Effect of Freezing/Thawing Temperature on the Viscoelastic and Nutritional Qualities of Carrots

Abstract

This study evaluated and correlated the viscoelastic and nutritional properties of carrots after freezing (-20,-70, and-196oC) and thawing (4 and 18oC) treatments. Results showed that all samples exhibited a solid behavior (storage modulus G′ > loss modulus G″) dominating the viscoelastic response. After treatments, G′, G″, hardness, fracturability, springiness, and chewiness of carrots significantly decreased, whereas loss tangent (Tanδ) increased. Compared with other treatments, fast freezing (-196oC) and thawing (18oC) better maintained G′, G″, hardness, and fracturability of carrots, and intermediate freezing (-70oC) better retained springiness, cohesiveness, and chewiness. For nutritional parameters, fast freezing and thawing conditions also contributed to preserving the contents of carotenoids of carrots. Partial least squares regression analysis revealed that β-and -carotene, lycopene, and soluble sugars were positively correlated with hardness, fracturability, G′, and G″, and negatively with Tanδ in carrots. The variation of viscoelastic parameters could well predict the changes at nutritional levels.