INTRODUCTION
Modern confectioners prioritize new formulations
with a reduced sugar content, lower energy value,
extended shelf life, and improved quality. The
quality of confectionery products is determined by
physicochemical and microbiological processes that take
place throughout their shelf life. These processes depend
on the product’s chemical composition, ingredient
ratios, storage conditions, moisture content, pH, water
activity, and moisture transfer. The main indicators of
jelly quality are moisture content, water activity, and
pH. They depend on the formulation, the content and
properties of carbohydrate-containing components, as
well as storage conditions [1, 2].
Confectionery products vary in moisture that
binds nutrients and regulates the product’s texture and
structure. Products with high moisture contain larger
amounts of free and chemically unbound water that
intensifies biological processes and causes damage to
products [3]. Free water is responsible for molds, yeasts,
and bacteria, as well as toxins. It is involved in chemical
and biochemical reactions that can affect the product’s
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texture, aroma, color, taste, nutritional value, stability,
and shelf life [4].
Regulatory requirements for confectionery products
include an indicator of water content (W, %). However,
this indicator cannot assess how well water is bound to
food substances and how this may affect the quality of
the product during storage [5].
What is vital for microorganisms is not the absolute
content of water in the product but its availability, or
water activity (Аw). This indicator is defined as Аw = Р/Р0,
i.e., the ratio of water vapor pressure over the surface
of the product (Р) and vapor pressure over pure
water (Р0) [6].
The relative equilibrium moisture is based on
the partial pressure of water vapor over the product
and depends on the product’s chemical composition,
moisture content, storage conditions (temperature and
relative air humidity), type of packaging, etc. [7].
The Аw limits for microorganisms in food products
are 0.83–0.98 for bacteria, 0.81–0.88 for yeasts, and for
0.70–0.88 molds. However, some types of mold fungi
and osmophilic yeasts can grow even at Аw = 0.62. That
is why fungi and yeast contents are included in those
microbiological indicators that determine the product’s
stability during storage. All types of microorganisms
are capable of reproduction at Аw > 0.95 and none can
reproduce at Аw < 0.6.
The pH and redox potential values have a significant
effect on the growth of microorganisms. Products with
pH < 3.7 are safe from spoilage, with only lactic acid
bacteria and certain yeasts and molds able to develop in
them, while products with pH of 5.0 to 7.0 are exposed
to risks associated with pathogenic microorganisms [8].
Based on water activity (Аw), products can be divided
into high moisture (Аw ˃ 0.9), intermediate moisture
(0.6 ˂ Аw ˂ 0.9), and low moisture (Аw ˂ 0.6) products.
Low moisture prevents microbiological processes in the
product, contributing to a long shelf life. Intermediate
moisture creates favorable conditions for predominantly
microbiological and enzymatic processes with a growth
of yeasts, molds, and some types of bacteria, thus
causing the products to dry out and become stale during
storage. High moisture products are vulnerable to all
types of microorganisms and therefore have a short shelf
life [9].
Reducing the water activity index can effectively
prevent microbiological spoilage and some chemical
reactions in food products that reduce their quality
during storage. For this, a number of methods are
applied including concentration, dehydration, drying,
freezing, increasing osmotic pressure over the product,
and using microorganism growth inhibitors. There
are also active ingredients that bind water and thereby
prevent or significantly slow down its evaporation.
These are specific enzymes, emulsifiers, carbohydratecontaining
hygroscopic substances, salts, and waterretaining
agents. The strength of water binding
depends on the origin and chemical composition of the
ingredients used, as well as pH and temperature of the
medium [10, 11].
The carbohydrate composition of fruit jelly has a
significant impact on its consumer properties during
storage. Jelly is a sugary confectionery product. Despite
its popularity, it has a number of disadvantages: high
sugar content (70–85% of easily digestible sugars),
high energy value (300–360 kcal/100 g), sweetness,
high glycemic index, and an unbalanced composition.
According to its chemical composition and structure,
jelly belongs to complex colloidal systems. Its
osmotically retained moisture has a limited energy
of binding with the product’s components. Jelly is an
intermediate moisture (15–30%) product [12, 13].
During storage, even with all requirements met,
jelly gradually becomes exposed to moisture exchange
(shrinkage) and sucrose crystallization, with its
appearance and structure deteriorating as well [13].
However, when stored at elevated temperatures and
relative humidity over 70%, jelly is vulnerable to mold
due to the sorption of moisture on its surface. This
results in its wetting, with an increase in the Аw index
to 0.9 and a growth in Aspergillus and Penicillium
fungi, yeast, and, to a lesser extent, bacteria [15]. The
lower limit of jelly moisture for mold fungi is 15%, but
under improper storage conditions, spoilage can occur
even with a higher dry matter content. With a sugar
concentration up to 60–65% and increased moisture,
some races of yeast can cause fermentation, especially
alcoholic, which gives the product an unpleasant
pungent odor [16].
Jelly drying can be prevented and water activity
reduced by introducing sugar-containing substances
with a high content of reducing agents and waterretaining
components (polysaccharides, glycerol,
polyhydric alcohols, some sweeteners, starch, proteins,
amino acids, lactic acid, etc.) [17].
Fruit jelly is made with natural gel-forming agents
such as agar-agar, pectin, gelatin, carrageenans, gum
arabic, xanthan gums, etc. These are hydrocolloidal
polysaccharides that bind water in jelly, like sugar,
making it less available for microorganisms to
develop [18–20].
Pectin is the best water-retaining gelling component
for jelly. It is a natural polysaccharide with water-soluble
fiber properties. Pectin is widely used in therapeutic
and preventative nutrition due to its normalizing
effect on many vital processes without disturbing
the bacteriological balance of the body. In particular,
it improves digestion, lowers blood cholesterol,
normalizes blood sugar, and removes ions of toxic
metals, pesticides, radionuclides, xenobiotics, anabolics,
metabolic products, and excess urea from the body. It
is recommended to people with disturbed carbohydrate
and lipid metabolism, immune and bacterial diseases,
obesity, and atherosclerosis [21].
Carbohydrates not only determine sensory,
functional, and technological properties of a product,
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but they also regulate its acidity and have a preservative
antimicrobial effect. Adding sugars increases the
binding energy of water in the material and decreases
the rate of chemical reactions, reducing water activity
and microbial growth [22]. However, not only the
quantity of sugars is important but also their qualitative
composition. For example, apple jam with 32.6%
moisture has a lower Аw index (0.825) than butter cream
with 15.2% moisture (0.851) due to a significant content
of sugar and reducing sugars [23].
Monosaccharides have the greatest ability to
bind water and reduce water activity, followed by
disaccharides and polysaccharides. Sugar-containing
substances can be arranged in the following order based
on their ability to reduce the Аw index in products [24]:
Amylopectin Maltohexaose
Maltotriose Sucrose Maltose
Lactulose Glucose Fructose
Xylose Glycerin.
Replacing white sugar with alternative starch
products is one of the ways to reduce sweetness
and easily digestible sugars, slow down drying and
staling, and keep jelly fresh during storage. These
alternative materials, e.g., starch syrup and glucosefructose
syrup, vary in carbohydrate composition and
are technologically advantageous, inexpensive, and
domestically produced in large quantities.
We aimed to study the quality of starch syrup
(low-conversion, confectionery, and high-conversion)
and glucose-fructose syrup, as well as their effect on
the sensory, physicochemical, and microbiological
parameters of jelly with different carbohydrate profiles
after manufacture and during storage.
STUDY OBJECTS AND METHODS
Samples of starch syrup and glucose-fructose syrup
(Kargill Company, Russia) were analyzed according to
State Standard 33917-2016 and Specifications 10.62.13-
001-00343579-2016 for the following parameters by
using the following methods:
– the dry matter content: by the refractometric method;
– the content of reducing substances: by the Lane-Eynon
method;
– the content of carbohydrates: by high performance
liquid chromatography on a Shimadzu LC-2010
chromatograph with a RID-10A refractometric detector;
– pH value: by measuring the activity of hydrogen ions
on a Testo 206 pH meter;
– acidity: by titration; and
– nutritional value: by calculation.
The jelly samples were based on apple pectin. The
control sample was based on sugar and confectionery
syrup in a ratio of 1:0.5. The experimental samples were
free of white sugar and based on starch syrup (lowconversion,
confectionery, and high-conversion) and
glucose-fructose syrup.
The sensory quality of the jelly samples was
evaluated on a 5-point scale by the descriptor-profile
analysis according to State Standard ISO 13299-
2015 [25]. It involved the following parameters and
methods of their determination:
– the water content: by the refractometric method (State
Standard 5900);
– the content of reducing substances: by the ferricyanide
method (State Standard 5903);
– titratable acidity: by titration; and
– active acidity (pH): by the potentiometric method
(State Standard 5898).
Water activity was measured by using a HygroPalm
hygrometer (Rotronic, Switzerland) on a scale from
0 to 1, with an absolute error of ± 0.008 (± 0.1°C for
temperature). The microbiological indicators were
evaluated against State Standard 6442-2014 and
Technical Regulations of the Customs Union 021/2011.
In particular, we applied microbiological research
methods to determine the total aerobic mesophilic count
(State Standard 10444.15-94), coliform bacteria (State
Standard 50474-93), and spoilage microorganisms (State
Standard 10444.12- 88).
The jelly samples were stored in food-grade
polyethylene terephthalate containers for 12 weeks at
21.0 ± 1.5°C and relative humidity of 82 ± 2%.
To prepare the control sample, apple pectin was
mixed with white sugar in a ratio of 1:3. The resulting
dry mixture was gradually added to hot water (70–75°С)
and vigorously stirred until a homogeneous water-pectin
mixture was obtained with a dry matter content of
25 ± 1%. Then, we added the remaining amount of white
sugar, starch syrup heated to 50–55°C, and buffer salt
(sodium lactate), stirred the mixture, and boiled it to
obtain a jelly mass with a 27–29% water content. The
mass was then cooled to 85–90°C, with citric acid and
а food flavoring agent introduced into it. The jelly mass
was poured into rigid molds to mature, dry, and cool.
The experimental samples were prepared according
to the same method as the control, with erythritol
used instead of white sugar (Fig. 1). Their ingredients,
carbohydrate composition, and energy value are
presented in Table 1.
RESULTS AND DISCUSSION
First, we studied the quality indicators of three
types of starch syrup (low-conversion, confectionery,
and high-conversion) and glucose-fructose syrup
in comparison with those of sugar syrup used to
prepare the control sample. The starch syrups differed
significantly in their carbohydrate composition. They
contained easily digestible reducing sugars (glucose
and maltose) and polysaccharides (dextries and
trisaccharides), with the latter responsible for dietetic
properties (Table 2). In addition, the syrups contained
minerals (0.10–0.37%) such as potassium, phosphorus,
sodium, calcium, magnesium, and iron [26]. Unlike
sugar syrup, starch syrup is free of sucrose and fructose,
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Figure 1 Process chart for jelly samples based on sugar-free starch syrup or glucose-fructose syrup
Table 1 Ingredients, carbohydrate composition, and energy value of jelly samples with different carbohydrate profiles
Name of material Control
(sugar and confectionery
syrup)
Experimental sugar-free samples based on:
Low-conversion
syrup
Confectionery
syrup
High-conversion
syrup
Glucose-fructose
syrup
Ingredients: “+” – present, “–” – absent
White sugar + – – – –
Low-conversion syrup – + – – –
Confectionery syrup + – + – –
High-conversion syrup – – – + –
Glucose-fructose syrup – – – – +
Erythritol – + + + +
Apple pectin + + + + +
Sodium lactate (40%) + + + + +
Citric acid (50%) + + + + +
Food flavoring agent + + + + +
Carbohydrates, g/100 g:
total 79.1 74.6 74.4 72.2 79.0
reducing sugars 14.9
(glucose, maltose,
fructose)
27.8
(glucose,
maltose)
33.2
(glucose,
maltose)
45.8
(glucose,
maltose)
77.3
(glucose,
maltose)
polysaccharides 13.7 46.9 41.4 26.2 –
Energy value, kcal 301 311 309 302 311
Erythritol
Citric acid
Food flavoring agent
Pouring into
rigid molds
Tempering of jelly
mass (t = 85–90оС)
Sampling, maturation,
and drying
Cooling
Coating
Sorting
and packaging by mass
Apple
pectin
Water
(Т=70–75оС)
Preparing
a pectin solution
Boiling of jelly mass
(Тboil=106–108оС, DM=71–73%)
Preparing
a formulation mixture
Apple
pectin
Starch syrup
or glucose-fructose syrup
Sodium lactate
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syrup contained more reducing sugars and fewer
polysaccharides (45.8 and 26.2%, respectively) than the
other experimental samples. The glucose-fructose syrup
sample contained more reducing sugars (77.3%) than the
other samples but no sucrose or polysaccharides.
Thus, all the samples based on starch syrup
contained 1.9–3.4 times more polysaccharides and
1.4–2.4 times fewer reducing sugars than the control.
However, the sample based on glucose-fructose syrup
had a 1.2 times higher content of reducing sugars.
The sensory evaluation of the jelly samples was
based on the quantitative descriptor-profile analysis. In
this analysis, each of the main sensory indicators (taste,
color, smell, texture) is presented as a set of components
a highly hygroscopic reducing carbohydrate that
significantly increases jelly’s wettability during storage.
All the types of starch syrup had a lower sweetness
coefficient (by 0.2–0.5 units), lower values of active
acidity (by 1.3–1.7 pH units), and a higher ash content
(2.0–7.4 times) than the sugar syrup. The highconversion
syrup contained the largest amount of
reducing sugars (62.6%, including 31.8% glucose
and 30.8% maltose) and the smallest amount of
polysaccharides (19.9%). The low-conversion syrup, on
the contrary, had the highest content of polysaccharides
(46.8%) and the lowest content of reducing sugars
(32.3%, including 14.5% glucose and 17.8% maltose).
The confectionery syrup contained 40.4% of reducing
sugars (20.8% glucose, 19.6% maltose) and 38.3% of
polysaccharides. The glucose-fructose syrup had a lower
value of active acidity (by 3.6 pH units) and a higher
sweetness coefficient (by 1.2) than the sugar syrup. This
was due to its significant content of easily digestible
reducing sugars (70.5%, including 28.6% fructose,
38.8% glucose, 3.1% maltose) and the absence of sucrose
and polysaccharides.
Replacing sugar with starch syrup or glucosefructose
syrup significantly changed the carbohydrate
composition of the jelly samples (Table 1). This not
only depended on the chemical composition of the
raw materials but also the chemical processes in the
jelly mass during boiling. Unlike the control, the
experimental samples contained no sucrose.
The control sample had 65.4% of easily digestible
carbohydrates, including 50.5% of sucrose and 14.9% of
reducing sugars (fructose, glucose, and maltose), as well
as 13.7% of polysaccharides. The samples based on lowconversion
syrup had a lower content of reducing sugars
(glucose and maltose) and more polysaccharides (27.8
and 46.9%, respectively) than the other experimental
samples. The samples based on confectionery syrup
contained 33.2% of reducing sugars and 41.4% of
polysaccharides. The samples based on high-conversion
Figure 2 Sensory evaluation of jelly samples with various
carbohydrate profiles
0
1
2
3
4
5
Sweetness
Taste richness
Cooling effect
Presence of yellow
tint
Color saturation
Transparency
Material-specific smell
Smell intensity
Off-odor
Jelly-like texture
Viscoelasticity and
plasticity
Stickiness
Control
Low-conversion syrup
Confectionery syrup
High-conversion syrup
Glucose-fructose syrup
0
1
2
3
4
5
Sweetness
Taste richness
Cooling effect
Presence
of yellow tint
Transparency
Color saturation
Material-specific smell
Smell intensity
Off-odor
Viscoelasticity
and plasticity
Jelly-like
texture
Stickiness
Table 2 Quality indicators and carbohydrate composition of starch syrup, glucose-fructose syrup, and sugar syrup
Quality indicators
and carbohydrates
Sugar syrup
(1:0.5)
Starch syrup Glucose-fructose syrup
Low-conversion Confectionery High-conversion
Dry matter content, % 80.2 79.3 78.9 83.0 70.6
Content of reducing substances
(or dextrose equivalent), %
14.5 32.3
(26–35*)
40.4
(36–44*)
62.6
(45 and over*)
70.5
Content of carbohydrates, %: 80.1 79.1 78.7Ц 82.5 70.5
– sucrose 50.6 – – – –
– glucose 6.3 14.5 20.8 31.8 38.8
– fructose 2.5 – – – 28.6
– maltose 5.7 17.8 19.6 30.8 3.1
– polysaccharides (dextrins) 15.0 46.8 38.3 19.9 –
Active acidity, pH units 6.4 5.1 5.0 4.7 3.6
Sweetness coefficient, units 0.8 0.3 0.4 0.6 1.2
* according to State Standard 33917-2016
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(or descriptors) that are scored by the panelists
according to their presence and intensity. The results are
graphically depicted in the form of a profile diagram.
In our study, 20 panelists aged 19–23 evaluated
the following sensory indicators of the jelly samples
(descriptors listed in brackets): taste (sweetness,
richness, cooling effect); color (yellow tint, saturation,
transparency); smell (material-specific smell, intensity,
off-odor); and texture (jelly-like, viscoelasticity and
plasticity, stickiness).
Figure 2 shows the profile diagram of the jelly
quality evaluated on a 5-point scale of intensity with
weight coefficients representing the significance of each
indicator.
The descriptor-profile analysis showed that the
samples based on high-conversion syrup and glucosefructose
syrup had the greatest sweetness, taste richness,
color saturation, and transparency. Also, the sample with
glucose-fructose syrup had a slight effect of stickiness
on its surface. This was because it had the highest
content of reducing sugars (mostly fructose) which turn
into coloring, humic substances and aldehydes during
boiling and intensify the product’s color, aroma, and
hygroscopicity.
The jelly based on low-conversion syrup had the
lowest sweetness, taste richness, and color brightness,
as well as low texture density and elasticity. These
values can be explained by its highest content of
polysaccharides which bind less water and therefore
make the product less viscous and strong. The sample
based on confectionery syrup had the most optimal
profile, with moderate sweetness and taste richness,
good jelly-like texture, viscoelasticity, and plasticity, no
effect of wetting or stickiness, and a color similar to that
of the control.
The jelly samples with various carbohydrate
compositions were packed in plastic containers
and stored for 12 weeks to study changes in
their water content (W), water activity (Aw), and
pH (Table 3). The initial (after preparation) water
contents in the control sample, the starch syrupbased
samples, and the jelly based on glucosefructose
syrup were 20.8 ± 0.2, 19.1 ± 0.2–20.0 ± 0.1,
and 20.6 ± 0.1, respectively. Тheir pH values were
3.4, 3.0–3.3, and 2.8, respectively.
All the jelly samples showed a gradual decrease in
the water content and changes in water activity during
storage. After 12 weeks of storage, the control sample
had the highest loss of water (38.9%), compared to the
experimental samples (17.0–28.3%). This was because
it contained a significant amount of sucrose (50.6%)
and a small amount of reducing substances (14.9%). In
the process of moisture transfer during storage, sucrose
crystallization centers gradually began to develop on
the sample’s surface. They subsequently grew in size
forming a thin crystalline sugar crust and gradually
sugaring the whole product. During this process, free
moisture quickly left the intercrystalline space, causing
the product to dry out and stale.
The jelly based on low-conversion syrup was losing
water more slowly than the control but faster than the
other experimental samples at the beginning of storage.
This was due to its significant content of polysaccharides
(46.9%), which bind and retain water to a lesser extent
than reducing substances. Since mold appeared on its
surface after 5 weeks of storage, the studied parameters
were no longer determined. The jellies based on
confectionery syrup and high-conversion syrup had
lower water losses (28.3 and 24.5%, respectively),
compared to the control. The lowest water loss (17.0%)
was registered in the sample based on glucose-fructose
Table 3 Water content changes in the jelly samples with various carbohydrate profiles during storage
Storage time, weeks Water content in the jelly samples based on
Sugar and
confectionery syrup
(control)
Low-conversion
starch syrup
Confectionery
starch syrup
High-conversion
starch syrup
Glucose-fructose
syrup
0 (after drying) 20.8 ± 0.2 19.5 ± 0.1 19.1 ± 0.2 20.0 ± 0.1 20.6 ± 0.1
1 19.4 ± 0.1 18.1 ± 0.1 18.7 ± 0.3 19.6 ± 0.1 20.1 ± 0.1
2 18.8 ± 0.1 17.8 ± 0.2 18.4 ± 0.3 19.1 ± 0.1 19.8 ± 0.2
3 17.3 ± 0.1 17.6 ± 0.3 17.9 ± 0.2 18.9 ± 0.2 19.5 ± 0.1
4 16.8 ± 0.2 17.3 ± 0.2 17.5 ± 0.2 18.6 ± 0.1 19.1 ± 0.2
5 16.3 ± 0.3 17.1 ± 0.1 17.2 ± 0.2 18.2 ± 0.2 18.9 ± 0.1
6 15.9 ± 0.2 mold appeared on
the surface.
water content not
determined
16.8 ± 0.1 17.8 ± 0.1 18.7 ± 0.1
7 15.4 ± 0.2 16.2 ± 0.2 17.4 ± 0.2 18.5 ± 0.3
8 15.0 ± 0.1 15.6 ± 0.2 16.8 ± 0.2 18.2 ± 0.2
9 14.6 ± 0.2 15.0 ± 0.2 16.4 ± 0.3 17.9 ± 0.1
10 14.1 ± 0.1 14.7 ± 0.1 15.9 ± 0.2 17.7 ± 0.2
11 13.5 ± 0.3 14.1 ± 0.2 15.6 ± 0.2 17.4 ± 0.2
12 12.7 ± 0.1 13.7 ± 0.2 15.1 ± 0.1 17.1 ± 0.1
Changes in water content after 3 months of storage, % of the initial value:
ΔW, % –38.9 – –28.3 –24.5 –17.0
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Figure 3 shows the changes in water activity in the
packaged jelly samples during 12 weeks of storage. As
we can see, the longer was the storage time, the lower
was water activity in all the samples. We also found that
the lower was the water loss, the more changes in water
activity it caused (Fig. 4).
The decrease in water activity was associated with
two processes – water loss during storage and the use of
starch products with a different ratio of mono-, di-, and
polysaccharides. Monosaccharides reduce water activity
to a greater extent than disaccharides due to their
solubility and hygroscopicity. The solubility of monosyrup.
It contained the largest amount of reducing
substances (fructose and glucose), which contributed to
slower drying and greater freshness preservation.
Thus, the jelly’s carbohydrate composition (the ratio
of mono-, di-, and polysaccharides) significantly affected
the process of moisture exchange during storage and
therefore the product’s drying and staling. Using various
types of starch syrup and glucose-fructose syrup with a
high content of reducing sugars (especially glucose and
fructose with higher solubility than maltose or dextrins)
significantly slowed down the drying of jelly and
increased its shelf life.
Figure 3 Water activity in jellies with various carbohydrate compositions during storage: 1 – control (based on sugar and
confectionery syrup); sugar-free samples: 2 – based on low-conversion syrup; 3 – based on confectionery syrup; 4 – based
on high-conversion syrup; 5 – based on glucose-fructose syrup
0.4
0.5
0.6
0.7
0.8
0.9
0 1 2 3 4 5 6 7 8 9 10 11 12
Water activity, Аw
Storage time, weeks
2
3
5
4
1
Mold appeared, the parameter
no longer determined
Figure 4 Water activity in jellies with various carbohydrate compositions after preparation and after 12 months of storage:
1 – control (based on sugar and confectionery syrup); sugar-free samples: 2 – based on low-conversion syrup; 3 – based on
confectionery syrup; 4 – based on high-conversion syrup; 5 – based on glucose-fructose syrup
0.724
0.839
0.789
0.749
0.664
0.401
0.573
0.421 0.402
0.4
0.5
0.6
0.7
0.8
0.9
1 2 3 4 5
after preparation after 12 months of storage
Water activity, Аw
43.8 %
Mold
appeared,
the parameter
no longer
determined
44.6 %
27.4 %
39.5 %
Jelly samples
0.724
0.839
0.789
0.749
0.664
0.401
0.573
0.421 0.402
0.4
0.5
0.6
0.7
0.8
0.9
1 2 3 4 5
after preparation after 12 months of storage
Water activity, Аw
43.8 %
Mold
appeared,
the parameter
no longer
determined
44.6 %
27.4 %
39.5 %
Jelly samples
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Table 4 Sensory indicators of jelly samples with various carbohydrate profiles during storage*
Indicator Jelly samples based on
Sugar and
confectionery syrup
(control)
Low-conversion
starch syrup
Confectionery
starch syrup
High-conversion
starch syrup
Glucose-fructose
syrup
Taste, color, smell Sickeningly sweet,
bright yellow,
no off-odor
Slightly sweet,
yellow-beige,
a subtle smell of
syrup
Moderately sweet,
yellow with a
golden tint, a subtle
smell of syrup
Sweet, yellow, no
off-odor
Sweet,
bright yellow with
an orange tint,
no off-odor
Texture Homogeneous, jelly-like, viscoelastic, plastic,
Quite dense Slightly dense Quite dense Quite dense Quite dense
Shape Regular, with an
indistinct contour
due to sucrose
crystallization on
the surface
Regular,
with a clear contour,
no deformation
Regular,
with a clear
contour,
no deformation
Regular,
with a clear
contour,
no deformation
Regular, with an
indistinct contour
due to sagging of
wet areas of the
surface
Surface Not sticky,
covered with a fine
crystalline sugar
crust, transparent
Not sticky,
without a crystalline
crust,
transparent
Not sticky,
without a crystalline
crust,
transparent
Not sticky, a fine
crystalline crust
beginning to form
due to glucose
crystallization,
transparent
Slightly wet and
sticky,
transparent
*The control and the experimental samples based on confectionery syrup, high-conversion syrup, and glucose-fructose syrup were evaluated after
12 weeks of storage; the sample based on low-conversion syrup was evaluated after 5 weeks of storage
and disaccharides varies greatly, amounting (at 100 °C)
to 98.4, 87.7, 86.1, and 82.9% for fructose, glucose,
maltose, and sucrose, respectively [27, 28]. Fructose
contributes to the greatest decrease in water activity,
followed by glucose, maltose, and sucrose. The tendency
of sugar molecules to hydration is associated with the
presence of hydroxyl and aldehyde groups capable of
forming hydrogen bonds with water molecules. The
more reducing sugars the product contains, the more
they bind water molecules and slow down its staling [29].
According to the sorption isotherm (Fig. 5), the
initial water activity values in all the jelly samples
ranged from 0.664 ± 0.012 to 0.839 ± 0.011. Therefore,
we can classify them as intermediate moisture products.
Figure 5 shows a certain correlation between the
water content and the water activity index that is
determined by both the content of carbohydrates and
their ratio in the sample. The control sample had the
greatest decrease in water activity, namely 44.6%
(Fig. 4). The sample based on low-conversion syrup
had the highest initial value of water activity (0.839).
This was due to its low content of reducing sugars with
a preservative effect and high water-binding capacity,
which led to gradual molding after 5 weeks of storage.
The water activity values of the samples based on highconversion
syrup and glucose-fructose syrup were
initially lower than in the other samples (0.749 and
0.664, respectively). After 12 weeks of storage, they
decreased more than in the other samples (by 43.8
and 39.5%, respectively) due to significant amounts of
reducing sugars in their composition (45.8 and 77.3%,
respectively). The sample based on confectionery syrup
had the lowest decrease in water activity, namely 27.4%
(Fig. 4). During storage, this sample dried more slowly
than the control. It did not get wet and retained its
viscoelasticity and plasticity, with no crystalline crust
forming on its surface.
The sensory indicators of the jelly samples after
12 weeks of storage are presented in Table 4.
The antimicrobial effect of carbohydrates is
primarily based on decreasing water activity, which
slows down most chemical reactions responsible for the
product’s deterioration, increases the binding energy
of water, and reduces the ability of microorganisms to
use it for metabolism. High water content (21–15%) and
water activity (0.6–0.8) in jelly are among the causes of
its microbiological spoilage, leading to the development
of molds and yeasts [30, 31].
In our samples, the water content was 19.1–20.8%
and water activity varied from 0.664 ± 0.012 to 0.839 ±
0.011, which might indicate possible development of
microorganisms and mold. Therefore, we decided
to study changes in the microbiological indicators
throughout the entire shelf life of the jelly samples.
Based on the Technical Regulations of the Customs
Union 021/2011, we determined the total number
of pathogenic microorganisms, aerobic mesophilic
bacteria, molds and yeasts, spore-forming bacteria, and
coliform bacteria in the jelly samples. We analyzed
their microbiological stability after storage and found
that the indicators under study did not exceed the
tolerance levels in the control and the experimental
samples based on confectionery syrup, high-conversion
syrup, and glucose-fructose syrup. Also, we detected no
pathogenic microorganisms or coliform bacteria in the
samples (Table 5).
270
Plotnikova I.V. et al. Foods and Raw Materials. 2022;10(2):262–273
high acidity could be used to increase the carbohydrate
content and acidity in the product.
Thus, changing the concentration of carbohydrates
with different water-retaining properties can have
an additional preservative effect on jelly in combination
with other technological factors. The risk of
microbiological spoilage can be reduced not only by
adjusting the formulation (lowering water activity
and pH), but also by ensuring low levels of initial
microbiological contamination of the product.
CONCLUSION
Our study showed that jelly can be produced
with various types of starch syrup (low-conversion,
confectionery, and high-conversion) or glucose-fructose
syrup used instead of white sugar. This can expand the
range of jellies with different carbohydrate profiles and
prolong their shelf life.
We found that using starch or glucose-fructose
syrups significantly changed the carbohydrate
composition of the jelly. Unlike the control, the
experimental samples did not contain any sucrose. The
starch syrup-based samples had more polysaccharides
(1.9–3.4 times) and fewer easily digestible reducing
sugars (1.4–2.4 times), while the sample with glucosefructose
syrup had a higher content of reducing sugars
(1.2 times) than the control. The sample based on
confectionery syrup had the most optimal profile, with
moderate sweetness and taste richness, good jellylike
texture, viscoelasticity and plasticity, no effect of
wetting or stickiness, and the color similar to that of the
control sample.
Different amounts and ratios of mono-, di-, and
polysaccharides significantly affected the moisture
transfer and the preservation of jelly freshness after
12 weeks of storage. The control sample had the
greatest water loss (38.9 %), compared to the experimental
samples. The samples based on high-conversion
syrup and glucose-fructose syrup were least subjected
to drying due to high contents of reducing sugars,
especially fructose and glucose, highly hygroscopic
sugars that can bind water and slow down the process
The jelly based on low-conversion syrup had its
counts of aerobic mesophilic bacteria, molds, and yeasts
exceeding the tolerance levels 2.3, 1.9, and 1.8 times,
respectively. This can be explained by a low content of
reducing sugars with a preservative effect and a high
water activity index in this sample. To improve its
microbiological indicators and reduce water activity, a
larger amount of a preservative agent should be added
to its formulation. For example, it could be a sweetener
with low sugar and calorie contents and a high waterbinding
capacity (erythritol, sorbitol, xylitol, etc.).
Alternatively, some food acid or concentrated juice with
Table 5 Microbiological indicators of jelly samples with various carbohydrate profiles during storage*
Indicator Technical
Regulations
of the Customs
Union 021/2011
(tolerance)
Jelly samples based on
Sugar and
confectionery
syrup
(control)
Lowconversion
starch
syrup
Confectionery
starch
syrup
Highconversion
starch
syrup
Glucosefructose
syrup
Pathogenic microorganisms, incl.
salmonella (not allowed), g
25 Not detected
Aerobic mesophilic bacteria, CFU/g max 1×103 1.5×102 2.3×103 0.8×103 2.8×102 1.4×102
Coliform bacteria (not allowed), g (cm3) 0.1 Not detected
Molds, CFU/g max 100 24 105 64 43 16
Yeast, CFU/g max 50 18 54 36 24 14
*The control sample and the experimental samples based on confectionery syrup, high-conversion syrup, and glucose-fructose syrup were
evaluated after 12 weeks of storage; the sample based on low-conversion syrup was evaluated after 5 weeks of storage
Figure 5 The sorption isotherm of the jelly samples with
various carbohydrate compositions: 1 – control (based on
sugar and confectionery syrup); sugar-free samples:
2 – based on low-conversion syrup; 3 – based on confectionery
syrup; 4 – based on high-conversion syrup;
5 – based on glucose-fructose syrup
R² = 0.9963
0.35
0.45
0.55
0.65
0.75
0.85
12 14 16 18 20 22
Water activity, Aw
Water content, %
1 2 3 4 5
А
А
А
А
А
B
C
C
C
C
Storage time:
А – 0 weeks (after drying);
B – 5 weeks (appearance of mold);
C – 12 weeks.
R² = 0.9963
0.35
0.45
0.55
0.65
0.75
0.85
12 14 16 18 20 22
Water activity, Aw
Water content, %
1 2 3 4 5
А
А
А
А
А
B
C
C
C
C
Storage time:
А – 0 weeks (after drying);
B – 5 weeks (appearance of mold);
C – 12 weeks.
R² = 0.9963
0.35
0.45
0.55
0.65
0.75
0.85
12 14 16 18 20 22
Water activity, Aw
Water content, %
1 2 3 4 5
А
А
А
А
А
B
C
C
C
C
Storage time:
А – 0 weeks (after drying);
B – 5 weeks (appearance of mold);
C – 12 weeks.
271
Plotnikova I.V. et al. Foods and Raw Materials. 2022;10(2):262–273
of staling. The water activity index of the jelly samples
after preparation ranged from 0.664 ± 0.012 to 0.839 ±
± 0.011, so they were classified as intermediate moisture
products. After storage, this index decreased most in the
samples based on high-conversion and glucose-fructose
syrups and least in the sample based on confectionery
syrup.
The microbiological indicators of all the samples,
except for the jelly based on low-conversion syrup,
did not exceed the standard tolerance levels. Neither
did we detect any pathogenic microorganisms or
coliform bacteria in them. The jelly based on lowconversion
syrup had its counts of aerobic mesophilic
bacteria, molds, and yeasts exceeding the tolerance
levels 2.3, 1.9, and 1.8 times, respectively. To improve
its microbiological indicators and reduce water
activity, a larger amount of a preservative should
be added to its formulation, such as a sweetener
(erythritol, sorbitol, xylitol, etc.), a food acid, or
a concentrated juice with high acidity that can
increase the carbohydrate content and acidity in the
product.
CONTRIBUTION
I.V. Plotnikova reviewed the literature on the
study problem, proposed a methodology for the
experiment, conducted the experiment, processed
experimental data, performed calculations, and edited
the manuscript. G.O. Magomedov developed the study
concept and supervised the experiment. I.M. Zharkova
reviewed the literature on the study problem and
edited the manuscript. E.N. Miroshnichenko edited the
manuscript for submission. V.E. Plotnikov conducted
the experiment, processed experimental data, and
performed calculations.
CONFLICT OF INTEREST
All the authors were equally involved in writing the
manuscript and are responsible for plagiarism.
ACKNOWLEDGEMENTS
We thank Raisa I. Ivanova, General Director of the
Confectionery Factory (Vologda), for providing raw
materials and an opportunity to test the samples in
industrial conditions.

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