Abstract:

Fructans occupy more than 75% of the dry weight of garlic (Allium sativum L.). Understanding of the enzymologic characteristics of garlic fructan exohydrolase (FEH) provides the theoretical basis on inhibition of garlic germination and mass production of high quality garlic fructans. In this experiment, localization of FEH was done by ammonium sulfate precipitation, its enzymatic degradation products were studied by TLC and ion chromatography, enzyme activity was determined by calculating the variance of reducing sugar via DNS assay. Further study of the locus of action of FEH and the effects of temperature, pH level, ionic strength, and substrate concentration on FEH activity was also included. The results showed that FEH was present in the fraction of 0－20% saturated ammonium sulphate. Through the analysis of enzymatic degradations, FEH was confirmed as an excision enzyme. The optimal reaction temperature, pH, ionic strength and substrate concentration were 45 ℃, pH 5.5, 1.5 mol/L and 4 mg/mL, respectively. These investigations demonstrated that the exohydrolase in garlic could impact the quality of garlic processed products and polysaccharide metabolization in the fresh garlic during its storage.

Key words: fructan, fructan exohydrolase, enzymologic characteristics, Allium sativum L.