Abstract
Blueberry leaves, by‐products of the blueberry industry, could be explored as source of functional foods, such as teas. Three different types of tea, including nonfermented green tea, semifermented oolong tea, and fully fermented red tea from blueberry leaves, were investigated on their chemical compositions and antioxidant capacities here. The contents of individual amino acids in three types varied, while the total amounts retained constant. A total of 167 volatiles were detected with alcohols, alkenes, and aldehydes as the dominant. More volatiles produced in the fermented teas. The total phenolic/flavonoid contents were highest in the green tea and decreased significantly in the oolong and red teas, correlating inversely with the fermentation degree. The highest levels of representative phenolics, that is, phenolic acids and flavonol glycosides, contributed to the strongest antioxidant capacity in the green tea. These indicated that blueberry leaves provided promising and prospective potential to develop new teas beneficial for health.
Highlights
Blueberries (Vaccinium spp.), generally regarded as an excellent source of dietary antioxidant, are one kind of popular and healthy fruits worldwide (Wang et al, 2015)
The nonfermented green tea, semifermented oolong tea, and fully fermented red tea were manufactured from the fresh blueberry leaves, and their chemical constituents as well as antioxidant activities in vitro were compared in the present study
The green tea (GT) possessed the highest contents of phenolics and flavonoids, which decreased dramatically in the oolong tea (OT) and red tea (RT), showing an inverse correlation with the fermentation degree
Summary
Blueberries (Vaccinium spp.), generally regarded as an excellent source of dietary antioxidant, are one kind of popular and healthy fruits worldwide (Wang et al, 2015). Three different types of tea samples, including minimally, partially, and maximally oxidized blueberry leaf teas, were attempted to produce, respectively, according to the making process of the green, oolong, and red tea from C. sinensis. These three types of teas were named as green tea (GT), oolong tea (OT), and red tea (RT) from blueberry leaves hereafter. The changes of main chemical compositions and antioxidant capacities during the processing of different blueberry leaf teas were evaluated and compared Various profiles, such as amino acids, volatile aroma components, and phenolic compounds/flavonoids/proanthocyanidin, were further investigated on the development of tea quality. This study would contribute to current knowledge on the comprehensive utilization of the waste blueberry leaves as potential valuable resource, and the systematically development of novel tea varieties
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