Structural and Mechanical Characteristics of Fermented Whipped Dairy Products
Authors: Podlegaeva Tatiana , Kostina Natalya 
Published: March 2020

Introduction. Whipped dairy products can be used both as finished and semi-finished products in confectionery industry. Therefore, this sphere constantly requires new technologies. A wide range of additives, stabilizers, and structure-forming agents make it possible to get products with programmed sensory, structural, and mechanical properties. Enzymatic processing of milk base is one of the modern directions in the development of whipping process, as it requires no artificial components. Enzyme preparations of plant and microbial origin were developed to satisfy the needs of the increasing production demand and to compensate for the acute shortage of animal rennet. These enzymes have a high proteolytic activity and exhibit good technological properties in dairy industry. The research objective was to study the fermentation process with preparations of different origin and optimize the proteolysis process to obtain a milk base with a high foaming capacity and maximal stability.

Study objects and methods. The research featured samples of fermented reduced skim milk. The following enzymes were selected for enzymatic hydrolysis: animal origin – rennet-beef enzyme SG-50 (Russia), chicken-beef enzyme KG-50 (Russia), pepsin (Russia); microbial nature – Fromase 750 (France), Pronase E (Russia); recombinant chymosin-preparation CHY-MAX M (Denmark). The fermented systems were tested for foaming ability, foam stability, relative content of free amino acids, and the diameter of casein micelles during hydrolysis by the ratio of the height of the foam column to the initial volume. The relative content of free amino acids was determined using the method of formal titration. The diameter of casein micelles during hydrolysis was determined by dynamic light scattering using a particle size analyzer in low-volume plastic cuvettes. These indicators were determined after inactivation of enzymes by pasteurization at 90–92°C for 3–5 sec.

Results and discussion. Enzyme preparations of various natures were added to milk. The temperature and duration were measured as rational parameters of fermentation. After inactivation of the enzymes by pasteurization method, the foaming capacity, foam stability, and the relative content of free amino acids were determined every 30 minutes after application of the preparation. The greatest foaming properties (800%) were observed in the milk base fermented with the recombinant enzyme CHY-MAX M. However, the use of this preparation in commercial production was found undesirable due to the high activity of the enzyme and the resulting complexity of the control process. The lowest foaming ability was observed in the milk sample fermented with preparations of animal origin – SG-50, KG-50, and pepsin. The optimal foaming capacity and stable whipped mass were registered in the samples hydrolyzed with microbial preparations Fromase and Pronase. Under certain rational parameters, the foaming capacity of milk was 740% and 700%, respectively, while the stability was 80%.

Conclusion. The research featured a comparative analysis of the foaming capacity and stability of reduced skim milk foam obtained using preparations of animal and microbial origin. The enzymes of the microbial group showed the best results for the enzymatic hydrolysis of proteins in reduced milk.