Physical properties of edible films based on bovine myofibril proteins

Myofibril proteins have excellent filmogenic properties. The objective of this article was to study the effect of the thermal treatment, of the pH and of the plasticizer concentration (Cp) of the filmogenic solution (FS), using over some physical properties of edible films, using a surface and response methodology (SRM). Films were made of lyophilized myofibril proteins (LMP) extracted from bovine muscle, employing the technique of solubility obtained from diluted saline solutions. The films were elaborated from FS containing 1 g of LMP/100g of FS and from Cp of 50 g to 79 g of glycerin/100 g of LMP. The LMP was dispersed in water under moderate agitation, and the pH was kept at 2.5-3.5 with the use of acetic acid. The FS were submitted to thermal treatment at different temperatures for 45 minutes. Films were dried in ventilated oven at 37 degrees C/18hr, conditioned at 75% of relative humidity at 25 degrees C/48 hr before analysis of: mechanical properties by puncture test; apparent opacity by spectrophotometer; solubility by immersion in water; and water vapor permeability by the gravimetric method. In general, films showed good appearance, translucent, easily handled and touchable, except for the films formed with pH 2.5 and at a low temperature (35 degrees C), with a medium thickness of 0.400 +/- 0.005 mm. The pH of the FS significantly affected all the physical properties under study. The temperature of the thermal treatment of the FS greatly affected the force at the rupture, solubility and water vapor permeability. This treatment can promote intermolecular interactions through the formation of disulphide bonds; however a very intense treatment can reverse this effect by irreversible structural alterations in the proteins. The glycerol concentration affected considerably all the properties under study, with the exception of the apparent opacity. Plasticizer increases the mobility of macromolecules with consequences in all physical properties.

Effects of Different Moisture Contents on Physical Properties of PVA-Gelatin Films

In this work, it was investigated the effect of different moisture contents on PVA-gelatin films by means of dielectric properties, infrared spectroscopy, microwave response and gravimetric method. The films were elaborated from a blend of gelatin and PVA, with 0 and 25 % glycerol. The sorption isotherms were determined by gravimetric methods, at 25 A degrees C. A capacimeter was used for dielectric measurements, and a device called SOLFAN setup was used for microwave measurements. The sorption isotherms were markedly affected by the glycerol content and relative humidity, due to the hygroscopic nature of the films. The dielectric constant and the microwave response signal were also strongly affected by the moisture and glycerol content in the films. Finally, Infrared spectra showed some changes in the amide peak positions, attributed to the modifications in the interactions between the macromolecules. The behaviors obtained in this work were explained on the basis the way the water enters in the film matrix.

Comparison of physical properties of two exogenous surfactants: new parameter.

The pulmonary surfactant has essential physical properties for normal lung function. The most important property is the surface tension. In this work, it was evaluated the surface tension of two commercial exogenous surfactants used in surfactant replacement therapy, poractant alfa (Curosurf, Chiesi Farmaceuticals, Italy) and beractant (Survanta, Abbott Laboratories, USA) using new parameters. A Langmuir film balance (Minitrough, KSV Instruments, Finland) was used to measure surface tension of poractant alfa and beractant samples. For both samples, we prepared a solution of 1 mg/m dissolved in chloroform (100π`), which was applied over a subphase of milli-Q water (175 ml) in the chamber of the balance. The chamber has two moving barriers that can change its surface area between a maximal value of 112.5 cm 2 , and a minimal value of 22.5 cm 2, defining a balance cycle. Each surfactant had its surface tension evaluated during 20 balance cycles for three times. Four quantities were calculated from the experiment: Minimum Surface Tension (MTS), defined as the surface tension at minimal surface area during the first cycle; Mean Work Cycle (MWC), defined as the mean hysteresis area of the measured surface tension curve of the last 16 balance cycles; Critical Active Surface Area in Compression (CASAC) or in Expansion (CASAE), defined as the maximal chamber area where the surfactant is active on the surface in compression or expansion. The t-test was applied to verify for statistical significance of the results. Comproved with the MST is the same reported in literature, the differences between MWC, CASAC, and CASAE were statistically significant (p<0.001). The MWC, CASAC and CASAE were higher for poractant alfa than for beractant. A higher MWC for poractant alfa means higher elastic recoil of the lung in comparison with beractant. Using a different methodology, our results showed that poractant alfa is probably more effective in a surfactant replacement therapy than beractant due the use of poractant alfa in relation to the use of beractant in preterm infants with Respiratory Distress Syndrome (RDS).