Physio-chemical behavior of g-irradiated garlic bulbs under ambient
storage conditions
Pallavi Sharma a, *
, S.R. Sharma a
, R.K. Dhall b
, T.C. Mittal a
, Surekha Bhatia a
a
Department of Processing and Food Engineering, College of Agricultural Engineering and Technology, PAU, Ludhiana, India
b
Department of Vegetable Science, College of Horticulture, PAU, Ludhiana, India
a r t i c l e i n f o
Article history:
Received 6 April 2020
Received in revised form
5 May 2020
Accepted 5 May 2020
Available online 21 May 2020
Keywords:
Allicin content
Garlic
Irradiation
Marketable
Sprouting
a b s t r a c t
The present study was undertaken to study the effect of different gamma irradiation doses on storage life
of garlic bulbs under ambient storage conditions. Garlic bulbs (cv. PG-18) were irradiated with gamma
rays in dose range of 0e0.2 kGy and stored under ambient conditions (Temp 27e35
C and RH 34e76%).
Physical and chemical quality parameters i.e. physiological loss in weight (plw), rotting, sprouting, total
soluble solids, firmness, ascorbic acid and allicin content of garlic bulbs was determined fortnightly to
assess its storage life. On 195th day of ambient storage, the weight loss of bulbs ranged from 32.22 to
38.48% in all irradiation doses. It was observed that upto 30 days and 150 days, there was no rotting and
sprouting, respectively in all the treatments. Firmness, total soluble solids, ascorbic acid and allicin
content were significantly different with storage period and irradiation dose levels. It is concluded that
garlic bulbs irradiated @ 0.12 kGy of gamma radiation resulted in minimum post-harvest losses along
with maintaining their marketable shelf life for 4 months under ambient storage conditions.
© 2020 Elsevier Ltd. All rights reserved.
1. Introduction
Garlic is one of the important spices and condiment crops of
world. Garlic is either consumed in raw form as vegetable
seasoning or in processed form as garlic oil, garlic extracts and
garlic powder with differences in chemical composition and
bioactive contents of these forms (Lanzotti et al., 2014). It has
antioxidant and antimicrobial properties which help in reduction of
cardiovascular diseases, cancer and increased detoxification of
foreign compounds (Aviello et al., 2009; Gonzalez et al., 2012).
India ranks second in world's total area and production of garlic
next to China. In Punjab, garlic is harvested in AprileMay and then
stored for about 4e5 months with periodic marketing. Almost 80% of
garlic produce is stored and made available for domestic supply,
therefore, it is mainlystored from May to February. During the storage
of garlic, major losses are sprouting, weight loss and infection to
diseases. Dhall and Ahuja (2013) suggested that the garlic can be
stored near 0 C but these garlic sprouts immediate after bringing out
from cold chambers. Garlic is commercially stored in a cool, dry, well-
ventilated place in containers under ambient conditions. However,
storage life of garlic under such conditions is 3e5 months with total
storage losses of 30e45% under ambient conditions. Therefore, some
technology is required to extend storage life of garlic bulbs under
ambient conditions with minimum quality losses. The gamma irra-
diation is an emerging preservation technology for post-harvest
treatment for such crops. On a commercial scale, India is one of the
first countries in the world to demonstrate the feasibility of irradia-
tion as a phytosanitary usage for treatment of mango in 2007. The
large-scale storage studies on irradiated commodities like onion,
garlic, potato and grains involving traders and end-users were also
being carried out in a few decades. Efficiency of low dose of gamma
radiation (0.01 kGy) in sprout inhibition and stopping the process of
mitosis in garlic have been reported by Pellegrini et al. (2000). Also,
Pellegrini et al. (2000) evaluated that high doses of radiation used
commercially for garlic caused complete sprout and mitosis (due to
nuclear aberrations) inhibition whereas lower doses of 0.01 kGy
applied in post-dormancy reduce sprouting and stop mitosis. Inhi-
bition was mainly observed after 150 days of harvest. Gamma-ray
irradiation followed by cold storage minimized the storage losses by
15%e20% and increased the shelf life of garlic (Allium sativum) as re-
ported by Tripathi and Lawande (2007). Perez et al. (2007) observed
that irradiation of garlic bulbs at dose of 0.06 kGy when stored for 8
months resulted in significant reduction in lipid and fatty acid con-
tents, with a concomitant reduction of garlic bulbs sprouting occur-
rence. Un-irradiated cold stored garlic showed rapid sprouting during
post cold storage period but this low temperature induced sprouting
was not noticed in g-ray irradiated cold stored garlic after storage.
* Corresponding author.
E-mail address: psharma9136@yahoo.com (P. Sharma).
Contents lists available at ScienceDirect
Journal of Stored Products Research
journal homepage: www.elsevier.com/locate/jspr
https://doi.org/10.1016/j.jspr.2020.101629
0022-474X/© 2020 Elsevier Ltd. All rights reserved.
Journal of Stored Products Research 87 (2020) 101629

Moreover, trisaccharides averaged 12%, while tetra-saccharides
averaged 10% of total carbohydrates. These studies showed very
encouraging results in terms of prevention of storage losses, retention
of the processing abilityand marketability of the commodity (Sharma
and Madhusoodanan, 2012). Moreover, reduction of microbial
contamination and replacement in application of chemical fungicides
during the post-harvesting period respectively are the other recom-
mended uses ofgamma irradiation(Thomas,1999).Thepresentpaper
deals with the physio-chemical behavior of irradiated garlic bulbs
under ambient storage conditions.
2. Materials and methods
2.1. Procurement of fresh produce
Garlic variety PG-18 was used for the experiment. Bulbs of
mentioned variety are large (4.55 cm diameter) and white with
average bulb weight of 28.4 g having 26 cloves per bulb whereas
cloves are medium to large sized and white in color. Garlic var. ‘PG-
18’ was procured from PAU's progressive farmer at district Ropar on
15th April 2019. Bulbs which were shade cured for 15 days were
Fig. 1. Gamma iradiation treatment and ambient storage of garlic bulbs.
Fig. 2. Variation of Temperature and relative humidity during storage.
P. Sharma et al. / Journal of Stored Products Research 87 (2020) 101629
2

used for the study. Then, manual grading of garlic bulbs was done
and medium size bulbs of weight 25 g were used. A total of 100 kg
of cured and graded garlic bulbs were used for the experiment
(Fig. 1), of which 20 kg was kept as control (0 kGy) whereas 20 kg
each was treated with four different doses of gamma irradiation i.e.
0.01, 0.06, 0.12 and 0.2 kGy.
2.2. Irradiation treatment to bulbs
Garlic bulbs were treated with different dose of gamma rays
within the range of 0e0.2 kGy at Punjab Agricultural University,
Ludhiana using Co60
gamma cell (Model: BI 2000; PAU Ludhiana)
(Fig. 1). The operating dose rate of gamma chamber was 3.465 Gy/
min. Doses of gamma-rays used were 0.01, 0.06, 0.12 and 0.2 kGy
and their time of exposure was 2 min 49 s, 19 min 18 s, 38 min 37 s
and 63 min 48 s, respectively. The garlic bulbs which were non-
irradiated were stored as non-treated (0 kGy).
2.3. Storage of bulbs
Storage of garlic bulbs, 20 kg from each dose level (non-treated
and treated) was done in crates made of plastic and ventilated at
the bottom as well as from sides under ambient conditions for 195
days (15th April to 10h
October). The variation of temperature and
relative humidity during storage period was monitored under
ambient conditions (Fig. 2).
2.4. Evaluation of physico-chemical attributes
The garlic bulbs were randomly selected from the crates to re-
cord observations on various physico-chemical attributes. The
physical parameters observed were physiological loss in weight (%),
sprouting (%), rotting (%), firmness (N) and color (L, a, b and DE)
whereas chemical parameters observed were total soluble solids
(%), ascorbic acid (mg/100 g F.W.) and allicin content (mmolmL1
F.W.). All above mentioned parameters were evaluated at fort-
nightly interval during storage period of 195 days.
2.4.1. Physiological loss in weight (PLW), rotting and sprouting
percentage
The garlic bulbs from each dose level of gamma rays were
weighed fortnightly i.e. after 15 days during storage at ambient
storage conditions. Weight loss, sprouting and rotting were
measured were measured on the basis of weight of the bulbs loss,
rotted and sprouted on 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, 165,
180, 195 days of storage similar to the method adopted by Sharma
et al. (2020). The physiological loss in weight, sprouting and rotting
percentage were expressed as formulae given below.
Rotting ð%Þ ¼
Weight of rotted bulbs 100
Initial weight of bulbs
Sprouting ð%Þ ¼
Weight of prouted bulbs 100
Initial weight of bulbs
2.4.2. Firmness, color and total soluble solids
The average of firmness i.e. resistance offered by the bulb to the
penetration of garlic bulbs was analyzed by similar method adop-
ted by (Sharma et al., 2020) using TX-XT2i Texture Analyzer (Stable
Microsystems) with the load cell of 50 Kg using P/2N needle probe
of 2 mm, 2 mm/s and 10 mm of diameter, speed and penetration
depth respectively.
During storage color of garlic bulbs from all the treatments was
read using a Color Reader CR-10 colorimeter calibrated using white
and black plate (Konika Minolta Sensing Inc.) (Hunter, 1975) and a
CIE standard illuminant C to determine CIE color space coordinates,
tristimulus value i.e. ‘L’, ‘a’ and ‘b’ values directly. Readings given by
colorimeters can be correlated with human eyeebrain perception
(Pathare et al., 2013).
Change in color was mainly measured by the modulus of the
distance vector between the initial color values and the values at
particular storage interval which is known as total color difference
(Pathare et al., 2013).
The total color difference (DE) was evaluated using given
formulae:
DE ¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
Lfinal Linitial
2
þ
afinal ainitial
r 2
þ
bfinal binitial
2
Color difference can also be classified according to small dif-
ference, distinct and very distinct, with DE value of range 1.5 DE,
1.5 DE3 and DE3 respectively (Pathare et al., 2013).
The total soluble solids (TSS) content was recorded with the
help of digital refractometer calibrated with distilled water and
expressed as %.
2.4.3. Ascorbic acid (mg100 g1
FW)
Garlic (0.5 g) were crushed in pestle and mortar using 10 mL of
metaphosphoric acid-acetic acid solution and then filtered. Filtered
extract known as aliquot (5 mL) was titrated against dye till the
appearance of light pink colour and the volume of dye used to
oxidize vitamin C in sample was noted (AOAC, 1990). Ascorbic acid
content was calculated by titrating the standard ascorbic acid (0.2
mgmL1
) with dye as given below.
PLW ð%Þ ¼
ðInitial weight of bulbs weight of bulbs at particular time intervalÞ 100
Initial weigh of the bulbs
Ascorbic acid
mg
100g
¼
Dye factor Titre value volume of solution made from sample 100
aliquot taken weight of sample
P. Sharma et al. / Journal of Stored Products Research 87 (2020) 101629 3

Dye factor ¼
0:5
Titre value
2.4.4. Allicin content (mmolmL1
)
Allicin was determined using the modified spectrophotometric
method by Han et al. (1995). For allicin determination 1 mL of
20 mM L-cysteine solution was mixed with 1 mL of garlic solution
and mixture was incubated at room temperature for 15 min. 1.5 mL
of above solution was added to 5 mL of DTNB, 10 mL of tris buffer
(1 M) and 83.5 mL of water to make 100 mL volume. Blank sample
was prepared by adding 5 mL DTNB, 10 mL tris buffer and 85 mL
distilled water. The amount of 2- nitro-5 thiobenzoate (NTB) was
determined by measuring the absorbance of the reaction mixture at
412 nm in UV spectrophotometer having model number UV-2601
of Rayleigh Company. The concentration of liberated NTB in sam-
ples was calculated from their absorbance at 412 nm, using molar
absorption coefficient of 14150 for NTB anion. The amount of NTB
(mM) is equal to the concentration of unreacted cysteine in each
sample.
Allicin was quantified using the following equations (Zhou et al.,
2015):
DA412 ¼ A0 A
Callicin
mmolmL1
¼ ðDA412 bÞ
.
ð2 14; 150 1000Þ
where, b ¼ The dilution of L-Cysteine
14,150 ¼ The molar Extinction coefficient (E) of allicin in water
A0 ¼ The absorbance reading of water
A ¼ The absorbance reading of allicin
2.4.5. Statistical analysis
The experimental design was randomized design in which doses
of irradiation and storage were considered as main factors. The
statistical software SAS (version 9.2 SAS software, USA) was used to
analyze data using ANOVA and LSD means. The factorial completely
randomized design (Factorial-CRD) was used for the experiment by
calculating three replications per treatment. Statistically significant
differences among means of different irradiation levels and storage
period were identified using at a 5% level of significance using Least
significant difference test of the General Linear Model procedure.
3. Results
3.1. Physiological loss in weight (PLW %)
It was observed that upto 120 days storage period, there was
gradual increase in percentage weight loss in all the treatments but
thereafter, there was rapid increase in PLW which might be due to
change in temperature and humidity in the environment (Table 1).
On 120th day of storage, PLW in non-treated (0 kGy) and maximum
irradiated (0.2 kGy) bulbs were higher than the bulbs treated with
other irradiation doses (0.01, 0.06 and 0.02 kGy). The PLW after 120
days of storage was 28.37, 25.81, 23.98, 21.65 and 28.32% in garlic
bulbs irradiated with 0, 0.01, 0.06, 0.12 and 0.2 kGy gamma dose
levels respectively (Table 1). The loss in weight after 195 days of
storage was 37.78, 36.55, 36.53, 32.22 and 38.48% for bulbs irradi-
ated @ 0, 0.01, 0.06, 0.12 and 0.2 kGy dose levels of gamma rays,
respectively. After 195 days, higher PLW was observed in control
(0 kGy) and 0.2 kGy treatment whereas minimum PLW was found
in the bulbs irradiated @ 0.12 kGy which may be due to less
moisture loss, sprouting and rotting in the bulbs. Therefore, storage
life of gamma radiated garlic bulbs can be considered for 120 days
at ambient temperature when irradiated @ 0.12 kGy with PLW of
21.65%.
3.2. Rotting (%)
Rotting percentage significantly (p 0.05) increased with in-
crease in storage period in all the treatments. It was observed that
during initial storage period i.e. upto 30 days no rotting was found
in stored bulbs (Table 1). No considerable rotting in garlic bulbs was
observed on 45th day of ambient storage and then after 120 days
rotting was 8.45, 6.02, 5.29, 3.54 and 10.74% for bulbs treated @ 0,
0.01, 0.06, 0.12 and 0.2 kGy dose levels of gamma rays respectively.
Higher rotting percentage was found in non-treated (0 kGy) bulbs
as well as bulbs irradiated @ maximum dose i.e. 0.2 kGy on 120th
day of storage (Fig. 8). Rotting percentage after 195 days of storage
was found to be 26.06, 18.50, 12.80, 8.76 and 23.01% for the bulbs
treated @ 0, 0.01, 0.06, 0.12 and 0.2 kGy gamma dose levels
respectively. It was observed that rotting was higher in non-treated
and bulbs treated @ 0.2 kGy gamma dose level after 195 days of the
storage as compared with irradiation dose levels.
3.3. Sprouting (%)
Under ambient storage conditions, it was found that both non-
treated and treated garlic bulbs did not sprout until 150 days.
However, there was sprout occurrence observed in garlic bulbs
irradiated @ 0 kGy and 0.01 kGy after 150 days (Table 1). After 195
days of storage, there was no sprouting in the garlic bulbs irradiated
@ 0.06 kGy, 0.12 kGy and 0.2 kGy gamma dose levels, while non-
irradiated (0 kGy) and bulbs irradiated @ 0.01 kGy gamma rays
results sprouting (Fig. 3). The sprouting percentage was found to be
18.63 and 5.72 for the bulbs irradiated @ 0 kGy and 0.01 kGy gamma
dose levels respectively after 195 days of ambient storage.
3.4. Total soluble solids (%)
Total soluble solids of garlic bulbs treated with different doses of
irradiation were significantly (p 0.05) different during ambient
storage. Under ambient temperature, total soluble solids firstly
increased upto 90 days and after that it decreased till 195 days of
storage in all the treatments (Fig. 4.). After 96 days of storage under
ambient storage conditions, total soluble solids increased from
32.6% to 42.1, 46.2, 43.2, 45.6 and 42.8% for the gamma radiated
bulbs treated @ 0, 0.01, 0.06, 0.12 and 0.2 kGy, dose levels respec-
tively. The total soluble solids increased from 32.6% to 36.8, 36.3,
35.4, 33.2 and 36.6% for the gamma radiated bulbs treated with the
dose of 0, 0.01, 0.06, 0.12 and 0.2 kGy respectively after 195 days of
ambient storage. The final total solids content obtained at the end
of the storage of 195 days was higher than content before storage in
all the treatments.
3.5. Firmness (N)
During storage, different irradiation dose levels caused signifi-
cant (p 0.05) difference in the firmness bulbs. It was observed
that, firmness of bulbs in all the treatments gradually decreased
during storage (Fig. 5). Firmness decreased initially from 16.611 N to
4.282, 4.557, 4.645, 5.733 and 4.341 N on 120th day of storage for
bulbs irradiated @ 0, 0.01, 0.06, 0.12 and 0.2 kGy gamma dose levels,
respectively. It was found that on 120th day of storage, bulbs irra-
diated @ 0.12 kGy gamma dose were firmer than other irradiated
bulbs. Firmness on 195th days of storage was found to be 1.509,
P. Sharma et al. / Journal of Stored Products Research 87 (2020) 101629
4

Table 1
Effect of irradiation doses on Physiological loss in weigh t (%), rotting (%) and sprouting (%) of garlic bulbs during storage.
Storage period
(Days)
Physiological loss in weight (%) Rotting (%) Sprouting (%)
0 kGy 0.01 kGy 0.06 kGy 0.12 kGy 0.2 kGy 0 kGy 0.01 kGy 0.06 kGy 0.12 kGy 0.2 kGy 0 kGy 0.01 kGy 0.06 kGy 0.12 kGy 0.2 kGy
0 0 Am
0 An
0 Am
0 Ae
0 An
0Ak
0Ak
0Ah
0Ab
0Al
0Ad
0Ab
0Ca
0Ca
0Ca
15 5.69±
0.012Al
2.99±
0.019Dm
3.20±
0.018Cl
3.87 ± 0.019Bed
2.63±
0.015Em
0Ak
0Ak
0Ah
0Ab
0Al
0Ad
0Ab
0Ca
0Ca
0Ca
30 7.40±
0.021Ak
4.66±
0.027Dl
5.34±
0.022Bk
5.15 ± 0.022Ced
4.23±
0.021El
0Ak
0Ak
0Ah
0Ab
0Al
0Ad
0Ab
0Ca
0Ca
0Ca
45 8.63±
0.030Aj
5.50±
0.028Dk
5.92±
0.016Cj
6.01 ± 0.021Bced
5.46±
0.023Dk
0.38±
0.045Aj
0.19±
0.050Dj
0.12±
0.004Ch
0.09±
0.002Ab
0.28±
0.004Bk
0Ad
0Ab
0Ca
0Ca
0Ca
60 12.43±
0.062Ai
8.12±
0.034Ej
9.13±
0.194Bi
9.02 ± 0.025Cced
8.28±
0.029Dj
0.83±
0.002Aj
0.29±
0.004Ci
0.24±
0.002Bh
0.18±
0.003Db
0.37±
0.001Cj
0Ad
0Ab
0Ca
0Ca
0Ca
75 11.95±
0.068Ai
9.20±
0.033Di
10.19±
0.007Ch
10.65 ± 0.023Cced
10.91±
0.031Bi
1.59±
0.003Ai
0.79±
0.003Bh
0.72±
0.009Bh
0.35±
0.001Cb
0.84±
0.007Bi
0Ad
0Ab
0Ca
0Ca
0Ca
90 16.32±
0.069Bh
15.53±
0.044Ch
14.95±
0.053Dg
14.09 ± 0.020Eced
17.69±
0.037Ah
2.47±
0.008Bi
1.29±
0.001Ch
0.84±
0.006Dg
0.62±
0.005Eb
2.91±
0.014Ah
0Ad
0Ab
0Ca
0Ca
0Ca
105 20.67±
0.132Bg
20.39±
0.043BCg
20.30±
0.086Cf
18.13 ± 0.013Dcebd
21.73±
0.031Ag
4.94±
0.007Bh
2.84±
0.021Dg
2.99±
0.017Cf
1.74±
0.010Eb
5.83±
0.016Ag
0Ad
0Ab
0Ca
0Ca
0Ca
120 28.37±
0.160Af
25.81±
0.036Bf
23.98±
0.051Ce
21.65 ± 0.153Dcbd
28.32±
0.020Af
8.45±
0.002Ag
6.02±
0.019Bf
5.29±
0.018De
3.54±
0.015Eb
10.72±
0.017Cf
0Ad
0Ab
0Ca
0Ca
0Ca
135 30.30±
0.276Be
31.07±
0.028Ce
29.87±
0.048Bd
25.04 ± 0.185Dcb
35.65±
0.277Ae
15.28±
0.001Af
10.68±
0.016Be
7.08±
0.019Ced
4.10±
0.018Db
15.38±
0.023Be
0Ad
0Ab
0Ca
0Ca
0Ca
150 32.79±
0.216Ad
35.67±
0.309Bd
31.63±
0.025Bc
27.24 ± 0.043Cb
36.69±
0.312Ad
20.92±
0.049Ae
13.55±
0.015Bd
8.66±
0.015Ed
6.76±
0.020Db
20.12±
0.045Cd
0Ad
0Ab
0Ca
0Ca
0Ca
165 35.17±
0.187Ac
33.90±
0.310Ac
34.91±
0.272Cbc
30.50 ± 0.064Db
37.06±
0.341Bc
22.57±
0.003Ac
16.90±
0.014Bc
11.16±
0.018Ec
7.92±
0.022Db
22.72±
0.052Cc
3.70±
0.025Ac
1.06±
0.004Bb
0Ca
0Ca
0Ca
180 35.05±
0.128Ab
34.62±
0.345Ab
35.58±
0.573Aba
31.27 ± 0.266Aa
37.63±
0.372Ab
25.82±
0.001Ab
17.2±
0.010 Ab
12.50±
0.016Ab
8.10±
0.019Ab
22.88±
0.062Ab
9.79±
0.022Ab
2.33±
0.012Bb
0Ca
0Ca
0Ca
195 37.78±
0.072Aa
36.55±
0.437Aa
36.53±
0.201Ca
32.22 ± 0.319Bb
38.48±
0.272Da
26.06±
0.010Aa
18.50±
0.012Aa
12.80±
0.007Ca
8.76±
0.021Ca
23.01±
0.014Ba
18.63±
0.036Aa
5.72±
0.011Ba
0Ca
0Ca
0Ca
a-e
Mean ± SD within a column with different superscripts are significantly different (p 0.05).
AI
Mean ± SD within a row with different superscripts are significantly different (p 0.05).
P.
Sharma
et
al.
/
Journal
of
Stored
Products
Research
87
(2020)
101629
5

2.842, 3.155, 3.381 and 3.203 N garlic bulbs irradiated @ 0, 0.01,
0.06, 0.12 and 0.2 kGy gamma dose levels respectively.
3.6. Color
Color is a quality parameter which signifies the appearance of
bulbs and therefore indirectly related to the shelf life of the bulbs. It
was observed that ‘L value’, ‘a value’ and ‘b value’ and total colour
difference (DE) significantly (p 0.05) increased in both control
and irradiated garlic bulbs when under ambient storage conditions
(Table 2). ‘L value’ continuously increased with increase in the
irradiation dose. The ‘L value’ increased from 70.00 to 81.65, 82.00,
81.25, 80.60 and 82.30 for irradiation doses of 0, 0.01, 0.06, 0.12 and
0.2 kGy respectively after 195 days of storage. The ‘a value’ for the
bulbs treated with the 0, 0.01, 0.06, 0.12 kGy at the end of 195 days
increased from 6.70 to 3.15, 2.85, 2.70, 3.10 and 2.95 and
Fig. 3. Sprouting and rotting of garlic bulbs during storage.
Fig. 4. Effect of irradiation doses on total soluble solids (%) of garlic bulbs during storage.
P. Sharma et al. / Journal of Stored Products Research 87 (2020) 101629
6

0.2 kGy respectively. On 195th days of storage, ‘b value’ also
increased from 14.30 to 21.75, 22.40, 21.45, 23.20 and 21.25 for the
samples treated with 0, 0.01, 0.06, 0.12 and 0.2 kGy respectively. On
195th day of storage, the total colour difference gradually increased
to the value of 14.64, 14.17, 12.72, 14.85 and 14.32 for the bulbs
treated with the gamma dose of 0, 0.01, 0.06, 0.12 and 0.2 kGy
respectively (Fig. 6).
3.7. Ascorbic acid (mg100 g1
F.W)
Ascorbic acid decreased significantly (p 0.05) in both non-
radiated and gamma irradiated garlic bulbs during storage. It was
found that ascorbic acid in garlic bulbs decreased in all the treat-
ments during storage under ambient conditions (Fig. 7). From
initial amount of 16.23 mg100 g1
, ascorbic acid content decreased
to 9.78, 9.45, 9.25, 7.90 and 7.77 mg100 g1
, in the garlic bulbs
irradiated @ 0, 0.01, 0.06, 0.12 and 0.2 kGy, gamma dose levels
respectively, after 195 days of storage period. Highest amount of
ascorbic acid was retained by control bulbs. It was observed that
bulbs irradiated @ 0.2 kGy exhibited lowest ascorbic acid as
compared to control (0 kGy) as well as other doses of irradiation.
3.8. Allicin content (mmolmL1
F.W)
During storage period of 195 days, allicin content initially
decreased until 135 days and then increased thereafter till 195 days
(Fig. 8) irrespective of irradiation dose levels. Allicin concentration
in of the garlic bulbs decreased initially from 3.05 mM/ml to 0.355,
0.392, 0.398, 0.417 and 0.590 mmolmL1
on 135th day of storage for
bulbs treated with the dose of 0 kGy, 0.01, 0.06, 0.12 and 0.2 kGy
respectively. Allicin content after 195 days of storage was 1.580,
1.650, 1.740, 1.850 and 1.980 mmolmL1
for the bulbs treated @ 0,
0.01, 0.06, 0.12 and 0.2 kGy gamma dose levels, respectively. The
allicin content significantly decreased (p 0.05) during storage
period. However, the concentration of the allicin in both control
and treated bulbs after 195 days was lower than the initial con-
centration at the beginning of the storage period. Allicin content in
the bulbs also increased with increase in irradiation dosage level.
4. Discussion
In the present study, various physico-chemical attributes were
studied during storage of irradiated garlic bulbs at ambient tem-
perature. Garlic bulbs mainly reduce weight during storage which
is due to respiration and transpiration of the bulbs during storage.
Previous studies also reported that increase in dry matter content
and water loss from the garlic bulbs is the main reason for PLW
(Diriba-Shiferaw et al., 2013). Garlic bulbs which were kept as
control resulted in maximum PLW (28.37%) on 120th day which
proved the effectiveness of gamma irradiation in minimizing post-
harvest losses under ambient conditions. Increase in PLW after 120
days of storage in garlic bulbs irradiated @ 0.2 kGy might be due
reduction in suphur compounds which resulted in more rotting
(Sharma et al., 2020). Rapid increase in PLW in garlic at the end of
storage period might be credited to breakdown of dormancy in
garlic bulbs which ultimately resulted in more sprouting and
rotting. Higher percentage of weight loss in control bulbs as well as
bulbs irradiated @ 0.2 kGy on 195th day might be due to internal
sprout development in non-treated bulbs (Tripathi and Lawande,
2007; Sharma et al., 2020) and structural modification in protein
and carbohydrates which thus reduced quality in the bulbs treated
with 0.2 kGy dose of irradiation. Due to less sprouting and rotting,
the lower percentage of weight loss was found in the bulbs irra-
diated at the dose of 0.12 kGy. Under ambient conditions of storage,
Tripathi and Lawande (2007) observed lower weight loss in irra-
diated garlic bulbs (29.4%) than non-irradiated bulbs (38.9%) after
80 days. Similar range of cumulative weight loss percentage
(25e30%) after 4 months were obtained in garlic bulbs stored at
ambient storage (Diriba Shiferaw et al., 2013) and in onion bulbs
irradiated with similar dose range (Sharma et al., 2020). Therefore,
storage life of gamma radiated garlic bulbs can be considered to be
120 days at ambient temperature when irradiated @ 0.12 kGy with
PLW of 21.65%.
Rapid increase in rotting percentage after 120 days might be due
to breakdown of dormancy, which resulted into sprouting and high
humidity at that time adds to the problem of rotting. Higher per-
centage rotting in non-treated and bulbs treated @ 0.2 kGy gamma
rays, signified that maximum dosage limit (0.2 kGy) of the
Fig. 5. Effect of irradiation doses on firmness (N) of garlic bulbs during storage.
P. Sharma et al. / Journal of Stored Products Research 87 (2020) 101629 7

experimental range i.e. 0-0.2 kGy was found effective in sprout
control in bulbs but did not increased their marketable storage life
with optimum physiochemical quality characteristics. Similar
behavior of rotting in onion bulbs was reported by Sharma et al.
(2020) when irradiated with different doses of irradiation and
stored under ambient conditions. However, garlic bulbs irradiated
@ 0.12 kGy dose level exhibited lower rotting due to lowest phys-
iological loss in weight and no sprouting occurrence.
Sprouting in bulb crops occurs due to breakdown of dormancy
of bulbs. Petropoulos et al. (2016) related sprout development with
moisture and weight loss under long storage conditions as it
resulted in higher metabolic rates and storage losses. It was found
that treatment of garlic bulbs with gamma rays after harvesting and
curing in the dose range of 0e0.01 kGy was ineffective in control-
ling sprouting during storage period of approximately 6 months
under ambient storage which might be due to presence of greater
hormonal compounds i.e. ethylene in bulbs (Nouri and Toofanian,
2001; Sharma et al., 2020). It was also suggested that inhibition
of biosynthetic process of sprout growth by irradiation was mainly
due to its effect on the lipid and fatty acid profile in garlic bulbs
(Perez et al., 2007). Pellegrini et al. (2000) reported that irradiation
with gamma dose of 0.01 kGy inhibited sprouting and stopped
mitosis process in garlic bulbs.
It was suggested that during initial storage period, fructans were
hydrolysed to fructose and resulted in higher total soluble solids. It
was suggested that dormancy period of the bulbs come to an end
with the progress of storage period and emergence of sprouting
which led to synthesized of organic acids from sucrose and resulted
in reduced total soluble content (Sohany et al., 2016).
Firmness is an important quality attribute considered for the
marketability of the bulbs. Generally, loss of firmness in bulbs
occurred due to moisture loss and dry matter loss in bulbs under
ambient storage conditions. After 120 days, bulbs irradiated @
0.12 kGy gamma dose were firmer which could be due to less loss of
moisture, rotting and sprouting at this dose level. Rapid decrease in
firmness value in non-treated samples after 165 days under
ambient conditions may be due to commencement of sprouting in
the bulbs. Therefore, it was suggested that firmness loss in the
bulbs mainly relied upon irradiation effects and storage behavior
i.e. physical and chemical attributes of the garlic bulbs.
Mainly, color intensity increased during irradiation as a conse-
quence of the breakdown of glycosidic linkages and enhanced
glycone formation (Tripathi et al., 2016). It was observed that ‘L
value’, ‘a value’, ‘b value’ and total colour difference of the garlic
Table 2
Effect of irradiation doses on color (L, a, b) of garlic bulbs during storage.
Storage period
(days)
Color
0 kGy 0.01 kGy 0.06 kGy 0.12 kGy 0.2 kGy
0 L 70.00 ± 0.396Aj
70.00 ± 0.396Ah
70.00 ± 0.396Af
70.00 ± 0.396Aj
70.00 ± 0.396Aj
A 6.70 ± 0.042Al
6.70 ± 0.042Am
6.70 ± 0.042Ak
6.70 ± 0.042Al
6.70 ± 0.042Al
B 14.30 ± 0.021Aj
14.30 ± 0.021Al
14.30 ± 0.021Aj
14.30 ± 0.021Ak
14.30 ± 0.021Al
15 L 68.85 ± 0.146Ek
71.30 ± 0.454Cg
70.20 ± 0.397Df
71.75 ± 0.355Bi
73.80 ± 0.417Ah
A 5.40 ± 0.011Ck
4.80 ± 0.041Ac
6.20 ± 0.035Ej
5.45 ± 0.027Dk
5.45 ± 0.004Bf
B 13.25 ± 0.028Ck
17.25 ± 0.110Aj
13.40 ± 0.284Bi
13.35 ± 0.066Cl
14.20 ± 0.020Aj
30 L 72.00 ± 0.204Ci
71.65 ± 0.405Dgf
72.35 ± 0.204Ad
73.00 ± 0.247Bh
72.85 ± 0.309Bf
A 5.40 ± 0.031Cb
4.65 ± 0.042Ab
5.65 ± 0.012Cb
4.45 ± 0.031Be
4.80 ± 0.024Di
B 17.15 ± 0.061Ag
18.60 ± 0.105Bh
15.20 ± 0.086Dh
16.95 ± 0.012Ch
16.40 ± 0.081Ek
45 L 75.45 ± 0.267Ah
71.90 ± 0.356Df
77.30 ± 0.328Ce
74.95 ± 0.318Ej
75.20 ± 0.372Bi
A 5.20 ± 0.033Ec
4.25 ± 0.012Dd
5.30 ± 0.004Aa
4.50 ± 0.006Ca
4.80 ± 0.010Ba
B 18.70 ± 0.053Ei
18.25 ± 0.091Ci
16.45 ± 0.070Ad
17.50 ± 0.074Di
17.20 ± 0.098Bh
60 L 77.45 ± 0.329Af
75.30 ± 0.266Bd
78.65 ± 0.334Ac
79.85 ± 0.226Afe
78.65 ± 0.278Ae
A 5.15 ± 0.025Di
4.40 ± 0.034Ba
5.30 ± 0.018Cf
4.20 ± 0.042Ac
4.50 ± 0.016Cg
B 18.45 ± 0.091Ch
19.55 ± 0.035Ad
18.80 ± 0.040Dk
17.25 ± 0.061Ad
17.75 ± 0.037Bg
75 L 78.75 ± 0.390Bad
75.10 ± 0.159De
80.30 ± 1.703Ab
78.85 ± 0.557BCcbd
78.20 ± 0.105Cdc
A 4.80 ± 0.027Dh
4.10 ± 0.032Ah
4.62 ± 0.006Ef
4.15 ± 0.008Bh
4.55 ± 0.035Cc
B 19.60 ± 0.111Cd
19.70 ± 0.014Bf
19.30 ± 0.068Aa
17.80 ± 0.037Df
18.45 ± 0.078Cg
90 L 79.95 ± 0.509Dg
78.85 ± 0.334Bb
80.75 ± 0.057Ab
79.85 ± 0.057Bcb
79.50 ± 0.168Cd
A 4.80 ± 0.024Aa
3.90 ± 0.003Bl
4.50 ± 0.095Eh
3.75 ± 0.003Cj
4.40 ± 0.025Di
B 19.30 ± 0.123Aa
20.80 ± 0.162Bed
19.40 ± 0.082Ce
17.60 ± 0.025Eg
19.65 ± 0.069Di
105 L 78.85 ± 0.502Ae
79.25 ± 0.056Ce
80.00 ± 0.112Bc
79.85 ± 0.508Afed
80.05 ± 0.226Dg
A 4.70 ± 0.030Cef
3.85 ± 0.006De
4.85 ± 0.258Bc
3.80 ± 0.033Af
4.35 ± 0.030Ek
B 19.20 ± 0.095Ac
20.95 ± 0.089Dk
19.35 ± 0.026Be
20.65 ± 0.132Cj
19.65 ± 0.056El
120 L 80.80 ± 0.457Aa
80.60 ± 0.228Ca
80.90 ± 0.057Cba
80.40 ± 0.170Dg
80.40 ± 0.625Ba
A 4.60 ± 0.013Ck
3.45 ± 0.015Af
4.50 ± 0.035Bi
3.45 ± 0.015Ei
4.20 ± 0.012Dj
B 19.55 ± 0.083Dc
20.15 ± 0.071Bb
19.60 ± 0.055Ef
20.65 ± 0.175Aa
20.70 ± 0.015Cd
135 L 80.90 ± 0.400Cdc
81.05 ± 0.115BCc
81.35 ± 0.288BCc
80.4 ± 0.114BAf
81.24 ± 0.689Ac
A 4.75 ± 0.006Ej
3.45 ± 0.017Bj
4.40 ± 0.257Cf
3.30 ± 0.007Aa
4.20 ± 0.035Dh
B 20.00 ± 0.057De
20.85 ± 0.059Cg
19.80 ± 0.014Eg
21.25 ± 0.030Be
20.20 ± 0.017Ac
150 L 80.10 ± 0.340Bdc
80.40 ± 0.625Bb
81.5 ± 0.173Ab
80.85 ± 0.115Aba
81.40 ± 0.806Bab
A 4.30 ± 0.018Dh
3.30 ± 0.011Bj
4.20 ± 0.003Cd
3.25 ± 0.009Ab
4.25 ± 0.039Cc
B 20.20 ± 0.028Ef
21.80 ± 0.031Be
19.80 ± 0.147Dc
21.40 ± 0.182Ac
20.65 ± 0.190Cf
165 L 81.00 ± 0.229Ce
81.60 ± 0.635Ba
81.70 ± 0.636Bb
80.90 ± 0.687Bac
82.45 ± 0.058Aa
A 4.20 ± 0.015Cd
3.10 ± 0.020Di
3.95 ± 0.017Ef
3.20 ± 0.004Ad
3.75 ± 0.008Bd
B 20.00 ± 0.127Ed
21.80 ± 0.185Ba
19.95 ± 0.204Ab
21.00 ± 0.059Db
21.05 ± 0.164Ce
180 L 81.65 ± 0.115CBa
81.90 ± 0.695Aa
81.25 ± 0.625Aa
80.60 ± 0.798Cb
82.30 ± 0.582CBb
A 3.65 ± 0.011De
2.95 ± 0.017Ek
3.65 ± 0.016Ce
3.12 ± 0.015Bg
3.25 ± 0.032Ab
B 20.05 ± 0.113Cc
21.55 ± 0.198Ab
20.45 ± 0.159Ddc
22.50 ± 0.047Bc
21.80 ± 0.216Aa
195 L 81.65 ± 0.115Ab
82.00 ± 0.754Baa
81.25 ± 0.625BCb
80.60 ± 0.798Cced
82.30 ± 0.582Aa
A 3.15 ± 0.119Dg
2.85 ± 0.015Cj
2.70 ± 0.005Eg
3.10 ± 0.020Ah
2.95 ± 0.013Be
B 21.75 ± 0.092Db
22.40 ± 0.174Aac
21.45 ± 0.015Ec
23.20 ± 0.164Ce
21.25 ± 0.150Bb
a-e
Mean ± SD within a column with different superscripts are significantly different (p 0.05).
AI
Mean ± SD within a row with different superscripts are significantly different (p 0.05).
P. Sharma et al. / Journal of Stored Products Research 87 (2020) 101629
8

bulbs increased with clear-cut trend. Magnitude of color difference
between initial sample and sample at particular storage interval is
indicated by total colour difference (Pathare et al., 2013). It was
observed that color difference was distinct during initial days of
storage i.e. upto 15 days and it turned into very distinct during
whole storage period. Similar trend of color values was obtained by
Sharma et al. (2020) in gamma irradiated onion bulbs.
Increase in quantity of oxidative radicals generated after expo-
sure of food to gamma radiation mainly led to decrease in ascorbic
acid content (Lester and Hallman, 2010; Sharma et al., 2020). In-
crease in sensitivity of ascorbic acid with increase in irradiation
dose levels proved greater sensitivity of Vitamin C toward
irradiation as observed by Fellows (2017). It might be because of
higher metabolism of ascorbic acid and carbohydrates bio-
synthesizing or its oxidation to dehydroascorbic acid (Rezaee et al.,
2013; Sharma et al., 2020). Therefore, results also showed that
gamma dose less than 0.06 kGy preserved considerable ascorbic
acid content which further reduced @ dose levels of 0.12 kGy and
0.2 kGy.
Garlic's pungent flavor is mainly attributed to sulphur-containing
non-volatile amino acids (thiosulfinates), among which alliin (pre-
cursor of allicin) or S-allyl-cysteine sulfoxide (ACSO) comprises the
most predominant garlic flavor precursors (Block et al., 1993;
Horní
ckov
a et al., 2010., Martins et al., 2016). It was suggested that
Fig. 6. Effect of irradiation doses on total color difference of garlic bulbs during storage. (For interpretation of the references to color in this figure legend, the reader is referred to
the Web version of this article.)
Fig. 7. Effect of irradiation doses on ascorbic acid of (mg100 g1
) garlic bulbs during storage.
P. Sharma et al. / Journal of Stored Products Research 87 (2020) 101629 9

pungency in garlic was mainly influenced by the genotype, har-
vesting stage and application of Sulphur nutrition (Martins et al.,
2016; Sharma et al., 2020). Ichikawa et al. (2006), suggested that
conversion of g-glutamyl peptides into sulfoxides, such as allin and
isoallin during ambient storage was observed which proved the
higher concentration of allicin after 195 days. However, isoalliin is
further converted into cycloalliin, thus affecting the quality of the
final product. Similar decreasing and increasing behavior of allicin
concentration bulbs of garlic was observed by Fei et al. (2015) during
ambient storage Fei et al. (2015) showed that maximum organo-
sulphur compounds (allicin) in garlic bulbs were obtained between 6
and 8 weeks of the storage. However, Veríssimo et al. (2010) showed
that allicin content in the garlic decreased over the storage period. A
study conducted by Bandyopodhyay and Gholap (1973) showed that
irradiation dose of 0.5 kGy had no effects on the pungent flavour
substances of the garlic. However, a study conducted by Kwon et al.
(1989) showed that gamma radiation dose upto 0.1 kGy had little
influence on the thiosulphate content of the stored garlic bulbs.
5. Conclusions
The results concluded that irradiation technology using gamma
rays was found to be an effective novel non-thermal post-harvest
method for storage life enhancement and sprout inhibition of bulb
crops. It was found that post-harvest storage losses (PLW, rotting
and sprouting) in garlic bulbs were higher in non-irradiated and
bulbs irradiated @ 0.01 kGy and 0.2 kGy. The physico-chemical at-
tributes viz. firmness, total soluble solids, color, ascorbic acid and
allicin content were found to be better in bulbs treated with gamma
dose of 0.12 kGy on 195th day of storage. Therefore, it is concluded
that garlic bulbs irradiated @ 0.12 kGy of gamma radiation resulted
in minimum post-harvest losses along with better quality attri-
butes for 4 months under ambient temperature.
Author's contribution
Pallavi Sharma is responsible for Data curation, Formal analysis,
Investigation, Validation, Writing original draft. SR Sharma is
responsible for Conceptualization, Methodology, Resources, Soft-
ware, Supervision, Writing review editing. RK Dhall is responsible
for Resources, Data curation, Validation, Writing review editing. TC
Mittal and Surekha Bhatia is responsible for Resources, Writing re-
view editing.
Declaration of competing interest
The authors declare that they have no known competing
financial interests or personal relationships that could have
appeared to influence the work reported in this paper.
Acknowledgements
The corresponding author gratefully acknowledges the Depart-
ment of Science and Technology (DST), New Delhi, Govt of India, for
awarding the DST-INSPIRE fellowship (IF170182) for scientific
research.
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