IJERD – International Journal of Environmental and Rural Development (2015) 6-1

Research article
erdApplication of Biodegradable Film from Yam(Dioscorea alata) Starch in Thailand for Agriculture Activity
OROSE RUGCHATI*
Faculty of Agriculture Natural Resources and Environment, Naresuan University, Phitsanulok,
ThailandE-mail: oroser@nu.ac.th

KANITA THANACHAROENCHANAPHAS
Faculty of Agriculture Natural Resources and Environment, Naresuan University, Phitsanulok,
ThailandReceived 13 December 2014

Accepted 1 April 2015(*Corresponding Author)

Abstract Starch sample obtained from water yam (mun lued) by wet milling process. Yam
starch films were prepared by thermal gelatinization technique casting using glycerol asplasticizer. The effect of different glycerol (1.65 and 2.00 g/100 g of filmogenic solution)
starch concentration (3.30 g/100 g of filmogenic solution) was evaluated for somecharacteristic of these films. The effect of different surfactant Span80 (1 ml/100 g offilmogenic solution) and Tween 20 (1.5 ml/100 g of filmogenic solution) was studied.
Suitable characteristic of biodegradable film from yam starch are glycerol 1.65 and span 80(1 ml/100 g) as filmogenic formulation. The temperature for obtaining gelatinized starchsolution was 70-80 °C and then dried at 45 °C for 4 hours. Film sample was molding inplastic bag form by simple sealing machine in average size 6x9 square inch. The samples
expected to be applied as agriculture bag for agriculture activity. As a result, the appearanceof film sample was smooth, transparence and glossy, with average moisture content of
25.96% and thickness of 0.01 mm. Puncture deformation and flexible increased withglycerol content. The starch and glycerol concentration were significant factors for yam
starch film characteristic. Surfactant Span80 increased smoother and reduce sticky
properties of film than Tween 20. Yam starch film as biofilms could be applied anddeveloped in qualities, and with the advantage of biodegradability.
Keywords biodegradable film, yam starch in Thailand, Dioscorea alata, agriculturalactivity

INTRODUCTION
Water yam (mun lued) or greater yam (Dioscorae alata) belonged to Family Dioscoraeceae is afood crop of economic value in Africa and Asia. The yam produces tubers, bulbils or rhizomes as astarch staple food. Edible yams being most frequently cultivated in tropical area. Originaly fromSoutheast Asia, yam tubers were distributed in all regions of Thailand. However, the main
utilization of yams tubers in Thailand only for home consumption and local economic food, not inindustrial scale. Yam also used for extraction starch in commercial scale when compare with otherstarch source such as cassava, potato, maize, wheat and sweet potato. Yam starch can be extracted
from tubers by wet milling using water as the extracting solvent. The starch extracted by thismethod are very pure. One starch content was 97-98.53% (dry basis) when estimated by enzymatic
method. The granular size of yam starch averages is 26.68 µm. Some physic-chemical
characteristics of yam starch are difference from cassava starch so it could be applied not only forfood industry but also non-food industry (Rugchati et al., 2013).
Edible and/or biodegradable films are made from renewable and natural polymers. Among thenatural polymers, biodegradable films are not meant to totally replace synthetic packaging films.
However, they do have potential to replace the conventional packaging in some applications. TheⒸ ISERD28

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use of edible films and coatings has been constantly increasing in the food industry. Coatings help
meet many challenges related to the storage and marketing of food products. The functionality andperformance of edible films and coatings depend on their barrier and mechanical properties, which
in turn depend on film composition, its formation process, and the method of application onto theproduct. Edible films include lipids, proteins, and carbohydrates, such as cellulose, starch, and theirderivates in their formulation (Falguera et al., 2011; Carvalho, 2013). The use of a biopolymer,
such as starch can be an interesting solution as one of the most promising candidates for futurematerials because this polymer is cheap, abundant, biodegradable, and edible with thermoplastic
behavior and this is important for film production because amylose is responsible for the filmforming capacity of starches (Rugchati and Thanacharoenchanaphas, 2010; Hoover, 2001; AOAC,
1990). Plasticizers, such as glycerol, are often used to modify the mechanical properties of the film.
Plasticizers decrease intermolecular attractions between adjacent polymeric chains increasing film
flexibility, but they may also cause significant changes in the barrier properties of the film
(Bertuzzi et al., 2007; Brandelero et al, 2010; Carvalho, 2008 and 2013). Starch is one of the mostcommonly used agricultural raw materials since it is a renewable source, inexpensive (even cheaper
than polyethylene), widely available, and relatively of the most promising candidates for futurematerials because this polymer is biodegradable and edible with thermoplastic behavior that easy tohandle.
Yam starch is one alteration for polymeric carbohydrate composed of anhydroglucose units. It
is not a uniform material and most starch contains two types of glucose polymers: a linear chain
molecule termed amylose and a branched polymer of glucose termed amylopectin (Falguera et al.,2011). The ratio of amylose to amylopectin content is critical for technological applications. Yamstarch (D. alata) contains about 24-26% amylose; the ratio of amylose to amylopectin content is
0.32, and this is important for film production because amylose is responsible for the film-forming
capacity of starches (Al-Hassan and Norziah, 2012; Alves et al., 2007). The potential of starch as amaterial for edible films and for biomaterials has been widely recognized. It is an appropriate
matrix-forming material and it provides a good barrier to oxygen and carbon dioxide transmission
but a poor barrier to water vaporation (Maliet al., 2002; Bertuzziet al.,2007). One of the mostimportant limitations of the use of starch for films and coatings is the hydrophilicity of this material.
Preponderance of amylose in starches gives stronger film. The branched structure of amylopectin
generally leads to films with different mechanical properties, such as decreased tensile stress.
Surfactants could be incorporated into the film formulation to reduce surface tension of the solution,
improving the wettability and adhesion of the film. These chemicals components are characterized
for being amphiphilic. The lipophilic part of the molecule tends to be in a nonpolar environment
and the hydrophilic part prefers to be in a polar (aqueous) environment. The balance between two
governs the functionality of the surfactant at interfaces and also its influence on the properties ofthe resulting films. With surfactant addition to film formulation, it is expected a decrease in water
vapor permeability values, because some hydrophobic characteristic were incorporated withcomponents. Sorbitan fatty acid esters (Spans) and the corresponding polyoxyethylene (POE)
adducts (Tweens) applied in a wide range of food, pharmaceutical and other industries. In someformulations, mixtures of Span surfactants and Tween surfactants are required, but some of thephysical properties of these mixtures are not well defined (Alves et al., 2007; Brandelero et al.,2010).
OBJECTIVE
The objectives of this study were to evaluate the influence of the presence of plasticizers (glycerol),and the influence of different surfactant (Span80 and tween 20) on Dioscorae alata film
characteristics, and the mechanical properties of starch films for suitable formulation of yam starch
film products that could be applied and developed in qualities, and with the advantage of
biodegradability in agricultural activities.
METHODOLOGYⒸ ISERD

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Raw Material
Fresh tubers of water yam or mun lued (Dioscorae alata), with uniform size and shape, without any
mechanical and pathological injuries were obtained from a local farm in Phitsanulok, Thailand.
Sample Preparation
Yam starch was extracted in the wet milling process (Rugchati and Thanacharoenchanaphas., 2010).
Amylose and amylopectin contents of yam starch were determined simultaneously by the Knutson
method (Knutson, 1986).
Film Preparation
Yam starch film was prepared by thermal gelatinization technique (Mali et al., 2002) with different
glycerol, Span80 (Arlacel 80: Sorbitan monooleate (oily liquid) HLB 4.3) and Tween 20(Polysorbate 60: Polyoxyethylene (20) Sorbitan monolaurate (yellow liquid) HLB 16.7) yam starchconcentration (3.30 g /100 g of filmogenic solution) (Brandelero et al., 2010; Rugchati et al., 2013).
The four filmogenic solution formulations selected were milligram of surfactant/100 g offilmogenic solution and gram of glycerol/100 g of solution (Table 1).
Table 1 Filmogenic solution formulations (100 g of solution)
Formulation
abcdGlycerol (g)
1.65
1.65
2.00
2.00

Surfactant (ml)Span80 (1 ml)
Tween 20 (1.5 ml)
Span80 (1 ml)
Tween 20 (1.5 ml)

The films were prepared by casting; yam starch (dry basis) and glycerol were directly mixed
with distilled water to make batches with a total weight of 500 g. The filmogenic solutions weretransferred quantitatively to the cup of a Brabender Viscograph, and its were heated from 30 to80 °C at a constant heating rate (2 °C/min) and maintained at 80 °C for 10 min, with regularshaking (75 rpm). Gelatinized suspensions were immediately poured on rectangular acrylic plates(20x20 cm). For each experiment, the quantity of starch suspension poured onto the plate wascalculated to obtain a constant weight of dried matter of approximately 12.25 mg/cm2. The starchsuspensions were dried (45 °C) in a ventilated oven (about 4 h). The result was translucent films,
which can be easily removed from the plate. The films were equilibrated at room temperature and arelative humidity (RH) of 70 % for 48 h before being tested (Mali et al., 2005 and 2006).
Characterization of Starch Films
Yam starch films were characterized by using electron microscopy scanner (SEM), JEOL JSPM
100 electron microscope (Japan). Water vapor permeability (WVP) ASTM E96-80 (ASTM, 1980)
with water vapor permeation tester: Lyssy L80-4000, Oxygen gas transmission (OGT) ASTM
D3985-81(ASTM, 1981) with Oxygen permeation tester Illinois 8000 (TISI Standard 1136-2536)(Rugchati et al., 2013).
Physical and Mechanical Properties
Thickness measurements: The thickness of the films was determined using a manual micrometerat 10 random positions on the films. The mean standard deviation within the film was about 5% of
the average thickness by micrometer (EDP63191 The L.S. Starrett Co., Athol, MA Micrometer).
Moisture content of film wasmeasured by infrared automatic moisture meter (MA 40
SARTORIUS), and color measurement by Hunter Lab (model DP9500) (Rugchati et al., 2013).
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Mechanical properties: The tensile properties and puncture tests were studied to determine force
using an Instron 4411 (Instron Ltd., Canton, USA) (Rugchati et al., 2013).
Statistical Analysis
Statistical analyses were conducted by one-way analysis of variance. Means were compared using
the Duncan's new multiple range test. Data analyses were performed using the SPSS 11.5 forWindows.
RESULTS AND DISCUSSION
Raw Material
Some morphologilcal characteristics of the water yam tuber, leaf, starch sample, and starch granuleshape (SEM 1000X) can be seen in Fig. 1.

Fig. 1 Some morphologilcal characteristics of the water yam tuber A. leaf, B. whole tuber
and pulp, C. starch sample and D. starch granule
Table 2 Some physic-chemical characteristic of yam starch film
Treatment Moisture (%)
a26.00+0.04nsb
25.99+0.70nsc
25.97+0.10nsd25.89+0.74ns

Thickness (µm)
0.01
0.01
0.01
0.01

L*
WVP(g/m2/day)
25.09+0.54a
2105+0.5a
24.99+0.54a
2099+0.8a
24.29+0.54b
2087+0.3b
24.19+0.54b
2079+0.8b

OGT(cm3/m2/day)
13.10+0.5a
12.95+0.5a
11.42+0.5b
12.00+0.5b

Note: All values are mean±standard deviation
a–b Means within a column with different letters are significantly different (p≤ 0.05)

Table 3 Mechanical characteristic of yam starch film
Formulation
abcdMax load (mm)0.54+0.09a
0.41+0.12b
0.37+0.10c
0.40+0.74b

Max SIR (Kgf)
1.08+0.00a
0.99+0.58a
0.29+0.54b
0.25+0.54b

Toughness (Kgf/mm2)0.025+0.00ns
0.023+0.05ns
0.025+0.5ns
0.024+0.5ns

Note: All values are mean ±standard deviation
a–c Means within a column with different letters are significantly different (p≤ 0.05)

The fresh root of the water yam consisted mainly of starch (65%), and the purple tuber pulp ishigh in moisture content (82%). Starch was extracted and purified from the fresh root. The color ofthe starch was slightly white and fine powder. The starch granular shape was triangular and theaverage size was 26.68 µm (Rugchati et al., 2013).

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Characterization of Yam Starch Films
The appearance of yam starch film for most of the formulations was transparent, smooth, andglossy and some physic-chemical characteristic has shown on tables 2 and 3.
CONCLUSION
This research showed the characterization of yam starch film. Starch from water yam mixed withand glycerol 1.65 and span80 (1 ml/100 g) were used as filmogenic formulation. The appearance ofyam film is clearly smooth and glossy. In other characteristics, the concentration of glycerol andsurfactant were a significant factor. In mechanical properties, type and concentration of surfactant
enhanced the puncture properties and a higher concentration of glycerol and surfactant decreased
puncture and tensile properties. Glycerol concentration was a significant factor for WVP and O2.
ACKNOWLEDGEMENTS
This research was supported by Naresuan University, Thailand and The Higher Education
Commission for Research Funding. The authors are also grateful and special thanks to the Facultyof Agriculture Natural Resources and Environment, Naresuan University, Phitsanulok, Thailand
and Center for Agricultural Biotechnology, Faculty of Agriculture, Natural Resources andEnvironment, Naresuan University.
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