Green tea and its constituents are known for a wide range of health-promoting properties. They may exert antimicrobial action but without altering lactic acid bacteria. The aim of the present study was to estimate the effect of green tea addition on the selected properties of probiotic milks. Bioyogurts (fermented with ABT-1 coculture of Streptococcus thermophilus, Lactobacillus acidophilus LA-5, Bifidobacterium animalis subsp. lactis BB-12) and acidophilus milks (fermented with pure L. acidophilus LA-5 culture) with addition of 0, 5, 10, or 15% (v/v) green tea infusion (GTI) were produced and analyzed for the antioxidant capacity by the “diphenyl picrylhydrazyl” (DPPH) and “ferric-reducing antioxidant power” (FRAP) methods, acidity, the count of starter bacteria, and sensory properties at the 1st, 7th, 14th, and 21st day of cold storage. The 15% addition of GTI to the acidophilus milk significantly reduced the lactic acid production during the whole study. The GTI had no impact on the level of S. thermophilus and B. lactis BB-12 in bioyogurts, and its effect on the count of L. acidophilus LA-5 depended on the concentration and probiotic milk type. GTI similarly and in a dose-dependent manner enhanced the antioxidant capacity of both milk types. There were no significant differences between the sensory notes received for bioyogurts, whereas acidophilus milks with tea were less appreciated by the panelists. In conclusion, green tea could be successfully used as a functional additive for selected probiotic milks enhancing their health benefits, but the proper selection of tea additive and starter culture is recommended.

Elderberries, sea buckthorn, and sloe berries are fruits of wild-grown bushes, valued in folk medicine for their health-promoting properties but still rarely applied in food. The aim of the present study was to produce probiotic yoghurts with a 10% addition of sweetened purees prepared from elderberries (EPY), sea buckthorn (SBPY), and sloe berries (SPY) and to assess their chemical composition, acidity, content of polyphenols and anthocyanins, ferric reducing antioxidant power (FRAP) and antiradical power (ARP), level of starter microbiota, concentration of acetaldehyde and diacetyl, syneresis, instrumentally measured color and texture parameters, and sensory acceptance. The results were compared to those obtained for plain probiotic yoghurt (PPY) and the changes tracked during 1 month of cold storage at 2 week intervals. The addition of elderberry and sloe berries significantly increased the antioxidant capacity of probiotic yoghurts, probably due to a high content of polyphenols, especially anthocyanins. However, anthocyanins were more stable in the EPY when compared to the SPY. All yoghurt treatments were characterized by good sensory quality and viability of starter microorganisms, including probiotic strains during cold storage. Elderberries promoted the evolution of diacetyl in yoghurts during storage and, together with sloe berries, produced increased syneresis and the greatest changes in color profile compared to PPY.

The present research was established to study the effect of green tea and Pu-erh tea (PT) additives on the mechanical and hydration properties of yogurt gels using a combination of nuclear magnetic resonance, rheological, and textural studies. Tea infusions (0-15 mL/100 mL) were added to batch milk before fermentation with yogurt culture. Obtained dairy products were analyzed for the water mobility and organization, viscosity, and texture profile. Results of the rheological and nuclear magnetic resonance studies suggested that stabilization of the yogurt gel structure was achieved upon supplementation with tea infusions. Generally, green tea fortification produced yogurts with more consolidated gel structure, tighter interacting water, and less susceptibility to shearing and temperature changes than PT treatments. In contrast, PT yogurts were more viscous and characterized by 8 to 17% lower hardness values. This knowledge can be useful for developing novel dairy products with desired structure and consistency.

Free radicals are connected with the increased risk of certain diseases, especially cancers. There is some scientific evidence that antioxidant-rich diet may inhibit the negative impact of free radicals. The aim of the present study was to analyse the antioxidant capacity of the selected commercial natural and flavoured fermented milks offered in Poland, derived from different producers. The following commercially available natural fermented milks: 12 yoghurts, 12 kefirs, 2 butter milks, 2 cultured milks, Turkish yoghurt drink (ayran) and the following flavoured fermented milks: 22 yoghurts, 2 acidophillus milks, 2 kefirs, butter milk and vegetable flavoured fermented milk were analysed for their antioxidant potential. The antioxidant capacity was assessed, in two replicates and twice for each product, by means of ferric reducing antioxidant power (FRAP) and DPPH radical scavenging ability (expressed as ARP - anti radical power) methods. Among all analysed plain products, yoghurts and kefirs were characterised by the highest antioxidant activity. The presence of probiotic Lactobacillus casei strains in the product positively affected both FRAP and ARP values. Antioxidant capacity of the flavoured fermented milks was primarily affected by the type and quality (e.g. fruit concentration) of the added flavouring preparation. The most valuable regarding the estimated parameters were chocolate, coffee, grapefruit with green tea extract as well as bilberry, forest fruits, strawberry and cherry with blackcurrant fillings. Protein content, inclusion of probiotic microflora as well as type and quality of flavouring preparations are the main factors affecting antioxidant properties of fermented milks.