NDFS 251 exam 1

Card Set Information

NDFS 251 exam 1
2012-09-30 23:58:44
food science

Dr. Dunn's NDFS 251 exam 1
Show Answers:

  1. Precision
     is the degree to which a single sample would return the same value when tested multiple times; repeatability. 
  2. Accuracy
    a measure of how close the obtained value 
  3. `
  4. Discrimination Test 
    or difference tests show whether people can tell a difference between two products
  5. triangle test
    • Select the odd/different sample.
  6. Duo-Trio
    • Select the sample that matches the reference. 
  7. Paired - Comparison 
    • Are the samples the same or different?
  8. Affective Tests
    • or "hedonic scale" tests indicate people's opinion of a product and/or attributes.
    • ex. Just about right 
  9. Descriptive tests 
    typically use trained panelists and go into detail  about specific elements of the product
  10. QDA Qualitative Descriptive Analysis
    A specific approach to descriptive testing where panelists are trained to identify specific attributes and to indicate attribute strengths on a continuum.  Used to make subjective analysis more objective.
  11. True Solution
    composed of molecules of low molecular weight, which, when added to water below their saturation point, dissolve completely to form clear non-opaque solutions.
  12. Colloidal Dispersions
    composed of molecules of higher molecular weight, but have either enough interaction with water or enough repulsion from each other to keep them from settling out.  normally translucent or partially cloudy.  can form gels.
  13. Suspensions
     consist of compounds of high molecular weight, whuch do not have sufficient intermolecular forces to stay uniformily dispersed on a permenant basis.  tyoically settle out over time, some fairly quickly and others over a more extended period.
  14. Conduction
    cooling direct transfer of energy from molecule to the next, without involving significant motion or flow.  Energy moves laterally from one layer to the next, which takes considerable time.
  15. Convection cooling
    involves an element of motion or flow, which allows an indivdual high-energy molecule ( heated) to be exposed to many unheated molecules in succession, so that the heat energy is transfered to many different molecules fairly rapidly.
  16. Evaporative cooling
     involves transfer of energy to ambient air during phase change of water from liquid to gas.
  17. Specific Gravity
     at same temp.
  18. Reducing sugar, Beenedicts reagent
    • Cu2+ + RCHO --> RCOO- + Cu2O(red) 
    • all sugars are reducing sugars except sucrose
  19. Invert sugar
    Sucrose + H2O - invertase acid-> fructose/glucose
  20. Brix
    defined as percent sugar (by weight) dissolved in an aqueous solution.  Since many juices and other foods are comprised mainly of water and sugar, "brix" is often used synonymously with dissolved solutions.  can be measured by refractive index.( refractometer) 
  21. Crystalline candies
    • made by heating sugar solutions to saturation, then cooling to super saturation with stirring.  Stirring allows the sugar molecules to interact to form a crystalline lattice.  If they are stirred hot they tend to form larger crystals, whereas many small crystals will be formed if stirred at a lower temperature.
    • ex. fondant, fudge.
  22. Amorphous candies
     In making these the goal is to inhibit crystallization.  this can be prevented in two ways.  interrferring agents.  quick cooling.
  23. Interfering agents 
    When dealing with sucrose based confections, presense of compounds other than water and sugar will generally interfere with sucrose crystilazation.  sugars other than sucrose, as well as fat, proteins, etc. are all interferring agents.  
  24. Amorphus candie formation 
    super saturated --> super cooled

    ex.  peanut brittle, caramel
  25. cold water test - syrup
    no ball
  26. cold water test - soft ball
    a definite ball but soft
  27. cold water test - firm ball 
    a ball that is firm to the touch
  28. cold water test - hard ball
    a ball that is plastic when handled. 
  29. cold water test - soft crack
    threads present but not brittle
  30. cold water test - hard crack
    Threads which are brittle
  31. final heating temp crystalline 
  32. Final heating temp Amorphus
  33. lower H2O cools very hard
  34. Normality
    concentration expression inducating the number of equivalents per liter
  35. one equivalent
    of an acid is the quanity of acid required to furnish one mole of H+.
  36. ice cream
    contains specified level of milkfat and nonfat milk solids
  37. Frozen custard
  38. mellorine
    milkfat replaced by vegetable or other animal fat
  39. sherbet
    a low fat version of ice cream characterized by addition of a fruit, cocoa, or confectionary flavoring 
  40. small crystals
    As ice crystals are scraped off, air is also being incorprated into the mix. 
  41. Overrun
    The amount of air introduced into the mix