No abstract

Bioplastics may solve environmental issues related to the current linear plastic economy, but they need improvement to be viable alternatives. To achieve this, we aimed to add chitin nanocrystals (ChNC) to polylactic acid (PLA), which is known to alter material properties while maintaining a fully bio-based character. However, ChNC are not particularly compatible with PLA, and surface modification with fatty acids was used to improve this. We used fatty acids that are different in carbon chain length (C4–C18) and degree of saturation (C18:2). We successfully used Steglich esterification and confirmed covalent attachment of fatty acids to the ChNC with FTIR and solid-state 13C NMR. The morphology of the ChNC remained intact after surface modification, as observed by TEM. ChNC modified with C4 and C8 showed higher degrees of substitution compared to fatty acids with a longer aliphatic tail, while particles modified with the longest fatty acid showed the highest hydrophobicity. The addition of ChNC to the PLA matrix resulted in brown color formation that was reduced when using modified particles, leading to higher transparency, most probably as a result of better dispersibility of modified ChNC, as observed by SEM. In general, addition of ChNC provided high UV-protection to the base polymer material, which is an additional feature that can be created through the addition of ChNC, which is not at the expense of the barrier properties, or the mechanical strength.

Highlights Novel home freezing provides quick freezing at 1.51 cm h − 1 for strawberry. Strawberries reached -15°C approximately 234 minutes shorter in the novel system. Color was protected better after quick freezing during 4 month storage. Antioxidant activity of the strawberries increased 8.96% after the novel freezing. Fruits and vegetables can be frozen quickly at home by this novel cabinet.

Freezing rate and storage time are the most important parameters in the losses of bioactive compounds of food during the freezing process. For this reason, the quality of strawberries which were frozen at different freezing mediums and the effect of storage time on samples were investigated in this research. The freezer section of the domestic refrigerator was used for slow freezing. Besides that, a modified freezer cabinet which capable of blowing air at a speed of 1.2 m/s at -30°C designed and produced by Bosch und Siemens Hausgerate GmbH (Çerkezköy,Turkey) was used for quick freezing. In the quick freezing chamber inside the refrigerator, the samples were provided to be frozen with a higher freezing speed than the static freezing unit of the refrigerator. Freezing time and freezing rates were determined from the cooling curves obtained experimentally. Slow and quick frozen samples were stored at −25°C for 4 months. Drip loss, total phenolic content, ascorbic acid content and total monomeric anthocyanin content of samples were significantly different after freezing and during storage time. It has been determined that higher freezing rate is essential for the better preservation of bioactive compounds of the strawberries. Freezing should be done at an appropriate freezing rate to preserve the cell structure and the nutritional content of strawberries.

About 1/3rd of produced food goes to waste, and amongst others, advanced packaging concepts need to be developed to prevent this from happening. Here, we target the antioxidative functionality of food packaging to thus address food oxidation without the need for the addition of antioxidants to the food product, which is not desirable from a consumer point of view. Chitin nanocrystals (ChNC) have been shown to be promising bio-fillers for improving the mechanical strength of biodegradable plastics, but their potential as active components in plastic films is rather unexplored. In the current study, we investigate the antioxidant activity of chitin nanocrystals as such and as part of polylactic acid (PLA) films. This investigation was conducted using DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity. Chitin nanocrystals produced via acid hydrolysis showed five times higher activity compared to crude chitin powder. When using these crystals as part of a polylactic acid film (either inside or on top), in both scenarios, antioxidant activity was found, but the effect was considerably greater when the particles were at the surface of the film. This is an important proof of the principle that it is possible to create biodegradable plastics with additional functionality through the addition of ChNC.