Comparison of drying systems in terms of energy consumption, effective mass diffusion, exergy e�ciency and improvement-sustainability index in the valorizations of waste tomatoes by thermal processes

In this study, the effect of carrier agent added at the rates of 5% and 10% to tomatoes with physical defects that have no market value and the effects of convective (CD), vacuum (VD), hybrid (HD), temperature controlled microwave (MTCM) methods on the energy parameters of powder production processes were investigated. The products reached their �nal moisture values in the shortest time with the MTCM method and in the longest time with the CD method. Effective moisture diffusion varied between 8.01x10 − 8 -1.97x10 − 6 m 2 /s. It has been determined that MTCM has the lowest energy consumption. SMER values of drying processes varied between 0.0018329–0.007384 kg/kWh. SEC values ranged between 546.76-135.42 kWh/kg. Exin, Exout, Exevap, Ex-Vdryer, Ex-Vdrying, SI and IP values of drying processes are 3.65–4.54 J/s, 3.13–3.43 J/s, 10.91–14.17 kJ/kg, 2.94–3.72, 0.72–0.90, respectively. The values varied between 3.60–9.99 and 0.34–0.91. It has been observed that the VD method is more advantageous than other drying methods in terms of exergy energy values. The MTCM method was found to be more advantageous in terms of drying time and energy consumption parameters.


Introduction
45% of agricultural products produced globally are waste [13,10].14.4% of these wastes occur in the eld, 8.8% in consumption, 8.5% in processing, 7.1% in distribution and 6.9% in post-harvest processes [16, 39,10].).In the structure of agricultural product wastes, especially fruit and vegetable wastes; There are plenty of substances with nutritional ( ber, vitamins and minerals), physicochemical, antioxidant, bioactive, antimicrobial and antibacterial properties [28,10].These wastes have a high potential to be transformed into new value-added products after being processed through physical, chemical and thermo-chemical processes.One of these valued products is food powder.Food powder is a popular topic.It is reported that the economic value of fruit powder is 13.52 million dollars.It is reported that this economic value will increase by 7.40% and reach 14.52 million dollars [20,50].With the decrease in the weight and volume of agricultural products turned into dust, transportation-storage costs decrease [27] and their shelf life is extended.One of the products that are turned into powder and used is tomato.Tomato (Lycopersicon esculentum L.) is one of the most consumed vegetables with high nutritional value.Ripe tomato fruit is rich in avour, bre, vitamins, minerals, salt and organic acids.The structure of tomato contains 0.6-6.6%dry matter, 0.95-1.0%protein, 4.0-5.0%sugar, 0.2-0.3%fat, 0.8-0.9%cellulose, 0.6% ash, 0.5% organic acids, 19-35 mg/kg vitamin C, It contains 0.2-2 mg/kg carotene, 0.3-1.6 mg/kg thiamine and 1.5-6 mg/kg ribo avin [7,15].According to the 2021 data of the FAO, the amount of fresh vegetable production in the world is approximately 1 billion 155 million tons, and the amount of tomato production has a large share of 16.38% in fresh vegetable production [14,11].
Before being turned into powder, agricultural products are subjected to a drying process.The thermal removal of moisture content from fresh products is called drying.The main purpose here is to preserve the quality characteristics of the product [6], keep energy consumption at a minimum level and increase energy e ciency by creating high heat-mass transfer.It is reported that an average of 10-25% of the amount of energy spent in the production-consumption chain is consumed only in drying processes [34], and in industrially developed countries, this rate varies between 7-15% on average [2].For this reason, in order to reduce energy consumption, products are dried in different systems and their performance values are investigated in terms of energy parameters [26,44].In the literature, Tagnamas et al. [47] dried carob seeds in a solar type convective dryer at temperatures of 50, 60, 70 and 80 ºC.They reported that temperature values were signi cantly affected by energy parameters.They found that the energy e ciency rates of drying processes varied between 2.6-4.2%.Kusuma et al. [25] dried banana leaves using microwave-assisted convective, microwave and convective methods.They determined the average energy consumption values according to drying processes as 0.0193, 0.0198, and 8.100 kWh, respectively.El-Mesery et al. [12] dried grape fruits with a hot air convective dryer.They investigated the thermal analysis of drying processes.Thermal e ciency rates of drying varied between 50.31 and 74.52%.The lowest thermal e ciency was found between 29.77% and 52.45%.Minimum speci c energy consumption was found to be 27.44 MJ/kg.Regarding the energy analysis of drying processes, Kamble et al. [22], Guangbin et al. [17], and Moreno et al. [32] etc.Many studies have been done.No comprehensive study has been found that investigates the effects of drying methods on the drying kinetics, energy consumption, energy-exergy and sustainability and improvement analysis of the processes of converting tomato powder into tomato powder with different drying systems using waste tomatoes.
In this study, the drying kinetics and effective moisture diffusion of tomato powder drying processes produced by microwave assisted hot air hybrid (HD), modi ed temperature controlled microwave (MTCM), hot air convective (CD) and vacuum assisted convective drying (VD) systems using waste tomatoes were investigated energy consumption, energy-exergy e ciency, sustainability and recoverability indices were investigated.

Fresh product
The waste tomatoes used in this study were samples collected in the soilless agriculture greenhouse in the spring of 2023.Within the scope of the study, Alsancak Fı tomato variety was selected for powder production.This type of pole is a product suitable for eld and greenhouse cultivation, but also does not have resistance and/or tolerance to biotic and abiotic stress factors.As a result of the inhibition of calcium intake due to sodium-calcium competition in the environment where the product is grown, products with ower nose physiological disorders and no market value have been used in the production of powder.Before moisture determination and drying of the products, the stem and leaf parts of the tomatoes were removed and washed thoroughly with chlorinated tap water.The parts with blossom end rot were cut and cleaned with a sharp knife (Fig. 1).

Preparation of puree
Waste tomatoes samples were blanched for 1 minute with a WARNING brand HGB2WTG4 model, 220-240 V, 50-60 Hz, (400 W) glass blender and turned into a puree.5%, and 10% Parmor brand maltodextrin (C12H22O11) was added to the prepared puree and mixed with a hand blender for 5 minutes.Use Beko brand 2166 model (700 W) food processor (1.5 min) to homogeneous the dried samples.

Moisture determination processes and drying processes
To determine the initial moisture content of waste tomato puree, it was dried in an oven (Şimşek labrteknik brand-ST-055 model) set at 70 ºC (Pixton and Warburton, 1973) until the weight change was constant.The initial moisture content (d.b.) of the samples was determined as an average of 4.60 ± 0.21 g moisture/g dry matter.It was dried to an average value of 0.035 ± 0.024 g moisture/g dry matter.The weight change of dry waste tomato puree samples was determined with an AND brand GF-300 model precision scale.MTCM (70 ºC), HD (350 W + 70 ºC), VD (70 ºC) and CD (70 ºC) were used to dry waste tomato purees (Table 1).Şimşek Laborteknik brand, ST-055 model hot air convective dryer was used.The samples were dried in the CD method at temperature of 70 ºC.
Modi ed temperature controlled microwave (MTCM) An Optris brand non-contact infrared temperature sensor is mounted on the Kenwood brand 13J28 model microwave oven, taking into account the technical speci cations.The drying material in the microwave oven was dried by placing it on a rotating glass tray.The device used is a household microwave oven with 230 V, 50 Hz and 800 W technical speci cations.In addition, it has a 2450 MHz feature.The surface temperature of waste tomato puree samples is measured with a non-contact infrared temperature sensor.The read values are transmitted to the control panel.MTCM stops when the surface temperature of the product reaches the drying temperature set on the control panel.After a 15second rest period, MTCM automatically starts working again when the product temperature falls below the speci ed drying temperature (± 2 ºC).If the product temperature does not decrease to the lower value of the drying temperature during this period, it rests for the speci ed period [48,38].The samples were dried in the MTCM method at temperature of 70 ºC.

Vacuum drying (VD)
CLS brand, CLVO-64T model vacuum dryer was used.The samples were dried in the VD method at temperature of 70 ºC.

Hybrid drying (HD)
The hybrid dryer is an oven-assisted microwave dryer.The drying process is carried out by placing the materials on the rotating glass tray inside.The hybrid dryer is Ariston brand, model MWHA 33343 B. In this dryer, waste tomato purees were dried at 350 W + 70 ºC..

Calculation of moisture content
Here: Mt.Moisture content (g water g dry matter − 1 ), dt; min., DR; dry rate (g water g dry matter min − 1 ).
Equation number 3 was used to determine the moisture content removed during the drying process.
Here: MR; moisture rate, M; Instant moisture content (g moisture/g dry matter), Me; Equilibrium moisture content (g moisture/g dry matter), Mo; initial moisture content (g moisture/g dry matter).

Energy consumption values
Polaxtor brand PLX-15366 model power meter (± 0.02 kWh) was used to measure the energy values consumed in the drying processes of waste tomato puree.

Speci c moisture extraction rate (SMER)
Equation number 5 was used to calculate the amount of moisture removed (SMER) in response to the unit energy value in the drying processes of waste tomato puree [45].

Speci c energy consumption (SEC)
Equation 6 was used to calculate the speci c energy consumption value of waste tomato puree drying processes [33].

Statistical analysis
Datas were evaluated by SPSS23.Duncan test was performed with the program.SigmaPlot10 to generate drying kinetics curves.program was used.Reliability values were calculated based on p < 0.05.

Drying values
Moisture and drying rates determined in different drying methods of waste tomato puree are given in Fig. 2.
According to Fig. 2, microwave drying methods dried waste tomato puree in a shorter time than convective drying methods.The reason for this is that the drying rates detected in microwave drying methods are higher than in convective drying methods.Kılıçlı et al. [24] found that the drying time decreased at high temperatures in the drying process of tomato puree using the convective drying method.This is due to the increase in drying rates as temperature increases.In all drying methods, drying time decreased by increasing the carrier agent ratio from 5-10%.This is because the carrier agent had an accelerating effect on the removal of water from the product during drying.Özçelik et al. ( 2019), increasing the carrier agent ratio used in blackberry puree contributed to the decrease in drying time.The average DR values of waste tomato puree dried using 5% and 10% carrier agent by CD, VD, HD and MTCM methods are 0.0051-0.0061,0.0073 − 0.0069, 0.050-0.054and 0.0174 − 0.0169 g moisture/g dry matter.min,respectively.It was determined as.Kılıçlı et al. [24] determined the DR values of the tomato powder they produced using 7.5% aquafaba green pea powder as 0.15, 0.26 and 0.30 g moisture/g dry matter for temperatures of 50, 60 and 70 ºC, respectively.The reason why the DR data obtained in this study is lower than the DR data in the literature is due to the difference in the initial moisture content of the product, the physicochemical properties of the product and the carrier agent powder used.Samimi-Akhijahani and Arabhosseini [40] determined that the maximum DR values of the drying processes of tomatoes with slice thicknesses of 3, 5 and 7 mm with a solar type convective dryer with a sun tracking system were 0.1, 0.08 and 0.05 g moisture/g dry matter.min,respectively.It was observed that the ndings obtained in this study were compatible with the ndings in the literature.It was found that the DR values determined in microwave drying processes were higher than the DR values determined for convective methods.This is due to the fact that microwave energy produces heat directly in the product [31,18].They found that the DR values of the drying-densi cation processes of tomato residues using microwave and convective methods were higher in the microwave [29].

Effective moisture diffusion
Effective diffusion values of dried waste tomato purees are given in Table 2.  2, drying methods and carrier agent rates affected the effective diffusion values of the drying processes.It has been observed that the effective diffusion values of convective drying methods are higher than microwave drying methods [21].The reason for this is that microwave drying methods carry out the drying process by creating a pressure difference in the product, causing the moisture moving away from the product to move forward.This phenomenon caused the diffusion area of moisture to decrease and the effective diffusion value to be lower.Minaei et al. [30] dried pomegranate seeds as control and pre-treatment using vacuum, microwave and infrared methods.It was determined that the effective moisture diffusion for the drying methods varied between the values of 6.77-52.5×10− 10 m 2 /s, 3.43-29.19×10− 10 and 4-32×10 − 10 m 2 /s, respectively.It was observed that the relationship between the ndings in the literature and the ndings obtained within the scope of this study was similar.Al-Hilphy et al. [3] dried tomato slices in a convective dryer with a halogen lamp at temperatures of 60, 70 and 80 ºC.They reported that the effective moisture diffusion varies between 7.96×10 − 9 and 1.07×10 − 8 m 2 /s.It was observed that the ndings obtained within the scope of this study were compatible with the ndings in the literature.

Energy consumption values
SMER and SEC values of dried waste tomato puree are given in Fig.According to Fig. 3, drying methods and carrier agent rates affected the energy consumption analysis of waste tomato puree drying processes.SEC energy consumption values of convective drying methods were found to be higher than microwave drying methods [41].This has reduced the drying time in microwave drying methods, since the energy is generated directly in the dried product.Szadzińska et al.
[46] found in their drying study using convective and microwave methods that the total energy consumption was lower in microwave drying processes.Increasing the carrier agent ratio in the drying processes increased the SMER values and decreased the SEC values.Carrier agent improved the drying kinetics of waste tomato puree.Taşova and Öcalan [49] investigated the effect of different ratios of carrier agent in pumpkin residues on the SMER and SEC parameters of the drying processes.Within the scope of the study, increasing the carrier agent ratio decreased SMER values and SEC values.It has been observed that the relationship between the study conducted in the literature and the ndings obtained in this study is exactly the opposite.The reason for this is that the interaction between pumpkin residue and carrier agent and the interaction between waste tomato and carrier agent are different from each other.The VD method is more advantageous than the CD method in terms of SMER and SEC energy consumption parameters.The reason for this is that the total energy consumption value is lower in the VD method than in the CD method.Kaveh et al. [23] found that the SEC energy consumption values in the green pea drying processes they carried out with convective and vacuum methods were lower in the vacuum method.The reason for this is that due to the vacuum effective drying method, the drying time of the product is lower than the convective method.It has been observed that the MTCM method is more advantageous than the HD method in terms of energy consumption parameters.Although the drying time of the MTCM method was higher than the HD method, SMER values were found to be higher and SEC values were lower.The reason for this is that in the modi ed microwave dryer, when the product reaches the determined drying temperature, it automatically stops for a rest period (15 s).This phenomenon causes the total drying time to extend.Orikasa et al. [36] determined the total energy consumption values of tomato drying processes using vacuum-assisted microwave, microwave and convective methods as 1.352, 0.222 and 6.212 kWh, respectively.Within the scope of the study, the lowest energy consumption value was determined in the microwave drying method.This is due to microwave energy producing higher thermal energy in the product.While the total energy consumption for MTCM was determined as 0.751 kWh for 5% and 0.737 kWh for 10%, for HD these values were determined as 1.387 kWh for 5% and 1.228 kWh for 10%.

Exergy energy, e ciency and sustainabilityimprovement index values
Exergy energy, energy e ciency and sustainability index values of waste tomato puree drying processes are given in Table 3.  [42] found in their study that the maximum E xin value in the tomato drying process using a solar type dryer was 350 W. The reason why this value in the literature is higher than this study is that the drying time of the heat source in the solar dryer is long due to the uncontrolled rays coming from the sun.However, the heat insulation feature of the dryer and the fact that the tomato was dried in slices affected it.It was determined that the E xout values of the drying process of waste tomato puree varied between 3.1335-3.4253J/s.Sharma et al. [42] [42] reported that sustainability index and improvement index values ranged between 1.55-2.39and 0.006966-0.065984,respectively.It has been observed that the ndings in the literature are generally compatible with the ndings for the drying processes of waste tomato puree.It is thought that the detected differences are due to the moisture content of the products, their physical properties, type, technical and thermal differences of the dryers.

Conclusion
Waste tomato puree was converted into powder and dried using different methods for use.Different drying methods and carrier agent ratios were effective in changing the drying kinetics of waste tomato puree.The drying and moisture content of the products dried using microwave methods and 10% carrier agent rates reached the highest level.Convective drying methods were more average than microwave methods in terms of drying and moisture rates.Drying methods and carrier agent rates affected the effective moisture diffusion values of waste tomatoes.Effective moisture diffusion values determined in convective methods were found to be higher than microwave methods.Since the drying rate values determined in convective methods are lower than in microwave methods, it causes the moisture moving away from the product to spread over a wider area.With the increase in the carrier agent ratio, energy consumption parameters were positively affected.It has been found that microwave drying methods are more advantageous than convective methods in terms of determined energy consumption values.The VD method was found to be the most advantageous method among the drying processes in terms of exergy energy e ciency of dryers (3.7224), exergy energy e ciency of drying processes (0.8999) and sustainability index (0.9850) values.In the MTCM method, the improvement index (0.9103) was calculated to be higher than other dryers.Although more advantageous results were obtained in terms of drying kinetics and energy consumption parameters in the MTCM method, the improvement index was found to be higher.It has been observed that the use of this dryer in the production of waste tomato powder is su cient, but it is possible to obtain higher performance values by improving.

Con ict of interest
The author in the study has no con ict of interest with any other author.

Equation 1
was used to determine the moisture content of waste tomato purees according to dry basis (d.b.). 1 Here: Mi; Initial weight (g), Ml; nal weight (g), Nd.b: g moisture/g dry matter 2.5.Drying kinetics Equation 2 was used to determine the drying rates of waste tomato purees.DR

Figure 2 Dry kinetics of waste tomato puree Figure 3
Figure 2

Table 2
Effective diffusion values of waste tomato puree

Table 3
Exergy energy and exergy e ciency values of drying processes reported that E xout values of tomato drying processes varied between 0.41738-0.67141.In this study, it was determined that E xevap values varied between 10.9099-14.1691kJ/kg.Aviara et al.[4]Cassava starch was dried in a tray type oven at increasing temperatures up to 40-60 ºC.They found that the E xin and E xout energy values of the drying processes