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Autochthonous yeasts associated with mature pineapple fruits, freshly crushed juice and their ferments; and the chemical changes during natural fermentation
On-ong Chanprasartsuk a, Cheunjit Prakitchaiwattana a,*, RomaneeSanguandeekul a, Graham H. Fleet b
Department of Food Technology, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330, Thailand Food Science, School of Chemical Sciences and Engineering, The University of New South Wales, Sydney, NSW 2052, Australia
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This study investigated autochthonous yeasts and their functions in thespontaneous fermentation of freshly crushed pineapple juice samples collected from two different areas of both Thailand and Australia. Hanseniaspora uvarum and Pichia guilliermondii were the main yeast species observed on the fruit skins of Thai samples, and also in the fresh juice and ferments of all samples from both countries. P. guilliermondii was consistently present as the dominant species during theearly stage of the fermentation, whereas H. uvarum became more prevalent towards the end of the six-day fermentation period, with populations increasing from an initial level of $5 log CFU/mL to $8 log CFU/mL at the end of fermentation. The ethanol levels in samples from both regions of Thailand were maximal at 2 days of fermentation, reaching $1 to 2% (v/v) but then declined thereafter. Incontrast, in the Australian samples ethanol levels continued to increase over the entire six-day fermentation period and reached $3 to 4% (v/v). A signiﬁcant decrease in citric acid and increase in lactic acid levels were observed throughout the fermentation period in the samples from Thailand, but not in those from Australia where the different acid contents (and pH) were relatively stable. The otherwine yeasts and, in particular, Saccharomyces yeasts, were not found in any of sampled fermentation systems that is apparently different from the other fruit juices. These ﬁndings suggested that the freshly crushed pineapple juice may possibly have some effects on the other autochthonous yeasts having important role in alcoholic fermentation. Ó 2010 Elsevier Ltd. All rights reserved.
Articlehistory: Received 9 November 2009 Received in revised form 1 April 2010 Accepted 15 April 2010 Available online 11 May 2010 Keywords: Autochthonous yeasts Denaturing gradient gel electrophoresis Fermentation Pineapple
1. Introduction The pineapple variety ‘‘Smooth cayanne” (Ananas comosus (L.) Merr.) is a signiﬁcant economic farm-plant that is widely grown in every part of Thailand, one of thelargest exporters of pineapple fruits, and some pineapple products, in the world. Recently, interest in developing pineapple wine, one of the new pineapple products, has increased as a potential product for exportation. Pineapple can be used to produce fruit wine (also known as country wines) since it contains a unique fruity ﬂavour and has sufﬁcient nutrients (including nitrogen) for yeast growthand fermentation, giving acceptable wine characters to the resultant (typically dry) white wine (Callens and De Smet, 1991; Ruengrongpanya, 1996; Ayogu, 1999). Moreover, its juice can be easily extracted, yielding up to 55% juice by weight, and so giving a good and easily obtained yield (Salvi and Rajput, 1995). Finally, the extracted juice is easy to ﬁlter and decontaminate, somewhat similar to thenature of grape juice, and thus is amenable to large scale commercial production. Therefore, pineapple has a high
* Corresponding author. Tel.: +66 2218 5515 6; fax: +66 2254 4314. E-mail address: cheunjit.P@chula.ac.th (C. Prakitchaiwattana). 0960-8524/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2010.04.047
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