Articles
Effect of refrigeration system on apple fruit preservation, mass loss and in-situ metabolism activity during CA storage
Article number
1456_24
Pages
185 – 192
Language
English
Abstract
Following the adoption of the EU F-Gas regulation aimed at phasing out HFC refrigerants due to their high global warming potential (GWP), commercial fruit storage facilities are mandated to transition to environmentally friendly alternatives.
However, to date, there has been a lack of comprehensive studies conducted on a commercial scale comparing the alternative refrigerants CO2 (R744) and propane (R290) regarding their suitability for apple fruit storage.
In this project, new refrigeration systems were installed in identical storage rooms with a capacity of 50 t, utilizing R290 (indirect evaporative cooling) and R744 (direct) as refrigerants.
In two experiment seasons, both storage rooms were filled over a 10-to-14-day period with homogeneous fruit material and cooled to 1°C. Subsequently, controlled atmosphere (CA) conditions were established (1.0 kPa O2,<0.7 kPa CO2 in 2023 and 1.2 kPa CO2 in 2024). For the assessment of each refrigeration system, the stability of climate control of each room during long-term storage (6 to 8 months) was evaluated and correlated with analyses of fruit quality, e.g., mass loss, softening rate, acid and peel yellowing, physiological disorders.
Furthermore, the metabolism activity of the fruit material in terms of CO2 production rate was monitored in-situ during storage.
Metabolic activity and associated quality‐parameter change rates were comparable between the two refrigeration systems.
Nevertheless, the room cooled with indirect R290 system exhibited significantly higher fruit mass loss than the R744 cooled room, most likely due to less stable temperature and relative humidity conditions.
Mass loss also varied markedly by bin position within the storage room and by apple cultivar.
Although these findings conflict with previous reports and require further validation, they highlight that economic evaluations of alternative refrigeration systems must consider not only capital and operating costs but also the impacts on the stored commodity.
Given the pronounced disparities in mass loss rates, the choice of refrigerant can directly translate into immediate economic repercussions, owning to the decreased mass of marketable fruit for the storage facility.
However, to date, there has been a lack of comprehensive studies conducted on a commercial scale comparing the alternative refrigerants CO2 (R744) and propane (R290) regarding their suitability for apple fruit storage.
In this project, new refrigeration systems were installed in identical storage rooms with a capacity of 50 t, utilizing R290 (indirect evaporative cooling) and R744 (direct) as refrigerants.
In two experiment seasons, both storage rooms were filled over a 10-to-14-day period with homogeneous fruit material and cooled to 1°C. Subsequently, controlled atmosphere (CA) conditions were established (1.0 kPa O2,<0.7 kPa CO2 in 2023 and 1.2 kPa CO2 in 2024). For the assessment of each refrigeration system, the stability of climate control of each room during long-term storage (6 to 8 months) was evaluated and correlated with analyses of fruit quality, e.g., mass loss, softening rate, acid and peel yellowing, physiological disorders.
Furthermore, the metabolism activity of the fruit material in terms of CO2 production rate was monitored in-situ during storage.
Metabolic activity and associated quality‐parameter change rates were comparable between the two refrigeration systems.
Nevertheless, the room cooled with indirect R290 system exhibited significantly higher fruit mass loss than the R744 cooled room, most likely due to less stable temperature and relative humidity conditions.
Mass loss also varied markedly by bin position within the storage room and by apple cultivar.
Although these findings conflict with previous reports and require further validation, they highlight that economic evaluations of alternative refrigeration systems must consider not only capital and operating costs but also the impacts on the stored commodity.
Given the pronounced disparities in mass loss rates, the choice of refrigerant can directly translate into immediate economic repercussions, owning to the decreased mass of marketable fruit for the storage facility.
Authors
F. Büchele, T.G. Hoffmann, F.R. Thewes, P.V. Mahajan, D.A. Neuwald
Keywords
storage, propane (R290), CO2 (R744), alternative refrigerants, fruit quality
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