Bioscience Evidence 2026, Vol.16, No.4, 329-344 http://bioscipublisher.com/index.php/be 337 by 3.7%-20.77% and 7.89%-26.35% across two growing seasons, respectively. This practice also increased the proportion of large tubers and reduced the number of small tubers, with ridge planting combined with full plastic film mulching showing the best performance (Shi et al., 2022). These yield improvements were associated with increased soil alkali-hydrolyzable nitrogen, available phosphorus, enzyme activity, and beneficial microbial populations. 6 Changes during Storage and Processing 6.1 Changes in nutritional components during storage Low-temperature storage generally causes limited changes in starch itself but significantly increases reducing sugar content through cold-induced sweetening (CIS), particularly under storage conditions at 4 ℃. Meanwhile, sucrose content usually decreases, accompanied by increased invertase activity (Galani Yamdeu et al., 2016). This response shows strong genotype dependence. CIS-resistant cultivars such as Verdi, Lady Claire, and Kiebitz can be stored at 4 ℃ for four months with only slight increases in glucose content, whereas susceptible cultivars such as Pirol, Agria, and Markies rapidly accumulate sugars during cold storage, resulting in brown to black chips after only two months of storage at 4 ℃ (Visse-Mansiaux et al., 2024). In colored potatoes, prolonged low-temperature storage may simultaneously increase reducing sugars, anthocyanins, and phenolic compounds; therefore, improved antioxidant capacity does not necessarily indicate improved processing suitability. Vitamin C and phenolic compounds show different patterns of change during storage. Multi-variety potato studies have shown that total phenolics and several phenolic acids may increase during storage under different temperatures, while antioxidant capacity generally increases during the early storage period and declines at later stages (Galani et al., 2017). Storage at 7 ℃ and 75% relative humidity is effective in reducing weight loss, sprouting, greening, and decay; however, this condition also promotes the greatest accumulation of simple sugars, with reducing sugar levels increasing by 26.0-68.5-fold, which is undesirable for frying processing (Gikundi et al., 2023). Therefore, storage of fresh-market potatoes mainly focuses on minimizing weight loss, sprouting, and visual quality deterioration, whereas processing potatoes require storage conditions that suppress sprouting while avoiding excessive sugar accumulation. 6.2 Effects of cooking methods Steaming, boiling, baking, and microwave heating all influence the color and nutritional composition of colored potatoes. Compared with more intensive or prolonged heat treatments, steaming and microwave heating generally preserve phytochemicals more effectively. In purple-fleshed potatoes, cooking treatments overall reduced vitamin C, phenolics, anthocyanins, carotenoids, and antioxidant activity; however, steaming and microwave treatments retained more health-promoting compounds, whereas stir-frying caused the greatest losses. In red- and purple-fleshed potatoes, microwave treatment increased the measured anthocyanin contents in all tested cultivars, while baking and boiling also resulted in slight increases. These increases were likely caused by heat-induced tissue disruption and enhanced pigment extractability rather than the formation of new anthocyanins (D’Amelia et al., 2022) (Figure 3). Boiling requires particular attention because hydrophilic compounds can easily leach into cooking water. Studies on colored root crops have shown that anthocyanin-rich purple tissues are more prone to color loss during boiling because water-soluble pigments dissolve into the cooking medium. In multi-variety potato studies after storage, boiling caused relatively limited losses; however, steaming and microwave treatment were more effective in retaining a broader range of phytochemicals.
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