Comparative antioxidant potential of kefir and yogurt of bovine and non-bovine origins

Physicochemical, Textural, and Antioxidant Attributes of Yogurts Supplemented with Black Chokeberry: Fruit, Juice, and Pomace

The fruit, juice, and pomace of black chokeberry (Aronia melanocarpa) are a rich source of phenolic compounds and can be used to obtain enriched dairy products. Chokeberry fruit, due to its astringent taste, is less favorable or even unacceptable to consumers and is usually processed into juice, resulting in large quantities of pomace, which is often discarded as waste. The aim of this study is to valorize chokeberry fruit, juice, and pomace by incorporating them in different percentages (1, 2, and 3%) into yogurt as functional ingredients. The physicochemical (total solids content, fat, protein, titratable acidity, pH, color), textural (hardness, adhesion, cohesiveness, springiness, gumminess, and chewiness), antioxidant (DPPH scavenging activity and total phenolic content), and sensory characteristics of supplemented yogurts were investigated. The results showed that the addition of chokeberry pomace in yogurt increased their total solids content (from 11.46 ± 0.18% for the plain yogurt sample to 13.71 ± 0.18% for the yogurt sample with 3% chokeberry pomace), while the addition of fruit and juice decreased the protein content of the yogurt samples (from 4.35 ± 0.11% for the plain yogurt sample to 3.69 ± 0.15% for the yogurt sample with 3% chokeberry fruit and to 3.84 ± 0.1% for the yogurt sample with 3% chokeberry juice). There was no statistically significant change in the fat content of all samples of chokeberry-supplemented yogurt compared to plain yogurt. The pH of the yogurt samples decreased with the increase in the percentage of chokeberry fruit, juice, and pomace added to the yogurt (from 4.50 for the plain yogurt samples to 4.35, 4.30, and 4.20 for the yogurt samples supplemented with 1, 2, and 3% black chokeberry pomace). Inhibition of DPPH radical formation was higher in the yogurt samples with chokeberry fruit (57.84 ± 0.05%, 73.57 ± 0.11%, and 75.38 ± 0.05% inhibition for the samples with 1, 2, and 3% fruit) and pomace (up to 64.8 ± 0.11% inhibition for the sample with 3%), while total phenolic content decreased (from 392.14 ± 2.06 to 104.45 ± 2.63 µg/g) as follows: yogurt with chokeberry pomace > yogurt with chokeberry fruit > yogurt with chokeberry juice. The yogurt samples with the highest acceptance scores were the samples with 3% and 2% black chokeberry fruit, while the lowest acceptance score was obtained for the yogurt sample with 3% black chokeberry pomace. Chokeberry fruit, juice, and pomace can improve the physicochemical, textural, and antioxidant characteristics of yogurt, emphasizing that the antioxidant effect of yogurt could be substantially improved by the addition of chokeberry pomace due to its high phenolic content, while incorporation into yogurt is another way to valorize this by-product.

Comparing Nutritional Values and Bioactivity of Kefir from Different Types of Animal Milk

The growing interest in fermented dairy products is due to their health-promoting properties. The use of milk kefir grains as a starter culture made it possible to obtain a product with a better nutritional and biological profile depending on the type of milk. Cow, buffalo, camel, donkey, goat, and sheep milk kefirs were prepared, and the changes in sugar, protein, and phenol content, fatty acid composition, including conjugated linoleic acids (CLAs), as well as antioxidant activity, determined by ABTS and FRAP assays, were evaluated and compared. The protein content of cow, buffalo, donkey, and sheep milk increased after 24 h of fermentation. The fatty acid profile showed a better concentration of saturated and unsaturated lipids in all fermented milks, except buffalo milk. The highest content of beneficial fatty acids, such as oleic, linoleic, and C18:2 conjugated linoleic acid, was found in the cow and sheep samples. All samples showed a better antioxidant capacity, goat milk having the highest value, with no correlation to the total phenolic content, which was highest in the buffalo sample (260.40 ± 5.50 μg GAE/mL). These findings suggested that microorganisms living symbiotically in kefir grains utilize nutrients from different types of milk with varying efficiency.

Dynamic alterations of flavor, functional nutrients, and microbial community during fermentation of different animal milk kefirs

Kefir is a traditional dairy beverage, usually made from cow or goat milk fermented with kefir grains, and has many health benefits. To elucidate the fermentation patterns of animal milk kefirs during the fermentation process and find the optimal milk types, cow, camel, goat, and donkey milk were fermented with kefir grains for 0, 1, 3, 5, and 7 days. Volatile and non-volatile metabolites and microbial changes were dynamically monitored. The results showed that volatile flavor substances were massively elevated in four kefirs on days 1-3. Lipids and carbohydrates gradually decreased, while amino acids, small peptides, and tryptophan derivatives accumulated during fermentation in four kefirs. Besides, four kefirs had similar alterations in Lactobacillus and Acetobacter, while some distinctions existed in low-abundance bacteria. Association analysis of microorganisms and volatile and non-volatile metabolites also revealed the underlying fermentation mechanism. This study found that appropriately extending the fermentation time contributed to the accumulation of some functional nutrients. Furthermore, goat and donkey milk could be the better matrices for kefir fermentation.

Isolated Fraction of Gastric-Digested Camel Milk Yogurt with Carao (Cassia grandis) Pulp Fortification Enhances the Anti-Inflammatory Properties of HT-29 Human Intestinal Epithelial Cells

Functional foods have recently generated a lot of attention among consumers looking for healthy options. Studies have examined yogurt with carao to increase health benefits and probiotic characteristics. It has been determined that carao fruit and camel milk have high phenolic compound and antioxidant activity concentrations. The objective of this study was to examine if carao (0, 1.3, 2.65, and 5.3 g/L) incorporated into yogurt enhances anti-inflammatory stimulus and antioxidant activity and impacts the physio-chemical and sensory properties of camel milk yogurt. HT-29 cells were used as a model of anti-inflammatory response, including cytokine responses of IL-8 and mRNA production of IL-1β and TNF-α in gastric digested isolated fraction. In addition, pH, titratable acidity, Streptococcus thermophilus counts and Lactobacillus bulgaricus counts of camel yogurts were examined during the fermentation process in 0, 2.5, 5, and 7 h whereas viscosity, syneresis, and radical scavenging assay evaluations were determined at hour 7. Furthermore, a consumer study was performed. Compared to control samples, the incorporation of carao into yogurts did not lead to a significant (ρ > 0.05) difference in the pH. In contrast, titratable acidity (TA), viscosity, syneresis, and antioxidant capacity significantly increased with the inclusion of 2.65 and 5.3 g/L carao, while 5.3 g/L carao significantly (ρ < 0.05) increased the counts of both bacteria. The inflammatory response of IL-8 and the level of mRNA production of IL-1β and TNF-α was significantly (ρ < 0.05) lower with 2.65 and 5.3 g/L carao yogurt compared to control camel yogurt. Sensory attributes were not impacted by the addition of 1.3 and 2.65 g/L carao. Carao could be a possible ingredient to consider when improving the nutrition value of yogurt.

Physical and chemical properties, structural characterization and nutritional analysis of kefir yoghurt

Scanning electron microscopy (SEM), Confocal laser scanning microscopy (CLSM) and low field nuclear magnetic resonance (LF-NMR) were used to analyse the relationship between the chemical, texture, rheology, microstructure and water distribution of kefir (yeast, acetic acid bacteria and Lactobacillus plantarum) yoghurt fermented by mixed bacteria and L. plantarum L₁ fermented yoghurt. This work was conducted to prepare a real champagne yoghurt and explore the difference between it and ordinary yoghurt. The nutritional evaluation of the two treatment groups was carried out by amino acid analysis, and the volatile flavour substances of the two treatment groups were detected by solid phase microextraction (SPME)-gas chromatograph (GC)-mass spectrometry (MS). Results showed that the addition of acetic acid bacteria and yeast increased the water content of kefir, resulting in a decrease in its water-holding rate. Moreover, the increase in acidity weakened the connection between the protein networks, the flocculent protein structure was not more densely stacked than the L₁ group, and the internal bonds were unstable. The rheological results showed that the apparent viscosity decreased faster with the increase in shear force. The CLSM and LF-NMR showed that the hydration and degree of freedom of kefir yoghurt protein decreased, resulting in an increased protein network density. The SEM showed that the cross-linking between kefir casein clusters was considerably tight to form small chains, the pore distribution was uneven, and a weak cheese structure was formed. In addition, the volatile flavour substances in the kefir group increased the phenylethyl alcohol, isobutanol, and isoamyl alcohol compared with those in the L₁ group, with a slight refreshing taste brought by alcohol and special soft malt alcohol aroma and rose aroma not found in ordinary yoghurt, which was more in line with the characteristics and taste of traditional kefir champagne yoghurt. Graphical Abstract.

Protective effects of dietary Kefir against aflatoxin B1-induced hepatotoxicity in Nile tilapia fish, Oreochromis niloticus

The effect of dietary Kefir supplementation on the biometric, biochemical, and histological parameters of Nile tilapia (Oreochromis niloticus) exposed to aflatoxin B1 (AFB1, 200 µg/kg diet) contamination was studied. The yeasts were dominant in Kefir followed by lactic and acetic acid bacteria. The Kefir showed relatively interesting antioxidant potential in the DPPH• (IC50 = 0.9 ± 0.02 mg/ml) and ABTS•+ (IC50 = 2.2 ± 0.03 mg/ml) scavenging activities, Fe3+-reducing power (EC0.5 = 1.2 ± 0.01 mg/ml), and β-carotene bleaching assay (IC50 = 3.3 ± 0.02 mg/ml). Three hundred and sixty Nile tilapia weighing 23 ± 5 g were divided into four groups (30 fish/group with 3 replicates), and fed with diets containing Kefir (D2), AFB1 (D3), and Kefir+AFB1 (D4) for 4 weeks, whereas D1 was kept as control group where fish were fed with basal diet. The Kefir supplementation in D4 group significantly increased (p < .05) the percent weight gain as compared to D3 group. Moreover, Kefir improved the antioxidant enzymes in the liver, such as catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD) activities, that significantly increased (p < .05) by 2-, 3-, and 1.5-folds, respectively, as compared to D3 group. The Kefir treatment significantly decreased (p < .05) the liver malonaldehyde content by ~50% as compared to D3 group. Histopathological analysis revealed the hepatoprotective effects of Kefir by showing normal liver histological architecture in D4 group, as compared to degenerative changes observed in D3 group. These results suggest that Kefir could be considered as a potential probiotic in Nile tilapia feed to mitigate the AFB1 harmful effects.