Is there a systematic hidden 'hot spot' in refrigerated containers filled with fresh food in ventilated packaging?. (November 2022)

• Record Type: Journal Article
• Authors: Defraeye, Thijs; Lukasse, Leo; Shrivastava, Chandrima; Verreydt, Celine; Schemminger, Jörg; Cronjé, Paul; Berry, Tarl
• Is Part Of: Trends in food science & technology. Volume 129(2022)
• Page Start: 388
• Page End: 396
• Publication Date: 2022-11
• Subjects: Refrigeration -- Transportation -- Airflow -- Fruit -- Vegetables -- Computational fluid dynamics; Food industry and trade -- Periodicals; Food -- Biotechnology -- Periodicals; 664.005
• DOI: 10.1016/j.tifs.2022.09.005
• Languages: English
• ISSNs: 0924-2244

Abstract

Abstract: Background: Thousands of refrigerated containers transport fresh fruit and vegetables to feed the world yearly. These containers should preserve fresh-food quality as uniformly as possible throughout the cargo. Scope and approach: Several simulation studies have suggested the presence of a systematic hot spot in these containers near the supply-air inlet when warm cargo is cooled down in the container. Induced by airflow recirculation inside the ventilated packaging, the hot spot is located at the bottom of the pallets near the refrigeration unit. The fruit at the bottom of these pallets is well known to be exposed to cold air. However, the existence and impact of this apparent hot spot were not acknowledged explicitly. Interestingly, full-scale experiments and computational fluid dynamics (CFD) simulations contradict the existence of this recirculation-zone-induced hot spot. Key findings and conclusions: We analyzed the literature and the physical phenomena at play to identify if and why this recirculation-driven hot spot occurs. We found that the airflow recirculation can be partially hidden in full-scale experiments and that we are often not looking for it at that location. Physically, the presence of the recirculation zone is plausible. The CFD simulations that predict this zone include all relevant physical processes. However, we still need proof by detailed full-scale experiments to confirm its existence. It is likely that the recirculation only occurs in some ventilated shipments, but then we need to identify for which shipments this happens. If this recirculation zone is present in a ventilated cargo of perishables, we need to solve this problem urgently. We suggest a roadmap with steps to do so. Otherwise, we would be systematically losing food quality in many shipped containers. Besides slowing down fruit cooling, such a recirculation vortex can trap respiration heat, moisture, and metabolic gases. Mitigating this hot spot thus can considerably impact the quality of the fruit and vegetables shipped worldwide. Highlights: Simulations suggested a systematic hot spot in refrigerated containers. The hot spot is induced by airflow recirculation inside the ventilated packaging. The existence of this hot spot was not acknowledged explicitly. Full-scale experiments contradict CFD simulations. If this recirculation zone exists, we need to solve this problem urgently.