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FOOD 2010 Unit 3.pdf

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Food Science
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FOOD 2010
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Massimo Marcone

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FOOD*2010     UNIT  3  CHAPTER  SUMMARY   Chapter  3   3.4   Because  of  sugars  and  its  link  to  diabetes,  weight  gain  and  tooth  decay,  alternate   sweeteners  have  been  developed.    They  can  be  nutritive  (calorie)  or  nonnutritive   (non-­‐calorie).   • Sugar  Alcohols:  examples-­‐  isomalt,  mannitol,  sorbitol,  are  found  naturally  in   fruits.    Can  be  manufactured  by  hydrogenating  sugars.    Sugar  alcohols   provide  a  sweet  taste  and  cooling  sensation.   • acesulfame  potassium(Sunette)  is  heat  stable  and  is  used  in  baked  products.     Highly  sweet  but  bitter  after  taste.    No  calorie  since  it  is  not  metabolized  and   excreted.     • Aspartame(Nutrasweet,  or  Equal).  Composed  of  aspartic  acid  and   phenylalanine.    Its  sweetness  is  almost  200  times  that  of  sucrose  and  is   therefore  used  only  in  small  quantities  and  does  not  contribute  calories.     Some  people  are  sensitive  to  aspartame  even  in  small  amounts   • Saccharin  was  the  first  artificial  sweetener  (1878).  intensely  sweet  but  bitter   aftertaste.    Found  to  cause  cancer  in  rats.    In  Sweet’N  Low  products   • Sucralose  (Splenda)  600  times  sweeter  than  sucrose.    No  aftertaste.  no   calories  or  tooth  decay.    Created  through  replacing  two  OH  groups  with   Chlorine  atoms.   Fat  replacers  are  important  for  human  health  and  nutrition.   • Carbohydrate-­‐based  fat  replacers  ingredients  are  plant  polysaccharides.     They  thicken  foods  and  add  bulk,  provide  mouth-­‐feel  similar  to  fat.    Can   provide  calories  or  none  like  cellulose,  which  is  not  digestible.    They  can   withstand  heat  and  are  used  in  meat  products.    Examples  include  fibers,   gums,  carrageen,  dextrins,  Oatrim,  starch  gels.   • Protein-­‐based  fat  replacers  can  be  blended  with  gums  to  form  gels.    Provide   structure  and  function  similar  to  fats.    Proteins  that  are  low  in  molecular   weight  added  to  cheeses.    Microparticulation  is  a  food  processing  method   that  reduces  the  particle  size  of  a  substance.    Microparticulated  egg  and  milk   proteins  contribute  to  the  creamy  mouth-­‐feel  of  fats  with  low  calorie.   Isolated  soy  protein  is  used  in  meat  products.    Most  cannot  be  used  in  high   temperatures  without  it  losing  function   • Fat-­‐based  fat  replacers  contain  some  fatty  acids  found  in  regular  food  fats   and  can  mimic  their  characteristics  of  flavor,  baking  and  frying  stability  and   shelf  life.    They  have  shorter  chains,  with  fewer  carbon  atoms.    Caprenin  used   in  cocoa  butter.    Salatrim  used  in  chocolate  products.    All  containing  shorter   fatty  acid  chains.    In  Olestra,  the  fatty  acids  are  attached  to  a  sucrose  which   allow  it  to  pass  through  the  body,  therefore  noncalorie;  it  is  also  stable  at   high  temperatures.,  used  in  potato  chips.    However  Olestra  can  cause   gastrointestinal  symptoms  like  cramping  and  loose  stool.       Chapter  4   4.1   • compounds  are  made  from  elements  and  the  important  compounds  in  food   science  are  organic  compounds.    These  elements  are  :  carbon,  hydrogen,   oxygen,  sometimes  sulfer,  nitrogen  and  phosphorous.   • food  systems  are  mixtures,  for  example-­‐  solution,  dispersion  and  emulsion     • symbols:  one  or  two  letters  to  represent  the  element  on  the  periodic  table  (H   for  hydrogen,  Cl  for  chlorine)   • Formulas:  elements  present  in  a  compound  represented  by  their  symbols           (  hydrochloric  acid  –  HCl)   • atom  electrons  are  organized  in  energy  layers/orbits  where  the  outermost   orbital  is  the  valence  shell.    A  complete  valence  shell  is  chemically  stable   Ø Chemical  bonds   o covalent  bonds-­‐sharing  one  or  more  pairs  of  electrons  between   atoms  filling  their  valence  shells.   o ionic  bonds  are  a  transfer  of  electrons  between  atoms,  filling  their   valance  shells   o hydrogen  bonds:  a  covalent  bond  between  hydrogen  and   electronegative  elements  with  unequal  sharing  of  electrons   o intermolecular  bonds-­‐  between  different  molecules   o intramolecular  bonds-­‐  within  the  same  molecule   4.2   Ø Reactions   • composition  –  A  +  B  èAB   • decomposition-­‐  ABè  A  +  B   Enzymes   • only  occur  in  living  systems,  plants  and  animals  tissue  and  microorganisms   in  food.   • can  change  colour,  texture,  flavor,  and  odor  during  storage  and  use  of  foods   • enzymes  are  special  protein  molecules  that  are  biological  catalysts-­‐  they   cause  chemical  reactions  to  speed  up.       • Activity  occurs  when  a  substrate  joins  to  an  enzymes  active  site  creating  an   enzyme-­‐substrate  complex,  after  reaction  a  product(s)  are  formed  and   separate  from  the  enzyme  (how  enzymes  lower  the  activation  energy  for  a   reaction  to  take  place)   • they  work  best  under  specific  ranges  of  temperature  and  pH  and  substrate   concentrations.   • Zero-­‐order  reaction:  scientists  keep  a  high  concentration  of  substrate  to   maintain  a  constant  level  of  ES  complexes,  resulting  in  the  formation  of   products  in  a  linear  function  of  time,   • First-­‐,  Second-­‐,  and  Third-­‐  order  reactions  occur  slower           Reactions  involving  enzymes   • enzymatic  hydrolysis  reaction,  enzyme  breaks  large  food  molecules  apart   into  smaller  fragments.    Hydrolic  enzymes  are  carbohydrates   • enzymatic  oxidation  reaction  occurs  when  oxygen  is  added  to,  or  hydrogen   or  electrons  are  removed.   • enzymatic  reduction  is  the  gaining  of  one  or  more  electrons,  gaining   hydrogen,  or  losing  oxygen  from  the  structure  of  a  food  molecule  in  the   presence  of  an  active  enzyme   • a  polymer  is  a  high  molecular  weight  molecule  created  by  the  repetitive   reaction  of  hundreds  of  thousands  of  low  molecular  weight  units   • polymerization:  a  type  of  reaction  where  many  monomers  are  joined   together  end  to  end   Nonenzymatic  reactions   Ø chemical  reactions  that  do  not  depend  on  enzymes  include:  addition,   oxidation-­‐reduction,  hydrolysis  and  condensation  reactions.   • addition  reactions  take  place  in  organic  molecules  that  possess  double  or   triple  bonds  between  carbon  atoms  (double  bonded=unsaturated.    addition   of  hydrogen=saturated)   • reducing  agent:  a  substance  that  causes  another  substance  to  be  reduced,   while  the  reducing  agent  itself  becomes  oxidized  in  a  reaction   • oxidizing  agent:  a  substance  that  causes  another  substance  to  become   oxidized,  while  the  oxidizing  agent  itself  becomes  reduced  in  a  reaction.   • condensation:  separate  reactant  molecules  are  linked  together  by  special   chemical  bonds(water  is  formed  as  a  product)   • hydrolysis:  water  molecules  split  large  molecules  to  smaller  units  (opposite   of  condensation  reaction)   4.3  Functional  Groups   Note:  many  atoms  exist  as  ions  that  carry  either  negative  or  positive  charges.   (sulfide  ion:  S-­‐2;  Ammonium  ion:  NH4+)   Ø Alcohol  Group:  R–  OH   o OH  –  hydroxyl   o name  endings  (-­‐ol)                                  H   Ø Aldehyde:      C=O                    R   o Oxygen  double  bonded  to  carbon  and  the  rest  of  the  molecule  (R)   o  name  ending  (-­‐al)     Ø Amino:  R-­‐NH2   o functional  group/  name  ending  (-­‐amine)     Ø Carboxylic  Acid:  O=C-­‐OH                                      R   o Carboxyl  or  acid  group   o COOH  carbon  double  bond  (carbonyl)  and  alcohol  (hydroxyl)  plus  (R)   side  chain   Ø Ester:    R   C=O   O   R’   o carbonyl-­‐oxygen-­‐carbon  system   o generally  fatty  acids   o give  flavors  and  aroma  to  foods     Ø Ketone:      R          C=O          R’   o contains  carbonyl  group  between  side  chains   o name  ending(-­‐one)     Ø Methyl:  R-­‐CH3   o important  in  the  biosynthesis  of  certain  bioactive  compounds   o molecules  are  “methylated”  with  CH3   o examples-­‐methionine,  methanol        R                    O   Ø Phosphate:    O=P-­‐OH      OH   o Phosphates  are  salts  of  the  inorganic,  phosphoric  acid,  H3PO4   o Phosphates  have  two  hydroxyls,  a  carbonyl,  and  an  oxygen  bond   which  is  also  bonded  to  a  side  chain   o used  in  food  processing.(  in  meats  it  improves  texture,  juiciness  and   water-­‐holding  capacity)     Ø Sulfhydryl:  R  –  SH   o similar  to  an  alcohol  group   o compounds  containing  this  are  called  thiols   o they  are  easily  oxidized  and  yield  disulfides   o used  in  gluten  structure   4.4   Functional  properties  are  the  physical  and  chemical  properties  of  food  molecules   that  affect  the  behavior  in  foods  during  fermentation,  processing,  and  storage.     Determine  by  the  molecules  function  groups   Ø Functional  properties  of  water  in  foods   o component  of  colloidal  dispersions   o fat-­‐replacer  ingredient   o heat  transfer   o medium  for  microbial  growth   o plasticizer(a  substance  that  when  added  to  food  systems,  makes  it   softer)   o product  moisture   o solvent   • water  molecules  are  dipole  because  of  the  partial  positive  hydrogen  atoms   and  partial  negative  oxygen.    the  Dipole  affects  waters  characteristics  like   boiling  pt,  freezing  pt,  and  vapor  pressure,  aswell  as  electrostatic  attraction   to  each  other.   • acts  in  the  process  of  hydration  as  a  solvent.    amphiphilic  molecules  (both   hydrophilic  and  hydrophobic)  form  micelles-­‐clusters  of  molecules  where   hydrophobic  group  is  directed  away  from  water.    this  is  called  noncovalent   interactions   • moisture-­‐  amount  of  water  in  food   o free  water-­‐seen  and  felt,  used  as  solvent   o absorbed  water-­‐associated  with  intermolecular  hydrogen  bonds   around  hydrophilic  food  molecules   o bound  water-­‐water  of  hydration,  exists  in  tight  crystalline  structure,   water-­‐ion  and  water-­‐dipole  interactions  (fails  to  freeze  at  0’C)   Water  activity:  the  measure  of  the  availability  of  water  molecules  to  enter   into  microbial,  enzymatic,  or  chemical  reactions   • this  determines  shelf  life  of  food   • it  is  calculated  as  a  ration  of  water  vapor  pressure  of  the  substance  divided   by  the  vapor  pressure  of  pure  water  at  the  same  temperature  (Aw=P/P0)   • relative  humidity  is  calculated  by  multiplying  water  activity(Aw)  by  100   • moisture  sorption  isotherms  are  graphs  that  interrelate  the  water  content  of   foods  with  its  water  activity  at  a  constant  temperature   • an  emulsion  is  a  type  of  colloidal  dispersion,  a  system  containing  two  liquids   or  phases  that  normally  do  not  mix:  a  dispersed  phase  and  a  continuous   phase(water  can  act  as  either  in  certain  situations)   4.5   Typical  food  acids  are  carboxylic  or  organic  acids  containing  the  carboxyl  (COOH)   group.    these  acids  differ  in  structure  depending  on  the  number  and  arrangement  of   carbon,  oxygen  and  hydrogen  atoms.    This  affects  their  physical  and  chemical   properties   o adding  acids  to  food  can  cause  hygroscopicity-­‐  allowing  the  it  to  remain  free-­‐ flowing,  preventing  the  moist  particles  from  clumping.   o food  acids  like  fumaric  and  malic  are  considered  weak  acids.    acids  that  are   strong  have  a  large  amount  of  dissociated  ions  and  has  a  great  effect  on  the   pH.     o weak  acids  have  a  small  dissociation  or  ionization  constant  (Ka)  given  for  the   reaction:      HA   +    -      A o strength  of  the  acid  is  directly  proportional  to  the  value  of  its  Ka.    Humaric   acid  has  two  acid  groups  and  higher  ionization  constant  and  is  therefore  a   stronger  acid  than  malic.   o mathematically  pKa  is  the  inverse  of  Ka.    therefore  a  lower  pKa  means  a   stronger  acid.   o adding  fumaric  acid  to  flour  dough  can  soften  it.    the  amino  acid,  cysteine  in   the  flour  contains  the  sulfhydryl  group.    When  it  becomes  oxidized  overtime   (loses  hydrogen)  the  cysteine  joins  to  create  disulfide  bonds(-­‐S-­‐S-­‐)  and   tightens  the  dough’s  structure.    the  adding  of  fumaric  acid  will  break  these   bonds  through  the  donation  of  H+.   o organic  salts  are  formed  when  an  organic  acids  carboxyl  group’s  hydrogen   atom  (COOH)  is  replaced  with  a  metal  ion  such  as  sodium,  calcium  or   potassium.  when  these  salts  ionize  they  act  like  neither  an  acid  or  a  base   affecting  flavor  and  quality  of  the  food.   o a  buffer  is  a  solution  of  a  weak  acid  and  its  salts  at  a  pH  where  the  solution   has  the  ability  to  maintain  that  pH  when  quantities  of  a  base  are  added.    an   example  of  this  system  are  lactic  acid  and  lactate.   o Leavening  refers  to  the  gas  production  of  yeast  fermentation,  by  the  reaction   of  an  acid  with  baking  soda  in  batter  and  dough  products,  or  by  the  heating  of   salts.  It  is  the  “rise”  of  the  product.    during  fermentation,  carbohydrates  are   converted  to  CO2  and  ethanol.    Leavening  acids  generate  hydrogen  ions   facilitate  the  release  of  CO2  in  the  sodium  bicarbonate  causing  the  expansion   of  the  product  due  to  the  increased  pressure.       o Two  important  properties  of  leavening  acids  are  neutralizing  value(NV)  and   dough  reaction  rate.    NV  is  the  amount  of  sodium  bicarbonate  that  can  be   neutralized  b  100  parts  by  weight  of  leavening  acid.    Dough  reaction  rate   refers  to  the  speed  of  the  reactivity  of  a  leavening  acid  in  a  dough,  as  the   amount  of  CO2  is  released.   o Sodium  bicarbonate  (baking  soda)  (NaHCO3)  ionizes  when  reacted  with   leavening  acids  to  produce  bicarbonic  ions  (HCO3-­‐)  which  are  converted  into   carbonic  acid(H2CO3)  which  then  dissociates  to  produce  CO2.   o Baking  powder  is  a  mix  between  baking  soda  and  acid(single  acting  or   double  acting  types)     4.6   o The  dissociated  hydrogen  ions  in  a  product  is  termed  pH.    pH  =  -­‐  log[H+]   scale  from  0  to  14.  value  less  than  7=acidic  (high  hydrogen  conc.).    value  higher   than  7  basic/alkaline.  7=neutral   o titratable  acidity  is  a  measure  of  the  total  acidity  in  a  sample,  both  as  free   hydrogen  ions(dissociated)  and  as  hydrogen  ions  still  bound  to  acids   (undissociated).    Measured  by  the  addition  of  a  base  of  known  concentration   to  a  sample  until  a  predetermined  end  point  is  reached.  (color  change  at   certain  pH  from  added  indicator).      This  process  is  used  in  the  dairy  industry   to  monitor  fermentation.   o an  acid  food  is  on  that  has  a  pH  of  4.6  or  below.   o natural  pH  is  the  pH  prior  to  processing     o Acidified  foods  are  low-­‐acid  foods  to  which  acids  are  added  final  pH  =or<  4.6   low  acid  food  originally  have  pH>4.6.      (example  of  acidified  food  are  pickles)   o equilibrium  pH  is  when  solid  and  liquid  parts  have  the  same  pH   o Fermented  foods  are  low  acid  foods  subjected  to  the  actions  of  certain   microorganisms  (fermented  foods=pickles)     • Food  systems:  a  dispersion  containing  two  phases:  a  continuous  phase  and  a   dispersed  phase-­‐  solids,  liquids,  gases   • solutions:  are  homogeneous  mixtures  in  which  one  substance  (  the  solute)  is   dissolved  in  another(  the  solvent)   • solubility:  is  the  maximum  amount  of  solute  that  dissolves  in  a  specified   volume  of  solution  at  a  specified  temperature.   • food  colloids:  are  surface  active  ingredients  such  as  fatty  acids,  glycerides,   phospholipids,  polysaccharides,  and  proteins.   • emulsions:  is  a  colloidal  dispersion  of  two  liquids,  usually  oil  and  water,  that   are  immiscible(not  mixable)   • Emulsifiers  such  as  monoglycerides,  phospholipids,  and  sorbitan   monostearates  are  amphiphilic  molecules,  which  means  they  contain   hydrophilic  and  hydrophobic  regions  in  their  structure   • colloidal  dispersion  example:  gel:-­‐liquid  -­‐solid,  foam:-­‐gas-­‐liquid.     Chapter  5   5.1   Fructose  and  glucose  are  single  carbohydrate  units  (monosaccharides)   sucrose  and  lactose  are  two  carbohydrate  units(disaccharide).    Simple  sugars  are   also  called  origin  alcohols  since  they  contain  a  carbon  attached  to  and  alcohol  (-­‐OH)   group.   Monosaccharides  that  contain  3  carbon  atoms  in  their  structure  are  called  trioses;   5=pentoses;6=hexoses.    Hexoses  can  be  identical  in  chemical  formula  but  slight   differences  in  the  location  of  the  functional  groups  causes  differences  in  functional   properties,  including  sweetness  and  solubility.   • glucose  is  the  most  common(aka  dextrose).  its  considered  an   aldose(aldehyde)  b/c  of  the  carbonyl(-­‐C=O)  group  at  carbon  1.   • Fructose  is  a  ketone  because  of  the  carbonyl  group  at  c2   • galactose  occurs  in  disaccharide  lactose   • monosaccharides  can  exist  in  straight  chain  or  Fischer  projection  molecules   and  ring  or  cyclic  Haworth  projection  form.   • in  solution  C5  (alcohol  grp)  and  C1(aldehyde  grp)  undergo  an  intramolecular   cyclization  rxn  which  joins  C1  to  C5  to  form  a  closed  ring  eliminating  the   carbonyl  group  and  leaving  the  OH  group   • Disaccharides  are  two  monosaccharides  joined  together  by  a  glycosidic  bond.     include  sucrose,  lactose,  and  maltose.    sucrose(table  sugar)  contains  glucose   and  fructose  linked  between  the  aldehyde  group  of  the  C1  atom  of  glucose   and  the  ketone  grp  of  C2  atom  fructose.    Lactose  is  composed  of  glucose  and   galactose.    Maltose  is  composed  of  two  glucoses.   • the  alcohol  grp  (-­‐OH)  is  important  for  solubility  and  sweetness.    The  carbonyl   grp(-­‐C=O)  is  important  for  reducing  activity  and  the  Maillard  browning   reaction-­‐causes  colour  and  flavor  change.    Alcohol
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