Content uploaded by Shamsudeen Sanusi Nassarawa
Author content
All content in this area was uploaded by Shamsudeen Sanusi Nassarawa on Nov 04, 2020
Content may be subject to copyright.
REVIEW ARTICLE
Effect of Light-Emitting Diodes (LEDs) on the Quality of Fruits
and Vegetables During Postharvest Period: a Review
Sanusi Shamsudeen Nassarawa
1,2
&Asem Mahmoud Abdelshafy
1
&Yanqun Xu
1,3
&Li Li
1
&Zisheng Luo
1,3,4,5
Received: 24 June 2020 / Accepted: 17 September 2020
#Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
Major losses of fresh horticultural produce transpire during postharvest storage due to prompt senescence and diseases. The
traditional postharvest preservation techniques used after harvest are based on cooling and the application of chemical preser-
vation techniques. As a residue-free physical sterilization and preservation method, light-emitting diode (LED) treatment, has
recently been applied for postharvest storage of fruits and vegetables by numerous researchers. This paper reviews the recent
applications of LEDs in postharvest storage of fresh produce, including its effect on physiological characteristics, secondary
metabolism, nutritional attributes, ripening process, senescence, shelf-life improvement, and pathogenic microbial spoilage of
fruits and vegetables. LED treatment has promoted the accumulation of different phytochemicals, such as phenolic compounds,
vitamins, glucosinolates, chlorophyll, total soluble solids, and carotenoids. Changes in the nutritional content, anthocyanin
content, antioxidant capacity, and ripening were also observed after the treatment. Reduction in microbial spoilage and delay
senescence were evident after the LED exposure. The influence of LED light depended on the fruit and vegetable variety.
Therefore, LED treatment is an efficient and promising strategy for extending the storage life of fruits and vegetables with
enhanced nutritional values.
Keywords LEDs .Fruits and vegetables .Postharvest .Preservation .Light quality
Introduction
Fruits and vegetables are well known for their health-
promoting properties due to their contents of vitamins, min-
erals, and antioxidants, which reduce the risk of chronic
diseases and increasing their demand in the consumer diet
(Aghdam et al. 2018; Pinela and Ferreira 2017; Slavin and
Lloyd Beate 2012). The Food and Agriculture Organization
(FAO) has reported that fruits and vegetables are the most
wasted commodities (Dou et al. 2017;Migueletal.2008).
The primary causes for this wastage are inefficient postharvest
infrastructure and poor harvesting and storage techniques (
Dou et al. 2017; Dueck et al. 2016; Kozai 2013; Kozai and
Niu 2015; Regnier and Combrinck 2009). The postharvest
problem is a major global issue, in both developed and devel-
oping countries. Many studies have shown that there are min-
imal storage facilities for various horticultural crops, especial-
ly in developing countries, which has influenced postharvest
losses, including over-ripening, softening, decay, weight loss,
senescence, firmness loss, and specific physiological disor-
ders (Bantis et al. 2018; Dou et al. 2017). The shortening of
fruits and vegetable loss is a leading issue for providing long-
term storage across the global population (Capone et al. 2014).
However, due to the speedy senescence and susceptible dis-
eases of postharvest fruits and vegetables, the preservation
technology has become the research focus (Mari et al. 2016;
Usall et al. 2016).
*Zisheng Luo
luozisheng@zju.edu.cn
1
College of Biosystems Engineering and Food Science, Zhejiang
University, Hangzhou 310058, People’s Republic of China
2
Department of Food Science and Technology, Faculty of
Agriculture, Bayero University, Kano, Kano State, Nigeria
3
Ningbo Research Institute, Zhejiang University, Ningbo 315100,
People’s Republic of China
4
National-Local Joint Engineering Laboratory of Intelligent Food
Technology and Equipment, Key Laboratory of Agro-Products
Postharvest Handling of Ministry of Agriculture and Rural Affairs,
Zhejiang Key Laboratory for Agri-Food Processing,
Hangzhou 310058, People’s Republic of China
5
Fuli Institute of Food Science, Hangzhou 310058, People’sRepublic
of China
Food and Bioprocess Technology
https://doi.org/10.1007/s11947-020-02534-6
Currently, the techniques used for preserving fruits and
vegetables are mainly chemical additives, such as the use of
1-methyl cyclopropane (Amornputti et al. 2014; Chiabrando
and Giacalone 2011), ozone treatment (Song et al. 2016),
application of a high oxygen atmosphere (Zheng et al.
2008), chitosan coating (Kerch 2015), and physical tech-
niques, including controlled atmosphere storage
(Skrovankova et al. 2015), forced air cooling air packaging
(Castro et al. 2004), and UV-C (Amornputti et al. 2014;Wang
et al. 2009), and biological techniques such as biocontrol
agent (Amornputti et al. 2014) to reduce losses. As a result
of limitations on chemical additives technologies, thus, the
food processing industries have shifted toward nonthermal
approaches, including irradiation, ultraviolet light (UV),
pulsed light (PL), high-pressure processing (HPP), ultrasound
(US), and cold plasma (Naveenkumar et al. 2017; Castillo
et al. 2010; Osae et al. 2020; Pinela and Ferreira 2017).
Recently, greater emphasis has been paid to the influence
of LEDs (narrow-bandwidth illumination) on the postharvest
storage of fresh horticultural produce. Recent research has
shown that LEDs enhance the traits of numerous postharvest
fresh produce, including lettuce, cabbage, kale plants, white
mustard, sweet pepper, cucumber and blueberries (Hung et al.
2016), peaches (Gong et al. 2015), strawberries (Xu et al.
2014a,2014b), tomatoes (Dhakal and Baek 2014), citrus fruits
(Ma et al. 2012), Chinese bayberries (Shi et al. 2014), Spinach
and kale (Erwin and Gesick 2017), and grapes (Rodyoung
et al. 2016).
In addition, there have been many researches on the applica-
tion of LEDs in the field of postharvest fruits and vegetables and
several reviews on plant physiology (D’Souza et al. 2015).
However, there is a lack of usable information on the advantages
of LED techniques when applied at the time of postharvest stor-
age. There is also no synopsis of the influence of LEDs on
quality attributes. This review provides information on the appli-
cation of LEDs for the postharvest preservation of fresh horticul-
tural crops. An overview of the effect of LEDs as a nonhazardous
technique for improving the ripening process, nutritional param-
eters, and secondary metabolites, delaying senescence, and lead-
ing to quality improvement of fruit is discussed.
Overview of LED (NBI) Technology
in the Postharvest Period of Fruits
and Vegetables
LEDs are a solid-state (i.e., semiconductor-based) system that
converts electrical energy to electromagnetic radiation
(D’Souza et al. 2015; Schultz et al. 2008), typically in the
infrared or visible regimes (Rodyoung et al. 2016), and occa-
sionally in ultraviolet regimes (Bantis et al. 2018; Dou et al.
2017; Krames et al. 2007). A depiction of a LED system is
shown in (Fig. 1). The LEDs comprised of a semiconductor
with a p-n (positive-negative) junction, consisting of p-type
(positive-doped) and n-type (negative-doped) semiconductor
on the right and left, respectively. A depletion region, defined
as the barrier between p-type and n-type regions that prevent
the movement of electrons from n-type and holes from p-type
semiconductors, is created due to diffusion currents. The de-
pletion region left with positive and negative charged ions.
Electrons and holes (beingthe absence of particles) recombine
spontaneously when a forward bias (i.e., applied electric field)
forces them to interact within the depletion region. This re-
combination process produces light (as photons) in a sponta-
neous emission process, defining the mechanism of the LEDs
(Bantis et al. 2018; Folta et al. 2005; Hasan et al. 2017a,
2017b). This emitted light has a wavelength dictated by the
bandgap energy of the semiconductor between the conduction
and valence energy bands (D’Souza et al. 2015). The emission
of light from LED can vary from a narrow band of single
colors like red, green, or blue to the wider band for white light
(Mitchell et al. 2012). A white LED is typically a blue LED
that has been infused with phosphorous to broaden the emis-
sion spectrum. A phenomenon involved in the operation of
LEDs is electroluminescence, which is a non-thermal process
of emitting light when the electric current passes through the
semiconductor(Laietal.2016). The electroluminescence
phenomenon was first detected when H. J. Round was work-
ing with silicon carbide in 1907. However, the first patent
based on the emission of infrared radiation from a semicon-
ductor due to the passage of electricity was obtained by James
Biard and Gary Pittman in 1962 (Taulavuori et al. 2017).
Fig. 1 LEDs showing the
emission of photons
Food Bioprocess Technol
LEDs have many advantageous properties that mark their
use in postharvest storage of fruits and vegetables (Bantis et al.
2018; Branas et al. 2013; Lee et al. 2014a,2014b ). LEDs have
the potential to regulate senescence, lead to ripening, and im-
prove fruit quality and nutritional attributes in fruits and veg-
etables (Dutta Gupta 2017;Bantisetal.2018). The potential
of LEDs to extend the storage life of horticultural crops is
advancing. Other advantageous properties of LEDs include
their monochromatic nature, long life, prevention of thermal
degradation, and high photon efficiency. All these favorable
characteristics make LED application beneficial for extended
the storage life of fruits and vegetables (Krames et al. 2007;
Yu et al. 2017). LEDs do not involve the use of heavy metals
that are toxic and operate at a low temperature and low direct
current (DC) voltages (Dutta Gupta et al. 2019;D’Souza et al.
2015; Yang et al. 2018). Furthermore, the monochromatic
nature of LEDs allows for the selection of the wavelength-
specific emission light spectra desired for the production,
preservation, and storage of fresh horticultural produce
(Krames et al. 2007;Yuetal.2017). The application of
LEDs in postharvest has expanded due to its numerous advan-
tages over conventional light sources. LEDs have more effi-
cient energyutilization and a longer lifespan (approximately 5
×10
4
versus 7–15 × 10
3
h) compared with traditional light
sources (Krames et al. 2007;Yuetal.2017). Additionally,
LED lights have some properties such as the capability to
restrain spectral composition, adjustable sizes, durability, a
longer operating time, and relatively cold emitting surfaces
(Folta et al. 2005;Yuetal.2020). LEDs facilitate nonthermal
operations and therefore minimize thermal degradation that
might have any detrimental influence on the quality of fresh
produce. It is also mechanically robust, which prevents dam-
age due to vibrations. LEDs do not present any mechanical
damage as a result of transportation, thus enabling their use in
cold storage (D’Souza et al. 2015).
Characteristics of LEDs (NBI)
LEDs emit low radiant heat and are highly effective at a
low temperature. LEDs have long-term effects and can last
for 50,000–100,000 h working against traditional lighting,
which can last for 15000 h (Jatothu 2013;Zhmakin2011).
LEDs have a close-packed size that improves flexibility
while designing lighting systems. LEDs can control ultra-
violet (UV) and infrared (IR) LEDs, while both UV and IR
LEDs cannot control high-pressure lamps (HPL) and fluo-
rescent lights (Denbaars et al. 2013; Munthikote 2018).
LED components can be assembled into a compact system
of various shapes, but this cannot be achieved with HPL
and fluorescent lights due to their bulkiness (Ibrahim et al.
2014; Munthikote 2018). LEDs have a color mixture of
white of 100–150 lm/W, whereas high-pressure and
fluorescent lamps have values of 45–80 lm/W, and 65–
150 lm/W, respectively. Many properties of LEDs have
facilitated their use over traditional light, such as sodium
and xenon lamps (D’Souza et al. 2015), high-intensity dis-
charge lamps (Dutta Gupta 2017). LEDs are energy effi-
cient with high luminosity and high photon flux (Dutta
Gupta 2017). They do not involve the use of heavy metals
that are toxic in cases of leakage (D’Souza et al. 2015).
Additionally, LEDs are safe to operate and have adjustable
on/off properties.
Effects of LEDs (NBI) on Postharvest
Physiochemical Characteristics of Fruits
and Vegetables
During postharvest storage, the majority of fruits and vegeta-
bles undergo rapid age and deterioration in quality, such as a
rise in respiration process, softening, tissue destruction, and
lipid peroxidation, increases in water loss, and postharvest
quality characteristics such as the visual scale, flavor, texture,
aroma, and nutritional quality; therefore, the primary purpose
of postharvest storage of horticultural crops is to postpone
senescence and to maintain the trait of fruits and vegetables
during storage (Hodges and Toivonen 2008; Martínez-
Romero et al. 2007; Pinela and Ferreira 2017; Prasad and
Chakravorty 2018; Sharma et al. 2017). LEDs have been
proven to be an effective inhibitory treatment for postharvest
senescence of fresh produce in recent years, by extending the
shelf life and maintain the quality of fresh produce (Table 1)
(Colquhoun et al. 2013;D’Souza et al. 2015; Dhakal and
Baek 2014; Dutta Gupta 2017; Gong et al. 2015; Hodges
and Toivonen 2008; Kader 2005; Lichtfouse 2015; Prasad
and Chakravorty 2018; Xu et al. 2014a,2014b). The most
recent study mainly focused on the application of LEDs in
horticulture, and some studies have explored the application
of LEDs in the postharvest stage (Dutta Gupta 2017). The
study of the effect of LEDs on postharvest quality is relatively
recent but has resulted in important findings.
Color Development
The color of a fruit is an important attribute that defines fruit
acceptability and quality. In most fruit such as blueberries, the
presence of anthocyanins is responsible for their color. The
color of the fruit is affected by multiple factors, such as tem-
perature, pH, and fruit physiology (Casati et al. 2012).
Similarly, light has a significant impact on the color indices
of fruits and vegetables, which regulate their shelf life. The
development of color in fruits after harvest is related to the
accumulation of various pigments such as lycopene, chloro-
phyll, or anthocyanin (Büchert et al. 2011;Xuetal.2014a,
Food Bioprocess Technol
Table 1 Effect of LED treatment on the physicochemical characteristics of fruits and vegetables during postharvest storage
Treated fruit/vegetable LED types Treatments Results Reference
Broccoli
(Brassica oleracea)
White (463 nm) LEDs 12 days of treatment at
a fluence rate of 12,
25, and 50 W m
−2
at 22 °C
White LED treatment increased the L
value after 12 days at 22 °C
(Büchert et al. 2011)
Strawberries
(Fragaria ananassa)
Blue LEDs 12 days of treatment at
5 °C at a fluence rate
of 40 W m
−2
After 4 days of blue LED treatment,
the color development in
strawberries increased. However,
the respiration rate decreased
during the initial 2 days of storage,
followed by a gradual increase in
the control and blue light treatment
at 5 °C. Blue LED treatment
increased the values of CRIG as
compared with control samples.
(Xu et al. 2014a,2014b)
Brussels sprouts (Brassica
oleracea gemmifera)
White and blue LEDs 5 and 10 days
treatment at a
fluence rate of 20 W
m
−2
at 22 °C
Medium intensity LED treatment
increased weight loss of Brussels
after 10 days at 22 °C compared
with control untreated samples
kept in the dark.
(Hasperué et al.
2016a,2016b)
Broccoli (B. oleracea var.
Italica,cv. You-xiu)
Red (630 nm) LEDs 5 days of treatment at a
fluence rate of 50 W
m
−2
at 20 °C
A higher increase in weight loss was
observed in broccoli during
storageinbothgroups.Thelevel
of increase in weight loss was
significantly lower in the control
group relative to treated broccoli
on4and5days.
(Jin et al. 2015)
Broccoli (B. oleracea var.
Italica,cv. You-xiu)
Red (630 nm) LEDs 5 days of treatment at a
fluence rate of 50 W
m
−2
at 20 °C
The red light was able to inhibit the
increase in L values, leading to the
higher chlorophyll content of
59.1% compared with the control
untreated samples. Likewise, the
a/b value of broccoli generally de-
creased during storage, regardless
of treatment; however, it was
higher in LED-treated broccoli af-
ter 3 days until the end of the ex-
periment.
(Jin et al. 2015)
Peaches (Prunus persica cv.) Blue (470 nm) LEDs 15 days of treatment at
a fluence rate of
40 W m
−2
at 10 °C
Blue LED treatment significantly
increased ethylene production, and
the maximum ethylene production
was delayed from 6 to 9 days, TSS
content increased, and acidity
decreased in peaches after 15 days
of storage at 10 °C.
(Gong et al. 2015)
Citrus fruits (Citrus sp.) Red (660 nm) and blue
(470 nm) LEDs
6 days of treatment at a
fluence rate of 50 W
m
−2
at 20 °C
After 6 days of red and blue LED
treatment, the contents of
antioxidants, phenolics, total
soluble sugars, and ascorbic acid
and enzymatic activities increased
significantly at 20 °C.
(Xu et al. 2014a,2014b)
Tomato (Solanum
Lycopersicum)
White and
red:far-red LEDs
6 days of treatment at a
fluence rate of
476 W m
−2
at 23 °C
Highest red: far-red ratios treatment
positively affected the firmness
parameters compared with other
white LED light conditions.
Furthermore, red: far-red ratio in-
creased the TSS and TA of the to-
mato fruit compared with the
white LED light and control sam-
ple after 6 days of storage
at 23 °C.
(Nájera et al. 2018)
Food Bioprocess Technol
Table 1 (continued)
Treated fruit/vegetable LED types Treatments Results Reference
immature green tomatoes Blue light (440) and red
light (450 nm)
21 days of treatment at
a fluence rate of
102.70 and 85.72 W
m
−2
at 25 °C
Both red LED, and dark (control)
treatment increased the color of
tomatoes, while those treated with
blue light wereyellowish color at 7
days. But no difference was ob-
served after 21 days of storage.
There was a gradual decrease in
the firmness of tomatoes as the
storage time increased. Tomatoes
treated with blue light maintained
significantly higher levels of firm-
ness than those treated with red
and darkness after 21 days of
storage. Tomatoes treated under
red light and darkness accumulat-
ed significantly higher amounts of
lycopene than those treated under
blue light after 7 days of storage.
Tomatoes treated under blue light
showed gradually increasing lyco-
pene contents as the storage time
in darkness increased, eventually
reaching the same levels of lyco-
pene as those treated under dark-
ness and red light after 21 days of
storage. The TSS content of to-
matoes treated under darkness, red
light, and blue light did not differ
significantly after 7 days of storage
and remained constant after 14
days of storage. Nevertheless, all
treatment showed a significant de-
crease in TSS after 21 days
of storage.
(Dhakal and Baek 2014)
Habanero pepper
(Capsicum chinense)
Blue and
UV-C LED light
30 days of treatment at
4–5 °C at a fluence
rate and dosage of 0,
1.5 W m
−2
and 0,
0.5 kJ m
−2
Blue and UV-C LED light both in-
creased the content of all bioactive
compounds and antioxidant ca-
pacity in habanero pepper vegeta-
bles for 30 days at 4–5°Cduring
storage. However, in some bioac-
tive compounds such as chloro-
phylls and total carotenoids, the
effect was evident only in the 1
days of storage.
(Pérez-Ambrocio et al. 2018)
Lettuce (Lactuca sativa
L. cv. ‘Zishan’)
Red and blue LED (456
nm) and (655 nm)
20 days of treatment at
a fluence rate of
500 W m
−2
and 23
°C
Red and blue LED treatment
increased the weight of lettuce first
and then decreased after 10 days of
storage. However, both the LEDs
increased the content of soluble
sugar, anthocyanin, flavonoid,
total phenolic, and ascorbic acid
compared with the untreated
sample (control).
(Shao et al. 2020)
Chinese bayberries
(Myrica rubra)
Blue (470 nm) LEDs 8 days of treatment at a
fluence rate of 40 W
m
−2
at 10 °C
After 8 days of blue LED treatment,
the content of total soluble sugar,
consisting of fructose, sucrose, and
glucose, in the Chinese bayberries
significantly increase as a result of
an increase in gene expression
(hexokinase genes, cryptochrome
genes, glucose sensor genes).
(Shi et al. 2016)
(Kim et al. 2011)
Food Bioprocess Technol
2014b). The accumulation and production of pigments are
affected mainly by light (Xu et al. 2014a,2014b).
In brussels sprouts (Brassica oleracea gemmifera)treated
with white and blue LEDs for 10 days of storage, LEDs affect
the color indices of the vegetables (Hasperué et al. 2016a,
2016b). Similarly, lower L (where L* lightness-darkness col-
or) values also reported in broccoli florets exposed to red
LEDs (630 nm) at a fluence rate of 50 W m
−2
for 5 days.
The red light was able to inhibit the increase in L values,
leading to the higher chlorophyll content of 59.1% compared
with the control untreated samples; likewise, the a/b (where
the positive a* represents the redness and the negative a*
represents the greenness whereas the positive b* represents
the yellowness and the negative b* represents the blueness)
value of broccoli generally decreased during storage, regard-
less of treatment; however, it was higher in LED-treated broc-
coli after 3 days until the end of the experiment (Jin et al.
2015). It has been reported that blue LED treatment
(85.72 W m
−2
) in green tomatoes fruit was able to prevent
red color development as compared with red light
(102.70 W m
−2
) and untreated samples after 7 days of storage.
The L values were significantly lower for tomatoes treated
with blue light with less reddish tomatoes visually.
However, tomato treated with the red light turned red at room
temperature for given intensity (Dhakal and Baek 2014). Also,
when the treatment of strawberries was carried out with blue
light at a fluence rate of 40 W m
−2
for 12 days at 5 °C and
evaluated for color changes, no significant differences were
observed. Also, there was an increase in CRIG values during
postharvest storage as compared with control samples (Xu
et al. 2014a,2014b). In another study conducted by Büchert
et al. (2011), there was an increase in L value for broccoli
when treated with white light using fluorescent tubes at a
fluence rate of 12, 25, and 50 W m
−2
at 22 °C. This increase
Table 1 (continued)
Treated fruit/vegetable LED types Treatments Results Reference
Strawberry
(Fragaria ananassa)
385 nm (violet, 470 nm
(blue), 525 nm
(green) and
630 nm (red)
4 days of treatment
at 5 °C
After 4 days of LED treatment at 5
°C, the content of soluble sugars,
acidity, total phenol, vitamin C,
and anthocyanin in immature
strawberry increased.
Strawberry
(Fragaria ananassa)
Blue (470 nm) LEDs 12 days of treatment at
5 °C at a fluence rate
of 40 W m
−2
Blue LED treatment enhanced the
levels of phenolics, ascorbic acid,
and acidity in strawberry for 12
days at 5 °C compared with the
control samples, and blue LED
treatment significantly decreased
the total sugar content during the
initial 6 days of storage inboth the
control and treated samples;
however, the contents of
antioxidant and DPPH radical
scavenging activity in strawberries
was increased.
(Ma et al. 2012)
Grape berries (Vitis
labruscana Bailey
cv‘Campbell Early’
and ‘Kyoho’)
Blue LED light
(445 nm)
9 days of treatment at a
fluence rate of 80 W
m
−2
at 15–25 °C
After blue LED treatment, firmness
was not influenced by any of the
treatments for 9 days at 25 °C. TSS
contentwasreducedinthedark
compared with the treated sample.
At the same time, the titratable
acidity was significantly enhanced
and gradually decreased with an
increase in temperature under both
light and dark conditions. The
percentage of berry weight loss
was progressively increased with
increasing temperature under both
light and dark conditions.
(Azuma et al. 2019)
Red Chinese sand pears fruit
(Pyrus pyrifoliaNakai)
White LEDs (765 nm)
and UV-B LED
(315 nm)
10 days of treatment at
a fluence rate of 532
and 270 W m
−2
at 32 °C
White and UV-B LED treatment im-
proved red color, firmness, and
TSS of the fruit for 10 days at 32
°C compared with the control un-
treated sample.
(Sun et al. 2014)
Food Bioprocess Technol
explained that with an increase in the treatment period, fruit or
vegetable heads towards the senescence stage. However, broc-
coli heads remained green under treatment with light than
those kept in the dark, implying that treated samples showed
a lower increase in L value as compared with untreated ones
(Büchert et al. 2011).
The influence of light at different wavelengths (463, 520,
and 630 nm) and fluence rates (20, 40, and 60 W m
−2
)attwo
different temperatures of 21 °C and 2 °C on blueberries
showed variable responses (Zhou et al. 2014). At 21 °C, the
lowest L value was observed for 20 and 40 W m
−2
,respec-
tively, under blue light treatment for 15 days. In contrast, at 2
°C, red light resulted in the lowest L value under the same
conditions. However, with an increased influence rate to (60
Wm
−2
), green light had the lowest L value for 15 days at 21 °C
and 2 °C, followed by blue and red light. At higher fluence
rates, blue and red (40 and 60 W m
−2)
light exhibited an
increased L value compared with the control samples at 21
°C, which was inconsistent with the 2 °C (control samples)
with the highest L values. Overall, enhanced L values were
reported for red light treatment for all three fluence rates at 21
°C. However, a decrease in the L value was observed under
blue light treatment followed by green light. At 2 °C, green
light showed a decrease in L value with an increased influence
rate (Zhou et al. 2014).
Total Soluble Solids
The content of total soluble solids in both climacteric and
non-climacteric fruit determines the maturity index of fruits
and vegetables. Increased levels of total soluble solids (TSS)
in fruit indicate an acceleration of the ripening process, while
a decrease in TSS content indicates slow ripening and en-
hanced shelf life of fruit (Gong et al. 2015). Similarly, the
application of LED treatment in brussels sprouts (Brassica
oleracea gemmifera) inhibited the increase in TSS within the
first 5 days of storage; however, after 10 days of storage, the
TSS content significantly decreased (Hasperué et al. 2016a,
2016b; Shi et al. 2014). Likewise, the application of blue,
green, and red LEDs in blueberry fruit inhibited the maxi-
mum increase in TSS content during postharvest storage
(Taulavuori et al. 2017). At 21 °C, red light showed a max-
imum increase in TSS for 5, 10, and 15 days, followed by
blue and green light at a fluence rate of 20 Wm
−2
.
Equivalently, for 40 and 60 W m
−2
,redlightshoweda
maximum increase in TSS for 5 and 10 days. However, over
15 days, blue light had maximum TSS values. At 2 °C, blue
light resulted in enhanced levels of TSS at 20, 40, and 60 W
m
−2
during the 15-day treatment period. However, the TSS
content of blueberries should remain constant as an increase
in TSS results in ripening and reduces the shelf life of fruit.
Green LED light showed lower values for TSS compared
with red and blue light and control samples over 15 days
of treatment at 20, 40, and 60 Wm
−2
at both 21 °C and 2
°C (Taulavuori et al. 2017). Also, after 4 days of LED treat-
ment at 5 °C in strawberry fruit, the contents of vitamin C
and sugar significantly increased during postharvest storage.
However, the significant increase in TSS in strawberries
could be associated with the solubilization of cell wall com-
ponents of crops, such as polyuronides and hemicelluloses,
rather than the conversion of starch to sugars, as there is very
little accumulation of glycogen during fruit development
(Kim et al. 2011). There was an increase in TSS levels in
Chinese bayberries (Myrica rubra Sieb) under the treatment
of blue (470 nm) LEDs at 40 Wm
−2
for 8 days at 10 °C.
There were enhanced levels of glucose, fructose, and sucrose
as compared with untreated samples (Shi et al. 2016). In
addition, the application of white and red:far-red LED treat-
ment at a fluence rate of 476 W m
−2
significantly increased
the firmness parameters compared with other white LED
light conditions. Furthermore, the highest R: FR ratio in-
creased the TSS and TA of the tomato fruit compared with
white LED light and control sample after 6 days of storage at
23 °C (Nájera et al. 2018)
Conversely, the TSS content significantly increased under
blue light treatment. A similar trend of enhanced ethylene
production was observed in postharvest peaches treated with
blue (470 nm) LEDs for 15 days at 10 °C (Gong et al. 2015).
However, maximum ethylene production was delayed from 6
to 9 days of storage compared with the untreated control sam-
ples. The TSS content significantly increased, and the acidity
decreased after treatment, in addition to color development in
peaches; blue LEDs helped to regulate the synthesis of pig-
ments and internal ethylene in fruit, accelerating the ripening
during a postharvest period (Gong et al. 2015).
Weight Loss
Weight loss is an important problem of quality deterioration in
fruits and vegetables during postharvest storage (Zhan et al.
2012a,2012b). The weight loss of vegetables was inhibited
when treated with LED light, including brussels sprouts
(Brassica oleracea gemmifera) and broccoli (Brassica
oleracea) (Hasperué et al. 2016a,2016b), also brussels
sprouts treated with a white and blue light at a fluence rate
of 20 W m
−2
for 5 and 10 days at 22 °C. There was higher
weight loss under light treatment as compared with control
untreated samples. Also, the weight losses increased with an
increase in the treatment period. These clearly explain the
interaction of blue light with stomatal cells. Blue light affects
the opening of stomata leading to higher respiration rates,
which in return affects the overall metabolism of fruits and
vegetables (Hasperué et al. 2016a,2016b). In addition to res-
piration, the other process affected by light is transpiration that
is also associated with stomatal opening regulated by light
(Zhan et al. 2012a,2012b). In another study conducted by
Food Bioprocess Technol
Xu et al. (2014a,2014b) found that levels of respiration rates
were higher in strawberries treated with blue light after 4 days
of storage at 5 °C. Treatment was carried out at a fluence rate
of 40 W m
−2
for 12 days.
Similarly, a higher increase in weight loss was observed in
broccoli during storage in both treated and untreated samples.
The level of increase in weight loss was significantly lower in
the control group relative to treated broccoli on 4 and 5 days
(Jin et al. 2015). Red and blue LED (456 nm) and (655 nm)
treatment at a fluence rate of500 W m
−2
at 23 °C significantly
increased the weight of lettuce first and then decreased after 10
days of storage (Shao et al. 2020).
Antioxidant Compounds
It is well known that plant senescence is mostly as a result of
the production of reactive oxygen species which can provoke
oxidative damage to lipids and protein of plant cells, thus
controlling the production of ROS is a significant way to
retard the senescence of fresh horticultural produce during
postharvest storage (Skrovankova et al. 2015). The removal
of ROS is classified into two categories: antioxidant sub-
stances (AS) and antioxidant enzymes (AE). AS comprising
(carotenoids, polyphenols, vitamin E, and reduced glutathi-
one), while AE mainly comprises (glutathione oxidase, cata-
lase, ascorbate oxidase, superoxide dismutase, and glutathione
oxidase) (Xu et al. 2014a,2014b).
The antioxidant system of fruits and vegetables was signif-
icantly increased by LED treatment (Table 1). On the other
hand, LED treatment increases the content of other antioxi-
dants such as phenolic compounds (i.e., flavonols, anthocya-
nins, and ascorbic acid), carotenoids, and GSH, as shown in
(Table 1). The increased content of antioxidant and DPPH
(1,1-diphenyl-2-picrylhydrazyl) free radical scavenging activ-
ity was observed in immature strawberries treated with blue
light (470 nm) at 40 W m
−2
for 12 days at 5 °C compared with
untreated samples (Xu et al. 2014a,2014b). In addition, red
(660 nm) and blue (470nm) light treatment at a fluence rate of
50 W m
−2
at 20 °C decreased the contents of carotenoid in
citrus fruit compared with the control, demonstrating a gradual
increase towards the end of treatment (Ma et al. 2017).
However, blue (470 nm) LEDs did not have any significant
effect (Ma et al. 2014). Similar results have been reported for
fresh-cut broccoli using green light treatment (Jin et al. 2015)
and strawberries with a blue light at (40 W m
−2
) (Xu et al.
2014a,2014b). Research showed that LED treatment in-
creased the antioxidant activity of blueberries at 40 W m
−2
at 21 °C and 2 °C (Dinardo et al. 2018). Similarly, the appli-
cation of blue (470 nm) and red (660 nm) LED light in citrus
fruits at 20 °C for 6 days at a fluence rateof 50 W m
−2
both the
light significantly increased the antioxidant present in citrus
fruit such as ẞ-cryptoxanthin (Ma et al. 2012). Also, blue and
UV-C LED light treatment at a fluence rate and dosage (0,
1.5 W m
−2
and 0, 0.5 kJ m
−2
) increased the content of all
bioactive compounds and antioxidant capacity in habanero
pepper vegetables for 30 days at 4–5 °C during storage.
Also, in some bioactive compounds such as chlorophylls
and total carotenoids, the effect was appreciable only in the
1 day of storage (Pérez-Ambrocio et al. 2018). Additionally,
LED treatment increased antioxidant characteristics of many
leafy vegetables such as tomato (Solanum Lycopersicum),
Chinese kale (Brassica sp.), Chinese cabbage (Brassica napus
L.), and pea (Pisum sativum L.), during storage as a result of
ROS-scavenging enzymes, DPPH free radicals, β-carotene,
and glucosinolates (Hee-Sun Kook 2013;Johkanetal.2010;
Ki Lee et al. 2016;Wuetal.2007). The increased activity of
this antioxidant helps in curing many diseases such as cancer
and ultimately promotes the functional properties of citrus
fruit (Ma et al. 2012).
Effects of LEDs (NBI) on Secondary Metabolites in
Postharvest Fruits and Vegetables
Lights of different wavelengths regulate key photochemical
processes include photosynthesis and the production/
assimilation of secondary metabolites in horticultural crops
(Xu et al. 2014a,2014b). The increase in gene expressions
such as MdMYB10 and MdUFGT under the effect of light
aids in the accumulation of compounds such as vitamin C,
soluble sugars, anthocyanin, or organic acids. Additionally,
enzymes such as phenylalanine ammonia-lyase are responsi-
ble for the production of secondary metabolites (Hasan et al.
2017a,2017b). The effect of light on various photoreceptors
or the production of secondary metabolites is essential for its
application of crop productivity and quality (Dutta Gupta et al.
2017). Crops respond to a natural light source, the sun, to
carry out the process of photosynthesis. Also, plants react to
other variables such as the light intensity, duration, wave-
length, surrounding temperature, humidity, and carbon diox-
ide, among others, which leads to the initiation of signals that
affect photoreceptors. For example, the phytochrome photo-
receptor is responsible for the absorption of far-red and red
light (Briggs and Olney 2001; Bentsink and Koornneef 2008;
Brazaityte et al. 2006; Casal 2013; Cookson and Granier
2006; Dutta Gupta 2017;Ouzounisetal.2014;Samuoliene
et al. 2013; Reinbothe and Reinbothe 1996;ParkandRunkle
2017), whereas cryptochrome and phototropin are responsible
for the absorption of blue light (Kong and Okajima 2016;
Wang and Folta 2013). The responses affect processes such
as ripening, senescence, nutritional quality, and overall fruits
and vegetable quality (Solovchenko and Merzlyak 2008;
Seigler 2000; Wang and Folta 2013). Also, light exposure
affects the production of secondary metabolites and the accu-
mulation of phytochemicals (Ki Lee et al. 2016). Light sensors
such as phytochrome, cryptochrome, and phototropin per-
ceive light at variable wavelengths and affect the metabolic
Food Bioprocess Technol
pathways (Braidot et al. 2014;Jones2018; Kong and Okajima
2016).
In fresh horticultural produce, secondary metabolites pro-
duced are different from primary metabolites such as carbo-
hydrates and amino acids (Nhut et al. 2011). The role of LEDs
in secondary metabolite induction in crops seems to be asso-
ciated with the phenylalanine ammonia-lyase enzyme. The
upregulation of PAL by blue light and red LEDs increases
the production of secondary metabolites (Bian et al. 2014;
Heo et al. 2012; Hasan et al. 2017a,2017b). The major sec-
ondary metabolite is ginsenoside, which is generated via the
isoprenoid pathway in ginseng. The effects of LEDs on sec-
ondary metabolites has not been well researched. However,
studies have shown that blue LED treatment (450–470 nm)
increases the concentration of flavonoids in Chinese foxglove
(Rehmannia sp.) from 2–74% compared with the sample that
is stored under dark conditions (Manivannan et al. 2015;Nhut
et al. 2011).
Phenolic Compounds
Phenolic compounds are the main nutrient present in fruits and
vegetables, which not only gives fruits and vegetables the
function of promoting human health but also plays a vital role
in plants themselves as secondary metabolites produced in
response to biological and abiotic stresses. The significant
phenolics found in fruits and vegetables are flavonoids
(cyanidin, petunidin, delphinidin), flavonols (myricetin, quer-
cetin, kaempferol, gallic acid), flavanols (catechins, epicate-
chin), and tannins (ellagitannins and phenolic acid) (Dutta
Gupta et al. 2019; Skrovankova et al. 2015). Light stress pro-
motes the biosynthesis of these compounds. As abiotic stress,
LEDs induce the change of phenolic metabolism of posthar-
vest fruits and vegetables (Table 2). For fruits and vegetables,
this stimulatory influence was likely to increase the total phe-
nolic content over a long time. LEDs as a source of light with
high photosynthetically active radiation efficiency induces re-
sponses through photoreceptors (blue light) (Wang et al.
2009), as well as phytochrome (red light) (Zhan et al. 2012a,
2012b), which are involved in the accumulation of com-
pounds such as flavonoids, quercetin glycosides, or
kaempferol. So, blue light plays a significant role in activating
a biosynthetic pathway to produce phenolic compounds in the
fruit. It regulates and stimulates the enzymes such as phenyl-
alanine ammonia-lyase (PAL) associated with the synthesis
and accumulation of secondary metabolites (Wang et al.
2009). Red light helps in enhancing the photosynthetic ability
and induces photophosphorylation for stomatal opening. It
converts the phytochrome from an inactive state to active form
and regulates the accumulation of phytochemicals such as
tocopherols and terpenes (Zhan et al. 2012a,2012b).
Additionally, light affects the expression of genes encoding
enzymes, including phenyl ammonia-lyase (PAL), chalcone
synthase, and flavanone-3-hydroxylase, among others, in-
volved in various processes (Dutta Gupta 2017).
In blueberries fruit, treatment with LEDs blue light (470
nm) significantly increases the total phenolic content at a
fluence rate of 40 W m
−2
after treatment (Xu et al. 2014a,
2014b). In addition, After 3 days of red (630 nm), blue (463
nm), and green treatment (520 nm) at a fluence rate of 20 W
m
−2
in the blueberry (Vaccinium) fruit, the content of non-
flavonoids including ascorbic, chlorogenic, caffeic acid, and
rutin in blueberries showed a maximum increasing trend over-
all. However, the content of phenolic compounds was signif-
icantly increased (Kim et al. 2011). Similar results have been
reported for immature broccoli treated with blue (660 nm)
LEDs, showing a positive effect on the phenolic compounds
within 7 days of storage (Zhan et al. 2012a,2012b). Some
recent studies have shown that LED treatment increases the
phenolic content in blueberries at 12 and 24 h (Patel 2014).
Also, several studies have reported that the application of blue
(450 nm, 440 nm, 450 nm, 470 nm, 456 nm, 405 nm, 465 nm,
and 460 nm) LED light enhanced the phenolic content during
storage of Tartary buckwheat sprouts (Fagopyrum sp.) (Thwe
et al. 2014), grape (Vitis sp.) (González et al. 2015), citrus fruit
(Citrus sp.) (Ballester and Lafuente 2017a), Chinese foxglove
(Rehmannia sp.) (Ahn et al. 2015), cherry tomato (Solanum
sp.) (Kim et al. 2014), kalanchoe pinata (Nascimento et al.
2013), strawberry fruit (Fragaria sp.) (Choi et al. 2013), and
lettuce (Lactuca sp.) (Son and Oh 2013). The increased con-
tents of phenolic, ascorbic acid, and acidity were observed in
immature strawberry fruits (Fragaria sp.) treated with blue (λ
= 470 nm) LED light at a fluence rate 40 W m
−2
for 12 days at
5 °C, as compared with control samples; also, the sugar con-
tent was significantly decreased during the initial 6 days of
treatment in both the control and treated samples, followed by
an increase in the later stage of storage (Kim et al. 2011). After
2 days of LED treatment in strawberries, the content of total
phenol showed an increasing trend overall compared with the
untreated samples (Kim et al. 2011;Wangetal.2009).
Furthermore, the significant increase in the phenolic com-
pound could be attributed to the substantial decrease in acidity
and organic acids over time, which aid in the provision of
carbon skeletons for the formation of phenolic compounds
(Wang et al. 2009). Similarly, the application of blue (436
nm), green (524 nm), and red (665 nm) LEDs on cabbage
Brassica oleracea L.) vegetable inhibited the increase of phe-
nolic content, total chlorophyll, and vitamin C during posthar-
vest storage (Lee et al. 2014a,2014b). On the other hand, UV-
LED treatment increases the production of flavonoids content
(Yang et al. 2019).
Anthocyanin Content
Different fluence rates and wavelengths affect the anthocyanin
content of fruits and vegetables during the postharvest period
Food Bioprocess Technol
Table 2 Effect of LED treatment on the secondary metabolites of fruits and vegetables during postharvest storage
Treated fruit/vegetable LED types Treatments Results Reference
Blueberries (Vaccinium) Red (630 nm),blue (463
nm), and green
(520 nm)
3 days of treatment at 20 °C at
a fluence rate of 20 W m
−2
After 3 days of LED treatment, the
content of non-flavonoids, including
ascorbic, chlorogenic, caffeic acid,
and rutin in blueberries, showed a
maximum increasing trend overall.
However, the content of phenolic
compounds was significantly
increased.
Kim et al. 2011
Immature strawberries
(Fragaria ananassa)
Blue (470 nm) LEDs 12 days of treatment at a
fluence rate 40 W m
−2
After 4 days of LED treatment, the
content of total phenolic was found
to increase by 13% for 4 days at 5 °C
Kim et al. 2011
Immature broccoli Blue (525 nm) LEDs 7 days of treatment at 2 °C at a
fluence rate of 20 W m
−2
After 7 days of LED treatment, the
content of total phenolic was
increased by 1.8% than the control
untreated sample
Zhan et al. 2012a,
2012b
Blueberries (Vaccinium)Blue(470nm),
red (525 nm), and
green (630 nm)
10 days of treatment at a
fluence rate of 20 and
60 W m
−2
at 2 °C
and 40 W m
−2
at 21 °C
Blue, red, and green LED treatment,
both increased the content of
anthocyanin in blueberries fruits for
10 days at 2 °C and 21 °C
Shi et al. 2014
Sweet cherries
(Prunus avium L.)
UV-B (310 nm), blue
(450 nm), a
combination of white,
blue and green LED
light (450, 473, and
532 respectively)
10 days of treatment at a
fluence rate of 23, 0.046,
3.6, and 0.02 W m
−2
at 1 ± 0.5 °C
Blue LED treatment, increased the
content of anthocyanin in sweet
cherries for 10 days at1 ± 0.5 °C
(cyaniding 3 Oglucoside, cyanidin
3-O-rutinoside) and significantly
influenced the CIE color parameters.
Furthermore, a Combination of
white-blue-green light provoked
similar but less pronounced effects,
while UV-B light was similar to
Control untreated sample. Blue and
white-blue-green light treatment in-
creased the phenylalanine
ammonia-lyase activity. Light irra-
diation had no significant impact on
ascorbic acid and the phenolic pro-
file after 10 days of storage.
(Kokalj et al. 2019)
Grape berries (Vitis
labruscana Bailey
cv ‘Campbell Early’
and ‘Kyoho’)
Blue LED light
(445 nm)
9 days of treatment at a
fluence rate of 80 W m
−2
at
15–25 °C
Blue LED treatment enhances the
content of anthocyanin for 9 days at
optimal temperature 15–20 °C
without a decline in titratable acidity
and berry weight. The expression
levels of anthocyanin
biosynthesis-related genes
also increased significantly and co-
ordinately by light
and temperature.
(Azuma et al. 2019)
Strawberry (Fragaria ×
ananassa)fruit
Red, yellow, green,
blue, and white LED
7 days of treatment at a
fluence rate of 520 W
m
−2
at 30 °C
Red and yellow LED treatment
maintained high significant
increased in total anthocyanin
content at 7 days; green, blue, and
white LED treatment both reduce
the total anthocyanin content
at 30 °C
(Miao et al. 2016)
Red Chinese sand pears fruit
(Pyrus pyrifoliaNakai)
White LEDs (765 nm)
and UV-B LED
(315 nm)
10 days of treatment at a
fluence rate of 532 and
270 W m
−2
at 32 °C
White and UV-B LED treatment en-
hanced the accumulation of antho-
cyanin content for 10 days at 32 °C
compared with the control untreated
sample.
(Sun et al. 2014)
Food Bioprocess Technol
(Table 2). However, at the postharvest stage, minimal studies
have examined the effect of light on anthocyanin content
(Kim et al. 2011). LEDs modulate anthocyanin biosynthesis
by controlling the expression of anthocyanin synthesis genes
in some fruit such as Chinese bayberry fruit (Myrica rubra
Sieb) and immature strawberry (Fragaria sp.) (Shi et al.
2014). In addition, the application of blue (470 nm), red
(525 nm), and green (630 nm) LED treatment at a fluence rate
of 20 and 60 W m
−2
and 40 W m
−2
)increased the content of
anthocyanin in blueberries fruits for 10 days at 2 °C and 21 °C
(Shi et al. 2014). Similarly, the application of UV-B (310 nm),
blue (450 nm), a combination of white, blue and green LED
light (450, 473, and 532 respectively) at a fluence rate of 23,
0.046, 3.6, and 0.02 W m
−2
increased the content of anthocy-
anin in sweet cherries fruit for 10 days at 1 ± 0.5 °C (cyaniding
3 Oglucoside, cyanidin 3-O-rutinoside) and significantly in-
fluenced the CIE color parameters. Furthermore, a
combination of white-blue-green light provoked similar but
less pronounced effects, while UV-B light was similar to the
control untreated sample (Kokalj et al. 2019). Also, some
studies have reported for red-leaf cabbage (Brassica oleracea
L.), buckwheat sprouts (Fagopyrum sp.), red leaf lettuce
(Lactuca sp.), and Chinese kale sprouts (Brassica sp.) with
red, blue light, and far-red light LEDs maintaining the green
color during the postharvest period (Seo et al. 2015; Shi et al.
2014). In the strawberry fruit, anthocyanin content increased
during LED treatment compared with the control samples (Xu
et al. 2014a,2014b). Similar results were also reported for
Chinese bayberries (Myrica rubra Sieb)at40Wm
−2
for 8
days, where blue light treatment significantly increased the
anthocyanin content (Shi et al. 2014). Conversely, blue LED
treatment enhanced the anthocyanin content of strawberry
fruit both at the ripening stage and during postharvest storage
(Bantis et al. 2016; Kadomura-Ishikawa et al. 2013;Xuetal.
Table 2 (continued)
Treated fruit/vegetable LED types Treatments Results Reference
Grape Berries
(Gros Colman)
White (352 nm) and UV
(530 nm) LEDs
72 h of treatment at a fluence
rate of 20, 24, and 60 W
m
−2
at 25 °C
After 72 h treatment, total anthocyanin
content (TAC) was markedly in-
creased by white light. However,
Under UV LED, a considerable
amount of TAC also accumulated
relative to dark conditions. As white
and UV LED intensities increased,
TAC gradually enhanced, but this
promoting the effect of light on the
accumulation of anthocyanin was
saturated at 60 W m
−2
for white and
24 W m
−2
for UV.
(Kataoka et al. 2004)
Octaploid strawberries
(Fragaria ananassa) fruit
White LEDs 8 days of treatment at a
fluence rate of 110 W m
−2
at 23 °C
White LED treatment controlled the
content of anthocyanin biosynthesis
via activation of FaMYB10
expression. Furthermore, FaMYB10
accelerated anthocyanin synthesis of
pelargonidin 3-glucoside and
cyaniding 3-glucoside during straw-
berry fruit ripening for 8 days at 23
°C.
(Kadomura-Ishikawa
et al. 2015)
Grape berries
(Vitis ×labruscana)
Blue (460 nm)
and red (640 nm)
24 h of treatment at a fluence
rate of 41 and 42 W m
−2
Blue and red LED treatment
significantly increases the content of
anthocyanin in berry grape for 24 h
compared with the control sample;
however, the content of the
expression of anthocyanin
biosynthesis-related genes, includ-
ing VlMYBA1-3, VlMYBA2,
F3’5’H, and UFGT, was higher in
the treated sample than in control.
(Azuma et al. 2012)
Kyoho’grapevines (Vitis
labrusca × V. vinifera)
Red (660 nm) and blue
(450 nm) LEDs
10 days of treatment at a
fluence rate of 50 W m
−2
at 35 °C
Blue and red LED treatment increases
the anthocyanin accumulation and
enhanced the expressions of
VvUFGT, VlMYBA1
−2
,and
VlMYBA2 for 10 days at 35 °C
(Rodyoung
et al. 2016)
Food Bioprocess Technol
2014a,2014b). In the previous study, treatment with blue light
LEDs shown to induce anthocyanin accumulation and total
flavonoid content in Chinese herbal medicine during storage
(Ren et al. 2014) and Chinese kale fruit (Brassica sp.) (Qian
et al. 2016). Nevertheless, it has been reported that LED treat-
ment has a positive influence on the anthocyanin accumula-
tion in grapes (Vitis sp.) and leaf baby lettuce (Lactuca sativa)
(Kondo et al. 2014; Samuoliene et al. 2012).
The effect of different LED treatments blue, red, and green
(385 nm, 470 nm, 525 nm, and 630 nm) in immature straw-
berries (Fragaria ananassa) at 5 °C for 4 days was reported
compared with control samples (Kim et al. 2011). The antho-
cyanin content showed a significant increase by 21% in the
treated strawberries during storage compared withthe untreat-
ed controls, as a result of variable light wavelengths, which
resulted in an increased of anthocyanin via the expression and
enzymatic activities of genes such as chalcone isomerase
(FaCHI), flavanone 3-hydroxylase (FaF3H), and
anthocyanidin synthase (FaANS) (Kim et al. 2011).
Additionally, when photoreceptors respond to light signals,
they coordinate anthocyanin biosynthesis. compared with
green and red LEDs, phototropin such as FaPHOT2 respond
to blue LEDs mostly involved in inducing flavonoid pathway
gene expression for the accumulation of anthocyanin and oth-
er flavonoids (Kadomura-Ishikawa et al. 2013). Similarly, the
application of blue LED light at a fluence rate (40 W m
−2
)for
8 days on Chinese bayberries fruit (Myrica rubra) inhibited
the increased of anthocyanin content by 1.8% compared with
the untreated control samples (Gupta et al. 2017; Shi et al.
2014). Blue light induces the expression of genes involved
in the synthesis of pigments such as anthocyanin, including
MrMYB1, MrANS, MrF3H, and MrDFR1 (Gupta et al. 2017;
Shi et al. 2014).
Influence of LEDs (NBI) on Nutritional Parameters in
Postharvest Fruits and Vegetables
Light stimulates the making of several secondary metabolites,
nutrients content as well as an antioxidant which supply
(ROS) in the course of photosynthesis (Darko et al. 2014).
LEDs intensify the redolent characteristics of fresh horticul-
tural products (Colquhoun et al. 2013), also improve the nu-
tritive value of horticultural crops atthe postharvest level, and
increase the accumulation of vitamin C, anthocyanin, and total
phenolic compounds (Table 3) (Dutta Gupta et al. 2017a;
D’Souza et al. 2015). Thus, the treatment of fruit with LEDs
of different light (wavelength) helps to maintain the nutritional
quality in the postharvest stage (Samuoliene et al. 2013). The
effect of the different types of LEDs diverse for a variety of
fruits and vegetables, affecting their nutritional value and
thereby affecting their functional components and quality
(Muneer et al. 2014). The use of LEDs has made the applica-
tion of monochromatic light convenient with well-defined
wavelengths and emission intensities. Thus, blue (400-470
nm) and red (600-650 nm) LEDs reported having a significant
effect on nutritional value (Colquhoun et al. 2013; Holopainen
et al. 2018;Taulavuorietal.2017). For instance, blue light is
associated with its effect on various metabolic pathways and
accumulation of phenolic compounds, carotenoid, anthocya-
nin, ascorbic acid, and polyphenols (Taulavuori et al. 2017).
In contrast, red light regulates the concentration of phyto-
chemicals like terpenes, sesquiterpenes, and tocopherols in
fruits and vegetables (Holopainen et al. 2018). The influence
of different types of LEDs (wavelength) on fresh horticultural
produce varies because of the impact generated by the lights
on the specific receptors in fruits and vegetables (Samuoliene
et al. 2013). Kitayama et al. (2019), studied the effect of LED
light superiority, fluence rate, and photoperiod on the nutri-
tional increase in many fruits and vegetables in controlled
conditions. In general, studies have shown that LED treatment
of different colors red (665 nm), blue (436 nm), green (524
nm), and white (375 nm) improve the nutritional quality and
other bioactive compounds of some harvested fruits and veg-
etables during the postharvest period such as Chinese bayber-
ry fruit (Myrica rubra Sieb), cabbage (Brassica oleracea L.),
broccoli (Brassica oleracea), romaine lettuce (Lactuca sp.),
spinach Spinacia oleracea), and pea seedling (Kanazawa
et al. 2012; Lee et al. 2014a,2014b;Lesteretal.2010; Zhan
et al. 2012a). It also reported that during postharvest storage,
chlorophyll, vitamin C, and total phenolic content were sig-
nificantly increased by LED light (Zhan et al. 2012b).
Consequently, the use of a particular wavelength supports
the initiation of responses in fruits and vegetables, which
may lead to the enrichment of functional compounds
(Table 3). These findings demonstrated that the nutritional
value of fruits and vegetables is enhanced by the application
of LEDs of different colors/wavelengths during postharvest
storage. However, ultraviolet (UV) LEDs are not part of the
visible spectrum; they are suited for postharvest storage, im-
proving nutritive value and retarding microbial growth in
fruits and vegetables (Yang et al. 2019). The higher increase
in quercetin-glycoside was observed in garden pea sprouts and
watercress by UV-A LED (375 nm) at a fluence rate of 33 W
m
−2
for 5 days (Kanazawa et al. 2012). Also, proper UV LED
exposure improved phytochemical traits of fruits and vegeta-
bles (Luksiene and Zukauskas 2009).
The precise biological processes of how nutrients improved
through light are not fully understood. But current studies
seem to move towards tracing the modifications in terms of
biochemical response and comparing in nutrition with an ex-
pression of the gene via techniques like real-time- quantitative
reverse transcription-polymerase chain reaction (qRT-PCR)
investigation (Park et al. 2020). Consequently, the tractability
in modification LEDs (optimum spectral composition) would
be convenient in discovery the (OSP) of light for fresh horti-
cultural crops, and well understanding of biological responses
Food Bioprocess Technol