Influence of water soaking of mustard cake on glucosinolate hydrolysis

The soaking of mustard cake in water prior to feeding is a traditional technology being practiced by Indian farmers to improve its palatability. The degree to which the glucosinolate moiety of mustard cake is hydrolysed is dependent on the soaking period. To understand the utility of this traditional technology, mustard cake was soaked with water (1:5 w/v) for 0, 2, 4, 6 and 8 h at 37 °C. The initial amount of total glucosinolates (55 μmol/g) was reduced by 76% after 8 h of soaking. Gluconapin was the major glucosinolate in mustard cake, while sinigrin and pentenyl were in minor quantities in molar ratios of 77:14:9. Gluconapin degraded linearly with time and 82% degradation was recorded after 8 h of soaking. Butenyl isothiocyanate (BIT) was the major degradation product which increased linearly with time (1.38, 2.41, 3.10 and 4.23 μmol/g slurry at 2, 4, 6 and 8 h, respectively), whereas allyl isothiocyanate was detected only in minor concentrations. These results indicate that mustard cake may be soaked in water for 8 h for substantial hydrolysis of its glucosinolates.