Composite films based on pumpkin oil cake obtained by different filtration process

Abstract

Packaging is inseparable retainer of almost all food products. However, most of produced packaging ends as packaging waste after consumption of the product. Increasing amounts of packaging waste that should be managed represents serious challenge of every modern society. There are many different approaches to address this subject, amongst which biodegradable, natural biopolymer-based or even edible packaging holds considerable potential. In this paper, a by-product of edible oil industry, left after completed extraction by cold pressing of oil from hulls of pumpkin seeds, was used to produce biopolymer packaging films. Pumpkin oil cake was used to produce composite bio-based films. Different filtration of film forming suspension was applied in order to test composite film production using different filtration fractions, leading to higher process yield and minimizing waste. In addition, films were casted on surface, about ten times larger comparing to the cast surface typically reported for these types of films in the literature, in order to test the possibility for commercial production and scale up process. Also, casted mass of film forming suspension was varied in order to define minimal casting mass per unit area. Presented results showed that biopolymer films based on the pumpkin oil cake can be successfully produced in sheets (50x35 cm), compared to films earlier produced in the form of discs with diameter 12 cm. Different filtration fractions from initial film forming suspension can be used for film formation, leading to increased production yield. Different filtration fractions lead to different film properties that should be adjusted according to selected application. Casted mass of film forming suspension was successfully decreased (comparing to earlier literature data) without compromising film functional properties and minimal casting mass was defined as 26 g/m 2 .

Pumpkin seed oil cake/polyethylene film as new food packaging material, with perspective for packing under modified atmosphere

“…For coarsely filtrated films, thickness was higher, compared to other two fractions with same film‐forming suspension mass, 0.149 ± 0.014 mm for CF150/PE and 0.203 ± 0.012 for CF250/PE (approximate value of sole PuOC layer thickness in these films is around 0.119 mm and 0.173 mm). Obtained difference in thickness might be due to the tightness of film network, as well as due to different components present in coarsely filtrated films, leading to different inter and intramolecular bonds Similar phenomena was already reported for PuOC films obtained by different filtration process 21 . During 90 days storage, no significant change in all film thickness values was observed ( p > 0.05).…”

“…These values of swelling ability are somewhat lower than values reported for PuOC films without PE layer, as well as soy protein isolate and concentrate films,100-250%. 14,21,32,[36][37][38] The solubility of films in water was about 35% for all tested samples and this solubility is similar to the value obtained for PuOC films without PE layer, as well as to films based on soy protein isolates and crosslinked gelatine films. 9,14,21,39,40 Considering that one side of the film was protected with PE layer it was expected that solubility of the normal direction, the elongation at break was 150-250% and in the parallel 100-150% for all films except CF/PE films.…”

“…The swelling of most films was about 90%, and slightly higher values were observed with FF150/PE, 99.5% and CF250/PE, 103% films. These values of swelling ability are somewhat lower than values reported for PuOC films without PE layer, as well as soy protein isolate and concentrate films,100–250% 14,21,32,36–38 …”

“…This difference might be due to the tightness of film network, as well as due to different components present in coarsely filtrated films, leading to different inter and intramolecular bonds as well as different hydrophilicity of available groups. Presence of PE, a non‐polar film that covers and protects one side of hydrophilic PuOC layer did not affect two‐layer film water content, which is similar to water content of sole PuOC film 21 and PuOC protein isolate film, 16,31 as well as other biopolymer films, like soy protein isolate, chitosan or corn starch based films 32–35 …”

“…Casting was performed on a levelled flat surface controlled by a spirit level 20 . Two different casting masses of film‐forming suspension were used, 150 g and 250 g, according to previous experiments 21 . Films were air dried for 2 days at room conditions (23 ± 2°C and 50 ± 5% RH).…”