Epsilon Archive for Student Projects

Abstract

Asparagus officinalis is an edible immature shoot cultivated all over the world and sold as a seasonal delicacy. Harvest season in Sweden stretches from between 8 to 12 weeks and these local spears are often considered to be of hight quality among consumers. However, clarification as to how different factors affects asparagus spear quality can be beneficial to maintain acceptable standards, and to solve future challenges which may arise with changed weather patterns due to climate change. This paper is a literature study, discussing factors before harvest that can affect quality of green asparagus from a Swedish perspective. How climate change may alter future field conditions in Sweden and hence spear quality is also included.
Asparagus physiology affected mostly textural quality since the bottom section was more fibrous and lignified than the immature top section. Harvested spear diameter affected quality by having more portions of fibrous and lignified tissue in relation to volume, while tall spears had more concentration of fibre compared to shorter ones, and higher rate of respiration which reduced shelf life after harvest. Hence, thick and short spears were more desirable according to literature. However, it was unclear at what height and thickness the textural quality would become undesirable from a consumer perspective, since there seems to be a market even for thin spears.
Agronomical factors such as plant age, root crown depth and density influences quality. Plants produce thinner spears as the plants ages if fern growth and carbohydrate accumulatio is not optimised. Spear diameter would increase with crown depth, spear diameter, while adding more plants per field area had an opposite effect. However, future weather patterns with increased precipitation during fall could require a shallower planting of crowns for optimal drainage, with the possible cost of reduced thickness. Meanwhile, an expected increase of hot summers and periods of drought could require producers to utilise field irrigation in the future, an uncommon practise in Sweden. Shoots need adequate moisture for optimal quality since this adds to spear weight, reduced wilting and contributes to textural tenderness.
Cold field temperatures would also increase the fiber to volume ration, adding to textural toughness, but shelf life as a function of respiration rate, wilting, and tip rot, was prolonged in spears grown during mild weather. Respiration and elongation rate accelerates as field temperature rises, and increases the occurrences of spears with feathered tips, while reducing textural toughness. Spears grown during warm weather are taller and thinner, which contributes to the faster loss of water and sugars, leading to less days of shelf life. Hence, a higher frequency of hot summers could lead to spears of poor visual quality and reduced shelf-life, requiring producers to better monitoring stalks on the field and harvest more often to prevent lanky shoots.