3 experimental part

Structural and mechanical properties of soft cheese

In order to optimise process control in product manufacturing, it is of paramount importance to study the formation of protein structures.
Thermodynamic parameters such as dispersibility, strength properties are the most important characteristics of the state of milk systems. Any changes in these have a significant effect on the finished product processes.
An analysis of the literature suggests that the curdling process and the raw milk affect the strength of the milk clot, the clot is characterised by a more elastic and softer structure, separating the whey.
In the production of soft cheeses from a mixture of cow's and goat's milk produced by curdling, the clot strength and the syneresis process are decisive for the quality of the finished product. In the studies presented here clot strength was determined by changing the dispersibility of the protein particles in the clot. For this purpose, clot samples with different ratios of cow's and goat's milk were mechanically processed and then the specific surface area of the particles was determined by the degree of dye absorption.
In order to study the ratio of raw milk to clot formation, test samples were produced with different ratios of cow's and goat's milk. The control was a sample made from cow's milk.
While studying the quality of clot obtained from goat's milk, it was found that goat's milk, compared to cow's milk, forms a fragile clot with a high loss of milk components into the serum. It is noted that with increasing dosage of cow's milk in the mixture, clot density increases and with the ratio of goat's milk to cow's milk 50/50; it is close to the clot obtained from cow's milk.
The table shows the 29results of studies on the dispersibility of protein particles in a cheese clot in terms of the amount of dye adsorbed at different raw milk ratios.
Table29 - Amount of dye from raw milk ratio

Soft cheese	Amount of dye adsorbed, %
from cow's milk	63,48±3,87
made from goat's milk	79,56±2,36
from a 1:1 milk mixture	70,71±3,57

The higher the amount of adsorbed substance, the higher the degree of particle dispersion and therefore the lower the strength of the clot.

It can be observed from studies that the greater the amount of goat's milk in the clot, the more it adsorbs the colouring agent, and hence the clot is characterised by less strength. A clot made from goat's milk has less cohesion and is more delicate and less strong than a clot with a predominance of cow's milk.
The structural and mechanical properties of the soft cheese samples were determined using a penetrometer. The soft cheeses are qualified in accordance with Table 30.
Table30 - Classification of Soft Cheese Texture (by P.A. Rehbinder)

Shear stress θ-10^-2 Pa	Texture assessment
50	Very soft, almost flowing
50-100	Very soft, but not smudgeable
100-200	Soft, spreadable
200-800	Plastic, spreadable
800-1000	Solid, without the ability to smear
1000-1500	Too hard with limited ability to smearing
1500	Too hard

In the course of the research, shear stress values were determined in samples of soft cheese made from goat milk, from cow's milk, from a mixture of cow's and goat's milk, and from a sample with chickpea flour. The experimental data are shown in the table below 31.

Table 31 - Soft cheese sample figures

A sample of soft cheese	Mass fraction of moisture in cheese, %	Mass fraction of solids in serum, %	Ultimate shear stress, θ-10^-2, Pa
from cow's milk	56,3±0,41	7,6±0,5	786±29
made from goat's milk	59,5±0,63	8,1±0,4	668±37
from a mixture of cow and goat's milk 1:1	58,4±0,57	8,9±0,4	721±35
from a mixture of milk and flour chickpea	61,2±0,61	10,1±0,6	534±26

During the experiment, a partial waste of dry matter was observed in the whey during clot processing. It was also found that the addition of the vegetable ingredient resulted in a softer, more pliable

the consistency of the finished product. All samples of soft cheeses can be classified as products with a pliable, spreadable texture.

3.