CZ307083B6 - Yeast strain of Saccharomyces cerevisiae CCM 8714 and its use in beer production - Google Patents

Abstract

Yeast strain Saccharomyces cerevisiae CCM 8714 and its use in beer production

Description

Technical field

The invention also relates to a novel yeast strain Saccharomyces cerevisiae CCM 8714. The invention further relates to the use of this yeast strain in beer production.

BACKGROUND OF THE INVENTION

Beer production consists of controlled fermentation of sugars contained in wort by brewer's yeast. Brewer's yeasts are cultural yeasts of several species and genera: Saccharomyces pastorianus is used to produce bottom-fermented beers, Saccharomyces cerevisiae is used to produce top-fermented beers, and specialty beers such as Brettanomyces or Torulaspora are produced (see for example T. Kochláňová et al .: "Yeast nonSaccharomyces and their importance in the brewing industry I. Part - Brettanomyces (Dekkera)" and "Yeast non-Saccharomyces and their importance in the brewing industry Part II", both Kvasný Průmysl 62/2016 (7 -8)). In doing so, brewer's yeast converts carbohydrates into ethanol, carbon dioxide and the energy required for yeast propagation, as well as about two thousand other substances, especially higher alcohols, esters, aldehydes, etc., which affect the resulting sensory properties of the finished beer. The overall ratio of these higher alcohols and esters is then very important for the overall sensory impression, since the individual compounds themselves are very often below the threshold concentration of sensory perception. For example, it is generally known that Saccharomyces cerevisiae strains produce a greater amount and a wider spectrum of sensory active substances than Saccharomyces pastorianus strains (see, eg, Lodolo et al., "The yeast Saccharomyces cerevisiae - the main character in beer brewing." FEMS Yeast Res 8 (7): 1018-36, 2008) and that the "lighter" taste of bottom-fermented beers causes, in addition to the lower main fermentation temperature, an altered expression of the genes responsible for ester production in Saccharomyces pastorianus (see e.g. Procopio et al .: "Function and regulation of yeast genes involved in higher alcohol and ester metabolism during beverage fermentation", European Food Research and Technology 233 (5): 721-729, November 2011).

Wine production then consists in fermentation of carbohydrates present in grape must with wine yeast. This fermentation results in the conversion of carbohydrates to ethanol and carbon dioxide, and the energy needed to propagate the yeast. Wine yeast is more resistant to alcohol than brewing yeast. They enter the must either from the surface of the berries (spontaneous fermentation) or by adding a pure culture of noble yeast (pure fermentation). Cultural wine yeasts belong to the species Saccharomyces cerevisiae and Saccharomyces bayanus.

SUMMARY OF THE INVENTION

The present invention provides a novel yeast strain of Saccharomyces cerevisiae CCM 8714 which has been isolated from spontaneous fermentation of grape must. It was prepared for further use by selection and re-boiling on wort agar with tetracycline. Cultivation was then performed aerobically in a microbiological incubator at 26 ° C for 3-5 days. After the growth of the yeast culture on the agar surface, this culture was transferred with a sterilized inoculating loop to a new Petri agar dish and seeded with a so-called cross smear diluting the yeast concentration on the agar. This procedure was repeated until the yeast culture had grown to form visibly separated colonies. Subsequent isolation of the yeast strain Saccharomyces cerevisiae CCM 8714 was then performed by inoculating the selected colony onto a petri dish containing wort agar.

The strain thus isolated was then characterized by biochemical assays and polymerase chain reaction (PCR).

The yeast strain Saccharomyces cerevisiae CCM 8714 produces ellipsoid to spherical cells having dimensions of 6-8 µm x 4-6 µm that do not form mycelium and rarely form pseudomycelium.

Appearance and consistency of colonies - the coating is pasty, creamy, light brown, smooth, glossy. Character of growth in liquid medium - it forms sediment in liquids, wastes never form.

Saccharomyces cerevisiae strain CCM 8714 utilizes both aerobic (oxidized) and anaerobic (fermented) galactose, sucrose, raffinose, maltose, and glucose. Aerobically uses (oxidizes) lactate.

The yeast strain Saccharomyces cerevisiae CCM 8714 has some advantageous properties for use in beer brewing compared to brewing yeast Saccharomyces cerevisiae and Saccharomyces pastorianus. In particular, it involves the production of only a minimal amount of diacetyl which gives the finished beer a taste for butter and is considered undesirable at higher concentrations. The optimum temperature for beer production using this strain is in the range of 18-22 ° C, where the yeast produces the optimal amount of sensory active substances; however, this strain can also be used for fermentation at temperatures of 12 to 16 ° C, and even at these temperatures it is characterized by a high fermentation rate.

The yeast strain Saccharomyces cerevisiae CCM 8714 according to the invention is deposited in the collection of microorganisms of the Research Institute of Brewing and Malting, as, referred to as RIBM code RIBM 191 and in the Czech Collection of Microorganisms in Brno under CCM 8714.

DETAILED DESCRIPTION OF THE INVENTION

Example 1: Preparation of the yeast strain Saccharomyces cerevisiae CCM 8714 for laboratory fermentation tests

In the preparation of the yeast strain Saccharomyces cerevisiae CCM 8714 for practical use - e.g. for further testing or for the production of beer, a pure culture of this kennel, obtained by isolation from spontaneous grape must fermentation (see above), was used up to of the preparation was stored in a refrigerator at 2 ± 1 ° C.

The culture of the yeast strain Saccharomyces cerevisiae CCM 8714 was seeded on sloping wort agar in cotton-stoppered tubes. From the formed yeast growth, a portion of the biomass was then transferred through a sterile seed loop into 10 ml of 10% sterile wort, followed by cultivation at 25 ° C for 2 days. The top fermentation layer was then discarded and the yeast sediment was transferred to 50 ml of 10% sterile wort and cultivated at 20 ° C for 2 days. Subsequently, this strain was multiplied by converting it into an ever larger volume in a ratio of approximately 1: 4. Thus, the yeast sediment was first transferred to 250 ml of 10% sterile wort where propagation was carried out at 17 ± 1 ° C for 5 days, after which the formed yeast sediment was transferred to 1000 ml of 10% wort where cultivation was carried out at 17 ± 1 for 3 days. Deň: 32 ° C.

The yeast strain Saccharomyces cerevisiae CCM 8714 prepared in this way can be used directly for laboratory fermentation tests or for beer production. If necessary, it is washed again with water (repeated sedimentation and washing) to remove the culture medium.

Example 2: Preparation of beer using the yeast strain Saccharomyces cerevisiae CCM 8714

To the wort with the original extract of about 12% (but the same procedure can be used to prepare beer from the wort with another extract), a concentrated yeast concentrate of yeast Saccharo-2CZ 307083 B6 myces cerevisiae CCM 8714 prepared according to the procedure described in Example 1 was added. million cells / ml wort. Subsequent fermentation was carried out in a sterilized plastic vessel at 21 ± 1 ° C for 5 days.

During fermentation, the course of cell proliferation and sedimentation was monitored by counting the cells by microscopic technique using a Burker chamber. In addition, extract loss, fermentation, alcohol concentration and pH change were further measured. The measured values are given in Table 1.

Table 1

Measured parameter Oh 24 h 48 h 72 h 96 h 120 h Alcohol (% vol) 0 2.54 3.79 3.91 3.99 4.04 Apparent fermentation (%) 0 41.67 62.49 65.8 66.2 67.29 Extract apparent (% wt) 11.87 6.61 4.27 3.96 3.75 3.69 pH 5.74 4.49 4.40 4.35 4.30 4.22 Number of cells (mil / ml) 31 69.6 76.05 54.95 30.6 30.4

After fermentation, the beer thus prepared was transferred to lager vessels and stored at 2 ± 1 ° C in a lager cellar. After 6 weeks of lying, it was measured for pH, fermentation, extract, alcohol content, diacetyl, pentanedione, acetaldehyde, and dimethylsulfide (DMS) concentrations, the measured values are shown in Table 2.

As is evident, the strain of Saccharomyces cerevisiae CCM 8714 produces only low concentrations of diacetyl compared to conventional brewer's yeast, which is responsible for the undesirable buttery flavor of beer.

Table 2

Measured parameter Value Apparent extract (% by weight) 3.66 Actual extract (% by weight) 5.15 Alcohol (% vol) 4.09 Apparent fermentation (%) 67.7 Diacetyl (mg / l) 0.014 Pentandione (mg / l) <0.005 Acetaldehyde (mg / l) 56.07 DMS (pg / l) 29

In addition, the content of higher alcohols and esters, which significantly contribute to the sensory profile of the finished beverage, was also measured with this beer. Table 3 lists selected higher alcohols and esters and the ratio of total higher alcohols to esters (A / E ratio). The value of this ratio suggests that yeast Saccharomyces cerevisiae CCM 8714 behaves similarly to upper brewer's yeast, but produces higher amounts of betafenyl alcohol than most of their strains (typically up to 4) and very low amounts of diacetyl and pentanedione. This is very advantageous from the point of view of beer production technology, since it is not necessary to include a long delay in the production process for the degradation of diacetyl.

-3 CZ 307083 B6

Table 3

Monitored substance Content ethyl formate (mg / 1) 0.05 ethyl acetate (mg / l) 9.29 propyl acetate (mg / l) 0.08 isobutyl acetate (mg / l) 0.251 ethylbutyrate (mg / l) 0.169 Propanol (mg / l) 27.43 isobutanol (mg / l) 16.97 isoamyl acetate (mg / l) 1.31 2 and 3-methyl-butanol (mg / l) 59.44 ethyl caproate (mg / 1) 0.246 ethylcaprylate (mg / 1) 0.163 ethyl hexanol (mg / l) 0,034 furfuryl alcohol (mg / l) 0,068 Phenylethyl acetate (mg / 1) 0.352 β-phenyl alcohol (mg / l) 8.73 sum of alcohols (mg / 1) 112.67 sum of esters (mg / 1) 11.94 A / E ratio 9.43

In addition, the production of phenolic substances responsible for the medicinal or clove aromas of beer was also analyzed. The values obtained are shown in Table 4, and are obvious to be similar to those of brewer's yeast strains used in the production of wheat beers.

Table 4

Monitored substance Content 2-Phenylethanol (mg / l) 23.05 4-vinylguaiacol (mg / l) 5.92 Tyrosol (mg / l) 4.51

A sensory evaluation of beer was also carried out by the tasting committee. The beverage prepared using the yeast Saccharomyces cerevisiae CCM 8714 showed no sensory defects, was pleasantly saturated, with an intense aroma of coriander and clove and tasted like top-fermented beer. Bitterness was evaluated as slightly adhering. The overall subjective impression was assessed as above-average 15 prices.

Claims (2)

PATENT CLAIMS 1. The yeast strain Saccharomyces cerevisiae deposited with the Czech Collection of Microorganisms under number 8714 isolated from spontaneous fermentation of grape must, which aerobically and anaerobically processes galactose, sucrose, raffinose and maltose and aerobically processes lactate, and which forms 20 ellipsoid to spherical cells with dimensions 6 to 8 µm x 4 to 6 µm that do not form mycelium. Method for producing beer, characterized in that the main wort fermentation is carried out by the yeast strain Saccharomyces cerevisiae CCM 8714 according to claim 1.