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Microbial ecology of sour rotten grapes and their influence on chemical and sensorial wine quality
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Orientador(es)
Resumo(s)
The grape berry microbiota is deeply influenced by the sanitary status of grapes. In sound grapes the most frequent yeast species were basidiomycetes, Aureobasidium pullulans, Candida zemplinina and Hanseniaspora uvarum. Sour rotten grapes were mostly colonised by C. zemplinina, H. uvarum, Issatchenkia spp. and Zygoascus hellenicus. The presence of minoritary populations of Zygosaccharomyces bailii was only found in damaged grapes. The acetic acid bacteria Gluconobacter spp. and Gluconoacetobacter spp. were isolated from healthy and injured grapes, while Acetobacter spp. was only associated with sour rot.
Sour rot induced an increase of the sugar content, volatile acidity, colour and total phenols of grape juices. Wines with sour rot up to 30% showed equal overall quality after one year of bottle storage. However, wines made with sour rotten grapes showed a distinctive chemical and honey-like aroma. Phenylacetic acid and ethyl phenylacetate, both exhibiting honey-sweet like aromas, emerged as key-aroma compounds of sour rotten wines.
The causal agents of sour rot were acetic acid bacteria disseminated by the insect Drosophila spp.. In the absence of these flies, putative plant defense mechanisms, probably mediated by the accumulation of phenylacetic acid, led to skin healing, preventing sour rot spreading
Descrição
Doutoramento em Engenharia Alimentar - Instituto Superior de Agronomia
Palavras-chave
sour rot damaged grapes grape ecology spoilage yeasts acetic acid bacteria wine aroma
Contexto Educativo
Citação
Barata, André Bernardo Antunes dos Santos Neves - Microbial ecology of sour rotten grapes and their influence on chemical and sensorial wine quality