Amino acids, proteins
and Maillard browning
FN 453
Food Chemistry
Exp 1-Maillard reaction
¾ Start early as this takes a while
¾ Chemistry
Browning chemistry
Exp 2-Qualitative tests for proteins
¾ Biuret
Complex is a blue-violet
color
Exp 2-Qualitative tests for proteins
¾ Xanthoproteic test
Nitrated amino acids are intensely yellow to burnt orange
Exp 2-Qualitative tests for proteins
¾ Reduced sulfur test
S-containing AA + KOH + Pb(OAc)2
PbS
A black precipitate
Exp 2-Qualitative tests for proteins
¾ Ninhydrin test
Lavender color indicates AA, except for proline and
hydroxyproline which give yellow products
Exp 3-Quantitative protein test with
Biuret
¾ Requires construction of a standard curve
¾ The unknown may need to be diluted so
that it’s reading falls in the limit of the
standard curve
¾ Read at 550 nm on Spec 20 Spectrometer
Standard curve example
Unknown
Absorbance=
0.68
Unknown
Concentration
= 4.3 g/dl
Exp 4-Effect of heat on proteins
¾ Temps
z
z
z
40 deg C-incubator under ovens
60 deg C-drying oven
68 deg C=water bath
Exp 5-Coagulation of proteins
¾ Examines effect of other additives on the
coagulation of proteins
¾ Additives
z
Various concentrations of salts, sucrose and
acid
¾ Heat for 20 minutes in water bath while
heating and note temperature of
coagulation
Exp 6-Effect of pH on hydration of
meat proteins
¾ Use large centrifuge tubes for this
experiment
¾ Make sure and weigh and label the tubes
before putting any meat in them!!
¾ Adjust meat to various pH’s and see how
much water is held by a given amount of
meat
¾ Try and get exactly 3 grams of meat in
each tube—this is important!
Exp 6-Effect of pH on hydration of
meat proteins
Minimum WHC occurs
Near IEP
Exps 7 and 8
¾ We are not doing these this semester