Biological
science / 6. Microbiology
Gorshunov Yu.V.
Ukrainian
Research Institute of Alcohol and Food Biotechnology, Ukraine; National
Technical University of Ukraine “Kyiv Polytechnical Institute”, Ukraine
BY-PRODUCTS OF GLUCOSE-FRUCTOSE SYRUP FERMENTATION WITH
DISTILLERY YEAST
Glucose-fructose
syrup (GFS) is a most promising sugar substitute product among a plurality of
other substitutes [1]. GFS is broadly used worldwide accounting for that it may
compete with cane and beet sugar with its processing and organoleptic
characteristics; therefore it is in substantial demand in many food industries.
GFS production has an advantage of its superior efficiency as compared with
sugar beet production owing to a possibility to organise a whole-year
production and to obtain useful by-products (oil and fodder products). GFS is
obtained from starch molasses via a transformation of some glucose into
fructose. In such case, a prepared syrup contains 71 % of dry solids: of them,
52 % - glucose, 42 % - fructose and about 6 % - oligosaccharides. Such
characteristics as viscosity rate, relative sweetness and osmotic pressure of
GFS are similar to those of invert sugar, and GFS is actually free of sugar
decomposition products. GFS is in stable and consistently growing demand and is
broadly used in the manufacture of alcohol-free beverages, fruit drinks,
syrups, baby food, preserves, confectionery and diary products, and in brewage.
GFS-42
has the following characteristics: dry solids weight ratio (DS) – not less than
68.6 %, and weight fraction of fructose – not less than 41 %. Previous studies
have confirmed the suitability of GFS-42 for alcohol fermentation. It has been
also found that most efficient yeast species for the purposes of GFS-42
fermentation include Saccharomyces cerevisiaå U-563 requiring growth promoting substances in a form of corn
extract (1 % of the overall volume of the medium) for the maximum yield of
ethanol in a course of its biosynthesis in a fermented wort.
It is generally accepted [2]
that in a course of alcohol fermentation, sugar from sugar-containing feedstock
is used for the formation of the following substances: ethanol, carbon dioxide,
yeast biomass, glycerol, higher alcohols, aldehydes, organic acids and esters.
Loss of unfermented sugar in a fermented wort may be 2.1 – 2.8 % of the input
sugar.
This
work is aimed at a determination and comparison of the quantities of
accumulated by-products of alcohol fermentation of wort prepared on the basis
of GFS-42 and molasses wort (MW).
Results
of fermentation of the wort prepared on the basis of GFS-42 and molasses wort
are summarised in Table 1. Characteristics of fermented worts obtained in a
course of fermentation of the wort prepared on the basis of GFS-42 and MW,
including etanol concentration, content of unfermented sugar, quantity of
accumulated biomass, content of glycerol, are actually similar for all
mentioned worts. The quantity of carbon dioxide formed in a course of
fermentation of GFS-42 wort correlates with the quantity of carbon dioxide
formed in a course of fermentation of molasses wort. Significance differences
may be observed only in the characteristics of apparent density and true dry
substances (molasses contains more impurities than GFS-42).
Table 1 – Alcohol fermentation of GFS-42
wort and molasses wort
|
Characteristics of fermented wort |
Molasses wort |
GFS-42 wort |
|
ÑÎ2, (g/100
ñm3), released during 96 h |
9.9 |
9.9 |
|
Apparent
density, % DS |
-8.5 |
-1.6 |
|
True DS, % |
10.3 |
1.8 |
|
Medium ðÍ, units |
4.84 |
4. 52 |
|
Acidity, degree |
0.56 |
0.58 |
|
Ethanol
percentage, % v/v. |
12.0 |
12.0 |
|
Content of
unfermented sugar, % |
0.29 |
0.32 |
|
Yeast biomass, g/dm3 |
26.5 |
23.3 |
|
Glycerol content, % |
0.678 |
0.680 |
Upon fermentation,
chromatograms of wash distillates were obtained to determine the composition
and quantity of fermentation by-products (Table 2).
Table 2 – Results of chromatographic
analysis
|
Ingredients |
Units |
Molasses wort |
GFS-42 wort |
|
Alcohol concentration |
% v/v |
12.0 |
12.0 |
|
Acetaldehyde |
mg/dm3 |
246.5 |
245.9 |
|
Methyl acetate |
mg/dm3 |
13.8 |
14.0 |
|
Ethyl acetate |
mg/dm3 |
206.8 |
207.5 |
|
Isoamyl acetate |
mg/dm3 |
21.1 |
20.8 |
|
Total esters |
mg/dm3 |
241.7 |
242.3 |
|
n-Propanol |
mg/dm3 |
198.2 |
193.1 |
|
Isopropanol |
mg/dm3 |
2.9 |
2.8 |
|
n-Butanol |
mg/dm3 |
10.8 |
9.4 |
|
Isobutanol |
mg/dm3 |
695.4 |
681.8 |
|
n-Amyl
alcohol |
mg/dm3 |
3.7 |
3.5 |
|
Isoamyl alcohol |
mg/dm3 |
3836.5 |
3608.5 |
|
Fusel alcohols, total |
mg/dm3 |
4747.5 |
4499.1 |
By-products
accumulated in a course of alcohol fermentation of GFS-42 wort are almost the
same as by-products accumulated in a course of alcohol fermentation of molasses
wort. Meanwhile, the content of all identified fusel alcohols in the alcohol
distillate obtained upon GFS-42 wort fermentation is somewhat lower than in the
distillates obtained upon molasses wort fermentation. The overall reduction in
the accumulation of fusel alcohols in a course of GFS-42 wort fermentation as
compared with molasses wort fermentation amounts to 5.2 %.
It
has been proven that in a course of GFS-42 wort fermentation, the composition
of accumulated by-products is identical to the composition of by-products of
molasses wort fermentation. The overall reduction in the accumulation of fusel
alcohols in a course of GFS-42 wort fermentation as compared with molasses wort
fermentation is 5.2 %.
Literature
1. Yu. Bondarenko. Influence of
glucose-fructose syrup on the consumer properties of sugar articles [Text] / Yu. Bondarenko, V. Drobot // Baking
and Confectionery Industries in Ukraine (Ukr.). - 2009. - No. 6. - P. 8-10.
2. Guidelines
on the technochemical control of alcohol production - Moscow: Agropromizdat, 1986. - 400 p.