Characteristics of ice juices and ciders made by cryo-extraction with different cider apple varieties and yeast strains.

Two sets of nine ciders were made by cryo-extraction for two consecutive harvests combining three types of ice cider apple juices (mono-varietal, bi-varietal and multi-varietal) and three autochthonous Saccharomyces bayanus yeast strains. The type of juice significantly influenced the pH values and the contents of sorbitol and shikimic acid in the ice juices. The strains used as starters did develop the fermentation producing ciders with alcoholic degrees between 8.75 and 11.52 (% v/v) and volatile acidities lower than 0.55 g acetic acid/L. Regarding the ice ciders, the apple mixture significantly influenced the levels of methanol (higher in mono-varietal ciders), 2-phenylethanol, and some minor acetate esters (higher in the bi-varietal ciders). The last ciders were also more floral, buttery, acidic and bitter than those made from mono- and multi-varietal juices. In the first harvest, the ciders obtained from the bi-varietal apple mixture scored lower for overall sensory quality.

Influence of the method of obtaining freeze-enriched juices and year of harvest on the chemical and sensory characteristics of Asturian ice ciders.

Ice cider is a special product made from apple juices enriched by freezing. In this paper, the method of obtaining the ice juices (cryo-extraction and exhaustion) and the year of harvest have been evaluated. For this purpose, a controlled raw apple mixture and an autochthonous Saccharomyces bayanus strain were used throughout the study. Both the enrichment system and the year of harvest significantly influenced the levels of total phenols, sucrose, malic acid, ethyl acetate and 2-phenylethanol. The ciders made by cryo-extraction presented the higher sugar/acidity and sugar/polyphenol ratios. These ciders were more fruity, less astringent and scored better for quality than those obtained by exhaustion. Additionally, a preliminary assay of juice enrichment by cryo-concentration is described. The corresponding ciders presented higher methanol and lower 2-phenylethanol contents than those obtained by the cryo-extraction and exhaustion methods.

Genetic and phenotypic diversity of autochthonous cider yeasts in a cellar from Asturias.

This paper analyses yeast diversity and dynamics during the production of Asturian cider. Yeasts were isolated from apple juice and at different stages of fermentation in a cellar in Villaviciosa during two Asturian cider-apple harvests. The species identified by ITS-RFLP corresponded to Hanseniaspora valbyensis, Hanseniaspora uvarum, Metschnikowia pulcherrima, Pichia guilliermondii, Candida parapsilosis, Saccharomyces cerevisiae and Saccharomyces bayanus/Saccharomyces pastorianus/Saccharomyces kudriavzevii/Saccharomyces mikatae. The species C. parapsilosis is reported here for the first time in cider. The analysis of Saccharomyces mtDNA patterns showed great diversity, sequential substitution and the presence of a small number of yeast patterns (up to 8), present in both harvests. Killer (patterns nos. 22' and 47), sensitive (patterns nos. 12, 15, 33 and 61) and neutral phenotypes were found among the S. cerevisiae isolates. The detection of beta-glucosidase activity, with arbutin as the sole carbon source, allowed two S. cerevisiae strains (patterns nos. 3' and 19') to be differentiated by means of this enzymatic activity. Yeast strains producing the killer toxin or with beta-glucosidase activity are reported for the first time in autochthonous cider yeasts.

A molecular genetic study of natural strains of Saccharomyces isolated from Asturian cider fermentations.

AIMS: To analyse the genetic diversity and the dynamics of Saccharomyces strains in spontaneous fermentation in ciders. The effect of the cellar, harvest and cider-making technology were evaluated. METHODS AND RESULTS: The ecology of spontaneous cider fermentations in the same cellar (Asturias) was studied for two consecutive harvests (2000 and 2001) by using mtDNA restriction analysis. Our results showed that there was a succession of genetically different strains of Saccharomyces during cider production. In general, strains of Saccharomyces bayanus species predominated at the early fermentation steps (begining and/or tumultuous fermentations), while Saccharomyces cerevisiae yeasts were the most abundant at the end of the fermentation. Five S. bayanus strains (patterns III, VII, VIII, XV and XVII) were present at significant frequencies in all the experimental tanks during the two consecutive years. The results of the cluster analysis (unweighted pair group method using average linkage) showed higher similarities for the patterns III, XV, VII and VIII. Therefore, these strains should be considered associated with the microbiota of this cellar. CONCLUSIONS: A high polymorphism within populations of Saccharomyces was found throughout the different stages of Asturian production of cider. In all the cider fermentations, a variable number of S. bayanus and S. cerevisiae strains was always present. Our results indicate, over the period of time studied, the existence of the natural microbiota in the cellar. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has allowed us to gain a better understanding of the role of wild Saccharomyces yeast in Asturian cider fermentations.