Upload
dipika
View
213
Download
1
Embed Size (px)
Citation preview
ORIGINAL PAPER
A comparative study on the effect of packaging materialand storage environment on shelf life of fresh bell-pepper
Nihar R. Sahoo • Lalit M. Bal • Uma S. Pal •
Dipika Sahoo
Received: 21 January 2014 / Accepted: 30 March 2014
� Springer Science+Business Media New York 2014
Abstract The effect of packaging materials [low density
polyethylene (LDPE), polypropylene (PP)] and storage
environment [modified atmospheric packaging (MAP)] on
shelf life enhancement of bell pepper in terms of quality
attributes such as physiological weight loss, ascorbic acid,
texture, surface colour and subjective quality analysis have
been studied at ambient and refrigerated condition. Dif-
ferent packaging techniques used for the experiment were
MAP with LDPE, MAP with PP, MAP in perforated LDPE
films, MAP in perforated PP films, shrink packaging with
bi-axially oriented PP (BOPP) film and vacuum packaging
with PP film. The in-pack bell pepper created a suitable
headspace environment with low O2 and high CO2 con-
centrations, which resulted in a better retention of freshness
of the vegetables and its marketability. Shrink packaging
with BOPP film could not yield better result under ambient
storage because of high water vapor transmission rate of
the film and consequently loss of turgidity of the vegeta-
bles. Among different packaging techniques and storage
conditions, MAP with PP film in refrigerated condition was
found to be the best followed by vacuum pack with PP film
in refrigerated condition and could be used to store for
20 days for bell pepper with maintenance of texture, col-
our, ascorbic acid and marketability. It is also inferred that
under ambient conditions, bell pepper could be stored for
4 days using ventilated LDPE and PP as MAP storage.
Further studies are needed to evaluate the sensory aspects,
as well as to microbiological evaluation to characterize the
fresh bell pepper during storage.
Keywords Bell pepper � Storage � Modified atmospheric
packaging � Physiological loss in weight
Introduction
Pepper is an important cash crop in India and the world’s
second most important solanaceous vegetable after tomato,
also known as bell pepper and locally known as simla
mirch [1]. Though it is low in saturated fat, cholesterol, and
sodium but it is rich in dietary fiber, Vitamin A, Vitamin C,
Potassium, Manganese, Thiamin, Riboflavin, Niacin and
Magnesium makes it nutritionally rich for maintaining
optimum health and weight loss programme [2]. However,
it has high rate of respiration and thus a shorter shelf-life at
room temperature due to various physiological factors
regulated by genetic mechanisms high susceptibility to
fungal diseases [3]. The major changes taking place during
its senescence include loss in weight due to moisture loss,
degradation of chlorophyll thus change in colour, loss of
turgidity and change in texture, loss of nutritional value
and reduction in marketability.
In recent days, there have been reports of different
methods of polymeric film packaging of fresh produces to
increase the shelf life. Polymeric film packaging in com-
bination with cool storage has been successful in delaying
N. R. Sahoo � U. S. Pal
Department of Agricultural Processing and Food Engineering,
Orissa University of Agriculture and Technology,
Bhubaneswar 751003, Odisha, India
L. M. Bal (&)
Post Harvest Process and Food Engineering, College of
Agriculture, Jawaharlal Nehru Agricultural University,
Tikamgarh 472001, Madhya Pradesh, India
e-mail: [email protected]
D. Sahoo
Department of Horticulture, College of Agriculture,
Bhawanipatna, Orissa University of Agriculture and
Technology, Bhubaneswar 751003, Odisha, India
123
Food Measure
DOI 10.1007/s11694-014-9177-4
senescence, maintenance of physico-chemical constituents
and extending shelf life. However, the selection of an
appropriate packaging film and packaging techniques are
the important criteria for its storage life. Improper film
selection and packaging technique can lead to loss of
quality in a very short period [4].
Generally for highly respiring materials like vegetables,
micro-perforated films having high gas transmission rates
for O2 and CO2 can be used to extend their shelf life [5].
But the micro-perforated films are costly. On the other
hand, application of non-perforated continuous films could
create anaerobic atmosphere inside the package headspace
in a short period thus accelerating quality deterioration.
Taking these factors into account, the application of
ordinary readily available polymeric films with appropriate
perforations can be explored. Therefore, objective of the
present study was on the effect of packaging material and
storage environment on shelf life of fresh bell-pepper.
Materials and methods
Raw material and sample preparation
Fresh green mature bell pepper was procured after har-
vesting manually from the research farm, Orissa University
of Agriculture and Technology, Bhubaneswar. Immedi-
ately after harvest, samples were transported to the
experimental site in plastic crates. The vegetables were
washed thoroughly with tap water to remove field heat and
adhering soil particles on the surface. The samples were
sorted for uniform size and colour, and packed separately,
approximately about 500 g per each pack.
Different packaging techniques used for the experiments
were modified atmospheric packaging (MAP) with low
density polyethylene (LDPE), MAP with polypropylene
(PP), MAP in perforated LDPE films, MAP in perforated
PP films, shrink packaging with bi-axially oriented PP
(BOPP) film and vacuum packaging with PP film. The
properties of these films used for packaging experiments
have been given in Table 1. Bag area of 10 cm 9 10 cm
was provided for each pack and perforations provided in
the LDPE and PP films were five holes of 0.3 mm diameter
in each side of the films. Sample packs were stored at
ambient (23–35 �C, 35–75 % RH) and chilled refrigerated
(4–6 �C, 45 % RH) conditions separately. The control
samples of 500 g each were kept unsealed under similar
environmental conditions of temperature and RH sepa-
rately. Three packages each from MAP storage treatments
of LDPE, ventilated LDPE, PP and ventilated PP were
taken out at 8 h storage interval for analysis of in-pack
head space concentration of O2 and CO2. The qualitative
analysis of the stored bell pepper packages (in triplicate)
was carried out in 2 days interval.
Physico-chemical analysis
Headspace gas evaluation
Changes in CO2 and O2 concentration of the headspaces of
the fresh-cut bell pepper packages during storage were
monitored with a check point O2/CO2 instrument (PBI
Dansensor, Denmark) at prespecified time [6]. The instru-
ment has ceramic solid state sensor for recording O2 and
infrared double wavelength sensor for recording CO2 by
means of a built-in pump and measuring gas was taken
from the suction probe or via enclosed needle. The accu-
racy of 0.1 % for O2 and 2 % for CO2 were in full range.
The calibration for the instrument was done with O2 and
CO2 air percentages. Parameters were expressed as DCO2
and DO2 percentage referred to initial values.
Physiological loss in weight (PLW)
The weight of each bell pepper package sample was
determined by weighing on the day after each period of
storage using a laboratory weighing balance having
0.0001 g accuracy. The PLW was calculated and expressed
in percentage based on initial weight of the samples. The
cumulative PLW was analyzed with respect to different
treatments.
Ascorbic acid
Ascorbic acid content of bell pepper sample was estimated
using standard procedure of titration method suggested by
Ranganna [7] based on the reduction of 2, 6-dichlorophenol
indophenol dye by ascorbic acid and can be expressed as
mg/100 g fresh weight.
Texture analysis
The texture of the stored bell peppers at regular intervals
were analysed by measuring the peak force from the
puncture test with a 2 mm probe using 50 kg load cell with
the help of a texture analyzer (TA-XT Plus, Stable Mi-
crosystems Ltd.).
Marketable quality evaluation
For assessing the marketable quality of the vegetable,
descriptive quality attributes were determined subjectively
by observing the level of visible mould growth, decay,
shriveling, smoothness and shine of the produce. The
N. R. Sahoo et al.
123
number of marketable vegetable (C80 %) was used as a
measure to calculate the percentage of marketable vege-
table during storage. Performance of the chamber was
evaluated in terms of shelf-life in number of days with
marketability C80 % [8, 9]. The fruits and vegetables were
stored in plastic crates inside the chamber and their shelf-
life was determined on the basis of an index of 20 %
spoilage or unmarketability.
Statistical analyses
The results obtained were subjected to analysis of variance
using SPSS 10.0 software. The means obtained from each
set were compared using the Duncan’s multiple range test
based on a complete randomized design (at 0.05 confidence
level).
Results and discussion
Headspace gases
The in-pack gaseous of O2 and CO2 concentrations for bell
pepper stored in different packages under ambient and
refrigerated condition are shown in Figs. 1 and 2, respec-
tively. The in-pack atmosphere of bell pepper attained
steady state levels of 9.4, 9.8, 9.0 and 9.2 % O2 and 3.3,
3.6, 3.9 and 4.1 % CO2 concentration level in-packs of
LDPE, ventilated LDPE, PP and ventilated PP, respectively
after 32 h of storage under refrigerated condition. Mano-
lopoulou et al. [10] made similar observation with MAP
storage of green bell pepper in polymeric films of LDPE-
60, MDPE-30 and PVC. In ambient storage of vegetables
in vacuum pack and shrink pack, initially there was no
head space gas, however after 4 and 8 days of storage there
was little gas accumulation and the samples spoiled
thereafter. So head space gas analysis was not done for
those samples. In case of refrigerated storage of vegetables,
vacuum was maintained in both vacuum pack and shrink
pack till 20 days of storage, so no head space gas analysis
was done.
Physiological loss in weight (PLW)
The PLW% in case of bell pepper storage was maximum in
the ambient control which was 21.60 (±2.57) % (Fig. 3)
after 8th day followed by 12.57 (±2.34) % (Fig. 4) in
refrigerated control at the end of 20th day of storage.
Table 1 Properties of films used for packaging of bell pepper
Thickness
(l)
Density
(g/cm3)
Oxygen transmission
rate (cm3/m2/24 h)
Water vapor
transmission rate (g/
m2/24 h)
Tensile
strength (kg/
cm2)
Elongation
(%)
Refractive
index at
200 �C
Water
absorption
rate (%)
LDPE
film
25 0.910 6,400 04.50 165 600 – 0.9
PP
film
45 1.054 3,000 07.75 400 300 1.58 –
BOPP
film
23 0.901 4,500 18.00 300 – – –
Fig. 1 Changes in head space concentrations of O2 and CO2 for bell
pepper samples stored under ambient conditionFig. 2 Changes in head space concentrations of O2 and CO2 for bell
pepper samples stored under refrigerated condition
Study on the effect of packaging material and storage environment
123
Ambient shrink pack sample showed a PLW% of 4.53
(±0.56) after eighth day and refrigerated shrink pack
sample showed PLW% of 1.78 (±0.34), which were
significantly higher to all other types of packaging condi-
tions. PP film without perforation under refrigerated con-
dition could check the PLW% to 0.49 (±0.07) %, whereas
with perforation it was only 0.59 (±0.08) %. Vanndy et al.
[11] also found similar result in their study of MAP of fresh
chilli.
Ascorbic acid
The ascorbic acid content decreased with storage period
under all the packaging treatments and storage environ-
ments. But the decrease in ascorbic acid content was sig-
nificantly higher under ambient conditions (Fig. 5) as
compared to the refrigerated storage condition (Fig. 6). In
ambient control storage, the decrease in ascorbic acid was
observed to be maximum (9.6 %) from an initial value of
158.42 (±1.24)–143.26 (±1.57) mg/100 g at the end of 8th
day whereas in refrigerated control samples the decrease
(11.5 %) was to 140.20 (±1.59) mg/100 g at the end of 20th
days of storage. The retention of ascorbic acid was highest
with the vacuum packaging condition maintaining 155.03
(±2.57) mg/100 g followed by PP with ventilation main-
taining 153.66 (±2.37) mg/100 g at the end of 20 days
among all the packaging types under refrigerated storage
condition. This could be due to the fact that low temperature
retarded the ageing through reduced respiration rate and
other undesirable metabolic changes. High temperature is
known to increase enzymatic catalysis and leads to a
chemical and bio-chemical breakdown in vegetables [12].
Texture analysis
A decrease in the peak force required to puncture the bell
pepper samples was observed in all the packaging types
both under ambient and refrigerated storage conditions.
The decrease in peak force was from 1.32 (±0.34) to 1.19
Fig. 3 Changes in PLW% of bell pepper under ambient storage
Fig. 4 Changes in PLW% of bell pepper under refrigerated storage
Fig. 5 Change in ascorbic acid content of bell pepper under ambient
storage
Fig. 6 Change in ascorbic acid content of bell pepper under
refrigerated storage
N. R. Sahoo et al.
123
(±0.62) kgf in PP with ventilation in refrigerated storage,
whereas, from 1.32 (±0.34) to 0.80 (±0.37) kgf in samples
stored in LDPE with ventilation under ambient storage
after 8 days. The control sample showed a decrease of peak
force from 1.32 (±0.34) to 0.54 (±0.35) kgf at the end of
20th day under refrigerated storage. The decrease in
puncture force was gradual in all other samples stored in
different packaging types under refrigerated condition.
Samples stored in vacuum pack condition maintained the
best texture among all the refrigerated stored samples with
a value of 1.03 (±0.23) kgf at the 20th day (Table 2).
Marketable quality
Marketability quality of fruits and vegetables was subjec-
tively assessed by observing the level of visible mould
growth, rotting, shriveling or discolouring shown in
Figs. 7, 8, 9, 10, and 11. The percentage marketable bell
pepper subjected to storage in different packaging materi-
als and storage environment are shown in Table 3. The
highest marketability of bell pepper was obtained in PP
with perforations under refrigerated storage. The percent-
age marketability were found to be 86.53, 61.30, 78.44 and
62.35 % after 20 days of storage in PP with perforations,
LDPE with perforation, vacuum pack and shrink pack
samples, respectively under refrigerated storage. In ambi-
ent storage of bell pepper, the percentage marketability
started decreasing since fourth day onwards and after
8 days of ambient storage all the packaging type showed
almost 2/3 of vegetables unmarketable. Ponnachanna et al.
[13] found similar result with storage studies of tomato and
bell pepper using eco-friendly films.
The good storage performance of vegetables in terms of
marketability in PP with perforation in refrigerated storage
Table 2 Effect of packaging
material and storage
environment on texture of bell
pepper
Figures in parenthesis are
standard deviation. Values in
the same rows followed by
different superscript letters (a–f)
are significant different
(p \ 0.05)
Packaging materials Texture ðkgf)Storage period ðdays)
0 4 8 12 16 20
Ambient
Control 1.32a (0.34) 0.66b (0.13) 0.43c (0.09) – – –
LDPE 1.32a (0.34) 0.87b (0.15) 0.61c (0.15) – – –
LDPE with pin
holes
1.32a (0.34) 0.94b (0.37) 0.75c (0.31) – – –
Polypropylene 1.32a (0.34) 0.89b (0.23) 0.74c (0.29) – – –
PP with pin holes 1.32a (0.34) 0.97b (0.41) 0.80bc (0.37) – – –
Vacuum pack 1.32a (0.34) 0.95b (0.33) 0.87c (0.19) – – –
Shrink pack 1.32a (0.34) 0.88b (0.39) 0.72c (0.41) – – –
Refrigerated
Control 1.32a (0.34) 0.97b (0.31) 0.83cd (0.51) 0.77d
(0.56)
0.61e
(0.47)
0.54f
(0.35)
LDPE 1.32a (0.34) 1.26b (0.73) 1.22b (0.37) 1.15bc
(0.33)
0.92c
(0.24)
0.87de
(0.44)
LDPE with pin
holes
1.32a (0.34) 1.19b (0.52) 1.07bc (0.29) 0.98cd
(0.38)
0.89e
(0.43)
0.84e
(0.36)
Polypropylene 1.32a (0.34) 1.21b (0.62) 1.14bc (0.34) 1.06d
(0.24)
0.96de
(0.37)
0.91e
(0.52)
PP with pin holes 1.32a (0.34) 1.26bc (0.49) 1.19d (0.62) 1.12de
(0.19)
1.09e
(0.52)
1.01ef
(0.49)
Vacuum pack 1.32a (0.34) 1.30a (0.38) 1.25ab (0.27) 1.19bc
(0.41)
1.11c
(0.34)
1.03de
(0.27)
Shrink pack 1.32a (0.34) 1.29a (0.51) 1.20bc (0.35) 1.16c
(0.63)
1.04de
(0.37)
0.98f
(0.22)
Fig. 7 Samples in LDPE film with hole after 8 days
Study on the effect of packaging material and storage environment
123
could be attributed to the fact that low temperature storage
along with modified atmosphere retarded the senescence.
No significant variation could be observed among pack-
aging material under ambient condition.
Conclusions
The in-pack bell pepper created a suitable headspace
environment with low O2 and high CO2 concentrations,
which resulted in a better retention of freshness of the
vegetables and its marketability. Shrink packaging with
BOPP film could not yield better result under both ambient
and refrigerated storage because of high water vapor
transmission rate of the film and consequently loss of tur-
gidity of the vegetables. Among different packaging tech-
niques and storage conditions, MAP with perforated PP
film in refrigerated condition was found to be the best
followed by vacuum pack with PP film in refrigerated
condition. It could be inferred that perforated PP film
packages could be used to store bell pepper for 20 days
under MAP refrigerated condition with maintenance of
texture, colour, ascorbic acid and marketability in com-
parison to 4 days in ambient condition.
Fig. 8 Samples in PP film without hole after 8 days
Fig. 9 Samples in PP film with hole after 20 days
Fig. 10 Samples in vacuum pack in PP film without hole after
20 days
Fig. 11 Samples in control after 8 days
Table 3 Effect of packaging material and storage environment on
percent marketability of bell pepper
Packaging materials Marketability (%)Storage period ðdays)
0 4 8 12 16 20
Ambient
Control 100 72.31 21.50 – – –
LDPE 100 81.25 32.93 – – –
LDPE with pin holes 100 85.33 45.17 – – –
Polypropylene 100 83.72 48.36 – – –
PP with pin holes 100 86.91 50.03 – – –
Vacuum pack 100 85.17 47.62 – – –
Shrink pack 100 79.39 38.11 – – –
Refrigerated
Control 100 75.06 53.41 42.95 30.33 20.50
LDPE 100 81.44 76.30 71.03 66.22 52.05
LDPE with pin holes 100 100 100 93.34 78.52 61.30
Polypropylene 100 85.50 78.93 76.38 68.19 55.72
PP with pin holes 100 100 100 96.17 90.09 86.53
Vacuum pack 100 100 100 94.34 82.93 78.44
Shrink pack 100 92.38 85.78 71.06 68.43 62.35
N. R. Sahoo et al.
123
References
1. B. Choudhary, Vegetables, 1st edn. (National Book Trust, New
Delhi, 1967), p. 70
2. A.P. Chaudhary, B.K. Kumbhar, B.P.N. Singh, M. Narain, Indian
Food Ind. 12, 20–27 (1993)
3. R.E. Hardenburg, A. Watada, C.Y. Wang, Agriculture Handbook
No. 66 (US Department of Agriculture, Washington, DC, 1990),
pp. 23–25
4. D.R. Rai, S. Paul, J. Food Sci. Technol. 44, 10–15 (2007)
5. S. Kartal, M.S. Aday, C. Caner, Postharvest Biol. Technol. 71,
32–40 (2012)
6. B. Tirkey, U.S. Pal, L.M. Bal, N.R. Sahoo, C.K. Bakhara, M.K.
Panda, Food Packag. Shelf Life (2014). doi:10.1016/j.fpsl.2014.
02.002
7. S. Ranganna, Handbook of analysis and quality control for fruit
and vegetable products, 2nd edn. (Tata McGraw-Hill Publishing
Company Limited, New Delhi, 2004)
8. M. Mohammed, L.A. Wilson, P.L. Gomes, J. Food Qual. 22,
167–182 (1999)
9. A. Tefera, T. Seyoum, K. Woldetsadik, Biosyst. Eng. 96,
201–212 (2007)
10. H. Manolopoulou, G. Xanthopoulos, N. Douros, G. Lambrinos,
Biosyst. Eng. 106(4), 535–543 (2010)
11. M. Vanndy, T. Chanthasombath, C.D. Thanh, B. Buntong, A.
Acedo, K. Weinberger, in ISHS Acta Horticulturae 804: Europe-
Asia Symposium on Quality Management in Postharvest Sys-
tems—Eurasia, 2007
12. M. Oke, J.K. Jacob, G. Paliyath, in Food Biochemistry and Food
Processing, 2nd edn. ed. by B.K. Simpson (Wiley–Blackwell,
Oxford, 2012)
13. C.S. Ponnachanna, V.H.P. Keelara, S.S. Nuggenahalli, R. Ra-
masamy, N.T. Rudrapatnam, J. Sci. Food Agric. 86(8),
1216–1224 (2006)
Study on the effect of packaging material and storage environment
123