How Vitamin C and Sugar Break Down Antioxidants in Stored Apple Juice

Greg Howard
20th August, 2024

How Vitamin C and Sugar Break Down Antioxidants in Stored Apple Juice

Image Source: Natural Science News, 2024

Key Findings

  • Researchers at Geisenheim University studied the stability of health-promoting flavan-3-ols in apple juices made with a new spiral filter press technology
  • Flavan-3-ols degrade faster in more concentrated apple juices, with up to 70% loss after 16 weeks at 20°C
  • Higher temperatures and sugar concentrations increase flavan-3-ol degradation, forming compounds that further accelerate this process
In recent research conducted by Geisenheim University, scientists explored the stability of flavan-3-ols in apple juices produced using a novel spiral filter press technology[1]. Flavan-3-ols, a group of plant compounds known for their potential health benefits, were retained in these apple juices. However, the factors affecting their stability during storage have not been thoroughly examined until now. The study produced flavan-3-ol-rich apple juices and concentrates with varying sugar content (16, 40, 70 °Brix) and supplemented them with different concentrations of ascorbic acid (0.0, 0.2, 1.0 g/L). The juices were then stored for 16 weeks at two different temperatures, 20°C and 37°C. Advanced analytical techniques, such as RP-UHPLC- and HILIC-DAD-ESI(-)-QTOF-HR-MS/MS, were used to monitor the flavan-3-ols and their reaction products during storage. The results demonstrated that flavan-3-ol degradation followed a second-order reaction kinetic, meaning the rate of degradation depends on the concentration of both flavan-3-ols and another reactant. The degradation was up to 3.5 times faster in the more concentrated juices (70 °Brix) compared to the less concentrated ones (16 °Brix). Furthermore, flavan-3-ols degraded significantly faster than other phenolic compounds present in the apple juices. For example, after 16 weeks at 20°C, flavan-3-ols experienced a maximum loss of 70%, whereas hydroxycinnamic acids and dihydrochalcones only decreased by 18% and 12%, respectively. The study also found that flavan-3-ols formed adducts with sugars and other carbonyl compounds, such as 5-(hydroxymethyl)furfural and L-xylosone, a degradation product of ascorbic acid[2][3]. The increased degradation rates of flavan-3-ols were particularly correlated with higher levels of furan aldehydes, which were more prevalent in the more concentrated juices stored at elevated temperatures. These findings build on earlier studies that investigated the role of ascorbic acid in the formation of colored species in model wine systems containing (+)-catechin, an oxidizable phenolic substrate. Previous research indicated that ascorbic acid could break down to form aldehydes or ketones capable of reacting with (+)-catechin to generate xanthylium pigments, which contribute to color changes in wine[3]. Another study showed that L-xylosone, a known degradation product of ascorbic acid, could react with (+)-catechin to form yellow pigments in wine-like conditions[2]. These insights align with the current study's observation that ascorbic acid-derived L-xylosone plays a significant role in the degradation of flavan-3-ols in apple juices. The current study's findings have practical implications for the production, distribution, and storage of flavan-3-ol-rich apple juices and other beverages. By understanding the factors that accelerate flavan-3-ol degradation, producers can optimize their processes to retain the health-promoting properties of these compounds for longer periods. For instance, minimizing the concentration of furan aldehydes and storing the juices at lower temperatures could help preserve flavan-3-ols. In summary, the research from Geisenheim University provides valuable insights into the stability of flavan-3-ols in apple juices. By identifying the factors that influence their degradation, this study offers practical solutions to enhance the shelf life and health benefits of flavan-3-ol-rich beverages.

FruitsNutritionBiochem

References

Main Study

1) Non-enzymatic degradation of flavan-3-ols by ascorbic acid- and sugar-derived aldehydes during storage of apple juices and concentrates produced with the innovative spiral filter press.

Published 19th August, 2024

https://doi.org/10.1016/j.foodres.2024.114827

Related Studies

2) Formation of pigment precursor (+)-1''-methylene-6''-hydroxy-2H-furan-5''-one-catechin isomers from (+)-catechin and a degradation product of ascorbic acid in a model wine system.

https://doi.org/10.1021/jf902198e

3) Understanding the contribution of ascorbic acid to the pigment development in model white wine systems using liquid chromatography with diode array and mass spectrometry detection techniques.

https://doi.org/10.1016/j.aca.2007.10.045


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