Matrix- and Technology-Dependent Stability and Bioaccessibility of Strawberry Anthocyanins during Storage.

Anna-Sophie Stübler,Avi Shpigelman,Andreas Juadjur,Volker Heinz,Cornelia Rauh,Lena Böhmker,Kemal Aganovic

doi:10.3390/antiox10010030

Abstract

Anthocyanins are often associated with health benefits. They readily degrade during processing and storage but are also dependent on the matrix conditions. This study investigated how strawberry anthocyanins are affected by preservation technologies and a relatively protein-rich kale juice addition during storage. A strawberry–kale mix was compared to a strawberry–water mix (1:2 wt; pH 4), untreated, thermally, pulsed electric fields (PEF) and high-pressure processing (HPP) treated, and evaluated for anthocyanin stability and bioaccessibility during refrigerated storage. The degradation of strawberry anthocyanins during storage followed first-order kinetics and was dependent on the juice system, preservation technology and anthocyanin structure. Generally, the degradation rate was higher for the strawberry–kale mix compared to the strawberry–water mix. The untreated sample showed the highest degradation rate, followed by HPP, PEF and, then thermal. The relative anthocyanin bioaccessibility after gastric digestion was 10% higher for the thermally and PEF treated samples. Anthocyanin bioaccessibility after intestinal digestion was low due to instability at a neutral pH, especially for the strawberry–kale mix, and after thermal treatment. The storage period did not influence the relative bioaccessibility; yet, the absolute content of bioaccessible anthocyanins was decreased after storage. This research further presents that processing and formulation strongly affect the stability and bioaccessibility of anthocyanins during storage.

Highlights

Anthocyanins are polyphenolic compounds and an important pigment of many fruits and vegetables
The high-pressure processing (HPP)-treated strawberry-kale mix and kale-water mix were microbiologically stable, while the thermally and pulsed electric fields (PEF)-treated named mixes exhibited outliers or an increase in the total aerobic plate count during storage. This could be related to the possible recontamination during the manual filling of the samples after PEF and thermal treatments, while the HPP was applied to the samples in the package
The degradation constant was significantly higher for the strawberry–kale mix compared to the strawberry–water mix, meaning that anthocyanins are less stable in the complex strawberrykale mix

Summary

Introduction

Anthocyanins are polyphenolic compounds and an important pigment of many fruits and vegetables. They are reported to exhibit health-promoting properties, reducing the risk for cardiovascular diseases, cancer and diabetes by their capacity to scavenge free radicals and indirectly inhibit cell proliferation [1]. Anthocyanins are unstable and readily degrade and undergo oxidation or polymerization reactions during processing and storage due to their chemical structure. Due to increasing consumer demand for products with potential health effects and minimally processed products, more complex juices, such as blends and smoothies with considerable amounts of anthocyanins, are developed and, in some cases, on the market, Antioxidants 2021, 10, 30. The occurrence and rate of these reactions are influenced by the presence of oxidative enzymes such as polyphenoloxidase or peroxidase and other food compounds (e.g., vitamin c and fructose), pH value, exposure to light and high temperature [3,4,5,6].

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Results

Conclusion