Rheological behaviour of chocolate at different temperatures

The rheological behaviour of the chocolate at different temperatures was studied using a concentric cylinder viscometer with precision small samples adapter, temperature sensor and standard spindle. BIO chocolate (100% organic cocoa) has been used for the whole types of experiments. At the first, the range of temperature has been chosen 36 oC, 38 oC, 40 oC, 42 oC, and 44 oC. The shear deformation rate was established from the 0.1 s-1 up to 68 s-1. Rheological behaviour was non-Newtonian (plastic) with inconsiderable yield stress in all temperatures. The chocolate unambiguously demonstrated plastic behaviour and flow curves were fitted by the power law model (Herschel-Bulkley model), Bingham model, and Casson model with taking into account the coefficient of determination R2. The obtained results of rheological behaviour of chocolate can be best described as Casson fluid. Exactly coefficients of models can be used for modelling of flow velocity, volume flow, friction factor, Reynolds number, two dimensional and three dimensional velocity profiles and much more for flow in the real technical elements e.g. pipes, trough, tubes. Finally, temperature dependence of apparent viscosity of chocolate was also continuously measured in the range from 35 oC up to 62 oC. The apparent viscosity decreased in the temperature range. This decrease was fitted using power law equation. The knowledge of the plastic flow behaviour of chocolate is very important, because it is not quite common flow behaviour of foodstuffs.O

Effect of additives to microbiological quality of yogurts

The objective of this work was to study the effect of addition chia flour, quinoa flour, nopal powder, apple fibre and bamboo fibre BAF 40 in yogurt to microbiological quality. Yogurts were made with 1, 3 and 5% of addition of these additives. The milk used for manufacturing was heated up to 85oC for 5 min and flour, powder and fiber were irradiated for 20 min in three replicates. It was monitored: Lactic acid bacteria (LAB) - 72 hours at 30oC (ISO 13721:1998) and yeasts and moulds - 5 days at 25oC (ISO 21527-1:2009). During storage, the number of LAB was increased to match the initial concentration of yogurt with addition chia flour (concentration 1, 3, 5%) and quinoa flour (1%). The addition of nopal powder, apple or bamboo fiber to yogurt showed a tendency to decrease the number of LAB compared with its initial concentration. All samples were compared with the control yogurt without addition whatever flour, powder or fiber. The amount of yeasts and moulds was increased with the increasing addition of fiber in yogurts. The lowest amount of yeasts and moulds was in yogurt with the bamboo fiber. On the other hand the highest amount was in yogurt with chia flour.O

Effect of different storage times on Japanese quail egg quality characteristics

The aim of this research was to monitor selected quality parameters of Japanese quails (Coturnix coturnix japonica) - the loss of egg weight, changing yolk and white index, Haugh units, egg yolks color. Quail eggs were stored for 0, 1, 2, 4, 6 and 8 weeks at 4 oC. The weight of the quail eggs ranged from 11.67 to 12.27 g. The ratio of the shell range 7.60 to 8.16 % (resp. 0.89 - 0.96 g), ratio of egg white from 59.33 to 62.10 % (resp. 6.31 - 6.66 g) and a ratio yolk of 30.13 - 32.88 % (resp. 3.68 - 3.91 g). The lost of egg weight ranged from 0.47 to 2.93 % during the quail eggs storage, corresponding to a weight loss of 0.26 - 0.58 g of the total weight of the eggs. The average values of the yolk index ranged from 42.67 - 48.53 % and the average values of the quail egg white index ranged from 6.77 to 11.35 %. The average Haugh units were set between 56.93 and 73.72. The color of quail egg yolk was determined using the La Roche scale with the most frequent value 3. During the quail eggs storage, a statistically significant difference was found with most of the quality traits observed.O

Phthalic acid esters content in yoghurt with chia flour and bamboo fiber during storage time

Phthalic acid esters are plasticizers, they can migrate freely from plastic to their surroundings. They have negative health effects. European legislation sets specific migration limits for phthalic acid esters. In our study, we deal with two esters of phthalic acid, dibutylphtalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP). It was studied the effect of storage of four types of yoghurt on the concentration of phthalic acid esters. Yoghurts contained 1% chia flour, 5% chia flour, 1% bamboo fiber and 5% bamboo fiber. Yoghurts were stored in plastic cups, which contained both examined phthalic acid esters. Esters of phthalic acid were determined after 1 week of storage then after 2 weeks of storage and in the original raw material. Furthermore, the pH of the yoghurt was determined. The pH values ​​were correlated with phthalate concentrations: the correlation coefficient for DBP with a pH of -0.0265 and for DEHP with a pH of 0.3075. Mean concentrations of DEHP decreased over time, while DBP decreased for yoghurt with 1% chia flour, while in other cases they increased. The mean DBP concentrations in yoghurt were higher than the average concentrations of DEHP. Comparing the mean sample values ​​with t-test for dependent samples for yoghurt of the same type, when comparing the DBP or DEHP concentration in week 1 with the DBP or DEHP concentration at week 2, the mean values ​​were consistent. It can be noted that there was no increase in DEHP concentrations from cups to yoghurts, which was probably due to a lower concentration in cups than the DBP concentration. DBP concentrations increased in 3 of the 4 types of yoghurt. The determined pH in yoghurts did not differ significantly. Apparently a greater effect on the migration of phthalic acid esters will have in our case a different yoghurt consistency than pH. It would be appropriate to examine the effect of food density on the migration of phthalic acid esters. Likewise, it would be appropriate to examine the effect of pH but in the same food with different pH on the migration of phthalic acid esters.&nbsp;</p

Vliv vybraných faktorů skladování na jakostní parametry křepelčích vajec

This thesis dealt with the monitoring of selected quality parameters of quail eggs (the lost of egg weight, index, egg-shaped, the percentage of yolk, albumen and shell of the total weight of quail eggs, changing the height yolk and white index, Haugh Units, colour egg yolks and pH yolk, albumen and egg melange) stored for 0, 1, 2, 4, 6 and 8 weeks at the temperature of 4°C. In total 120 samples Japanese quail (Coturnix coturnix japonica) eggs were analysed. The lost of mail eggs during storage range 0,47 - 2,93% which corresponding with weight loss of 0,26 to 0,58 g. The average value of the ratio albumen quail eggs ranged 43,60 - 48,53 %. The percentage of yolk increased from 31,79% to 32,88 %. The average value of the index whites ranged from 6,77 to 11,35 %. The percentage of egg white during storing first rose from 9,37 % to 11,35 %, and there after decreased to a value of 6,77 %. Average values Haugh Units ranged from 56,93 to 73,72. The colour of yolk quail eggs was determined the most frequent value 3. During storage for most of the quality parameters found a statistically significant difference

Kvalitativní parametry vajec křepelek japonských

Qualitative parameters of Japanese quail eggs are associated with the quality and individual eggshells and egg components. Eggs as one of the nutritionally most important foods are characterized by qualitative parameters that evaluate their food safety and freshness. These properties are divided into external and internal. Among the external features of eggs belongs egg weight, egg shape index, shell color, pollution shells, shell wholeness, strength and thickness of the shell, the smell of eggs and its structure. The internal properties are focused on the individual components separately, which means that these tests are different for yolk and albumen and they are ranked among the main indicators of quality of eggs. These include density, freezing point, the weight of egg albumen, egg yolk and shell, yolk index, albumen index, Haugh units, yolk color, albumen and yolk pH. The quality of the eggs is also affected by many factors, such as age of hens, composition of the diet, the effects of genotype and health status

Relationship between viscosity and sugar content of must during ripening period of grapes

The relationship between dynamic viscosity and sugar content of the must is important indicator during the ripening of the vine grapes. For the experiment were selected and used only grape vine varieties. The grape vine varieties are divided into blue and white. The varieties of Blaufr&auml;nkisch, Blauer Portugieser, and Cabernet Moravia were used in the blue varieties. Representatives of the white varieties were used Pinot Blanc, Pinot Gris, and Sauvignon. Country of origin was the Czech Republic, wine region Moravia (sub-region Slov&aacute;cko). The grapes were collected and analyzed four times week after week during their ripening period. After grapes harvesting the individual berries were cut out of grape using the scalpel. These berries were then weighed and then the must was squeezed using a mechanical presser. Weight of berries, dynamic viscosity (in shear strain rate 100 s-1), sugar content, and density of must were measured and evaluated. From the values of berries weight it can be observed the variations in weight depending especially on the weather change - the water content in the berries. The observed sugar content did not change a lot during maturity, which can be explained by a more mature phase of the grapes. The results of viscosity and sugar content (for all varieties) demonstrate the viscosity dependence on the sugar content of must - with increasing viscosity of the must the sugar content of the must increase and conversely. The knowledge of the physico-mechanical properties os wine must is very important for for technocologists, producers, but also wine consumers.</p

Rheological and Flow Behaviour of Yolk, Albumen and Liquid Whole Egg from Eggs of Six Different Poultry Species

Liquid egg products are one of the basic raw materials for the food industry. Knowledge of their rheological and flow behaviour in real technical elements is absolutely necessary for the selection of suitable technological equipment for their processing. In this article, the rheological properties of liquid egg products were determined. Eggs from six different species of poultry are used: domestic hen (Gallus gallus domesticus) hybrid Hisex Brown; Japanese quail (Coturnix japonica); German carrier goose (Anser anser f. domestica); domestic ducks (Anas platyrhynchos f. domestica); domestic guinea fowl (Numida meleagris f. domestica); and domestic turkeys (Meleagris gallopavo f. domestica). Liquid egg products showed pseudoplastic behaviour in range of shear strain rates from 0.2 up to 200 s&minus;1 and at the temperature of 18 &deg;C. Thus, the flow curves were constructed using the Ostwald-de Waele rheological model, with respect to the pseudoplastic behaviour of liquid egg products. According to the values of the coefficients of determination (R2), the sum of squared estimate of errors (SSE) and the root mean square error (RMSE), this model was appropriately chosen. Using the consistency coefficient K, the flow index n and the adjusted equations for the flow rate of technical and biological fluids in standard pipelines, the 3D velocity profiles of liquid egg products were successfully modelled. The values of the Reynolds number of the individual liquid egg products were calculated, and the type of flow was also determined. A turbulent flow has been detected for some liquid egg products