# Physicochemical and Sensory Analysis of Apple Cream Fillings for Use in the Pastry Industry
## 3 Results & Discussion
This is slightly higher than AP2 but lower than AP1, indicating that PD has a less water-attracting surface compared to AP2. The absence of apple cubes in PD means that the surface is primarily composed of powdered ingredients, which may have a more balanced mix of hydrophilic and hydrophobic properties. According to Figure 6a, it seems that the increase in the shear stress leads to a decrease in the viscosity of the three samples. This behavior is typical of a non-Newtonian fluid, where the viscosity is dependent on the shear rate. When comparing AP1 and AP2 with PD, it is obvious that for the same shear rate, the PD sample shows higher viscosity values than the samples containing dried apples, such as AP1 and AP2. The addition of dried apples in cubes reduces the elasticity of the samples and increases the water content, reducing the viscosity of the AP1 and AP2 samples. The increase in viscosity in the apple cream fillings follows the order: AP1 < AP2 < PD. According to Figure 4b, it seems that the increase in the shear rate leads to an increase in the shear stress. The PD sample presents the highest shear stress compared to AP1 and AP2 for the same shear rate values. The experimental data of shear rate and shear stress approached the theoretical values of the equations described in Figure 6c, indicating that the three samples are all pseudoplastic liquids. PD presents the highest percentage of potato starch (28.00%) compared to AP2 (17.50%) and AP1(16.19%). Potato starch is a key thickening agent in apple cream fillings, providing the desired viscosity and creaminess, explaining the highest viscosity of PD and the lowest viscosity of AP1. It forms a gel-like structure when hydrated, which helps stabilize the emulsion and prevent phase separation during storage [8]. Xanthan gum solutions are shear thinning fluids, where the viscosity decreases as the shear rate increases [54]. In the preset study the amount of xanthan gum is 1.30% for PD compared to 0.80% for AP1 and AP2, respectively and all samples present shear thinning behavior with the highest value of viscosity to PD and the lowest values to AP1 and AP2. Moreover, the addition of glucose in the form of sugar (63.00% to PD compared to 40.00% for AP2 and 31.00% for AP1) [55] and the presence of dextrose (6.00% for PD and 3.00% for AP2 and 3.45% for AP1) increases the viscosity of the samples explaining the viscosity order of the present study (AP1 < AP2 < PD). Figure 5: Images with the contact angle measurement of (**a**) AP1, (**b**) AP2, and (**c**) the PD sample. The microbiological analysis of the three samples (AP1, AP2, and PD) was performed according to the microbiological characteristics of the raw materials. The total plate count of the present samples (AP1,AP2, PD) is less than 10,000 cfu/g while the standard plate count of different types of sauce and ketchup varied from 100 to 300 cfu/g [56]. The yeast and mold count among the samples is less than 300 cfu/g for AP1 and AP2 and less than 100 cfu/g for PD, while in other types of sauce and ketchup the count varies between 50-500 CFU/g [56]. Other studies have shown that the total viable bacterial count for different sauce ranges between 10\({}^{2}\) and 10\({}^{8}\) cfu/g, while the total count of fungi ranges from 18 to 6.3 \(\times\) 10\({}^{5}\) cfu/g [57]. In the present study, coliforms are less than 10 MPN/g, while in other studies they were not detected in selected sauce and ketchups [56]. Moreover, the _E. coli_ (total) and _S. aureus_ values are less than 10 cfu/g for AP1 and AP2 and 0 cfu/g for PD. Finally, _Salmonella_ spp. was not detected in 25 g in all samples. According to literature [56], the acceptable limit of total viable count, coliform, yeast, and mold count for sauce and ketchups is \(<\)10\({}^{4}\) CFU/g, \(<\)10 MPN/g, \(<\)10\({}^{4}\) CFU/g, respectively, while the Ireland's guidelines for the microbiological quality of some ready-to-eat foods at point of sale [58] indicate that the satisfactory levels for _E.