# Effect of Extraction Method and Thermosonication on Apple Juice Quality
## 3 Results and Discussion
### Influence of Device Type on Total Mesophilic Microorganism Content in Apple Juice  
Results of testing of juices concerning the influence of device type and time and temperature of storage are presented in Tables 1 and 2. Mean total microorganisms in the studied juices directly after production was low and ranged between \(4\times 101\) and \(4\times 102\) colony forming units (cfu)/mL. As demonstrated by research, the microbial content in fresh juice is variable and depends on the raw material state and production conditions. Results of the study conducted by [PERSON] et al. [38], carried out in several tens of samples, demonstrated that the total microorganism count in juice ranged between 3.65 and 9.31 \(\times\) 102 cfu/mL. On the other hand, [PERSON] et al. [39] determined that the total microorganism content in one-day carrot juice was from 3.1 \(\times\) 105 to 9.1 \(\times\) 105 cfu/mL. The low microbial content found in our study is primarily associated with the experimental conditions, i.e., the fruits were carefully cleaned and the devices were disinfected. Thus far, no permissible level of microorganisms has been established for minimally processed products [40]. The applicable microbiological criterion determining the number of mesophilic microorganisms to be 103-104 cfu/mL only concerns pasteurized juices [41].  
Under experimental conditions, the lowest total microorganism content directly after extraction was recorded in the case of juice obtained using a piston press. Juice from the double-screw press was characterized by close to twofold higher total microorganism count. A very high, 10-fold higher total microorganism count as compared with the piston press was found for juice obtained using the decanter. A visual assessment of juice from the decanter indicated high pulp and skin content. It is possible that microorganisms inhabiting the surface of the skin were introduced with it to the juice, and the solids formed a medium for bacterial growth.  
During juice storage, a significant increase of total mesophilic microorganism count occurred in all tested samples, and a clearly less pronounced increase was observed in samples stored in refrigeration conditions (Tables 1 and 2). In the case of juice obtained with the use of the piston press and stored at 4 \({}^{\circ}\)C, a close to three-fold increase of total mesophilic microorganism count was observed after 96 hours (4 days), but the number was over three-fold lower than in juice obtained with the use of the decanter. After 120 hours (5 days), the total microorganism count in juice obtained using the basket, double-screw press, and decanter was nonquantifiable (nqf). In the case of juice stored at 20 \({}^{\circ}\)C after 72 hours (3 days), independent of the production method, a rapid decrease in quality was recorded associated with increased total microbial count, and the samples were characterized by nonquantifiable colony forming units or demonstrated spilled structure. The slowest growth of total mesophilic microbial count independent of storage conditions was observed in the case of juice from the piston press. Therefore, this juice underwent further detailed testing. As demonstrated by the experiments (Table 1), juice produced in accordance with our procedure should not be stored in refrigeration conditions for more than 96 hours (4 days).  
Figure 2: Influence of sonication time on temperature of apple juice. Error bars represent standard deviations.