Improvement of mechanical and heat-sealing properties of edible chitosan films via addition of gelatin and CO2 treatment of film-forming solutions.

Glycerol, gelatin and CO2 were used to prepare chitosan-based packaging films with improved mechanical properties and seal strength. Nuclear magnetic resonance spectroscopy, X-ray diffraction analysis, Fourier transform infrared spectroscopy and dynamic mechanical analysis were conducted; the results were used to explain the mechanical and sealing properties data. Film color was also measured. Combined addition of glycerol and use of CO2 to treat the film-forming solution led to decreased film crystallinity and glass transition temperature, resulting in improved film mechanical properties. Addition of glycerol and gelatin resulted in enhanced molecular interactions between chitosan-gelatin and improved sealability of the films. Films with the best mechanical and sealing properties were obtained from a solution with 25% (w/w) glycerol and treated with CO2 and from that with 25% (w/w) glycerol and 10% (w/v) gelatin, respectively. Films with addition of both glycerol and gelatin exhibited lower lightness, but higher yellowness than the commercial stretch film.

Mechanical properties improvement of chitosan films via the use of plasticizer, charge modifying agent and film solution homogenization.

Glycerol, charge modifying agent (NaCl) and high-pressure homogenization were used to prepare chitosan film-forming solution prior to drying to improve mechanical properties of the resulting films. Zeta potential and viscosity of each film solution were measured, while mechanical properties viz. tensile strength and percent elongation of the films were assessed. X-ray diffraction analysis, Fourier transform infrared spectroscopy and dynamic mechanical analysis results of the films were obtained and used to explain the mechanical property data. Combined use of glycerol, NaCl and homogenization led to increased zeta potential but decreased viscosity of the solution. Electrostatic repulsion led to extended chitosan chains and lower film crystallinity and glass transition temperature due to weaker hydrogen bonding and increased amide-I band interactions. A film with the best mechanical properties (tensile strength of 50MPa and percent elongation of 47) was from the solution with 25% (w/w) glycerol, 15-mM NaCl and homogenized at 10/5MPa.

Optimum condition of producing crisp osmotic banana using superheated steam puffing.

BACKGROUND: Puffing can improve textural property of snacks. Nevertheless, high temperature puffing accelerates non-enzymatic browning reactions. The osmotic treatment using sucrose solution potentially retards the browning, but the high amount of sucrose gain causes hard texture. The objective of this work was therefore to study the effects of osmotic time, puffing time and puffing temperature on banana qualities such as colour, shrinkage and textural property. RESULTS: The experimental results showed that puffing temperature, puffing time and osmotic time significantly affected colour, shrinkage and textual properties. CONCLUSION: The optimisation using response surface methodology was used for a trade-off between colour and textural properties. To obtain a good quality product, the puffed osmotic banana should be operated at the osmotic time of 43 min and puffing temperature of 220 °C and puffing time of 2 min. © 2016 Society of Chemical Industry.

Effects of ripening stage and steaming time on quality attributes of fat free banana snack obtained from drying process including fluidized bed puffing.

Healthy snacks have increasingly been interested in consumers. Puffing technique is an alternative to produce healthy snacks. Effects of ripening stage of banana and steaming time on quality of banana slices obtained from drying process including fluidized bed puffing were investigated. Bananas at the ripening stages 1 and 3 were steamed at 100 °C for 30 s up to 2 min and dried at 90 °C to moisture content of 25 % dry basis (d.b.). The samples were then puffed by fluidized bed dryer at 160 °C for 2 min and dried at the same temperature as the first stage drying. The experimental results showed that shrinkage, drying time, color, glycemic index and textural properties were affected by steaming time and ripening stage. Steaming provided more uniformity of banana color. Steaming positively or negatively affected the degree shrinkage of banana depending on the ripening stage. The banana texture in particular crispiness could be improved by the steaming for the ripening stage 1 banana whilst it did not improve for the ripening stage 3. During steaming, the C-type crystalline structure of banana starch disappeared and thus the value of glycemic index was increased. The ripening stage 1 banana was recommended for producing healthy snack in order to control glycemic response.

Combined effects of drying methods, extract concentration, and film thickness on efficacy of antimicrobial chitosan films.

UNLABELLED: An idea of using a suitable drying method to minimize the loss of added antimicrobial agent and, at the same time, to modify the structure, and hence the release characteristics of chitosan films was proposed. Chitosan film-forming solution was incorporated with galangal extract (0% and 1.5% w/w) and formed into films with the thickness of 15 and 30 µm via hot air drying (HD) (40 °C) and low-pressure superheated steam drying (LPSSD) (70 °C, 10 kPa). The extract retention, release characteristics, and antimicrobial efficacy of the films were then assessed; fresh-cut cantaloupe was used as the test food material, while Staphylococcus aureus was the test pathogenic microorganism. The retention and release of 1,8-cineole, a major bioactive compound in the galangal extract, was monitored during 5-d storage at 25 °C. The film swelling was also evaluated and their results used to interpret the release characteristics of 1,8-cineole from the films to the cantaloupe. At the same thickness, the films prepared by HD had lower extract retention and higher degree of swelling, thus exhibiting faster extract release and lower antimicrobial efficacy than the films prepared by LPSSD. Within the same drying method, the increased film thickness led to higher extract retention and antimicrobial efficacy. The concentration of the extract in the cantaloupe matched well with the extract retention and release characteristics as well as the antimicrobial efficacy of the films. PRACTICAL APPLICATION: The results of this work illustrate the feasibility of using a suitable drying technology to improve the quality of antimicrobial films from edible biopolymer and form the basis for future development of an improved antimicrobial film production process.

Quantitative evaluation of microstructural changes and their relations with some physical characteristics of food during drying.

UNLABELLED: Drying is known to affect various quality attributes of a food product, especially its physical properties. However, changes of physical properties or characteristics are generally due to changes of the product microstructure. Nevertheless, not much quantitative information, as opposed to abundant qualitative information, is available to describe in detail relationships between microstructural and physical changes of food undergoing drying. The present study, thus, aimed at studying quantitative relationships between microstructural and selected physical changes of a test material, that is, carrot, undergoing hot air drying at 60 and 80 °C. The microstructural changes were represented quantitatively in terms of the normalized changes of the fractal dimension (ΔFD/FD(0)) of microstructural images of the samples as well as the normalized changes of the sample average cell diameter (ΔD/D(0)), while the physical changes of interest were shrinkage and hardness. The results showed that during an earlier period of drying ΔFD/FD(0) as well as ΔD/D(0) tended to increase with decreasing moisture content; deformation of the microstructures (represented either in terms of ΔFD/FD(0) or ΔD/D(0)) led to increased shrinkage and hardness. On the other hand, deformation of the microstructures existed, while the moisture content did not change much during the final stage of drying. The relationships between ΔFD/FD(0) and both physical changes were quite well established; ΔD/D(0)were also found to correlate well with the physical changes. Either ΔFD/FD(0) or ΔD/D(0)could thus be used as a tool to monitor the apparent physical changes (shrinkage and hardness) of a sample during drying. PRACTICAL APPLICATION: Either the normalized changes of the fractal dimension of microstructural images of a sample or the normalized changes of the sample average cell diameter can be a useful tool in monitoring the drying process by 1st assessing the product volumetric shrinkage, which can be assessed easily on-line and on a real-time basis by such techniques as image analysis, and then relating the obtained results through microstructural changes to other apparent physical changes, including the product texture.