Metal nanoparticles (NPs) are increasingly being used in many areas, e.g., industry, pharmacy, and biomedical engineering. NPs can be obtained through chemical and biological synthesis or using physical methods. AgNPs, AuNPs, CuNPs, FeNPs, MgNPs, SnO2NPs, TiO2NPs, and ZnONPs are the most commonly synthesized metal nanoparticles. Many of them have anti-microbial properties and documented activity supported by many tests against some species of pathogenic bacteria, viruses, and fungi. AgNPs, which are used for the production of commercial self-sterilizing packages, are one of the best-explored nanoparticles. Moreover, the EFSA has approved the use of small doses of silver nanoparticles (0.05 mg Ag·kg−1) to food products. Recent studies have shown that metal NPs can be used for the production of coatings to prevent the spread of the SARS-CoV-2 virus, which has caused the global pandemic. Some nanoparticles (e.g., ZnONPs and MgONPs) have the Generally Recognized As Safe (GRAS) status, i.e., they are considered safe for consumption and can be used for the production of edible coatings, protecting food against spoilage. Promising results have been obtained in research on the use of more than one type of nanometals, which prevents the development of pathogen resistance through various mechanisms of inactivation thereof.
Due to their different properties compared to other materials, nanoparticles of iron and iron oxides are increasingly used in the food industry. Food technologists have especially paid attention to their ease of separation by magnetic fields and biocompatibility. Unfortunately, the consumption of increasing amounts of nanoparticles has raised concerns about their biotoxicity. Hence, knowledge about the applicability of iron nanoparticle-based materials in the food industry is needed not only among scientists, but also among all individuals who are involved in food production. The first part of this article describes typical methods of obtaining iron nanoparticles using chemical synthesis and so-called green chemistry. The second part of this article describes the use of iron nanoparticles and iron nanoparticle-based materials for active packaging, including the ability to eliminate oxygen and antimicrobial activity. Then, the possibilities of using the magnetic properties of iron nano-oxides for enzyme immobilization, food analysis, protein purification and mycotoxin and histamine removal from food are described. Other described applications of materials based on iron nanoparticles are the production of artificial enzymes, process control, food fortification and preserving food in a supercooled state. The third part of the article analyzes the biocompatibility of iron nanoparticles, their impact on the human body and the safety of their use.
The objective of the paper was to describe the impact of freeze-drying conditions on hardness of lyophilizates obtained based on soft fruit pomace. Raspberry, cherry, and grape pomace from the pressing process carried out with a low-speed rotary press constituted a research material. Immediately after the pressing process, pomaces were placed in forms, frozen, and after freezing they were freeze-dried in the pressure of 20, 42, 63, 85 and 110 Pa. The obtained lyophilizates were subjected to the measurement of hardness with the use of texture meter equipped with a penetrometer in the form of a cone with a vertical angle of 30°. The increase of pressure during freeze-drying of samples was accompanied by the increase of hardness of the obtained lyophilizates, which may affect the energy consumption of the grinding process and the nature of rehydration of the final product. Moreover, the water content of raw material, pomaces, and lyophilizates was determined. The obtained results of measurements were subjected to a statistical analysis which showed that the pressure of freeze-drying significantly diversifies the hardness of the obtained lyophilizates.
The magnetic properties of magnetite nanoparticles (Fe3O4 NPs) strongly depend on their chemical and physical parameters, which can be regulated by a controlled synthesis process. To improve the quality of the obtained nanoparticles, their surface is often modified with organic compounds (from the group of surfactants, sugars, proteins, or organic acid). In this study, we synthesized magnetite nanoparticles with a surface modified with the organic compound DMSA. Then, the nanocrystallites were characterized in terms of structure and morphology. To investigate the role of DMSA and to understand the adsorption mechanism, FTIR measurements were carried out. Using Mössbauer spectroscopy, we investigated temperature-induced changes in the magnetic properties of prepared samples. The spectra were recorded in a wide temperature range (from 4 K to 390 K) for two types of samples: powders and ferrofluids with various concentrations. In the case of powder samples, the superparamagnetic doublet appeared at room temperature. For magnetic suspensions, the spectra were more complicated. They consisted of superposition of asymmetrically broadened sextets and doublets, which was caused by the occurrence of long-range dipole-dipole interactions. These interactions affected the magnetic properties of the material and increased the blocking temperature. Additionally, the magnetic hysteresis and zero field cooling-field cooling (ZFC/FC) curves were measured with the use of a vibrating sample magnetometer.
The goal of these study was to present results of investigation concerning possibilities of utilization of harmful wastes in countryside area to produce ecological energy. Biogas production can be important from the point of view of environment protection especially in case of overproduction of animal wastes. Production and utilization of energy from agriculture residues gives a great chance for diversification and grows of income for family farms. Besides energetic and environment gains, we can obtain very valuable fertilizer, which is easy absorbed by plants in field crop production. The experimental study was conducted to investigate the effect of mixing process on the parameters of methane fermentation process. Temperature inside fermentation chamber, pH of fermented material, redox potential and carbon to nitrogen ratio (C:N) were investigated. Utilize wastes from pig and poultry houses were used for the study. Digestion in a chamber was provided at constant temperature of 37 °C. After adding fresh substrate to the digester, the temperature of the raw material decreased by 1,0-1.5 °C depending on the location in the tank. Also, it was observed that biogas production decreased. The mixing process had a positive effect on the homogeneity of the material throughout the digester volume. The best results for biogas production were obtained when the pH value was 7.0. Research results obtained from tested biogas installation show, that from two bio reactors at total capacity of 410 m3 we can get electrical energy at cost of 34,52 € MWh-1 and thermal energy at cost of 62,54 €×MWh-1. While the cost of producing electricity in a professional power plant based on lignite was 76.23 €MWh-1. The energy produced was used for the operational activities of the farm.
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