## 3 Results
### The Effect of Storage Method on Homemade Tofu Quality
#### 3.2.3 Microbiological Quality  
Tofu cheeses, due to their high water and protein content, are susceptible to microbial growth, especially if proper manufacturing and/or storage procedures are not performed [16; 46]. Due to this fact, homemade tofu was subjected to microbial analysis after six months of storage in vacuum packs in the freezer. Figure 8: Percentage changes in the (**a**) physicochemical parameters (moisture, pH, and free acidity), (**b**) antioxidant activity (DPPH and FRAP), total polyphenols content (TPC), and (**c**) texture parameters after six months of storage of vacuum-sealed tofu in freezer in relation to the values of fresh samples. C—commercial; N—natural; WG—wild garlic; BC—black cumin; B—basil; PC—Herbes de Provence and cranberry. Total mesophilic bacteria in analyzed samples ranged from 4.39 to 7.78 log CFU/g. It must be noted that the lowest values were obtained for commercial natural tofu and self-prepared natural tofu, as well as for tofu with black cumin (Table 4). According to the Soyfoods Association of America's Tofu Standards Committee [47], the acceptable microbiological contamination in tofu should not exceed 6.7 log CFU/g. Considering that four of the seven tested samples were at an acceptable level. However, the European Commission established the general standard limit of total mesophilic bacteria in food products as lower than 5.47 log CFU/g [48], which allowed us to accept only C and BC samples. In this aspect, the literature data are very diversified. [PERSON] et al. [16] observed that the total mesophilic bacteria was between 4 and 5 log CFU/g of fresh tofu samples. [PERSON] and [PERSON] [15], who analyzed the microbial quality of commercial tofu present in the Polish market, observed the lowest microbial contamination for natural tofu (2.83 log CFU/g) in natural tofu and higher for marinated and smoked tofu (up to 5.47 log CFU/g). On the other hand, some authors highlighted the poor hygienic quality of commercial tofu with aerobic plate counts above 10\({}^{6}\) CFU/g (which is similar to some of our samples) [49; 50; 51]. The level of yeast ranged from 1.21 to 2.68 log CFU/g, and only two samples exceeded the norms of <2 log CFU/g of the European Commission [48]. [PERSON] [50] determined the yeast value at the comparable level of 5.5 \(\times\) 10\({}^{2}\) CFU/g. Molds were not detected in any sample. Importantly, _E. coli_, _Salmonella_, and _Clostridium perfringens_ bacteria were not detected in any samples. According to the Soyfoods Association of America's Tofu Standards Committee, _Salmonella_ and _E. coli_ should not be present in tofu [47]. The Enterobacteriaceaeae were not detected in two samples of natural tofu and the sample with wild garlic, while only in two samples was the level higher than that established by the European Commission limit of <2 log CFU/g [48]. The number of coagul-positive staphylococci ranged from 0 to 3.54 log CFU/mL. According to the Department of Health [52], the permissible limit of 10\({}^{3}\) CFU/g has been exceeded only for two samples. The literature data indicate various degrees of contamination of tofu samples with even pathogenic bacteria. [PERSON] et al. [46] and [PERSON] et al. [53] detected higher levels of _S. aureus_ in industrial tofu samples (more than 10\({}^{4}\) CFU/g), while [PERSON] and [PERSON] [15] and [PERSON] [43] obtained the levels of 0 to 4.35 log CFU/g. [PERSON] and [PERSON] [49] observed _Enterobacteriaceae_ above 10\({}^{3}\) CFU/g for most of the analyzed samples, similar to [PERSON] et al. [16]. Moreover, [PERSON] and [PERSON] [49] detected _E. coli_ at the level of 10\({}^{2}\) CFU/g in most of the samples. To summarize, long storage in the frozen form of homemade tofu can be a good method for the prolonged shelf life of this food, which was confirmed by the good microbial quality of natural tofu samples. It can be assumed that the addition of antioxidant ingredients of herbal origin helps maintain nutritional values and protects nutrients against oxidation and chemical degradation.