Long-Term Frozen Storage and Pasteurization Effects on Strawberry Polyphenols Content

Abstract

The profile of the strawberry polyphenols was analysed on fresh strawberry, immediately after freezing or after pasteurization and during frozen storage of strawberry at −20°C for 360 days. Freezing increased the extractability of (−)-epigallocatechin gallate (60 %), (−)-epicatechin (48 %) and ellagic acid (51 %) and decreased the pelargonidin-3-glucoside (18 %). Direct pasteurization of fresh strawberry increased the extractability for (−)-epigallocatechin gallate (73 %), (−)-epicatechin (45 %) and ellagic acid (143 %) and decreased for pelargonidin-3-glucoside (16 %). During storage at −20°C for 360 days the extractable levels of pelargonidin-3-rutinoside, (−)-epigallocatechin gallate, (+)-catechin, (−)-epicatechin and ellagic acid decreased by 17, 20, 37, 65 and 80 %, respectively, while those of pelargonidin-3-glucoside increased 13 %. Changes in polyphenols content, produced by pasteurization after 360 days frozen storage, were minimal. Polyphenols content decreased during storage of strawberry pieces at −20°C for 360 days, while the thermal treatment applied after freezing storage did not induce any significant change.

High–Pressure Processing vs. Thermal Treatment: Effect on the Stability of Polyphenols in Strawberry and Apple Products

“…An increase in catechin (42%) was also observed in strawberry pulp treated at 70 °C for 2 min [ 44 ]. In the same direction, Oliveira et al [ 31 , 32 ] reported increments on (+)-catechin, (–)-epigallocatechin, (–)-epicatechin, and (–)-epigallocatechin gallate levels in entire strawberries pasteurized at 90 °C for 5 min. However, after 360 days of storage at –20 °C and 90 days at 23 °C, the concentration of the monomers decreased compared to the content evaluated immediately after processing, although they were still higher than the fresh control [ 31 , 32 ].…”

“…In the same direction, Oliveira et al [ 31 , 32 ] reported increments on (+)-catechin, (–)-epigallocatechin, (–)-epicatechin, and (–)-epigallocatechin gallate levels in entire strawberries pasteurized at 90 °C for 5 min. However, after 360 days of storage at –20 °C and 90 days at 23 °C, the concentration of the monomers decreased compared to the content evaluated immediately after processing, although they were still higher than the fresh control [ 31 , 32 ]. Conversely, a general increase in polymeric PACs was observed in thermally treated (90 °C/2 min) cloudy strawberry juice kept at 4 and 20 °C for six months [ 37 ].…”

Effect of different freezing methods on the bioaccessibility of strawberry polyphenols

“…Although there are a few studies in the literature investigating the chemical changes that are induced to strawberry polyphenols during freezing (Oliveira et al ., ; Bulut et al ., ), as far as it is known, no previous study examined the effect of freezing process on the bioaccessbility of strawberry polyphenols. Considering that, the aim of this study was (i) to investigate the digestive stability of polyphenols from fresh and frozen strawberries as well as the changes in their antioxidant activity using the standardised in vitro model that simulates oral, gastric and small intestinal digestion, and (ii) to compare effects induced by IQF and CF.…”

Anthocyanin Recovery from Grape by-Products by Combining Ohmic Heating with Food-Grade Solvents: Phenolic Composition, Antioxidant, and Antimicrobial Properties

“…Mostly, according to several studies, the inhibition of polyphenol oxidases and acid hydrolysis could occur; as a result, the TPC increases, and consequently, the AA also increases [18,30,31]. The differences found in TPC and AA when citric acid (C 6 H 8 O 7 ) or lactic acid (C 3 H 6 O 3 ) were used could be explained by its chemical structure and its pH solution, 2.55 and 2.98, respectively.…”