Asparagus

Botanical Profile

Asparagus officinalis is a perennial vegetable and cultivated plant of the Asparagaceae family. The young shoots are used primarily; roots, herb and processing side streams are also described in research and raw-material science.

Asparagus officinalis L. is a perennial herbaceous plant with an underground rhizome, fleshy storage roots and young shoots emerging in spring. These young shoots form the vegetable asparagus. If left to grow, they develop into branched aerial shoots with fine, needle-like cladodes, small flowers and red berries. White asparagus is produced by cultivation under soil and exclusion of light, whereas green asparagus develops above ground and forms chlorophyll. Botanically, the young shoots, mature herb, roots and berries must be clearly distinguished. The berries are not suitable as a conventional food raw material. As a cultivated plant, asparagus is widespread in temperate regions and has a long European horticultural and culinary tradition.

Phytochemistry

Asparagus shoots contain water, dietary fibre, sugars, amino acids, minerals, organic acids, saponins, flavonoids, sulphur-containing aroma precursors and vitamin-rich fractions. Asparagine, an amino acid historically described from asparagus, is characteristic. Sulphur-containing compounds and their metabolites are important for the typical aroma. Roots and herb have different profiles, including steroidal saponins, flavonoids and accompanying phenolic compounds. Composition varies between white and green asparagus and according to cultivar, harvest time, soil, storage and processing. Freshness, fibrousness, bitterness, aroma and nitrate or residue parameters are relevant to food quality.

Traditional Uses

Asparagus has been known since antiquity as a vegetable and garden plant. In European cuisine it has been particularly valued as a seasonal spring vegetable. In certain growing regions, white asparagus developed into a culturally important speciality vegetable, whereas green asparagus is characterised more strongly by chlorophyll-rich, more pronounced sensory properties. Older herbal traditions also describe uses of the root and herb, which should be distinguished from the usual culinary use of the young shoots. The traditional significance of asparagus combines nutrition, seasonality, horticulture and regional food culture.

Current Research

Research on Asparagus officinalis addresses vegetable quality, saponins, phenolic compounds, aroma, storage, breeding, fibrousness, yield physiology and processing. Studies investigate differences between white and green asparagus, changes after harvest and storage, and constituents of side streams such as peel or woody shoot sections. Steroidal saponins and flavonoids are investigated in experimental models, while food studies focus more strongly on freshness, texture, aroma and nutrient profile. Findings from root or side-stream extracts cannot automatically be transferred to fresh shoots.

Sources

• Plants of the World Online: Asparagus officinalis L.; Royal Botanic Gardens, Kew.
• Food-science and horticultural literature on Asparagus officinalis.
• Scientific literature on asparagus saponins, aroma and processing quality.