Test Method Test Item Measurement Remarks  References Titrimetric Method   Soybean oil meal Volume of NaOH required to finish the titration * Application: In mixed-feed industry to identify the low concentration of urease in soybean oil meal (when urea and soybean oil meal are combined in cattle feeds)  [70] Soybean meals Volume of NaOH required to finish the titration * Application: To determine urease in soybean meals of high activity  [121] * Recommended for all highly active meals Jack Bean Color change of the p-Nitrophenol indicator from yellow to colorless during the titration *Limitation: This is not for determining the activity of urease, from Bacillus pasteurii, U7127  [122]  *Urease activity is reported as Units/g solid. Spectrophotometric Stop Rate Determination - Absorbance is taken at 480 nm wavelength using a spectrophotometer *Urease activity is reported as Units/g enzyme (one unit will liberate 1.0 mmole of NH3 from urea per minute at pH 8.2 at 30 °C.)  [123] *Nessler's reagent is used to determine NH3 generated from hydrolysis of Urea Caskey-Knapp method Soybean meal color change due to variation in pH *pH indicator. phenol red solution (If sufficient urease is present color change to deep red)  [124] *Application: Food processing Industry to detect inadequately heated soybean oil meal *Limitation: Cannot indicate excessive heat treatment Modified Caskey-Knapp method /PH Change method (potenciometric method) Soybean oil meal pH value using pH meter with glass electrode *Application: In food processing Industry (detecting inadequately heated soybean oil meal)  [125]   Soybean meal and byproducts pH value using pH meter with glass electrode *Application: In Soybean Industry (Detecting present in soybean products like soy-bean meals, soy flour, and mill feeds)  [126]   Soybean meal and byproducts pH value using pH meter with glass electrode *Application: soybean Industry (Detecting urease present in Soybean meal and its by-products)  [127] Conductimetric Method Soybean Resistance in ohms (specific conductance is reciprocal ohms) Application: To study urease isolated from soybeans  [70] Wiffin's conductimtric Method Bacteria (proteus vulgaris and sporosacina pasteuii) Conductivity Urease activity is reported as Mm urea hydrolysed min-1.  [71]   Bacteria (Sporosrcina pasteurii) Conductivity    [87]   Soybean meal The absorbance (Optical density) is measured at 430 m Wavelength using the spectrometer *Application: To determine urease activity of soybean meal  [128] *Urease activity was reported as mg/l urea decomposed. (An unit of urease activity is defined as one milligram per liter of urea decomposed)   Plant seeds Color change due to variation in pH *pH indicator red cabbage extract (At pH 7, the solution is violet/blue and in the acidic range it turns red and in alkaline range it turns green)  [129,130] *1% or 2%phenolphfhalein solution and bromothymol blue are alternatives for pH indicator (it turns from yellow to blue in pH 7.6) colorimetric Method Soybean Absorbance is taken at 405 nm wavelength using a spectrometer *Nessler's reagent is used to determine NH3 generated from hydrolysis of Urea  [131] *One unit of urease activity is defined as the amount of enzyme required to liberated 1.0 M of NH3, from urea per min at pH 8.0 and temperature 30 °C)   Jack Bean meal Absorbance (optical density) is measured at 630 nm wavelength, using the spectrometer (Phenol Hypochloride solution was added to develop color)  -  [132]   Soil Absorbance (optical density) is measured at 690 nm wavelength, using the spectrophotometer *Urease activity is expressed as gN hydrolyzed/g dry soil per 2 hour at 37 °C.  [133]   Soil Absorbance (optical density) is measured at 690 nm wavelength, using the spectrophotometer *Urease activity is calculated as mole of ammonium released per hour per gram of soil.  [134]   Pararhodobacter sp. Color change due to variation in PH *pH indicator: Cresol red solution (yellow to purple has been observed from pH 7.2 to pH 8.8)  [135] *Medium used to isolate microorganism in ZoBell2216E medium   Bacteria  - *Christensen's urea medium was used  [136]   Bacteria Absorbance (optical density) is measured at 430 nm and 560 nm wavelengths, using the spectrophotometer *Urease activity as Units/ml enzyme (one unit of urease activity corresponds to the amount of enzyme that hydrolyzes 1mM of urea per minute)  [137]

Table 2: Methods for evaluating urease activity.