gelatinization temperature in dilute acid. Low viscosity when heating allows it to be pumped while hot; forms a clear gel; ex. gum drops), cross-linked starches (contain molecules that have been cross-linked with ether/ester linkages to minimize breakdown of starch in acid; ex. in canned/frozen goods), and pregelatinized starch (starch that is precooked and dried; dispersible in cold water; ex. instant pudding or rice).

State the advantages and disadvantages of low temperature preservation.

Advantages: better sensory quality, better nutrient retention in some cases; disadvantages: cost (continual energy output); shorter shelf life than drying/canning

State the ingredients of baking powder; explain the action of slow and fast acting acids and categorize/recognize specific compounds in both groups.

Baking powder (AKA MONOCALCIUM PHOSPHATE MONOHYDRATE): 25% dry baking soda, 25% starch (filler), and 50% dry acid (acid salts). Fast acting: liberates a high proportion of CO2 in cold dough/batter. Ex.: lemon juice (citric acid), vinegar (acetic acid), molasses (aconitic acid), cream of tartar (potassium acid tartrate), and monocalcium phosphate monohydrate (baking powder). Slow acting: most CO2 forms in oven (late stage leavening). Ex.: cake mixes, double acting baking powder, self-rising flour, quick breads with texture of yeast breads...pretty much all the chemical names beginning with Sodium and Glucono-... :)

Explain the changes in food during cool storage and during freezing/frozen storage.

COOL STORAGE CHANGES: Slowed but continued microbial growth, chemical= starch—> sugar in potatoes and staling of bread, off flavors (certain foods like meat due to more oxidized fats), chill injury in some foods (ex. bananas) FREEZING STORAGE CHANGES: movement of water from cells

Explain casein micelle structure and milk fat globule structure.

Casein micelles are a colloidal dispersion; fat globules are a suspension (or a colloidal dispersion if homogenized). Casein micelle: the major protein fraction of milk (80%); micelles have an aggregated, mostly spherical structure of aggregated proteins. Colloidally dispersed, consisting of alpha, beta, and kappa. The isoelectric point of casein is at pH 4.6 (when least soluble; milk is usually 6.6). K-casein on surface because protein tail helps keep it suspended as a colloid (otherwise it precipitates out). Fat globule: spherical droplets of lipids in the form of emulsified fat in native milk; consists of phospholipid, high-melting triglyceride, cholesterol, and vitamin A.

Explain cheese production, including the role of acid and chymosin (rennet).

Cheese is the curd of milk; it is mostly casein once whey has been drained. Caused by acid (starter culture→ lactic acid OR acid directly added) and enzyme (rennet/chymosin--mixed in then sits still) aggregation of casein micelles. The enzyme, chymosin, cuts off the K-casein tail, therefore decreasing the micelle's water solubility. Because the micelles are now hydrophobic and are attracted to one another (instead of the surrounding water), they clump together and aggregate/precipitate. Rennet= crude extract; chymosin=enzyme within--also made synthetically.

Explain the structure of cis- and trans- fats, and omega-3 fats.

Cis double bonds: hydrogens on same side; chain bent/kinked; naturally occurring. Trans double bonds: hydrogens on opposite sides; chain is straight; increases bad cholesterol and decreases good cholesterol.

State the factors that affect the composition of cow's milk.

Composition depends on: genetics/breed (> fat in Jerseys), age (fat content declines with age), season (higher fat and protein in winter), stage of lactation (initial colostrum high in protein, immunoglobulins), and feeding regimen.

Explain the purpose of container head space and vacuum.

Container head space allows contents to expand, creating a partial vacuum to protect from damage by oxygen.

Define: cooking, pasteurization, blanching, canning, sterilization, and commercial sterilization.

Cooking: heating or reheating of food, usually by consumers; pasteurization: treatment to destroy pathogenic organisms, reduce bacterial count, and inactivate enzymes; blanching: steaming/boiling water immersion for a short time (inactivates enzymes, usually prior to freezing vegetables); canning: treatment to destroy all pathogenic and spoilage organisms (thermophiles may be present)--two types= boiling water bath and RETORT (pressure cooker); sterilization: treatment to destroy all microorganisms and spores; commercial sterilization: treatment to destroy pathogenic and spoilage microorganisms only--may contain some thermophiles (as in canning)

Define D-value and the purpose of using a "12 D process."

D-value: time at a given temperature to reduce microbial population of a given population by 90% (1 log); 12 log reductions used as a buffer/overkill to account for potential higher counts or variations in bacterial resistance...it's the law!

Explain egg pasteurization, proper egg storage, and other steps to ensure safe consumption of eggs.

Dehydration--spray drying--glucose first removed to preserve flavor and color (impacted by Maillard browning). Freezing: pasteurized first; need to add NaCl, sugar, or corn syrup for texture preservation upon thawing (protein aggregation causes lumpy texture). Pasteurization: to eliminate pathogenic bacteria, especially Salmonella spp. Denaturation: white= 60 → 65; yolk= 65 → 70. Temperatures of Pasteurization: white= 134 deg F; whole egg= 140-143 deg F, both for 3.5 to 4 minutes. Storage: refrigerate (sometimes coated in mineral oil) to slow deterioration from aging, such as: air cell enlargement, thinning of the thick white, and yolk flattening.

Define protein denaturation and explain its significance.

Disruption of any of the higher order structures of the protein without disrupting the primary structure. The spatial arrangements of the polypeptide chains are changed to a more disordered arrangement. Causes: heat, acid, salts, freezing, or mechanical action (shearing/pressure). Effects: Decreased solubility, loss of function, e.g., enzymes don't work, and increased susceptibility to proteases.

Distinguish drying and dehydration, and state the three parameters controlled during dehydration.

Drying: removal of water from a food using ambient conditions (ex. sun) Dehydration: removal of water from a food using controlled conditions of heating, forced air circulation, and relative humidity (ex. home dehydrator)

Explain egg white foam structure, formation and stabilization.

Egg white is an aqueous dispersion of proteins--when beaten or whipped, air is incorporated. The > the air, the > the aqueous film separates adjacent air and thins. Protein denatures, with hydrophobic groups orienting toward the air. This lowers the surface tension of the water, facilitating foam formation.

Define enzyme and active site, including the general reaction of enzymes.

Enzymes are proteins that act as catalysts in reactions involving specific substrates (endogenous or exogenous). Active site: the region of an enzyme that binds the substrate; contain amino acids and co-factors in a spatial arrangement to facilitate the making and breaking of certain bonds. E + S ← → ES complex → E + P

Explain briefly the production of the various types of milk products, including the microorganisms used in making cultured buttermilk and yogurt. Define filled milk and imitation milk.

Evaporated: 60% H2O removed, homogenized, and sealed. Sweetened condensed: 50% H2O removed, 44% sucrose added so not sterilized. Non-fat dry (NFDM): skim milk that has been pasteurized, condensed, and spray-dried. Instant non-fat dry: NDFM that has been wetted, agglomerated and re-dried to increase ease of rehydration--flavor worse. Dried dairy: why, casein, or dry whole milk (by spray drying). Buttermilk: milk cultured with Streptococcus lactis, Streptococcus cremoris, and Lactobacillus citrovorum till titratable acidity reached. Yogurt: milk cultured with Streptococcus thermophilus and Lactobacillus bulgaricus. Filled milk: milk fat is replaced with a less expensive fat/oil. Imitation milk: both milk fat AND milk proteins replaced with less expensive ingredients (ex. Water, corn syrup, sucrose, vegetable fat, whey proteins).

Explain freezer burn and how to prevent it.

Freezer burn: dehydrated surface on frozen food—gray, dry, grainy patches. Fluctuations or increase in freezer temperature cause this. Prevent: use small containers, tight seals, water proof/resistant, durability, and low permeability to other gases.

Explain gelatinization/pasting and the influence of sugar, acid, salts and fats on gelatinization.

Gelatinization/pasting: thickening of a starch as it absorbs water, swells irreversibly (you can't uncook rice), loses birefringence, rapidly increases in viscosity, and leeches amylose. Effects on ingredients--Sugars: granule swelling limited because sugar competes for water. Decreases thickness of gelatinized starch. Increases gelatinization temperature. Makes swollen granules more resistant to rupture. Acids: hydrolyze starch, reducing viscosity (slight hydrolysis may open granule, producing a thicker paste). Salts: generally not much effect; may increase gelatinization temperature (because salt affects the BOILING POINT). Fats/Surfactants: fats "water-proof" the granules so that water cannot penetrate easily. Surfactants markedly increase the gelatinization temperature.

Define the terms: birefringence, waxy starch, syneresis, staling.

Gelatinization: water and heat cause starch intermolecular bond breakdown--irreversible and dissolves starch granule in water. Causes loss of birefringence (refractive index with light). Waxy starch: only contains amylopectin (NO amylose), begins to thicken at lower temperatures; becomes less thick, does not gel, and does not undergo retrogradation. Syneresis: the release of water during retrogradation (partial re-crystallization of starch molecules after gelatinization and cooling). 1. Amylose normally forms gel to entrap water--2. The amylose then retrogrades (partially recrystallizes) and the gel can lose water (syneresis). Staling: a chemical and physical process of hardening, especially in breads. Although refrigeration slows microbial growth, it increases staling.

Explain the formation of gelatin gels; explain why certain raw fruits cannot be added.

Gelation is solubilized or dispersed in hot water. As the gelatin sol cools, viscosity increases due to molecular interaction between polymers. With further cooling viscous liquid changes to viscoelastic solid. Gelatin molecule association along polypeptide chains called crystallites or junction zones. Some fruits and vegetables can be added after gel partially thickens to prevent floating. Raw figs, kiwi, and pineapple cannot be added because the proteases hydrolyze the gelatin.

Define gelation and explain how gels form.

Gelation: protein, pectin, and starch gel formation. 1. Long polymers (e.g., starch, gelatin, pectin) are colloidally dispersed as a liquid - a sol. 2. The polymers interact with each other via hydrophobic interaction or hydrogen bonding 3. A three dimensional network forms that entraps water.

Explain how to optimize the storage life of dehydrated foods.

H. A. L. T. (Humidity--low moisture: humidity allows mold growth and accelerates chemical reactions, Air--no oxygen: oxygen allows mold growth and destroys fat/pigments, Light--eliminate: light destroys fats/pigments/some vitamins, Temperature--cool but not frozen: high temperature accelerates chemical reactions)

Draw the structure and explain the formation of a monoglyceride containing butyric acid.

HOOC CH2 CH2 CH3; HYDROLYSIS (LOSS OF WATER) OR ESTERIFICATION WITH GLYCEROL AND FATTY ACID; BUTYRIC ACID= four carbons

Contrast the formation of gels using high methoxyl and low methoxyl pectin.

High methoxyl pectin (HMP) gels -Gel formed by balance of acid and sugar -pH 2.8-3.4 -40 to 70 % sugar (Usually 60-65%) Low methoxyl pectin (LMP) gels -Junction zones formed by calcium "bridges": COO- groups on separate polymers bind Ca++ -pH 3.2-4.0 is needed to ensure enough acid groups are negatively charged, to allow interaction with Ca++ -Less or no sugar is needed -Requires addition of calcium ions (Ca salt bridges) -Application: Low calorie jams and jellies

Explain the risks if frozen foods are not stored below the recommended temperature.

Higher temperatures—even if still frozen—are dangerous: microbes activated, freezer burn more likely, enzymes more active, possible textural changes.

Explain the heat penetration properties of food and containers, including cold-point.

Important in determining time needed to reach cold point. 1. Conduction: heat transferred by molecular activity from one substance to another (ex. hot stove to saucepan; most foods; slow), cold point in middle. 2. Convection: movement of heated substance itself (faster, ex. water in saucepan, warmer water rises-because less dense-and cooler water moves downward; thick foods like creamed corn, soup, cake batter), cold point closer to bottom. 3. Radiation: transfer of heat directly from radiant heat source (fastest; ex. heat from sun, infrared lamp, broiler, campfire—in same manner as light and with same velocity). Containers: metal cans, glass bottles, retortable foil pouches, plastic containers, others...all are hermetically sealed (airtight).

List the steps and explain the purposes of blanching vegetables before freezing.

Improves color, flavor, and texture (due to enzyme inactivation). Reduced microbial load, nutrient preservation, better packing, and removes off odors/flavors. (Fruit is too delicate.) 1. Boiling water (salt optional), 2. place vegetables for a minute, 3. quickly remove, and 4. immerse in cold water to stop cooking.

State and distinguish the types of flour based on type of wheat, particle size and composition.

In order of decreasing particle size/coarseness: Farina/semolina (thick for hot cereal), whole wheat (bran, germ, endosperm), bread (long patent), all purpose (long patent), pastry (short patent), and cake (short patent). Long patent/straight flour: entire endosperm without bran or germ. Short patent/patent flour: coarse protein particles have poor hydration properties--fractions of endosperm, bran, AND germ removed.

Define the two categories of microorganism-caused foodborne illnesses and designate which organisms belong to which category. Recognize the names of the common food-borne pathogens.

Intoxication: food poisoning--when illness caused by ingesting a preformed toxin (ex. Staphylococcus species); Infection: illness caused by ingesting living organism that grows in GI tract, then causes toxins (ex. Salmonella species)

Discuss the feasibility of eating only locally produced fresh foods.

Is it in season? Equipment and energy to process, storage/space, quality, and self reliance...will it go to waste or be used?

How can one determine the credibility of information sources claiming scientific status?

Look for credible sources backed by evidence

Contrast heat processing requirements for low acid and acid foods.

Low acid: pH >5.3 (ex. peas, corn, meat, fish, poultry)...more risky; Acid: pH 3.7 to 4.6 (ex. Tomatoes, pears, pineapple)

Based on the limiting factors for growth and common knowledge about food, determine the type of microorganism that would likely be the initial cause of spoilage in a given food.

Mesophiles most common, then thermophiles or psychrophiles

Describe starch granules, including appearance and physical characteristics.

Microscopic packages within plant (parenchyma) cells, consisting of starch molecules arranged in an orderly fashion (but all unique). Used for plant storage prior to hydrolysis and glucose synthesis; from special form of plants called plastids (amyloplasts)

Explain how to prepare hard cooked eggs and the chemical reaction that results in yolk discoloration, including how to prevent it.

Must cover water at least 1 inch above eggs--boil, then cover and let stand, covered in hot water, for 15 min. for large eggs (plus or minus 3 minutes). Cool immediately with cold running water/ice. Yolk discoloration: Fe (yolk) + H2S (egg white) → FeS (black--appears green/gray against yolk). To prevent, cook in simmering (not boiling) water and cool rapidly--pressure reduction draws H2S outward.

State the various categories of emulsifying agents and how they work.

Natural emulsifiers: proteins, solid particles temporarily stabilize emulsions (spices), phospholipids (lecithin); synthetic emulsifiers: fatty acid esters (esterified to polar compounds--mono and diglycerides, and other non-glycerine polyol esters)

Explain the production of high quality pasta, including the type of wheat and flour.

Pasta: durum wheat milled into flour called semolina, which is combined with water to make a paste. Paste placed into extruder, which make pasta (formulation, processing, conditions, and type of dye determine pasta).

Define pasteurization and homogenization.

Pasteurization: heat treatment to destroy pathogens (high temp, short time OR ultra high temp). Homogenization: reduction of milk fat globule size to eliminate creaming (milk forced through small openings under pressure).

Define plasticity and state the factors that alter plasticity.

Plasticity depends on cohesion of solid (crystalline) particles; texture is affected by number and size of crystals. Triglyceride Crystal polymorphs: Ease of formation: a>B'>B; Stability, Melting point, and Size: a<B'<B

Explain the formation of pectin gels, including the role of pectin, acid and sugar.

Polymers of pectin associate via hydrogen bonding and hydrophobic interaction, entrapping water and forming a gel. Pectin: interacts at junction zones, forming a three-dimensional network; becomes the continuous phase. Water: is trapped in pockets within the gel network, becomes the dispersed phase. Acid: depresses ionization of pectin, reducing the negative charge. Increases pectin to pectin attraction (pH 2.8 to 3.4 needed for high methoxyl pectin or HMP). Sucrose: competes for water, decreases pectin to water interaction.

How can one determine the scientific validity of food safety concerns?

Primary (firsthand) vs. secondary (interpretative) sources; research based vs. anecdotal; risks vs. benefits

State the functions of proteins in foods.

Protein functions include: solubility (ex. Whey protein in sports drinks), nutritional value (ex. Soy protein in baked products), thickening or binding (ex. Egg proteins in breaded products), gelling (ex. Gelatin in jelly, congealed products like Jello), emulsification (ex. Milk proteins in ice cream), and foaming (ex. Egg white proteins in meringue).

Label the structures of a hen's egg; recognize names of proteins in yolk and white.

See notes :)

Define retrogradation and explain its consequences.

Retrogradation is the partial recrystallization of starch molecules after gelatinization and cooling. It causes products to become stale/hard (ex. Hard play-doh or leftover rice hardening). Reversible by heating in bread and H2O+heat in rice.

Draw the general reaction of baking soda with acid.

Sodium bicarbonate (2NaHCO3) + Acid (H+) →Na+ + Carbonic acid (H2CO3) + CO2 + H2O

State the two main starch molecules and describe their chemical structure.

Starch molecules inside granule: 1. amylopectin = branched, larger, 75%, millions of glucose units per molecule 2. amylose = straight, smaller, 25%, thousands of glucose units per molecule

Explain the drying processes discussed in class and their related advantages/disadvantages.

Sun drying: largest loss of nutrients and risk of bugs, etc. but no specific controls/equipment needed. Solar drying: more controlled to protect from rodents, etc. but need plexiglass/drying rack equipment. Spray drying: controlled environment but need to buy/maintain equipment. Freeze drying (LYOPHILIZATION): expensive but preserves quality and texture. Drum drying: more economical but lower quality than spray drying. Tunnel drying: controlled but need equipment. Extrusion drying: controlled but need equipment.

State the defects in baked goods containing too much or too little baking soda.

TOO MUCH: Too alkaline; soapy flavor and brown color or yellowing of flavonoids TOO LITTLE: Too acidic: not enough leavening; whitening can occur

State the temperature danger zone of bacterial growth and define the following terms: thermophile, mesophile, psychrotroph, psychrophile.

Temperature danger zone: 40-140 degrees Fahrenheit; thermophile: 40-70 deg C; mesophile: 10-50 deg C; psychrotroph: 0-30 deg C (fridge/freezer, or above); psychrophile: -10 to 20 deg C (ideally fridge, or freezer/below)

Explain recommended thawing procedures for meat and why refreezing is not recommended.

Thaw meat in the refrigerator, microwave, or in cold water replaced every half hour (NEVER at room temperature). Refreezing issues: increased microbial load, textural changes, off-flavors.

Graph the generic pH optimum and temperature optimum of enzymes.

The closer to optimum temperature and pH, the more enzyme activity.

Define iso-electric point.

The isoelectric point is the pH at which the positive and negative charges on an amino acid (or a protein) are in balance, i.e., have a net charge of zero.

Explain the concept of risk versus benefit.

There is no such thing as "zero risk;" the consumer decides on whether the benefits outweigh the risks, such as food borne illness, nutritional value, packaging/plastics, chemicals, GMO's, pesticides, organic, pasteurized or not, etc.

State the effect of chain length and degree of unsaturation on melting point.

UNsaturated fatty acids have a lower melting point than saturated fatty acids. The longer the carbon chain, the higher the melting point.

State where to find reliable information regarding home canning procedures and explain the precautions to take when processing low acid foods.

USDA Website or other official sources

Explain the proper packaging for frozen foods, including size and head space.

Use small containers; leave 10% head space for liquids and fill dry containers to capacity.

State the treatments used to preserve food.

Water removal (dehydrate/add solute), high temperature (thermal processing), low temperature (refrigeration/freezing), oxygen control (vacuum/inert atmosphere packaging), chemical preservatives (antimicrobials, antioxidants, acidifiers), aseptic conditions (sterile packaging), and other processes (irradiation, high pressure, Ohmic heating)

Explain whipped cream foam structure and formation.

Whipped cream foams are stabilized by rigid, fragile structure formed by clumping of fat globules at air-liquid interface: contains fat droplets with their emulsifiers; whipping incorporates air into liquid; film of water thins and fat globules orient in this film as air is incorporated; fat globule membrane is disrupted by whipping. Globules stick together, imparting stiffness to the foam.

Draw the overall reaction of carbon dioxide production via yeast; state the genus and species of yeast utilized in baked products.

Yeast: Saccharomyces cerevisiae; reaction: Glucose (C6H12O6) → Ethanol (2C2H5OH) + CO2

State the conditions which allow for growth of Clostridium botulinum spores.

pH > 4.6, water activity > 0.92, temperature 3 to 97 deg. C, low salt content, and protein/carbohydrate medium favor growth of C. botulinum

Draw the basic structure common to all fatty acids; recognize the structures of the following fatty acids: butyric, lauric, palmitic, palmitoleic, stearic, oleic, linoleic, linolenic.

see notes :)

Draw two amino acids joined together with a peptide bond; describe amino acid and protein structure.

see notes :)