Influence of cutting size and packaging materials on the quality of fresh-cut winter squash (var. Ajijimang)

doi:10.4236/as.2013.49064

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Vol.4, No.9, 477-482 (2013) Agricultural Sciences

http://dx.doi.org/10.4236/as.2013.49064

Influence of cutting size and packaging materials on

the quality of fresh-cut winter squash (var. Ajijimang)

Alexander Joel G. Gibe1, Ji Gang Kim2*

1Philippine Center for Postharvest Development and Mechanization, Munoz, Philippines

2National Institute of Horticultural and Herbal Science, Rural Development Administration, Suwon, Korea;

*Corresponding Author: [email protected]

Received 9 June 2013; revised 10 July 2013; accepted 15 August 2013

tribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is prop-

erly cited.

ABSTRACT

Winter squash (var. Ajijimang) washed in 100

mg·L−1 chlorine water and cut into 4 and 8 parts

was packed in different packaging materials, 35

µm micro-perforated P-Plus (MPP), 50 µm poly-

ethylene (PE), 80 µm nylon/PE (Ny/PE), and 90

µm PE films separately. Fresh-cut samples were

then stored at 10˚C for up to 17 days. The 35 µm

MPP having a high oxygen transmission rate

(OTR) has the most stable gas exchange ratio

while the 80 µm Ny/PE was the most unstable.

Firmness of the mesocarp remained acceptable

until the end of storage regardless of the cutting

size. Soluble solids content (SSC) remained

stable and even slightly increased to a certain

extent within 6 days. An increase in pH after

10-day storage suggested the activity of micro-

organisms within the packaging films. Strong

off-odor was detected in samples packaged in

80 µm Ny/PE film after 13 days of storage. Mold

was observed in all 1/4 cut samples on day 13

except the sample packaged with 80 µm Ny/PE

film. However, no mold was found in all 1/8 cut

samples except 35 µm MPP film on day 13. Se-

vere mold invasion was apparent on the onset of

the 17-day storage in 35 µm MPP film and 50 µm

PE film. Samples cut into 8 parts and packed in

80 µm Ny/PE and 90 µm PE films had less mold

incidence compared with other two packaging

films. Fresh-cut winter squash packaged in 90

µm PE film maintained quality with shelf-life of

10 days at 10˚C. Winter squash as fresh-cut

commodity, with the right packaging material

has the potential for longer period of storage in

retail stores.

Keywords: Fresh-Cut; Packaging Films; Shelf-Life;

Storage; Winter Squash

1. INTRODUCTION

Fresh-cut commodities are gaining popularity in Korea

for the last decade in response to an increased consumer

demand for convenient food. However, fresh-cut produce

has limited shelf-life due to rapid quality deterioration.

Quality of fresh-cut produce depends mainly on the qual-

ity of the intact product and its maintenance between

harvest and preparation of the fresh-cut products, proc-

essing method, and subsequent handling conditions [1].

Korean fresh-cut processors recognize the importance of

postharvest handling of raw materials. Processors are

aware that raw materials affect shelf-life of fresh-cut

produce [2].

In winter squash (Cucurbita maxima D.), it is vital to

wash newly harvested fruits with 200 ppm of NaOCl to

control growth of spoilage fungi before storage or proc-

essing [3]. The atmosphere surrounding fresh-cut proc-

essed vegetables likewise is extremely important to ex-

tend shelf-life. One of the most influential factors on its

composition is the permeability of the film used for

packaging [4] and the interaction between film oxygen

transmission rates (OTR) and initial headspace O2 [5].

Polyethylene (PE) is one of the most commonly used

materials in packaging. Polypropylene (PP) either un-

perforated or micro-perforated is likewise gaining popu-

larity. These films in different thickness possess a range

of gas transmission rates. Fresh-cut products that nor-

mally have elevated respiration rate require films with

high gas transmission capabilities. Even within the

package, fresh-cut vegetables are bound to deteriorate.

The main spoilage mechanisms influencing processed

products include oxidation, water loss and the activity of

A. J. G. Gibe, J. G. Kim / Agricultural Sciences 4 (2013) 477-482

478

microorganisms. Reducing the respiration rate and inhib-

iting agents of spoilage with the right packaging films

having appropriate gas transmission rates and right tem-

perature at storage would result in longer shelf-life of

packed commodity.

Green rind winter squashes commonly known as but-

tercup is a popular variety that has an appealing yellow

orange flesh with high soluble solids content (SSC) of 13

to 17% [6,7]. Cultivar Ajijimang is another green rind

winter squash more appealing for its higher SSC of 17 to

19% [8]. Ajijimang is a potential variety as fresh-cut

winter squash that may be used for ready-to-cook com-

modity. Oftentimes, the fruit is cut in halves or in quarter

covered with a 15 μm polyvinyl chloride (PVC) wrap

and displayed at 15˚C to 20˚C shelves in supermarkets in

Korea. The cut squash fruits often last for 2 to 3 days.

Optimum modified atmosphere (MA) packaging is effec-

tive in prolonging the shelf-life of fresh-cut produce by

matching film permeability for O2 and CO2 to the respi-

ration rate of the packaged commodity. The respiration

rate of fresh-cut produce is influenced by storage tem-

perature, cut size, etc. Little information exists on opti-

mum packaging film for different sized fresh-cut winter

squash. To date, vacuum packaging with Ny/PE film and

PVC wrap are utilized for covering cut winter squash. In

the present experiment, different films were assessed as

packaging material for fresh-cut winter squash (var. Aji-

jimang) prepared in different cuts.

2. MATERIALS AND METHODS

2.1. Materials, Fresh-Cut Processing, and

Packaging

Winter squash (Cucurbita maxima D., cv. Ajijimang)

grown in a plastic house in Suwon was harvested 45 days

after flowering. The fruits were conditioned for a month

for further maturation at room temperature (25˚C ± 2˚C).

The squash material was subjected to further storage of

three months at 12˚C. The average weight of intact win-

ter squash was 1.8 kg.

Three months stored Ajijimang were washed with 100

ppm of sodium hypochlorite (NaOCl) prior to cutting.

The squash was cut into quarter (1/4) and eight parts (1/8)

with seeds removed and washed with cold sterile water

to remove cellular exudates released during cutting of

winter squash. Samples were air dried for a few minutes

to remove surface water. After surface drying, fresh-cut

squash were packaged in 35 μm micro-perforated P-Plus

(MPP), 80 µm Nylon/PE (Ny/PE), 50 µm PE, or 90 µm

PE films. Fresh-cut squash samples in packages (20  25

cm) were then stored at 10˚C for up to 17 days.

Oxygen transmission rates (OTR) of 50 and 90 µm PE

films (Samkyoung Chemistry Ltd., Korea) were 1850

mL· m−2·d−1 and <1300 mL·m−2·d−1 at 10˚C [9], respec-

tively. 35 µm MPP film (Amcor, UK) with an OTR of

11,648 mL·m−2·d−1 at 10˚C and 80 µm NY/PE film (Da-

san Polybag, Korea) with an OTR of about <100

mL· m−2·d−1 at 25˚C [10] were also used to pack different

cutting sizes of winter squash.

2.2. Gas Composition Analyses

Oxygen (O2) level and accumulation of carbon dioxide

(CO2) within the package of different films containing

fresh-cut winter squash were monitored in every sam-

pling occasion. Gases were measured using a gas moni-

toring devise (PBI-Dansensor CheckMate II, Denmark)

by placing the needle directly into the packages.

2.3. Texture Measurements

In every period of analysis, samples of each cut in

triplicate representing a treatment were sliced twice

horizontally making a 5 cm-thick cut in the middle. The

top slice represented the stalk side while the bottom slice

represented the underside of the fruit where the calyx is

located. The middle slices were analyzed for firmness

while top and bottom parts were analyzed for soluble

solids content and change in pH. In each sampling occa-

sion, cut samples from the middle section of the fruit were

analyzed for firmness by using a texture analyzer (Model

TA-XT2-5, Stable Microsystems, UK). Two spots per

replicate on flat surface of sliced samples were pricked

with a cylindrical probe of 3 mm in diameter mounted on

a drill stand at 3 mm per second speed and deformation

distance of 8 mm.

2.4. Soluble Solids Content and pH

Juice samples used for soluble solids content (SSC)

and pH measurements were obtained by grating of

peeled samples and squeezing of the squash samples

from each replicate with a hand juicer. Samples were

then filtered through two layers of cotton gauze. Soluble

solids content and pH of the juice were measured at

room temperature with a digital refractometer (Model

PAL-1, Atago Co., Japan) and a pH meter (Model Titro-

Line Easy, Schott, UK), respectively.

2.5. Mold Infection and Off-Odor

Development

Incidence of mold infection was monitored throughout

the storage period. The incidence rate was calculated by

the weight of all mold infected pieces in each package,

divided by the total fresh weight of the sample and mul-

tiplied by 100 to obtain percentage. Off-odor was evalu-

ated immediately after opening the packages and scored

on a five-point scale where 0 = none; 1 = slight; 2 =

moderate; 3 = strong; and 4 = severe [5]; a score of 3 or

A. J. G. Gibe, J. G. Kim / Agricultural Sciences 4 (2013) 477-482 479

above was considered unacceptable.

3. RESULTS AND DISCUSSION

3.1. Gas Composition

Any vegetables when processed or cut will have in-

creased metabolic activity as a result of an increased sur-

face area exposed to the atmosphere. The respiration rate

increases as the cutting allows oxygen to diffuse into the

interior cells more rapidly [11]. Winter squash in two

different cuts were packaged in four different films with

different OTRs. Levels of O2 and CO2 within the pack-

age as the squash were stored at 10˚C are presented in

Figure 1. Fresh-cut winter squash packaged in 35 µm

MPP film has the most stable gas concentrations/ex-

change within the package for the entire storage period

of 17 days. This type of film has a high OTR of 11,648

mL· m−2·d−1 at 10˚C [9] and therefore allows higher gas

exchange. On the other hand, O2 concentration in pack-

age prepared with 80 µm Ny/PE film decreased rapidly

to zero from 18% while CO2 increased tremendously

within three days. This film has a very low OTR of about

<100 mL·m−2·d−1 at 25˚C [10] and level of CO2 keeps on

accumulating as storage progressed which resulted in

ballooning of the package. CO2 levels within the package

even reached 60 % in 10 days. Both 50 and 90 µm PE

films exhibited better gas exchange in the presence of

fresh-cut winter squash. Although O2 levels in those

films reached anaerobic conditions from 3 days until the

end of the storage period, ballooning was not observed

Figure 1. Levels of O

2 and CO2 concentration in fresh-cut

winter squash packaged in different films (µm) and stored at

10˚C for 17 days. Each symbol is the mean of three replicate

measurements; vertical lines represent SE. (●) 50 µm PE, (○)

90 µm PE, (▲) 35 µm MPP, (∆) 80 µm Ny/PE.

neither in the two PE films tested. However, the level of

CO2 in 50 µm PE film was lower than 90 µm PE film

because CO2 diffusion in 50 µm PE film was faster due

to a higher OTR compared to 90 µm PE film [9].

3.2. Firmness

Mesocarp of fresh-cut Ajijimang was highly firm ini-

tially at 36.9 N when preconditioned one month after

harvest. Firmness of fresh-cut winter squash was gener-

ally maintained for 10 days regardless of the cut and

packaging film (Figure 2). Slicing plant tissues generally

results in loss of firmness causing direct water loss due

to cell leakage [12]. As minimally processed vegetables

are stored, loss in turgor pressure and textural breakdown

due to enzymatic hydrolysis of cell compounds becomes

apparent [13]. The mechanism of physical spoilage in

fresh-cut winter squash is unique. The breakdown of

tissues may have been very slow due to its high starch

content. The result only suggests that firmness is not go-

ing to be a problem in winter squash as a fresh-cut com-

modity. More so, with the right packaging film and stor-

age temperature, other quality attributes will likewise be

preserved.

3.3. Soluble Solid Content and pH

Winter squashes are not only known for its excellent

nutritive value and eating quality, its seeds and flesh

likewise contain high level of Vitamin E and carotenoids,

respectively as anti-oxidants [14,15]. In the same way,

winter squash which has high sugar content is attractive.

It is therefore important that give attention to SSC as a

quality attribute of fresh-cut winter squash. Levels of

SSC in fresh-cut Ajijimang increased slightly from

17.2% to 18.6% and were maintained within 10 days of

storage (Figure 3(a)). The same trend was true with 80

µm Ny/PE film (data is not shown). Fresh-cut winter

(a) (b)

Figure 2. Firmness of fresh-cut winter squash packaged in

different films (µm) and stored at 10˚C for 17 days. Each sym-

bol is the mean of three replicate measurements; vertical lines

represent SE. (●) 50 µm PE, (○) 90 µm PE, (▲) 35 µm MPP,

(∆) 80 µm Ny/PE.

A. J. G. Gibe, J. G. Kim / Agricultural Sciences 4 (2013) 477-482

480

(a) (b)

Figure 3. Levels of soluble solid content (SSC) and pH in

fresh-cut winter squash packaged in two different films (µm)

and stored at 10˚C for 17 days. Each symbol is the mean of

three replicate measurements; vertical lines represent SE. (●)

1/4 Cut + 50 µm PE, (○) 1/4 Cut + 90 µm PE, (▲) 1/8 Cut + 50

µm PE, (∆)1/8 Cut + 80 µm PE.

squash from Ajijimang, in this case, continued to ripen

within the specified period of time. The same findings

were observed by Roura et al. [16] in diced squash (C.

moschata) packed and covered with 15 µm PE wrap

where SSC and sugar/titratable acidity ratios increased

during storage at 10˚C ± 2˚C. Soluble solids content in

fresh-cut winter squashes although initially very high

were at a plateau and started to decline after 10 days.

These findings suggest the importance of selecting pro-

per maturity and preconditioning details of squash varie-

ties as fresh-cut vegetable. It appears that packaging

films used facilitated maintenance in quality in terms of

increasing or maintaining SSC in storage. However, sur-

face drying was noticeable early in storage even within 6

days in 35 µm MPP film package. The RH during stor-

age period ranged from 45% to 60%. Increasing the RH

would improve dryness of fresh-cut surface.

It is worth interesting to note that pH of fresh-cut win-

ter squash increased slowly during storage. Increase in

pH became prominent after 10 days of storage (Figure

3(b)) signifying higher microbial activity which is con-

sistent with the visible growth of fungi on day 13 for

winter squash packed in 50 µm PE film (Figure 5) and

possible bacterial accumulation or other fermenting or-

ganisms in squash packed in 90 µm PE film.

3.4. Spoilage and Off-Odor

The main causes of deterioration mechanisms influ-

encing processed products include oxidation, water loss

and the activity of microorganisms. All three mecha-

nisms were observed in fresh-cut winter squash depend-

ing on the films used. 35 µm MPP film is capable of ex-

changing more balanced gases however surface of

fresh-cut winter squash dries up within the package. Ap-

pearance of mold spots in fresh-cut squash packaged in

35 µm MPP film was apparent on day 10 (data is not

(a) (b)

Figure 4. Decay incidence of fresh-cut winter squash packaged

in different films stored at 10˚C for 13 and 17 days. Each sym-

bol is the mean of three replicate measurements; vertical lines

represent SE. (□) 50 µm PE, (■) 90 µm PE, (■) 35 µm MPP, (■)

80 µm Ny/PE.

shown) while the activity of molds in fresh-cut squash

packaged in other three films occurred later. No mold

activity was recorded in fresh-cut winter squash packed

with 80 µm Ny/PE film on day 13 in both 1/4 and 1/8 cut

samples (Figure 4). High CO2 levels in both 90 µm PE

and 80 µm Ny/PE film suppressed fungal growth for at

least or over 10 days. Suppression of fungi in MPP film,

on the other hand, was less than 10 days. A decrease in

temperature has a tremendous effect on lowering respire-

tion rates, thereby lowering microbial activity. Moreover,

its affects on permeability of gases through the package-

ing films also slow microbial growth [17]. Occurrence of

mold growth was evident in either 90 µm PE or 80 µm

Ny/PE film.

Off-odor development was not detected in fresh-cut

squash packed in 35 µm MPP film until 6 days (Figure

5). On the other hand, the absence of O2 inside the pack-

age for other three films encouraged fermentative me-

tabolism resulting in the development of off-odor within

3 days in squash packaged in 80 Ny/PE film (Figure 5).

Sour smell was produced and became stronger in 6 days

as the package is opened. However, the sour smell dis-

appears once the fresh-cut winter squash are aerated for a

few minutes. It also worth noting that off-odor develop-

ment was much intense in fresh-cut winter squash cut

into 8 parts than 4 parts in 50 µm PE, 90 µm PE, and 35

µm MPP film. Higher number of cuts probably increased

respiration which can cause more off-odor development

of samples packaged in only 80 µm Ny/PE film. Both 80

µm Ny/PE and 90 µm PE films was best in suppressing

respiration by reducing O2 levels to almost zero and

similarly increasing CO2 levels within three days (Figure

1). This condition suppressed sensitivity of fresh-cut

winter squash of further ripening and the growth of mi-

croorganisms [11]. The CO2 levels on day 3 were 12 to

14% in 90 µm PE film and 30 to 40% in 80 µm Ny/PE

film that was more than enough to cause such suppres-

sion. In these conditions, off-odor development in winter

A. J. G. Gibe, J. G. Kim / Agricultural Sciences 4 (2013) 477-482 481

Figure 5. Off-odor development in fresh-cut winter squash

packaged in four different films (µm) and stored at 10˚C for 17

days. Off-odor was scored using a 0 to 4 hedonic scale where 0

= no off odor; 1 = slight; 2 = moderate; 3 = strong and 4 = se-

vere. Each symbol is the mean of three replicate measurements.

(●) 50 µm PE, (○) 90 µm PE, (▲) 35 µm MPP, (∆) 80 µm

Ny/PE.

squash in the early days of storage may not be a product

of microbial action since no signs of physical deteriora-

tion are apparent.

The shelf-life of fresh-cut winter squash packaged in

35 µm MPP was 6 days at 10˚C regardless of cutting size.

However, both 1/4 and 1/8 cut samples packaged with 90

µm PE films had longer than 10 days of shelf-life though

off-odor development was detected in the samples. The

samples had less mold incidence and the off-odor was

acceptable until 10 to 13 days in 1/4 and 1/8 cut treat-

ments, respectively.

4. CONCLUSION

Packaging film affected package atmosphere, mold in-

cidence, and off-odor development of fresh-cut winter

squash during the 10˚C storage. Firmness, SSC, and PH

of fresh-cut winter squash remained acceptable for at

least 10 days regardless of the cutting size. Mold was

detected in all packaging films after 17 days of storage.

However, less mold incidence was found in samples cut

into 8 parts and packed with 80 µm Ny/PE and 90 µm PE

films compared with 35 µm MPP film and 50 µm PE

film. Strong off-odor was detected in samples packaged

in 80 µm Ny/PE film after 13 days of storage. Therefore,

fresh-cut winter squash packaged with 90 µm PE film

maintained better quality with 10 to 13 days of shelf-life

in 1/4 and 1/8 cut, respectively at 10˚C.

5. ACKNOWLEDGEMENTS

The authors would like to acknowledge Rural Development Admini-

stration, Republic of Korea for supporting this project financially.

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