Hii, Law - Quality Evolution During Drying of FVFs
Where RT
E
0
a
k kexp
−
= (6. 15)
The constant k is known as the degradation rate constant which follows the Arrhe-
nius temperature dependency equation (Equation 6.15). The term E is the activation
energy while R is the universal gas constant (8.314 J/mol-K).
6.2.3.2. Antioxidants
Most fruits and vegetables contain various antioxidants which are beneficial to hu-
man health such as in lowering incidence of degenerative diseases i.e. cancer, arthritis,
arteriosclerosis, heart diseases, inflammation, brain dysfunction and ageing process
(Lim et al., 2007 ). This is due to the ability of the antioxidants to scavenge free radicals
in human body and thereby decrease the amount of free radical damage to biological
molecules like lipids and DNA (Wu et al., 2004). Antioxidants from plant chemical are
such as Vitamin C, Vitamin E, carotenoids, polyphenols, melanoidins and indoles
(Manarch, et al., 2004). Drying causes nutritional losses and hence some antioxidants
are destroyed, probably due to thermal degradation, depending on the drying condition
and techniques used. Table 6. 6 and Table 6.7 list some of the common methods that
are used to determine the antioxidant capacity and the antioxidant photochemical in
food products.
Table 6.6. Determination of antioxidant capacity
Method Analytical assay Unit Sample Reference
ABTS cation
radical-
scavenging assay (^) 2,2’-azinobis-(3-
ethylbenzothiazoline-6-
sulfonic acid)
μmol/g AEAC Fruit seeds^ Soong and Barlow
(2004)
Trolox equiva-
lent antioxidant
capacity (TEAC)
assay
mmol/L Fruits and
vegetables
Pellegrini et al.
(2007)
Oxygen radical
absorbance ca-
pacity (ORAC)
2,20-azo-bis, 2-
amidinopropane (AAPH)
dihydrochloride solution
μmol TE/g Fruits^
Date
Patthamakanokporn
et al. (2008)
Maisuthisakul et al.
(2007)
DPPH free radi-
cal-scavenging
assay
1,1-diphenyl-2-
picrylhydrazyl assay
IC 50 , AEAC Fruits Lim et al. (2007)
DPPH radical sca-
venging activity
(%), EC 50 , AAR
Plant ex-
tracts
Maisuthisakul et al.
(2007)
μmol BHT equiva-
lents/ g sample
FW
Strawberries Pinto et al. (2008)
Ferric-reducing
antioxidant pow-
er assay (FRAP)
Ferric-TPTZ (2,4,6-
tripyridyl-s-triazine) rea-
gent
μmol/g FRAP Fruit seeds Soong and Barlow
(2004)
μmol TE/g Fruits^ Patthamakanokporn
et al. (2008)
μmol /g DW Apple peel^ Łata (2008)^