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Ultrasound pretreatment of vegetables has been a hot topic recently and has shown promise in significantly reducing overall processing time. The objective of this study was to investigate the effects of high-intensity ultrasound treatment with different amplitudes and treatment times using an indirect and direct ultrasound device on the microbiological safety of butternut squash by monitoring microbiological growth during 28 days of storage at room temperature. Classical microbiological methods of cultivation on selective media were used to determine the presence of microorganisms. The results showed that the shelf life of the squash was better with the combination of pretreatment and drying than with drying and/or pretreatment alone. All treatment combinations were microbiologically safe after 28 days. The best results were obtained with samples treated with ultrasound at an amplitude of 60 % for 6 minutes before vacuum drying, and no microorganisms were detected in any of the samples.

This research was aimed to make biolayer coatings enriched with orange peel essential oil (OPEO) on synthetic laminate, oriented poly(ethylene- terephthalate)/polypropylene (PET-O/PP). Coating materials were taken from biobased and renewable waste sources, and the developed formulation was targeted for food packaging. The developed materials were characterized for their barrier (O2, CO2, and water vapour), optical (colour, opacity), surface (inventory of peaks by FTIR), and antimicrobial activity. Furthermore, the overall migration from a base layer (PET-O/PP) in an acetic acid (3% HAc) and ethanol aqueous solution (20% EtOH) were measured. The antimicrobial activity of chitosan (Chi)-coated films was assessed against Escherichia coli. Permeation of the uncoated samples (base layer, PET- O/PP) increased with the temperature increase (from 20 °C to 40 °C and 60 °C). Films with Chi-coatings were a better barrier to gases than the control (PET-O/PP) measured at 20 °C. The addition of 1% (w/v) OPEO to the Chi-coating layer showed a permeance decrease of 67% for CO2 and 48% for O2. The overall migrations from PET-O/PP in 3% HAc and 20% EtOH were 1.8 and 2.3 mg/dm2, respectively. Analysis of spectral bands did not indicate any surface structural changes after exposure to food simulants. Water vapour transmission rate values were increased for Chi-coated samples compared to the control. The total colour difference showed a slight colour change for all coated samples (ΔE > 2). No significant changes in light transmission at 600 nm for samples containing 1% and 2% OLEO were observed. The addition of 4% (w/v) OPEO was not enough to obtain a bacteriostatic effect, so future research is needed.

The obtained results present different process parameters for drying in air fluidized beds and also a significant contribution of an immersedheat exchanger element. In this process, the drying time at lower temperatures is shorter, the product quality is higher and the rehydration time is shorter as well. This paper comprises research work on celeriac and peas dried in a fluidized bed. The goal has been to obtain dry vegetables with 6% to 10% water content and of good rehydration quality. Experimental data (bed height, gas temperature and velocity, pressure drop over the bed, drying time and total humidity of drying) have been measured and relevant values have been calculated. First the aerodynamic properties of fluidizing bede in motion were experimentally investigated and then the particles were dried at given temperatures in different time intervals and at an air flow rate ranging from 0, 30 m/s to 4, 93 m/s. Two columns of different dimensions were used: a cylindrical column (d = 0, 10 m and h = 1, 0 m) and a square column (a = 0, 09 m, b = 0, 18 m and h = 0, 83 m). Working parameters were: 1. Particle dimensions (blanched): 5x5x5 mm and 5x5x10 mm for celeriac and 8 mm (first class) and 9 mm (second class) diameter for peas 2. Particle mass: 0, 200 kg, 0, 300 kg and 0, 400 kg 3. Drying temperature 40°C, 50°C and 60°C The results have shown that drying of vegetables in a fluidized bed produces dry vegetable pieces of excellent quality in a much shorter time than in continuous bell-dryers which are generally used. The best results of celeriac drying were obtained with the following dimensions of celeriac: 5x5x5 mm, 200 g, in a cylindrical column at 60°C and the maximum air flow rate of 4, 3 m/s. The best results of peas drying were achieved with the first class peas, 400 g, in a square column at 60°C and at the maximum air flow rate of 2, 46 m/s.

Nettle is a highly valued medicinal plant that is still largely neglected, both in terms of nutrition and use for pharmacological purposes. Tinctures, i.e., alcoholic extracts, are becoming increasingly popular nettle products, mainly because they allow better availability of phytochemicals and their stability over a longer period of time. The production of alcoholic extracts is a chemically demanding process that is still usually carried out using conventional techniques, which have numerous drawbacks. The use of green technologies such as ultrasound-assisted extraction (UAE), which is characterized by high efficiency of phytochemical extraction, shorter treatment time, and a much lower environmental footprint, is a suitable and sustainable solution. Therefore, the aim of this study is to determine the influence of the extraction method, conventional and ultrasound (by varying two ultrasound equipment systems), time and ethanol concentration on the extraction of specialized metabolites from nettle powder. Ultrasonic extraction using a probe system significantly contributed to increase the ascorbic acid yield, polyphenolic compounds, and antioxidant capacity of nettle extracts compared to conventional extraction. In addition, when a probe system was used during UAE, significantly less time was required for isolation of individual specialized metabolites compared to ultrasonic extraction in the bath. Ethanol concentration (50 and 80% v/v) also proved to be an important factor in the efficiency of extraction of specialized metabolites, with 80% ethanol being more effective for the isolation of ascorbic acid and pigment compounds (chlorophyll and carotenoids), while 50% v/v for the extraction of polyphenolic compounds. It can be concluded that extraction with the ultrasonic probe system is much more efficient in obtaining higher yields of specialized metabolites from nettle powder in a shorter time (average process duration 5–10 min) both compared to UAE in the bath and classical extraction. However, optimization of the key factors of time, solvent type, and ultrasonic power is necessary to maintain the nutritional quality of the nettle extract in order to obtain a final product with a high specialized metabolites content, antioxidant capacity, and functional value. The future application of alcoholic nettle extracts is based on the fact that these products have significant potential as functional foods and pharmacological preparations for the treatment of a number of but also to strengthen the immune system, mainly due to the rich nutritional composition and high content of various specialized metabolites. The prepared extracts can be safely taken orally by diluting the tinctures with water immediately before ingestion.

Pumpkin (Cucurbita L.) is a squash and gourd fruit vegetable grown worldwide. The large production of pumpkin is related to the growing interest of consumers in the intake of a wide range of nutrients and phytochemicals through an adequate and balanced diet. As a result of the large use of pumpkin (cooked, baked, and processed), various by-products, such as peels and seeds are produced. Although these by-products are commonly used to fortify animal feed, much of them go unused. To find out whether these discharged fractions can be reused as a low-cost source of value-added compounds, the results of their chemical composition are presented in this study. The content of moisture, ash, fat, protein, and dietary fibre was analysed not only in the peels and seeds, but also in the raw pumpkin from which these residues are obtained. The results showed that peels and seeds contained higher amounts of ash (0.97-2.75%), fat (3.24-21.44%), proteins (4.27-14.88%), and dietary fibre (18.52-56.55%) compared to raw pumpkin. The content of ash, fat, protein and fibre in raw pumpkin was 0.55%, 1.54%, 1.76% and 17%, respectively. The moisture content decreased in the following order: raw pumpkin (93.97%), pumpkin peel (87.78%) and seeds (9.81%). From the results it can be concluded that the utilisation of pumpkin fractions is interesting not only from the environmental point of view, but also from the nutritional point of view due to the high content of ash, fat, protein and fibre. Of course, the mineral composition and content as well as the amino acid and fatty acid profiles still need to be completed to verify their status as sustainable food ingredients.

Energy consumption during drying operations has great potential to be improved using novel non- thermal processing technologies. Technologies such as high-intensity ultrasonics can be used as pre- treatment to drying operations, which due to mechanical and thermal effects of cavitation can improve mass diffusion and consequently shorten drying times. Shortening the drying time could potentially lead to a decrease in energy consumption and waste production, which improves the ecological and economic aspects, increasing the sustainability of the whole process. This study investigates the effect of pre-treatment of pumpkin in an ultrasonic bath on the drying time and total energy consumption for the drying process. Square pumpkin pieces were processed using 30 %, 60 %, and 90 % of maximal ultrasonic power (380 W at 37 kHz) for 30 min, 45 min, and 60 min. Drying is conducted under atmospheric (1 bar) and low (0.1 bar) pressure at 60 oC. Obtained results show a significant difference in total used energy during conventional and vacuum drying (2, 04 ± 0, 17 kWh kg-1 compared to 3, 92 ± 0, 11 kWh kg-1). An increase of ultrasonic power leads to a significant shortening of the drying time from 365 min to 320 min for conventional and from 265 to 190 min for vacuum drying. Pre-treatment using 90 % of maximal power combined with drying at 1 bar uses 2, 75 ± 0, 21 kWh kg-1, while the same treatment at 0.1 bar uses 4, 88 kWh for drying 1 kg of fresh pumpkin material. An increase in ultrasonic processing time exhibits the same behavior, as there is a significant increase in total energy consumption (3, 75 kWh kg-1 for conventional and 5, 41 kWh kg-1 for vacuum) while there is still a significantly shorter drying time. However, vacuum-dried pretreated samples had much better sensory properties such as texture and color. In conclusion, while pre-treatment using an ultrasonic bath did not have any influence on the decreasing of total energy consumption, it contributes to significantly shorter drying times. The combination of pre-treatment with vacuum drying has the potential to contribute to the sustainability of the drying process, as total energy consumption can be further improved using larger batches of material or possibly using much shorter processing times. Such processes would be much more beneficial using high powered ultrasound with an immersion probe, as it can process the surface of the material with the same amount of mechanical energy in a much shorter amount of time. Acknowledgment: This work was supported by means of the Croatian Science Foundation project IP-2019-04-9750.

Drying is well-known as an effective process for food preservation. The main benefits of the drying process are restricted growth of microorganisms, reduced degradation reactions related to moisture content, and decreased mass during transportation [1]. Among the advantages of using microwaves in drying, two of them stand out. First, an increase in drying rate with a reduction in time of processing, due to faster diffusion and better heat transfer. Second, the ability to improve quality, including eliminated case hardening and better sensory attributes, appearance, colour, and texture [2]. This study aimed to examine the effect of convective drying combined with microwaves on drying kinetics and the colour of pumpkin pulp (Cucurbita maxima). Hybrid drying of pumpkin pulp were performed at five microwave powers (119 W, 336 W, 462 W, 595 W, 700 W) for 2 minutes coupled with hot air drying (60 °C, air velocity 1 ms-1). The results show that microwave- assisted hot air convective drying significantly affects drying kinetics and colour. Higher microwave power shortens the drying time. Total colour difference is increasing due to the increase in microwave power. Increasing the microwave power results in a decrease in lightness (L*) and yellowness (b*). The hybrid drying can be accepted as an alternative drying process for pumpkin pulp.

According to the new guidelines for waste management, procedures to prevent the generation of waste and techniques to recover it take precedence over recycling and disposal. Plant food waste (organic residues) and by-products from fruits and vegetables represent a nutritionally valuable source rich in numerous specialized metabolites important for human health. Therefore, the recovery of such by-products into valuable resources is crucial for the production of new food products, especially in order to reduce food waste. The pumpkin by-product is also a valuable source of numerous metabolites, especially vitamins, dietary fibers, polyphenolic compounds and carotenoids, and therefore represents a valuable material for further utilization. One of the ways to produce new products is the drying process, which very often has a negative impact on the nutrient composition of the plant material due to the high temperature and is also energy consuming. For this very reason, innovative pre-treatment methods such as ultrasound and hybrid drying techniques (vacuum-conduction) are being developed. Vacuum drying uses low pressure to evaporate water at lower temperatures, preserving heat-sensitive bioactive compounds such as vitamins, carotenoids, and other phytochemicals, while ultrasound pre-treatment also offers a number of benefits, most notably significantly shortening the drying process and preserving nutrients. The aim of this study was to determine the influence of temperature (60 and 70 °C) and ultrasound pre-treatment (37 kHz, 380W, Elmasonic P 300H, ultrasonic bath 100%) during hybrid vacuum-conduction drying (100 mbar) of pumpkin organic residue on the content of specialized metabolites. Drying processes were performed in a vacuum drying oven VO 200 (Memmert, Germany) at a pressure of 100 mbar. The pumpkin slices were dried to a final water content of 14%. The highest vitamin C content (439.14 mg/100 g DW) was determined in pumpkin samples pre-treated with ultrasound for 5 min and dried at 70 °C ; total phenolic content (1655 mg GAE/100 g DW) was also determined by vacuum drying at a temperature of 70 °C without ultrasound pre-treatment. The β-carotene content was best preserved by vacuum drying at 60 °C with ultrasound pre-treatment for 10 min. In general, all dried pumpkin samples are characterized by high antioxidant capacity, proving that hybrid vacuum drying combined with ultrasound pre-treatment has a positive effect on nutritional potential. In conclusion, ultrasonic pre-treatment had a significant effect on the preservation of bioactive compounds in the dried pumpkin samples, while drying by vacuum (100 mbar) at both combined temperatures (60 and 70°C) showed no negative effects on the nutritional composition of the pumpkin samples. Therefore, it can be concluded that this method of drying and ultrasonic pre-treatment is an efficient way to preserve the nutritional composition of the raw material, thus giving the organic residues the possibility of additional recovery and further use and utilization.

Pumpkin is one of the inexpensive and widely available fruits that can be kept for one to three months after harvest. To extend its shelf life and avoid microbial spoilage, moisture loss and colour changes, convective hot air drying (HAD) can be used. This method enables the use of pumpkin powder as an excellent, nutrient-rich ingredient for the production of various food products. The proposed work shows the results of chemical composition of pumpkin powder obtained after drying the pulp with hot air at temperatures of 50, 60 and 70 °C and airflow velocities of 1.5 and 0.5 m s-1. The results show that the dried pumpkin pulps have a low moisture content, ranging from 9.62 to 16.59% depending on the temperature and airflow velocity. Ash content ranges from 5.78 to 8.08%, followed by high amounts of dietary fibre (6.98-10.18%) and low fat content (0.32- 0.88%), regardless of drying parameters. The protein and sugar content is particularly high, ranging from 8.90 to 10.98% and 50.80 to 66.07%, respectively, depending on the drying parameters. Overall, the low moisture content indicates that the shelf life of the pumpkin can be extended by HAD. Because of the high ash and low fat content, the dried samples are probably an excellent mineral and fat free source. The high levels of dietary fibre, protein, and sugars indicate that the dried pumpkin pulp may be considered an acceptable and valued food ingredient due to its great nutritional potential.

Multifunctional packaging systems have a high potential for commercial packaging applications. By applying the layer of the biopolymer coating on the polymer surface, it is possible to change its barrier properties and can serve as a transporter to deliver active substances having a special function to packed food. Life style and market demands pushes food industry towards the development of new materials that consequently leads to the increased product shelf life while minimising the impact on the nature and climate. The main aim of this study was to investigate the possibility of applying naturally friendly chitosan coating on the surface of commercially available oriented poly(ethylene- terephthalate)/polypropylene (OPET/PP). This bi- layer material is used as the cover film for PP buckets ; in which bakery fruit fillings are stored. Moreover, orange peel essential oil was used as the active compound that was nanoencapsulated in the coating. The essential oil was prepared by microwave assisted extraction coupled with ETHOS. This method is environmentally friendly providing green production concept by minimising the use of naturally unfriendly solvents. Also, by reusing the orange peel as a food waste, this study contributes to a sustainable material production. Produced materials were tested for their gas and water vapour barrier performance, physico-chemical properties (thickness, UV transmission and colour), and antimicrobial properties. The results show the possibility of improving the commercial material properties. It is possible to couple the traditional with green extraction technology to reuse natural product considered as a food waste for food packaging and thus minimise the negative impact on the nature. In order to better check the functional character, further investigation is needed on real food products during their storage and impact on their shelf-life.

High-intensity ultrasonics as novel food processing technology have increased use in the food industry. The cavitation effect of ultrasonic processing can influence a wide array of food processing operations such as mixing, emulsification, inactivation of microorganisms, and drying. Drying is one of the most energy-intensive operations in the industry, and as such could strongly benefit from using novel technologies to help before or during drying. High-intensity ultrasonics have a thermal and mechanical impact on processed food, due to the high energy and pressures obtained in an implosion of cavitation bubbles during the propagation of the ultrasonic wave in high liquidcontent materials. Such impact in the vicinity of the food surface can have an impact on the cellular structure, specifically modifying the matrix and enlarging pores inside processed food. As drying is a mass transfer process, it is heavily influenced by the pore sizes in the food. In this way, ultrasonic pre-treatment can significantly increase mass transfer and consequently shorten drying times. This can potentially lead to a decrease in energy consumption and ensure a more sustainable process. This study investigates the effect of the ultrasonic treatment of pumpkin on the drying time. For the experiment, square pumpkin pieces were processed using two different types of ultrasonic treatment. Ultrasound with the probe was used at 30, 60, and 90 % of maximal amplitude during 3, 6, and 9 min. For the second type of treatment, an ultrasonic bath was used at amplitudes of 30, 60, and 90 % during 30, 45, and 60 min. Drying was performed using a conventional convective tray dryer at 60 oC using an airflow of 0.5 ms-1. Statistical analysis is performed using ANOVA and posthoc tests in Statistica software. MANOVA analysis of obtained results shows a significant change in drying times which correlate to both types of ultrasonic pre-treatment. The drying time of control samples was 305 min, which was a baseline for further analysis. Samples treated using an ultrasonic bath show a statistically significant decrease in the drying time (down to the shortest drying time of 248 min, processed at 90 % of maximal amplitude) which correlates to the increase of the amplitude. This same property was confirmed using the ultrasonic probe, as drying time was shortened to 245 min for samples treated with 30 % of maximal amplitude for 9 min. Further increase of ultrasonic power seems to have no further influence on the drying time. The ultrasonic probe was proven to be more effective in the sonication of pumpkin samples, with much shorter processing times and lower amplitudes needed for the same effect on the drying time. In conclusion, while pre-treatment using an ultrasonic have a significant influence on the decreasing of drying time, such a process would be much more beneficial using high-powered ultrasound with an immersion probe, as it can process the surface of the material with the same amount of mechanical energy in a much shorter amount of time.

Drying is an important method to prevent post-harvest losses of pumpkin fruit and to obtain a more stable pumpkin powder. Pumpkin powder has a longer shelf life, desirable sweet taste and yellow-orange color, and could be used as a functional ingredient and natural color additive due to its nutritional and health-promoting properties. The simultaneous separation of pumpkin pulp for drying purposes resulted in large amounts of the waste fractions, i.e., the peel and seeds. Considering the nutritional potential of all pumpkin (Cucurbita maxima Duchese) products, i.e. pulp, dried pulp and by-products, the aim of this work was to compare the amounts of proteins and sugars obtained from them. Drying was carried out at temperatures of 50, 60 and 70 °C and air velocity of 0.5 m/s. To maximize the recovery of proteins and sugars from the pumpkin samples, ultrasound-assisted extraction was performed at a frequency of 37 kHz and a temperature of 50 °C for 10, 20, and 40 min. The results showed that all dried pumpkin pulp samples contained significantly higher amounts of proteins (7.80-12.67%) than raw pulp (1.03-2.30%), making them a potential source of nutrients. As the results show, a drying temperature of 60 °C can be considered optimal for protein extraction during 20 minutes. The optimal time for sugar extraction with ultrasonic treatment was set at 40 minutes with mass fractions of 49.39%, 49.70%, and 49.44% at temperatures of 50, 60, and 70 °C, respectively. Obviously, the dried samples are a valuable source of sugar compared to the raw pumpkin, which contains 2.99-5.61% sugar depending on the extraction time. The protein and sugar content is also higher in the pumpkin by-products than in the raw pulp. The results show that the amounts of sugars are 1.10-1.79% (seeds) and 4.86-9.11% (peels) and proteins are 4.31-4.76% (seeds) and 1.87-7.54% (peels), depending on the extraction time. In conclusion, all pumpkin components studied in this work can be considered as a valuable source of nutrients. Considering that seeds and peels are usually discarded, both by-products are interesting from a nutritional point of view and could be reused in line with global sustainable trends in the use of food by-products.

The avocado (Persea americana) is a fruit widely consumed throughout the world and is an important dietary source of valuable essential nutrients and phytochemicals. Due to the high consumption and industrial processing of avocado, large amounts of residues, peels and seeds are generated, which represent a major environmental problem due to the large production volumes and the inadequate and insufficient use of avocado residues. Currently, most of this waste is discarded and underutilized. The pulp of the avocado and its waste (peel, seeds, pulp after oil extraction) contain bioactive compounds such as ascorbic acid, vitamin E, phenolic compounds and carotenoids, high levels of proteins, carbohydrates (starch, fiber), monounsaturated fatty acids and minerals (especially potassium). Extracts from all parts of the avocado fruit exhibit antioxidant, anti-inflammatory, antimicrobial, anticancer, antidiabetic, and anti-atherogenic properties. Due to their numerous health benefits, the consumption and production of avocados have increased greatly in recent years. Therefore, the pulp and waste of avocado are a potential source of bioactive compounds suitable for use in foods or dietary supplements. In addition, avocado seed waste is the main source of biomaterials such as starch and can therefore be used as an alternative starch source in the textile industry. Avocado seeds are also rich in antioxidants, natural dyes, biodiesel, and a phenolic compound that can be used for various applications in the pharmaceutical and cosmetic industries. The processing of avocados produces large quantities of avocado peels, which contain large amounts of valuable compounds. Avocado peels are a remarkable source of biomolecules, including phenolic and flavonoid compounds, and can be used as a food preservative, antioxidant, or functional ingredient in novel food formulations. The use of avocado byproducts as a source of natural compounds is a way to extract value-added ingredients while having a significant impact on avocado industrial applications and the environment.

Pumpkin is a fruit vegetable that is commonly cooked, baked and processed into various pumpkin products in the food industry, such as pumpkin pie, bread, cookies, cheesecake, desserts, donuts, cereals, ice cream, lasagna dishes, etc. Due to the large global production and use, it is necessary to use preservation methods that allow to preserve the properties of pumpkin for a long period of time. One of the most commonly used methods is convective hot air drying, which reduces water activity and thus minimises microbiological changes. However, during the drying process, structural and chemical changes may occur in the fresh material, which eventually affect the product quality. Therefore, with the aim of extending the shelf life of fresh pumpkin pulp (Cucurbita maxima D), hot air drying was also used in this work. Experiments were conducted at three different temperatures (50, 60, and 70 °C) and speeds (1.5, 1.0, and 0.5 m/s) using the following combined parameters: 50 °C (1.5, 1.0, and 0.5 m/s), 60 °C (1.0 and 0.5 m/s), and 70 °C (0.5 m/s). The chemical properties of the dried samples were evaluated based on moisture content, crude ash, crude fat, and crude fibre content. To evaluate the chemical composition of the dried samples and the efficiency of drying, analyses were also performed on fresh, undried pulp. In addition to the dried and undried pumpkin samples, the peel and seeds were also analysed as potential sources of nutrients, which are by-products of the preparation of fresh pulp for drying. As the result showed, pumpkin pulp and peel contained significantly higher moisture content (93.97 and 87.78 %, respectively) than dried pulp (11.78 - 19.55 %, depending on temperature and drying speed) and seeds (9.81%). The highest ash content is found in dried pumpkin peel (5.55 - 8.23 %), followed by pulp (0.55 %), peel (0.97 %) and seeds (2.75 %). The fat and total fibre content are particularly high in pumpkin seeds, 21.44% and 56.55%, respectively. The high fat (3.24%) and fibre (18.52%) content is also found in the shell. Therefore, both by-products can be considered as valuable sources of fat and fibre, compared to dried samples with slightly lower amounts of these nutrients (1.03 - 3.13 % for fat) and (8.52 - 13.99 % fibre). In conclusion, the drying process resulted in a decrease in moisture content, which increased the shelf life of the squash. The dried samples are likely an excellent source of minerals due to their high ash content compared to the other samples. Although the fat and fibre content decreased due to the drying process, the results obtained indicate that the functional properties of the pumpkin can be maintained after drying.

Cilj ovog rada bio je utvrditi utjecaj parametara sušenja (temperatura, vrijeme sušenja i tlak) na fizikalna svojstva ploda muškatne tikve, boju i vlažnost, odnosno gubitak mase mesa (mezokarp) ploda tijekom sušenja u kondukcijskoj vakuum sušari. Smanjenje tlaka u sustavu i povećanje temperature značajno utječu na brzinu sušenja i konačnu vlažnost uzoraka, pri čemu je postignuta razlika u smanjenju vlažnosti uzoraka od 6, 9 puta. Porast temperature ima nepoželjne uočljive, a smanjenje tlaka slabo uočljive do uočljive promjene u boji (∆E*) mesa ploda muškatne tikve. Povećanjem temperature s 40 na 70 °C uz smanjenje tlaka od atmosferskog na 50 mbar pri vremenu sušenja od 300 minuta dolazi do značajne razlike u vrijednosti ∆E*, odnosno vrlo uočljive razlike u boji sa 6, 60 na 13, 43 (d∆E*=6, 83). Temperatura sušenja od 70 oC pri 1 bar uz vrijeme sušenja od 120 min pokazala se optimalnom za postizanje vlažnosti od 16, 40 % uz promjenu boje ∆E* od 4, 03.

Pumpkin is recognized as a functional food source. Although pumpkin pulp is a nutritionally valuable food source, its chemical properties change over time. The objective of this work was to determine spectrophotometrically the total protein and sugar content of pumpkin pulp dried at an air flow of 1.0 m/s and a temperature of 50 and 60 °C, respectively. Protein and sugar content were also determined in pumpkin peels and seeds to address the global sustainable trend of recycling unused by-products. Proteins and sugars were extracted from all samples using ultrasound-assisted extraction at a frequency of 37 kHz, a temperature of 50 °C, and durations of 10, 20, and 40 min. The recovery of both nutrients was also compared with reflux extraction performed during 20 and 40 minutes. The results obtained showed that high contents of proteins (12.83%) and sugars (48.93%) were present in the dry samples extracted with UAE. The content of proteins and sugars depended on the drying temperature and extraction time. The contents of proteins and sugars obtained by reflux extraction were also high, 10.66% (proteins) and 56.14% (sugars). The raw pulp contained between 0.83 and 1.54% proteins and 4.64 to 5.71% sugars. The raw seeds contained 8.99 to 27.55% proteins and 2.36 to 14.06% sugars, while the raw peels contained 1.21 to 2.41% proteins and 1.90 to 2.72% sugars, depending on the extraction method. Therefore, both by-products are valuable sources of two nutrients and could be used as an alternative sustainable source of food ingredients.

Global production of pumpkin (family Cucurbitaceae) has increased in the past year due to various consumption alternatives. Pumpkin can be consumed raw or cooked, baked, frozen, dried, crystallised, and freeze-dried. One of the most commonly used pumpkin processed products is flour, as it can be stored for a long time. As a natural colour additive, it can be added to baked goods, soups, sauces, and instant noodles to not only increase the content of various nutrients, but also improve their flavour. The simultaneous separation of pumpkin pulp for different uses results in large amounts of waste fractions, i.e. peel and seeds. From a nutritional point of view, the pumpkin pulp, pumpkin flour, peel and seeds are valuable sources of proteins, fibres, sugars, minerals, etc. Considering their functional properties and benefits for human health, the main objective of this work was to study the quality parameters of pumpkin pulp (Cucurbita moschata, "butternut" pumpkin), dried pulp and by-products in order to compare which of them represent nutrient-rich sources. In this context, dry matter, crude ash, crude fat and crude fibre were analysed in all pumpkin fractions. The drying process was carried out with air at 50 and 60 °C and a speed of 1.0 m/s. The results showed that pumpkin peels and pulp had significantly higher moisture content (90.43 and 91.56 %) than the dried pulp samples (11.9 - 18.62 %) and seeds (5.44 %). On the other hand, dried fruit pulp samples contained high ash content (7.91 - 8.23 %), followed by pulp (0.78 %), skin (1.22 %) and seeds (4.83 %). The fat and total fibre contents are particularly high for pumpkin seeds, 35.57% and 24.86%, respectively. The high fat (1.90 %) and fibre (16.68 %) contents are also found in the shell compared to the pulp and dried pulp. The pulp contains 1.30 and 12.79 % fat and fibre, respectively. The dried pulp contains between 0.39 and 0.43% fat and 10.37 to 12.23% fibre, depending on the drying temperature. In conclusion, all the pumpkin components studied in this work can be considered a valuable source of nutrients. For example, the dried samples with low moisture content extended the shelf life of pumpkin and due to their high ash content are an excellent source of minerals. Considering that seeds and peels are usually discarded, both by-products are interesting from a nutritional point of view due to their high fat and fibre content. Finally, the pulp, with its high moisture content, could be considered a useful source of water intake as part of a balanced diet.

Jam is food with intermediate moisture, and it is usually microbiologically stable due to large amounts of sucrose. However, it can be spoiled due to osmophilic acid-tolerant flora, and from the industrial standpoint to ensure the safety of the final product during packaging, hydrogen peroxide is usually used as an antimicrobial agent. This leads to changes in surface appearance such as colour and can also change some textural and rheological properties. Textural characteristics as one component of the sensory properties of food have a very important role in the acceptability of food, as it influences mouthfeel. Mechanical properties of food and foodstuff are specific for the type of the food, but most important are hardness, elasticity, stress, and strain, as well as several others relevant to gel-like materials such as extrusion force, adhesion, spreadability, and stickiness. Those properties have a very important role in further processing steps in the food industry such as pumping, extrusion, drying, baking, and others. Rheological properties such as yield stress and shear stress are also in direct correlation to jam quality and its functionality in the development of final products. Therefore, it is important to retain desired properties while introducing novel food processing technologies for microbial inactivation. Based on the power, amplitude, intensity, and other parameters such as the amount of liquid in the processed system, ultrasonic waves can produce a cavitation effect, which disperses large amounts of thermal and mechanical energy in the system. High-intensity ultrasonic treatment can thus introduce several changes in the cellular structure of treated material, which can consequently exhibit significant changes in textural and rheological properties. Methods for determination of the textural properties of jams and eventual changes after ultrasonic treatment are based on the instrumental texture analysis with various probes such as conical spreadability probe, and back and front extrusion cells. Rheological properties of jams are measured using a viscometer at different temperatures (20 oC to 60 oC) and different shear rates (form 0.1 s-1 to 150 s-1) and calculation of the relationship between shear stress and shear rate is performed using Herschel – Bulkley model. The time dependency of jams at those parameters is calculated based on the kinetic mathematical models by various authors such as Weltman, Figoni, or Hahn. Based on the correlation of ultrasonic parameters such as power and sonication time to measured textural and rheological parameters, optimal processing parameters can be determined to obtain desired log5 reduction of microorganisms and thus ensure microbiological safety, while retaining optimal functional properties of jams. Acknowledgment: This work was supported by the project “Increasing the development of new products and services arising from research and development activities - phase II\”: Development of innovative products to increase food quality \”- KK.01.2.1.02.0282.

Pumpkin is one of the inexpensive and widely available fruits grown mainly in tropical and subtropical countries. After harvesting, pumpkins can be kept for one to three months. After that, they become susceptible to microbial spoilage, moisture loss and colour changes. To extend the shelf life of pumpkins, various drying methods such as convection and vacuum drying can be used. These methods allow the use of pumpkin powder as an excellent ingredient rich in colour and nutrients in the production of various food products. In this context, the proposed work shows the results of protein and sugar evaluation of pumpkin powder obtained after drying the pulp with hot air at temperatures of 50, 60 and 70 °C and velocity of 1.5 and 0.5 m/s. The main objective of this work was to investigate whether the parameters used affect the extraction of proteins and sugars and whether the nutritional properties of pumpkin are maintained after drying. Extraction of two analytes from dried samples was performed by ultrasound-assisted extraction (UAE) at a frequency of 37 kHz, a temperature of 50 °C, and times of 20 and 40 min for protein and sugars, respectively. The results obtained by UV/Vis spectrophotometry showed that the dried samples had a high content of proteins (9.26-10.98%) and sugars (37.97-66.07%) depending on the drying temperature and air velocity. As the results show, there is not much difference among the dried samples in terms of protein content. However, the drying parameters had a stronger influence on the sugar content. The highest protein content (10.98%) was found in a pumpkin powder dried at 70 °C at an air velocity of 0.5 m/s, while the sugar content was highest in a sample dried at 60 °C at an air velocity of 0.5 m/s. Overall, the results showed that dried pumpkin powder is rich in proteins and sugars and therefore can be considered as an acceptable and valued food ingredient due to its nutritional potential. Acknowledgements: The work was supported by the Croatian Science Foundation (research project "Hybrid drying and valorization of plant food waste and by-products" IP-2019-04-9750) - HYDRYBY.