From proanthocyanidins in grape seeds to catechins in green tea, natural polyphenols are highly sought after for their potent antioxidant properties and extensive health benefits. So, where does one of the most common fruits in our daily lives-apples-stand in this "rich mine" of polyphenols?
1. Apple Polyphenols: Definition and Core Value
First, we need to clarify what apple polyphenols are. Apple polyphenols are not a single compound but a collective term for various phenolic substances found in apples. These substances primarily include flavonol compounds (such as quercetin and its glycosides), flavan-3-ols (such as catechin, epicatechin, and proanthocyanidins), phenolic acids (such as chlorogenic acid), and dihydrochalcones (such as phloridzin).[1] It is precisely these diverse compounds that collectively form the robust biological activity foundation of apples, enabling them to demonstrate significant potential in areas such as antioxidant effects, cardiovascular protection, and even anti-tumor properties.[1, 2]
2. Apple Polyphenol Content: A Topic Full of Variables
So, how high is the polyphenol content in apples? This seemingly simple question is actually difficult to answer in a single statement. By reviewing existing research data, we found that multiple factors significantly influence its content.
2.1 Variety Differences: The "Genetic" Variations in Polyphenol Content
There are significant differences in polyphenol content among various apple varieties, a fact widely recognized in the industry. For instance, a study analyzing 15 different apple varieties found notable variations in their total polyphenol (TP) levels. [105] Some studies have provided more specific numerical data:
- Fuji Apples: As a mainstream variety in the market, Fuji apples have relatively high levels of phenolic compounds. Research data indicate their content approaches 230 mg/100 g. Another study on browning during storage measured the total phenolic content in Fuji apple flesh at 726.0 mg/kg (i.e., 72.6 mg/100 g).[4]
- Kozara Apple: A 2024 study revealed that the "Kozara" apple variety, with a total polyphenol content of 217.37 mg GAE/100g fresh weight (fw), stands out among multiple tested varieties.
- Other varieties: Research indicates that the total phenolic content ranges from 66.2 to 211.9 mg/100 g fresh weight, and can even reach an astonishing 2723.96 mg/100 g dry weight under certain varieties and specific conditions. The polyphenol content of varieties such as Golden Delicious, Gala, and Granny Smith has also been extensively studied.[3]
2.2 Distribution by Part: Apple peel is a true "polyphenol treasure trove."
The distribution of apple polyphenols is highly uneven, with significantly higher concentrations in the peel than in the flesh. Multiple studies consistently confirm that the total phenolic content in apple peels can be several times that of the flesh.[1, 5] This means that the apple peels discarded during daily consumption are precisely the most nutrient-dense part.
Returning to our original question: Is the polyphenol content in apples high? The answer is yes-apples are undoubtedly a significant dietary source of polyphenols. However, for the plant extract industry that prioritizes standardization and high efficiency, "high" is a relative and dynamic concept. The polyphenol content in apples varies significantly depending on the variety. Additionally, processing methods directly determine the final polyphenol content in the product.
For more details about Apple Polyphenol, connect with Serrisha from APPCHEM. (Email: cwj@appchem.cn; +86-138-0919-0407)
Reference
[1]5º Encontro em Biotecnologia Medicinal / 2nd Iberian Congress on Medicinal Biotechnology. Escola Superior de Saúde, P.PORTO. [2022-10-21]
[2]Xiangjiu He, R. Liu. "Triterpenoids isolated from apple peels have potent antiproliferative activity and may be partially responsible for apple's anticancer activity." Journal of agricultural and food chemistry (2007). [2007-05-08]
[3]Assessing Comparatively The Bioactive Compounds Composition Of Apple Pomace Obtained From Three Apple Cultivars After Juice Extraction. I. Taranu et al.
[4]Effects of Different Dwarfing Rootstocks on Total Phenols and Their Components in Huahong Apple Fruits. Li Qingshan et al.
[5]Stability of phenolic compounds and drying characteristics of apple peel as affected by three drying treatments. Qiancheng Ma et al.[2020-01-22]