Introduction

ASBC (The American Society of Brewing Chemists) and The American Society for Enology and Viticulture carried out a Joint Symposium on strains of yeast produced by Fermentis (the Beverage business section of the Lesaffre company) to analyze the impact on the flavor of fermented beverages.

Their methods of analysis are rigorous and follow the latest thinking in that they are organoleptic- or sensory-based. Firstly, there were 12 yeast strains analyzed sensorially and aromatically. Two strains have shown interesting sensory and aromatic profiles, and they were further tested under different conditions to determine the impact on ester production.

Ester production is important because esters are essential for the flavor and aroma of fermented products- they will taste and smell better.

Particular attention was paid to the impact of T, YAN, and Yeast Hulls addition on the overall results. To explain these terms, T is fermentation temperature, YAN is Yeast Assimilable Nitrogen and Yeast Hulls are the yeast cell walls.

The challenge was to increase ester production during white wine fermentation.
This was done by:

> Selecting the yeast strain
> Adjusting the fermentation conditions
> Selecting the appropriate nutrients to enhance the final wine

They can be tailored to each client and advice given to streamline the production line so that the wine profiles and volumes most suitable to their markets are adapted.

The result is quality, consistent product with the most pleasing bouquet.
The method of testing was based on the follow-up of the CO2 release and the reaching of the Smax. This is a very technical term which means the maximum velocity or the highest speed or rate of a reaction when a strain is introduced. They also worked out when the best moment was to introduce YAN to the mix to speed up fermentation.

SCALYA® fermentation management tool

scalya cuve-chardonnay-trials
title - zoom cuve

Cigar-shaped long stainless steel tanks were used for a better transfer of O2.

The CO2 sensors located at the top of the tanks allow to follow the production of this gas which represents the progress of the alcoholic fermentation.

All of the wines produced were analyzed chemically, analytically (for aroma) and sensorially by an internal and expert jury.

The fermentation recipe includes 4 temperature levels 16-14-16-18°C. 5mg/L of oxygen was added at the Smax.

To make sure that there wouldn’t be a nitrogen deficiency, YAN was added to the fermentable sugars to obtain a 1:1 ratio.

The same intake was kept for all strains and the addition was made in the form of DAP (Di ammonium Phosphate) at 35% of the fermentation process.

Testing 12 strains

title-testing-strains

> Flash pasteurized Chardonnay was
mixed in a large buffer tank. (10 hL)

> The turbidity (the cloudiness in
the liquid) was adjusted to 150 NTU
(Nephelometric Turbidity Unit)

> Assimilable nitrogen and residual
sugars were titrated (dissolved in
the liquid)

> Inertage and filling of the tanks
at 80L

> The turbidity was measured in
each tank for any readjustment

> Nitrogen was bubbled for the
deoxygenation and then inerting of
the top of the tank with CO2.

> The solutions were yeasted
at 20g/hL

> The nitrogen intake was at
35 % of the advancement rate

Strains 1, 5, and 6 were found to need the most time to ferment (437 hours) whereas Strain 3 ended its fermentation in 223 hours.

There were many differences in exactly the same fermentation conditions. Different strains required different things.
The basic criteria for sensorial analyses followed four main profiles.

The basic criteria for sensorial analyses followed four main profiles.

sensorial analysis - chardonnay-trials

Choice of strain 3 (SafŒno™ BC S103) and strain 10 (SafŒno™ HD S62)

The strains chosen after analysis of all 12 were Strain 3 BC S103 and Strain 10 HD S62

SafŒno™ BC S103
  • The fastest
  • The most robust
  • Low volatile acidity
  • Medium SO2 production
  • High 2-phenylethanol
  • Very high isoamyl acetate
  • Low ethyl esters
SafŒno™ HD S62
  • Medium fast
  • Robust
  • Medium volatile acidity
  • No SO2 production
  • Low 2-phenylethanol
  • Low isoamyl acetate
  • High ethyl esters

The two strains selected, the second step was to study the impact of 6 fermentation conditions on the kinetics (movement) and production of fermentation aromas. SafŒno™ BC S103 was shown to perform best.

Samples were taken every day and frozen before final analyses. It was found that SafŒno™ HD S62 fermented more quickly when the temperature was dropped and more nitrogen was added. The level of 2-phenylethanol increased.

SafŒno™ BC S103

BC S103 - analysis

With SafŒno™ BC S103, the determining factor was to boost the nitrogen but the temperature needed to be kept more constant.

Again with Profile 3 for SafŒno™ BC S103, isoamyl acetate production was boosted with an
increased lag phase, then a stationary phase but it declined after a temperature increase.

With the fourth profile analysis, boosting with oxygen or nitrogen assisted yeast
growth but increasing temperature caused a decrease.

Reduction of esters due to evaporation after yeast mortality in SafŒno™ BC S103 in Profile 5. In Profile 6, ethyl methylpropanoate production decreased at, or just after Smax.

The same profiles gave different results with SafŒno™ BC S103. The possible explanations for this point strongly to the influence of temperature and in the final analysis the optimum amount of YAN to be added is +135ppm for SafŒno™ BCS103.

The choice for extreme conditions

SafŒno™ HD S62

Conversely it is the addition of YEAST HULLS which make a difference for SafŒno™ HD S62 the difference could be due to the big impact of YAN on the precursor.

It seems that the hulls impact on improving fermentation conditions for SafŒno™ HD S62 is overtaking the other effects.

An internal panel evaluation by Vivelys found that Isomyl acetate was a good aromatic enhancer for SafŒno™ BC S103 it is a key flavor enhancer for SafŒno™ HD S62 also.

For deeply colored and structured reds

Conlclusion

During the trials, two strains demonstrated great performance:

SafŒno™ BC S103:

  • Strong performance noted, especially when Young Amino Nitrogen (YAN) is added.
  • Improved amylic profile observed when no yeast hulls are added and temperatures are kept low.

SafŒno™ HD S62:

  • Optimal performance achieved at low to medium temperatures.
  • No YAN addition is necessary, but adding yeast hulls contributes to a fruity profile.

The next stages involve the analysis of wines at different aging points: when they are young, at 8 months in the bottle, and at 12 months in the bottle. Stay tuned for the final results!