Yeasts are the leading cause of spoilage in yogurt. Considering the high demand from consumers to use natural products as an alternative to additives, essential oils (EOs) could be a promising ...solution to guarantee high microbiological standards. The present study highlighted the in vitro antifungal potential of cinnamon, ginger, lemongrass, mandarin, orange, lemon and lime EOs against spoilage yeasts isolated from yogurts prepared with pasteurized buffalo milk. A total of 74 isolates represented by 14 different species of Candida, Rhodotorula, Debaryomyces, Kluyveromyces and Yarrowia genera were subjected to a disc diffusion assay, showing lemongrass EO to have the highest antifungal activity (40.97 ± 9.86 mm), followed by cinnamon (38.46 ± 6.59 mm) and orange (12.00 ± 4.52 mm) EOs. Yarrowia lipolytica was less susceptible to lemongrass EO than Candida sake and Yarrowia deformans isolates. Ginger EO exhibited the lowest efficacy. A minimum inhibitory concentration (MIC) assay showed the ability of lemongrass and cinnamon EOs to inhibit the growth of all selected isolates at concentrations between ≤0.31 and 1.25 μL/mL. Therefore, for the first time, the two best-performing EOs (lemongrass and cinnamon) based on in vitro assays were assessed for their potential roles as preservatives in an in vivo yogurt model prepared at the laboratory scale. Since some limitations, such as the inhibition of lactic acid bacteria by cinnamon EO, consequently leading to fermentation failure as well as species-specific antifungal activity of lemongrass EO, were observed, further studies are needed to explore the possibility of using a slightly higher concentration of lemongrass EO and/or combinations of different EOs and/or their components. Finally, since yogurt spoilage could also be prevented by correct sanitation procedures of the production environment, the sanitizers commonly used in the food industry were tested against all isolates, showing the high efficiency of alcohol-based sanitizers and the ineffectiveness of chlorine-based sanitizers.
•Seven essential oils (EOs) were tested in vitro against 74 yogurt spoilage yeasts.•Lemongrass and cinnamon EOs showed the highest in vitro antifungal activity.•Cinnamon and lemongrass EO inhibited spoilage yeasts in an in vivo yogurt model.•Inhibition of lactic acid bacteria by cinnamon EO in in vivo system was observed.•High efficiency of alcohol-based sanitizers on yogurt spoilage yeasts was seen.
This study aimed at investigating the suitability of oat flakes for making functional beverages. Different technological options were assayed, including the amount of flakes, the inoculum of the ...starter and the addition of enzyme preparations. The beverage containing 25% (wt/wt) of oat flakes and fermented with L. plantarum LP09 was considered optimal on the basis of sensory and technological properties. The enzyme addition favored the growth of the starter, shortened the time needed to reach pH4.2 to ca. 8h, and favored a decrease of the quotient of fermentation. Fermentation increased the polyphenols availability and the antioxidant activity (25 and 70% higher, respectively) and decreased the hydrolysis index in vitro. Sensory analyses showed that fermented oat flakes beverage had the typical features of a yogurt-like beverage, enhancing the overall intensity of odor and flavor compared to the non-fermented control. Selection of proper processing and fermentation condition allowed the obtainment of a beverage with better nutritional and sensory properties.
•A biotechnological protocol for obtaining oat flakes beverage was set-up.•Technological advantages deriving by the use of selected lactic acid bacteria and enzymes were demonstrated.•Nutritional, sensory, and functional properties of the beverages were characterized.
Yogurt usually contains 5–7% sugar and 3–5% lactose. As β-galactosidases can hydrolyze lactose and improve sweetness, they have the potential to produce lactose-free (LF) and no-sugar-added (NSA) ...yogurt. In this study, β-galactosidase AoBgal35A from Aspergillus oryzae was engineered by site-saturation mutagenesis. Results of 19 variants of T955 residue showed that lactose hydrolysis rate of T955R-AoBgal35A was up to 90.7%, much higher than 78.5% of the wild type. Moreover, the optimal pH of T955R-AoBgal35A was shifted from pH 4.5 to pH 5.5 and the optimal temperature decreased from 60°C to 50°C. The mutant T955R-AoBgal35A was successfully expressed in Komagatella pastoris, which produced extracellularly 4528 U/mL of β-galactosidase activity. The mutant T955R-AoBgal35A was used to produce LF yogurt. Streptococcus thermophilus counts of LF yogurt increased from 7.9 to 9.5 lg cfu/g, significantly higher than that of the control group (8.9 lg cfu/g). Residual lactose content of LF yogurt was 0.13%, meeting the requirement of “lactose-free” label (<0.5%, GB 28050–2011, China). Furthermore, sugar in yogurt was replaced by whey powder to produce LF-NSA yogurt. The optimal addition content of whey powder was 7.5%. The texture, WHC and titratable acidity of LF and LF-NSA yogurt achieved good stability during the shelf life. Therefore, this study provides an insight for technological implications of β-galactosidases in the dairy industry.
Cereal‐based fermented products are becoming popular in the world. A millet‐based yogurt‐like product (MYP) using polymerized whey protein (PWP) and xanthan gum (XG) as thickeners was developed. The ...present study aimed to investigate the effects of PWP (0.3 to 0.5%, w/v) and XG (0 to 0.2%, w/v) on the gelation properties and microstructure of MYP. All samples were analyzed for rheological properties, textural properties, microstructure, and pH value during fermentation. The MYP Ⅲ (0.4% PWP and 0.1% XG) registered the highest elastic modulus (G′) throughout the fermentation and cooling steps (P < 0.05), but MYP Ⅳ (0.35% PWP and 0.15% XG) had the highest apparent viscosity compared with the other samples. No significant differences in the pH values among the samples were observed during the fermentation process (P > 0.05). The hardness value of MYP Ⅳ reached a maximum after 4 hr and then stabilized during fermentation. Scanning electron microscopy showed a compact and uniform network for the MYP with PWP and XG. MYP Ⅳ had the best texture properties (hardness, springiness, and gumminess). Overall, PWP (0.35%, w/v) and XG (0.15%, w/v) were the best combination for MYP as a thickening system.
Practical Application
Cereal‐based fermented products have attracted much attention in the food industry. However, due to absence of a natural protein network, it is hard to produce a set‐type millet‐based yogurt with a firm texture under the studied conditions without adding any thickening agents. In this study, PWP (0.35%, w/v) and XG (0.15%, w/v) can be used for fermentation of millet‐based yogurt‐like products. The new cereal‐based fermented product would be a promising food in the market.
•Nano-encapsulated fish oil was produced successfully from liposomes.•Nano-encapsulation resulted in a significant reduction in peroxide value.•Yogurt with nano-encapsulated fish oil had a higher DHA ...and EPA content.•Fortified yogurt gave closer results to control sample for sensory evaluation.
Fish oils have many dietary benefits, but due to their strong odors and rapid deterioration, their application in food formulations is limited. For these reasons, nano-liposome was used to nano-encapsulate fish oil in this study and encapsulated fish oil was utilized in fortifying yogurt. Physicochemical properties of produced yogurt including pH, acidity, syneresis, fatty acid composition, peroxide value as well as sensory tests were investigated during three weeks storage at 4°C. Nano-liposome encapsulation resulted in a significant reduction in acidity, syneresis and peroxide value. The results of gas chromatography analyses revealed that after 21days storage, yogurt fortified with nano-encapsulated fish oil had a higher DHA and EPA contents than yogurt containing free fish oil. Overall, the results of this study indicates that adding nano-encapsulated fish oil into yogurt gave closer characteristics to control sample in terms of sensory characteristics than yogurt fortified with free fish oil.
The probiotic features of Lactiplantibacillus (L.) pentosus and L. paraplantarum strains, endogenous in Cobrançosa table olives from northeast Portugal, were assessed in terms of functional ...properties and health benefits. Fourteen lactic acid bacteria strains were compared with Lacticaseibacillus casei from a commercial brand of probiotic yoghurt and L. pentosus B281 from Greek probiotic table olives, in attempts to select strains with higher probiotic performances than those references. For functional properties, the i53 and i106 strains, respectively, exhibited: 22.2 ± 2.2% and 23.0 ± 2.2% for Caco-2 cell adhesion capacity; 21.6 ± 7.8% and 21.5 ± 1.4% for hydrophobicity; 93.0 ± 3.0% and 88.5 ± 4.5% for autoaggregation ability by 24 h of incubation; and ability to co-aggregate with selected pathogens-from 29 to 40% to Gram+ (e.g., Staphylococcus aureus ATCC 25923 and Enterococcus faecalis ATCC 29212); and from 16 to 44% for Gram− (e.g., Escherichia coli ATCC 25922 and Salmonella enteritidis ATCC 25928). The strains proved to be resistant (i.e., halo zone ≤14 mm) to some antibiotics (e.g., vancomycin, ofloxacin, and streptomycin), but susceptible (i.e., halo zone ≥ 20 mm) to others (e.g., ampicillin and cephalothin). The strains exhibited health-beneficial enzymatic activity (such as acid phosphatase and naphthol-AS-BI-phosphohydrolase), but not health-harmful enzymatic activity (such as β-glucuronidase and N-acetyl-β-glucosaminidase). Additionally, the antioxidant activity and cholesterol assimilation features, respectively, of the strains were 19.6 ± 2.8% and 77.5 ± 0.5% for i53, and 19.6 ± 1.8% and 72.2 ± 0.9% for i106. This study indicated that the addition of L. pentosus strains i53 and/or i106 to Cobrançosa table olives is likely to enhance the added value of the final product, in view of the associated potential benefits upon human health.
Vitamin Bsub.12 and melatonin were added to whole milk-stirred yogurt to evaluate its physicochemical (fat, protein, total solids, moisture, syneresis, and color), rheological (flow behavior and ...dynamic rheology), and color characteristics as L, asup.∗, and bsup.∗ and color change (∆E). For this, five treatments (T) were elaborated as follows: T1 = yogurt (Y) without vitamin Bsub.12 and melatonin, T2 = Y with 3μ g/L of Bsub.12, T3 = Y with 5mg/L of melatonin, T4 = Y with 2μ g/L of Bsub.12 and 3mg/L of melatonin, and T5 = Y with 3μ g/L of Bsub.12 and 5mg/L of melatonin. The fortification of yogurt with vitamin Bsub.12 and melatonin modified (P<0.05) the content of fat, moisture, and syneresis. Treatment 5 presented the lowest content of fat and the largest content of moisture (P<0.05). Treatment 4 had the largest syneresis at day 1, and at day 14, there was not differences in syneresis among treatments (P>0.05). Regarding color, luminosity (Lsup.∗) did not have significant differences (P>0.05) among treatments and neither among storage days, except for T5 that presented the lowest value at day 14. Regarding parameter asup.∗, all treatments presented negative values (tendency to green), and T2, T3, and T5 showed significant differences (P<0.05) trough time. No significant differences (P>0.05) were observed for the bsup.∗ values neither among treatments nor among time. The highest value in Δ E, compare to the control, was observed in T5. Regarding flow behavior, T1 showed a significantly different (P<0.05) higher flow behavior (n) than the rest of the treatments. In general, all the samples indicate an increase (P<0.05) in the flow behavior (n) through the storage time. And the consistency index (K) showed significant difference (P<0.05) between T1 and T2 and T3 and T4. In conclusion, the addition of vitamin Bsub.12 and melatonin to yogurt generates changes in the physicochemical and rheological properties; likewise, the addition of melatonin in combination with vitamin Bsub.12 showed that the viscoelastic characteristics of the fortified yogurts are like the control yogurt. Since these, treatment 5 presented the most similar values of rheology and syneresis compared to the control, so this combination of Bsub.12 and melatonin could be employed to develop a new functional yogurt.
•Optical parameters were nondestructive predictors of the quality index in cow yogurt.•Quality index expressed loss of textural quality and post acidification in cow yogurt.•The quality index was ...predictor of overall acceptability in cow yogurt.•The quality predictive model was adequately applicable to commercial cow milk yogurts.
Physicochemical and microbiological changes in yogurts determine their storage and shelf life. Thus, monitoring yogurt quality is essential for consumer acceptance and food safety. However, traditional techniques of yogurt quality analysis are food-destructive, environment polluting, costly, and time-consuming. On the other hand, nondestructive techniques only measure a single quality property, not expressing the yogurt overall quality. In this study, predictive models validated by bootstrapping and cross-validation methods demonstrate the biogenic amine index (BAI) as a nondestructive monitoring system of overall quality during storage. The optical parameter was a strong nondestructive predictor of the BAI for both cow’s milk yogurt, CY (Rv = 0.944; p = 0.007), and goat’s milk yogurt, GY (Rv = 0.909; p = 0.009). For CY, the reduction in the overall acceptability during storage was a strong predictor of the BA index (Rv = 0.869; p < 0.05), with a suitable prediction accuracy in the application set of commercial samples (Rapplic = 0.847; accuracy = 84.06%;). For GY, the model had a low prediction capability of the overall quality. Given the high predictive ability of the model, the BAI has a great potential to perform a nondestructive assessment of the overall quality of CY during storage.
The objective of this study was to investigate the effect of 2 plant leaf extracts on fermentation mechanisms and health-promoting activities and their potential as a nutraceutical prebiotics ...ingredient for application in dairy products. The individual active phenolic compounds in the plant extract-supplemented milk and yogurts were also identified. Compared with control fermentation, the plant extracts significantly increased the growth and acidification rate of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus. In particular, plant extract components, including monosaccharides, formic acid, and hydroxycinnamic acid, such as neo-chlorogenic, chlorogenic, and caffeic acid, together play a stimulatory role and cause this beneficial effect on the growth of yogurt culture bacteria through fermentation. In addition, supplementation with the plant extracts enhanced antioxidant activities with increased total phenolic contents, especially the highest antioxidant activity was observed in yogurt supplemented with Cudrania tricuspidata leaf extract.
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