Abstract
The emerging trend towards the reduction of SO2 in winemaking has created a need to look for alternative methods to ensure the protection of wine against the growth of undesired species of microorganisms and to safely remove wine microorganisms. This study describes the possible application of silica nanospheres as a wine stabilisation agent, with Oenococcus oeni (DSM7008) as a model strain. The experiment was conducted firstly on model solutions of phosphate-buffered saline and 1% glucose. Their neutralising effect was tested under stirring with the addition of SiO2 (0.1, 0.25, and 0.5 mg/mL). Overall, the highest concentration of nanospheres under continuous stirring resulted in the greatest decrease in cell counts. Transmission electron microscope (TEM) and scanning electron microscopy (SEM) analyses showed extensive damage to the bacterial cells after stirring with silica nanomaterials. Then, the neutralising effect of 0.5 mg/mL SiO2 was tested in young red wine under stirring, where cell counts were reduced by over 50%. The obtained results suggest that silica nanospheres can serve as an alternative way to reduce or substitute the use of sulphur dioxide in the microbial stabilisation of wine. In addition, further aspects of following investigations should focus on the protection against enzymatic and chemical oxidation of wine.
Highlights
Winemaking, i.e., techniques of transforming grape must into wine, has to guarantee its stability in such a way that does not affect its organoleptic properties [1]
The Thermogravimetric analysis (TGA) of the silica nanospheres is presented in the Supplementary Information (Supplementary Materials, Figure S1)
The results indicated a decrease in the bacterial counts by 53% after just 60 min of incubation with continuous stirring, compared to the control
Summary
Winemaking (vinification), i.e., techniques of transforming grape must into wine, has to guarantee its stability in such a way that does not affect its organoleptic properties [1]. In the last two decades, more and more reports indicated that SO2 -derived compounds had caused many adverse clinical effects on human health. Research papers have indicated many varied methods, including the use of biological (e.g., microbial resources [10,11]) and physical methods (e.g., pulsed electric fields [12,13], high pressure [14,15,16], ultraviolet radiation (254 nm) [17,18]), electron beam irradiation [19], or additives to the musts or wines, such as dimethyl dicarbonate [20,21], bacteriocins [22], chitosan [23], chitooligosaccharide [24], lysozyme [25,26,27], phenolic compounds [27,28] or α-pinene terpene [29]
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