Analecta Technica Szegedinensia

Food safety-based evaluation of 3D printed objects

2023-09-13T12:02:48+02:00

The 3D printing technology involves a digital manufacturing machine that produces three-dimensional objects according to designs created by the user via 3D modelling or computer-aided design/manufacturing (CAD/CAM) software. This work analyzes the processing timeline of the filament (material for 3D printing) from unboxing to the extrusion trough the nozzle. It is an important task to analyze the growth of bacteria on 3D printed surface and in gaps between the layers. By default, 3D printed object is not food safe after longer usage and direct contact with food (even though the food safe filaments were used), but there are solutions for this problem. We tested several methods to prevent or reduce the emerging microbial contamination. These methods are coating with epoxy resin, using antimicrobial and high temperature-resistant filaments. The best results were obtained by epoxy resin coating, where the object was cleanable like any other injection molded plastic object with smooth surface. Very good results have also been obtained by boiling the objects, and it is good to see that nowadays more and more special filaments have food safe certificate and can withstand boiling temperatures too. Using antibacterial filaments reduced bacterial colonies by 80%, which is not a perfect solution.

Two sample unpaired T-test power calculation using simulation

2023-05-22T06:50:00+02:00

Statistical tests like t test are used to test the hypothesis for comparison of mean between two groups. The result from a t test is used to determine if there a significant difference between the two samples mean, which cannot be attributed to sampling error or to random occurrence. A t test is considered a parametric test, meaning test samples should meet assumptions of normality, equal variances and independence. The article aims to calculate the power of unpaired t test using simulation in Microsoft Excel.

Solid-phase extraction as promising sample preparation method for compound of emerging concerns analysis

2023-09-13T11:59:12+02:00

Today’s environment is under the influence of numerous substances and most of them are not covered by current national and international regulations. Substances that are classified as contaminants of emerging concern, CECs, are not regulated nor systematically controlled in the environment, and they belong to the different chemical classes such as pesticides in current use, pharmaceutically active compounds (PhACs), personal care products, illicit drugs, hormones, micro- and nano-plastics, per- and poly-fluoroalkyl substances (PFAS), and many others. Once released CECs end up in surface water where they can be either accumulated or transported to the other environmental compartments, i.e. soil (by irrigation), underground water, or drinking water. The aim of the research was to investigate the efficiency of different selected solid-phase extraction (SPE) cartridges for preparation of water samples for simultaneous analysis of several CECs. For this purpose, a model mix solution of selected CECs in concentration relevant to environmental appearance was used. The selected CECs (14 PhACs, 11 pesticides in current use, and 4 PFAS) represented emerging contaminants with different properties, including polarities, and varying adverse effect on the environment and human health. Different types of sorbents were investigated: (i) commercial single-layer HLB, (ii) homemade multi-layer I: HLB plus a mix of WAX, WCX, and PPL, and (iii) multi-layer II: mix of WAX, WCX, and PPL plus HLB. The results revealed that the single-layer sorbent showed better efficiency in extraction of the analyzed CECs. Multi-layer sorbent should be further investigated to elucidate the possible reason for the poor extraction of some compounds, as development of a balanced extraction for a wider range of contaminants with different polarities, especially for non-target analysis of chemical residues, is required in order to capture the occurrence of the full profile of micropollutants.

Development of lab-scale gasification systems for different possible applications

2023-07-10T11:30:04+02:00

The goal of gasification is the conversion of solid fuels or carbonaceous wastes to gas that can be further used energetically or for chemically utilisation. Due to cost-effectiveness and gaining experience, the industrial application of new systems and raw materials or mixtures must be preceded by laboratory-scale experiments. The manuscript presents the laboratory scale gasification systems we designed and used, as well as the difficulties experienced during the implementation (e.g. water introduction, sealing, etc.). In addition to these, the results of one-, two- and three-stage experiments are presented as examples, where different materials such as a mixture of wood and canteen waste, brown coal and refuse derived fuel (RDF) were used for testing the system.

The mechanical properties of biodegradable modified polymer packaging

2023-06-29T20:38:22+02:00

In this research, a lactic acid-based biodegradable polymer (polylactic acid, PLA) was chemically modified and the mechanical material property changes were studied. The hardness and elastic modulus were determined with a nanoindentation instrument. The modified PLA was compared to the unmodified control group. Each group contained 5 different samples and t-test was performed to compare the mean difference of the hardness and elastic modulus between the two groups. A statistically significant result was obtained both in the hardness and elastic modulus due to the modification. The treated sample structure has become more inhomogeneous as well. The elastic modulus of the modified PLA reduced in its hardness and elastic modulus compared to the control PLA.

Ethical aspects of inventory management in an agricultural enterprise

2023-05-26T11:55:02+02:00

Inventory management has a different meaning in agriculture than in a commercial chain, but it is just as important. In most cases, the purpose of the inventory is to satisfy demand. Demand and supply do not always meet at a predetermined place and time but are shaped by external circumstances. It is the same in agriculture. Our research aims to present and compare simple inventory management methods through a practical agricultural example and to examine the ethical aspects. To manage inventory, we have to make an appropriate decision in the following two questions: when to order and how much to order. There are three basic inventory mechanisms: cycle inventory, damping inventory, and two-warehouse inventory. There are three levels within business ethics: macro-, meso-, and micro-level. In the case of the examined agricultural limited company, the meso- and micro-levels are affected by ethical problems. When handling inventory improperly, can the employee be held liable, or is the company responsible? The agricultural sector began to develop, which is mainly the result of developments in the use of information technology. Even so, many farms still use outdated methods, which should be changed to operate more economically

Changes of physical and chemical parameters of organic and conventional carrots during storage

2023-05-18T09:39:25+02:00

In industrialised countries, around 670 million tonnes of food are lost every year, much of it still fit for human consumption. Due to the special nutrient management of organic farming, root vegetables have a higher dry matter content and a lower nitrate content, which also affects their shelf-life. The effect of storage under domestic conditions was investigated in our experiments on organic and conventional carrot lots. It was found that packaged organic carrots in a 4°C environment showed the longest shelf life, lowest nitrate content and weight loss during household storage. The results of the experiment may contribute to lower food waste through changes in consumer habits.

Effect of plant extracts on some quality parameters of canned mixed sweet corn-red bean

2023-05-18T09:49:22+02:00

The leading export product of Hungary is canned sweetcorn, which is available in single-component or blended varieties with a focus on colour retention, for wich the food industry mainly uses ascorbic acid and EDTA in the brine of canned vegetable. Thoughtful customer behavior is pushing the food industry to switch to natural plant extracts instead of synthetic additives. In order to investigate if acerola plant extract is suitable as a replacement for ascorbic acid, we investigated the potential uses of two varieties of acerola extract in three different concentrations in the case of canned mixed sweet corn and red bean. After production, and after 1 week of thermostating at 55°C and storage at room temperature for 4 and 8 weeks, the changes in pH value, salt concentration, water-soluble dry matter content, colour, total polyphenol content, and antioxidant capacity of the brine were all evaluated in this experiment. The results showed that both acerola extracts were promising in fixing the colour, with the higher application of the first extract and the lowest and highest dosage of the second extract showing the best results. During storage, the polyphenol content and antioxidant capacity of some samples decreased slightly compared to their initial values.

Permeability measurement theory in case of natural gas and natural gas-hydrogen mixture

2023-05-18T11:47:13+02:00

Green hydrogen, using renewable electricity that breaks down water molecules into hydrogen and oxygen, holds great promise for meeting global energy demand while contributing to climate policy goals. Interest in green hydrogen production technologies has increased considerably. This is because the potential uses of hydrogen cover many sectors, including power generation, manufacturing processes in steel and cement production, fuel cells for electric vehicles, and power grid stabilization. One possible use of green hydrogen is to blend it with natural gas and deliver it to end-users using existing natural gas pipeline storage and networks, thereby increasing performance and reducing emissions. In the case of underground storage of a hydrogen natural gas mixture, it is important to assess its impact on the reservoir beforehand, which rock permeability studies can do. This article deals with the theory of rock permeability testing for natural gas and natural gas-hydrogen mixtures.

The environmental impact of the feral pigeon (Columba Livia f. Domestica) in the historic city centre of Sopron

2023-05-18T11:48:18+02:00

The presence of different bird species in inhabited areas is becoming increasingly common. The problem with these species is that they are more likely to spread pathogens, contaminate public and private land with their droppings, cause economic damage or even frighten the public. One of the most notable conflict species causing environmental pressures in populated areas is the feral pigeon (Columba livia f. domestica), whose populations are increasing worldwide. Adequate practices and methods are available to reduce the problem. However, their applicability and effectiveness may vary from one locality to another due to the different characteristics of the localities and the different causes of the pigeons' presence. Therefore, it is essential to think in terms of town-specific solutions, the preparation of which requires, among other things, an assessment of the temporal and spatial pattern of occurrence of the species causing the conflict, an understanding of the extent of damage and an overview of the population's level of information. In our study, we investigated the environmental pressures of the feral pigeon in the historical city centre of Sopron, using a combination of the three elements mentioned above. For this purpose, we carried out a monthly visual population assessment combined with a photographic technique at sample points for one year. We conducted a field visit to the area to draw up a damage map of the study area and a spatial localisation of existing control methods. Questionnaire surveys complemented this to assess the public's awareness of the issue. In light of the results, we drew up a map of the pigeon conflict in the city centre of Sopron and identified possible solutions.