: Puree prepared from over‐ripe peeled bananas was used as raw material for films processing in a laboratory padder. Pectin and glycerol as plasticizer were added in small concentrations and ...chitosan nanoparticles (88.79 ± 0.42 nm medium size) incorporated at 0.2% (dry weight basis) as reinforcement material. The mechanical properties, water vapor transmission, thermal stability, and scanning electron microscopy of fractured film surfaces were characterized. Both pectin and glycerol demonstrated an important role in promoting elongation and film handability as was expected. The incorporation of nanoparticles promoted noticeable improvement of the mechanical properties and acted in reducing the water vapor permeation rate, by 21% for films processed with pectin and up to 38% for films processed without pectin, when compared to the control (puree films with no pectin and nanoparticles additions). Microscopic observation revealed a denser matrix when nanoparticles are incorporated into the films.
Practical Application: The development of films from fruit purees head to a new strategy for plastic processing from natural resources. The over‐ripe or even waste banana can be adequately prepared for batch films processed with reasonable mechanical and barrier properties, suitable for applications in the food segment. The addition of small fractions of chitosan nanoparticles, form nanocomposites enhancing mechanical and thermal stability broadening potential film applications.
Recently the squid pens, a rich source of β-chitin containing low contents of inorganic compounds, have become available in considerable amounts as a refuse of the fishery industries in Brazil. Thus, ...the aim of this work is to use squid pens from
Loligo sanpaulensis and
Loligo plei, species found in the Brazilian coast, as the raw material for the extraction of β-chitin. The squid pens were submitted to the usual sequence of treatments used for chitin extraction – demineralization and deproteinization – but due to its low content of inorganic compounds a two-step alkaline treatment was enough to produce β-chitin with low contents of ash (⩽0.7%). Indeed, the low contents of ash and metals, such as Ca (⩽10.4
ppm), Mg (⩽2.5
ppm), Mn (⩽3.1
ppm) and Fe (⩽1.8
ppm), are lower than those reported in most of the papers found in the literature. Also, the β-chitin extracted by employing only the alkaline treatment was more acetylated than the other samples prepared in this work. Regardless of the treatment employed for the extraction of the β-chitin from the squid pens, its infrared spectra and X-ray diffraction pattern presented only minor differences, however they were clearly distinguished from commercial α-chitin.
•Enzymatic and acid hydrolysis were used to produce soybean straw nanocellulose.•SPI films were reinforced with nanocellulose produced by enzymatic/acid hydrolysis.•CNFs presented a greater aspect ...ratio and thermal stability and lower crystallinity.•CNFs as reinforcing filler yielded more elongable nanocomposites with lower WVP.•Both CNFs and CNCs improved the mechanical resistance of SPI films.
This work is a comparative study of the application of mercerized soybean straw (MSS) and nanocellulose produced by acid (CNCs) or enzymatic hydrolysis (CNFs) as reinforcing fillers in soy protein isolate (SPI) films. CNCs presented average dimensions of about 10 nm-thick and 300 nm-long with a crystallinity index of 57%, whereas CNFs have similar diameters, though with greater lengths (>1 μm), lower crystallinity index (50%) and greater thermal stability. Incorporation of 5% of CNCs and CNFs (g/100 g of SPI) improved the SPI film tensile strength by 38 and 48% respectively, and decreased the SPI film elongation at break when compared to control films. The SPI-CNC films showed the lowest values for solubility, probably due to their higher crystallinity (63%). On the other hand, the water vapor permeability was solely reduced with CNF addition, which can be attributed to their higher aspect ratio (length/diameter) and a better incorporation into the protein matrix.
A novel method for obtaining
N,
N,
N-trimethylchitosan has been developed using dimethylsulfate as the methylant agent. Dimethylsulfate is not only more efficient but is less expensive than other ...commonly used agents. The resultant chitosan derivatives were characterized by FTIR,
1H NMR, CP-MAS
13C NMR, and a capillary viscometer. Films were processed by casting and then hydrophilic changes were assessed by water contact angle measurements. The highest degree of substitution (
DQ
¯
=
52.5
%
) was obtained after a 6
h long-term reaction at room temperature. The use of higher temperatures helped to provoke polymeric thermal degradation and favor O-methylation over a
N-methylation reaction.
Absorbance, as measured at 620nm, as a function of chitosan and TMC concentration added in the medium with E. coli, according to turbidity method after 12h interaction.
Chitosan is largely known for ...its activity against a wide range of microorganisms, in which the most acceptable antimicrobial mechanism is found to include the presence of charged groups in the polymer backbone and their ionic interactions with bacteria wall constituents. This interaction suggests the occurrence of a hydrolysis of the peptidoglycans in the microorganism wall, provoking the leakage of intracellular electrolytes, leading the microorganism to death. The charges present in chitosan chains are generated by protonation of amino groups when in acid medium or they may be introduced via structural modification. This latter can be achieved by a methylation reaction resulting in a quaternized derivative with a higher polymeric charge density. Since the charges in this derivative are permanents, it is expected a most efficient antimicrobial activity. Hence, in the present study, commercial chitosan underwent quaternization processes and both (mother polymer and derivative) were evaluated, in gel form, against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative), as model bacteria. The results, as acquired from turbidity measurements, differ between materials with an expressive reduction on the Gram-positive microorganism (S. aureus) growth, while E. coli (Gram-negative) strain was less sensitive to both polymers. Additionally, the antibacterial effectiveness of chitosan was strongly dependent on the concentration, what is discussed in terms of spatial polymer conformation.
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•hUCM-MSC culture in Wave-Induced Motion Bioreactor was performed for the first time.•A new Cellbag design was proposed to improve cell growth.•The new Cellbag design inhibited the ...formation of dune-like deposits.•Expansion factors from 11.6 to 25.6 fold were achieved with the Wave-Induced Motion Bioreactor using the new Cellbag design.
Mesenchymal Stromal Cells (MSCs) are considered a viable option for the treatment of several diseases in different medical areas. MSCs are present in small proportions in tissues, thus making an in vitro expansion necessary in accordance with the cGMP. For this purpose, the disposable Wave-Induced Motion Bioreactor (WIMB) is a promising alternative for MSC expansion in a safe and low shear environment. However, wave motion leads to the formation of aggregate deposits (microcarriers and cells) on the Cellbag plastic, impairing the MSC proliferation. In this study, a modification in the Cellbag design was proposed and tested in order to overcome this limitation. Human Umbilical Cord Matrix derived Mesenchymal Stromal Cells (hUCM-MSCs) were expanded in WIMB using Cultispher-S microcarriers and α-MEM medium. Two approaches were evaluated for hUCM-MSCs culture in the new Cellbag design: 1) adhesion phase in spinner and expansion in the WIMB (Expansion Factors: 5.8–8.0 fold) and 2) adhesion and expansion phases in the WIMB (Expansion Factors: 11.6–25.6 fold), both with absence of the most damaging particle deposits. These results showed that the use of WIMB with the Cellbag design modification have good potential for hUCM-MSCs expansion, while maintaining cell quality attributes.
Carboxymethylcellulose (CMC) salts in different counter-ion forms were obtained and characterized by FTIR, CP-MAS
13C NMR and EDX spectroscopies. Additionally, thermogravimetry (TG) was used to ...evaluate the degree of humidity and the thermal stability. In general, CMC samples having Li
+, Na
+ and K
+ as counter-ions showed a high hydrophilic character, absorbing more than 50% in weight of water, while for CMC having Mg
2+, Ca
2+, Ba
2+ and others cations the hydrophilic character was lower than the former, absorbing less than 30% of water. All of the CMC salts showed lower thermal stability than their cellulose parent. Typical values of
T
m, in °C, and
E
a, in kJ
mol
−1, were for cellulose:
T
m
=
349.11,
E
a
=
178.8
±
8.4; CMCK:
T
m
=
283.61,
E
a
=
152.9
±
1.0
kJ
mol
−1; CMCCa:
T
m
=
305.67,
E
a
=
167.2
±
5.2
kJ
mol
−1. Different kinetic models were found for the CMC salts as Šesták–Berggren, reaction order and Johnson–Mehl–Avrami.
•Chemical treatments increased the cellulose content, crystallinity, and thermal stability of soybean straw.•Alkali treatment produced a mixture of polymorphs of cellulose I and II.•Addition of ...chemically treated fibers improved the mechanical resistance of SPI film.•H2O2 bleaching provided more effective delignification.•Soybean straw treated with H2O2 yielded less soluble composite film.
This work investigated changes in the chemical composition and structure of soybean straw (SS) treated with alkali (NaOH 5% and 17.5%) and bleached with hydrogen peroxide (H2O2) or sodium hypochlorite (NaOCl). Removal of the amorphous constituents increased the degree of crystallinity and the content of cellulose fibers particularly after reaction with high concentrations of alkali. Treatment with NaOH 17.5% contributed to the allomorph transition from cellulose I to II regardless of the bleaching agent, but H2O2 as bleaching agent promoted more effective delignification. This work also evaluated the potential use of treated and non-treated SS as reinforcement filler in soy protein isolate film (SPI). Films added with treated SS presented higher mechanical resistance, lower elongation at break, and lower solubility in water. Addition of non-treated SS did not affect the properties of the SPI film significantly. The low solubility and the reasonable water vapor permeability of the composite films make them suitable packaging materials for fresh fruit and vegetables.
Active food packaging systems promote better food quality and/or stability, such as by releasing antimicrobial agents into food. Advantages of adding antimicrobials to the packaging material instead ...of into the bulk food include controlled diffusion, reduced antimicrobial contents, and improved cost effectiveness. Nanostructured antimicrobials are especially effective due to their high specific surface area. The present review is focused on recent advances and findings on the main nanostructured antimicrobial packaging systems for food packaging purposes. Several kinds of nanostructures, including both inorganic particles and organic structures, have been proven effective antimicrobials by different mechanisms of action and with different application scopes. Moreover, there are systems containing nanocarriers to protect antimicrobials and deliver them in a controlled fashion. On the other hand, scientific data about migration of nanostructures onto food and their toxicity are still limited, requiring special attention from researchers and regulation sectors.
The latest and most relevant research outputs on active food packaging comprising nanostructured antimicrobial agents are summarized. Although its approach is concise, this review is rather comprehensive in content by addressing a range of nano‐sized inorganic particles, organic structures, and carrier systems that have been demonstrated to deplete the development of pathogenic and spoilage microorganisms in food matrices. This article is part of an AFOB (Asian Federation of Biotechnology) Special issue. To learn more about the AFOB visit www.afob.org.
Summary
Pure zein films are known to be very hydrophobic, but are inappropriate for edible coating applications because of their brittle nature. In an attempt to improve the flexibility of these ...coatings, the influence of low concentrations of oleic acid (OA) as a plasticiser on mechanical, topographical and wetting properties of zein thin films was evaluated. Films were first obtained by casting from aqueous ethanol solutions with 4.0% in mass of zein and additions of 0%; 0.25%; 0.50%; and 1.0% (w/w) of OA. The results indicate an improvement in mechanical properties with increasing plasticiser leading to a reduction in the elastic modulus. An increase in the elongation at break has been observed, but with minor influence on tensile strength. All plasticised zein films have similar initial contact angle (approximately 69°) with a time‐dependent receding drop behaviour. An increase in plasticiser concentration increases film’s affinity towards water. As measured by atomic force microscopy, a consistent linear relation (R2 = 0.991) was estimated between film composition and surface adhesion and consequently on the hydrophilicity. Surface topography also varied with plasticiser addition, becoming smoother as the OA concentration increases. When tested as an edible coating on pears (Pyrus communis L.), a formulation with 0.25% wt of plasticiser achieved the best results in preserving the pear mass as measured during the evaluated storage time (12 days) at room temperature. A 0.5% concentration of plasticiser had no influence and higher amounts resulted in a reduction in fruit protection.
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