## 2 Materials and Methods  
### Samples  
The raw material used for grinding consisted of meat-and-bone residues obtained from broiler chickens of the Ross 308 cross, aged 40-50 days, which were taken from the commercial poultry company LLP \"Ardager\", Semey, Kazakhstan. Following manual deboning of the carcass, the remaining bones--including vertebrae, breast, drumstick, and thigh bones--typically retained up to 8% adherent muscle tissue. The chemical composition of the poultry bone fraction was as follows: moisture content 65.6%, protein 16.8%, fat 12.1%, and ash 5.5%. Chicken carcass with a total mass of 50 kg were initially subjected to deboning and sinew removal, with all bones carefully separated. The recovered bones were first coarsely ground using a power crusher. The resulting bone material was then divided into four equal portions, each weighing 6 kg. Each portion was processed separately in a colloid mill. First, the control knife assembly was installed, and each batch was milled at a different rotor speed. Afterward, the experimental knife assembly was installed, and the remainingbatches were similarly milled at the same set of rotational speeds. This procedure allowed a systematic comparison of grinding effectiveness between the control and experimental rotor-stator geometries under identical processing conditions. Grinding was performed at four different rotor speeds: 1000 rpm, 2000 rpm, 3000 rpm, and 4000 rpm. The variation in rotational speed was achieved by using an electric motor equipped with a frequency converter. Two types of rotor-stator knife assemblies were used in the study. The control assembly represented a factory-standard configuration with a tooth inclination angle of 45\({}^{\circ}\) and a tooth pitch of up to 1.5 mm. The control tool configuration was selected because it is a widely used industry standard in commercial colloid mills intended for grinding relatively soft food materials such as nuts and other non-fibrous or less resistant raw ingredients. While this geometry is effective for the fine grinding of softer products, it is not optimized for hard inclusions such as bone, because hard particles with sizes of more than 0.1 mm are not acceptable in food systems. The experimental assembly was designed with a modified tooth geometry, featuring a 20\({}^{\circ}\) inclination angle and a reduced tooth pitch of up to 1 mm. _Description of Fine Grinding Equipment_  
A general view of the grinder is shown in Figure 1. The device operates according to the principles of centrifugal grinders. The throughput capacity of the machine is 80 kg/h (Table 1). The structure of the grinder includes a supporting frame, a loading hopper, a working assembly (rotor-stator), and a discharge chamber. Figure 1b provides a detailed depiction of the individual components and assemblies of the grinder. \begin{table}
\begin{tabular}{l l} \hline
**Indicator** & **Characteristic** \\ \hline Capacity, kg/h & 80 \\ \hline Electric power, kW & 4 \\ \hline Overall dimensions, cm & 64 \(\times\) 41 \(\times\) 90 \\ \hline Weight, kg & 150 \\ \hline Hopper volume & 8 L \\ \hline \end{tabular}
\end{table} 
Table 1: Technical characteristics of colloid mill. Figure 1: Colloid mill. Determination of mass and volume flow rates  
The mass flow rate is determined by the following formula:  
\[M=\frac{m}{t}\cdot 3600\]  
where \(M\)--mass flow rate, kg/h,  
\(m\)--mass of loaded raw material,  
\(t\)--grinding time, s.  
The volumetric flow rate is determined by the following formula:  
\[V=\frac{V_{s}}{t}\cdot 3600\]  
where \(V\)--volume flow rate, m\({}^{3}\)/h,  
\(V_{s}\)--volume of loaded raw material,  
\(t\)--grinding time, s.  
Determination of particle size distribution of bone particles  
The dried solid residue after alkaline treatment was passed through a set of laboratory sieves with nominal mesh diameters of 2 mm, 1 mm, 0.5 mm, and 0.1 mm. In emulsified meat products, a particle size below 0.1 mm is generally considered acceptable, as larger bone fragments negatively impact texture and sensory quality.