Ioannis Arvanitoyannis

Chitosan and gelatin based edible films: state diagrams, mechanical and permeation properties

Films of chitosan and gelatin were prepared by casting their aqueous solutions (pH≈4.0) at 60°C and evaporating at 22 or 60°C (low- and high-temperature methods, respectively). The physical (thermal, mechanical and gas/water permeation) properties of these composite films, plasticized with water or polyols, were studied. An increase in the total plasticizer content resulted in a considerable decrease of elasticity modulus and tensile strength (up to 50% of the original values when 30% plasticizer was added), whereas the percentage elongation increased (up to 150% compared to the original values). The low-temperature preparation method led to the development of a higher percentage renaturation (crystallinity) of gelatin which resulted in a decrease, by one or two orders of magnitude, of CO2 and O2 permeability in the chitosan/gelatin blends. An increase in the total plasticizer content (water, polyols) of these blends was found to be proportional to an increase in their gas permeability.

Edible films made from gelatin, soluble starch and polyols, Part 3

The thermal and mechanical properties of edible films based on blends of gelatin with soluble starch plasticized with water, glycerol or sugars were investigated. Two different methods, known as ‘the high temperature’ and ‘the low temperature’ methods, consisting of casting aqueous solutions of blends at 60 and 20 °C, respectively, were employed for the preparation of films. With increasing water, glycerol or sorbitol content, a drop of elasticity modulus and tensile strength (up to 50% of the original values for 30% plasticizer) was observed. The tensile strength and percentage elongation increased with high gelatin contents (> 20% ww). The development of a higher percentage renaturation of gelatin (reaching 70% for 5% water content) by the ‘low temperature’ method caused a reduction in gas and water permeabilities. The former decreased by one or two orders of magnitude for O2 and CO2, respectively. The semi-empirical model for calculation of gas permeability and the semi empirical equations for upper and lower limits of tensile moduli of composites were applied with limited success and the obtained values were compared to those experimentally determined.

Application of quality control methods for assessing wine authenticity: Use of multivariate analysis (chemometrics)

Determination of food authenticity is one of the most crucial issues in food quality control and safety. The introduction of new sophisticated techniques, in conjunction with greater consumer demands and expectation for safer products, gives a tremendous impetus to food quality assurance. Wine adulteration, mainly in terms of varieties and regions of origin (geographical), has been very widespread. Therefore, apart from novel experimental techniques, the need emerged for a more comprehensive statistical data analysis. Multivariate analysis comprising principal component analysis (PCA), discriminant analysis (DA), canonical analysis (CA), cluster analysis (CLA), has, in most cases, been effectively employed in wine differentiation and classification according to geographical origin.

Edible films made from hydroxypropyl starch and gelatin and plasticized by polyols and water

Two methods, known as the low and the high temperature methods, which consist of casting aqueous solutions of hydroxypropyl starch and gelatin at 20 and 60°C, respectively, were employed for film preparation. The physical (thermal, mechanical and gas/water permeation) properties of these composite films, plasticized with water or polyols, were studied. An increase in the total plasticizer content resulted in a considerable decrease in elasticity modulus and tensile strength (up to 60% of the original values when 25% plasticizer was added), whereas the percentage elongation increased (up to 200% compared to the original values). The low temperature method led to the development of higher percentage renaturation (crystallinity) of gelatin which resulted in a decrease, by one or two magnitude orders, of CO2 and O2 permeability in the hydroxypropyl starch/gelatin blends. An increase in the total plasticizer content (water, polyols) of these blends was found to be proportional to an increase in their gas permeability.

Physical properties of polyol-plasticized edible films made from sodium caseinate and soluble starch blends

Abstract Aqueous blends of sodium caseinate and soluble starch, plasticized with polyols, were prepared by casting or by extrusion and hot pressing. The mechanical, thermal, gas and water permeation properties of these blends were studied after their conditioning at various relative humidities. With increasing plasticizer (water, polyols) content there was a progressive decrease of Tg of the blends. The plasticized blends also showed increased percentage elongation, whereas their flexural modulus and tensile strength exhibited a substantial drop. The gas permeability-temperature plots revealed Arrhenius-type relationships with an inflection in the glass transition temperature region.

Edible films made from sodium casemate, starches, sugars or glycerol. Part 1

Abstract The physical properties of edible films, based on blends of sodium caseinate with starches of different origin (corn and wheat) plasticized with water, glycerol or sugars, were studied. An increase in water or sugar/glycerol content resulted in a considerable decrease in the modulus of elasticity and in the tensile strength of films. The tensile strength and the water vapor permeability decreased with an increase in sodium casemate contents (> 10%w/w). The development of crystallinity caused a reduction in gas and water permeabilities. Semi-empirical models for calculation of gas permeability and tensile strength and tensile moduli were applied with limited success and the obtained values were compared to those experimentally determined.

Edible films made from natural resources ; microcrystalline cellulose (MCC), methylcellulose (MC) and corn starch and polyols - Part 2

Aqueous blends of microcrystalline cellulose (MCC) or methyl cellulose (MC) and corn starch with or without polyols were extruded, hot pressed and studied, after their conditioning at different relative humidities, in terms of their thermal, mechanical and water and gas permeability properties. An increase in water or polyol content showed a considerable increase in percentage elongation but also a decrease in the tensile strength of films. The presence of high cellulose contents increased the tensile strength and decreased the water vapour transmission of films. The development of crystallinity with time resulted in a decrease of both gas and water permeability. Several semiempirical models for calculation of gas permeability and tensile strength and tensile and flexural moduli were applied. The obtained values were compared to those experimentally determined and with the ones reported in the literature. On several occasions, quite significant discrepancies were found which were attributed to differences in molecular weight, percentage crystallinity and polymorphism.

Physical properties of polyol-plasticized edible blends made of methyl cellulose and soluble starch

Abstract Aqueous blends of methyl cellulose and soluble starch, plasticized with glycerol or sugars, were prepared by casting, or by extrusion and hot pressing. The mechanical (tensile and flexural mode), thermal (differential scanning calorimetry) and gas and water permeation properties of these blends were investigated, after their conditioning at various relative humidities. The observed T g depression for these polymer blends was proportional to the plasticizer content (water, glycerol and sugars). Although glycerol had a greater depressing effect on T g than sorbitol, the latter had a greater impact than glycerol and xylose, as a plasticizer, on the mechanical properties (higher percentage elongation) of the soluble starch–methyl cellulose blends. The tensile strength and flexural moduli of these blends were shown to decrease drastically with an increase in the total plasticizer content. An indirect measurement of glass transitions, comparable to the ones determined with DSC, was obtained from the Arrhenius-type plots of the gas permeability–temperature relationships.

Study of biodegradability of poly(δ-valerolactone-co-L-lactide)s

The biodegradability of poly(δ-valerolactone-co-L-lactide)s was studied both with enzymatic (lipase from Rhizopus arrhizus) and nonenzymatic hydrolyses. The hydrolyzability was evaluated by recording the amount of the hydrolyzed water-soluble products. The enzymatic hydrolysis was considerably affected by copolymer composition. The copolyester, the most susceptible to enzymatic hydrolysis, was the one containing a 90 mol % δ-valerolactone unit. The copolymers were also nonenzymatically hydrolyzed at 70°C. The results were similar to those of enzymatic hydrolysis, confirming the influence of copolymer composition on the hydrolyzability. However, the L-lactide rich copolymers were more susceptible to hydrolysis. These results suggest that poly(δ-valerolactone) is easily degraded by lipase, whereas poly(L-lactide) is degraded through simple hydrolysis.

Preparation and study of novel biodegradable blends based on gelatinized starch and 1,4-trans-polyisoprene (gutta percha) for food packaging or biomedical applications

The gas and water vapour permeability coefficients of novel biodegradable films based on 1,4-trans-polyisoprene and gelatinized starch were determined. The glass transitions, indirectly determined from gas permeability measurements, were compared to those obtained from thermal measurements (differential thermal analysis and dynamic mechanical thermal analysis). Incorporation of a low plasticizer amount in the blend was attempted in order to improve the mechanical properties of the blends. Some initial biodegradability experiments showed that these novel blends are biodegradable. This is primarily due to the presence of starch.