# Life cycle assessment and energy comparison of aseptic ohmic heating and appertization of chopped tomatoes with juice

Sami Ghnimi, Amin Nikkhah, Jo Dewulf, Sam van Haute

► To cite this version:

Sami Ghnimi, Amin Nikkhah, Jo Dewulf, Sam van Haute. Life cycle assessment and energy comparison of aseptic ohmic heating and appertization of chopped tomatoes with juice. Scientific Reports, 2021, 11, pp.13041. 10.1038/s41598-021-92211-1. hal-03267348

HAL Id: hal-03267348

https://hal.science/hal-03267348

Submitted on 22 Jun 2021

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons CC0 - Public Domain Dedication 4.0 International License
<figure><img src="image_2.png" /></figure>

OPEN

# Life cycle assessment and energy comparison of aseptic ohmic heating and appertization of chopped tomatoes with juice

Sami Ghnimi<fnref n="1" />,²✉, Amin Nikkhah³,⁴✉, Jo Dewulf⁵ & Sam Van Haute³,⁴

The energy balance and life cycle assessment (LCA) of ohmic heating and appertization systems for processing of chopped tomatoes with juice (CTwJ) were evaluated. The data included in the study, such as processing conditions, energy consumption, and water use, were experimentally collected. The functional unit was considered to be 1 kg of packaged CTwJ. Six LCA impact assessment methodologies were evaluated for uncertainty analysis of selection of the impact assessment methodology. The energy requirement evaluation showed the highest energy consumption for appertization (156 kWh/t of product). The energy saving of the ohmic heating line compared to the appertization line is 102 kWh/t of the product (or 65% energy saving). The energy efficiencies of the appertization and ohmic heating lines are 25% and 77%, respectively. Regarding the environmental impact, CTwJ processing and packaging by appertization were higher than those of ohmic heating systems. In other words, CTwJ production by the ohmic heating system was more environmentally efficient. The tin production phase was the environmental hotspot in packaged CTwJ production by the appertization system; however, the agricultural phase of production was the hotspot in ohmic heating processing. The uncertainty analysis results indicated that the global warming potential for appertization of 1 kg of packaged CTwJ ranges from 4.13 to 4.44 kg CO₂eq. In addition, the global warming potential of the ohmic heating system ranges from 2.50 to 2.54 kg CO₂eq. This study highlights that ohmic heating presents a great alternative to conventional sterilization methods due to its low environmental impact and high energy efficiency.

## Abbreviations

CML Institute of environmental sciences

CO₂ Carbon dioxide

CTwJ Chopped tomatoes with juice

Eq Equivalent

FU Functional unit

FU Functional units

HPP High pressure processing

IPCC Intergovernmental panel on climate change

ISO International standardization organization

kg Kilogram

LCA Life cycle assessment

LCI Life cycle inventory

m³ Cubic meter

MJ Mega joule

PEF Pulsed electric fields

<footnote n="1">¹Université Claude Bernard Lyon 1, CNRS, LAGEPP UMR 5007, 43 Bd 11 Novembre 1918, 69622 Villeurbanne, France. ²ISARA Lyon, 23 rue Jean Baldissini, 69007 Lyon, France. ³Department of Food Technology, Safety and Health, Ghent University, Faculty of Bioscience Engineering, Ghent, Belgium. ⁴Department of Environmental Technology, Food Technology and Molecular Biotechnology, Ghent University Global Campus, Incheon, South Korea. ⁵Department of Green Chemistry and Technology, Ghent University, Coupure Links 653, 9000 Ghent, Belgium. ✉email: sghnimi@isara.fr; amin.nikkhah@ugent.be</footnote>
<table><caption>**Table 1.** Summary of the literature on the LCA of tomato processing.</caption><thead><tr><td>Product</td><td>The studied region</td><td>Functional unit</td><td>Impact assessment methodology</td><td>Focus of the research</td><td>Environmental hotspots</td><td>References</td></tr></thead><tbody><tr><td>Paste and diced tomatoes</td><td>United States</td><td>One kilogram of canned, consumer-ready tomato paste</td><td>Not available</td><td>The environmental consequences of regional and national-scale food systems</td><td>Processing and retail packaging</td><td>Brodt et al. (2013)<sup>58</sup></td></tr><tr><td>Chopped tomatoes and peeled tomatoes in tomato juice and tomato purée</td><td>Italy</td><td>One kg of packaged product</td><td>CML 2001</td><td>Environmental impacts of various tomato based products</td><td>Agricultural phase and packaging</td><td>Del Borghi et al. (2014)<sup>13</sup></td></tr><tr><td>Packaged tomato puree</td><td>Northern Italy</td><td>700 g puree jar</td><td>CED, CML 2001 and ReCiPe</td><td>Environmental impacts of various phases of packaged tomato puree production process</td><td>Packaging and agricultural phases</td><td>Manfredi and Vignali (2014)<sup>49</sup></td></tr><tr><td>Tomato puree</td><td>Northern Italy</td><td>One kg of tomato purée</td><td>ILCD method</td><td>Anaerobic digestion of by-products</td><td>Packaging and agricultural phases</td><td>Bacenetti et al. (2015)<sup>55</sup></td></tr><tr><td>Tomato juice</td><td>German Institute of Food Technologies, Germany</td><td>One kg of packaged tomato juice</td><td>Not available</td><td>Thermal, high pressure processing, and pulsed electric fields technologies compression</td><td>Packaging</td><td>Aganovic et al. (2017)<sup>59</sup></td></tr><tr><td>Packaged peeled tomatoes</td><td>Italy</td><td>1 kg of processed tomato</td><td>ReCiPe</td><td>Pulsed electric fields technology at an industrial scale</td><td>Canning</td><td>Arnal et al. (2018)<sup>50</sup></td></tr><tr><td>Fresh and dried organic tomato</td><td>Southern Sweden</td><td>One tonne</td><td>ReCiPe midpoint</td><td>Environmental impacts of fresh and dried tomato supply chain</td><td>Agricultural phase, packaging and drying</td><td>Bosona, and Gebresenbet, (2018)<sup>60</sup></td></tr><tr><td>Tomato puree</td><td>Iran</td><td>500 g packaged tomato puree in a steel can with a plastic cap</td><td>CML-IA baseline</td><td>Comparison of different tomato puree production phases</td><td>Packaging</td><td>Shahvarooghi Farahani et al. (2019)<sup>21</sup></td></tr><tr><td>Tomato-pasta sauce</td><td>The USA</td><td>1 kg product eaten at the consumer level</td><td>ReCiPe 2016</td><td>Cradle to grave environmental impact assessment</td><td>Processing and the agriculture phase</td><td>Parajuli et al. (2020)<sup>48</sup></td></tr><tr><td>Tomato ketchup</td><td>Austria</td><td>3.8 kg ketchup</td><td>Combination of a few methodologies</td><td>Packaging systems in the light of food waste</td><td>Packaging</td><td>Wohner et al. (2020)<sup>61</sup></td></tr><tr><td>Chopped tomatoes with juice</td><td>Italy</td><td>One kg of packaged CTwJ</td><td>CML-IA baseline, ILCD 2011 Midpoint, EDIP 2003, EDP 2013, ReCiPe midpoint, and IMPACT 2002+</td><td>Processing upon appreciation and ohmic heating systems</td><td>-</td><td>Current Study</td></tr></tbody></table>

SO₂ Sulfur dioxide

t Tonne

Wh Watt-hour

Life Cycle Assessment (LCA) is a recognized standardized methodology for examining environmental consequences in food systems. In recent years, this method has been applied to the environmental assessment of agricultural systems, such as apple¹, peanut², strawberry³, cacao⁴, kiwifruit⁵, canola⁶, tea⁷, peach⁸, apricot⁹, barley¹⁰, corn¹¹, and tobacco¹². However, there are few studies on the LCA of food processing systems, such as tomato-based product processing¹³, olive oil¹⁴, tea processing¹⁵, whole peeled canned tomato¹⁶, pasta production¹⁷, legume processing and packaging¹⁸, and apple juice¹⁹. Life cycle environmental impact assessment of food production (agricultural phase and processing) throughout its supply chain can improve the understanding of environmental impacts and determine the environmental hotspots of production systems.

In recent years, the development of an environmentally sustainable food supply chain has become important²⁰. In this regard, LCA can also help policymakers and managers produce their products in a more environmentally friendly manner. In this regard, tomato (*Lycopersicon esculentum*) is the second most important vegetable crop after potato, and the total worldwide tomato production was 182 million tons in 2017²¹. There are different tomato-based products, such as purée, paste, juice, chopped tomatoes, and peeled tomatoes in tomato juice, resulting in various processing systems.

The environmental impacts of the agricultural phase of tomato production have been widely investigated in different parts of the world, such as Australia²², Albania²³, Colombia²⁴, Iran²⁵,²⁶, Italy¹⁶,²⁷, Spain²⁸⁻³⁰, and Canada³¹. More information regarding the LCA studies on the agricultural phase of tomato production systems can be found in Pineda et al.³². However, there are a few published documents related to the LCA of different tomato processing systems. Table 1 displays a summary of the relevant literature on the LCA of tomato processing systems.

Industrial food processing is the second most notable phase of the food supply chain, accounting for 28% of the total energy use³³. Moreover, industrial production, together with logistics and packaging (beyond the farm gate), are responsible for approximately half of the total energy consumption in the food chain³³. The EU food industry is making significant contributions to improve energy efficiency while optimizing production processes through different approaches: (i) energy and heat recovery, (ii) selection of renewable energy sources to minimize
<figure><img src="image_3.png" /><figcaption>**Figure 1.** Appertization line with 6 t/h capacity, including pre-processing, canning, sterilization and cooling.</figcaption></figure>

the impact of energy consumed, and (iii) development and application of new sustainable “green and innovative” techniques in food processing. In comparison to conventional food processing technologies, green and innovative food processing technologies involve less processing time, reduced solvent and energy consumption, and a lower CO₂ footprint³⁴. The most common innovative thermal and non-thermal technologies in the food industry are ohmic heating, microwave heating, radiofrequency, high-pressure processing, and pulsed electric fields. Ohmic heating provides a rapid and uniform heating, consequentially reducing thermal damage compared to conventional heating and allows manufacturers to obtain high-quality products with minimum nutritional, sensorial, and structural changes³⁵. The conversion of electric energy into thermal energy during ohmic heating results in high energy efficiency (i.e., > 90%), which is considerably higher than those achieved by the traditional indirect heating technologies that rely on the burning of fuels, such as appertization, tubular heat exchangers, and plate heat exchangers³⁶,³⁷. In a study, Aganovic et al.³⁸ investigated the energy consumption and environmental life cycle of thermal, high-pressure processing (HPP), and pulsed electric field (PEF) technologies for tomato and watermelon preservation. The results indicated that the tomato juice farm-to-gate environmental impact was higher than that of watermelon juice, and the largest energy uptake was documented for HPP, followed by PEF and traditional thermal processing.

Italy leads tomato production in the EU with a share of 36%; the amount of total tomato production was 5.6 million tons (96% for processing) in 2015³⁹. Reviewing the related relevant literature, it has been highlighted that in-depth research has not yet been conducted on the environmental impacts of chopped tomatoes with juice (CTwJ) processing by conventional processing, including appertization and innovative electro-technology such as ohmic heating. Similarly, for energy efficiency, research studies focus only on specific unit operations and not on the entire processing line to determine energy consumption. Thus, this study aimed to perform an energy efficiency comparison (global line and thermal unit operations) and LCA of ohmic heating and appertization for CTwJ processing.

## Materials and methods

**Tomato processing.** Tomatoes (*Solanum lycopersicum* var. *Hybrid*) were grown in the Italian Puglia region. They were purchased and transported to processing plants located 160 km away and then processed at a local Italian factory. For the purpose of this study, the industrial appertization and aseptic ohmic heating units were selected as described in Figs. 1 and 2, respectively. The preparation processes (grading, washing, peeling, and dicing) were the same for both industrial lines. The tomatoes were peeled using a steam system (Cavalieri, Italy) under pressurized steam at 110 °C for 10 s, followed by mechanical separation of the peels. A linear dicer was used to cut tomatoes (Cavalieri, Italy). The tomatoes were first cut into 2 cm thick slices, and afterward to 1.7 cm-side cubes. Diced tomatoes and juice were mixed in a tank for approximately 10 min for further processing by appertization or ohmic heating. A volumetric pump was used to feed the ohmic heating and appertization units. This pump minimizes product damage and enables moving fluid-solid mixtures containing approximately 60% of diced tomatoes in 40% tomato juice. Figures 1 and 2 illustrate the system boundaries in CTwJ processing and packaging upon appertization and ohmic heating systems.
<figure><img src="image_4.png" /><figcaption>Figure 2. Aseptic Ohmic heating line with 4 t/h capacity, including pre-processing, preheating, sterilization, cooling and aseptic packaging.</figcaption></figure>

**Appertization line.** Diced tomatoes and juice were mixed in a tank for 10 min. They were pre-heated (ca. 60 °C) using direct steam injection before hot filling in tinplate cans. Cans sterilization was done using a tunnel sterilizer (Manzini, Italy) at 95 °C for 30 min with a production rate of 6 t/h of canned diced tomatoes with juice. The steam production system consists of firetube steam boilers (PB 100 model, Mingazzini, Parma, Italy) with a steam output of 10,000 kg/h and rated pressure of 12 bar.

**Aseptic ohmic heating line.** The process is based on the electrical resistance of the chopped tomato with the juice that is treated. Dissipation of the electrical energy when electric current flows through food leads to heat release (Joule effect)⁴⁰. Ohmic heating was conducted in an industrial-scale unit, consisting of one stage for pre-heating the CTwJ up to 75 °C and a subsequent stage for heating them up to 102 °C. It then enters the insulated holding tubes before being cooled in tubular heat exchangers (Tetra Pak, Denmark) up to 20 °C. After cooling, the product is pumped into the aseptic storage vessel prior to aseptic packaging in multi-layer plastic pouches. The total electrical power of the ohmic system was 240 kW, and the average product flowrate was 4 t/h. The flowrate was recorded using an electromagnetic flowmeter (EMC, Auckland, New Zealand) with a precision of within 1% of the full range. The bulk temperatures were measured using platinum resistance probes (Pt 100 Ω to 0 °C with a ±0.1 °C accuracy) placed at the inlet and outlet of each zone. Relative pressure was measured with manometers (JUMO, type 4AP30, Fulda, Germany) at the inlet and outlet of each zone with a precision of 0.1%. The power supply delivers bipolar potential pulses, and electrolysis is prevented by using a high-frequency alternating voltage⁴¹.

**Energy auditing.** Energy requirements were experimentally measured through energy auditing. Both processing lines were instrumented to determine thermal and electrical energy inputs and consumption.

The energy requirement for the appertization line encompasses the electricity used by conveyers, pumping systems, and line dicers; thermal energy is required for peeling, pre-heating prior to appertization, sterilization and cooling of the product.

The specific energy required for heating the cans ($E_c$) and their contents ($E_p$) was calculated using Eqs. (1) and (2), where $n_c$ is the number of cans per cycle, $m_c$ is the weight of empty cans, $m_p$ is the weight of the product per can, $C_{pc}$ is the specific heat of cans, $C_{pp}$ is the specific heat of the product, $T_c$ is the temperature of the cans, $T_p$ is the temperature of the product, and $T_s$ is the steam temperature inside the sterilizer:

$$E_c = n_c \times m_c \times C_{pc} \times (T_s - T_c) \quad (1)$$

$$E_p = n_c \times m_p \times C_{pp} \times (T_s - T_p) \quad (2)$$

The energy input in the tunnel sterilizer ($E_s$) was calculated using Eq. (3), with $\dot{m}_{vs}$ as the steam mass flowrate, and $h_{vs}$ is the specific enthalpy of steam:
$$E_s = \dot{m}_{vs}h_{vs} \qquad (3)$$

Ohmic heating occurs due to the electrical conductivity and ability of the electrical current to flow through it. The power clamp meter was connected to the electrical power supply to measure the given electrical power ($P_g$). The fraction of electrical power converted to thermal energy and dissipated in the product was calculated using Eq. (4), with $\dot{m}_{po}$ as the mass flowrate of the product in the ohmic heater, $C_{pp}$ is the specific heat of the product, $T_{pi}$ is the inlet temperature of the product, and $T_{po}$ is the outlet temperature of the product.

$$P_t = \dot{m}_{po} \times C_{pp} \times (T_{po} - T_{pi}) \qquad (4)$$

The energy required for final cooling prior to aseptic packaging was calculated using Eq. (5), where $\dot{m}_{wc}$ is the mass flowrate of cooling water, $C_{pw}$ is the specific heat of water, $T_{iw}$ is the inlet temperature water, and $T_{ow}$ is the outlet temperature of water in the heat exchanger:

$$P_t = \dot{m}_{wc} \times C_{pw} \times (T_{ow} - T_{iw}) \qquad (5)$$

**Software.** EDraw Max (ver. 9.1, 2018; Sheung Wan, Hong Kong) was used for the representation of the appertization and ohmic heating flowcharts. The LCA analysis was performed using the professional SimaPro software (ver. 8.1.0 Analyst) and adapted Ecoinvent 3.2 database.

**LCA methodology.** LCA is a standardized and widespread methodology to study environmental consequences associated with food$^{42}$. The LCA procedure is outlined by ISO 14040 and ISO 14044$^{43}$. A comprehensive LCA comprises four coherent and iterative phases (1) goal and scope definition, (2) life cycle inventory, (3) impact assessment, and (4) interpretation of the results.

*Definition of the goal and scope.* The objective of this study was to perform an attributional life cycle environmental assessment of CTwJ processing and packaging upon appertization and ohmic heating systems. The functional unit (FU) was considered as 1 kg of CTwJ, which is a single reference of the product, requiring 1.6 kg of fresh tomato. Mass-based FU is common in food processing LCA (see Table 1). Figures 1 and 2 illustrate the system boundaries in CTwJ processing and packaging for the appertization and ohmic heating systems.

*Life cycle inventory.* The inputs and outputs of the investigated system were quantified in the second phase of the LCA$^{44}$. The cradle-to-grave emissions were classified into background (off-site) and foreground (on-site) emissions$^{45}$. The background emissions include the emitted pollutants from the production of material inputs, for instance, the emissions released within the generation of electricity and natural gas. However, foreground emissions comprise the direct emissions from the consumption of inputs in the investigated factory, for instance, emissions released within the combustion of natural gas. The background's emissions coefficients, such as the emissions of electricity generation and distribution, were adapted from the Ecoinvent database.

*Life cycle impact assessment.* In the third phase of an LCA study, impact category selection and characterization are mandatory; however, normalization and weighing are optional$^{46}$. The IMPACT 2002+ methodology was applied as the baseline impact assessment methodology, given its inclusion of various impact and damage categories. It is also a combination hybrid IMPACT 2002, Eco-Indicator 99, CML, and IPCC.

**Uncertainty analysis of the impact assessment.** There are some sources of uncertainties affecting the LCA results, including data quality, scenarios, and mathematical models underlying the impact assessment methods$^{44,47}$. As shown in Table 1, studies on the LCA of tomato processing have employed different impact assessment methodologies (see Table 1). In this study, an uncertainty analysis was performed to investigate the effect of impact assessment selection on the LCA results of the case study. For this purpose, six impact assessment methodologies, i.e., EDIP 2003, CML IA baseline, EDP 2013, ILCD 2011 Midpoint, ReCiPe midpoint, and IMPACT 2002+ were considered to be evaluated by LCA. The analyses were conducted using SimaPro V8.0.3.14.

**Research involving plants.** Studies complied with local and national regulations for using plants.

## Results and discussion

**Energy auditing.** An overview of the energy and water requirements for the aseptic ohmic heating and appertization lines is presented in Table 2.

The global specific energies for appertization and ohmic heating industrial lines for pre-processing and processing of CTwJ were 156 and 54 kWh/t, respectively. The energy requirement for the appertization line encompasses the electricity consumed by conveyers, pumping systems, and line dicers; the thermal energy required for peeling, pre-heating prior to appertization, and the energy required for sterilization, cooling, and packing of the product. Energy uptake for the ohmic heating includes the electricity used by conveyers, pumping systems, and line dicers; thermal energy required for peeling, ohmic pre-heating and ohmic sterilization; and energy consumption for cooling and aseptic packaging of the final product. The energy saving of the ohmic heating line compared to the appertization line is 102 kWh/t of the product (or 65% energy saving).

The energy efficiencies of the appertization and ohmic heating systems are 25% and 77%, respectively. For ohmic heating, the electrical energy input is converted to thermal energy by the Joule effect, where the chopped
<table><caption>**Table 2.** Overview of energy and water consumption for producing 1 kg of CTwJ through industrial appertization and aseptic ohmic heating lines.</caption><thead><tr><th></th><th>Appertization line</th><th>Aseptic Ohmic heating line</th></tr></thead><tbody><tr><td><strong>Pre-processing</strong></td><td></td><td></td></tr><tr><td>Electricity, Wh/kg</td><td>0.23</td><td>0.19</td></tr><tr><td>Natural gas, m³/kg</td><td>7.92 × 10<sup>-4</sup></td><td>2.38 × 10<sup>-5</sup></td></tr><tr><td>Water, m³/kg</td><td>0.37</td><td>0.34</td></tr><tr><td><strong>Processing</strong></td><td></td><td></td></tr><tr><td>Electricity, Wh/kg</td><td>3.19</td><td>53.97</td></tr><tr><td>Natural gas, m³/kg</td><td>1.48 × 10<sup>-2</sup></td><td>–</td></tr><tr><td>Water, m³/kg</td><td>1.32</td><td>1.35</td></tr></tbody></table>

<table><caption>**Table 3.** Characterization indices for tomato juice production.</caption><thead><tr><th>Impact category</th><th>Unit</th><th>Appertization</th><th>Ohmic heating</th></tr></thead><tbody><tr><td>Global warming</td><td>kg CO<sub>2</sub> eq</td><td>4.38</td><td>2.52</td></tr><tr><td>Mineral extraction</td><td>MJ surplus</td><td>67.11</td><td>0.02</td></tr><tr><td>Non-renewable energy</td><td>MJ primary</td><td>52.15</td><td>24.94</td></tr><tr><td>Ozone layer depletion</td><td>kg CFC-11 eq</td><td>1.34 × 10<sup>-7</sup></td><td>4.00 × 10<sup>-8</sup></td></tr><tr><td>Ionizing radiation</td><td>Bq C-14 eq</td><td>55.49</td><td>10.96</td></tr><tr><td>Respiratory organics</td><td>kg C<sub>2</sub>H<sub>4</sub> eq</td><td>0.0019</td><td>0.001</td></tr><tr><td>Respiratory inorganics</td><td>kg PM<sub>2.5</sub> eq</td><td>0.01</td><td>0.002</td></tr><tr><td>Non-carcinogens</td><td>kg C<sub>2</sub>H<sub>3</sub>Cl eq</td><td>0.11</td><td>0.03</td></tr><tr><td>Carcinogens</td><td>kg C<sub>2</sub>H<sub>3</sub>Cl eq</td><td>0.08</td><td>0.03</td></tr><tr><td>Aquatic ecotoxicity</td><td>kg TEG water</td><td>1943.03</td><td>505.51</td></tr><tr><td>Terrestrial acid/nutri</td><td>kg SO<sub>2</sub> eq</td><td>0.15</td><td>0.029</td></tr><tr><td>Terrestrial ecotoxicity</td><td>kg TEG soil</td><td>526.11</td><td>161.90</td></tr><tr><td>Aquatic acidification</td><td>kg SO<sub>2</sub> eq</td><td>0.06</td><td>0.01</td></tr><tr><td>Aquatic eutrophication</td><td>kg PO<sub>4</sub> P-lim</td><td>0.0006</td><td>0.0003</td></tr><tr><td>Land occupation</td><td>m<sup>2</sup>org.arable</td><td>0.20</td><td>0.09</td></tr></tbody></table>

tomato with juice behaves like a resistor in an electrical circuit. Energy losses in the ohmic heating system are mainly due to the pre-processing step and the cooling of the product during the holding phase between ohmic pre-heating and ohmic heating steps of the product; this temperature gradient was around 4.5 °C. Adding thermal insulation to this holding zone will improve the energy efficiency of the ohmic heating system.

Energy losses in the appertization line are mainly due to the lack of insulation, lack of reuse of steam condensate, and non-condensation of part of the injected steam. Steam condensate could be reused to heat feedwater for the steam boiler, pre-heat utilities, or clean equipment. Another major reason is the non-synchronization of the cans flow rates between the filling and retorting levels, which induces a continuous injection of steam in the retort even with a low load of cans. This situation leads to large energy losses due to the high steam consumption. This low efficiency can be improved by installing a steam regulation in the retort, which will provide the required steam flow depending on the load of the cans.

**Interpretation of LCA results.** Table 3 displays the characterization indices for CTwJ production. The global warming potential, ozone layer depletion, and non-renewable energy consumption for 1 kg production of packaged CTwJ for the appertization system were determined to be 4.38 kg CO₂eq, 1.34 × 10⁻⁷ kg CFC-11 eq, and 52.15 MJ, respectively. However, the aforementioned amounts for 1 kg of packaged CTwJ production upon the ohmic heating system were 2.52 kg CO₂eq, 4.00 × 10⁻⁸ kg CFC-11 eq, and 24.94 MJ, respectively. The results clearly showed that the environmental impacts of CTwJ processing and packaging on appertization were higher than those of ohmic heating systems. In other words, CTwJ production by the ohmic heating system was more environmentally efficient. The global warming potential of tomato sauce production was reported to be 1.5 kg CO₂eq⁴⁸.

Figures 3 and 4 illustrate the share of inputs in environmental burdens of CTwJ production upon appertization and ohmic heating systems, respectively. The results indicated that the tin production phase was the hotspot in CTwJ production by the appertization system. The agricultural phase was the second main contributor to the most impacted categories. More specifically, the agricultural phase of tomato production and tin packaging accounted for 54.33% and 45.00% of the total global warming potential of CTwJ production, respectively. The results are in line with the study of Manfredi and Vignali⁴⁹, which indicated that packaging was the main
<figure><img src="image_5.png" /><figcaption>**Figure 3.** Inputs contribution to the environmental impact of tomato juice production upon appertization.</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>**Figure 4.** Inputs contribution to the environmental impact of tomato juice production upon ohmic heating.</figcaption></figure>

contributor to most impact categories for tomato purée production in a glass jar. Arnal et al.⁵⁰ also highlighted that canning was the largest contributor to the total industrial-scale environmental impacts of packaged peeled tomato production systems. Packaging was reported to be responsible for the environmental impacts within all selected impact categories of tomato purée production, except for acidification and eutrophication⁵¹. Del Borghi et al.¹³ showed that packaging and agricultural phases had the highest adverse impacts on the environment during the production of 13 different tomato processed products. Many studies have also reported that the packaging phase is an environmental hotspot during the production of some other processed food products, such as dairy products⁵², and canned sardine⁵³.

The results highlight the important contributions of the agricultural phase in the ohmic heating system in the most impacted categories. The agricultural phase accounted for 94.44% of the total global warming potential of CTwJ production by the ohmic heating system. In other words, the consumption of inputs, such as diesel fuel and chemical fertilizer cause a huge negative environmental impact during the CTwJ production supply chain.

Figure 5 and 6 show the normalized damage assessment of CTwJ processing and packaging upon appertization and ohmic heating systems, respectively. The largest adverse environmental impact belonged to the human health damage category upon CTwJ production in both systems. The direct emissions of fossil fuels during the tomato production supply chain play a key role in the human health damage category. The resources damage category was placed as the second damage category with higher adverse environmental impacts in packed CTwJ production.
<figure><img src="image_7.png" /><figcaption>**Figure 5.** Normalized values of input damages in CTwJ processing and packaging for the appertization system.</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>**Figure 6.** Normalized values of inputs damages in CTwJ processing and packaging for the ohmic heating system.</figcaption></figure>

Figure 7 illustrates the normalized damage assessment of CTwJ processing and packaging for appertization and ohmic heating systems. The normalized damage assessment of CTwJ processing and packaging for the appertization system was higher than the ohmic heating system in all impact categories. So, the packed CTwJ for the ohmic heating system was more environmentally friendly. An LCA study on tomato processing also indicated that the application of PEF technology could mitigate environmental impacts⁵⁰.

**Uncertainty analysis of the impact assessment.** Table 4 illustrates the indicators of CTwJ production for different impact assessment methodologies. The obtained results help to compare the results of this study
<figure><img src="image_9.png" /><figcaption>**Figure 7.** Normalized damage assessment of tomato juice processing and packaging for appertization and ohmic heating systems.</figcaption></figure>

<table><caption>**Table 4.** Total characterized indicators of CTwJ within the selected impact assessment methodologies.</caption><thead><tr><th rowspan="2">Impact assessment</th><th colspan="2">Global warming (kg CO<sub>2</sub>eq)</th><th colspan="2">Ozone layer depletion (kg CFC-11 eq)</th></tr><tr><th>Appertization</th><th>Ohmic heating</th><th>Appertization</th><th>Ohmic heating</th></tr></thead><tbody><tr><td>CML-IA baseline</td><td>4.44</td><td>2.50</td><td>1.34 × 10<sup>-7</sup></td><td>4.00 × 10<sup>-8</sup></td></tr><tr><td>EDIP 2003</td><td>4.44</td><td>2.50</td><td>1.34 × 10<sup>-7</sup></td><td>4.00 × 10<sup>-8</sup></td></tr><tr><td>EDP (2013)</td><td>4.44</td><td>2.50</td><td>1.34 × 10<sup>-7</sup></td><td>4.00 × 10<sup>-8</sup></td></tr><tr><td>ILCD 2011 Midpoint</td><td>4.44</td><td>2.50</td><td>1.33 × 10<sup>-7</sup></td><td>3.99 × 10<sup>-8</sup></td></tr><tr><td>ReCiPe midpoint</td><td>4.13</td><td>2.54</td><td>1.35 × 10<sup>-7</sup></td><td>4.03 × 10<sup>-8</sup></td></tr><tr><td>IMPACT 2002+</td><td>4.38</td><td>2.52</td><td>1.34 × 10<sup>-7</sup></td><td>4.00 × 10<sup>-8</sup></td></tr></tbody></table>

with those published on LCA tomato-based products. The results showed that the global warming potential of 1 kg of packaged CTwJ ranges from 4.13 to 4.44 kg CO₂eq, within the appertization line. In addition, the global warming potential of the ohmic heating system ranges from 2.50 to 2.54 kg CO₂eq. The results also indicated that the ozone layer depletion for the production of 1 kg of packaged CTwJ ranges from 1.33 × 10⁻⁷ to 1.35 × 10⁻⁷ kg CFC-11 eq; however, this value for ohmic heating systems ranges from 3.99 × 10⁻⁸ to 4.03 × 10⁻⁸.

**Mitigation strategies.** As previously mentioned, packaging and agricultural phases were the environmental hotspots in both systems. One solution to reduce the environmental burdens of tomato product processes is related to the packaging phase; it could be weight reduction⁴⁹, and transitioning to packaging materials with less environmental impacts, such as bio-based packaging¹³,⁵¹. Therefore, the mitigation of the environmental impacts of tomato cultivation, replacing the packaging materials with bio-based materials, and using the by-products of cultivation and processing for supplying a part of the energy requirement can be considered as the main strategy for environmental impact mitigation of the CTwJ production supply chain. In the case of agricultural phase of CTwJ supply chain, Muñoz et al.²⁸ highlighted that the environmental impacts of 1 kg of tomato production in a greenhouse is less than that of an open field system due to the efficient use of water, fertilizers, and pesticides. A study compared three tomato farming systems (open field, greenhouse, and hydroponic) in terms of energy use patterns and concluded that the hydroponic system was the most environmentally friendly system⁵⁴. Bojacá et al.²⁴ believed that the implementation of integrated pest management programs could mitigate the environmental impacts of Colombian greenhouse tomato production. Bacenetti et al.⁵⁵ compared the two scenarios of the tomato purée production supply chain. In the first scenario, tomato by-products were sent back to the farms as bio-fertilizers; in the second scenario, the by-products were used in terms of biogas generation. The results showed that the second scenario was more environmentally efficient.
Moreover, there are some measures which can be taken in to consideration in order to mitigate the environmental impacts of CTwJ processing. For instance, a study focusing on the valorization of tomato by-products (tomato seeds and peels) highlighted the potential application of whole tomato by-products for valuable compound recovery and sequential low-cost biosorbent production⁵⁶. Winans et al.⁵⁷ applied LCA to study the diced tomatoes and paste production systems in California over a 10-year timeframe. They showed that the introduction of renewables in the life cycle of the production systems, such as solar-powered irrigation pumps, and on-site solar energy generation for facilities can mitigate the GWP impacts by 9–10%.

## Conclusions

This is the first study to compare the energy requirement and life cycle environmental impact of a novel food processing technology (ohmic heating) with a conventional method (appertization) in the tomato processing industry, considered one of the largest food processing industries worldwide. Moreover, uncertainty analysis was performed through the application of six different impact assessment methodologies.

The energy requirement evaluation showed the highest energy consumption for appertization (156 kWh/t of product). The energy saving of the ohmic heating line compared to the appertization line was 102 kWh/t of the product (or 65% energy saving). The energy efficiencies of the appertization and ohmic heating systems are 25% and 77%, respectively. There are opportunities for energy optimization of the investigated processes while maintaining the potential quality benefit. In the appertization system, a more energy-efficient process could be obtained by reducing steam non-condensation and installing a steam regulation, which will give the necessary steam flow depending on the load of the cans. In the case of ohmic heating, adding thermal insulation to the holding zone will improve the energy efficiency of the system.

From the LCA perspective, the uncertainty analysis results suggested that the global warming potential of the production of 1 kg of packaged CTwJ ranges from 4.13 to 4.44 kg CO₂eq. In addition, the global warming potential of the ohmic heating system ranges from 2.54 to 2.78 kg CO₂eq. Overall, CTwJ production by the ohmic heating system was more environmentally efficient than traditional retort canning.

Given this study was conducted on an industrial scale, the effect of influencing variables in the manufacture process of CTwJ production was not optimized. Therefore, further research is needed to optimize the processes in terms of energy and environmental impacts. In addition, replacing the packaging materials with bio-based materials, and using the by-products of cultivation and processing for supplying a part of the energy requirement, on the final energy and environmental impacts of CTwJ production should be further explored.

Received: 12 February 2021; Accepted: 7 June 2021

Published online: 22 June 2021

## References

1. Keyes, S., Tyedmers, P. & Beazley, K. Evaluating the environmental impacts of conventional and organic apple production in Nova Scotia, Canada, through life cycle assessment. *J. Clean. Prod.* **104**, 40–51 (2015).

2. Nikkhah, A., Khojastehpour, M., Emadi, B., Taheri-Rad, A. & Khorramdel, S. Environmental impacts of peanut production system using life cycle assessment methodology. *J. Clean. Prod.* **92**, 84–90 (2015).

3. Tabatabaie, S. M. H. & Murthy, G. S. Cradle to farm gate life cycle assessment of strawberry production in the United States. *J. Clean. Prod.* **127**, 548–554 (2016).

4. Utomo, B., Prawoto, A. A., Bonnet, S., Bangviwat, A. & Gheewala, S. H. Environmental performance of cocoa production from monoculture and agroforestry systems in Indonesia. *J. Clean. Prod.* **134**, 583–591 (2016).

5. Nikkhah, A. et al. Integration of life cycle assessment and Cobb–Douglas modeling for the environmental assessment of kiwifruit in Iran. *J. Clean. Prod.* **137**, 843–849 (2016).

6. Mousavi-Avval, S. H. et al. Application of multi-objective genetic algorithms for optimization of energy, economics and environmental life cycle assessment in oilseed production. *J. Clean. Prod.* **140**, 804–815 (2017).

7. Kouchaki-Penchah, H., Nabavi-Pelesaraei, A., O'Dwyer, J. & Sharifi, M. Environmental management of tea production using joint of life cycle assessment and data envelopment analysis approaches. *Environ. Prog. Sustain. Energy* **36**(4), 1116–1122 (2017).

8. Nikkhah, A., Royan, M., Khojastehpour, M. & Bacenetti, J. Environmental impacts modeling of Iranian peach production. *Renew. Sustain. Energy Rev.* **75**, 677–682 (2017).

9. Pergola, M. et al. A comprehensive Life Cycle Assessment (LCA) of three apricot orchard systems located in Metapontino area (Southern Italy). *J. Clean. Prod.* **142**, 4059–4071 (2017).

10. Tricase, C., Lamonaca, E., Ingrao, C., Bacenetti, J. & Giudice, A. L. A comparative Life Cycle Assessment between organic and conventional barley cultivation for sustainable agriculture pathways. *J. Clean. Prod.* **172**, 3747–3759 (2018).

11. Lee, E. K. et al. Projecting life-cycle environmental impacts of corn production in the US Midwest under future climate scenarios using a machine learning approach. *Sci. Total Environ.* **714**, 136697 (2020).

12. Mirkarimi, S. R., Ardakani, Z. & Rostamian, R. Economic and environmental assessment of tobacco production in Northern Iran. *Ind. Crops Prod.* **161**, 113171 (2021).

13. Del Borghi, A., Gallo, M., Strazza, C. & Del Borghi, M. An evaluation of environmental sustainability in the food industry through Life Cycle Assessment: The case study of tomato products supply chain. *J. Clean. Prod.* **78**, 121–130 (2014).

14. Tsarouhas, P., Achillas, C., Aidonis, D., Folinas, D. & Maslis, V. Life Cycle Assessment of olive oil production in Greece. *J. Clean. Prod.* **93**, 75–83 (2015).

15. Khanali, M., Mobli, H. & Hosseinzadeh-Bandbafha, H. Modeling of yield and environmental impact categories in tea processing units based on artificial neural networks. *Environ. Sci. Pollut. Res.* **24**(34), 26324–26340 (2017).

16. Garofalo, P., D'Andrea, L., Tomaiuolo, M., Venezia, A. & Castrignanò, A. Environmental sustainability of agri-food supply chains in Italy: The case of the whole-peeled tomato production under life cycle assessment methodology. *J. Food Eng.* **200**, 1–12 (2017).

17. Heidari, M. D. et al. Regionalised life cycle assessment of pasta production in Iran: Damage to terrestrial ecosystems. *J. Clean. Prod.* **159**, 141–146 (2017).

18. Del Borghi, A., Strazza, C., Magrassi, F., Taramasso, A. C. & Gallo, M. Life Cycle Assessment for eco-design of product-package systems in the food industry—The case of legumes. *Sustain. Prod. Consum.* **13**, 24–36 (2018).

19. Khanali, M. et al. Energy flow modeling and life cycle assessment of apple juice production: Recommendations for renewable energies implementation and climate change mitigation. *J. Clean Prod.* **246**, 118997 (2020).
20. De Marco, I. & Iannone, R. Production, packaging and preservation of semi-finished apricots: A comparative Life Cycle Assessment study. *J. Food Eng.* **206**, 106–117 (2017).

21. Anwar, R., Fatima, T. & Mattoo, A. Tomatoes: A model crop of solanaceous plants. In *Oxford Research Encyclopedia of Environmental Science* https://doi.org/10.1093/acrefore/9780199389414.013.223 (2019).

22. Page, G., Ridoutt, B. & Bellotti, B. Carbon and water footprint tradeoffs in fresh tomato production. *J. Clean. Prod.* **32**, 219–226 (2012).

23. Canaj, K., Mehmeti, A., Cantore, V. & Todorović, M. LCA of tomato greenhouse production using spatially differentiated life cycle impact assessment indicators: An Albanian case study. *Environ. Sci. Pollut. Res.* **27**(7), 6960–6970 (2020).

24. Bojacá, C. R., Wyckhuys, K. A. & Schrevens, E. Life cycle assessment of Colombian greenhouse tomato production based on farmer-level survey data. *J. Clean. Prod.* **69**, 26–33 (2014).

25. Khoshnevisan, B., Rafiee, S., Omid, M., Mousazadeh, H. & Clark, S. Environmental impact assessment of tomato and cucumber cultivation in greenhouses using life cycle assessment and adaptive neuro-fuzzy inference system. *J. Clean. Prod.* **73**, 183–192 (2014).

26. Pishgar-Komleh, S. H. et al. Integration of life cycle assessment, artificial neural networks, and metaheuristic optimization algorithms for optimization of tomato-based cropping systems in Iran. *Int. J. Life Cycle Assess.* **25**(3), 620–632 (2020).

27. Ronga, D. et al. Carbon footprint and energetic analysis of tomato production in the organic vs the conventional cropping systems in Southern Italy. *J. Clean. Prod.* **220**, 836–845 (2019).

28. Muñoz, P. et al. Comparing the environmental impacts of greenhouse versus open-field tomato production in the Mediterranean region. In *International Symposium on High Technology for Greenhouse System Management: Greensys 2007*, 801, 1591–1596 (2007).

29. Antón, A. et al. Improvement of agricultural life cycle assessment studies through spatial differentiation and new impact categories: Case study on greenhouse tomato production. *Environ. Sci. Technol.* **48**(16), 9454–9462 (2014).

30. Neira, D. P., Montiel, M. S., Cabeza, M. D. & Reigada, A. Energy use and carbon footprint of the tomato production in heated multi-tunnel greenhouses in Almeria within an exporting agri-food system context. *Sci. Total Environ.* **628**, 1627–1636 (2018).

31. Maham, S. G., Rahimi, A., Subramanian, S. & Smith, D. L. The environmental impacts of organic greenhouse tomato production based on the nitrogen-fixing plant (Azolla). *J. Clean. Prod.* **245**, 118679 (2020).

32. Pineda, I. T., Lee, Y. D., Kim, Y. S., Lee, S. M. & Park, K. S. Review of inventory data in life cycle assessment applied in production of fresh tomato in greenhouse. *J. Clean. Prod.* **282**, 124395 (2020).

33. Monforti-Ferrario, F. et al. Energy use in the EU food sector: State of play and opportunities for improvement (Publications Office of the European Union, 2015).

34. Misra, N. N. et al. Landmarks in the historical development of twenty first century food processing technologies. *Food Res. Int.* **97**, 318–339 (2017).

35. Ghnimi, S., Delaplace, G. & Filla上海, L. Tubular and fluid jet units. In *Ohmic Heating in Food Processing, Electro-Technologies for Food Processing Series* (CRC Press (Taylor & Francis Group), 2014).

36. Ramaswamy, H. S., Marcotte, M., Sastry, S. & Abdelrahim, K. Ohmic heating for food processing (2016). https://doi.org/10.1201/b12112-22.

37. Yildiz, H. & Guven, E. Industrial applications and potential use of ohmic heating for fluid foods. *Bulgar. Chem. Commun.* **46**, 98–102 (2014). http://bcc.bas.bg/BCC_Volumes/Volume_46_Special_B_2014/BCC-46-B-98-102.pdf.

38. Aganovic, K. et al. Pilot scale thermal and alternative pasteurization of tomato and watermelon juice: An energy comparison and life cycle assessment. *J. Clean. Prod.* **141**, 514–525 (2017).

39. Costa, J. M. & Heuvelink, E. *The global tomato industry*. Tomatoes 1–26 (CABI, 2018).

40. Ghnimi, S., Zaid, I., Maingonnat, J. F. & Delaplace, G. Axial temperature profile of ohmically heated fluid: Analytical model and experimental validation. *Chem. Eng. Sci.* **64**(13), 3188–3196 (2009).

41. Ghnimi, S., Flach-Malaspina, N., Dresh, M., Delaplace, G. & Maingonnat, J. F. Design and performance evaluation of an ohmic heating unit for thermal processing of highly viscous liquids. *Chem. Eng. Res. Des.* **86**, 627–632 (2008).

42. Nikkhah, A. Life cycle assessment of the agricultural sector in Iran (2007–2014). *Environ. Prog. Sustain. Energy* **37**(5), 1750–1757 (2018).

43. Collotta, M. et al. Comparative LCA of three alternative technologies for lipid extraction in biodiesel from microalgae production. *Energy Procedia* **113**, 244–250 (2017).

44. Rafiee, S. et al. Sustainability evaluation of pasteurized milk production with a life cycle assessment approach: An Iranian case study. *Sci. Total Environ.* **562**, 614–627 (2016).

45. Paramesh, V., Arunachalam, V., Nikkhah, A., Das, B. & Ghnimi, S. Optimization of energy consumption and environmental impacts of arecanut production through coupled data envelopment analysis and life cycle assessment. *J. Clean. Prod.* **203**, 674–684 (2018).

46. Dong, Y. H. & Ng, S. T. A life cycle assessment model for evaluating the environmental impacts of building construction in Hong Kong. *Build. Environ.* **89**, 183–191 (2015).

47. Nikkhah, A., Firouzi, S., Dadaei, K. & Van Haute, S. Measuring circularity in food supply chain using life cycle assessment; Refining Oil from Olive Kernel. *Foods* **10**(3), 590 (2021).

48. Parajuli, R., Matlock, M. D. & Thoma, G. Cradle to grave environmental impact evaluation of the consumption of potato and tomato products. *Sci. Total Environ.* **758**, 143662 (2021).

49. Manfredi, M. & Vignali, G. Life cycle assessment of a packaged tomato puree: A comparison of environmental impacts produced by different life cycle phases. *J. Clean. Prod.* **73**, 275–284 (2014).

50. Arnal, Á. J. et al. Implementation of PEF treatment at real-scale tomatoes processing considering LCA methodology as an innovation strategy in the agri-food sector. *Sustainability* **10**(4), 979 (2018).

51. Shahvarooghi Farahani, S. S., Soheilifard, F., Raini, M. G. N. & Kokei, D. Comparison of different tomato puree production phases from an environmental point of view. *Int. J. Life Cycle Assess.* **24**(10), 1817–1827 (2019).

52. Djekic, I., Miocinovic, J., Tomasevic, I., Smigic, N. & Tomic, N. Environmental life-cycle assessment of various dairy products. *J. Clean. Prod.* **68**, 64–72 (2014).

53. Almeida, C., Vaz, S. & Ziegler, F. Environmental life cycle assessment of a canned sardine product from Portugal. *J. Ind. Ecol.* **19**(4), 607–617 (2015).

54. Platis, D. P. et al. Analysis of energy and carbon and blue water footprints in agriculture: A case study of tomato cultivation systems. *Euro-Mediterr. J. Environ. Integr.* **6**(1), 1–10 (2021).

55. Bacenetti, J., Duca, D., Negri, M., Fusi, A. & Fiala, M. Mitigation strategies in the agro-food sector: The anaerobic digestion of tomato puree by-products. An Italian case study. *Sci. Total Environ.* **526**, 88–97 (2015).

56. Azabou, S., Louati, I., Taheur, F. B., Nasri, M. & Mechichi, T. Towards sustainable management of tomato pomace through the recovery of valuable compounds and sequential production of low-cost biosorbent. *Environ. Sci. Pollut. Res.* **27**(31), 39402–39412 (2020).

57. Winans, K., Brodt, S. & Kendall, A. Life cycle assessment of California processing tomato: An evaluation of the effects of evolving practices and technologies over a 10-year (2005–2015) timeframe. *Int. J. Life Cycle Assess.* **25**(3), 538–547 (2020).

58. Brodt, S., Kramer, K. J., Kendall, A. & Feenstra, G. Comparing environmental impacts of regional and national-scale food supply chains: A case study of processed tomatoes. *Food Policy* **42**, 106–114 (2013).

59. Filla上海, L. & Ghnimi, S. Energy efficiency and control of ohmic heating process. In *Ohmic Heating in Food Processing, Electro-Technologies for Food Processing Series* (CRC Press (Taylor & Francis Group), 2014).
60. Bosona, T. & Gebresenbet, G. Life cycle analysis of organic tomato production and supply in Sweden. *J. Clean. Prod.* **196**, 635–643 (2018).

61. Wohner, B., Gabriel, V. H., Krenn, B., Krauter, V. & Tacker, M. Environmental and economic assessment of food-packaging systems with a focus on food waste. Case study on tomato ketchup. *Sci. Total Environ.* **738**, 139846 (2020).

## Acknowledgements

The authors would like to acknowledge the support received from Ghent University Global Campus.

## Author contributions

S.G. developed the initial concept of the research and contributed to the data collection, energy analysis, and manuscript writing and editing. A.N. contributed to the development of the initial concept, LCA analysis and writing of the first draft of the manuscript. J.D. contributed to the validation of the results, manuscript writing and editing. S.V. contributed to the concept, and editing of the article.

## Competing interests

The authors declare no competing interests.

## Additional information

Correspondence and requests for materials should be addressed to S.G. or A.N.

Reprints and permissions information is available at www.nature.com/reprints.

**Publisher's note** Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

<figure><img src="image_10.png" /></figure>

**Open Access** This article is licensed under a Creative Commons Attribution 4.0 International

License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

© The Author(s) 2021