Agriculture Reference
In-Depth Information
NH
2
(a)
(d)
OH
N
+
O
N
O
S
HO
NH
N
OH
OH
O
(b)
(e)
N
NH
R1
OH
R
R2
O
O
N
N
O
HO
P
OH
R3
NH
2
HO
O
HO
N
OH
HO
OH
O
O
(c)
(f)
OH
HN
NH
O
N
S
OH
Fig. 18.3.
Structures of B vitamins. (a) B
1
, thiamine; (b) B
2
, riboflavin; (c) B
3
, niacin; (d) B
5
, pantothenate;
(e) B
6
, pyridoxine; (f) B
8
, biotin.
were unstable across environments. The moderate
broad-sense heritability suggests that breeding
for thiamine enhancement should be possible,
but the identification of clones that perform well
across environments is difficult because of the
presence of genotype × environment interactions
and the instability of many clones.
in boiled (peeled or unpeeled) potatoes (Augustin
et al
., 1978). Temperature and time of cooking
used in these studies may account for these dif-
ferences.
Vitamin B
2
(riboflavin)
Postharvest and cooking
Riboflavin is the precursor for flavin mononucle-
otide (FMN) and flavin adenine dinucleotide
(FAD)
(Fig. 18.3b)
. They are cofactors in various
oxidative enzymes, also called flavoproteins,
which participate in diverse biochemical reac-
tions such as fatty acid oxidation, biosynthesis
of other vitamins (B
6
, B
9
, B
12
), or the mitochon-
drial electron transport chain (Roje, 2007). In
plants, riboflavin is also specifically relevant
for tetrapyrrole biosynthesis, with major end
products being chlorophyll and heme (Hedtke
et al
., 2012). RDA values for women and men in
the USA are 1.1 and 1.3 mg day
-
1
,
respectively
(
Table 18.1
)
(Otten
et al
., 2006). Symptoms of
riboflavin deficiency, also called “ariboflavinosis”,
include inflammation and cracks of the mouth
and tongue, sore throat, and stunted growth.
Storage at cold temperature does not lead to
significant thiamine loss; instead, thiamine con-
centrations slightly increase in several geno-
types when stored for a period of
3-
8 months.
There is disparity in the literature regarding
the effects of cooking and cooking methods on
thiamine in potatoes. The USDA Nutrient Data-
base reports that oven-baked white, russet, and
red potatoes contain less thiamine (20% de-
crease) but more folate (75% increase) than raw
potatoes, while boiled potatoes contain more
thiamine (32% increase) but less folate (37% de-
crease). Thiamine losses (14%) in oven-baked po-
tatoes have also been reported (Augustin
et al
.,
1978). Unlike the USDA Nutrient Database,
Augustin
et al
. reported a 12% loss of thiamine
