Assessment of diastatic, proteolytic and lipolytic activities of yellow and brown varieties of Cyperus esculentus (Tigernuts) extracts

Analyses of two varieties of Cyperus esculentus (tigernuts) showed that the 100-nutweight of the yellow variety (49.1 g) was higher than the brown variety (14.8 g). The percentage of moisture contents for the yellow and brown varieties were 13.50% and 5.78% respectively. Treatment of soluble starch with tigernut extracts showed that starch hydrolysis occurred. The time for diastatic activity (α- + β- + γ-amylase activities) to completely hydrolyse starch was generally longer than either α- or β-amylase activity at 50℃. Periods and temperatures for complete starch hydrolysis by α-, β- and γ-amylases were virtually the same in the two tigernut extracts. The shortest time for complete starch hydrolyses by diastatic activity occurred at 50℃ and 65℃ for both yellow and brown varieties respectively. Least period for starch hydrolysis by α-amylase activity in both varieties occurred at 50℃, while the least time for β-amylase and γ-amylase activities in both tigernut varieties occurred at 65℃. Quantitative determination of amylolytic enzymes of yellow tigernut extract (TNE) on ‘dry basis’ showed that diastatic activity (183.6º) > α-amylase activity (167.3º) > β-amylase activity (119.8º) > γ-amylase activity (47.5º). Similarly, brown TNE amylolytic enzymes on ‘dry basis’ showed that diastatic activity (175.8º) > α-amylase activity (140.8º) > β-amylase activity (94.9º) > γ-amylase activity (49.6º). The α-amylase activity in yellow tigernut variety was 1.4-fold that of βamylase activity but about 1.5-fold in brown variety. However, α-amylase activity (dry basis) was about 3.5-fold that of γ-amylase in yellow variety but 2.8-fold in the brown variety. Extracts from both tigernut varieties also showed proteolytic and lipolytic activities at about 30℃. Evidently, tigernuts contain various endogenous hydrolytic enzymes and the sweetness of tigernut is invariably due to sugars produced from amylase hydrolysis of innate starch.