Fruit-Based Fermented Beverages: Contamination Sources and Emerging Technologies Applied to Assure Their Safety

The food and beverage market has become broader due to globalization and consumer claims. Under the umbrella of consumer demands, legislation, nutritional status, and sustainability, the importance of food and beverage safety must be decisive. A significant sector of food production is related to ensuring fruit and vegetable conservation and utilization through fermentation. In this respect, in this review, we critically analyzed the scientific literature regarding the presence of chemical, microbiological and physical hazards in fruit-based fermented beverages. Furthermore, the potential formation of toxic compounds during processing is also discussed. In managing the risks, biological, physical, and chemical techniques can reduce or eliminate any contaminant from fruit-based fermented beverages. Some of these techniques belong to the technological flow of obtaining the beverages (i.e., mycotoxins bound by microorganisms used in fermentation) or are explicitly applied for a specific risk reduction (i.e., mycotoxin oxidation by ozone). Providing manufacturers with information on potential hazards that could jeopardize the safety of fermented fruit-based drinks and strategies to lower or eliminate these hazards is of paramount importance.

Ozone-Induced Biochemical and Molecular Changes in Vitis vinifera Leaves and Responses to Botrytis cinerea Infections

To investigate how plants cope with multi-stress conditions, we analyzed the biochemical and molecular changes of Vitis vinifera leaves subjected to single or sequential double stresses (infection by Botrytis cinerea (Bc) and ozone (O₃, 100 ppb for 3 h) treatment). In Bc⁺/O₃^- leaves, the hydrogen peroxide (H₂O₂) induction (observed at 12 and 24 h from the end of treatment (FET)) triggered a production of ethylene (Et; +35% compared with Bc^-/O₃^- leaves), which was preceded by an increase of salicylic acid (SA; +45%). This result confirms a crosstalk between SA- and Et-related signaling pathways in lesion spread. The ozone induced an early synthesis of Et followed by jasmonic acid (JA) and SA production (about 2-fold higher), where Et and SA signaling triggered reactive oxygen species production by establishing a feedback loop, and JA attenuated this cycle by reducing Et biosynthesis. In Bc⁺ + O₃⁺ leaves, Et peaked at 6 and 12 h FET, before SA confirmed a crosstalk between Et- and SA-related signaling pathways in lesion propagation. In O₃⁺ + Bc⁺ leaves, the H₂O₂ induction triggered an accumulation of JA and Et, demonstrating a synergistic action in the regulation of defence reactions. The divergence in these profiles suggests a rather complex network of events in the transcriptional regulation of genes involved in the systemic acquired resistance.

Preliminary Studies on Endotherapy Based Application of Ozonated Water to Bobal Grapevines: Effect on Wine Quality

The application of ozonated water in the vineyard is an increasingly popular tool for disease management, but the quality of grapes and resulting wines is likely to be affected. Endotherapy, or trunk injection, is a particularly useful method to apply phytosanitary products since many fungal pathogens colonize the grapevine woody tissues. Thus, the present study aimed to evaluate the effect on wine quality of the ozonated water applied to Bobal grapevines, one of the most cultivated red varieties in Spain, through endotherapy (E) or its combination with spraying (E + S). Endotherapy was carried out four times before harvest for both E and E + S treatments, and spraying was performed 2 days before and after each endotherapy application. Grapes were harvested, vinified, and the quality of the finished wines was evaluated through several enological parameters and the phenolic and volatile composition. Both treatments resulted in less alcoholic and more acidic wines. The E treatment, although it reduced the content of phenolic acids, stilbenes and flavanols, significantly increased anthocyanins, whereas E + S decreased the overall amount of phenolics, which had different implications for wine colour. In terms of aroma, both treatments, but E to a greater extent, reduced the content of glycosylated precursors and differentially affected free volatiles, both varietal and fermentative. Thus, the dose of ozonated water, frequency and/or method of application are determining factors in the effect of these treatments on wine quality and must be carefully considered by winegrowers to establish the optimum treatment conditions so as not to impair the quality of wines.

Ozone and Bioactive Compounds in Grapes and Wine

Ozone is widely used in the agri-food and food processing industries mainly as a sanitizing agent. However, it has recently become clear that ozone exposition leads to another important benefit: in living tissues, the induced-oxidative stress triggers the antioxidant response, and, therefore, it enhances the production of antioxidant and stress-related secondary metabolites. As such, ozone can be considered an abiotic elicitor. The goal of the present review was to critically summarize knowledge about the possibility of improving bioactive compounds and, consequently, the health-related properties of grapes and wine, by using ozone. The greatest interest has been given not only to the pre- and post-harvest treatment of table and wine grapes, but also to the explanation of the mechanisms involved in the ozone-related response and the main secondary metabolites biosynthetic pathways. From the literature available, it is clear that the effect of ozone treatment on health-related properties and secondary metabolites accumulation depends on many factors, such as the cultivar, but also the form (water or gaseous), doses, and application method of ozone. Most of the published papers report an increase in antioxidant compounds (e.g., polyphenols) and stress-related volatiles, confirming the hypothesis that ozone could be used to improve berry and wine compositional and sensory quality.

The application of ozonated water rearranges the Vitis vinifera L. leaf and berry transcriptomes eliciting defence and antioxidant responses

Ozonated water has become an innovative, environmentally friendly tool for controlling the development of fungal diseases in the vineyard or during grape postharvest conservation. However, little information is currently available on the effects of ozonated water sprayings on the grapevine physiology and metabolism. Using the microvine model, we studied the transcriptomic response of leaf and fruit organs to this treatment. The response to ozone was observed to be organ and developmental stage-dependent, with a decrease of the number of DEGs (differentially expressed genes) in the fruit from the onset of ripening to later stages. The most highly up-regulated gene families were heat-shock proteins and chaperones. Other up-regulated genes were involved in oxidative stress homeostasis such as those of the ascorbate-glutathione cycle and glutathione S-transferases. In contrast, genes related to cell wall development and secondary metabolites (carotenoids, terpenoids, phenylpropanoids / flavonoids) were generally down-regulated after ozone treatment, mainly in the early stage of fruit ripening. This down-regulation may indicate a possible carbon competition favouring the re-establishment and maintenance of the redox homeostasis rather than the synthesis of secondary metabolites at the beginning of ripening, the most ozone responsive developmental stage.