The group of semi-hard cheeses is quite heterogenous and there are distinctions between individual representatives of this group. The aim of this paper was a comparison the colour changes and texture properties of semi-hard pasta filata cheeses during ripening. Spectrophotometer Konica Minolta CM-3500d was used for the colour measurements of cheese samples. Color parameters L* a* b* were determined for the edge part and for the middle part of samples. The texture properties of cheese were measured by TIRATEST 27025. Measurements were made for part following the edge and the middle part of samples as well. During ripening of cheese samples there were observed statistically significant changes in the colour parameters of the edge part of oiled cheese. Total colour difference (ΔE * ab ) during storage was the most noticeable in first 10 days of ripening. In compare with changes in a* parameter of the edge part of cheese samples, red tone (a* parameter) in the middle part of cheese samples did not show so large change. The measured strenght of edge part of the cheese samples was in range between from 7.44 N up to 23.49 N. Firmness of middle part varied from 4.46 N to 24.40 N in 60 days of maturating.
Differences in the rheology and friction factor of natural food hydrocolloid gels were studied in this paper. The practical importance of the knowledge of the rheological parameters is quite evident. The experimental data were carried out using a concentric cylinder rotary viscometer. It was prepared 1% hydrocolloid solutions (hydrogels). Hydrogels of the natural gums extracted from the seeds of the plants and plant tubers have been usedcarob gum (from the seeds of Ceratonia siliqua), guar gum (from the seeds of Cyamopsis tetragonoloba) and tara gum (from the seeds of Caesalpinia spinosa). Rheological behaviour has non-Newtonian pseudoplastic character and the flow curves were fitted using the Otswaldde Waele (power law) model and Herschel -Bulkley model. The hydrogels exhibit shear thinning behaviour. The meaning of the rheological parameters on the friction factors during flow of hydrocolloid gels in the tube has been shown. Information on time dependent behaviour of tested liquids has been also obtained. Time dependent curves were fitted by the Gaussian model. Preliminary results obtained for a constant shear rate showed the thixotropic and time-dependent behaviour of the hydrogels. These parameters can be especially used in much software dealing with a numerical simulation of the flow problems.
The aim of this work was measurement of the curd firmness prepared by different volume of rennet solution and comparison of differences of curd firmness between these volumes. Further, it was observed the influence of different volumes of rennet up to thevolume of whey release, curd firmness, dry matter of curd and dry matter of whey. The composition of milk was determined according ISO and Czech state standard. Dry matter content (%) was determined by gravimetry, in drying oven at 102 °C to constant weight (ISO 6731:2010), the protein content (%) by Kjeldahl´s method (EN ISO 8968-1:2002), content of fat (%) by Gerber´s acidobutyrometric method (ISO 2446(ISO :2008, content of lactose by polarimetry, titratable acidity by titration Soxhlet-Henkel method, pH and calcium content in milk (g.L -1 ) was determined by complexometric titration with flueroxone as an indicator according to Czech state standart No 57 0530. For coagulation was used microbial rennet CHY-MAX R M 200. There were measured: curd firmness, rennet coagulation time, curd quality, volume of released whey, weight of curd, dry matter of curd and dry matter of whey. Different volumes of rennet solution had influence on curd firmness. Curd firmness (volume of rennet solution) had no significant influence on curd quality (five grade scale). Curd firmness had influence on volume of whey release (mL) out of the curd. With the increasing curd firmness s increased the volume of whey released from the curd. The volume of rennet solution had an influence on weight of curd. Curd dry matter raised with higher volume of rennet solution. Volume of added rennet solution had no statistically significant effect on the change of whey dry matter.
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