食品化学课件 Topic 2-3 FScN-4112-12 aw chemistry.pdf
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FScN 4112- 2012
Topic 1-3
Food chemical reactions as a f (a )
w
Slide # 1
Reaction Parameters
} Enough solvent to dissolve reactant A
} Reactant mobility A+X-B
Local solvent phase viscosity
Nature of polymer matrix inhibiting mobility
} Solvent effects e.g. dielectric, pH
Slide # 2
General Reaction Kinetics
A + X è AX * è B + X
dA n
Rate = = ± k [A]
obs
dt
kobs = observed rate constant
A = moles reactant / volume solvent
n = order (via curve fitting)
Slide # 3
A k = slope = I rate constant I
o
eg mg/day = (A -A )/(t -t )
2 1 2 1
A
} zero order 1
A
2
t1 t2
time
+dB -dA
dt = dt = ± kobs= constant
Note k is always absolute value
A = A - k t or B = B + k t
o o
Linear equation
Slide # 4
} first order exponential loss or gain
Ao 100
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