Volume 19
Issue 3
Food Science and Technology
JOURNAL OF
POLISH
AGRICULTURAL
UNIVERSITIES
Available Online: http://www.ejpau.media.pl/volume19/issue3/art-01.html
EFFECT OF SACCHAROSE ON RHEOLOGICAL AND TEXTURAL PROPERTIES OF YOGHURT MIMETICS BASED ON INULIN AND WHEY PROTEIN
Kamil Toczek, Paweł Glibowski, Sylwia Tracz
Department of Biotechnology, Human Nutrition and Science of Food Commodities, Faculty of Food Science and Biotechnology, University of Life Sciences in Lublin, Poland
Nowadays yoghurts belong to significant group of dairy products.
Apart from having good taste, they also have dietetic and healthy values. The
present work was established to study possibility of obtaining a model, yoghurt-type
product based on inulin and whey with addition of saccharose. Texture profile
analysis including hardness, adhesiveness, cohesiveness was analyzed. Additionally
viscosity and pH were determined. The studies showed that samples with a 15%
inulin were characterized by higher values for most of the tested textural and
rheological features. Yoghurt mimetics with 15% content of inulin were firmer
in comparison with mimetics containing 13% inulin. The results showed no link
between the content of inulin and cohesiveness. Rheological and textural properties
of yoghurt mimetics were not clearly affected by saccharose concentration
Key words: yoghurt, inulin, whey protein, saccharose.
INTRODUCTION
Yogurts are one of the most dynamically developing groups of dairy products. The nutritional value of milk fermented beverages is as high as milk, whereas the dietetic and healthy value of yoghurt is unique and incomparable with milk. This value results from the biological activity of live lactic acid bacteria [19]. More and more yoghurts contain all sorts of additives that maintain the appropriate structure, preventing syneresis and substances that stimulate growth of lactic acid bacteria. Such substances include inulin and whey proteins [18].
Oligofructose and inulin are one of the best known prebiotics. They are added to a fermented food to improve the survival rate of probiotic bacteria during storage [11]. They are also added to all kinds of confectionery and bakery products [13]. Inulin is a natural carbohydrate belonging to the fructans. It can be produced from chicory, dahlia tubers and Jerusalem artichoke. It may be a substitute for fat, sweetener, filler; therefore it has numerous applications in the food industry [8]. It consists of several tens of fructose molecules linked by Beta (2 → 1) and a single glucose molecule attached to the reducing end of the chain. Depending on the source, inulin may have a different degree of polymerization. It is not digested in the small intestine reaching the large intestine essentially intact, where is fermented [2, 3, 14, 15].
In the yoghurt production, whey proteins are also used. The nutritional value of whey proteins are high and results from their amino acid composition [12]. Like inulin, they are widely applied in the dairy industry as well as in the meat industry, baking industry or confectionery. Whey proteins increase the nutritional value of products, improve the sensory and organoleptic properties, and due to their capacity to bind water, they have an effect on the rheological properties of products (e.g. viscosity) [5].
The aim of this work was to research the possibility of obtaining a product similar to yoghurt based on inulin as a texturizing agent and whey powder as a carbon source for yoghurt bacteria. The influence of saccharose on rheological and textural properties also was investigated.
MATERIAL AND METHODS
Material
Whey powder SICALAC® (Euroserum, Port-sur-Saône, France), containing
72.5% lactose, 11.5% protein, 8.5% ash, 1.5% fat, and 3% water (manufacturer's
data), inulin Frutafit®Tex! with a degree of polymerization ≥23 (Sensus
Operations C.V., Roosendaal, The Netherlands), saccharose (DIAMANT, Poland),
lyophilized yoghurt culture Yo-Flex (YC-X11 Yo-Flex Thermophilic Lactic Culture
type Yoghurt CHR; Chr. Hansen, Poland) containing Streptococcus thermophilus and Lactobacillus
delbrueckii subsp. bulgaricus (total cell count cfu/g: ≥1E+11)
were used for yoghurt mimetics production.
Methods
Two versions of yoghurt mimetics containing different amounts
of inulin – 13
and 15% were prepared. The solutions were prepared by mixing a whey powder (6.25%)
with distilled water at room temperature using a magnetic stirrer HS MS 11 (Wigo)
until completely dissolved. During stirring, saccharose and inulin were added.
These solutions were covered with aluminum foil to prevent evaporation. The solutions
were placed in a water bath at 70°C for 30 min and mixing occasionally. After
this time, the solutions were cooled to a temperature below 45°C. Then, Direct
Vat Set yoghurt culture (YC-X11 Yo-Flex) was added at a level of 0.015% (w/w)
and the solution was stirred on a magnetic stirrer to dissolve it. Subsequently,
the solutions were poured into the containers (3 × 40 ml) and placed in
a thermostatic cabinet, where were first heated for 5 hours at 45°C, and
then cooled to a temperature of 5°C. pH was measured before inoculation and
after fermentation using pH meter CP-401 (Elmetron Sp. J., Zabrze, Poland).
Texture analysis
The texture analyses were performed by two sequential penetration events at
the crosshead speed 1 mm/s (immersion probe in the test sample 15 mm), separated
by a relaxation phase of 30 s using a TA-XT2i texture analyser (Stable Microsystems,
Goalding, UK) equipped with cylindrical probe (1 cm diameter). The results were
analyzed on the computer, giving the results of hardness, adhesiveness and cohesiveness
[10].
Rheometry
Rheological measurements were made using a rheometer RS 300
(Haake, Karlsruhe, Germany) in coaxial plate – plate system. All the tests were performed
at 20°C, which was provided by circulating water bath Haake DC30 (Haake,
Karlsruhe, Germany). Results were recorded using a computer program RheoWin Pro
2.91 (Haake, Karlsruhe, Germany). Apparent viscosity was measured at 10 (s -1)
for 120 seconds. For the analytical purposes, average value was calculated from
90th, 105th and 120th second of the measurement [10].
Statistical analysis
The rheological and textural measurements were completed in three independent
trials. Each analysis was performed in duplicate. The value of the standard deviation,
and the significance of differences between the results was determined using
test the Student-Newman-Keuls by using SAS Enterprise 3.0.2.4.1.4. (SAS Institute
Inc., USA).
RESULTS AND DISCUSSION
Viscosity
The highest increase of viscosity was observed
in the samples with the addition of 6% saccharose, while the smallest with 4%
saccharose (Fig. 1). In the samples with lower content of inulin, the effect
of saccharose addition was ambiguous. Viscosity of samples with 4% saccharose
was the same as for the sample without saccharose. In other samples, the addition
of sugar caused a decrease of viscosity. Viscosity, from the consumer point of
view, is a very important element characterizing the rheological properties of
yoghurt. Therefore, it is important to maintain the desired viscosity and consistency
of the product, for the entire duration of its shelf life [13]. Glibowski & Bochyńska
[7] showed that increase of viscosity in solutions with whey proteins and inulin
are responsible mainly high concentrations of whey proteins, still higher concentration
of inulin also has the effect in increasing viscosity. The research results (Fig.
1) are ambiguous; the concentration of whey protein in the analyzed samples might
have been too small to have an impact on structure of solution.
|
Fig. 1. The effect of addition of saccharose on viscosity of the yoghurt
mimetics containing 13 and 15% inulin (a–d – means with different
superscript letters for the same inulin concentration are significantly different,
p≤0.05) |
Hardness
Figure 2 shows the results of mimetics hardness.
In case of samples containing 13% inulin, it was found that the hardness of all
the tested samples was similar and ranged between 21,1 to 22,2 g. For samples
with 15% inulin, hardness differences were much larger. The highest hardness
was recorded for yoghurts containing 6% of saccharose and the lowest hardness
was observed in the samples with 4% addition of saccharose. As it was in case
of viscosity, hardness increase was also dependent on the concentration of inulin.
This relationship is confirmed in other studies in which the hardness of inulin
gels, expressed as a force of penetration depend on concentration of inulin [4].
Glibowski and Bochyńska [7] reported higher
hardness of inulin-whey protein gels at higher concentration of inulin (15%)
probably due to interaction inulin-whey proteins.
|
Fig. 2. The effect of addition of
saccharose on hardness of the yoghurt mimetics containing 13 and 15% inulin (a–b – means
with different superscript letters for the same inulin concentration are significantly
different, p≤0.05) |
Adhesiveness
The addition of saccharose increased
the adhesiveness of all samples regardless of the content of inulin. Much greater
adhesiveness revealed mimetics with 15% inulin content (Fig. 3), as compared
to those containing 13% inulin. Adhesiveness of the product also is dependent
on the concentration of inulin. Adhesiveness in the samples with lower content
of inulin remained at a similar level, however, 6% addition of succharose cause
significant (p ≤ 0.05) increase in comparison
to samples without saccharose. Low adhesiveness such as close to zero is characterized
by liquids and in this case of solution is undesirable [6].
|
Fig. 3. The effect of addition of
saccharose on adhesiveness of the yoghurt mimetics containing 13 and 15% inulin
(a–b – means with
different superscript letters for the same inulin concentration are significantly
different, p≤0.05) |
Cohesiveness
The results showed there was no link between the content of inulin and cohesiveness
(Fig. 4). Results of cohesiveness were higher compared to the reference product
(Tab. 1). The addition of saccharose did not cause clear change in cohesiveness
in the samples with 13% inulin content, while a significant increase was observed
in 15% inulin mimetics with the addition of 6% saccharose. Cohesiveness values
are within the range of 0 to 1, where 0 means that the sample after deformation,
does not return to its original shape, and 1 means. that there was a complete
recovery as is the case with the liquid [6].
|
Fig. 4. The effect of addition of saccharose on cohesiveness of the
yoghurt mimetics containing 13 and 15% inulin (a–b – means with different
superscript letters for the same inulin concentration are significantly different,
p≤0.05) |
Table 1. The rheological properties and pH of commercially available yogurts |
pH
pH values of the analyzed samples before fermentation range from 6.20 to 6.30.
After the fermentation mimetics containing 13% inulin and saccharose showed no
significant pH difference. pH remained at a constant level between 4.22 and 4.28.
These values were higher than pH the reference product, without saccharose (pH
= 4.05) (Tab. 1). The pH values of products with 15% inulin depended on the concentration
of saccharose, and ranged from 4.30 to 4.49. There was no effect of inulin on
the final product pH which was confirmed in other studies [13].
|
Fig. 5. The effect of addition of saccharose on ph of the yoghurt mimetics containing
13 and 15% inulin (a–b – means with different superscript letters
for the same inulin concentration are significantly different, p≤0.05) |
For better interpretation and for comparison, of the results, commercial yogurts were analyzed. In the majority, the obtained results did not match with the results of studied mimetics. The only similarity to commercial yoghurts were shown in case of viscosity for the samples with 15% of inulin and 6% of saccharose. pH of mimetics was also at a similar level to a pH of typical yogurt. This confirms the fact that the inulin does not affect the pH of product.
Interactions between whey proteins and inulin are not well understood [7]. It was proven that inulin interacts with whey proteins. All of milk proteins with the exception of alpha-lactalbumin connect to the inulin. Beta-lactoglobulin, which is the most abundant whey protein, is responsible for the gelation of whey protein solutions. The other hand, alpha-lactalbumin assists in this process [9]. In practice, the most comprehensive assessment of the quality can be achieved by texture analysis. It allows the complex characteristics of the product taking into account its mechanical properties and geometry [1]. The rheological properties of yoghurt depend on the quality of the raw material, quantity and kind of structure-forming additives, the fermentation conditions and the mechanical impact on the product [20]. Texture is very important for consumers and producers because heavily affects our eating habits, shapes our preferences and is an indicator of freshness. It is also important in the transport and processing, because it determines the handling of products [16, 17]. Inulin and its beneficial effects on texture of fermented products caused that it is widely used in the dairy industry [13].
CONCLUSION
- There is no clear effect of saccharose on the rheological properties of the tested yoghurt mimetics.
- Structure of samples containing 15% inulin and 6% saccharose resembles a commercial product.
- Yoghurt mimetics with 15% inulin are characterized by higher values for most of the tested rheological and texture features.
- Yoghurt mimetics with 15% content of inulin are firmer than these with 13% inulin.
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Accepted for print: 30.06.2016
Kamil Toczek
Department of Biotechnology, Human Nutrition and Science of Food Commodities, Faculty of Food Science and Biotechnology, University of Life Sciences in Lublin, Poland
8 Skromna Street
20-704 Lublin
Poland
email: kamil.tocz@gmail.com
Paweł Glibowski
Department of Biotechnology, Human Nutrition and Science of Food Commodities, Faculty of Food Science and Biotechnology, University of Life Sciences in Lublin, Poland
8 Skromna Street
20-704 Lublin
Poland
email: pawel.glibowski@up.lublin.pl
Sylwia Tracz
Department of Biotechnology, Human Nutrition and Science of Food Commodities, Faculty of Food Science and Biotechnology, University of Life Sciences in Lublin, Poland
8 Skromna Street
20-704 Lublin
Poland
email: sylwiatracz1609@gmail.com
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