Pea Starch Films Research Articles

Effects of primary, secondary and tertiary structures on functional properties of thermoplastic starch biopolymer blend films

To better understand the correlation between structure and properties in thermoplastic starch biopolymer blend films, the effects of amylose content, chain length distribution of amylopectin and molecular orientation of thermoplastic sweet potato starch (TSPS) and thermoplastic pea starch (TPES) on microstructure and functional properties of thermoplastic starch biopolymer blend films were studied. After thermoplastic extrusion, the amylose contents of TSPS and TPES decreased by 16.10 % and 13.13 %, respectively. The proportion of the chains with the degree of polymerization between 9 and 24 of amylopectin in TSPS and TPES increased from 67.61 % to 69.50 %, and from 69.51 % to 71.06 %, respectively. As a result, the degree of crystallinity and molecular orientation of TSPS and TPES films increased as compared to sweet potato starch and pea starch films. The thermoplastic starch biopolymer blend films possessed a more homogeneous and compacter network. The tensile strength and water resistance of thermoplastic starch biopolymer blend films increased significantly, whereas thickness and elongation at break of thermoplastic starch biopolymer blend films decreased significantly.

The relationship between molecular structure and film-forming properties of thermoplastic starches from different botanical sources

To illustrate the correlations between molecular structures and the film-forming properties of thermoplastic starch from various botanical sources, starches from cereal, tuber and legume were modified by thermoplastic extrusion and the corresponding thermoplastic starch films were prepared including thermoplastic corn starch (TCS), thermoplastic rice starch (TRS), thermoplastic sweet potato starch (TSPS), thermoplastic cassava starch (TCAS) and thermoplastic pea starch (TPES) films. TPES film displayed a higher tensile strength (6.28 MPa) and stronger water resistance, such as lower water solubility (15.70 %), water absorption (42.35 %), and water vapor permeability (0.285 g·mm·h−1·m−2·kPa−1) due to higher contents of amylose and B1 chains. TCAS showed a smoother and more amorphous film due to higher amylopectin content, resulting higher elongation at break and larger opacity. TCS film was the most transparent due to a compacter network and more ordered crystallinity structure, which was suit for the packaging of fresh vegetables and aquatic products, whereas TCAS film was the opaquest, which protected package foods from light such as meat products, etc. The outcome would provide an innovative theory to regulate accurately the functional properties of thermoplastic starch films for different food needs.

Edible films to improve quality and shelf life of fresh tortillas

Edible films have emerged as packaging aids to replace synthetic polymers due to their biodegradable nature. The aim of this study was to develop starch-based edible films for application in packaging, to inhibit moisture transfer from the filling to the tortilla, while maintaining physicochemical and organoleptic quality characteristics, and improving shelf life. Twenty-four types of filmogenic solutions were produced by casting from corn, pea, and chestnut starch blended with agar, guar, and potassium alginate, using glycerol as a plasticizer. The films were selected due to its surface properties and water absorption capacity, which allowed selecting the films that best retained moisture. The hydration properties of the selected films allowed to verify that the corn and pea starch films show good resistance to water and microbial development. Microstructural properties showed that the pea starch films exhibit a homogeneous and smooth surface without porosity. Fourier Transform Infrared Micro-Spectroscopy allowed the characterization of the starch films at the molecular level. The mechanical properties of corn and pea starch films were evaluated in tensile strength (21.98–27.5 KPa), elongation at break (59.17–185.96%), and elastic modulus (42.35–17.09 MPa). The results suggest that pea films are more flexible than starch films due to differences in the amylose and amylopectin molecules and molecular masses of the different starches. The sensory analysis concluded that the pea starch film delayed moisture transfer from the filling to the tortilla, maintaining the texture, appearance, and organoleptic characteristics for 6 days, improving the consumption experience of these food products.

Starch-Based Edible Films Properties and Sensory Evaluation for Food Applications

Edible films have emerged as a substitute for synthetic polymers because those are biodegradable, maintain organoleptic quality, and improve the shelf-life of food products. This study, developed starch-based edible films for application in a wrapper to inhibit moisture transfer from tortilla filling while maintaining physicochemical and organoleptic characteristics, increasing the shelf-life. Twenty-four types of filmogenic solutions were produced by casting from corn, pea, and chestnut starch blended with agar, guar, and potassium alginate, using glycerol as a plasticizer. The films were selected due to its surface properties and water absorption capacity, which allowed selecting the films that best retained moisture. The hydration properties of the selected films allowed to verify that the corn and pea starch films show good resistance to water and microbial development. Microstructural properties showed that the pea starch films exhibit a homogeneous and smooth surface without porosity. Fourier Transform Infrared Micro-Spectroscopy allowed the characterization of the starch films at the molecular level. The mechanical properties of corn and pea starch films were evaluated by tensile strength (22.34-27.5 KPa), elongation at break (53.20-185.96 %), and Young's modulus (64.35 -17.09 MPa) had revealed that pea starch is a stronger and more flexible film than corn starch film due to amylose content and molecular weight. The sensory analysis concluded that the pea starch film delayed moisture transfer from the filling to the tortilla, maintaining the texture, appearance, and organoleptic characteristics of the wrapper for 6 days and improving the consumption experience of this food product.

Development and characterization of bilayer films based on pea starch/polylactic acid and use in the cherry tomatoes packaging

Renewable and biodegradable packaging materials are desired for numerous applications. Pea starch (PS) and polylactic acid (PLA) are promising alternatives to petrochemical-based polymers except that their phase separation causes poor mechanical properties. To surmount this problem, PS/PLA films with a double-layer structure were designed. The bilayer films displayed better toughness, thermal stability and barrier capacity over those of PLA films. The incorporation of PLA on a PS layer increased water resistance and tensile strength over those of a monolayer PS film. Weak interfacial adhesion between the PS and PLA layers was revealed by Fourier transform infrared spectroscopy and scanning electron microscopy. The bilayer films reduced weight loss ratio of cherry tomatoes and extended the retention of organic acids and vitamin C. A bilayer architecture represents a promising route to develop packaging materials that display the advantageous properties of each material layer.

Effects of acid hydrolysis on the physicochemical properties of pea starch and its film forming capacity

The effects of acid hydrolysis treatment on the properties of pea starch (PS) and PS-based films by solution casting were investigated. Native pea starch granules were partially hydrolyzed with 2% hydrochloric acid for 0.5, 1.0, 1.5, 2.0, and 2.5 h. Acid hydrolysis treatment lowered the molecular weight of amylopectin from 27.94 × 107 g/mol for native PS to 9.16 × 107 g/mol for the sample of 2.5 h hydrolysis, but had no obvious effect on the molecular weight of amylose. Micrographs of the hydrolysis starch granules exhibited surface erosion and fragmentation. The relative crystallinity slightly increased, whereas the peak, trough, final and setback viscosities decreased during acid hydrolysis. After acid hydrolysis treatment, the tensile strength of the pea starch film significantly increased and reached a maximum of 21.21 MPa with 2.0 h of acid hydrolysis.

Physical, Barrier, and Antioxidant Properties of Pea Starch-Guar Gum Biocomposite Edible Films by Incorporation of Natural Plant Extracts

Active food packaging based on pea starch and guar gum (PSGG) films containing natural antioxidants (NAs) was developed. Four kinds of NAs (epigallocatechin gallate (EGCG), blueberry ash (BBA) fruit extract, macadamia (MAC) peel extract, and banana (BAN) peel extract) were added into the PSGG-based films as antioxidant additive. The effects of these compounds at different amounts on the physical and antioxidant characteristics of the PSGG film were investigated. The antioxidant activity was calculated with three analytical assays: DPPH radical scavenging ability assay, cupric reducing antioxidant capacity (CUPRAC), and ferric reducing activity power (FRAP). EGCG-PSGG films showed higher antioxidant activity, followed by BBA-PSGG, MAC-PSGG, and BAN-PSGG films, at all concentrations (0.75–3 mg/mL) and with all procedures tested. Additionally, the antioxidant activity of films showed a concentration dependency. The results revealed that addition of NAs made the PSGG film darker and less transparent. However, the moisture barrier was significantly improved when NAs were incorporated into the film. The FTIR spectra were examined to determine the interactions between polymers and NAs. The results suggested that incorporation of EGCG, BBA, MAC, and BAN into PSGG films have great potential for use as active food packaging for food preservation.

Mechanical and Physical Properties of Pea Starch Edible Films in the Presence of Glycerol

The mechanical properties and moisture sorption at relative humidity (RH) range of 11–94%, water vapor permeability (WVP), solubility in water and color of the pea starch films as a function of glycerol were examined. The results showed that increasing the concentration of plasticizer resulted in improvement of the tensile strength of the films at RH <43%, the percent elongation as well as the deformation at break at RH <84%. Increasing plasticizer content and RH also resulted in films with lower Young's modulus, lower puncture force, but higher puncture deformation. Furthermore, increasing plasticizer content led to the films with more opaque appearance. Films prepared with 15 and 25% glycerol had lower WVP in comparison with unplasticized film. This study provides information regarding the advantageous or disadvantageous of possible application of pea starch films in food packaging industry. Practical Application Starch edible films have been utilized for packaging technologies and edible coatings. Pea starch has been found to produce the films with improved physical and mechanical properties in comparison with films prepared from other starches due to high amount of amylose. The development of pea starch film with improved functions affects its application. Pea starch edible films may find practical applications in the poultry, meat, seafood, fruit, vegetable, grains and candies industries.

Effects of pH and Salts on Physical and Mechanical Properties of Pea Starch Films.

To identify the significant contribution of intermolecular hydrogen bonds of starch molecules to the film structure formation, pH of film-forming solutions was adjusted and also various salts (NaCl, CaCl2 , CaSO4 , and K2 SO4 ) were mixed into the glycerol-plasticized pea starch film. The film made from pH 7 possessed the highest tensile strength-at-break (2 times) and elastic modulus (4 to 15 times) and the lowest elongation-at-break compared with those of the films made from acid and alkali environments. The pH 7 film also has the highest film density and the lowest total soluble matter. At the level of 0.01 to 0.1 M of CaSO4 and 0.1 M of K2 SO4 in a kilogram of starch, the water solubility of the film increased, while chloride salts slightly lowered the solubility. NaCl and CaSO4 reduced water vapor permeability (WVP), while CaCl2 slightly increased WVP at 0.01 and 0.06 M concentrations, and K2 SO4 significantly increased WVP at 0.03 and 0.15 M. Presence of salts increased tensile strength (5 to 14 times than the control films) and elastic modulus (35 to 180 times) of starch film at 0.01 to 0.03 M of CaSO4 and K2 SO4 . Elongation-at-break increased significantly as salt concentration increases to an optimal level. However, when the concentration exceeded above the optimal level, the E of starch films decreased and showed no significant difference from the control film. Overall, the addition of salts modified physical and mechanical properties of pea starch films more than pH adjustment without any salt addition.

Physicochemical properties of starch nanocomposite films enhanced by self-assembled potato starch nanoparticles

The aim of this research was to enhance the physicochemical properties of pea starch-based nanocomposite films by incorporating with different levels of potato starch nanoparticles (SNPs). The SNPs prepared by self-assembly of short amylose were characterized by SEM. The spherical SNPs with a diameter of 15–30 nm were observed. X-ray diffraction results showed that the SNPs displayed higher relative crystallinity than native starch. It was found that the addition of SNPs to starch films enhanced the mechanical properties. With incorporation of 6% SNPs, the tensile strength of film was increased from 8.8 MPa to 15.0 MPa. The nanocomposite films presented reductions in both water vapor permeability and water solubility. Compared with control film, the melting temperature of the nanocomposite films increased with increasing SNPs content, indicating improved thermal stability. The newly developed pea starch films impregnated with potato SNPs could have potential use in degradable packaging applications.

Water Sorption Isotherm of Pea Starch Edible Films and Prediction Models.

The moisture sorption isotherm of pea starch films prepared with various glycerol contents as plasticizer was investigated at different storage relative humidities (11%–96% RH) and at 5 ± 1, 15 ± 1, 25 ± 1 and 40 ± 1 °C by using gravimetric method. The results showed that the equilibrium moisture content of all films increased substantially above aw = 0.6. Films plasticized with glycerol, under all temperatures and RH conditions (11%–96%), adsorbed more moisture resulting in higher equilibrium moisture contents. Reduction of the temperature enhanced the equilibrium moisture content and monolayer water of the films. The obtained experimental data were fitted to different models including two-parameter equations (Oswin, Henderson, Brunauer–Emmitt–Teller (BET), Flory–Huggins, and Iglesias–Chirife), three-parameter equations Guggenhiem–Anderson–deBoer (GAB), Ferro–Fontan, and Lewicki) and a four-parameter equation (Peleg). The three-parameter Lewicki model was found to be the best-fitted model for representing the experimental data within the studied temperatures and whole range of relative humidities (11%–98%). Addition of glycerol increased the net isosteric heat of moisture sorption of pea starch film. The results provide important information with estimating of stability and functional characteristics of the films in various environments.

Resistance to moist conditions of whey protein isolate and pea starch biodegradable films and low density polyethylene nondegradable films: a comparative study

Biodegradable packaging materials are degraded under the natural environmental conditions. Therefore using them could alleviate the problem of plastics accumulation in nature. For effective replacement of plastics, with biodegradable materials, biodegradable packages should keep their properties under the high relative humidity (RH) conditions. Therefore the objectives of the study were to develop biodegradable packaging material based on whey protein isolate (WPI) and pea starch (PS). To study their mechanical, oxygen barrier and solubility properties under different RHs compared with those of low density polyethylene (LDPE), the most used plastic in packaging. Films of WPI and PS were prepared separately and conditioned at different RH (30-90%) then their properties were studied. At low RHs (<50%), WPI films had 2-3 times lower elongation at break (E or stretchability) than PS and LDPE. Increasing RH to 90% significantly (P<0.01) increased the elongation of PS but not WPI and LDPE films. LDPE and WPI films kept significantly (P<0.01) higher tensile strength (TS) than PS films at high RH (90%). Oxygen permeability (OP) of all films was very low (<0.5 cm3 μm m-2 d-1 kPa-1) below 40% RH but increased for PS films and became significantly (P<0.01) different than that of LDPE and WPI at > 40% RH. Oxygen permeability of WPI and LDPE did not adversely affected by increasing RH to 65%. Furthermore, WPI and LDPE films had lower degree of hydration at 50% and 90% RH and total soluble matter than PS films. These results suggest that WPI could be successfully replacing LDPE in packaging of moist products.

Physical and microstructural properties of biodegradable films based on pea starch and PVA

The effect of storage time on the physical properties of pea starch (PS) and polyvinyl alcohol (PVA) films and their blend was studied to develop biodegradable packaging materials for food applications. To this end, an analysis was performed of the microstructural and physical properties (solubility, moisture content, barrier, mechanical and optical properties) of PS, PVA and PS:PVA films stored for five weeks (25°C–53%RH). Whereas SEM micrographs showed a homogenous appearance for PS films, PVA presented irregularities typical of semi-crystalline structures. Blend films showed a structure which was more similar to PVA films. After 5weeks, the physical properties of PVA films did not change; in the case of PS, however, the elastic modulus and tensile strength increased markedly but the stretchability and gloss significantly decreased, which was associated with water loss in the starch matrix. All the physical properties of blend films remained unchanged throughout time, except the elastic modulus and the tensile strength, which slightly increased. Therefore, the incorporation of PVA into pea starch films improved their physical properties and inhibited the changes that occurred in the starch matrix caused by ageing.

Properties and ageing behaviour of pea starch films as affected by blend with poly(vinyl alcohol)

Pea starch (S) and poly(vinyl alcohol) (PVA) blends with different ratios were produced in order to elucidate the possible advantages of blend films to overcome the common drawbacks of starch films. Starch, poly(vinyl alcohol) and blends (S:PVA ratios of 2:1, 1:1 and 1:2) were obtained by casting and microstructure and thermal behaviour were characterized. Moreover, barrier, mechanical and optical properties were evaluated after 1 and 5 storage weeks at 25 °C and 53% relative humidity in order to study the effect of poly(vinyl alcohol) on the ageing process of starch. The incorporation of PVA into pea starch films implied the formation of interpenetrated networks of both incompatible polymers with partial solubilisation. S-PVA blend films were much more extensible and stable during storage, with improved water barrier properties and reduced water sorption capacity especially when the S:PVA ratio were 1:1 and 1:2. Starch-poly(vinyl alcohol) blend films are environmentally friendly, low cost materials, with good functional properties.

Mechanical, barrier and morphological properties of starch nanocrystals-reinforced pea starch films.

To characterize the pea starch films reinforced with waxy maize starch nanocrystals, the mechanical, water vapor barrier and morphological properties of the composite films were investigated. The addition of starch nanocrystals increased the tensile strength of the composite films, and the value of tensile strength of the composite films was highest when starch nanocrystals content was 5% (w/w). The moisture content (%), water vapor permeability, and water-vapor transmission rate of the composite films significantly decreased as starch nanocrystals content increased. When their starch nanocrystals content was 1-5%, the starch nanocrystals dispersed homogeneously in the composite films, resulting in a relatively smooth and compact film surface and better thermal stability. However, when starch nanocrystals content was more than 7%, the starch nanocrystals began to aggregate, which resulted in the surface of the composite films developing a longitudinal fibrous structure.

Effect of amylose:amylopectin ratio and rice bran addition on starch films properties

The influence of the amylose:amylopectin ratio on the properties of pea, potato and cassava starch films and the effect of the incorporation of rice bran of two different particle sizes were studied. The structural, mechanical, optical and barrier properties of the films were analyzed after 1 and 5 weeks. The high content of amylose gave rise to stiffer, more resistant to fracture, but less stretchable films, with lower oxygen permeability and greater water binding capacity. Although no changes in the water vapour permeability values of the films were observed during storage, their oxygen permeability decreased. Throughout storage, films became stiffer, more resistant to break, but less stretchable. Rice bran with the smallest particles improved the elastic modulus of the films, especially in high amylose content films, but reduced the film stretchability and its barrier properties, due to the enhancement of the water binding capacity and the introduction of discontinuities.

Lysozyme release from isolate pea protein and starch based films and their antimicrobial properties

The objective of the current research was to analyze the effects of the pea protein and corn starch films as well as the temperature influence (10 and 25°C) on the release of lysozyme to a food simulant (agar gel). Lysozyme concentration at different depths of food simulant was measured, as a function of diffusion time, through its enzyme activity. In both polymer matrices, a loss of lysozyme activity was observed after film formation. Diffusion of lysozyme was enhanced when temperature increased, mainly when pea protein films were tested. A higher retention of lysozyme in the film starch matrix was significantly detected which could be attributed to the different hydration degree of the film in contact with the agar medium and the different interactions between the enzyme and the film polymer chains. The antimicrobial effectiveness of pea protein and starch films containing lysozyme (0, 50, 75 and 100mg lysozyme/g hydrocolloid), against Listeria monocytogenes was proved. At 10°C, both matrices were effective against the pathogen. At 25°C, the effectiveness of films significantly decreased and pea protein films showed the best antimicrobial activity.

Mechanical, barrier and morphological properties of pea starch and peanut protein isolate blend films

Mechanical, barrier and morphological properties of edible films based on blends of Pea starch (PS) and Peanut protein isolate (PPI) plasticized with glycerol (30%, w/w) were investigated. As PPI ratio in PS/PPI blends increased, the thickness of films decreased, the opacity slightly elevated and color intensified. The addition of PPI to the PS film significantly reduced tensile strength from 5.44MPa to 3.06MPa, but increased elongation from 28.56% to 98.12% with the incorporation of PPI into PS at 50% level. Film solubility value fell from 22.31% to 9.78% upon the incorporation of PPI ranged from 0 to 50% level. When PPI was added into PS film at 40% level, the WVP and WVTR of the films markedly dropped from 11.18% to 4.19% and 6.16 to 1.95%, respectively. Scanning electron microscopy (SEM) of the surface of films showed that many swollen starch granules were presented in the 100% PS film, while 100% PPI film was observed to have rougher surfaces with presence of pores or cavities. The PS/PPI blend films upon the incorporation of PPI at 20% and 50% level were not homogeneous. However, the smoother film surface was observed in PS/PPI blend films with the addition of PPI at 40% level. SEM image of the cross-sections of the films revealed that the 100% PS film showed a uniform and compact matrix without disruption, and pore formation and 100% PPI film displayed a smooth structure. Rougher and flexible network was shown in blend film with the addition of PPI reaching 40% level.

Mechanical properties of pea starch films associated with xanthan gum and glycerol

AbstractThe aim of this study was to evaluate the effect of the addition of xanthan gum and glycerol to the starch of green pea with high content of AM (cv. Utrillo) in the preparation of films and their physical characteristics. Filmogenic solution (FS) with different levels of pea starch (3, 4, and 5%), xanthan gum (0, 0.05, and 0.1%), and glycerol (glycerol–starch ratio of 1:5 w/w) were studied. The FS was obtained by boiling (5 min), followed by autoclaving for 1 h at 120°C. The films were prepared by casting. Films prepared only with pea starch were mechanically resistant when compared to other films, prepared with corn, cassava, rice, and even other pea cultivars (yellow, commercial). The tensile strength of these films is comparable to synthetic films prepared with high‐density polyethylene and linear low‐density polyethylene. However, they are films of low elasticity when compared to other films, such as rice starch films, and especially when compared to polyethylene films. The increased concentration of starch in the solution increased the puncture force. The increased concentration of glycerol slightly decreased the film crystallinity and interfered in the mechanical properties of the films, causing reduction of the maximum values of tensile strength, strain at break, and puncture force. The plasticizer also caused an increase of elongation at break. Xanthan gum was important to formation of films; however, it did not affect their mechanical properties.

Crystallization of high-amylose starch by the addition of plasticizers at low and intermediate concentrations.

The antiplasticization effect of plasticizers (that is, polyols and monosaccharides) in starch films was investigated. Pea starch films were plasticized by various polyols and monosaccharides at the levels of 0% to 25% (w/w, plasticizer/starch). After 14 d of storage at 50% relative humidity, the crystallinity of pea starch films increased with increasing concentration of plasticizers from 0% to 20%. Accordingly, moisture content, water vapor permeability, oxygen permeability, and elongation decreased with increasing plasticizer concentration from 0% to 20%, showing the antiplasticization effect. The addition of plasticizers above 20% reduced the crystallinity of starch films, consequently showing the plasticization effect. The results showed that the addition of the plasticizers facilitated the crystallization of the polymer chains through the antiplasticization phenomenon at the concentration range below 15%. Above 20%, plasticizers performed the conventional plasticization effect. Each plasticizer had different critical concentration where the antiplasticization was converted to plasticization.