## 4 Discussion
However, during storage, the colony counts of the groups detected usually increased, but as there are no limits for these groups, it is difficult to assess their microbiological status in terms of shelf life. The technological and hygiene criterion of Regulation (EC) No. 2073/2005 [57] pertains solely to the determination of the number of _E. coli_ in chopped or cut fruit and vegetables, allowing between 100 and 1000 per 1 g sample. Nevertheless, Decree 4/1998 of the Hungarian Ministry of Health [58] also establishes a threshold for the number of moulds, specifying a range between three and four orders of magnitude. Moulds were very rare in our samples, and anaerobic storage reduced their numbers below the detection limit, with yeasts becoming the dominant fungi. In the case of sweet potato samples, the data obtained during microbiological tests were found to be significantly heterogeneous. This discrepancy may be attributable to the fact that, in the case of the three parallel samples, one of the tested sweet potato cubes exhibited a significantly lower microbial count than the other two. As demonstrated in Figure 2, the sample's standard deviation exhibited a range of up to three orders of magnitude, as evidenced by the data from Covington for anaerobic bacteria counts and lactic acid bacteria. It has been demonstrated that significant deviations may be attributable to a number of factors, including, but not limited to, the heterogeneous distribution of microbes, sampling or dilution errors, plating or colony-counting errors, contamination, or even real variability in microbial load [59; 60; 61; 62]. In the case of the Covington (dark-orange- fleshed sweet potato) variety, the treatments resulted in a reduction in lactic acid bacteria during storage, leading to a slight increase in pH values when treated with apple pomace and chokeberry pomace extracts. It has also been demonstrated that this variety underwent a decline in LAB following treatment with ascorbic acid and citric acid. However, a decrease in pH values was observed in response to the application of the organic acids. In the case of the Bonita (white- fleshed sweet potato) variety, it was also observed that the treatments reduced the lactic acid bacteria, but not to the same extent, resulting in minimal changes in pH values. Consequently, the findings of the treatment studies indicate that citric acid treatment is the most efficacious procedure; thus, we recommend its utilisation to maintain microbiological stability and extend the shelf life of sweet potato varieties. However, for the Bonita (white) variety, a combination of citric acid and ascorbic acid would be advantageous in order to achieve a more effective impact. The phenomenon that organic acids have a stronger antimicrobial effect than fruit pomace extracts can be attributed to different factors. Organic acids (e.g., acetic, lactic, citric, or malic acid) are typically in a pure or highly concentrated state, thereby ensuring consistent and potent antimicrobial activity. Conversely, fruit pomace extracts comprise a multifaceted array of compounds, including fibres, flavonoids, polyphenols, and sugars, as well as negligible quantities of organic acids [63; 64]. Consequently, the concentration of active antimicrobial substances is considerably lower and more variable. The mechanism of action of organic acids involves the disruption of microbial cell membranes and the reduction in the pH level. Organic acids are capable of penetrating cells in an undissociated state, thereby acidifying the cytoplasm [65; 66]. These mechanisms have been shown to be direct and efficient. However, it is important to note that pomace extracts may rely more on flavonoids and phenolic acids, which have weaker and often species-specific antimicrobial activity [67]. These compounds usually act via extracellular enzyme inhibition, antiadhesion activity, membrane destabilisation and/or permeabilisation, and the chelation of metal ions [68].