Impact of Rainfall and Air Temperature Before Harvest on Content and Response of Carotenoids, Tocopherols, and Vitamin C to Postharvest Thermal Processing of Tomato

This research aimed to explore the influence of climate factors, especially in the three weeks prior to harvest, on the reaction of key phytonutrients in industrial tomatoes used for juice thermal processing and their stability. The cultivation was performed in two areas with differing climatic conditions. In the region with higher temperatures and rainfall, the levels and stability of carotenoids were lower compared to the area characterized by warm temperatures and minimal rainfall during both the growth and harvest phases of the tomatoes. The extraction of cold-break (CBE) tomatoes from relatively cool and wet environments resulted in a loss of total carotenoids, particularly lycopene, amounting to 66% and 58% of the initial raw tomato content in 2018 and 2019, respectively, while a markedly reduced loss of 10% was observed after the CBE of tomatoes from the warmer and drier region in both years (36% and 35%). In contrast, hot-break extraction (HBE) demonstrated a higher stability of lycopene compared to CBE, with losses of 43% and 53% in 2018 and 2019, respectively. Additionally, the stability of lycopene in HBE did not show significant differences between the cultivation sites. Climatic conditions influenced the accumulation of geometrical isomers and oxidized forms of lycopene and β-carotene, especially in tomatoes grown in areas with higher rainfall and lower temperatures. A similar trend in response was noted for β-carotene, lutein, phytoene, and phytofluene, as well as total and individual tocopherols. Regarding vitamin C, the environmental factors had no meaningful impact on the vitamin content in tomato fruits; however, its stability during processing, especially with hot-break extraction, was considerably influenced by the climatic conditions of the cultivation site, with p values ranging from <0.01 to <0.001 across different products in various years. The content and stability of phytonutrients in pomace, the by-product from tomato juice processing, were also assessed. In conclusion, tomato fruits and processed products that boast high phytonutrient levels and stability during thermal processing can be achieved through cultivation in conditions of low rainfall and relatively high temperatures, particularly in the three weeks leading up to harvest.