Influence of maturity stages and variety on viscoelastic properties and mechanical toughness of the strawberries

Abstract

Introduction. This study aims to determine the influence of maturity stages and variety on the strawberries viscoelastic properties and to evaluate their mechanical toughness. Materials and methods. The fresh strawberry samples (Vibrant, Elsanta and Magic variety) were subjected to a creep test and the Burger model with four Kelvin Voigt elements was used to determine the viscoelastic parameters. The strawberry samples were divided on three maturity stages: almost ripe (S1), ripe (S2) and overripe (S3). Results and discussion. The strawberries samples were analyzed in terms of moisture content, soluble substances concentration, pH and total acidity. The moisture content ranged between 87.38 and 89.67%, the overripe maturity stage (S3) showing higher values of moisture compared to nearly ripe ones (S1), p<0.05. The highest concentration of soluble substances was recorded by Elsanta variety overripe maturity stage and followed by Magic (11.91) and Vibrant (11.57) varieties. The instantaneous elastic strain of strawberries ranged between 1.057 3.135 mm and the retardation time, which is correlated with storage period, varies from 10.92 to 140.83 s. The Pearson correlation matrix between physicochemical (moisture content, Brix concentration, pH and total acidity) and viscoelastic parameters (retarded and instantaneous elastic strain, retardation time, viscous strain, creep strain and area under the creep curves) highlighted a significant positive correlation between retarded elastic strain (€2) and the creep strain (p<0.01). Conclusions. The Vibrant strawberry variety had the highest resistance to mechanical impact and also a high mechanical resistance to compression due to the fact that showed the lowest values of instantaneous and retarded elastic strain.