Phenolic acids and flavonoids in tea processed from flowers of black elder (Sambucus nigra L.) stored in different packing materials.

摘要

The aim of the present study was to investigate the effects of cultivar, packing material and storage time on the content of phenolic acids and flavonoids in elderflower tea (ET) processed from flowers of the black elder (Sambucus nigra) cultivars 'Sampo', 'Sambu' and 'Samyl'. ET was processed by placing elderflowers in a thin layer on nylon screens in woody frames placed in a cool room and dried using a dehumidified air flow above and below the nylon screens for 96 h at 5 degrees C. The yield of ET for the cultivars 'Sampo', 'Sambu' and 'Samyl' were 12.8%, 15.7% and 8.9%, respectively. A clear significant difference in the content of polyphenols was found between ET processed from the three cultivars. The total content of phenolic acids was significant higher in 'Samyl' (41.3 mg g-1 ET) compared to 'Sampo' (33.8 mg g-1 ET) and 'Sambu' (34.0 mg g-1 ET). 'Sambu' had the lowest content of flavonoids (25.7 mg g-1 ET), whereas the highest content was found in 'Sampo' (33.5 mg g-1 ET). ET samples were packed in bags of brown paper at normal pressure and under vacuum in polyethylene plastic bags and in aluminium foil bags comprised of polyamide, aluminium and polyethylene, respectively, and stored at 0 (non-stored), 3, 6, 9, 12, 15, 18 and 21 months. Principal components analysis and multiple linear regression analysis taking into account the correlation and interactions between packing material, storage time and cultivar showed, however, that packing materials and storage time only had a minor effect on the content of phenolic acids and flavonoids in ET. The overall conclusion of the following study is that polyphenols in ET are relatively stable during storage up to 21 months and that the content of phenolic acids and flavonoids in ET is mainly determined by the choice of cultivar/genotype. To maintain a good flavour of ET during storage paper bags are clearly less preferable than aluminium foil and plastic packing materials and therefore the best choice of packing material for ET seem to be aluminium foil based packing materials.