Electronic Journal of Polish Agricultural Universities (EJPAU) founded by all Polish Agriculture Universities presents original papers and review articles relevant to all aspects of agricultural sciences. It is target for persons working both in science and industry,regulatory agencies or teaching in agricultural sector. Covered by IFIS Publishing (Food Science and Technology Abstracts), ELSEVIER Science - Food Science and Technology Program, CAS USA (Chemical Abstracts), CABI Publishing UK and ALPSP (Association of Learned and Professional Society Publisher - full membership). Presented in the Master List of Thomson ISI.
2016
Volume 19
Issue 3
Topic:
Food Science and Technology
ELECTRONIC
JOURNAL OF
POLISH
AGRICULTURAL
UNIVERSITIES
Toczek K. , Glibowski P. , Tracz S. 2016. EFFECT OF SACCHAROSE ON RHEOLOGICAL AND TEXTURAL PROPERTIES OF YOGHURT MIMETICS BASED ON INULIN AND WHEY PROTEIN, EJPAU 19(3), #01.
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

 

ABSTRACT

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
Tested feature
Plain yoghurt 1
Plain yoghurt 2
pH
4.13
4.25
Viscosity [Pa × s]
2.967
1.206
Hardness [g]
17.806
2.125
Adhesiveness [N × s]
-58.286
-1.413
Cohesiveness
0.508
0.732

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

  1. There is no clear effect of saccharose on the rheological properties of the tested yoghurt mimetics.
  2. Structure of samples containing 15% inulin and 6% saccharose resembles a commercial product.
  3. Yoghurt mimetics with 15% inulin are characterized by higher values for most of the tested rheological and texture features.
  4. 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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