Phenolic composition of Croatian olive leaves and their infusions obtained by hot and cold preparation
2021
Valerija Majetić Germek | Paula Žurga | Olivera Koprivnjak | Kristina Grozić | Iva Previšić | Šime Marcelić | Smiljana Goreta Ban | Igor Pasković
Leaves and infusions of six Croatian olive cultivars grown in an organic orchard under the same agronomic conditions were characterised by high-performance liquid chromatography-ultraviolet/visible spectrophotometry (HPLC-UV/VIS). The total identified phenols in leaves ranged from 3 818 mg 100 g-1 [cultivar Istarska crnica (IC)] to 10 572 mg 100 g-1 of dry mass [cultivar Oblica (OB)]. The canonical discriminant analysis (CDA) provided a distinct separation of cultivars based on leaves' phenolic profiles. Hot- and cold-water infusions (200 mL) were prepared from 1 g of dry leaves. The average transfer rate of the total phenols in the cold-water infusions was 40% (25 °C/30 min), while in the hot-water infusions was 63% (75 °C/3 min) and 76% (100 °C/3 min). Although the cold-water infusions had the lowest transfer rate, they contained important levels of hydroxytyrosol derivatives ranging from 16.6 mg 200 mL-1 to 36.5 mg 200 mL-1 depending on the cultivar. Therefore, both hot and cold preparations are effective in obtaining antioxidant-rich natural beverages.
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