Five different drying profiles, including a single triangular shape temperature pattern, two constant and two time-varied schemes were examined, aiming to minimize the drying duration and maintain the product quality. The profile that temperature was gradually increased from 35 ◦C to 60 ◦C within 8 h, was found to be the most appropriate in terms of quality retention  and drying duration. A different study by Xanthopoulos et al., evaluated two stepwise drying schemes, following a step-up and a step-down temperature profile on apricot halves. The constant temperature drying at 55 ◦C had almost the same drying duration with the step-up profile using three temperature stages of 40–55-70 ◦C. The step-up profile presented improved antioxidant activity under the treatment with ascorbic acid and almost a constant drying rate that was initially lower than the constant temperature drying. However, the drying was stopped at MR = 0.35 and no conclusions can be drawn for the final moisture content of apricot halves. Non-stationary temperature schemes of convective drying with an increase of air drying temperature, is reported to have a shorter or almost equal drying duration compared with the low constant drying temperatures and improved effects on quality, compared with the high constant temperature drying. However, given each product’s morphological properties, the appropriate rate of temperature increase and the selection of lower/upper temperature limits can affect differently the quality and the drying time. Thus, one gap that needs to be addressed is how the moisture loss is affected under different increasing temperature rates for the same range of the final upper constant temperature limit, indoor growers and the lower initial constant temperature level.

Accounting the lack of drying kinetic studies of hemp in literature, the present study aims to:  experimentally investigate the convective drying behavior and moisture removal of Cannabis sativa L. leaves for stationary and non-stationary drying conditions at a constant airflow velocity,  determine the kinetic profile that characterizes the convective drying of Cannabis sativa L. leaves by evaluating mathematical drying kinetic models. Drying rate versus time and moisture content is presented in Fig. 3. The drying process of hemp leaves at the examined drying conditions occurred entirely in the falling rate period, whereas no constant rate period was observed. The previous fact indicates that liquid diffusion is most likely the dominant physical mechanism, governing the water migration in Cannabis sativa L. from the interior to the surface of the leaves. Drying rate in time-varied temperature conditions resemble the drying rate behavior of the lowest constant temperature, since the initial applied temperature has been 40 ◦C. It is evident that higher constant drying temperatures and higher airdrying heating rates, are associated with increased drying rates and acceleration of the moisture removal, leading to shorter drying duration. Previous observations are in agreement with similar drying kinetic studies of various medical and aromatic plants submitted to hot air drying in the literature, reporting absence of constant-rate periods and similar trends between the applied constant drying temperatures. Global energy demand remains high even with the COVID-19 pandemic. Production of energy from fossil fuels has a negative impact on environmental health wellbeing and ecological balance. Many countries are requested to achieve challenging emissions reductions targets that will result in global net zero by 2050 and keep 1.5 ◦C within reach. To achieve these targets, investment in renewables is one of the solutions. Among renewable energy resources, biomass will play a vital role. Agricultural residues are lignocellulosic biomass considered to be major feedstocks for biorefineries. In many counties, hemp, Cannabis sativa L., is becoming a high-valued economic crop. It is a herbaceous plant grown up under different climatic conditions. Products from hemp include food and pharmacy. However, after processing two-thirds of starting raw materials become wastes, which are usually discarded or burned. Alternatively, hemp hurds/residues may be used as fuel, as they contain hemicellulose  and cellulose. Pyrolysis is a promising technology for converting hemp hurds into high-value products: biochar and bio-oils. Determination of kinetic and thermodynamic parameters for pyrolysis of a specific feedstock is essential for the design, optimization, and operation of the pyrolysis system.

For kinetics of biomass pyrolysis, Onsree et al. studied kinetics of corn residue pellets and eucalyptus wood ships pyrolyzed with heating rates of 5–15 ◦C/min using Kissinger-Akahira-Sunose  and Flynn-Wall-Ozawa  methods. They demonstrated that the kinetic parameters were a function of feed stock conversions. A discrete DAEM was also used to analyze kinetic parameters of pyrolysis of corn residues with high prediction accuracy. It can be seen that, by varying kinetic parameters, different biomass materials would have different pyrolysis behaviors. For thermodynamic analysis of biomass pyrolysis, Singh et al.investigated thermodynamic properties for pyrolysis of banana leaves at low heating rates of 10–30 ◦C/min and found that ΔH, ΔG, and ΔS fluctuated when the pyrolysis process proceeded. To the authors’ knowledge, very few studies on pyrolysis of hemp residues were reported, and conducted only at relatively low heating rates without considering thermodynamic properties. DAEM was rarely used in analyzing pyrolysis of hemp residues. Therefore, the current work aims to analyze kinetic and thermodynamic properties of pyrolysis of hemp hurds through the use of a discrete DAEM technique. Pyrolysis of hemp hurds was carried out from room temperature to 1000 ◦C at low and intermediate  heating rates. Decomposition of hemp hurds during pyrolysis was characterized and discussed. By the discrete DAEM, the accuracy of the model for predicting pyrolysis behaviors of hemp hurds was evaluated. Effects of different heating rate ranges on kinetic and thermodynamic properties of pyrolysis of hemp hurds were discussed. Information on kinetic and thermodynamic parameters is crucial for designing a pyrolysis reactor for hemp hurds, especially in large-scale production of biochar. The opinion about meat products and its impact on human health has become very negative in recent years. Dietitians pay attention to the high cholesterol and fat content or the amount of saturated fatty acids causing obesity and heart related diseases. According to the World Health Organization , total fat should supply less than 30% of energy from the diet and saturated fat should contribute less than 10%. The abundance of many chemical additives and smoking procedures are the main cancerogenic factors associated with the consumption of processed meat . At the same time, consumers in the developed countries tend to be interested in functional foods of vegetable and animal origins that, besides their role in providing basic nutrient components, are able to modulate the physiological system and prevent diseases. This goal is realized by adding various bio-active compounds such as n3 fatty acids, vitamins, selenium, dietary fibre or lactic acid bacteria, or simply by decreasing the animal fat content and/or exchanging it for more healthy fats . Lowering fat content or replacing the animal fat to develop healthier meat products may increase the production costs and change the products’ sensory properties .

Moreover, the consumers prefer and are willing to pay more for the product if it contains the ingredients coming from natural  sources . Hemp seed or the by-products obtained during oil production may be examples of such additives . Despite the fact, that it is one of the oldest crops cultivated all over the world, and is a valuable source of nutrients, it has been prohibited from cultivation because of the presence of psychotropic substances . Varieties containing up to 0.2% of THC  are approved by the European Union . The trend of a growing interest in hemp seed and food products containing hemp ingredients can be observed especially among vegans in many countries . Roasted seeds are a popular snack in China and hemp seed oil has been used for a long time in Russia and many other Eastern countries . There are also increasingly more various hemp products appearing on the market. They were used as food additives in breads, yoghurts, cookies or meat cutlets . Hemp seeds contain 27–30% of oil, 24–28% of protein, 20–34% carbohydrates, 10–15% insoluble fibre and 5.0–5.8% of mineral substances. The oil consists of 80–90% polyunsaturated fatty acids  including 50–70% linoleic  and 15–25% α-linolenic acid , and the n6/n3 ratio is 2.5–3.0. Hemp seeds contain wide range of minerals like calcium, magnesium, iron, manganese or zinc. The amino acids present in hemp seeds are comparable to those from egg or soy . In vitro and in vivo studies conducted by Girgih et al.  have shown that hemp seed peptides have the potential to be used as antioxidant and antihypertensive agents. Hemp proteins and hemp flour are by-products obtained from the oil extraction. They are also protein rich substances, trimming tray which could be used as an alternative to soy ingredients for preparing meat products. Moreover, functional products could be formulated using hemp additives because of the many health promoting ingredients present in hemp . To the best of our knowledge, there is no data in the scientific literature on the quality of meat products with hemp or hemp by-products. Therefore, the aim of this study was to verify if hemp seed, dehulled hemp seed, hemp flour and hemp protein could be used in the production of meat loaves and how they influence the products quality.The chemical composition of hemp additives and of all the manufactured variants of pork loaves is presented in Tables 2 and 3, respectively. The chemical composition of the Białobrzeskie hemp strain used in this study was similar to the composition of Finola hemp strain ; it contained less fat and more minerals compared to the commercially available hemp seeds  used by Worobiej, Mądrzak, and Piecyk .

Few publications show the quality of hemp flour or hemp protein which are available on the market. Hemp flour is prepared from defatted hemp seed, so it contains significantly less fat than the hemp seed, which was confirmed in our study . Svec and Hruskova  used hemp flour containing 32 g of protein and 8 g of fat in 100 g of a sample for bread production. A similar level of fat , but a lower amount of proteins  in commercially available hemp flour was reported by Korus, Gumul, et al.  and Korus, Witczak, et al. . The fat content in the hemp flour analysed by Worobiej et al.  contained 5.6 g/100 g of fat and 31.1 g/100 g of protein. The amount of fat may depend on the producer and the oil extraction method . Fibre content was high in all of the ingredients except the de-hulled hemp seed.The protein content was significantly higher in products with hemp seed, and the ash content was significantly higher in the products with hemp seed or de-hulled hemp seed. The fat content was comparable in all the samples with slightly higher amount in products with both hemp seed and de-hulled hemp seed. Moisture content was lower in all the meat loaves with various hemp additives compared to the control sample. The total fibre content in the meat loaves increased significantly thanks to the hemp additives. The results show the highest level of dietary fibre in the products with hemp seeds and hemp proteins . Fibre intake is associated with decreased constipation problems, obesity, colorectal cancer risk and diabetes , so it is worth increasing its content in meat products which naturally do not contain fibre. A significant increase was noted in the magnesium, manganese and iron content associated with the addition of every hemp ingredient . Magnesium plays a role in many regulatory processes in the human organism. Its deficiency is associated with depression and sleeping disorders . The Recommended Daily Intake for adults is 320–420 mg . The manganese requirement for an adult is 1.6–2.3 mg/day and it is required for proper reproductive system function, energy metabolism, metallo enzymes activity, antioxidant reactions regulation, etc. Iron availability from meat has been proven to be higher compared to the plant sources, but it is still only 15–30%, which means that any increase of the iron content may be treated nutritionally favourable. There are studies showing that even 180 g of pork per day does not fulfil the organism’s requirements. Moreover, meat intake increases non-haem iron availability .