Improving the texture and rheology of set and stirred kombucha fermented milk beverages by addition of transglutaminase

U radu je ispitana mogućnost proizvodnje fermentiranih mliječnih napitaka uz primjenu koncentriranog kombucha inokuluma i s dodatkom transglutaminaze (TG). Glavni ciljevi rada bili su ispitati utjecaj koncentriranog inokuluma kombuche i dodatka transglutaminaze na teksturalna, reološka i senzorska svojstva čvrstih i tekućih fermentiranih mliječnih napitaka. Rezultati pokazuju da dodatak transglutaminaze u mlijeko značajno utječe na teksturalna i reološka svojstva kombucha fermentiranih mliječnih napitaka. Čvrstoća i konzistencija kombucha fermentiranih mliječnih napitaka značajno je povećana primenom transglutaminaze u odnosu na kontrolni uzorak. Čvrsti uzorci s transglutaminazom imali su 90 % veću površinu histerezisne petlje u usporedbi s tekućim uzorcima, dok je površina histerezisne petlje tekućih uzoraka bez transglutaminaze bila oko 60 % manja u usporedbi s čvrstim uzorcima kombucha fermentiranih mliječnih proizvoda. Enzimski tretman mlijeka s transglutaminazom poboljšao je teksturalna i reološka svojstva, i senzorske karakteristike čvrstih i tekućih fermentiranih mliječnih napitaka dobivenih primjenom koncentriranog kombucha inokuluma.The possibilities of manufacturing fermented milk beverages by applying kombucha inoculum concentrated by evaporation and with addition of transglutaminase have been investigated. The main aims of this study were to investigate influence of concentrated kombucha inoculum and the addition of transglutaminase (TG) on textural, rheological and sensory properties of set and stirred fermented milk beverages. The results showed that the addition of transglutaminase had a great influence on textural characteristics and rheological properties of kombucha fermented milk beverages. Firmness and consistency of kombucha fermented milk products were significantly increased with the incorporation of TG compared to the control sample. Set samples with TG addition had approximately 90 % higher hysteresis loop area compared to stirred samples, while hysteresis loop area of stirred samples without TG was 60 % lower compared to set samples. The enzymatic treatment of milk with TG improved texture, rheology and sensorial characteristics of set and stirred fermented milk beverages obtained by concentrated kombucha inoculum

Ružička days : International conference 16th Ružička Days “Today Science – Tomorrow Industry” : Proceedings

Proceedings contains articles presented at Conference divided into sections: open lecture (1), chemical analysis and synthesis (3), chemical and biochemical engineering (8), food technology and biotechnology (8), medical chemistry and pharmacy (3), environmental protection (11) and meeting of young chemists (2)

Modeling and Optimization of Herb-Fortified Fresh Kombucha Cheese: An Artificial Neural Network Approach for Enhancing Quality Characteristics

In this study, an Artificial Neural Network (ANN) model is used to solve the complex task of producing fresh cheese with the desired quality parameters. The study focuses on kombucha fresh cheese samples fortified with ground wild thyme, supercritical fluid extract of wild thyme, ground sage and supercritical fluid extract of sage and optimizes the parameters of chemical composition, antioxidant potential and microbiological profile. The ANN models demonstrate robust generalization capabilities and accurately predict the observed results based on the input parameters. The optimal neural network model (MLP 6-10-16) with 10 neurons provides high r2 values (0.993 for training, 0.992 for testing, and 0.992 for validation cycles). The ANN model identified the optimal sample, a supercritical fluid extract of sage, on the 20th day of storage, showcasing specific favorable process parameters. These parameters encompass dry matter, fat, ash, proteins, water activity, pH, antioxidant potential (TP, DPPH, ABTS, FRAP), and microbiological profile. These findings offer valuable insights into producing fresh cheese efficiently with the desired quality attributes. Moreover, they highlight the effectiveness of the ANN model in optimizing diverse parameters for enhanced product development in the dairy industry

Homology modelling and docking analysis of L-lactate dehydrogenase from Streptococcus thermopilus

The aim of this research was to create a three-dimensional model of L-lactate dehydrogenase from the main yoghurt starter culture - Streptococcus thermopilus, to analyse its structural features and investigate substrate binding in the active site. NCBI BlastP was used against the Protein Data Bank database in order to identify the template for construction of homology models. Multiple sequence alignment was performed using the program MUSCULE within the UGENE 1.11.3 program. Homology models were constructed using the program Modeller v. 9.17. The obtained 3D model was verified by Ramachandran plots. Molecular docking simulations were performed using the program Surflex-Dock. The highest sequence similarity was observed with L-lactate dehydrogenase from Lactobacillus casei subsp. casei, with 69% identity. Therefore, its structure (PDB ID: 2ZQY:A) was selected as a modelling template for homology modelling. Active residues are by sequence similarity predicted: S. thermophilus - HIS181 and S. aureus - HIS179. Binding energy of pyruvate to L-lactate dehydrogenase of S. thermopilus was - 7.874 kcal/mol. Pyruvate in L-lactate dehydrogenase of S. thermopilus makes H bonds with catalytic HIS181 (1.9 Å), as well as with THR235 (3.6 Å). Although our results indicate similar position of substrates between L-lactate dehydrogenase of S. thermopilus and S. aureus, differences in substrate distances and binding energy values could influence the reaction rate. Based on these results, the L-lactate dehydrogenase model proposed here could be used as a guide for further research, such as transition states of the reaction through molecular dynamics. [Projekat Ministarstva nauke Republike Srbije, br. III 46009

Content of sugar, organic acids and ethanol in fermented milk beverages obtained with different types of kombucha inoculum

The aim of this study was to examine the influence of different types and concentration of kombucha inoculum on content of sugar, organic acids and ethanol in the fermented beverages produced from milk of 0.9% fat content. Three different kombucha inoculums, cultivated on black tea with addition of sucrose: standard inoculum - 10% (w/w) and 15% (w/w), concentrated by microfiltration- 10% (w/w) and 15% (w/w), and concentrated by evaporation - 1.5% (w/w) and 3.0% (w/w), were applied in the manufacture of fermented milk. Contents of lactose, galactose, glucose, fructose, organic acids, and ethanol in the kombuha fermented milk beverages were determined by the enzyme tests. It was found that the lactose content varied from 3.30 to 4.0 g/100g. All samples showed higher content glucose than fructose. The content of L-lactic acid in the samples ranged from 0.4 to 0.7 g/100g, while significantly lower level of D-lactic and acetic acid were determined in all samples of kombucha fermented milk (<0.06g/100g).[Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 46009

Kinetics of lactose fermentation in milk with kombucha starter

The aim of this research was to investigate the effect of new, non-conventional starter culture on the kinetics of the lactose transformation during milk fermentation by kombucha, at pH 5.8; 5.4; 5.1; 4.8; and 4.6, at two different temperatures 37 °C and 42 °C. Milk fermentation at 42 °C lasted significantly shorter (about 5 h, 30 min) compared to the fermentation at 37 °C. Changes of lactose concentration at the both temperatures are consisting of two retaining stages and very steep decline in–between. The analysis of the rate curves showed that the reaction rate passes through the maximum after 9 h, 30 min at 37 °C and after 4 h at 42 °C. The sigmoidal saturation curve indicates a complex kinetics of lactose fermentation by kombucha starter. Keywords: Kinetics, Kombucha, Lactose fermentation, Mil

Protein characterisation and antioxidant potential of fresh cheese obtained by kombucha inoculum

U ovom radu ispitani su proteinski profil, in vitro gastrointestinalna digestija i antioksidativni potencijal dva uzorka svježeg sira dobivenog korištenjem kombucha inokuluma i tradicionalne starter kulture. Utvrđena je značajna razlika u proteinskom profilu i biološkom potencijalu između uzoraka svježeg sira. Kombucha svježi sir sadržava veći udio proteina, pretežno frakcija kazeina (α-kazein i β-kazein) u odnosu na svježi sir koji je dobiven tradicionalnom starter kulturom. Tijekom gastrointestinalne digestije, frakcije kazeina brže se razgrađuju pepsinom u uzorku svježeg sira s tradicionalnim starter kulturom nego u kombucha svježem siru. Nakon gastrointestinalne digestije (s pepsinom i pankreatinom), u uzorku kombucha svježeg sira utvrđena je znatno veća količina topljivih proteinskih frakcija i viši stupanj hidrolize u odnosu na uzorak dobiven tradicionalnom starter kulturom. Hidrolizati sira dobiveni inokulumom kombuche sadržavali su veće koncentracije fenola i imali veću sposobnost uklanjanja antiradikala od hidrolizata svježeg sira proizvedenog s tradicionalnom starter kulturom. Rezultati pokazuju da primjena inokuluma kombuche doprinosi poboljšanju biološkog potencijala svježeg sira.Protein profile, in vitro gastrointestinal digestion and antioxidant potential of two fresh cheese samples obtained by kombucha inoculum and traditional starter culture have been investigated in this study. There is a significant difference in protein profile and bioactive potential between fresh cheese samples. Kombucha fresh cheese contains higher proportion of protein, predominantly the casein fractions (α-casein and β-casein) compared to fresh cheese obtained by traditional culture. After gastrointestinal digestion (with pepsin and pancreatin), significantly higher amount of soluble protein and higher degree of hydrolyses were measured in kombucha fresh cheese sample than sample obtained by traditional culture. During gastrointestinal digestion, for fresh cheese with traditional starter both fractions of casein are degraded more rapidly by pepsin than in kombucha fresh cheese. The hydrolysates of cheese obtained by kombucha inoculum showed higher phenolic content and higher antiradical scavenging abilities than hydrolysates of fresh cheese produced with traditional starter. These results suggest that kombucha inoculum contributes to improvement of product’s bioactive potential

The effect of processing parameters on the structure of fermented milk products with transglutaminase addition

This study is concerned with the effect of concentration of transglutaminase (TG), content of milk fat and starter culture type (probiotic and kombucha) on the structure of fermented milk products. The application of TG significantly improved textural characteristics of the fermented milk products. The firmness of the samples produced from milk with 0.1g100g-1 and 0.9g100g-1 fat content with probiotic starter were by 33% and 17.6% higher, respectively, compared to the control samples. During ten days of storage, the value of the hysteresis loop area of all samples produced from milk with 0.9g100g-1 fat content with TG addition, decreased by 14%. [Projekat Ministarstva nauke Republike Srbije, br. 46009

Methylene blue removal by adsorption on unmodified and modified wood sawdust

Adsorption, as an easy and effective technique, is widely used to remove a large number of dyes from aqueous solutions. Activated carbon is the most desirable adsorbent, but due to its high cost, its use is limited. Proving the possibility of adsorption and its efficiency performed on cheap adsorbents is a great challenge and interest of many researchers in the past few decades. In this paper, unmodified (P) and modified sawdust obtained in two ways (HCl treatment and NaOH treatment), labeled as PHCl and PNaOH, are used for the removal of the methylene blue dye. Adsorption experiments showed that the optimal time for adsorption is different, for the sample PNaOH – 30 min, for the sample P – 45 min, and for the sample PHCl – 60 min. By applying nonlinear kinetic models to the experimentally obtained data, it was found that the best model that describes this adsorption is pseudo-second-order model. By examining the effect of pH values on adsorption, different results were obtained (for samples P and PHCl the optimal pH value is pH=11, the PNaOH sample is effective in a wider range of pH values). The analysis of the effect adsorbent dose on adsorption process showed that the efficiency of dye removal decreases with increasing mass of adsorbents. The obtained values of the coefficient of determination in Freundlich's model for samples of unmodified (P) and modified sawdust (PNaOH) indicate that the adsorption of the methylene blue dye is multilayer type adsorption. For the PHCl sample, neither the Langmuir nor Freundlich model adequately described MB dye adsorption

Influence of fat content and starter cultures on the quality of fermented dairy products

The objective of this study was to investigate the effect of fat content and type of the starter culture (traditional or probiotic) on physico-chemical quality, rheological and textural characteristics of the fermented dairy products during 14 days of storage. Seven different fermented dairy products of two different groups: stirred and set yoghurts were used in this study. The rheological and textural characteristics of the analyzed type of fermented dairy products after the production and during storage are dependent on the chemical composition, particularly fat content. [Projekat Ministarstva nauke Republike Srbije, br. III 46009