Flask m8 head

Water uptake capacity was measured according to the ASTM D570 method [26 ], using a third of the rectangular bioplastic specimens, that is, a rectangular sample measuring 20 × 10 × 1 mm. The specimens were dried in a conventional oven (UN 55, Memmert, Schwabach, Germany) at 50 $°$ C for 24 h to determine the dry weight. Immediately after, they were immersed in distilled water for 24 h. Finally, they were submitted to a freeze-drying step at −80 °C under vacuum in a LyoQuest freeze-dryer with a Flask M8 head (Telstar, Seville, Spain) and their weights after these last two steps were employed to determine their water uptake capacity and soluble matter loss according to the following equations:

where w₁, w₂ and w₃ are the weight of the bioplastic after dehydrothermal treatment, the immersion step and the freeze-drying stage, respectively.

The water-uptake capacity (WUC) values were evaluated following the ASTM D570 standard [43 ]. For this, the samples were immersed in distilled water and weighed after 24 h to obtain the wet-mass value (wet weight). Finally, they were subjected to a freeze-drying process at −80 °C under vacuum conditions in a LyoQuest freeze-dryer with a Flask M8 head (Telstar, Terrassa, Spain) after being previously frozen at −40 °C. After this drying, the final dry weight was obtained. The value of WUC was obtained using the following equation: $$WUC\left(\mathrm{\%}\right)=\frac{Wet weight-Final dry weight}{Final dry weight}·100$$

Water uptake capacity (WUC) was measured according to the ASTM D570 method [25 (link)] using one-third of the rectangular samples mentioned above, that is, probes measuring 20 mm × 10 mm × 1 mm. The samples were subjected to a dehydrothermal treatment in a conventional oven at 50 °C (Memmert UN 55, Schwabach, Germany) for 24 h to determine the dry weight (Initial dry weight). Subsequently, they were immersed in distilled water and weighted after 24 h of immersion (Wet weight). Finally, they were frozen at −40 °C before lyophilization at −80 °C and vacuum atmosphere (0.125 bar) using a LyoQuest freeze-dryer with a Flask M8 head (Telstar, Barcelona, Spain) and subsequently weighted (Final dry weight). According to the methodology used, WUC and soluble matter loss (SML) were determined by the following equations: $$WUC \left(\%\right) = \frac{Wet weight-Initial dry weight}{Initial dry weight}·100$$
$$SML \left(\%\right) = \frac{Initial dry weight-Final dry weight}{Initial dry weight}·100$$