# _Forentation_
## 1 Introduction
This explains the high content of this acid (>10 g L\({}^{-1}\)) in the most cultivated varieties in Argentina's North Patagonia. From a sensory perspective, malic acid can be harsh at high concentrations. Microbiologically, it is unstable because lactic acid bacteria can metabolize it, leading to the formation of undesirable compounds. One common strategy in winemaking, and later explored in cider making, is to induce malolactic fermentation using selected lactic acid bacteria before bottling. Some studies have reported that malolactic fermentation, which often occurs spontaneously, not only reduces malic acid content but also produces volatile compounds that contribute significantly to the sensory attributes of certain ciders [27; 28; 29]. However, other studies report that malolactic fermentation can be a challenging process to control, potentially leading to a deterioration in the quality of the final product [30]. In this context, the use of starter cultures containing _P. kudriavzevii_ strains seems interesting. In a previous study, [PERSON] et al. [31] examined _P. kudriavzevii_ strains isolated from different substrates in the Patagonian region--wine, cider, and natural environments--and demonstrated that the cider strain _P. kudriavzevii_ NPCC1651 could degrade L(-)malic acid as its sole carbon source and consume malic acid present in acidic apple musts. This strain also stood out for its high fermentative capacity and fructose consumption. Additionally, the indigenous wine strain _S. cerevisiae_ NIF8 demonstrated some capacity to consume malic acid while also exhibiting a high fermentative ability. In this study, pure and mixed fermentations were carried out using the autochthonous strains _P. kudriavzevii_ NPCC1651 and _S. cerevisiae_ NIF8 to determine the optimal fermentation strategy for producing ciders with low acidity and distinct physicochemical and aromatic profiles--key attributes when selecting starter cultures for cider production from acidic apples. Additionally, reducing malic acid levels in ciders could lessen the need for added sugar during the final adjustment stage to balance the harshness of malic acid, resulting in a healthier beverage and providing cost savings. In all fermentation trials, both yeasts remained viable throughout the process and successfully completed fermentation, significantly influencing the chemical and sensory characteristics of the ciders. The simultaneous inoculation at a 1:1 ratio and the sequential fermentation initiated with _S. cerevisiae_ emerged as the most promising strategies, producing ciders with higher concentrations of lactic and succinic acids, isoamyl alcohol, 2-phenylethanol, isoamyl acetate, and 2-phenylethyl acetate while exhibiting lower levels of acetic acid and ethyl acetate. Among these, simultaneous inoculation is proposed for further pilot-scale testing in natural (non-sterile) musts due to the practicality of the strategy, aiming to achieve ciders with a distinctive sensory profile and to demonstrate the potential of this co-culture as an autochthonous starter for the production of high-quality ciders. Additionally, the interaction of the yeasts in the simultaneous inoculation strategy with the lactic acid bacteria present in the must and their effect on malolactic fermentation will also be evaluated.