Pomegranate liquor preparation and analysis

The pomegranate (Punica granatum L.) liquor has been produced for several centuries in the south of Portugal, mainly in the mountain areas. The “Assaria” variety is the preferred cultivar due to its organoleptic properties and high arils to peel ratio. Wild pomegranates are also widely distributed but, despite the health benefits that have been associated to the fruits, they continue to be unappreciated for consumption. Liquor preparation is a very good alternative for wild pomegranate fruits. We prepared pomegranate liquors by following a maceration procedure using the arils or juice of Assaria and wild pomegranate fruits. Strawberry tree (Arbutus unedo L.) fruit spirits were used to prepare the liquors. At the end of the maceration time 5 day as minimum sugar syrup was added. The maturation period was three months or longer. The obtained liquors showed a very attractive pink colour. The colour and the total polyphenol, as well as the anthocyanin and ellagitannin profiles, were measured at the end of the maceration and maturation times. Wild pomegranates gave rise liquors with more intense pink colour and higher polyphenol contents than the prepared using Assaria fruits. The anthocyanin and ellagitannin profiles also indicated higher contents of polyphenols for liquors prepared using wild pomegranate fruits. When juice is used instead of complete arils during the maceration period punicalin is not present and the consequently total polyphenols is low. The main anthocyanins identified in the liquors were delphinidin-3,5-diglucoside, cyaniding-3,5-diglucoside, delphinidin–3-glucoside, cyaniding–3-glucoside, pelargonidin–3–glucoside; the main ellagitannins were punicalagin and punicalin.

Yeast diversity in the Mediterranean strawberry tree (Arbutus unedo L.) fruits' fermentations

In the Mediterranean region the fruits of the strawberry tree (Arbutus unedo L.) may be fermented and distilled to produce a traditional beverage very much appreciated in Southern Europe. The aim of the present work was to study the diversity of the yeast population and the killer activity of the isolates identified as Saccharomyces cerevisiae, obtained during solid state industrial fermentations of the arbutus berries. The identification of the isolates was performed by the 5.8S rRNA-ITS region restriction analysis and by sequencing the D1/D2 region of the large subunit of the rRNA gene. At the start of the fermentations, various non-Saccharomyces species were detected including Aureobasidium pullulans, Dothichiza pithyophila, Dioszegia zsoltii, Hanseniaspora uvarum and yeasts belonging to the genera Metschnikowia, Cryptococcus and Rhodotorula. However, as the biological processes progressed the number of different species decreased with S. cerevisiae and Pichia membranaefaciens becoming dominant at advanced stages of the must fermentation that is characterized by high concentrations of ethanol. Forty three isolates identified as S. cerevisiae were tested for killer activity against two sensitive reference strains and Zygosaccharomyces bailii. Their killer sensitivity in relation to five killer referenced toxins (K2, K5, K8, K9 and K10) was also studied. Out of the isolates analyzed, 95.3% were sensitive and 4.7% were tolerant against the killer toxins tested. Only three isolates revealed killer activity against one sensitive strain and two of them against the spoiler yeast Z. bailii. The microbiota obtained revealed an interesting potential to be used as starter cultures to overcome unpredictable uncontrolled fermentations of the arbutus fruits as well as in other applications of biotechnological interest. (C) 2012 Elsevier Ltd. All rights reserved.