Evaluation of engineering properties for waste control of tomato during harvesting and postharvesting

Abstract In Iran, more than 30% of agricultural products turn into waste at different stages from harvesting to consumption. Thus, main factors for performing of this present study are including of: (a) the importance of tomato as an agricultural product and (b) lack of information about reducing waste during tomato processing. In this study, some physical, nutritional, mechanical, and hydrodynamic properties of tomato were measured under standard conditions. Physical properties included the length, width, thickness, mean diameter (geometric and arithmetic), mass, volume, density, sphericity, surface area, and aspect ratio. Also, nutritional properties, moisture, dry matter, pH, total soluble solid (TSS), and titration acidity (TA) of tomato were evaluated. The mechanical properties of tomato (compression and shear) were measured using Instron instrument. The hydrodynamic properties were measured with water in transportation, separation, and sorting of tomatoes. The physical properties were including of length, width, thickness, mass, volume, and geometric and arithmetic mean diameters showed a direct relationship with the size of tomatoes. Also, volumetric mass (density) had an inverse relation with tomato size. Yield point and shear force were obtained 51.27 and 22.20 N, respectively. The nutritional properties such as pH value, TSS, and TA were equal to 4.22, 22.23οBrix, and 2%, respectively. The hydrodynamic properties of tomatoes such as the terminal velocity, the tomatoes' rise time in the water column, the buoyancy force, and the drag force were obtained to be equal to 0.05 m/s, 10.11 S, 0.52 N, and 0.17 N, respectively.

14.3 g, 12.3 ml, 29.4 mm, 2,743 mm 2 , and 74.5% for mean mass, volume, geometric mean diameter, surface area, and sphericity, respectively. Moghadam and Kheiralipour (2015) conducted a research on the physical and nutritional properties of the hawthorn fruit. They reported that some physical properties such as sphericity, surface area, and slenderness ratio were 1.13%, 1.69 mm, and 1.26, respectively. After studying the nutritional properties of the hawthorn fruit, they concluded that the TSS and TA were equal to 18.7% and 1.71%, respectively. Jahanbakhshi, Yeganeh, and Akhoundzadeh Yamchi (2016) studied the physical, mechanical, and hydrodynamic properties of scolymus. They reported that the scolymus density is less than water, and thus, it could be hydraulically sorted and transferred without any damage. The maximum force for bending and shearing the scolymus were 41.5 and 82.9 N, respectively. Moreover, in the assessment of hydrodynamic properties, the average terminal velocity for the scolymus was equal to 0.02 m/s. In investigation of the physical and mechanical properties of snake melon, Jahanbakhshi (2018) reported that length, width, thickness, surface area, and density are some of the physical characteristics that play an important role in many of the topics related to designing special machines or assessing materials' behavior when they are transferred. The maximum force for the pressure, bending, and shearing tests on the snake melon were 309. 66, 44.4, and 33.66 N, respectively. Singh and Reddy (2006) conducted a study about the postharvest mechanical properties of orange peel and fruit. They measured the shearing energy of the orange fruit and showed that increase in the storage period would reduce the amounts of force and energy required to shear oranges. Ince, Uğurluay, Güzel, and Özcan (2005) carried out a study on the flexural and shear properties of sunflower. They found out that increasing of moisture was caused to reduce shear modulus of elasticity and bending stress and increase shear energy. Kheiralipour (2008) studied the terminal velocity of two apple cultivars and reported that the fruits reached their terminal velocity at 5 s after release. Terminal velocity of fruits and Cereals small has an important role in designing the equipment for transportation of materials through wind or water, designing of fluidized bed dryers. Thus, researchers determined terminal velocity for different products such as pistachios and green peas (Kashaninejad & Tabil, 2009;Nimkar & Chattopadhyay, 2002).
Tomato is one of the plants which are sensitive to environmental stresses including of intensive temperature, high salinity, dryness, and environmental pollution. Therefore, according to different environmental stresses in different regions of Iran, various cultivars are planted in different areas. In Kermanshah province, tompler cultivar of tomato has been considered by farmers. However, due to lack of knowledge about the engineering properties of this product, its waste during the process of harvesting and after that is a matter worthy of attention and analysis. So, the importance of tomato as an agricultural product and lack of knowledge among Iranian farmers about how to reduce waste and process tomatoes are factors that motivate this study. Review of the previous literature revealed that prior studies had not researched the properties of this cultivar of tomatoes.

| Determination of physical properties
In this study, the tomatoes which had equal rates of ripeness were collected from a farm in Kermanshah province in Iran as the sample. Then, in order to prevent the initial moisture of the product, the sample was kept inside a refrigerator at the temperature of 4 ± 1°C and transferred from the storage environment (the refrigerator) to the laboratory about 2 hr before carrying out the tests. To determine the dimensions and mass of the samples under experiment, a digital caliper with the precision of 0.01 mm and a digital scale with the accuracy of 0.01 g were used. Geometric mean diameter (D g ), arithmetic mean diameter (D a ), and sphericity percentage (Ø) were calculated through Equations (1), (2), (3) (Mohsenin, 1986).
where L, W, and T were the length, width, and thickness of the tomatoes, respectively. S is the surface area (mm 2 ), and R a is the aspect ratio of the tomato were obtained through Equations (4) and (5) (Mohsenin, 1986).
The tomatoes mass was measured using a digital scale (GF600, USA). To determine the volume of the tomatoes, the platform method was used (Equation (6)) (Mohsenin, 1986).
The density of the tomatoes is obtained by Equation (7).
where W W is the density of the displaced water (g/cm 3 ), ρ W is the density of the water (g/cm 3 ), ρ t is the true density (g/cm 3 ), M is the mass (g), and V is the volume of the tomatoes (m 3 ).
Static friction coefficient (μ s ) of tomatoes was calculated by measuring the angle at which tomatoes started moving on four surfaces of galvanized, aluminum, wood, and rubber sheets. For measurement of this parameter, a metal rectangular cube whose both ends were open with the dimensions of 20 × 10 × 10 cm was placed on the given surface and filled with tomatoes. After that, the gradient of the surface under study was gradually increased and the rectangular cube started to move at a particular angle without being in contact with the surface. At that point, the tangent of the angle between the surface and the horizon (α) was taken as the static friction coefficient calculated through Equation (8) (Khazaei, Borghei, & Rasekh, 2003;Mohsenin, 1986).

| Determination of nutritional properties
Measurement of moisture content was done using the standard oven hot air method (Memmert UNE 500 model). For this purpose, 20 g samples of tomatoes were dried at an oven for 4 hr at the temperature of 105°C in three replications. Weight of samples was measured before and after being placed in the oven using a digital scale.
Then, the moisture content and dry matter of tomato fruit were calculated by Equations (9) and (10) Where MC is the moisture content of fruit (%), M W is the initial mass of fruit (g), M d is the mass of dried fruit (g), and DM is the dry matter fruit (%).
The pH of tomato juice was measured by pH meter (pH-200L model). The TA was measured using the titration method. 0.1 normal soda (NaOH) (5ml of tomato extract in 50 ml of distilled water) and the titration was operated until solution pH reached 8.2. The results were expressed as grams of malic acid per 100 g fresh weight. The TSS was measured for 10 tomatoes in Brix degrees using a refractometer instrument (model ATC-le manual model). Equations (11) and (12) were used to measure the TA and TSS TA ratio.
where TA is the titratable acidity (%), V b is the amount of soda in milliliters used for titration, N n is the normality of the soda consumed (N n = 0.1), E is the equivalent gram of the dominant acid, and V i is the volume of the sample tomato extract in milliliters.
where T is the TSS TA ratio, TSS is the total soluble solids (°Brix), and TA is the titratable acidity (%).

| Determination of mechanical properties
The mechanical properties of tomato fruit were including of compression and shear test. This test was performed using Instron machine (Z 0.5 model, country Germany). For compression test, the samples were placed on the flat plate and pressed with a  (Jahanbakhshi, 2018;Jahanbakhshi & Kheiralipour, 2019b). The Instron machine was simultaneously connected to a computer, and data mining was carried out (Figure 1).

| Determination of hydrodynamic properties
In determining, the hydrodynamic properties were measured in a plexiglas column with the base of 35 × 35 × 90 cm and the thickness of 8 mm. The sides of this column's base were set to fit standard sizes (Jahanbakhshi et al., 2016;Kheiralipour & Marzbani, 2016;Vanoni, 2006). The column was filled with water up to 80 cm of its height. Each tomato was placed on bottom of water by a nondestructive clamp. It was then released after the water became calm.
Immediately, a Sony (DSC-W710) digital camera was used to film the movement of each tomato from the beginning to the end with 30 frames per second ( Figure 2).  (Jahanbakhshi et al., 2016).
In that relation, N is the number of images for a tomato's movement at the vertical distance of 50 cm. where V is the volume of the tomato (m 3 ), g is the acceleration of gravity (m/s 2 ), and ρ w is the density of water (Kg/m 3 ). The drag force (F d ) is the force on the tomato in the opposite direction of its movement. Equation (15) was used to obtain this drag force. This relation clearly shows that when a tomato is in a static state, no drag force affects it but as soon as it starts moving, the drag force rises from zero, and when the tomato reaches its terminal velocity, the drag force reaches its maximum that equals: Where ρ w is the water's density (Kg/m 3 ), V t is the tomato's terminal velocity (m/s), C D is the drag coefficient, and A is the surface area of tomato (m 2 ). In Equation (15)

| Physical properties
The physical properties of tomato are reported in

| Nutritional properties
The nutritional properties of the tomato fruit are reported in Table 3.
The means for the moisture content and the dry matter of tomato fruit were 94.29 and 5.70 percent. In similar studies, researchers reported a moisture content is very important and influential in determination of physical and mechanical properties of fruits (Altuntaş & Yıldız, 2007;Gholmohammadi, Roghanipour, & Mesri Ghendishmin, 2013;Moghadam & Kheiralipour, 2015). The average pH, TSS, TA for the tomato juice were 4.22 and 22.23 ο Brix and 2%, respectively.
In addition, these data were used to obtain the TSS/TA ratio which was equal to 11.13. The properties mentioned above are very important in preserving the product after harvest, during storage and processing. A similar study conducted by Kheiralipour (2008

| Mechanical properties
The mechanical properties of the tomato fruit for compression test are reported in Table 4. The mean values of the properties measured in the compression test (elasticity module, the maximum force required [rupture force], deformation, energy) were 0.11 GPa,51.27 N,9.52 mm,and 202.38 N·mm, respectively. One of the most important factors in increasing agricultural waste is mechanical damage.
Therefore, in order to reduce tomato waste, the compressive forces caused by displacement and transportation are reduced to the lowest possible (<51.27 N). In a similar study, Jahanbakhshi and Ghamari (2015) investigated the mechanical properties of plum fruit. In a compression test, they reported the modulus of elasticity equal to 0.0118 GPa. As compared to the present study, it can be stated that tomato fruit has a higher modulus of elasticity (0.11 GPa) and, thus, it has a harder tissue.
Another mechanical property of the tomato fruit is the shear force that it is shown in

| Hydrodynamic properties
The hydrodynamic properties of tomato fruit are reported in Table 6. Other similar studies investigated terminal velocity and rise time for two apple cultivars, Redspar and Delbarstival, and modeled terminal velocity of kiwi fruit. Their results indicated that reducing the real density would increase the termination velocity (Kheiralipour, 2008;.

| CON CLUS ION
The first step in the codification of quality standards for agricultural products such as tomatoes as well as the improvement of different processing lines for this product is to know various properties of those products and their changes according to different factors.
This study investigated some physical, nutritional, mechanical, and hydrodynamic properties of tomato. The following findings and results could be reached at based on the present study: