Abstract
The aim of this study was to determine the effect of two yeast strains (Saccharomyces cerevisiae and S. bayanus) on the fermentation with or without additional pectinase. The organic acids products (tartaric, malic, and succinic acid), carbohydrates (glucose, fructose, and sucrose) utilized, and ethanol produced were examined by HPLC. The efficiency of fermentation was affected by several parameters such as the preparation procedure of the fruits, like temperature (18�C), yeast strain applied, pH adjustment (3.2), the dosage of yeast nutrient and application of pectinase. We have found that pectinase pre-treatment and S. cerevisiae could significantly alter the amount of the examined components, which changed the quality of the end product. We have also experienced significant (p≤0.05) differences in the sugar utilisation of yeast strains as well as organic acid contents in the different stages of fermentation, where the samples fermented with spontaneous and identified yeast strains.
Highlights
It is well known that the fermentation process of fruits is basically determined by their compositional parameters, the proportion of their nutritional components and health condition of fruits, including their microbiological appropriateness
Beside specific yeast strains used in fermentation non-Saccharomyces strains have gained an ever-increasing role, since they are capable to imitate the processes of spontaneous fermentation, and they increase the aromatic complexity of the product, as well [3]
If we look at the results for different preparation methods - disregarding the starter culture - we can find an unambiguous difference between samples treated with pectinases and the non-treated ones
Summary
It is well known that the fermentation process of fruits is basically determined by their compositional parameters (sugar content), the proportion of their nutritional components and health condition of fruits, including their microbiological appropriateness. Cells function in a remarkably complex environment during the fermentation process, and they can adapt to these environmental factors, in addition to changing environmental parameters. This ability is an essential requirement against yeast strains developed for alcoholic fermentation [2]. Kloeckera apiculata (the anamorph of Hanseniaspora uvarum) yeasts composing more than 80% of the microflora [4] These microorganisms get into the mash during fruit processing, and they carry out spontaneous fermentation. With the progress of fermentation, non-Saccharomyces species disappear one by one; Saccharomyces cerevisiae is responsible the main and final stage of fermentation The population of this species is quite different concerning its oenological and other characteristics, e.g., its vulnerability against lethal toxins or its ability to produce them [5]. The alcohol production capacity of S. cerevisiae strains was examined and proven in several studies in alcoholic fermentation but in the field of bioethanol production from sewage-slum as well [6]
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