In this work, the impact of the industrial freezing process on structure, texture and total antioxidant capacity was
studied using green asparagus stems, zucchini and green beans. Samples were analysed as raw/uncooked,
blanched, raw/boiled and industrially frozen/boiled.
A consistent damage of the vegetable tissue was revealed by the histological analysis on vegetables boiled after
freezing. The cells appeared to be dehydrated, contracted and separated at different levels depending on the
anatomical structure of each vegetable.
The initial textural quality was partially retained in all blanched vegetables, and enhanced in cut tested asparagus
stems, in relation to the action of phenolic acids at cell wall level. Raw/boiled and industrially frozen/boiled asparagus
stems exhibited comparable forces of penetration and cut tests. On the other hand, zucchini, both raw and
frozen, completely softened after boiling making the texture measurement impossible. Industrially frozen/boiled
green beans showed higher values of cut and penetration forces, probably due to a higher presence of swollen cell
walls, in comparison to those raw/boiled.
Blanching and boiling significantly increased the ferric reducing antioxidant power values of asparagus stems and
green beans compared to uncooked/raw samples, while boiling after the freezing process significantly deprived
both vegetables of the initial antioxidant capacity. On the other hand, boiling the frozen zucchini proved to be
detrimental to the antioxidant capacity.
In conclusion,manufacturers and researchers should join together to develop specific industrial freezing process
conditions according to the matrix of each vegetable.