Influence of ascorbic acid infusion and heat treatment on the flavour of frozen asparagus (asparagus officinalis l.)

The influence of 3 treatments – vacuum infusion of ascorbic acid, a brief heat treatment, and a combination of both treatments, on the flavour of frozen asparagus (Asparagus officinalis L.) was studied. The effects of the treatments were evaluated for the apical, middle and basal sections of the asparagus by ascorbic acid and hexanal measurements, as well as by sensory. analysis of apical sections. The asparagus sections were vacuum infused with 1% (w/v) ascorbic acid solution for 3 min. The heat treatment involved conventional boiling in water for 4 min. Ascorbic acid and hexanal analyses were conducted after 0, 5 and 7 weeks of storage at -18degreesC, and sensory evaluation after 7 weeks. Infusion increased ascorbic acid levels and decreased hexanal levels significantly throughout the storage period. Heat treatment decreased initial ascorbic acid levels, but resulted also in improved ascorbic acid retention and reduced hexanal formation during storage. The combination of both treatments showed highest ascorbic acid and lowest hexanal concentrations at the end of the storage period. Sensory evaluation of flavour and appearance confirmed the instrumental measurements, demonstrating higher flavour ratings for the treated asparagus samples, and in particular for the combination treatment.