Development of heat sealable film from tapioca and potato starch for application in edible packaging

Abstract

This study aimed to fabricate edible films from tapioca (T) and potato (P) starch, assessing their physicochemical properties and biodegradation across different ratios (T100P0, T70P30, T50P50, and T30P70). The films underwent evaluation for moisture content, thickness, water vapor permeability, and color values. T100P0 and T30P70 formulations exhibited the highest film transparency at 43.51 and 43.93%. T30P70 exhibited (p < 0.05) water solubility at 38.62%. The film was heat-sealed as a seasoning sachet and tested for solubility at 90–95 °C. The 100% tapioca starch film (T100P0) displayed rapid dissolution (4 min 50 s), indicating potential use in heat-sealed. Seasoning sachets made from T100P0 demonstrated the highest elongation at break and the lowest tensile strength. Biodegradation assessment revealed complete degradation of all four film formulations in soil at ambient temperature within 8 days. This study underscores the promising utilization of tapioca starch in eco-friendly food packaging, providing a sustainable solution to the escalating issue of plastic waste in the environment. Future investigations will concentrate on refining the film and determining its shelf-life concerning film characteristics and packaged foods.

Introduction

Cassava is one of the widely cultivated crops in Thailand. According to the data presented in Krungsri Research (2023), Thailand emerged as the foremost exporter of cassava in the year 2020, with a volume of 7.1 million tons, ranking third globally in cassava production behind Nigeria and Congo. Over the past two decades, Thailand has witnessed a sustained expansion of its cassava cultivation area (approximately 55.5 million acres in 2021), a trend driven by the concurrent growth of the cassava processing industry and its subsequent impact on the export market. Cassava roots are mostly processed into tapioca flour and starch, which plays an important role in the country’s agricultural and industrial sectors. Thailand has a well-established tapioca processing industry, equipped with modern facilities and advanced technologies, and hence, offers a wide range of tapioca products to both domestic and international markets. Thai cassava products are cassava chips, cassava pallets, cassava native starch, cassava modified starch, and others including cassava root, cassava pulp, and sago (Krungsri research 2023). However, to promote sustainable development to the tapioca market, exploring value-added products to ensure the long-term viability and competitiveness of the industry is currently a major focus.

Tapioca starch is widely used as a food ingredient due to its unique functional properties, especially excellent gelling, and high viscosity functionalities, which contributes to texture enhancement, moisture retention, and stabilization (Hsieh et al. 2019). Tapioca starch has been used in various varieties of food products, for example, bakery, dairy and frozen desserts, sauces, dressing, soups, snack foods, meat, and seafood products. The use of tapioca starch in these applications provides manufactures with opportunities to develop high-quality, gluten-free, and consumer-appealing products (Ofman et al. 2004). Garcia et al. (2000) reported that cassava starch-based film showed greater thermal and mechanical properties compared to the film from waxy maze.

Potato starch is commonly used in developing edible starch-based film and has been reported for its characteristics and functionalities in many studies (Ballesteros-Mártinez et al. 2020; Fangfang et al. 2020). Starch is one of natural polymeric sources that is edible and biodegradable. Starch granules contain two macromolecules, amylose and amylopectin. When these granules are mixed with hot water and then cooled, they form a gel-like solution. This gel formation involves the formation of crosslinks between the amylose and amylopectin molecules, creating a network structure. As the water evaporates, the gel transforms into a film. The physical crosslinks in the starch’s macromolecular network are primarily formed by microcrystalline domains within the amylose (Wang et al. 2015; Otoni et al. 2021).

Edible films and coating are currently gaining significant attention as an alternative to plastic packaging due to their biodegradability, reduced environmental impact, and ability to enhance food safety. With growing concerns about plastic pollution and a preference for eco-friendly solutions, these edible materials offer a promising avenue to address both environmental and consumer demands. Starch-based film offers advantages in biodegradability, renewability, and compatibility with food matrices. Different types of starch were used in edible film development including potato, tapioca, wheat, and corn starch (Dai et al. 2019). Heat-seal ability is the ability of a material to form a secure and effective seal when exposed to heat. This is a crucial characteristic in packaging materials as it helps create a barrier that protects the contents from external elements such as moisture, air, and contaminants, ensuring the integrity of the product. The heat-seal ability of starch-based films can be enhanced by using glycerol, sorbitol, or other polymers like chitosan, lecithin, and gelatin (Cheng et al. 2021). According to literature reviews, starch has been a promising material for the development of edible and heat sealable films. However, publication of heat-sealable tapioca starch-based film is still limited till date. Therefore, objectives of this study are to develop heat sealable film from different ratios of tapioca and potato starch, and to determine physicochemical properties, and biodegradability assessments.

Materials and methods

Materials

Premium refined tapioca starch was obtained from Flourish Company Limited (Bangkok, Thailand) and potato starch were purchased from a supermarket in Thailand. Food grade soy lecithin and glycerin were purchased from Chemipan Corporation Co., Ltd. (Bangkok, Thailand).

Film preparation

The film-forming solution was prepared in 4 different ratios of tapioca and potato starch (100:0, 70:30, 50:50, 30:70) according to the method of Luchese et al. (2017) with some modifications. The film mixture was composed of 20 g of total starch, 10 g of soy lecithin, 10 g of glycerin, and 400 milliliters of distilled water (Table 1). All ingredients were homogeneously blended using a blender (BE-120, Otto, Thailand) for 1 min and poured into a pan through a strainer to remove bubbles. The solution was continuously stirred using medium heat until the temperature of the film solution reached 80–85 ^oC. The solution was then removed from the stove and poured into an acrylic sheet (size 20 × 50 × 0.6 cm) through the strainer to eliminate bubbles. The film was dried in a humidity control cabinet (NUVE TK120, Turkye) at 35 ^oC, 65% RH for 24 h. The dried film was removed from the acrylic sheet and kept for further analysis.

Table 1.

Film formulation with 4 different ratios of tapioca starch and potato starch

Film	Tapioca starch (g)	Potato starch (g)	Soy lecithin (g)	Glycerine (g)	Water (mL)
T100P0	20	0	10	10	400
T70P30	14	6	10	10	400
T70P50	10	10	10	10	400
T30P70	6	14	10	10	400

Moisture content

The moisture content of film samples was determined according to AOAC (2005) method with some modifications. The film was cut into 6 × 7 cm, weighed (M₁) and put in an aluminum can for drying at 105 ^oC for 24 h. After that, the aluminum can was cooled down in a desiccator, and then weighed the dried film (M₂). Moisture content was calculated and reported in percentage using Eq. (1).

1

Film thickness

The thickness of film (6 × 7 cm) was measured according to Ballesteros-Mártinez et al. (2020) using a digital micrometer with 0.001 mm accuracy (Zhongtian Experimental Instrument Co., Ltd. Zhengzhou, China). Four thickness measurements were randomly taken at different locations on each film and the average value was reported.

Water vapor permeability (WVP)

The WVP analysis was conducted following the standard test method ASTM E96 (ASTM 1995) with some modifications. Film size of 6 × 9 cm without visible scratch, bubble or leakage was used in this analysis. Dried silica gel (5 g) was weighed into a 30 mL beaker. The beaker was then covered tightly with film, recorded an initial weight before placed the beaker in a desiccator containing 50 mL of distilled water at ambient temperature. The beaker was recorded for its gaining weight every after 2 h for 12 h. The test was done in triplicate. Water vapor transmission rate was calculated using linear regression from the plot between time and weigh gain. Then, water vapor permeability can be calculated using Eq. (2).

2

Whereas

A is permeation area (m²)

X is average film thickness (mm)

W is water mass absorbed in silica gel (g)

t is permeation time (h)

is water vapor pressure between two sides of the film ( = 2758.6 Pa at 30 ^oC).

Water solubility

The water solubility was determined as per a method described by Choi et al. (2022) with slight modifications. A film sample (6 × 7 cm) was dried at 105 ^oC for 24 h and recorded for its weight (d_m1). The film sample was then submerged in a beaker containing 50 mL distilled water and put in a shaking incubator (LabTech LSL-1005R) for 24 h at 37 ^oC. After that, the remaining film was dried at 105 ^oC for 24 h and weighed (d_m2). The water solubility of the film was reported in percentage using Eq. (3).

3

Water solubility of the seasoning sachet

The sachet was prepared referring to the commercial size of seasoning sachet for instant noddle products. Film (6 × 7 cm) was heat-sealed 3 sides to form a sachet using 500 Electric pumping (filling) gas automatic packing machine (Henan Jinfuda Trading Co., Ltd., China). Sealing time and cooling time were set at 2.0 and 1.0 s, respectively. Two grams of commercial mixed seasoning powder was put into the sachet and heat-sealed the remaining side. The water solubility test was conducted by boiling 200 mL of distilled water on a magnetic hot-plate until the water reached 90–95 ^oC, which is considered as a cooking temperature for boiling soup. The seasoning sachet was then put in the boiling water while continuously stirred and recorded the time usage until the film was completely dissolved.

Mechanical properties of the film

Tensile strength (TS) and Elongation at break (EAB) of film samples were measured as per the method of Tongnuanchan et al. (2016) with a slight modification using a Texture Analyzer model TS-XT plus (Stable Microsystems Texture Technologies Inc., UK). Film was cut into 2 × 7 cm; each side of the film was clamped to tension measurement head (A/TG). The setting values were a distance between the clamps at 50 mm, 50 mm/min of crosshead speed, using a 50 N static load cell. Nine specimens of each sample were used for measurement. Tensile strength and elongation at break were using Eq. (4) and Eq. (5):

4

5

Whereas

F_max is maximum force (N) to pull the film apart

A is cross-sectional area (m²)

L₀ is initial film length (mm)

L is film elongation when rupture (mm)

Color measurement

A handheld colorimeter (CR-400 Chroma meter, Konica Minolta) was calibrated with a standard white tile before measurement. Film was placed on a white surface, while a colorimeter was placed perpendicularly over the film and recorded L*, a* and b* values. L* indicates the brightness level (from white to black), (a*) represents the chromatic index between green and red and (b*) identifies the chronic values from yellow to blue.

Film transparency

Transparency of film was determined according to Chandrasekar et al. (2023), using a 1 × 5 cm, put the film in a cuvette. The transmittance (%) was recorded from a spectrophotometer (DR2700) at 600 nm wavelength. An empty cuvette was used as a blank.

Biodegradability of the film

Loamy soil was put in a plant tray, a film (6 × 7 cm) was buried 4-cm deep under the soil. The film was covered with soil and kept the tray under shade, watered 2 times per day. The film characteristic was pictured every 2 days.

Statistical analysis

Data was calculated for average values and standard deviation. Significance difference between means was evaluated using analysis of variance (ANOVA) with Duncan’s Multiple Range Test (DMRT) at 95% confident level. The experimental data were analyzed using IBM SPSS Statistics for Windows, Version 29.0, (IBM Corp. Released 2022, Armonk, NY).

Results and discussion

According to results depicted in Table 2, moisture content of the film composing different ratio of tapioca and potato starch were non-significant, ranging from 21.62 to 23.86%. The moisture content observed in this investigation aligns with that reported for edible films made from different starch reported by Luchese et al. (2017) and Putri et al. (2023). Film thickness demonstrated variability between 0.18 and 0.21 mm (p > 0.05). Water vapor permeability (WVP) values for all film conditions did not exhibit significant variations; however, a trend was observed where WVP tended to decrease with an increase in potato starch content. This phenomenon may be attributed to the higher amylose concentration in potato starch, leading to the formation of more organized linear structures with elevated crystallinity (Talja et al. 2008; Menzel et al. 2015). The linear structure allows tight packing and strong intermolecular interactions. The organized structures create crystalline regions in the films and resulted in water vapor barrier (Garcia et al. 2000). The WVP values for all film samples in this study ranged from 0.0016 to 0.0019 g·mm/m²·h·Pa, comparable to the WVP of rice starch film (0.0017 g·mm/m²·h·Pa) reported by Majzoobi et al. (2015) but were lowered than those of mung bean starch (0.2–0.46 g·mm/m²·h·Pa, Zuo et al. 2019). In comparison, the WVP values of petroleum-based materials were significantly lower, with values of 0.00001 g·mm/m²·h·Pa for high density polyethylene, 0.00003 g·mm/m²·h·Pa for low density polypropylene and 0.00005 g·mm/m²·h·Pa for polyethylene terephthalate (Bangar et al. 2021).

Table 2.

Chemical analysis of films developed from tapioca and potato starch

Film	Moisture contentNS (%)	ThicknessNS (mm)	Water vapor permeabilityNS (g.mm/m2.h.Pa)	Water solubility test
				Film (%)	Seasoning sachet (min.sec)
T100P0	21.62 ± 2.41	0.18 ± 0.05	0.0016 ± 0.0001	38.62 ± 4.29b	4.50 ± 1.29a
T70P30	23.06 ± 1.09	0.20 ± 0.04	0.0019 ± 0.0001	35.70 ± 2.15a	6.10 ± 0.70ab
T50P50	23.86 ± 2.71	0.21 ± 0.05	0.0016 ± 0.0000	34.57 ± 1.62a	9.02 ± 2.23c
T30P70	22.03 + 1.74	0.21 ± 0.04	0.0016 ± 0.0002	32.92 ± 2.87a	7.06 ± 0.85b

Note: ^a−c Average values in the same column with different letters showed significant difference (p ≤ 0.05), ^NS represented no significant difference (p > 0.05)

Water solubility, indicative of the film’s water resistance, is a crucial property for food applications. In this study, the T30P70 film exhibited significantly lower water solubility compared to other film samples (Table 2). Furthermore, a noticeable decrease in water solubility with an increasing concentration of potato starch was observed, consistent with the findings of Yun and Yoon (2010). Gelatinization of amylose can lead starch to absorb water and undergo structural change, resulting in swelling, dispersion of starch molecules and forming a compact structure upon gelatinization. This phenomenon then reduced water penetration and lowered solubility of the film. In addition, water solubility of seasoning sachets followed a similar trend, with the sachet made from 100% tapioca starch was completely dissolved in the shortest time at less than 5 min (p ≤ 0.05). Seasoning sachets made from tapioca and potato starch were shown in Fig. 1. The inclusion of soy lecithin and glycerol in this study contributed to the improved heat-seal ability of the film. These additives enhance interfacial compatibility forming a thin layer at film interface, promoting adhesion between two surfaces during heat sealing. This improved interfacial adhesion facilitates the formation of strong intermolecular bonds, resulting in a secure and reliable seal (Kim and Ustunol 2001).

Fig. 1.

Heat-sealed seasoning sachet made from tapioca (T) and potato (P) starch-based film

Tensile strength (TS) and elongation at break (EAB) serve as pivotal mechanical benchmarks, elucidating the intricate response of films to tensile forces, elucidating the behavior of film under stretching forces. TS indicates film robustness and structural integrity, whereas EAB represents film flexibility, pliability, and resilience, reflecting its capacity to undergo deformation. Figure 2 revealed a compelling negative correlation between TS and EAB across all film samples. The film made from 100% tapioca starch exhibited the lowest TS and concurrently the highest EAB among all film formulations (p ≤ 0.05). This value aligned with a report from Torres et al. (2011) that the highest EAB values was observed in cassava starch film. The increase in potato starch made films more rigid and less flexible, limiting their capacity for stretching before rupture. This phenomenon is attributed to the elevated amylose content fostering a densely organized structure. The presence of more microcrystalline domains in the starch-based film results in higher tensile strength of the film. Producing starch film at elevated temperatures and low humidity conditions leads to a lower degree of crystallinity in both amylose and amylopectin. On the other hand, the degree of crystallinity in the starch film increases as the amylose content in the starch increases (Jiang et al. 2020).

Fig. 2.

Tensile strength (TS) and Elongation at break. (EAB) of films. Different letters (a, b) on the same line indicated significant difference at p ≤ 0.05

All films with different ratios of tapioca and potato starch exhibited yellowish color which was contributed by the color of soy lecithin. All color characteristics of films; lightness (L*), redness (a*) and yellowness (b*), were not significantly different (Table 3). Transparency of the film was expressed as percentage of light transmission, which could be interpreted to the light protection ability. It could be seen from the results in Table 3 that films T100P0 and T30P70 showed the highest in film transparency (p ≤ 0.05), 43.51% and 43.93%, respectively. However, all film samples in this study had lower transparency than the result of pure starch film reported by Ali et al. (2018). The conditions used in this study could promote intense starch crystalline upon gelatinization, and hence resulted in film transparency lower than 50%. It is believed that film with low transparency can help protect packaged food against UV radiation.

Table 3.

Transparency and color values of films developed from tapioca and potato starch

Film	Transparency (%)	Color values
		L*NS	a*NS	b*NS
T100P0	43.51±4.69b	81.73±7.59	0.26±0.46	16.76±1.55
T70P30	38.30±0.48a	82.99±3.77	0.31±0.47	17.11±2.81
T50P50	38.18±2.22a	82.71±0.237	0.34±0.52	18.58±3.31
T30P70	43.93±2.97b	84.13±3.04	0.20±0.45	16.45±1.93

Note: ^a−b Average values in the same column with different letters showed significant difference (p ≤ 0.05), ^NS represented no significant difference (p > 0.05)

The result from film’s biodegradability determination was outstanding because all film conditions presented the deformation since the first two days of observation (Fig. 3.), and they were completely decomposed at the eighth day as there was no film residual found under the soil. By far, this study presented the shortage time in complete degradation (within 8 days) compared to 20 days of tapioca starch film reported by Maran et al. (2014). However, the important drawback of starch based biodegradable films is the hydrophilic character which leads to the decrease in stability of the film when subjects to diverse environment conditions (Molavi et al. 2015).

Fig. 3.

Biodegradability test of developed films

Conclusions

The purposes of this study were to develop edible and heat-sealable film, and also to apply it as an edible seasoning sachet in order to replace synthetic plastic material in food packaging. The findings in this study revealed that tapioca starch could be a potential material for plastic packaging replacement: not only its rapid biodegradability, but also quickest solubility in boiling water. Its heat-seal ability could benefit wide varieties of applications in the coming future. Although this study presented possible application as a sachet for dry ingredients, we also observed its ability on packing cooking oil and watery ingredients such as sauce, however, the film lost its integrity in a short time. Therefore, the next study will focus on improving the film and determination its shelf-life in terms of film’s characteristics, and packaged foods.

Author contributions

SS and SF performed the experiments, data analysis, and drafted the manuscript; SR provided concept and scope of the study, supervised the work, and edited the manuscripts.

Funding

Not applicable.

Data availability

The data presented in this article are available in the article.

Code availability

Not applicable.

Declarations

Ethical approval

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Consent to participate

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Consent for publication

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Conflict of interest

The authors declare no conflicts of interest.