Upgrading the technology of functional dairy products by means of fermentation process ultrasonic intensification

B. Shershenkov* and E. Suchkova

ITMO University, Institute of Refrigeration and Biotechnologies, Department of Technology of Milk and Food Biotechnology, Lomonosov str., 9, 191002, St. Petersburg, Russia; *Correspondence: boris.shershenkov@list.ru

Abstract:

Intensification of milk fermentation without negative influence on product quality is a priority research direction in dairy industry. One of the perspective tools for solving this problem is usage of ultrasound. Careful selection of ultrasonic treatment regimens allows to activate lactic-acid bacteria metabolic activity and to improve the efficiency of dairy production. A number of cultivations were carried out for ultrasonic processing effect estimation on Lactococcus mixed culture, Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus symbiotic cultures that are often used for dairy fermentation. Milk with added starter culture was treated with ultrasound by means of ultrasonic homogenizer at a frequency of about 30 kHz. Processing duration varied from 1 to 3 minutes and ultrasound power varied from 2 to 8 W. Ultrasonication regimens of fermenting milk allowed accelerating of fermentative process by 10% and improving the quality of final product.

Key words:

The Effect of Milk Heat Treatment on the Growth Characteristics of Lactic Acid Bacteria

I. Stulova 1, 2 , N. Kabanova 1, 2, T. Kriščiunaite 1, 2, T.-M. Laht 1, 2 and R. Vilu 1,2

1 Tallinn University of Technology, Ehitajate tee 5, 19086, Tallinn, Estonia 2 Competence Center of Food and Fermentation Technologies (CCFFT), Akadeemia tee 15B, 12618, Tallinn, Estonia; e-mails: irina.stulova@tftak.eu; natalja@tftak.eu; tiina@tftak.eu; tiiu@tftak.eu; raivo@tftak.eu

Abstract:

The ability to growth in milk is an important feature for lactic acid bacteria (LAB) used as starters for fermented milk products. Several decades ago the results of the studies varied widely: some of them showed that LAB grew better in raw milk and others demonstrated improved growth of the bacteria in heat-treated milk (Foster et al., 1952). The effectiveness of heat treatment of milk as a tool for modifying the functional properties of protein components has been extensively documented in the literature (Raikos, 2010), but the information on the influence of heat treatment of milk on the growth of LAB is not exhaustive. Peculiarities of growth of Streptococcus thermophilus ST12 and Lactobacillus paracasei S1R1 were studied using isothermal batch microcalorimeter TAMIII. Bacterial growth was monitored in pasteurized and ultra-high temperature (UHT) treated milk with different fat content, and also in reconstituted skim milk (RSM) prepared from low-heat skim milk powder (LHSMP). Heat produced during different growth stages (Qtot, Qexp), maximal specific growth rate (μmax) and lag–phase (λ) duration were determined by processing calorimetric curves, and detailed analysis of growth of the bacteria in differently pretreated milks were carried out on the basis of these data. The results of the experiments showed that primarily heat treatment and, to a minor extent, fat content of milk influenced the growth parameters of both bacterial strains, especially Lb. paracasei, growth of which was almost completely inhibited in UHT milk.

Key words:

bacterial growth, Lactobacillus paracasei, microcalorimetry, milk treatment, Streptococcus thermophilus