Effects of postharvest ultraviolet-B light applications on the storage of different types of pepper varieties

The aim of this thesis was to determine the effects of postharvest UV-B illimunation at different doses on the storage and shelf-life of capia and chile pepper types. For this purpose, the effects of ultraviolet-B (UV-B) treatments at doses of 8, 16, and 24 kJ/m² were investigated on the storage and shelf-life of the 'Star' (Capia) and 'Kızıl' (Chile) pepper cultivars, harvested at commercial maturity. After harvest, the peppers treated with UV-B illimination were placed on foam trays, sealed with stretch film, and stored at 8°C with 90-92% relative humidity. Additionally, during the storage period, samples were subjected to shelf-life testing at 20°C and 65-70% relative humidity for 3 days at specific intervals. During the study, parameters such as weight loss, fruit color values (h°, C*, and L), titratable acidity (TA), soluble solid content (SSC), total phenolic content (TPC), antioxidant activity (AA), ascorbic acid content, and total carotenoid content were evaluated at 10-day intervals during storage and shelf life periods. In the study, the highest weight loss of the Capia type 'Star' and Chile type 'Kızıl' peppers cultivars was observed in the control group under both cold storage and shelf conditions. While lower weight loss was recorded with UV-B treatments, no statistical difference was found among the UV-B doses. However, at the end of the shelf-life period, 16 and 24 kJ/m² UV-B treatments resulted in lower weight loss in the 'Star' variety. At the end of the storage period, the lowest average h° value was found in the 'Star' cultivar with the 24 kJ/m² UV-B treatment, while all UV-B doses exhibited similar values for the 'Kızıl' cultivar. During shelf life conditions, both varieties showed lower h° values for the UV-B doses of 8, 16, and 24 kJ/m². Throughout storage and shelf-life conditions, the highest C* value was observed with the 8 kJ/m² UV-B dose for the 'Star' variety and the 24 kJ/m² dose for the 'Kızıl' variety. Both cultivars exposed to UV-B radiation during storage and shelf conditions exhibited higher L* values compared to the control. At the end of storage and shelf-life periods, the levels of SSC and TA were significantly higher in the UV-B treated peppers compared to the control group. For both cultivars, UV-B treatments of 8 and 16 kJ/m² increased the TPC at the end of storage. In the 'Star' variety, the average AA activity, during storage was high for the 8 and 16 kJ/m² treatments, while under shelf-life conditions, the 8 kJ/m² treatment was more effective. For the 'Kızıl' cultivar, the 8 kJ/m² UV-B treatment resulted in the higher levels of AA and ascorbic acid levels. The 8 kJ/m² UV-B treatment was found effective in slowing down the decrease in ascorbic acid levels in the 'Star' cultivar. With respect to total caroteneid content, the 8 and 16 kJ/m² UV-B treatments stood out for both varieties. In conclusion, UV-B light applications in both varieties provided positive contributions in terms of color and biochemical properties. In the study, 8 kJ/m2 UV-B application is considered suitable for both varieties as it demonstrated higher ascorbic acid and antioxidant activity compared to other doses after storage and shelf-life conditions.