The Ultraviolet radiation (UV-C) for the microbiological stabilization of red wine

Abstract

Abstract. The traditional procedure for the control of the microbiological stability of wine consists of the addition of sulfur dioxide (SO 2 ), which acts as an antimicrobial agent and also as an antioxidant. The search for alternative methods of microbiological control is important and necessary, since SO 2 is a potential allergen and consumers are increasingly looking for healthier and preservative free products. Ultraviolet radiation was tested as an innovative technology that can help reduce the amount of sulphur dioxide used in winemaking. The object of this study was to optimize the process conditions compared to the results obtained previously, and to evaluate the efficiency of microbiological stabilization and its influence on the physico-chemical characteristics, the phenolic composition and sensory profile. Thus, red wine with very low content of sulphur dioxide was subjected to UV-C radiation in two different doses 424J/l e 778J/l, and the preparation of a control wine was carried out to which 30 mg/l sulfur dioxide was added. The wines (control=UV0, UV1 and UV2) were analyzed over time (from 0 to 4 months). The results show that treatment with a lower dosage is effective in the microbiological control of the product. The wines subjected to treatment with UV-C showed an increase in intensity of colour, and the treatment does not affect the flavour and taste of the wine.Resumo: O procedimento tradicional de controlo da estabilidade microbiológica no vinho consiste na adição de dióxido de enxofre (SO 2 ), que atua como agente antimicrobiano e também antioxidante. A procura de métodos alternativos de controlo microbiológicoé importante e necessária, dado que o dióxido de enxofreé um potencial alérgeno e os consumidores procuram cada vez mais produtos saudáveis e livres de conservantes. A radiação ultravioleta tem sido estudada como uma tecnologia inovadora que pode auxiliar na redução do teor de dioxido de enxofre em enologia. O objectivo deste trabalho foi optimizar as condições do processo, face aos resultados já obtidos anteriormente, e avaliar a eficiência na estabilização microbiologica, e a sua influência nos parâmetros fisico-quimicos, na composição fenólica, e nas caracteristicas sensoriais. Assim, o vinho tinto com teor muito baixo em SO 2 foi submetido a radiação UV-C com duas doses diferentes, 424J/L e 778J/L, e procedeu-se aindaà preparação de um controlo, a que foi adicionado 30 mg/L de dióxido de enxofre. Os vinhos (UV0, UV1 e UV2) foram analisados ao longo do tempo (de 0 a 4 meses). Os resultados mostram que o tratamento com menor doseé eficaz no controlo microbiológico do produto. A análise sensorial mostrou que o tratamento com radiação UV-C não afectou o aroma e o sabor dos vinhos, inclusivamente estes vinhos foram mais pontuados no descritor intensidade da cor.

Preliminary study on the influence of UV-C irradiation on microorganism viability and polyphenol compounds content during winemaking of ‘Regent’ red grape cultivar

“…With an increase in exposure time, a decrease in total anthocyanins, and of each compound separately, was noted. A similar decrease in the total amount of anthocyanins after UV-C radiation was noted by Matias et al 20 . On the other hand, Pala and Toklucu 18 did not observe any signifi cant changes in monomeric anthocyanin content after UV-C treatment with the reactor type described above.…”

Suitability of ultraviolet‐C irradiation for white grape must

“…Part of the lamp remained external to the chamber for the continuous monitoring of UV-C dosage by the sensor connected to the data acquisition device. Since the UV-C energy used during treatment was known and the current intensity that penetrated through the section profile could be measured, it was possible to set the UV-C irradiation according to the volume of the medium, instead of by area, as previously reported by other authors (Fredericks et al 2011, Rizzotti et al 2015, Matias et al 2016).…”

“…Irradiation with UV-C has also been used during processing of coloured and turbid liquids, such as apple juice (Falguera et al 2011), grape must (Fredericks et al 2011, Falguera et al 2013) and wine (Matias et al 2016, Mijowska et al 2017. The impact of UV treatment, however, needs further investigation, especially the resistance of different microbial strains and the potential for activation of oxidative reactions.…”