Abstract
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.
Highlights
Yoghurt is the most popular fermented milk product, consumed for its taste and for its nutritional and health-promoting properties
The analyzed fruit purees contained flavonoids; myricetin was detected in sea buckthorn and sloe, whereas rutin and quercetin were present in elderberry puree
The content of anthocyanins in sea buckthorn was very low compared to other applied fruits and did not bring any difference when SBPY was compared to the plain probiotic yoghurt (PPY) in terms of total monomeric anthocyanin content (TMAC); on the other hand, sea buckthorn added great value to yoghurts with respect to total phenolic content (TPC), phenolic acids, epicatechin, and myricetin. This could have been due to too small an addition of fruit puree (10% of fruit puree equal to 7% of berries) or the methods used for the evaluation of the antioxidant capacity. This observation is consistent with the results reported by Najgebauer-Lejko and Sady [27] performed on commercial yoghurt samples, which demonstrated that yoghurts with bluish-purple and red berries were characterized by higher ferric reducing antioxidant power (FRAP) and antiradical power (ARP) values than the respective yoghurts with light-colored fruits
Summary
Yoghurt is the most popular fermented milk product, consumed for its taste and for its nutritional and health-promoting properties. It is produced from a milk base with standardized fat and total solid content which is homogenized, pasteurized, cooled, and inoculated with two starter bacteria, i.e., Streptococcus thermophilus and Lactobacillus delbrueckii ssp. About 4.5 cups with yoghurt are transferred to refrigerated storage after reaching the desired pH, or the yoghurt gel from a vat is stirred, cooled to about 20 ◦C, and mixed with flavoring (e.g., fruit) preparation before cold storage [1]. Elderberry, is added to yoghurt, but only in small concentrations, in order to enhance the dark reddish-violet color of, e.g., blueberry or forest fruit yoghurt, not as flavoring or a bioactive ingredient itself. Due to a high content of dietary phytochemicals, as well as antioxidant, antibacterial, antiviral, immunostimulating, and antiallergic properties, both elderberries and elderflowers have been used for centuries in food production and in folk medicine to treat different ailments [10]
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