Abstract
Phenolic compounds in apples 17 cultivars (Malus domestica Borkh.) and 3 wild forms (Malus sp.) were analyzed to study the impact of genetic background, growth site, and fruit bagging. The impact of altitude was studied in nine cultivars by analyzing fruits collected from orchards at three altitudes. Procyanidin B2 (71–628 μg/g fresh weight), ( −)-epicatechin (35–357 μg/g), and chlorogenic acid (28–563 μg/g) were always the three most abundant phenolic compounds in the apple samples studied, except for the cultivar ‘Qinguan’, which had a very low content of ( −)-epicatechin (13 μg/g) and procyanidin B2 (8 μg/g). The wild apples of M. prunifolia (Willd.) Borkh were 5-times richer in epicatechin (278 μg/g) and procyanidin B2 (628 μg/g) than the commercial cultivars of M. domestica Borkh (86 and 54, respectively). Among the commercial cultivars, ‘Qinguan’ had the highest level of chlorogenic acid but the lowest content of flavan-3-ols, whereas ‘Liuyuehong’ was characterized by the highest content of quercetin glycosides. Procyanidin B2, and ( −)-epicatechin correlated negatively, while other phenolics positively, with altitude. The response of phenolic compounds to altitude variation depended on latitude variation and genetic backgrounds. Bagging treatment reduced the contents of most phenolic compounds, with the impact of cultivars and length of re-exposure before harvest. This is also the first report on phenolic compounds in several important new cultivars, adding new knowledge on the compositional characteristics of global apple resources.
Highlights
Apples are among the most widely consumed fruits in the world
Phenolic compounds are key components contributing to astringency and bitterness of apples, and play a role in color, aroma, and flavor of apple products such as apple cider and apple vinegar
The most abundant phenolic compounds in the samples studied fell into four groups: flavanols (mainly ( −)-epicatechin and procyanidin B2), hydroxycinnamic acid derivatives, flavonol glycosides, and dihydrochalcones
Summary
Apples are among the most widely consumed fruits in the world. Apples are rich in phenolic compounds, vitamins and other phytochemicals [1,2,3]. Phenolic compounds reported in apples belong to five major classes, namely. Phenolic compounds are key components contributing to astringency and bitterness of apples, and play a role in color, aroma, and flavor of apple products such as apple cider and apple vinegar. Phloridzin and chlorogenic acid are two major phenolic compounds in apple fruit. Phloridzin is a commonly known bitter compound contributing to the bitterness of both apples and apple ciders, whereas chlorogenic acid, a non-bitter phenolic acid, is a precursor of a range of bitter compounds which can be formed as degradation products of chlorogenic acid during processing [17]. The composition and content of phenolic compounds may have a key influence on the sensory quality of apples and apple products
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