Cryogenic Pre-treatment of Grape must before winemaking: Effect on must and wine physico-chemical and sensory profiles

Sauvignon blanc and Chenin blanc are key South African white wine cultivars whose varietal aroma profiles are strongly influenced by methoxypyrazines and volatile thiols. Efforts to enhance these compounds through viticultural and oenological interventions have produced inconsistent results, prompting interest in cryogenic pre-fermentative treatments as a potential strategy for improving aroma expression. This study examined the effects of cryogenic freezing (–20 °C and –4 °C) applied at four production stages—whole grapes (WG), macerated grapes (MG), turbid must (TM), and clear juice (CJ)—either immediately (T0) or after four months of storage (T4). A standard white winemaking protocol was followed, with untreated (unfrozen) wines serving as controls. Musts and wines were evaluated for physicochemical composition, volatile thiols, methoxypyrazines, and sensory attributes. Cryogenic treatments had minimal impact on must composition aside from increased pH and reduced total acidity. Vintage-related differences were evident in yeast assimilable nitrogen. In Sauvignon blanc, 3‑SHA exceeded its aroma threshold and typical concentration range, whereas 3‑SH and 4‑MSP remained within or below expected levels. Chenin blanc showed elevated 3‑SHA but generally lower 3‑SH. Most cryogenic treatments increased methoxypyrazine concentrations above perception thresholds in Sauvignon blanc. Aroma composition was strongly influenced by region and vintage, particularly in T4 Sauvignon blanc wines from WG and MG treated at –4 °C. Sensory evaluation showed that WG and MG treatments produced wines with enhanced tropical and thiol‑driven aromas, increased body, and higher overall quality. Overall, the production stage had the largest effect, while temperature and storage duration played smaller roles. Applying cryogenic treatments to WG or MG at –4 °C, particularly at T0, appears to be an energy-efficient, cost-effective approach for enhancing desirable aroma attributes.