## 4 Discussion
Meanwhile, TPC varied slightly between fruit at the beginning of ripening and mid-ripening, but TPC content was twice as high in fully mature fruit as shown in a study by [PERSON] et al. [47]. Although there are evident tendencies for antioxidant activity to increase in later maturity stages as in our study (Tables 1-3). Also, some studies found that these changes maydepend on the variety of tomatoes. In research conducted by [PERSON] et al. [48], the results show antioxidant activity in tomato fruits to be higher in green-orange and orange-red ripening stages and the lowest at the green and red-ripe stages in all investigated cultivars except, Donald which seemed to be unaffected by the ripening process. Similar results were reported by [PERSON] et al. for the cherry tomato cultivar Naomi grown in a greenhouse [45]. Also, similar but contradictory results were published by [PERSON] et al., where the highest antioxidant activity was found in the fruit of the green stage, and the lowest activity was recorded in the fruit of the red-ripe stage [46]. This study shows a significant influence of the fruit ripening stage on the total carotenoid and lycopene contents and antioxidant activity in all investigated cultivars, which show good correlations between antioxidant activity and the mentioned compound contents [46]. It is known that the antioxidant activity of fruits can be determined not only by the ripening of the fruit but also by its genotype and growth conditions, the digestate also influenced our results. As shown by the two-factor ANOVA analysis, both digestate addition and fruit maturity, the interaction of these factors had a significant effect (Tables 1-4). [PERSON] et al. found the antioxidant activity to remain unchanged during the fruit ripening of the tomato variety cultivar Marmande-Cuarenteno [49]. [PERSON] et al. even found the antioxidant activity to continuously increase during the development of the fruit until the light red stage and depending on the cultivar to reach maximum values and then decline significantly [50]. Tomato variety Grandela was investigated at different ripening stages while treated with varnauba and mineral oil. Results showed mineral oil significantly positively affected antioxidant activity at all stages of fruit ripening [51]. [PERSON] et al. [52] experimented with \"TY Megaton\" and \"Yureka\" tomato variety cultivars. They concluded that tomato fruits harvested at different ripening stages and postharvest ripening under room conditions mature without affecting antioxidant activity capacity. Our findings suggest that fruit maturity when harvested has a significant difference in antioxidant activity even without storage, although further investigation is needed. The action of digestate may be explained by analyzing the composition of digestate itself. Most digestates are rich in nitrogen, either in ammonium or nitrate forms. It also shows the contents of phosphorus, potassium, calcium, magnesium, and chlorides [53]. These supplementary elements added to the substrate may interact with plant roots and change the dynamics of micro- and macro-element absorption [54]. Our tested digestate is very rich in phosphorus and also contains a high amount of nitrogen (0.406% total nitrogen (N), 1.81% phosphorus (P\({}_{2}\)O\({}_{5}\))). Nitrogen in the soil present in the ammonium form is usually tightly bound to the cation exchange complex, so more accessible forms of nitrogen are in nitrate form. When absorbed into the root cell wall spaces and through the membrane into the plant cells, it is used for amino acid synthesis. Ammonium can enter into amino acid synthesis directly, but nitrate must first be reduced to the ammonium form [55]. Another important constituent in the digestate mechanism of action is phosphorus because this element affects all biological processes in the plant. It is important for energy exchanges, nucleic acids, RNA, and DNA. Even photosynthesis and respiration are energized by inorganic phosphate or its organic derivatives.