# Designing the Quality Characteristics of Berry Processing Byproducts Using Fermentation
## 4 Discussion
As proven in numerous studies, bioactive compounds (phenolics, flavonoids, organic and fatty acids, peptides, volatiles, and enzymes) resulting from fermentation can inhibit the growth of commonly occurring food spoilage mold and be used as natural preservatives [55; 56; 57; 58; 59]. This effect was also observed in the experiments that were performed. Although molds grew on both PCA and Sabouraud agar in the control, their growth was not observed on the fermented sample cultures (except for blackcurrant samples fermented with lactic acid bacteria). Notably, [PERSON] and [PERSON] [60] demonstrated the ability of _Saccharomyces cerevisiae_ strains to inhibit the production of mycotoxins. The inhibition of microorganism growth in pomace was also determined by changing the quantitative ratio of individual microorganism groups in the control and fermented pomace samples. For all control samples, except for blackcurrant, the most numerous colonies observed grew on the medium used to determine the total number of microorganisms (PCA). Following 48 h of fermentation using lactic acid bacteria, notably fewer colonies were observed on the PCA medium for the raspberry pomace sample. This was also observed for the chokeberry pomace sample fermented with yeast and a mixture of lactic acid bacteria and yeast. The obtained results confirm the beneficial effect of fermentation on the microbiological quality of the tested pomace. Fermentation with microorganisms presents a potential approach to modifying the composition of berry pomace by increasing the content of key compounds that contribute to its biological activity. Additional benefits of fermentation include the low temperature required, which helps preserve heat-sensitive compounds, such as vitamin C and polyphenols. Improving the biological activity of fruit pomace is one of the potential and emerging applications of fermentation. In this work, this strategy was applied to obtain berry pomace with higher TPC and ascorbic acid (vitamin C) contents, as well as antioxidant activity (assessed via ABTS, DPPH, and FRAP assays). Three different mixtures of microorganisms were applied to improve the biological activity of chokeberry, blackcurrant, raspberry, and strawberry pomace samples (Table 1). Vitamin C is a water-soluble vitamin that is present in fruits and has many nutritional and clinical benefits for human health. In particular, it acts as a strong antioxidant through its electron donation potential [61]. Fermentation with a mixture of lactic acid bacteria (_Lactobacillus acidophilus, Lactococcus lactis_ subsp. _lactis_, and _Lactobacillus rhamnosus_) led to a significant increase in vitamin C content in all berry pomace samples compared with the control samples. These results are in agreement with previous studies [62; 63] that reported an increase in ascorbic acid content in orange juice following fermentation with lactic acid bacteria. The greatest increase in vitamin C content occurred when chokeberry pomace was fermented with lactic acid bacteria. The growth was over 90% compared to the control sample. All fermented berry pomace samples had a higher level of vitamin C than the control sample, suggesting that microorganisms may play a role in synthesizing vitamin C during fermentation [64]. However, fermentation with _Saccharomyces cerevisiae_ led to moderate growth of vitamin C for chokeberry and blackcurrant samples, exhibiting increases of over 20% and 55%, respectively. In raspberry and strawberry samples fermented with yeast, vitamin C was not statistically significant compared to the control sample. In terms of the fermentation process, a mixture of lactic acid bacteria and yeast led to an increase in vitamin C content only for chokeberry pomace. Phenolic acids are associated with the biological activity and sensory qualities of foods [65]. Therefore, we investigated the evolution of TPC in berry pomace samples during fermentation with _Saccharomyces cerevisiae_.