Effect of Drying Temperature and Time on Alpha-Amylase, Beta-Amylase, Limit Dextrinase Activities and Dimethyl Sulphide Level of Teff (Eragrostis tef) Malt

Abstract

Teff is a gluten-free cereal with attractive nutritional profile. This research was aimed to study the influence of kilning on the enzyme activities and dimethyl sulphide (DMS) level of DZ-Cr-387 teff variety and suggest a kilning condition that yields teff malt with low DMS with no or little damage on its enzyme activities. The malts were dried using isothermal conditions at 30, 40, 50, 60 and 70 °C for 40 h with sampling in certain time interval. To set up kilning program, two temperature regimens 18 h at 30 °C + 1h at 60 °C + 3 or 5 h at 65 °C (R1) and 18 h at 30 °C + 1 h at 60 °C + 3 or 5 h at 80 °C (R2) were selected. Results from isothermal kilning indicated that enzyme activities, DMS and moisture contents were affected (P < 0.05) by time and temperature. The values of α-amylase, β-amylase, limit dextrinase activities and DMS content while using the first regimen (R1) with 3 h curing at 65 °C were 68 U/g, 440 U/g, 1,072 U/kg and 3.3 mg/kg, respectively. Whereas in the second regimen with 3 h curing at 80 °C, the values were 42 U/g, 406 U/g, 736 U/kg and 2.15 mg/kg, respectively. Prolonged curing in both kilning regimens caused an adverse effect on the amylolytic enzyme activities. R1 with shorter curing time is considered to be the best condition in preserving enzymes. The enzyme activities and DMS level show that teff can be an alternative raw material for production of gluten-free malt.