Energy and Quality Assessment in the Cooling of Crushed Bombino Nero Grapes with Indirect Heat Exchange System and Direct Heat Exchange System with CO2

A study was conducted in a winery in Puglia on the effect of cooling crushed and destemmed Bombino Nero grapes, comparing two different systems: (1) traditional indirect heat exchange using a water-cooled with a tube-in-tube heat exchanger and (2) a direct refrigeration system with a CO2 system. The must obtained from crushed grapes cooled with CO2, compared to that treated with an exchanger, has a lower ethanol content, greater presence of sugars and higher color and tone; these qualitative advantages are due to much faster cooling and deoxygenation, which slowed down the development of indigenous yeasts present on the surface of the grapes and allowed for greater extraction of the anthocyanin components in the must. These qualitative advantages give added value to the wine, justifying higher energy costs. In fact, the test results highlighted limitations associated with higher energy costs for the direct cooling system with CO2 compared to the traditional one with indirect heat exchange. Energy consumption in the winery is lower for the CO2 system, but energy and costs for capture, liquefaction and stockage must also be considered. However, from an energy and functional point of view, the potential advantages related to the clarification phase should not be neglected: it could be carried out at higher temperatures than those currently adopted for musts treated with CO2, limiting the amount of the required CO2 and consequently the total energy consumption for the whole process.