Original research articleEffect of cultivar and storage temperature on identification and stability of polyphenols in strawberry cloudy juices

- Cloudy strawberry juices were compared in the terms of polyphenols content.
- Products obtained from 7 cultivars (cvs.) were stored for 6 months at 4 and 20 °C.
- Cultivar, molecular structure and storage conditions influence polyphenols stability.
- Anthocyanins are the least stable active compounds of strawberry juices.
- 'Kimberly' cv. is the most useful for the production of high quality cloudy juices.

The effect of strawberry (Fragaria x ananassa Duchesne) cultivars (cvs) and storage temperature on the stability of polyphenols in cloudy juices was determined. Identification of phenolic compounds by ultra performance liquid chromatography-electrospray ionization/mass spectrometry (UPLC-ESI/MS), as well as quantitative analysis by ultra-performance liquid chromatography-photodiode array-fluorescence (UPLC-PDA-FL), were carried out on fresh and stored products (6 months, 4 °C and 20 °C) from 7 different strawberry cvs. A total of 32 polyphenolic compounds were identified: flavan-3-ols (6), anthocyanins (8), flavonols (4) and flavones (3), hydroxycinnamic acids (4), and ellagic acid derivatives (7). Total polyphenol content ranged from 642.08 mg/L in fresh 'Florence' cv. juice to 296.72 mg/L in 'Honeoye' cv. juice after 6 months of storage at 20 °C. Anthocyanins (max. 161.40 mg/L in 'Honeoye' juice) demonstrated the greatest degree of degradation (31-100%, depending on the molecular structure and temperature). Cyanidin-3-malonylglucoside was less labile than 3-glucoside. In the case of pelargonidin glycosides, 3-glucoside was more stable. The degradation process was the least advanced in 'Kimberly' cv. juice (58.53% at 4 °C). Storage conditions also influenced the decrease in p-coumaroyl-hexose, and quercetin-glucuronide content. However, low temperatures limited this process. This was especially noticeable in 'Florence' and 'Honeoye' cvs. In turn, proanthocyanidins showed the most stability and were the main polyphenols identified in juices (212-434 mg/L). Generally, it was observed that the total content of polyphenols and their stability in juices was dependent on the cultivar, and the duration of storage conditions.