NDFDS 250

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BYU91
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179744
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NDFDS 250
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2012-10-25 19:51:57
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food science
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NDFS 250 quiz 3
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  1. Starchy plants
    corn, wheat, rice, potato, tapioca, arrow root
  2. Startches are different
    Root startches are similar and grain starches are similar

    Just remember that starches are different 
  3. •Starch granules:
    Microscopic packages, within plant cells, of starch molecules arranged in an orderly fashion. Unique for each type of starch.
  4. Concentric striations on starch granules
    due to crystalline and noncrystallineregions
  5. •Amylose
    –Linear

    –Actually it’s a coil, but it’s still linear (no branching)
  6. •Amylopectin
    Branched
  7. startch ratio
    • Most starch granules contain about
    • 1/4 amylose and 3/4 amylopectin
  8. Amylose

    Glucose polymer with alpha 1, 4 linkages.

      Linear fraction of starch.
  9. Amylopectin
    Glucose polymer with alpha  1, 4 and alpha  1, 6 linkages.

    Branched fraction of starch; branches contain 20-25 glucoses
  10. •Gelatinization
    occurs (Starch granule absorbs water and swells)

    •Irreversible swelling

    • •Loss of birefringence (Maltese cross
    • disappears)

    •Rapid increase in viscosity
  11. Pasting
    •occurs (Additional swelling and amylose leaches into the cook water)

    •Thickness due to enlarged granules and amylose exudate
  12. Detecting
    Gelatinization
    • Uncooked starch granules under polarized light, exhibiting birefringence (Maltese cross)
  13. Gelatinization and Pasting of a Starch Slurry
  14. Effect of Ingredients on Gelatinization
    •Sugars
    •Granule swelling limited because sugar competes for H2O

    •Decreases thickness of gelatinized starch

    •Increases gelatinization temperature

    •Makes swollen granules more resistant to rupture
  15. Effect of Ingredients on Gelatinization
    •Acids 
    •Hydrolyze starch, reducing viscosity

    •(Slight hydrolysis may open granule producing a thicker paste)
  16. Effect of Ingredients on Gelatinization
    •Salts
    •Generally not much effect; may increase gelatinization temp.
  17. Effect of Ingredients on Gelatinization
    •Fats and surfactants
    • •Fats “water proof” the granules so that water cannot penetrate
    • easily.

    •Surfactants markedly increase the gelatinization temperature
  18. syneresis
    Liqiud draining from a gel.
  19. Retrogradation
    (re-crystallization of starch molecules) affects texture
  20. Why is starch modified for use as a food
    ingredient? frozen food
  21. Why is starch modified for use as a food
    ingredient? Confections
  22. •Acid-modified Starch
    –Thin-boiling starch prepared by heating starch below its gelatinization temperature in dilute acid.

    –When heated, it’s low in viscosity; this allows for pumping while hot

    –When cooled, a clear gel forms; used in gum drops.
  23. •Cross-linkedstarches
    –Starches containing molecules that have been cross-linked with one another with ether or ester linkages.

    –Cross-linking minimizes breakdown of the starch in acid.

    –Good for frozen foods
  24. •Pregelatinized starch
    –Starch that is precooked and dried, i.e.,instantized; dispersible in cold water

    –Used in instant pudding.
  25. Functions of fat in food
    •Crystal modification
    •Ice in ice cream, sucrose in fudge
  26. Functions of fat in food
    •Medium for heat transfer
    •Fried foods
  27. Functions of fat in food
    •Tenderness in baked products
    •Limits gluten development by coating flour particles in biscuits, muffins, pastry, cakes.
  28. Functions of fat in food
    •Flavor and tenderness in protein foods
    •Cheese, ground beef
  29. Functions of fat in food
    •Body and mouthfeel
    •Smoothness of cream, mayonnaise

    •Moist sensation when crystals melt in mouth
  30. •Fats and oils
    chemistry
    •Fats are solid at room temperature

    •Oils are liquid are room temperature

    •Two terms are often used interchangeably
  31. •Fatty acids
    chemistry
    •The building blocks of fat made of hydrocarbons

    •Saturated and unsaturated
  32. •Glycerides
    chemistry
    •Fatty acids esterified to Glycerol

    •Synonym: acylglycerols

    •1 fatty acid + glycerol = monoglyceride

    •2 fatty acids + glycerol = diglyceride

    •3 fatty acids + glycerol = triglyceride
  33. Butyric
    HOOC CH2 CH2 CH3 or H3C CH2 CH2 COOH    
  34. Lauric
    HOOC (CH2)10 CH3
  35. Palmitic
    HOOC (CH2)14 CH3
  36. Palmitoleic
    HOOC (CH2)7 HC = CH (CH2)5 CH3
  37. Stearic
    HOOC (CH2)16 CH3
  38. Oleic
    HOOC (CH2)7 HC = CH (CH2)7 CH3
  39. Linoleic
    HOOC (CH2)7 HC = CH CH2 HC = CH (CH2)4 CH3
  40. Linolenic
    HOOC (CH2)7 HC = CH CH2 HC = CH CH2 HC = CH CH2 CH3
  41. Glycerol
  42. Polymorphism
    More than one crystal form
  43. Consistency of fats
    Plastic range
    Temperature range over which a fat exhibits plasticity

    Fats with a wide plastic range have some crystalline fat at elevated temperatures and some liquid fat at low temperatures

    • Important
    • for shortening

    • Temperature
    • range where there is some crystalline fat present 
  44. Consistency of fats
    Methods of altering plastic range (plasticity)
    Interesterification

    Hydrogenation

    Mixing different fats

    Adding emulsifiers (superglycerination)
  45. •Hydrogenation
    •Addition of H2 to the double bonds of unsaturated fats, converting them to saturated fats.

    • •The oil is heated with a finely divided nickel catalyst.  The
    • system is evacuated and H2 gas is admitted.

    •Converts unsaturated fats to saturated fats, changing textural properties and improving stability.
  46. •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.

    •The molecules become more heterogeneous, resulting in smaller crystals and a wider plastic range.
  47. •Superglycerination
    •Process of incorporating 3-6 % emulsifier (glyceryl monostearate) into shortening to improve its baking qualities.
  48. Rancidity 
    Off-odors and off-flavors due to fat breakdown

    Two types:

    Oxidative rancidity, due to lipid oxidation (autoxidation)

    Hydrolytic rancidity, due to lipid hydrolysis

    Both types may be caused by enzymes technically are not, enzymes destroyed/slowed down

    Oxidative – lipoxygenase

    Hydrolytic – lipase

    Can occur even when only small amounts of fat are present

    A major cause of food deterioration and shortened shelf life
  49. Oxidative Rancidity
    occurs at the double bonds
  50. Hydrolytic rancidity 
    occurs when short fatty acids are hydrolyzedfrom the glycerol
  51. Antioxidants
    • Antioxidants
    • are substances that delay rancidity

    • Bind
    • metal pro-oxidants (EDTA)

    • Stop
    • free radical reactions
    • Butylated
    • Hydroxyanisole  (BHA)
    • Butylated
    • Hydroxytoluene (BHT)
  52. Tertiary Butylhydroquinone

    (TBHQ)
  53. Propyl Gallate (PG)
    • Alpha-tocopherol
    • (Vitamin E)
  54. Vegetable
    Oil
    Oil bearing portion of seed, etc. is cleaned, ground and tempered

    Pressing or solvent extraction

    Removes the oil

    Refined with alkali to remove free fatty acids and non-fatty material

    Bleached

    • with
    • fuller’s earth to lighten color

    Deodorized

    • by
    • steam distillation in a vacuum to remove volatiles.
  55. Shortenings
    • After vegetable oil is bleached with fuller’s earth, the oil
    • to be made into shortening is then:
    • Hydrogenated

    Deodorized

    Emulsifier added and antioxidant if desired

    Chilled and agitated to produce desired texture (crystal size)

    Whipped to aid in desired texture
  56. Margarine
    Usually soybean oil is used, prepared with partial hydrogenation

    Addition of:

    NaCl

    Na benzoate

    Vitamin A, Vitamin D,

    • Emulsifiers:
    • lecithin, or mono- or diglycerides

    Diacetyl for flavor, and Annatto for yellow color (all optional but almost universal)

    Melted fat is agitated or churned with skim milk that was pasteurized and cultured with bacterial starter.
  57. Lard
    Lard comes from the fatty tissue or fat back of pork, cut into small pieces.

    Rendered – heated with or without water to remove fat

    Prime steam lard is heated with water

    Kettle rendered lard is without the addition of water in an open, steam-jacketed kettle.  Has a cooked flavor desired by some.

    Antioxidant added.

    • Bleaching,
    • hydrogenation, deodorization, emulsification, and interesterification

    • Additional
    • modifications to improve baking performance
  58. Butter
    Cream and milk separated by centrifugation.

    Pasteurized to inactivate enzymes and kill microbes of pathogenic nature.

    Starter culture added to produce lactate.

    Ripened a few hours

    Churned so that buttermilk separates from clumps of butterfat.

    Oil in water cream emulsion changes to water in oil emulsion of butter during churning; inversion.

    Buttermilk is drawn off and butter worked and salted

    worked to distribute salt and to remove excess water.

    Natural production of diacetyl and free fatty acids contribute to flavor.
  59. Sol
  60. Oil in Water (O/W)
    (Most food emulsions) 
  61. Water in Oil (W/O)
    butter and margarine
  62. Emulsifier
  63. A molecule that has two functional areas, one nonpolar or hydrophobic and  one polar or hydrophilic
  64. Surfactant(surface active agent)
    Substance that lower the interfacial tension of a liquid 
  65. Emulsifier
  66. emulsifier deffinition 
    • An emulsifier, such as a monoglyceride, has both polar regions and non-polar regions on the same molecule.  The
    • non-polar tail is attracted to the oil (discontinuous phase) and the polar head is attracted to the water (continuous phase). This allows the two phases to associate into an emulsion.
  67. Surface tension
    Phenomenon due to unequal forces exerted on molecules at a surface

    Forces acting on molecules in the interior and on the surface of a liquid
  68. Interfacial tension
    Same phenomenon existing at interface between two liquid phases, e.g., oil and water
  69. Emulsions greatly increase interfacial area:
    a – 1 cm2 interfacial area

    • b – 300 m2 interfacial area when oil
    • droplets are   0.1 μm in diameter
  70. emulsifier formation
  71. •Creaming 
    •Separation into two emulsions

    •Unhomogenized milk or whipping cream in the refrigerator
  72. •Inversion
    •Change of emulsion type: o/w     w/o

    •Churning of cream to butter 
  73. •Coalescence 
    •Merging of droplets

    • •French dressings that are temporary emulsions or margarine in
    • a hot fry pan
  74. Causes of Emulsion Instability
    Salt
    – increases surface tension of water
  75. Causes of Emulsion Instability
    •Agitation
  76. (e.g., during product distribution)
  77. Causes of Emulsion Instability
    •Drying
    – removes a protective layer around droplets
  78. Causes of Emulsion Instability
    •Heating
    – evaporates the water phase
  79. Causes of Emulsion Instability
     •Freezing
  80. – removes the water phase as crystals and can crystallize the fat phase
  81. Causes of Emulsion Instability
    •Type of emulsifier
     (e.g., solid particles not as stable as monoglyceride)
  82. Causes of Emulsion Instability

    •Insufficient
    emulsifier 
  83. •Mayonnaise
    •³ > or= 65 % by weight of oil
  84. •Salad Dressing
    •³ 30% by weight of oil

    • •Not less than 4% liquid egg yolk (or
    • equivalent yolk ingredients)
  85. •French Dressing
    •³ 35% by weight of oil

    • •May include egg or emulsifier, but not
    • more than 0.75%
  86. pectinase
    fruit juice clarification 
  87. Amylase
    —flours for bread 
  88. Lactase
    —low-lactose milk
  89. Chymosin
    Cheese
  90. Papain
    meat tenderizer
  91. Glucose
    isomerase
    High fructose corn syrup
  92. Invertase
    candies
  93. Glucose
    oxidase
    glucose removal to prevent   Maillard browning 
  94. Protein Gels
    -Gelatin (e.g. Jello)

    -Casein (e.g. cheese curd, custard)
  95. Pectin Gels
    -Jams and Jellies

    -Candies
  96. Starch Gels 
    -Puddings

    -Candies (gum drops)
  97. Collagen
    is a protein in animal tissue that exists as a triple helix formed from 3 left handed helices
  98. Gelatin commercial forms
    1.Fine powder
    (flavored/sweetened gelatin) – solubilizes in hot water
  99. Gelatin commercial forms
    Coarse powder(unflavoredgelatin)
     presoak in cold water 4-8 mins, then add hot water
  100. Gelatin commercial forms
    Sheets or Leafs –(unflavored)
    - presoak in cold water 4-8 mins), then add hot water (has lighter color, cleaner flavor than coarse)
  101. gelatonin formation
    žGelatin solubilized/dispersed in hot water

    žAs gelatin sol cools, viscosity increases due to molecular interaction between polymers

    žWith further cooling viscous liquid changes to viscoelastic solid
  102. •1-2% gelatin is required for gelation
    •Too much:  gel is stiff, rubbery

    •Too little: gel converts to sol

    •Just right: gel holds shape, yet tender and quivery
  103. •Fruit and Vegetable Gels
    •Add fruit (or vegetable) after gel partially thickens

    •Prevents floating

    •Do not add raw figs, kiwi or pineapple

    •Proteases hydrolyze peptide bonds of gelatin
  104. •Whips, sponges, creams
    •Foam/Gel combination

    •Make gelatin sol

    •Cool to 10 C and allow to thicken but not set

    •Beat to incorporate air and make foam
  105. Pectin Sources 
    žPrimarily extracted from citrus albedo and apple pomace, both agricultural waste products
  106. Pectin structure
  107. Pectin molecule
    žα-D-galacturonic acid (and its methyl ester)

    žJoined by alpha-1,4-glycosidic linkages
  108. Esterases
    ž(a type of hydrolase that cleaves esters)

    Pectin methyl esterase activity increases during natural maturation of fruits
  109. Pectin gel components and their functions
    •Pectin
    •Forms three-dimensional network that entraps water
  110. Pectin gel components and their functions
    •Water
    •Solvent for other components
  111. Pectin gel components and their functions
    •Acid
    • •Decreases ionization of carboxyl groups to allow for junction
    • zone formation

    •pH 2.8 to 3.4 needed for HMP
  112. Pectin gel components and their functions
    •Sucrose
    •Disrupts water around methyl groups, allowing junction zone formation through hydrophobic interaction

    •Competes for water, partially dehydrating pectin and allowing junction zone formation through H-bonding between pectin polymers (instead of pectin-water) 
  113. žEffect of acid  Pectin
    If pH too high, too many negative charges exist and repulsion results – weak or no gel

    If pH is very low, then association is too tight and a brittle gel is formed with water eventually being expelled through syneresis
  114. HMP
    žGel formed by balance of acid and sugar

    pH 2.8-3.4

    40 to 70 % sugar  (Usually 60-65%)
  115. LMP
    žJunction 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

    • ¡Application:
    • Low
    • calorie jams and jellies
  116. Jelmeter
    A Jelmeter measures viscosity of a pectin extract, which indicates its sugar-carryingcapacity.

    The Jelmeter is calibrated to read in cups of sugar required for each cup of extract.
  117. Speed of gel formation with rapid and slow set HMP 
  118. Jelly
    A soft, elastic food product containing pectin from fruit juice
  119. Marmalade
    žA tender jelly with small pieces of fruit distributed evenly throughout, commonly contains citrus
  120. Jam
    žA viscous food product containing pectin from crushed or ground fruit

    Tends to hold shape, but less firm than jelly
  121. Conserves
    žJams made from mixtures of fruit including citrus, raisins, and sometimes nuts
  122. Preserves
    žWhole or large pieces of fruit suspended in a thick syrup
  123. yolk proteins
    •Livetin

    •Phosvitin

    •binds certain metal ions

    •contains 10% phosphorus

    •4% of egg yolk solids
  124. egg white proteins
    •Ovalbumin

    •Glycoprotein

    •Conalbumin

    •Ovomucin 

    •Associated with thick white; fibrous

    •Glycoprotein

    •Ovomucoid (11%)

    •Glycoprotein; Not coagulated by heat

    •Trypsin inhibitor

    •Lysozyme (3.5%)

    •Lyses cell walls of gram (+)

    •Contributes to whipping
  125. Candling
    A quality test where eggs are rotated over bright light in dark room

    • Reveals condition of shell, size of ai cell, and size, distinctness, and mobility of the yolk; also detects blood
    • spots and meat spots
  126. Processing Eggs: Pasteurization
    Egg white; 134°F for 3.5 to 4 minutes

    Whole egg: 140-143°F for 3.5 to 4.0 minutes
  127. freezing eggs
    • lOne of the following additives must be
    • added to yolk or whole egg before freezing

    lNaCl (1/2 tsp/cup)

    lSugar (1-2 Tbs/cup)

    lCorn syrup (1 Tbs/cup)

    l  Why?

    lWithout additives, yolk has a lumpy texture after thawing

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