Blanching effect on the quality of frozen asparagus spears

Abstract

Asparagus (Asparagus officinalis L.) is a healthy vegetable, however it is perishable under conventional conditions (usually from three to five days). Asparagus spears are influenced by moisture, temperature, light, air, enzymes and microorganisms which present in them. These factors quickly change chemical composition and properties of spears, and they need to be quickly realized. Freezing is one of the best and most reliable ways to protect vegetables from deterioration. Freezing preserves the nutritional value and quality of perishable vegetables. It effectively inhibits the effects of microorganisms, chemical and biochemical processes, oxygen, heat and light. The experiment was carried out in 2016 at the Laboratory of Food Raw Materials, Agronomical and Zootechnical Research of Aleksandras Stulginskis University. The aim of the research: to determine the effect of blanching on the quality of frozen asparagus spears. The object of the research is the spears of asparagus hybrid varieties ‘Avalim’ and ‘Gijnlim’. The yield of spears for the study was harvested on 19th of May. The chemical composition of non-blanched and blanched spears stored for four weeks in a freezer (-18°C) has been determined. Standard methods have been applied to determine the quantities of vitamin C, dry matter, fibre, green ash, proteins, potassium, and nitrates. The blanching has affected the quantities of chemical substances tested in frozen asparagus spears. The highest amounts of vitamin C, protein and potassium and lower nitrate levels were found in blanched frozen asparagus spears, while higher amounts of dry matter, fibre, and green ash were detected in non-blanched frozen spears. Higher contents of dry matter, protein and potassium were determined in the variety ‘Avalim’ spears. There were lower nitrate levels were detected as well. Therefore, spears of the variety ‘Gijnlim’ contained higher amounts of vitamin C, fibre and green ash.