Determination of N/Protein in Probiotic Drink by Kjeldahl Method (CAT#: STEM-EA-0046-ZJF)

Introduction

A probiotic is a live microbial food ingredient that beneficially affects the host through its effects in the intestinal trac t. Probiotics are already widely used to prepare fermented dairy products that are becoming more and more popular in Europe, Japan and USA. These products favorably influence digestive functions and colonic flora. After passage through the stomach and the small intestine, some probiotics survive and become established transiently in the large bowel. The bacterial genera most often used as probiotics are lactobacilli and bifidobacteria, almost exclusively consumed as fermented dairy products such as yogurt.
Kjeldahl is nowadays the most used method for determining nitrogen and protein contents in foods and feeds , thanks to the high level of precision and reproducibility and to its simple application. The modern Kjeldahl method consists in a procedure of catalytically supported mineralization of organic material in a boiling mixture of sulfuric acid and sulfate salt at with digestion block temperature at 400 °C. During the process the organically bonded nitrogen is converted into ammonium sulfate. Alkalizing the digested solution liberates ammonia which is quantitatively steam distilled and determined by titration.