## 2 Cryogenic Technologies
Rapid freezing within a blast-freezez causes the formation of very small ice crystals, which causes less damage and preserves food at a higher quality [53]. Blast-freezing used as a pre-fermentative cryogenic treatment for wine grapes is conducted by blasting cold air with temperatures ranging between \(-10\)\({}^{\circ}\)C and \(-120\)\({}^{\circ}\)C directly onto whole grape bunches. This freezing method allows all individual berries to be frozen within 1-2 h [42; 51]. Cryogenic agents, i.e., carbon dioxide (CO\({}_{2}\)) and nitrogen (N\({}_{2}\)), are commonly added to whole grapes before crushing or during crushing in a solid state (dry ice or solid CO\({}_{2}\)) or using the direct injection of the cryogenic agent in liquid form [32]. The use of both these cryogens, solid CO\({}_{2}\) and liquid N\({}_{2}\), induces a thermal shock, leading to an increase in the degradation of the cell structure of grape berries [29; 32; 42]. This is advantageous as it prolongs the contact time between the grape pulp and must, thus protecting the grapes from oxidation [42]. If dry ice is used for the pre-fermentation skin contact, the cell walls are disrupted and \"disorganised\", which enables the extraction of compounds located within the grape skin [32]. The freezing process causes an increase in the intracellular liquids, therefore disrupting the membranes, allowing for the release of aromatic and phenolic compounds. Cryomaceration with cryogens was found to be the most effective \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Cryogenic** & **Temperature** & **Advantages** & **Disadvantages** & **Aroma Compounds** & **Resultant** & **References** \\
**Technology** & **t\({}^{\circ}\)C/Time** & & & Increased costs & & & \\  & & & & and energy & & & \\ Large capacity & \(-8\) to \(-20/9\) h to & & & groups/must/juice & consumptionSlower & & & \\ refrigerators & 4 months & 4 months & Conditions can be & rate of cooling & & & \\  & & & controlled & & & & \\  & & & & development & & & \\ \hline  & & & Wines produced from & & & & \\  & & & concentrated grape juice & & & & \\  & & & were superior in terms of & & & & \\  & & & chemical and & & & & \\  & & & sensory profiles & & consumption, & & \\ Freeze- & \(<\)0/10 min to 12 h & & Wines with & depending & & & \\ concentration & \(<\)0/10 min to 12 h & & fermentation tanks with & on the & & & \\  & & & cooling systems have the & & technology & & \\  & & & potential to perform & & applied & & \\  & & & freeze-concentration & & & & \\  & & & without purchasing & & & & \\  & & new equipment & & & & & \\ \hline Blast-freezing & \(-10\) to \(-120/<\)25 min & & Allows for quick freezing & High energy & & & \\  & & to 20 h & & of grape berries, \(<\)25 min & consumption & & & \\ \hline Cryogenic agents, & & & Creates an inert & & & & \\ i.e., carbon dioxide & & & atmosphere, protecting & & & \\ (CO\({}_{2}\)) and nitrogen (N\({}_{2}\)) & \(-20/8\) s to 24 h & & & from oxidation & Increased cost & & & \\  & & & Final wines were more & & & compounds, fatty & \\  & & & aromatic than & & acids, anthocyanins & & \\  & & & control wines & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of the cryogenic technologies used in winemaking and the effect on targeted aroma compounds. method because they are heavier than oxygen, they displace the air, and they create an inert atmosphere, protecting the grapes from oxidation [32; 42].