| Resumo : |
This study presents an exergy analysis of the beef freeze-drying process, aiming to determine key performance parameters per kilogram of dehydrated product by evaluating the cooking, freezing, dehydration, and condensation stages. Exergy destruction, exergoeco-enomic costs, and environmental impacts were quantified considering beef and electricity as the main inputs. Results indicate that cooking is responsible for 96.25% of the total exergy destruction due to the large amount of thermal energy supplied, which is not fully converted into useful work, causing significant losses; however, cooking is not a mandatory stage, as many products are freeze-dried raw and prepared at consumption owing to their high rehydration capacity. From the perspective of specific irreversibilities, dehydration-including drying and condensation-shows the highest proportional exergetic penalty, accounting for 3.67% of total exergy destruction, mainly due to the high energy consumption of the vacuum pump that maintains the sublimation pressure in the drying chamber; freezing contributed only 0.08% of the exergy destruction. Considering only the mandatory stages-freezing and drying at low pressure and temperature-dehydration represents more than 97% of exergy destruction in this subset, reinforcing its importance for energy optimization. The exergoeconomic analysis showed that the market price of freeze-dried beef is 42.58 times higher than raw beef, while the specific exergy cost of cooked and freeze-dried beef is 2.74 times greater than raw beef and 2.06 times greater than cooked beef, reflecting the thermodynamic complexity and high energy demand, especially in drying. Environmentally, there was a proportional increase in specific CO2 emissions per kilogram processed, but more than 85% of exergoeconomic costs and emissions are linked to raw beef production, highlighting the role of agricultural practices such as enteric fermentation and manure management in the environmental footprint. The separate stage analyses allowed identification of the largest irreversibilities and exergetic losses, as well as economic and environmental impacts, guiding effective strategies for improving energy efficiency and reducing environmental impact, which are essential for more sustainable processes in the food industry. |