In recent years, 3D printing has become a rapidly developing manufacturing technology with huge potential and is influencing many industries, such as engineering, art, education, medicine, aerospace, and many more. Of the many technologies, the one used most frequently is the FDM (fused deposition modeling) method, which is widely available, relatively simple and inexpensive. The essence of this method is to extrude a thermoplastic material through a heated nozzle in a controlled manner. PLA, or polylactide, is a naturally sourced material with good biodegradable properties. It is frequently used in 3D printing and is derived from natural ingredients such as maize starch or sugar cane. The current study aimed to determine the effects of adding plant-origin food industry by-products, such as carrot pomace and ground walnut shells, to PLA on the mechanical and biodegradable properties of specimens printed using the FDM technology. The assumed research objective is consistent with the issue of sustainable development in the management of by-products from the food industry. The study used a pulverized fraction of each additive, with a particle size of less than 0.2 mm, which was introduced into the base material PLA at rates of 1%, 3% and 5%. The mixtures prepared in this manner were used to print (using FDM technology) standardized specimens, which were assessed for strength (bending and breaking tests) and biodegradability (weight loss after 60 and 120 days of storage under varying climatic conditions). It was observed that the additive increased the bending strength parameters (by a maximum of 44.9%, as compared to the raw material with no additives) while decreasing the breaking stress (by a maximum of approximately 15%, as compared to the raw material with no additives). Using plant additives increased biodegradability (up to 7.6%) compared to the control material.

Juices produced on an industrial scale are largely devoid of pectin substances, and lack a significant part of their vitamins, carotenoids and polyphenols. In recent years, physical methods have been used for preliminary treatments prior to pressing, allowing the elimination of enzymatic treatment. This paper presents the results of a study on the effect of freezing and thawing, as a preliminary treatment, on the efficiency of pressing and on the quality of juice obtained from northern highbush blueberry. Preliminary treatment of pulp, consisting in its freezing and thawing, caused a notable (23.1%), but lower than that for enzymatic treatment (34.9%), increase in pressing efficiency relative to control samples. The highest content of lutein and vitamin C was obtained in juice acquired from pulp subjected to treatment consisting in its freezing and thawing prior to pressing. The application of enzymatic treatment caused a 26.9% increase in the content of juice extract, while the treatment consisting in freezing and thawing caused a 19.5% increase in the content of extract. Irrespective of the type of preliminary treatment applied, a degradation of l-ascorbic acid and an increase in the content of dehydro-l-ascorbic acid were observed in the juices produced. The method proposed permits the production of juices with health-promoting properties, due to the application of freezing as a preliminary treatment.