Öz
Objective: True protein (TP) does not contain non-protein nitrogenous substances (NPN), unlike crude protein (CP). Therefore, it is not affected by NPN adulterations as much as crude protein. In this study, determining the amount of TP in milk, milk powder (MP) and whey powder (WP) samples and the possibility of using this parameter to prevent NPN adulterations was investigated.
Materials and Methods: Method validation/modifications were made for GP analysis using protein and NPN content specific reference material and subsequently infrared device calibrations were performed and samples were analyzed. In the second stage of the study, the effectiveness of the true protein value in NPN adulterances was evaluated by adding urea to MP in different proportions.
Results: Average CP, TP amounts and TP/CP and NPN/CP ratios of analyzed 100 raw milk, 40 MP and 15 high proteinacious and 5 proteinacious WP were 3,25±0,23%, 3,06±0,01%, 94,08%, 5,92%; 32,51±2,25%, 30,35±0,06%, 93,36%, 6,64%; 12,18±0,71%, 8,29±0,04%, 67,84%, 32,16% and 8,05±0,67%, 6,11±0,03%, 75,37%, 24,63% respectively.
In the performed adulteration study it was determined that the amount of CP increased by 35,59, 109,95, 221,09% due to the increased amount of urea (5, 10, 20% respectively) while the amount of true protein decreased by.
Conclusions: As a result, putting the true protein value in the label information of milk and dairy products may contribute to the prevention of NPN adulterations. However, the performance of the method on known NPN substances should be evaluated separately.