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  • Author or Editor: V. Slaćanac x
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Acidic and enzymatic coagulation of milk are complex processes which proceed in several phases and are dependent upon many different parameters. The formation of coagulum during lactic-acid fermentation is in fact acidic coagulation of milk. It occurs because of an increase in concentration of lactic acid, which causes a decrease in pH. Enzymatic coagulation of milk has been analytically described by means of mathematical models by many authors. Although enzymatic and acidic coagulation of milk do not proceed according to identical physical and chemical rules, it is possible to compare them kinetically. The aim of this paper was to combine the kinetics of enzymatic and acidic coagulation of milk and to mathematically present the changes that develop during lactic-acid fermentation of milk. The models presented in this paper enable a more complex mathematical analysis of the coagulation of the protein content of milk during lactic-acid fermentation. Application of the models enables the analysis and comparison of the kinetics of coagulation in different types of milk and various types of fermented dairy products manufactured with lactic acid bacteria. Mathematical combination of coagulation kinetics of the protein complex in milk with reological characteristics of the obtained fermented dairy products enables easier defining of parameters for lactic acid fermentation.

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This study was carried out to determine the intensity of production of acetic acid, short (SCFA) and medium (MCFA) chain fatty acids in cow and goat milk fermented by the use of Bifidobacterium longum Bb-46. Amounts of SCFA and MCFA in fermented goat and cow milk were determined by the use of GC/FID method. Concentration of acetic acid in the samples of fermented goat and cow milk were measured using GC/MS method. Furthermore, the growth rates of Bifidobacterium longum Bb-46 and its fermentation activity in goat and cow milk were also determined. Obtained results suggest higher metabolic activity of Bifidobacterium longum Bb-46 in goat than in cow milk. Bifidobacterium longum Bb-46 grew better in goat than in cow milk. Consequently, pH values decreased more rapidly during the fermentation of goat milk. Contents of all the examined SCFA and MCFA, as well as of acetic acid, increased more rapidly in goat milk during the whole fermentation process.

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The aim of this study was to determine the influence of goat’s milk fermented by Bifidobacterium longum Bb-46 on pathogenic Staphylococcus aureus strain, as well as to determine the differences of inhibitory potential between fermented goat’s and cow’s milk. The results showed significantly higher inhibitory effect of fermented goat’s milk on the growth of Staphylococcus aureus compared to that of fermented cow’s milk. Fermented goat’s milk inhibited the growth of Staphylococcus aureus during the whole fermentation period. In contrast to fermented goat’s milk, weaker inhibitory effect of fermented cow’s milk was observed only during the first phase of fermentation (incompletely fermented samples with higher pH values and lower number of viable cells of Bifidobacterium longum Bb-46). The obtained results suggested that there was no correlation between changes of pH or CFU of Bifidobacterium longum Bb-46 during fermentation and the inhibitory effect of fermented cow’s and goat’s milk. However, the results suggested some correlation between the inhibition of Staphylococcus aureus growth and the content of SCFA and MCFA in fermented cow’s milk. At the same time, considerably higher amounts of all examined SCFA and MCFA were produced in goat’s milk in all the phases of the fermentation process.

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The aim of this study was to determine the stimulatory effect of honey addition on fermentation activity of Lactobacillus casei Lc-01 in cow’s and goat’s milk. Two monofloral honey types, dark-coloured chestnut and light-coloured acacia honey were added to cow’s and goat’s milk before fermentation. Different mathematical and statistical models were used to describe the kinetics of fermentation in all analysed samples. The basic hypothesis of this study was that addition of honey could influence fermentation kinetics in both types of milk. Comprehensive kinetic analyses suggested complex interaction between all components in fermented milk samples. The results presented in this paper showed that addition of both types of honey had a stimulatory effect on the growth of Lactobacillus casei Lc-01 in cow’s and goat’s milk. Addition of acacia honey significantly stimulated (P<0.05) the growth of Lactobacillus casei Lc-01 in cow’s and goat’s milk. This resulted in higher number of Lactobacillus casei cells, as well as in lower pH values of the samples with addition of acacia honey. Furthermore, goat’s milk was fermented faster than cow’s milk. Calculated values of selected kinetic parameters showed that the critical period of fermentation kinetics, when influence of honey proved stimulatory, was between 10th and 20th hour of the fermentation.

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Acta Alimentaria
Authors:
P. Havas
,
Sz. Kun
,
G. Styevkó
,
V. Slačanac
,
J. Hardi
, and
J. Rezessy-Szabó

Consumers are becoming more interested in healthy nutrition. To meet consumer requirements, the possibility of the fruit and vegetable juice fermentation by bifidobacteria was investigated. Sour cherry, orange, carrot, and tomato juice was fermented with five Bifidobacterium strains (from human origin and starter culture). The tested strains have grown well in orange, carrot, and tomato juices. The B. longum Bb-46 strain demonstrated the best growth activities. It was found that ratio of the produced acetic and lactic acids are dependent on the Bifidobacterium strain rather than on the fermentation medium. The most intensive inhibition was observed against the Campylobacter jejuni strain. In course of the fermentation the antioxidant capacities slightly decreased, except when the orange juice was fermented with B. lactis Bb-12 and B. longum A4.8. The obtained results may contribute to the design of a novel functional food product.

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