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Scleroglucan as Structure Forming Agent of Low-Fat Yogurt: Effects on Functional Properties, Bacterial Activity and Sensory Profile
Background: scleroglucan, an extracellular polysaccharide with gel-forming, thickening, and stabilizing properties, was used as a structure-forming agent in low-fat yogurt formulations. The aim of this study was to evaluate its influence on the fermentation process and the physicochemical, rheological, textural, microstructural, and sensory properties of the yogurts. Methods: control samples were formulated with the addition of skim milk powder (SMP), whereas experimental yogurts contained scleroglucan at concentrations of 0.25%, 0.5%, and 1.0% (w/w). The fermentation kinetics, acidity, color, syneresis, rheological behavior, texture profile, microstructure, and volatile compounds were analyzed during storage. Results: the results showed that scleroglucan slowed acidification and increased the apparent viscosity, yield stress, and firmness of yogurts, while completely eliminating syneresis. Scleroglucan also modified the volatile profile by decreasing acetaldehyde and increasing 2,3-pentanedione levels during storage. The survival of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus was not affected. Conclusions: the yogurt containing 1.0% scleroglucan was rated highest in overall acceptability. These findings demonstrate that scleroglucan can serve as a natural, clean-label stabilizer and an alternative to skim milk powder in low-fat set-style yogurts.
The Effect of Essential Oils on the Survival of Bifidobacterium in In Vitro Conditions and in Fermented Cream
Essential oils derived from plant materials are a mixture of compounds that exhibit antibacterial properties. Due to their distinct aroma, they also serve as a desirable natural additive for various food products, including dairy products. In this study, the essential oils of lemon peels, clove buds, and juniper berries were obtained by steam distillation and characterized using gas chromatography–mass spectrometry to determine their chemical compositions and effects on the viability of seven Bifidobacterium strains. Furthermore, the effect of essential oils on the viability of Bifidobacterium animalis subsp. lactis Bb-12 was investigated in cream samples during fermentation and after storage for 21 days at 6 °C. The fatty acid composition of fat extracted from essential oils containing sour cream samples and the volatile aroma compound profile of the sour cream samples were also determined chromatographically. Among the 120 compounds identified, monoterpene hydrocarbons were dominant in the essential oils of lemon peels (limonene and γ-terpinene) and juniper berries (sabinene and β-myrcene), while eugenol and eugenol acetate were abundant in the essential oil of clove buds. In addition to these compounds, butanoic and acetic acids were found in the tested sour cream samples. In turn, fat extracted from these samples was rich in saturated fatty acids, mainly palmitic acid. Among the tested strains of the genus Bifidobacterium, B. animalis subsp. lactis Bb-12 was the most sensitive to the essential oils of clove and juniper, as indicated by the larger growth inhibition zones. However, both the concentration and type of essential oils used had no effect on the number of cells of this strain present in the cream samples immediately after fermentation and after its 21-day storage, which suggests that the tested essential oils could be a natural additive to dairy products.
The Combined Effect of Lactic Acid Bacteria and Galactomyces geotrichum Fermentation on the Aroma Composition of Sour Whey
The increase in demand for food flavorings due to the shortening and simplification of food production technology also entails an increase in the demand for new technologies for their production. The biotechnological production of aromas is a solution characterized by a high efficiency, an independence from environmental factors and a relatively low cost. In this study, the influence of the implementation of lactic acid bacteria pre-fermentation into the production of aroma compounds by Galactomyces geotrichum on a sour whey medium on the intensity of the obtained aroma composition was analyzed. The monitoring of the culture in terms of biomass buildup, the concentration of selected compounds, and the pH resulted in the confirmation of interactions between the analyzed microorganisms. The post-fermentation product underwent a comprehensive sensomic analysis for the identification and quantification of the aroma-active compounds. The use of gas chromatography−olfactometry (GC−O) analysis and the calculation of odor activity values (OAVs) allowed 12 key odorants to be identified in the post-fermentation product. The highest OAV was found for phenylacetaldehyde with a honey odor (1815). The following compounds with the highest OAVs were 2,3-butanedione with a buttery aroma (233), phenylacetic acid with a honey aroma (197), 2,3-butanediol with a buttery aroma (103), 2-phenylethanol with a rosy aroma (39), ethyl octanoate with a fruity aroma (15), and ethyl hexanoate with a fruity aroma (14).