# Towards Sulphite-Free Winemaking: A New Horizon of Vinification and Maturation
## 1 Introduction  
The winemaking process, spanning from grape harvesting to the culminations of the fermentation and maturation phases, exposes wine to oxygen at various stages [1], which, although plays a key role in facilitating microbial development and polymerization of phenolic components, may have both positive and negative effects [2; 3; 4]. Limited and controlled amounts of oxygen introduced through micro-oxygenation may enhance aromas and reduce green and vegetal notes in wines [4; 5; 6]. Conversely, excessive exposure to oxygen may lead to an undesirable loss of colour and aroma [2; 7]. To counteract these negative effects, the use of sulphur dioxide (SO\({}_{2}\)) during wine production has became crucial to mitigate undesirable outcomes [8; 9; 10]. The use of SO\({}_{2}\) as a food preservative is regulated by the European authority. Regarding wine, Council regulation (EC) N\({}^{\circ}\) 1493/1999 of 17 May 1999 and Commission Regulation (EC) No 1622/2000 of 24 July 2000 have established a limited total concentration of SO\({}_{2}\) up to 160 mg/L in red wines, and 210 mg/L in white and rose wines [11]. Sulphur dioxide is a longstanding additive in winemaking thanks to its antiseptic, antioxidant, and antimicrobial properties [12; 13]. Indeed, microbiologically, SO\({}_{2}\) exerts an important antiseptic function that has proven to be specifically selective towardsboth acetic and lactic acid bacteria, and it also helps to determine the yeast population present [14], holding significance for both producers and consumers [10]. An excessive consumption of sulphites, however, can elicit symptoms such as headaches, nausea, stomach irritation, and respiratory distress, especially in asthmatic subjects [11; 15; 16]. Moreover, an overabundance of SO\({}_{2}\) during the winemaking process can induce changes in the sensory characteristics of the final product [10; 17]. To address these concerns, permissible concentrations of this additive in wines have been progressively reduced. The wine industry is increasingly compelled to minimize or eliminate SO\({}_{2}\), particularly in the production of organic wines. This aspect highlights the need for novel and healthier strategies, prioritizing both the consumer well-being and the quality of the final wine product [10; 18]. Several techniques have been employed to regulate the use of SO\({}_{2}\) in the winemaking process, such as the application of high-pressure pulses [19], ultraviolet irradiation [20], and electric fields [21], or the development of alternative additives like lysozyme [22], ascorbic acid [23], glutathione [24], and plant extracts [25], or colloidal silver nanoparticles [26]. Nowadays, there is a growing consumer demand for foods with natural preservatives, inspiring interest in alternatives to chemical additives [27; 28]. In the field of wine production, natural plant extracts have emerged as a promising alternative to sulphides. These extracts, rich in phenolic compounds recognized for their antioxidant and antimicrobial properties [29], are being explored as potential substitutes for sulphides in wine production. Indeed, polyphenols, acting as scavengers of free radicals and natural metal chelators, are widely employed in the food industry to preserve oxidative stability and extend products' shelf life [30]. The demonstrated effectiveness of phenolic compounds and their derivatives in preventing autoxidation adds appeal to these natural preservatives [31; 32; 33; 34]. In this context, some authors have successfully produced wines with a sensory profile similar to those produced with SO\({}_{2}\) by substituting this preservative with extracts derived from winery by-products, such as grape seeds and stems rich in antioxidant compounds [35]. Wines produced with natural preservatives are seen as more competitive on the global market, mainly thanks to their numerous positive aspects, such as the prevention of degenerative diseases and their antimicrobial activity [36].