# Evaluation of Hazelnut Cake Flour for Use as a Milk Powder Replacer in Ice Cream
## 3 Results and Discussion
### Rheological Properties of Ice cream Mixtures  
Although there is no optimum value for the viscosity of ice cream mixtures, it is an important property [1] so considerable attention should be given to parameters influencing ice cream mixture viscosity. For example, it is important for industrial designing [53; 54], and it affects other ice cream properties, such as overrun values [55] and hardness [56]. In general, the rheological properties of ice cream are influenced by protein, fat, MSNF, and dry matter content, as well as by the concentration of added stabilizers and emulsifiers [57; 58] and by the ageing duration [59]. The rheological properties of ice cream samples from this research are presented in Table 3 and Figure 2. According to the R\({}^{2}\) values (0.997-1.000), it is obvious that the Ostwald de Waele model was successfully fitted to describe the flow behaviour of analyzed ice cream mixtures. Values for the flow behaviour index in this research were in the range of 0.551 to 0.728, i.e., less than one, which is consistent with previous statements that ice creams are shear-thinning non-Newtonian fluids with pseudoplastic flow [1; 36; 48; 60]. In addition, the pseudoplastic behaviour of analysed ice cream mixtures can be noticed from Figure 2a. The results show that the substitution of SMP with HPCF increased the consistency coefficients (from 1.32 to 7.66 Pa s\({}^{\text{n}}\)), and this increase was significant (\(p<0.05\)) for all samples, except for the HN1. These findings align with those obtained by [PERSON] et al. [22] who incorporated a beverage made from hazelnut cake in yoghurt. Furthermore, [PERSON] et al. [61] investigated the possibility of cold-pressed chia seed cake application as a fat replacer and stabiliser in ice cream. They reported that this by-product can be used as an agent for improving the ice cream's rheological properties in low-fat ice cream. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **Consistency Coefficient** & **Flow Behaviour Index** & **Macroviscosity** & **Thixotropic Area** \\  & **K (Pa s\({}^{\text{n}}\))** & **n (\(-\))** & **n\({}_{\text{50}}\) (Pa s)** & **A\({}_{\text{t}}\) (Pa/s)** \\ \hline C & 1.32 \(\pm\) 0.03 d & 0.681 b & 0.999 & 0.38 \(\pm\) 0.00 d & 1682.00 \(\pm\) 4.90 e \\ HN1 & 1.17 \(\pm\) 0.04 d & 0.728 a & 1.000 & 0.27 \(\pm\) 0.00 d & 2054.00 \(\pm\) 50.62 d \\ HN2 & 4.76 \(\pm\) 0.08 c & 0.581 c & 0.999 & 0.50 \(\pm\) 0.00 c & 5334.00 \(\pm\) 93.90 c \\ HN3 & 5.78 \(\pm\) 0.04 b & 0.580 c & 0.997 & 0.61 \(\pm\) 0.00 b & 7345.00 \(\pm\) 56.34 b \\ HN4 & 7.66 \(\pm\) 0.07 a & 0.551 d & 0.998 & 0.69 \(\pm\) 0.00 a & 9839.50 \(\pm\) 48.58 a \\ \hline \hline \end{tabular}  
* The results are expressed as mean \(\pm\) SD. Means in the same column with different superscripts are significantly different according to the Tukey HSD test (\(p<0.05\)). C—control ice cream; HN1, HN2, HN3, HN4—samples with 25%, 50%, 75%, and 100% replacements of SMP with HPCF.  
\end{table} 
Table 3: Rheological properties of ice cream mixtures. Figure 2: Rheology properties of ice cream mixtures: (**a**) apparent viscosity (Pa s) and (**b**) flow curves-shear stress (Pa) at various shear rates (1/s). C—control ice cream; HN1, HN2, HN3, HN4—samples with 25%, 50%, 75%, and 100% replacements of SMP with HPCF. An increase in the sample viscosity in this research may be explained by the water-binding properties of the proteins from hazelnuts [22; 23]. According to [PERSON] and [PERSON] [62], different protein sources may impact the consistency coefficient of ice cream mixtures, due to their unique characteristics. [PERSON] et al. [63] reported that adding a pea protein isolate instead of milk powder increases viscosity due to the protein's high water-binding properties and thus more stable gel matrix formation. In addition, several studies reported that dietary fibres contribute to enhanced viscosity because of their water-holding capacity [36; 42; 64].