Design of Biodegradable Bio-Based Equilibrium Modified Atmosphere

Home , Modified atmosphere

Postharvest Biology and Technology 111 (2016) 380–389

Contents lists available at ScienceDirect

Postharvest Biology and Technology

journal homepage: www.elsevier.com/locate/postharvbio

Design of biodegradable bio-based equilibrium modiﬁed atmosphere

packaging (EMAP) for fresh fruits and vegetables by using

micro-perforated poly-lactic acid (PLA) ﬁlms

a, a a

Antonis Mistriotis *, Demetrios Briassoulis , Anastasios Giannoulis , b

Salvatore D’Aquino

Agricultural University of Athens, Laboratory of Agricultural Structures, 75 Iera Odos, Athens, 11855 Greece

National Council of Reserch of Italy—Institute of Sciences of Food Production (ISPA-CNR), Traversa La Crucca, 3, loc. Baldinca, Li Punti - 07100 Sassari, Italy

A R T I C L E I N F O A B S T R A C T

Article history: Equilibrium modiﬁed atmosphere packaging (EMAP) is used for prolonging the shelf life of fresh produce

Received 12 February 2015

such as fruits and vegetables and preserving their quality characteristics such as freshness, colour and

Received in revised form 3 September 2015

aroma. However, the resulting extensive use of plastic packaging ﬁlms raises serious environmental

Accepted 14 September 2015

concerns. Replacing conventional plastic ﬁlms with novel biobased and biodegradable under composting

conditions materials such as ﬁlms made of poly-lactic acid (PLA), offers new sustainable solutions to the

Keywords:

problem. In the present work, the gas transport properties of three layer PLA ﬁlms have been studied in

EMAP

relation to their potential as EMA packaging materials for fresh produce. A simple one-dimensional

PLA ﬁlm

model simulating the combined gas diffusion through micro-perforations and the permeable membrane

Gas diffusion

Micro-perforation was developed as a designing tool for PLA based EMA packaging systems. By using this model, innovative

ﬁ

Horticultural produce packaging biodegradable bio-based EMAP systems were designed speci cally for selected fruits and vegetables

ﬁ

Bio-based materials using laser microperforated, water vapour (WV) permeable PLA lms. It was shown that the relatively

Bio-based packaging high water vapour permeability of PLA ﬁlms compared to conventional OPP ﬁlms allows the development

of an optimised biodegradable bio-based EMA packaging for the speciﬁc applications.

1. Introduction the temperature increases O2 requirements from tissues increase

too, while tolerance to CO2 decreases (Kader, 1997).

Fruits and vegetables are two of the main agricultural product The main disadvantage of EMAP, like any other conventional

categories in Europe. Packaging is particularly important for food packaging, is the extensive use of plastic ﬁlms resulting into

exported fruits as it allows preserving their quality and health huge quantities of domestic plastic wastes. Global plastic ﬁlm and

safety and facilitates labelling of the produce. Recently, advanced sheets market is expected to reach 70.9 million tons by 2018

techniques such as equilibrium modiﬁed atmosphere packaging (Markets and Markets, 2014). A large percentage of this quantity is

(EMAP) for dynamically modifying the in-package atmosphere are used for food packaging. Although recycling of these materials

used for extending the shelf life of high value fresh produce increased during the last decade, only a small part of the generated

(Sandhya, 2010). amount of plastic waste is ﬁnally recycled (Themelis et al., 2011).

Successful applications of EMAP include a wide variety of Therefore replacing non-degradable conventional plastics based

produce, such as broccoli florets, cauliflower florets, carrots, baby on fossil oil with sustainable bio-based biodegradable materials is

carrots, peeled garlic (Lee et al., 1996). However, most of the of great environmental importance. Various bio-based plastics

published studies for recommended CO2 and O2 concentrations have been studied already as possible alternatives to conventional

generally represent the conditions in the temperatures range of 0– packaging materials (Siracusa, 2008).

5 C that maximize the storage life of each commodity (Fernández- Such a promising biodegradable plastic material is poly-lactic

Trujilio et al., 1988; Malakou and Nanos, 2005; Irtwange, 2006). As acid (PLA). PLA was introduced as a packaging material and started

being produced at a commercial level about ten years ago. It has

attracted attention mostly because of its sustainable nature: it is

* Corresponding author. Fax: +30 2105294023. synthesized from processed corn or other naturally produced

E-mail address: [email protected] (A. Mistriotis).

http://dx.doi.org/10.1016/j.postharvbio.2015.09.022

A. Mistriotis et al. / Postharvest Biology and Technology 111 (2016) 380–389 381

carbohydrates, thus it is a bio-based material, and it biodegrades contribute to a longer shelf-life of the packaged produce (Almenar

after use under industrial composting conditions (Auras et al., et al., 2008; Briassoulis et al., 2013).

2004). The main objective of the present work was the development of

a one-dimensional steady state analytical model of the in-package

PLA can be used for the development of transparent thin ﬁlms

atmosphere assuming that WV transport process through the

suitable for food packaging (Auras et al., 2004). PLA’s certiﬁed

permeable packaging ﬁlm obeys Fick’s law. Using this analytical

compostability and compliance with the food contact safety

model, packaging bags made of PLA have been optimally designed

regulations (Auras et al., 2004) makes it attractive as packaging

and developed for two selected horticultural produce: cherry

material, since it meets the compostability requirements of

tomatoes and peach, as typical high value vegetables and fruits

EN13432 for packaging (EN 13.432, 2005), thus alleviating the

respectively. These optimized packaging systems were tested

plastic wastes problem. PLA exhibits high water vapour (WV)

through full-scale experiments to conﬁrm the validity of the design

permeability compared to conventional plastic packaging ﬁlms,

methodology.

while its permeability to CO2 and O2 is comparable.

The performance of an EMA packaging greatly depends on its

2. Materials and methods

optimised design which has to be tailored to the needs of the

speciﬁc packaged produce. Gases are exchanged between the

2.1. Deﬁnitions and terminology

package and the environment by a restricted diffusion process

resulting into an EMA in the package. In a typical EMAP the

Before presenting the relevant methodology and the results of

synthesis of the in-package atmosphere is controlled by selecting

the present work, it is important to clarify the deﬁnitions related to

the gas transport properties of the packaging ﬁlm. The equilibrium

the diffusive gas transport through membranes in order to avoid

(steady state) modiﬁed atmosphere (EMA) is obtained when the

confusions, as the relevant terminology is not unique in the

exchange rate of gases through the covering ﬁlm is in equilibrium

literature. The gas barrier property of a material is expressed by its

with the production or consumption of gases at the respiring and 2 1 1

gas mass permeability P (kg m m s Pa ). This is deﬁned as the

transpiring produce. Therefore, the gas transport properties of the

gas mass (kg) which, under steady conditions, crosses unit area

ﬁ

packaging system have to be designed to meet the speci c 2

(m ) and unit thickness (m) of the specimen, in unit time (s) under

requirements of the packaged produce. A technique for adjusting

unit pressure difference (Pa) and at constant temperature. In

the gas transport properties of a packaging ﬁlm is perforation. Both

particular, the permeability of a plate or membrane is expressed by

macro-perforation by mechanical means (Van der Steen et al.,

the one-dimensional Fick’s law of diffusion as:

2002) and laser made micro-perforation (Ozdemir et al., 2005) are

used for this purpose. In the case of a perforated ﬁlm, the diffusion dp

F ¼ P A ð1Þ

is not spatially uniform and the combined transmission effect of dx

both perforations and ﬁlm has to be investigated. The size and the 1

where F (kg s ) is the mass ﬂow rate of the gas, dp=dxis the

number of perforations have to be estimated to meet the speciﬁc 1

gradient of the gas pressure across the specimen (Pa m ) and A

needs of the packaged fruits or vegetables for a given packaging 2

(m ) is the area of the membrane. If a gas mixture is considered, gas

conﬁguration. For this reason, the development of a model

pressure, p (Pa) refers to the partial pressure of a gas in the mixture,

predicting the gas transfer through a perforated ﬁlm is a necessary

thus it is a measure of the molar fraction, c, of the gas in the

tool for designing the perforation pattern. Such a model has to take

mixture.

into account the combined gas transport through both the

In the case of a gas mixture, the partial pressure gradient can

packaging ﬁlm and the perforations (Paul and Clarke, 2002;

also be expressed as the molar fraction gradient of the gas,

Rennie and Tavoularis, 2009; Briassoulis et al., 2013). 1

dc=dx(m ). Then the mass permeability is expressed in (kg m

Several attempts have been made to model gas transfer through 2 1 2 1

m s ) and the volume permeability in m s .

a perforated permeable ﬁlm for optimizing EMAP (Paul and Clark,

When a thin ﬁlm is considered, its gas transfer characteristics

2002; Rennie and Tavoularis, 2009). These models focus on the gas

are described by the permeance, PR. In the Standard ASTM-E96/

diffusion through a perforation (Chung et al., 2003), while the ﬁlm 2 1

E96-05 (ASTM, 2005) water vapour permeance PR (kg m s ) is

itself is considered impermeable (barrier ﬁlm) (Chung et al., 2003;

deﬁned by the equation:

Gonzalez et al., 2008). Such modelling approaches are based on

Fick’s law of diffusion (Chung et al., 2003) or Stefan–Maxwell law F P

PR ¼ ¼ ð2Þ

(Rennie and Tavoularis, 2009). The simplest model assumes Fick’s A Dc L

diffusion in a cylindrical pore ﬁlled with stagnant air simulating

where L (m) is the thickness of the thin ﬁlm.

the perforation. However, an end correction term for the diffusive

An additional, practically used measure of the barrier property

path length must be introduced to compensate for end effects at

of a ﬁlm is its gas transmission rate, TR. In the Standard ASTM-E96/

the mouths of the hole (Chung et al., 2003). Certain models also 2 1

E96-05 the transmission rate TR (kg m s ) of a gas through a ﬁlm

take into account convection mass transfer in the headspace 2

of thickness L (m), that crosses unit area (m ) of the specimen, in

between the produce and the packaging ﬁlm due to temperature

unit time (s) for a speciﬁc molar fraction difference Dc, is then

differences (Rennie and Tavoularis, 2009). However, this effect has

deﬁned as: a limited importance.

¼ ¼ D ð Þ

Relevant to the present work are studies concerning the use of TR PR c 3

ﬁlms made of other biodegradable materials for food packaging

(Avella et al., 2005; Siracusa et al., 2008). Most of these bio-based

2.2. The modiﬁed Fick’s law for gas diffusion through a hole

ﬁlms are rather permeable in water vapour. The gas transport

properties of these ﬁlms are particularly interesting for further

2 1

The diffusion coefﬁcient D (m s ) of a gas in a gas mixture, optimizing EMAP systems.

3 1

such as air, is deﬁned as the diffusion volume ﬂow rate F (m s )

The present work focuses on the use of micro-perforated PLA D

ﬁ ﬁ

lms for designing optimized equilibrium modi ed atmosphere divided by the molar fraction gradient of the gas, dx, per unit area.

packaging (EMAP) for fresh fruits and vegetables. Recent studies The gas diffusion through a single perforation (e.g., an

indicate that PLA is a versatile packaging material, which may impermeable ﬁlm with one hole) may be modelled as diffusion Download English Version: https://daneshyari.com/en/article/4517894

Download Persian Version:

https://daneshyari.com/article/4517894

Daneshyari.com