Food Technology
Elham Safaei; Hannan Lashkari; Sara Ansari; Alireza Shirazinejad
Abstract
Introduction Manufacturers are trying to replace plastic materials in the food packaging industry with biodegradable and edible films. Biodegradable edible films and coatings are mainly made from carbohydrates, lipids and proteins and their mixtures. In recent decades, various carbohydrates from ...
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Introduction Manufacturers are trying to replace plastic materials in the food packaging industry with biodegradable and edible films. Biodegradable edible films and coatings are mainly made from carbohydrates, lipids and proteins and their mixtures. In recent decades, various carbohydrates from plant sources have been investigated and introduced as new compounds for the preparation of these films. Flaxseed gum is a white to cream-colored powder that dissolves in water and produces a gel, and is a desirable compound for forming films and coatings. Recently, through the integration of reinforcements or fillers with at least one nanometer dimension in the substrate of one or more natural biopolymers, the physicochemical, mechanical, optical, thermal and barrier properties of pure biofilms have been improved. The use of cellulose nanoparticles in biofilms as a reinforcing agent for polymer materials leads to the creation of composite films with better quality characteristics and leads to the creation of functionalization activities in film production. Therefore, the aim of this research was to produce and characterize edible and biodegradable film based on the combination of flaxseed gum and cellulose nanocrystals. Materials and Methods Cellulose nanocrystals (Degree of crystallinity: 42% and average particle size: 58 nm) were extracted from cotton linters. Glycerol and other chemicals used for this research were obtained from Merck, Germany. Flaxseeds were purchased from the local market of Shiraz (Iran). Bionanocomposite films were prepared from different ratios (0:100, 30:70, 50:50, 70:30 and 100:0) of flaxseed mucilage (2% w/v) and cellulose nanocrystal (6% w/v) solutions. The prepared solutions were poured on a petri dish with a diameter of 15 cm and dried in an oven at 80°C for 4 hours. Their physical, color and mechanical properties were investigated and the best ratio was selected for the preparation of bionanocomposite film. The produced films were subjected to different analysis to determine thickness, solubility, water absorption capacity, permeability to water vapor, tensile strength, elongation at break point, and colorimetry. The microstructure of the produced film was studied using a scanning electron microscopy (SEM).The average data were analyzed by analysis of variance in a completely randomized design using SPSS 22.0 software. Differences between treatments were expressed in Duncan's multiple range test at the 95% probability level (p<0.05) and the corresponding graphs were drawn with Excel 2013. Results and Discussion The results of the film thickness test showed that the film containing 100% mucilage has the lowest thickness and with the addition of cellulose nanocrystals, the thickness increased significantly (p<0.05). The results of the water solubility and water absorption capacity of the film samples showed that the addition of cellulose nanocrystals to the flaxseed mucilage film initially led to a significant decrease in the water solubility and water absorption capacity (p<0.05), so that the lowest level ofthese two physical parameters were obtained in the film containing the combination of 70% flaxseed mucilage and 30% cellulose nanocrystal, and then with the increase of cellulose nanocrystals, an increase in water solubility and water absorption capacity of the films was observed. Nanocrystal cellulose at low levels (30%) acted as a filler and was uniformly dispersed in the network of the film and by filling the empty pores of the biopolymer film based on flaxseed mucilage, it caused the transfer of water vapor more complicated and reduced the permeability to water vapor. However, its higher amount increased the permeability of the film to water vapor.The results showed that by adding cellulose nanocrystal to the film based on flaxseed mucilage and increasing its amount, the brightness of the films decreased and the intensity of redness, yellowness and turbidity of the films increased significantly (p<0.05). By combining flaxseed mucilage and cellulose nanocrystals in a ratio of 30:70, the best film was produced in terms of mechanical strength and stability against moisture and water vapor. The SEM image of this film showed a smooth, even surface and a uniform distribution of cellulose nanocrystals in the film network. Conclusion The results finally showed that the combination of flaxseed mucilage and cellulose nanocrystals in a ratio of 30:70 was able to produce a biodegradable and edible film with favorable structural and barrier properties. The characteristics of this film include; thickness (0.313mm), solubility (53.42%), water absorption capacity (44.44%), permeability to water vapor (0.350 g.m-1s-1Pa-1 × 10 -10), tensile strength (0.973 MPa), elongation at break point (30.52%) were obtained. The colorimetric indices L*, a*, b* and turbidity were determined as 79.73, 1.95, 3.48 and 1.335 mm-1 respectively. Acknowledgement The authors would like to express their sincere gratitude to Islamic Azad University, Sarvestan Branch.
Lida Shashavani Mojarrad; Ali Rafe
Abstract
Textural, thermal and microstructural properties of single component gels and binary composite gels (BCG) of high amylose corn starch (Hylon VII) mixed with wheat flour at different wheat flour/Hylon VII (WF/H) ratios (95:5, 90:10 and 85:15) and temperatures (100, 121 and 135ºC) were investigated. ...
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Textural, thermal and microstructural properties of single component gels and binary composite gels (BCG) of high amylose corn starch (Hylon VII) mixed with wheat flour at different wheat flour/Hylon VII (WF/H) ratios (95:5, 90:10 and 85:15) and temperatures (100, 121 and 135ºC) were investigated. The visual appearance showed that as Hylon VII was increased in BCG, the stronger gel was achieved. Textural results confirmed by increasing Hylon VII, the firmness was increased, but the springiness, cohesiveness and adhesiveness were reduced. Moreover, the BCG at high temperatures showed the higher level of Hylon VII, the higher water solubility index would be achieved. The gelatinization enthalpy (ΔH) and peak gelatinization temperature (Tp) increased by improving the content of amylose in BCG. Hylon VII showed the lowest peak viscosity and the BCG gel containing high amount of Hylon VII indicated a reduction in the paste viscosity. The differences in the microstructure of WF and HylonVII gels were also reflected the pasting properties of the gels. Consequently, BCG of WF/H develops the stronger gel which can withstand at high thermal processing such as retort to improve the shelf-life of the final product.
Vahid Alizade; Hassan Barzegar; Behzad Nasehi; Vahid Samavati
Abstract
Introduction: The environmental effect of synthetic plastic wastes is of increasing global concern. There is an urgent need to develop and apply renewable biopolymer materials. Development of edible and biodegradable films can help solving the waste disposal problem by partially replacing synthetic plastics ...
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Introduction: The environmental effect of synthetic plastic wastes is of increasing global concern. There is an urgent need to develop and apply renewable biopolymer materials. Development of edible and biodegradable films can help solving the waste disposal problem by partially replacing synthetic plastics (Martins et al., 2012). Chitosan; a linear polysaccharide composed of (1, 4)-linked 2-amino-deoxy-b-d-glucan, is a deacetylated (to varying degrees) product of chitin, which is the second most abundant polymer found in nature after cellulose. It has been proved to be biodegradable, biofunctional, biocompatible, nontoxic and have strong antifungal and antimicrobial properties (Aider, 2010). Thus, this work was undertaken to investigate the physical, optical, barrier, mechanical, microstructural, and antimicrobial properties of chitosan films incorporated with PEO, to examine its potential applications as a packaging material.
Materials & method: The films were prepared according to the solvent casting technique reported by (Abdollahi et al., 2012) with some modifications. Tensile strenght (TS) and elongation at break (E) of the films were measured with texture analyzer according to Barzegar et al. (2014) method. Equilibrated film strips (at 53% RH for 48 h) were fixed between the grips with an initial separation of 50 mm and the cross-head speed was set at 50 mm/min. TS was calculated by dividing the maximum force by the initial area of the film and E% was calculated through dividing the extension at the moment of specimen rupture by the initial gauge length and multiplying by 100. The WVP of the films was determined at according to the Shojaee-Aliabadi et al. (2013). The test cups containing anhydrous calcium chloride (0% RH) were sealed by the test films, then were placed inside a desiccator containing sodium-chloride-saturated solution (75% RH). Weight gain of the cups along time were recorded periodically and plotted as a function of time. Antimicrobial properties of the films were assessed using the disc-diffusion method according to Dashipour et al. (2015). Four gram-positive or gram-negative bacteria, including B. cereus, S. aureus, E. coli and S. typhimurium were used for testing.
Results and discussions: The influence of PEO incorporation on thickness, TS, EAB, WVP and water solubility of films can be seen in Table 1. The incorporation of PEO into the film-forming dispersion led to an increase in the thickness of the films, which varied between 0.131 mm and 0.185 mm. It could be due to the entrapment of PEO micro droplets by the polymer matrix (Dashipour et al. 2015). By increasing PEO concentration from 0.5 to 2 % in the film solutions, WS decreased markedly from 22.46 to 16.15 (P < 0.05). This behavior can be explained by the cross-linking effects of PEO components to esters and/or amide groups. Cross-linking in the chitosan film leads to a polymer with lower water solubility, which is useful when product integrity and water resistance are intended (Hosseini et al., 2009).
Table 1. Physical and mechanical properties of chitosan films.
PEO (% v/v) Thickness (mm)
Solubility in water (%) WVP
(g s-1 m-1 Pa-1 × 10-10) TS
(MPa) EAB
(%)
0.0 0.131 ± 0.01d 22.46 ± 0.73a 1.04 ± 0.05c 21.22 ± 1.97a 49.05 ± 1.63c
0.5 0.153± 0.01c 21.19 ± 1.22a 1.12 ± 0.06c 20.09 ± 1.40a 50.36 ± 2.98c
1 0.167 ± 0.01b 18.47 ± 0.53b 1.35 ± 0.09b 17.04 ± 1.26b 55.25 ± 2.95b
2 0.185 ± 0.01a 16.15 ± 0.54c 1.73 ± 0.09a 13.23 ± 1.35c 59.37 ± 2.49a
The incorporation of PEO into chitosan-based films leads to an increase in WVP values from 1.04 to 1.73 g s-1 m-1 Pa-1 × 10-10. A similar trend has been found by Bonilla et al., (2011) in chitosan-based films incorporated with thyme essential oil. The structural discontinuities induced in the polymer network by the addition of PEO could be the reason for the lowest resistance to breakage of the emulsified films. These discontinuities greatly reduced the film cohesion and mechanical resistance (Bonilla et al., 2012). Conversely, the EAB value of the films increased significantly (P < 0.05) from 49.05% to 59.37%, because the essential oil acted as a plasticizer even at small concentrations and enhanced the flexibility of the polymer chains.
The effects of PEO on the antimicrobial properties of the chitosan films are shown in Table 2. The films containing 1% PEO showed a certain inhibitory effect against B. cereus and S. aureus but no inhibition against S. typhimurium and E. coli. As the concentration of PEO increased, the zone of inhibition also increased significantly (P < 0.05). The films containing 2% PEO were effective against all studied bacteria and a greater inhibitory power was observed on S. aureus with the zone area of 49.67 mm2. The inhibitory effect of PEO is due to the two monoterpene hydrocarbons, α-pinene, and β-pinene (Barrero et al., 2005).
Table2. Antimicrobial activity of chitosan films.
PEO (% v/v) Inhibition zone (mm2)
S. aureus B. cereus E. coli S. typhimurium
0.0 0.00c 0.00c 0.00b 0.00b
0.5 0.00c 0.00c 0.00b 0.00b
1 22.58 ± 1.76b 15.63 ± 0.63b 0.00b 0.00b
2 49.67 ± 3.02a 41.96 ± 1.40a 21.12 ± 1.87a 12.49 ± 1.57a
Conclusion: The results obtained in this study showed that the chitosan films incorporated with PEO has a good potential to being empolyed as an active film to preserve food products. Addition of PEO decreased water solubility and tensile strength, while increased the thickness, WVP and percent elongation of the films. Overall, this study demonstrates that PEO-containing films present a good potential for their application in the food industry.
Igor Smykov; Anna Gnezdilova; Yuliya Vinogradova; Valentina Popova
Abstract
These work deals with the study of changes in the microstructure of the sweetened condensed milk with sugar substitution for starch syrup during its long storage period. The research has been carried out with the transmission electron microscope. The authors have analyzed the microstructure of the condensed ...
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These work deals with the study of changes in the microstructure of the sweetened condensed milk with sugar substitution for starch syrup during its long storage period. The research has been carried out with the transmission electron microscope. The authors have analyzed the microstructure of the condensed milk with sugar and the microstructure of the condensed milk with 40% and 100% sugar substitution for the starch syrup. It is established that filamentous bridges are formed between the casein micelles in the microstructure of the condensed milk with the partial sugar substitution for the starch syrup. These bridges are pseudo-polymers, formed by glucose monomers. During the long-storage period the number and density of these bridges increase, influencing, consequently, the organoleptic and rheological properties of the condensed milk. The studies have shown that there is a critical concentration of the starch syrup in the condensed milk, which limits the syrup use in the manufacture of the product.
Seyed Amir Tavakoli Lahijani; Fakhri Shahidi; Mehdi Varidi; Mohebbat Mohebbi
Abstract
Spirulina platensis is a blue-green microalga with unique nutrient content and several therapeutic aspects which has been used for fortification of different foods. In this study, the effect of Spirulina platensis powder in different levels (0, 0.5, 1 and 2 percent), added in two stages (before pasteurization ...
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Spirulina platensis is a blue-green microalga with unique nutrient content and several therapeutic aspects which has been used for fortification of different foods. In this study, the effect of Spirulina platensis powder in different levels (0, 0.5, 1 and 2 percent), added in two stages (before pasteurization and at same time with starter culture) was studied on the microstructure and acidification characteristics of yogurt during fermentation time. The results showed that different levels of Spirulina biomass had significant effect on acidification kinetics parameters of yogurt samples (p
