226 Leenawaty Limantara et al. / Procedia Chemistry 14 ( 2015 ) 225 – 231
Nomenclature
SPAD Soil Plant Analysis Development
HPLC High Performance Liquid Chromatography
R
2
coefficient of determination or goodness-of-fit of linear regression
sp. species
subsp. subspecies
var. variety
s sec
1. Introduction
Nowadays, consumption of green leafy vegetables has been
increasing, especially as a counterbalance of the
growing number of degenerative diseases. Several bioactive compounds in vegetables are including vitamins,
minerals, antioxidants, as well as the pigments (chlorophylls and carotenoids). In the living plants, chlorophylls play
an i
mportant role as primary photosynthetic pigment to capture light energy from the sun. Composed together with
carotenoids (the accessory photosynthetic pigments) in pigment-protein complexes, it exhibits colour appearance
w
hich is specific for each plant leaf and even used as parameter of maturity, quality, and freshness of food crops
.
The colour is extremely important because it defines the ap
pearance of the vegetables and influences consumer
choice
3
. However, this minimally processed vegetables are most kept under low temperature preservation (usually
4 °C to 10 °C, with 95 % to 100 % relative humidity) and sold within one week. During that period, the
p
hysiological processes occur and particularly cause loss of colour due to degrad
ation of leaf pigments or tissue
browning. Hence the quality and freshness of commercially sold vegetable can be monitored by measuring its
ch
lorophyll contents
4
.
The content of chlorophylls can be determined photometr
ically following extraction of the pigments using an
organic solvent, such as acetone or dimethyl formamide, or else by means of handheld device based on lightemitting
diodes and silicon
photodiode
rece
ptor
that
measures
leaf
transmittance
in
the
red
(650
nm)
and infrared
(950
nm)
regions
of
the
electromagnetic
spectrum
5
. The transmittance values are used by the device to derive a
relative SPAD meter values that is proportional to the amount of chlorophyll in the sample. The former method is
considered as in vitro measurement which is well established and accurate, but time-consuming, destructive, and
req
uires the use of toxic or flammable chemicals. On the other hand, the latter provides an alternative in vivo
method for the measurements of relative leaf chlorophyll levels that overcome these disadvantages, but it is less
accurate
, not applicable for small or thick leaf, influenced by light condition, and produces only predictive value.
There have been numerous studies which evaluated the correlation between in vitro chlorophyll data with its in
vi
vo data, based on SPAD value as well percentage of nitrogen in lea
f, by using available handheld instruments. The
correlation between SPAD value and % N was mostly found as strong linear function, while the strong relationship
(R
2
~ 0.9) between SPAD value and in vitro chlorophyll concentration has been previously proposed to follow
exponential
6
or second-order polynomial function
5,7
. Most of the studies employed the leaves of growing plant at
certain medium or light set up, but there are only a few numbers of investigations which employed post-harvested
sa
mples. Here, the correlation between in vivo and in vitro data of the chlorophyll content of ten green leafy
v
egetables purchased from three different supermarkets at Malang, East Java, Indonesia, was observed. The
objectives of this study were to (i) identify the range of the SPAD value and % N for ten selected green leafy
v
egetables on their condition in the market; and (ii) find out the distribution of the feasibility of in vivo
measurement among ten selected leafy vegetables, compared to their in vitro data.
1,2