Technology of Milk and Dairy products

A rapid and sensitive spectrophotometric method for the quantitative determination of inulin and fructooligosacharides in lactic acid fermented dairy products has been developed. The method was based on the familiar Seliwanoff reaction for detection of ketoses with resorcinol in hydrochloric acid media. The standard curve was constructed by using fructose as a standard. The tested spectrophotometric method has been characterized with good linearity (R2=0.997) in the fructose concentration range 0.5-20 μg/ml. The presence of galactose and lactose in the analyzed samples did not interfere in the determination of inulin. The sample preparation procedure included hot water extraction, purification by Carrez solutions and subsequent spectrophotometric determination at 480 nm. The developed method showed very good precision: repeatability (RSD=6%) and reproducibility (RSD=10%). The obtained results demonstrated that the spectrophotometric method is less time-consuming, cheap, reproducible and suitable for routine laboratory analysis.

Fermented dairy products from cow milk with addition of lactulose are produced, which have well known health characteristics. The dynamic of the process of lactose fermentation is investigated with addition of different amount of the disaccharide - 1, 2, and 3 % and a control sample. It is found that the dynamic of biochemical transformation of lactose to lactic acid and the coagulation of the milk in the versions with different amounts of added lactulose are similar to the control sample. The organoleptic profile of the obtained products, show that they are characterized by indicators - texture, color, taste and aroma typical for this group of products.

Abstract Ultrasonic fractional extraction of fructooligosaccharides and inulin from Jerusalem artichoke tubers has been carried out. The following conditions as the type of the used solvent- n-propanol, 95% (v/v) ethanol and distilled water and the duration of the extraction process have been varied. The contents of sugars and fructans in the obtained extracts were determinated by spectrophotometric method based on resorcinol reaction and by TLC analysis. The greatest amounts of fructooligosaccharides and inulin have been extracted by distilled water (46 g/100g d.w.), as each ultrasonic extraction was carried out in triplicate for 30 min. The best solvent used for the separation of a particular fraction fructooligosaccharides consisting of kestose, nystose and fructofuranosylnystose was n-propanol.