Nutritional Characteristics of Potatoes - The Potato: Botany, Production and Uses - page 328

Given the studies mentioned earlier in this chap-
ter that suggest potato consumption contributes
to obesity and can increase the risk of diabetes,
it is especially notable that chlorogenic acid
may decrease the risk of type 2 diabetes (Legrand
and Scheen, 2007) and can slow the release
of glucose into the bloodstream (Bassoli et al .,
2008). If so, then high-CGA potatoes might
have lower glycemic index values. CGA also ex-
hibited anti-obesity effects in mice, where it re-
duced body weight, improved lipid profiles and
decreased obesity-related hormones, possibly
via activation of an adenosine monophosphate
(AMP)-dependent kinase (Cho et al ., 2010; Ong
et al ., 2013), but another study failed to repli-
cate these results (Mubarak et al ., 2013). Other
polyphenols, including some found in potatoes,
may also have anti-obesity properties (Williams
et al ., 2013).

lines that have 15-19 mg g - 1 DW of anthocya-
nins (Navarre, unpublished data).
Tuber anthocyanin synthesis has been
studied more in the periderm, where it is con-
trolled by at least three loci, D , P , and R . P and R
are structural genes, whereas D encodes an
R2R3 MYB (Jung et al ., 2005, 2009; Zhang
et al ., 2009). The D locus mapped to a chromo-
some 10 region that harbored StAN1 (Jung
et al ., 2009). StAN1 expression correlated with
anthocyanins in drought-stressed potatoes
(André et al ., 2009). A novel approach to dissect
tuber anthocyanin regulation used purple pota-
toes that had incomplete pigmentation, with the
flesh containing both white and purple sectors.
Microarray analysis of the white versus purple
tissue from the same tuber, along with tubers
from white or purple genotypes, was able to re-
duce 1817 differentially expressed genes down
to 27 genes differentially expressed in purple tis-
sue in all sets (Stushnoff et al ., 2010).
Potatoes contain small amounts of flavonols
including rutin and kaempferol, but are not re-
garded as important sources of dietary flavonols.
It is unclear to what extent levels can be increased
in potatoes by directed efforts. Various studies
suggest quercetin and related flavonols have
health-promoting effects, including reduced risk
of heart disease, lowered risk of asthma, bron-
chitis, and emphysema, and reduced risk of pros-
tate and lung cancer. A survey of Andean pota-
toes found a range from zero to 191 and 222 µg
g - 1 DW for rutin and kaemp- 3- rut, respectively
(Andre et al ., 2007b), while Phureja group tubers
contained up to 3000 µg g - 1 DW (Pillai et al .,
2013). Advanced breeding lines containing over
430 µg g - 1 DW are reported (Navarre et al ., 2011).
Flavonols increased in fresh-cut tubers up to
140 µg g - 1 FW, suggesting that the use of specific
processing methods may be a way to increase
tuber flavonols (Tudela et al ., 2002a).

Anthocyanins and flavonols

Red- and purple-flesh cultivars can contain
substantial amounts of anthocyanins, com-
pounds that are antioxidants and have other
health-promoting effects. A potato anthocya-
nin extract had anticancer properties (Reddi-
vari et al ., 2007b). Anthocyanins from purple
potatoes were found to be more stable at low
pH and temperatures, and protected against
chromium toxicity, as measured by protecting
bovine serum albumin conformation (Zhao
et al ., 2011). Lewis et al . screened 26 colored-
fleshed cultivars for anthocyanin content and
found up to 7 mg g - 1 FW in the skin and 2 mg
g - 1 FW in the flesh (Lewis et al ., 1998). Another
study evaluated 31 colored genotypes and
found a range of 0.5- 3 mg g - 1 FW in the skin
and up to 1 mg g - 1 FW in the flesh (Jansen and
Flamme, 2006). Brown evaluated several
genotypes for anthocyanins and found whole
tubers that contained up to 4 mg g - 1 FW and
that anthocyanin concentration correlated
with antioxidant value (Brown et al ., 2005).
The Andean cultivar, Guincho Negra, from the
Andigenum group, contained 16 mg g - 1 DW of
anthocyanins (Andre et al ., 2007b), whereas
RN27.01 of the Phureja group contained
41 mg g - 1 DW (Pillai et al ., 2013). We have
found baby potatoes from advanced breeding

Tuber discoloration

A potential complication of high-phenolic white
potatoes could be the potential for unaccept-
able levels of browning or after-cooking darken-
ing (ACD), as documented by older literature.
However, recent studies showed that amounts of
total phenolics or chlorogenic acid did not