Streptococcus Thermophilus Counts Research Articles

The effect of three different preservatives on the numbers and types of bacteria, Brix percentage, pH and nutritional composition of bovine colostrum sourced from New Zealand dairy farms

ABSTRACT Aims To investigate the effect of preservation by addition of yoghurt starter, potassium sorbate and citric acid on counts of aerobic bacteria, Lactobacillus spp., Streptococcus thermophilus and coliforms, Brix percentage, pH, protein, fat and anhydrous lactose concentrations at 0, 7 and 14 days after collection for colostrum stored at ambient temperature. Method Approximately 2 L of first milking colostrum was collected from 10 farms in the Waikato region. Following mixing, it was split into five 400-mL sub-samples and allocated randomly to a control (two sub-samples), or treatment with yoghurt, potassium sorbate, or citric acid preservative. Throughout the trial samples remained in the laboratory at ambient temperature with the lids slightly ajar, and were stirred daily for 15–30 seconds using a sterile spatula. Sub-samples were tested on Days 0, 7 and 14. On Days 0 and 14 aerobic bacteria (by aerobic plate count (APC)), Lactobacillus spp., coliforms and Streptococcus thermophilus counts, pH, Brix percentage, protein, fat and anhydrous lactose were measured. On Day 7 only bacterial counts were completed. The data were analysed using non-parametric clustered bootstrap sampling to estimate the effect of treatment, time, and their interaction on the outcome variables. Results Compared to control samples, on Day 7 the APC for potassium sorbate (1.0 (90% CI = 0.6–1.6) × 108 cfu/mL) was approximately seven-fold lower than for yoghurt (7.3 (90% CI = 4.1–11) × 108 cfu/mL), and approximately three-fold lower than citric acid (3.2 (90% CI = 0.2–4.3) × 108 cfu/mL) remaining low to Day 14. All preservatives reduced coliform growth compared to control samples at Day 7 but growth was lower for potassium sorbate than the other preservatives. For Lactobacillus spp., at Day 7, samples with yoghurt preservative had greater counts than the other two preservatives. Potassium sorbate reduced growth of S. thermophilus compared to the other treatments, especially at Day 7, with 7–10 times fewer S. thermophilus per mL compared to the other three groups. All groups showed an obvious acidification over time, with very little variation within days and treatment groups. There was no evidence for change in fat or protein percentage over time regardless of treatment. Conclusion and clinical relevance Aerobic and coliform bacteria proliferate extensively in unpreserved colostrum. All preservatives decreased coliform counts compared to un-preserved colostrum, but potassium sorbate was more effective at decreasing both coliforms and aerobic bacteria than either yoghurt or citric acid.

Characteristics of apricot yogurt fermented with different culture straıns and stevıa

This study evaluated the effects of exopolysaccharide (EPS)-producing and non-EPS-producing culture varieties and the enriching of apricot pulp to the post-acidification process and microbiological, viscosity, antioxidant, and sensory properties of yogurt. Two groups of yogurts were produced in terms of culture variety. One of the yogurts in both groups was enriched with apricot pulp at a ratio of 10%. The natural sweetener, stevia, was added at a ratio of 0.1% to all yogurts. The lowest pH and highest acidity values were determined for the non-EPS sample produced without apricot pulp. The dry matter content of the yogurts was increased with whey protein powder. Between the yogurts produced with EPS-producing strains, the bacteria counts were higher for those enriched with apricot pulp. The highest Streptococcus thermophilus counts were determined for the sample produced with EPS-producing culture and apricot pulp at the beginning and end of the storage. Total phenolic content (TPC) was higher for the samples produced with conventional culture and enriched with apricot pulp. Similar results were observed in the antioxidant activity. Sensory attributes were considered taste, odor, appearance, texture, and overall acceptability. The yogurts produced with EPS-producing culture were preferred regarding taste, texture, and overall acceptability.

Enhancing Low-Fat Probiotic Yogurt: The Role of Xanthan Gum in Functionality and Microbiological Quality

The objective of this study was to determine the effect of XG addition on low-fat yogurt (LFY) properties. Pasteurized skimmed buffalo milk (SBM) was heated to 95 ± 2 °C for 16 s, cooled to 40 ± 1 °C, and then divided into six treatment lots. The treatments included the following: T1 (control), T2 (0.2% XG), T3 (0.4% XG), T4 (0.6% XG), T5 (0.8% XG), and T6 (1% XG). A proportion of 2% of a mixed starter culture from Streptococcus thermophilus (ST), Lactobacillus bulgaricus (LB), and Bifidobacterium bifidum (BB) in the ratio 1:1:1 was added. Yogurt was manufactured following the standard manufacturing protocol. Chemical composition and texture were determined at fresh time, while water-holding capacity (WHC), viscosity, and syneresis % were determined at 0, 7, 14, and 21 days of storage. Total bacterial counts (TBC), lactobacilli, streptococci, and bifidobacteria counts were determined at 0, 7, 14, and 21 days of storage. Sensory analysis was performed immediately upon the cooling stage (time zero) and then after 14 and 21 days of storage. The experiment was performed in trice. The results obtained showed that the addition of XG in LFY significantly (p < 0.05) decreases the pH, total protein (TP), and ash, and significantly (p < 0.05) increased the total solids (TS). Additionally, the addition of XG led to a significant (p < 0.05) increase in hardness, WHC, and viscosity; however, syneresis significantly (p < 0.05) decreased. The addition of higher amounts of XG led to a significant (p < 0.05) decrease in the TBC and led to a significant (p < 0.05) increase in counts of ST, LB, and BB during the first two weeks of the storage period. Sensory evaluation revealed that increasing the XG concentration up to 0.8% increased the product’s acceptability among panelists; however, further increasing the concentration to 1% had a detrimental impact on its acceptability. To conclude, this study showed that XG can be used as a stabilizer in the manufacturing of LFY as well as a prebiotic for starter culture and improve the quality of LFY.

The Effect of High-Pressure Processing of Caprine Milk on the Production and Properties of Yoghurt.

The aim of this study was to determine the suitability of HP-treated caprine milk for yoghurt production and to evaluate the effect of HP treatment on yoghurt properties. Reconstituted caprine milk was subjected to HP treatment (350 MPa/10 min/20 °C); a lactic acid starter culture (YC-X16, Chr. Hansen) was added. Milk was fermented at a temperature of 43 °C until pH 4.60. Bacterial counts, pH, color, rheological characteristics, texture, microstructure, and the sensory attributes of the yoghurt were determined after production and after seven days of storage at a temperature of 4 °C. HP treatment increased color saturation and whiteness index and induced a minor increase in milk pH. Minor differences in the acidification curve were noted. During storage, Streptococcus thermophilus counts were significantly higher in yoghurt from HP-treated than from untreated milk, whereas Lactobacillus delbruecki ssp. bulgaricus counts remained stable. A color analysis did not reveal differences between the experimental and control yoghurts. After storage, yoghurt made from HP-treated milk was characterized by thicker consistency and lower rheological stability than the control yoghurt. The micrographs of the yoghurts confirmed the differences in rheological parameters. Yoghurt produced from HP-treated caprine milk and stored for seven days received the highest scores in the sensory evaluation.

Engineering the β-galactosidase from Aspergillus oryzae for making lactose-free and no-sugar-added yogurt

Yogurt usually contains 5% to 7% sugar and 3% to 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, the β-galactosidase AoBgal35A from Aspergillus oryzae was engineered by site-saturation mutagenesis. Results of 19 variants of T955 residue showed that the lactose hydrolysis rate of T955R-AoBgal35A was up to 90.7%, which is much higher than the 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 Komagataella pastoris, which produced extracellularly 4,528 U/mL of β-galactosidase activity. The mutant T955R-AoBgal35A was used to produce LF yogurt. The Streptococcus thermophilus count of LF yogurt increased from 7.9 to 9.5 log cfu/g, which is significantly higher than that of the control group (8.9 log cfu/g). The residual lactose content of LF yogurt was 0.13%, meeting the requirements of the national standard in China for the "lactose-free" label (<0.5%). 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, water-holding capacity, and titratable acidity of LF and LF-NSA yogurt achieved good shelf life stability. Therefore, this study provides an insight for technological implications of β-galactosidases in the dairy industry.

Influence of Hesperidin on the Physico-Chemical, Microbiological and Sensory Characteristics of Frozen Yogurt.

Frozen yogurts contain yogurt culture bacteria, which might impart health benefits to their consumers. Global frozen yogurt market sales are expected to grow by 4.8% by 2028, which represents an important opportunity for the industry, consumers and researchers. Polyphenols are metabolites found in plants which have antioxidant and anti-inflammatory properties and might prevent chronic diseases such as cancer, diabetes and cardiovascular diseases. The objective of this study was to elucidate the effect of the polyphenol hesperidin on the physico-chemical, microbiological and sensory characteristics of frozen yogurts. Hesperidin was incorporated into frozen yogurt at three concentrations (125, 250 and 500 mg/90 g of product), while yogurt with no hesperidin was used as a control. The viscosity and overrun of the frozen yogurt were analyzed on day 0. The hardness, pH, color and Lactobacillus bulgaricus and Streptococcus thermophilus counts were determined after 0, 30 and 60 d. The melting rate was determined at 60 and 90 min after 0, 30 and 60 d. The bile and acid tolerances of both S. thermophilus and L. bulgaricus were measured after 7 and 60 d. A hedonic scale of nine points was used to measure sensory attributes. Data were analyzed at α = 0.05 with an ANOVA with Tukey's adjustment, and McNemar's test was used to analyze purchase intent. Hesperidin did not influence the pH, overrun or microbial characteristics. Polyphenol addition compared to the control decreased the melting rate but increased the hardness and bile tolerance of L. bulgaricus, as well as the L* and b* values. The sensory characteristics were not influenced by the lowest concentration of hesperidin, as it was not statistically different from the control. Moreover, consumers were interested in purchasing frozen yogurt with added hesperidin after learning about the health claim. This study can assist in the development of a healthier frozen yogurt in an increasingly competitive market.

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.

Physico-chemical, microbiological, and sensory characteristics of yogurt as affected by various ingredients

l-Glutamine, quercetin, slippery elm bark, marshmallow root, N-acetyl-d-glucosamine, licorice root, maitake mushrooms, and zinc orotate have been reported to help treat leaky gut. The purpose of this research was to explore the impact of these functional ingredients on the physico-chemical, microbiological, and sensory properties of yogurt. The milk from same source was equally divided into 9 pails and the 8 ingredients were randomly assigned to the 8 pails. The control had no ingredient. Milk was fermented to yogurt. The pH, titratable acidity, syneresis, viscosity, color (L*, a*, b*, C*, and h*), Streptococcus thermophilus counts, and Lactobacillus delbrueckii spp. bulgaricus counts of yogurts were determined on d 1, 7, 14, 21, 28, 35, and 42, whereas coliform counts, yeast and mold counts, and rheological characteristics were determined on d 1 and 42. The sensory study was performed on d 3 and particle size of the functional ingredients (powder form) was also determined. When compared with control, the incorporation of slippery elm bark into yogurts led to less syneresis. l-Glutamine increased pH and n' values (relaxation exponent derived from G') and lowered titratable acidity values. N-Acetyl-d-glucosamine incorporation resulted in higher n' and lower titratable acidity values, whereas maitake mushroom led to lower n' values. Incorporating quercetin increased the growth of L. bulgaricus. Adding maitake mushrooms increased the growth of S. thermophilus but lowered apparent viscosity values, whereas quercetin decreased its S. thermophilus counts. Quercetin decreased L* and a* values but increased b* values, and maitake mushroom increased a* values. Thixotropic behavior increased with the addition of licorice root and quercetin. Adding slippery elm bark, N-acetyl-d-glucosamine, licorice root, maitake mushrooms, and zinc orotate into yogurt did not affect the sensory properties, whereas yogurts with quercetin had the lowest sensory scores. Overall, most of these ingredients did not cause major changes to yogurt properties.

Formulation of a probiotic buttermilk powder using cell protectants by spray drying and estimation of its shelf-stability

Probiotic powders have received significant attention in recent times, due to their health benefits. However, the decrease in viable counts of the probiotic bacteria after spray drying and during subsequent storage remains a concern for spray-dried powders. Therefore, the proportion of the cell protectants such as whey protein concentrate (WPC), trehalose, and maltodextrin were optimised by response surface methodology to achieve high viability of bacteria in the spray-dried buttermilk powder along with evaluation of their physicochemical characteristics. The viable counts of Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus and Bifidobacterium bifidum were, respectively, 32.6, 52.2, and 50.9% lower in the control sample without protectants than in the powder containing protectants after 49 d of refrigerated storage. The optimised concentration of the thermal protectants in this study will help in the industrial production of buttermilk powder with desirable properties and an affordable cost.

Synergistic combination of cryoprotectants for high freeze-dried survival rate and viable cell counts of Streptococcus thermophilus

Vacuum freeze-drying is one of the common methods to prepare probiotic powder. However, the low temperature and low moisture content could lead to the death of probiotics. The method of adding cryoprotectants is efficient to improve the survival rate of probiotics during vacuum freeze-drying. The synergistic combination of different cryoprotectants could play a better protective effect. However, the principle of the synergistic combination of different cryoprotectants during vacuum freeze-drying is not clear. In this study, literature review and analysis were firstly used to reveal commonly used cryoprotectants for coccus. Taking the price of cryoprotectants into account, the combination is preliminarily determined as sucrose/skim milk/sodium glutamate. Then, taking Streptococcus thermophilus 937 as the research target strain, the effect of this cryoprotectant combination was verified by a single-factor screening experiment and concentration optimization of cryoprotectants. It was found that the preferred cryoprotectant combination for Streptococcus thermophilus 937 is 6% sucrose/8% skim milk/4% sodium glutamate, with the freeze-dried survival rate and viable counts being 90.59% and 1.78 × 1011CFU/g, respectively. Meanwhile, this cryoprotectant combination also had a good protective effect on the other two cocci, Streptococcus thermophilus Grx02 and Enterococcus faecium 218. This result might have guiding and reference significance on the vacuum freeze-drying of coccus.

Optimization of spray‐dried probiotic buttermilk powder using response surface methodology and evaluation of its shelf stability

In the present study, double-toned milk was inoculated with Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, and Bifidobacterium bifidum, to result in a curd which was further subjected to homogenization and spray drying. Various process parameters like inlet temperature (140–160°C), the flow rate of feed (10–20 ml/min), and compressed air (2–4 kg/cm2) were varied to obtain the best-operating conditions for the maximum viable count in the probiotic cultured buttermilk powder. The yields of the powder ranged between 58.4% and 71.5%. An inlet temperature of 150°C, feed flow rate of 15 ml/min and compressed air of 3 kg/cm2 were the optimum process parameters obtained by response surface methodology for maximum survival of starter culture and probiotic bacteria Bifidobacterium bifidum. The powder stored at 4 ± 1°C showed superior qualities to that stored at 27 ± 1°C. While moisture content, aw, solubility and density showed an increase, hygroscopicity exhibited a decline during storage. The final moisture content, hygroscopicity, aw, solubility index, and bulk density of buttermilk powder stored at 4 ± 1°C and 27 ± 1°C were 5.93, 13.73, 0.293, 59.78, 0.71, and 6.27, 12.31, 0.301, 60.12, 0.93 respectively. The viable counts of Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus and Bifidobacterium bifidum in BMP were 8.07 ± 0.21, 7.68 ± 0.17, 6.01 ± 0.18 at 4 ± 1°C and 5.73 ± 0.17, 5.57 ± 0.14, 4.14 ± 0.20 at 27 ± 1°C after 4 weeks of storage. Practical applications Probiotics have gained tremendous attention in recent times. However, the viability of probiotics during rigorous food processing and handling steps remains a matter of concern. Spray drying results in a powder that can be easily handled, stored, and reconstituted in beverages. A probiotic cultured buttermilk powder was obtained by optimizing the inlet temperature, feed flow rate, and compressed air while spray drying. Buttermilk is a valuable by-product usually lost in waste streams during the manufacturing of butter. This study attempts to valorize buttermilk by developing a spray dried probiotic buttermilk powder and evaluate its shelf-life under refrigerated storage and ambient conditions, which would be of great help to the industry.

Potential Probiotic Acceptability of a Novel Strain of Paenibacillus konkukensis SK 3146 and Its Dietary Effects on Growth Performance, Intestinal Microbiota, and Meat Quality in Broilers.

Simple SummaryThis study investigated the probiotic characteristics of Paenibacillus konkukensis and its dietary effects on growth performance, intestinal characteristics, intestinal microbiota, and meat quality in broilers. Through this study, P. konkukensis showed non-hemolytic activity, variable antibiotic susceptibility, and moderate acid and bile tolerance. Supplementary feeding of P. konkukensis as bacterial culture did not affect the growth performance parameters and meat quality, with positive effects on meat yield and intestinal microflora. Overall, dietary P. konkukensis may not have any adverse effects and might be considered as a probiotic feed additive in poultry.This study evaluates the in vitro probiotic characteristics of P. konkukensis sp. nov. SK-3146, which was isolated from animal feed, and its dietary effects on growth performance, intestinal characteristics, intestinal microbiota, and meat quality in broilers. In vitro experiments revealed that P. konkukensis was non-hemolytic with variable antibiotic susceptibility, and acid as well as bile tolerance. To assess the effect of P. konkukensis on broilers, a total of four hundred eighty 1-day-old Ross 308 broiler chicks were allocated to 3 treatment groups with 4 replicates of 40 birds each; the negative control group was fed a basal diet without any feed additives (NC), the positive control group was fed a basal diet containing 0.01% enramycin (PC), and the experimental group was fed a basal diet containing P. konkukensis bacterial culture (PK) at 104 CFU/g of the diet based on bacterial count. The experiment lasted for 35 days. Results indicated that there were no significant differences in any growth performance parameters among the dietary treatments (p > 0.05). In addition, the inclusion of P. konkukensis in the broilers’ diet did not affect meat cooking loss, color, and pH but increased the relative weight of breast meat (p < 0.05). The PK group showed heavier intestinal weight and shorter intestinal length than the NC group (p < 0.05). The ratio of the intestinal weight to length of jejunum was the highest in the PK group (p < 0.05). The PK group showed increased counts of Streptococcus thermophilus (p < 0.05) with no adverse effects of P. konkukensis on other intestinal microbiota in the jejunum. This study implies that P. konkukensis might have the potential to be applied as a probiotic feed additive in poultry.

Inulin as a prebiotic for the growth of vegan yoghurt culture in pea protein-based vegan yoghurt-ice cream, while improving the textural properties

The study aimed to develop a vegan yoghurt-ice cream made up of pea protein isolate with inulin as a prebiotic for the growth of yogurt culture while investigating the influence of inulin on textural properties – hardness, melting, overrun, and colour. Freeze-dried cultures were added at 0.02% (w/v) to the mixes made up of 0, 1, 2, 3, and 4% inulin, and incubation was done at 45 °C until it reaches a pH of 4.5. A significant (p<0.05) increase in counts of Streptococcus thermophilus and Lactobacillus bulgaricus were observed with the addition of inulin (2, 3, and 4%) and count was maintained more than 6 log CFU/g during 10 days of storage. The maximum overrun of 42.87 ± 3.74% was obtained with the addition of 4% inulin. The fermentation of pea protein ice cream mixes showed a significant (p<0.05) reduction in the hardness and melting times increased with the inulin addition. The colour values L*, a* and b* were influenced by fermentation and blueberry-juice concentration in the formulation. It can be concluded that the addition of inulin to the pea protein yoghurt-ice cream showed prebiotic activity and influenced the textural properties during the development of vegan probiotic food as a dairy alternative.

Effect of lactose hydrolysis and salt content on the physicochemical, microbiological, and sensory properties of ayran

Ayran is a salty drinkable yoghurt, but lactose in ayran induces lactose intolerance. This can be overcome by production of lactose-free or lactose-reduced ayran. Milk with 50% and 100% lactose hydrolysis by β-galactosidase was therefore used for alternative lactose-reduced or lactose-free ayran production. Physicochemical, microbiological, and sensory analyses were performed during storage at 4 °C for 28 days. Syneresis and flow behaviour index values increased, and apparent viscosity and consistency coefficient values decreased with increasing lactose hydrolysis level, salt content (0.5 and 1%), and storage period. No significant effects of lactose hydrolysis level and salt content on the counts of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus were found, while counts of these bacteria decreased during the storage period. Sensory evaluation highlighted that the 1% salt-containing ayran samples, which had higher scores of overall liking than 0.5% salt-containing ones, were significantly different from commercial ayran within the storage period.

Effect of blueberry addition on antioxidant activity, textural, microbiological and physicochemical properties of strained yoghurt.

In this research, the microbiological, physicochemical, rheological, textural, sensory properties and antioxidant activity of blueberry pulp added (0, 4%, 8% and 12%) strained yoghurt samples were investigated during a 28 day storage period. The Lactobacillus delbrueckii spp. bulgaricus and Streptococcus thermophilus counts in the samples were found to have decreased at the end of the storage period. The lightness, yellowness/blueness and whiteness index values showed a decrease depending on the addition of blueberry, while the redness/greenness values increased. The addition of blueberry had a negative the effects on the fat and protein values, while it had a positive effect on the total solids values. The storage period did not significantly change any of the physicochemical, colorimetric or rheological properties of the strained yoghurt samples. The general acceptability scores of the sample containing 12% blueberry were higher than the other samples. The antioxidant activities and total phenolic content of the strained yoghurt samples increased in accordance with blueberry concentration, while the firmness and work of the shear values decreased. In conclusion, it was determined that the addition of blueberry pulp at a 12% ratio could be used to enhance the nutritional and functional properties of strained yoghurts.

The impact of medicinal and aromatic plant addition on antioxidant, total phenolic, antimicrobial activities, and microbiological quality of Mozzarella cheese

In the present work, the antioxidant, antimicrobial activities, total phenolic content, and microbiological quality of Mozzarella cheeses added with medicinal and aromatic plants namely rosemary (Rosmarinus officinalis L.), basil (Ocimum basilicum L.), peppermint (Mentha piperita L.), and Turkish oregano (Origanum onites L.) were investigated. Results demonstrated that peppermint and Turkish oregano increased antioxidant and antimicrobial activities, while Turkish oregano and basil increased the total phenolic content of the Mozzarella cheese samples. Mozzarella cheese samples added with Turkish oregano exhibited antimicrobial activity against Escherichia coli, Listeria monocytogenes, and Enterococcus faecalis during 30 days of storage. Mozzarella cheese sample added with rosemary and peppermint exhibited antimicrobial activity against Staphylococcus aureus in early storage, and Mozzarella cheese sample added with rosemary and Turkish oregano exhibited antimicrobial activity against Bacillus cereus on the 10th day of storage. It was determined that the highest activity against the tested microorganisms was observed in Mozzarella cheese sample added with Turkish oregano and peppermint. It was also determined that Lactobacillus spp. and Streptococcus thermophilus counts were above log 4 CFU/g for 30 days. The addition of medicinal and aromatic plants to the Mozzarella cheese samples did not affect yeast and mould development, and the yeast and mould counts increased during the storage period.

Physicochemical, viability, microstructure, and sensory properties of whole and skimmed buffalo set‐yogurts containing different levels of polydextrose during refrigerated storage

This work was planned to investigate the influence of polydextrose as a fat replacer on the properties of skimmed yogurt. So, five batches were prepared; full-fat yogurt (control) and four skimmed yogurt batches prepared with 0%, 1.0%, 2.0%, and 3.0% polydextrose, respectively. Addition of polydextrose had significant effects on pH values and acidity and skimmed yogurt with 3% polydextrose exhibited significantly (p ≤ .05) higher in the apparent viscosity, WHC, and lower in syneresis. The viable counts of Streptococcus thermophilus and Lactobacillus spp. in samples containing polydextrose remained above ˃106 CFU/g. Microstructure showed stronger and more stable gel structures in treatment with 3% polydextrose. No significant differences were noted between yogurt with 3% polydextrose and full-fat yogurt in sensory attributes except flavor. Higher sensory scores were observed for yogurt with 3% polydextrose. Thus, the addition of 3% polydextrose was sufficient to develop skimmed yogurt with desired properties. Practical applications In recent years, growing attention to diet and healthy food products. these products are lower or free in fat contents because of their nutritional values and health-promoting properties. Yogurt is the most popular fermented functional dairy product consumed by all ages worldwide. The addition of polydextrose as a fat replacer with the level of 3% to yogurt increased the viability of starters and enhanced the physical and sensory properties of the product. Finally, our study concluded that the addition of polydextrose proves the effectiveness and consumption of fat-free dairy foods. We can produce many fat-free cheeses, ice creams, and beverages for special cases.

Physicochemical and microbiological characteristics of camel milk yogurt as influenced by monk fruit sweetener

Camel milk, similar to cow milk, contains all of the essential nutrients as well as potentially health-beneficial compounds with anticarcinogenic, antihypertensive, and antioxidant properties. Camel milk has been used for the treatment of allergies to cow milk, diabetes, and autism. Camel milk helps decrease cholesterol levels in blood and improves metabolism. One of the most desirable food tastes is sweetness. However, the excessive ingestion of sugar negatively affects human health. Monk fruit sweetener is a natural, 0-calorie sweetener with many health-beneficial functions. Monk fruit sweetener helps decrease symptoms of asthma and diabetes, prevents oxidation and cancer, protects the liver, regulates immune function, and lowers glucose levels. Monk fruit sweetener is 100 to 250 times sweeter than sucrose. The objective of this study was to examine the influence of different concentrations of monk fruit sweetener on the physicochemical properties and microbiological counts of drinking yogurt made from camel milk. Camel milk drinking yogurt was produced with 0, 0.42, 1.27, and 2.54 g/L of monk fruit sweetener and stored for 42 d. The physicochemical characteristics and microbiological counts of yogurts were measured at d 1, 7, 14, 21, 28, 35, and 42. For the physicochemical characteristics, pH, titratable acidity, viscosity, and color [lightness-darkness (L*), red-green axis (a*), yellow-blue axis (b*), chroma (C*), and hue angle (h*)] values were evaluated. The counts of Streptococcus thermophilus, Lactobacillus bulgaricus, Lactobacillus acidophilus, coliforms, and yeast and mold were determined. Three replications were conducted. The sweetener addition significantly influenced pH, viscosity, and color (a*, b*, C*, and h*) values. Control samples had significantly higher pH values, lower viscosity, lower b* and C* values, and higher h* values than the samples with 1.27 and 2.54 g/L of monk fruit sweetener. Growth of S. thermophilus, L. bulgaricus, and probiotic culture L. acidophilus was not affected by the incorporation of monk fruit sweetener. Monk fruit sweetener can be added in camel milk yogurts as a health-beneficial 0-calorie sweetener.

Use of soy as a source of protein in low-fat yogurt production: microbiological, functional and rheological properties

The objective of this study was to evaluate the effect of different protein sources incorporated into milk to produce low-fat yogurt (LF-yogurt). Five treatments were used: YC – yogurt control (without protein supplementation), YM – yogurt with milk powder, YWP – yogurt with whey protein, YSP – yogurt with soy protein, and YSF – yogurt with soy flour. Microbiological counts of Streptococcus thermophilus and Lactobacillus bulgaricus, pH, lactic acid and changes in rheological and structural properties (firmness, color, microstructure and syneresis) were followed throughout 28 days of storage. Antioxidant capacity (DPPH and ABTS assay) and total phenolic compounds were also analyzed. Addition of different ingredients influenced S. thermophilus and L. bulgaricus CFU counts. LF-yogurts supplemented with milk powder, soy flour and soy protein were firmest, and yogurts supplemented with milk powder and soy flour had the least syneresis. LF-yogurts with soy flour were darker, redder and yellower, contained more polyphenols and exhibited higher antioxidant activity. Thus, supplementation of LF-yogurt with soy is interesting since it confers functional activity to the yogurt and also modify its technological properties.

Antioxidant activity and some quality characteristics of buffalo yoghurt fortified with peanut skin extract powder.

Peanut is an important crop grown worldwide. Peanut skin, the byproduct of peanut processing is a valuable byproduct due to its content of many functional components. Therefore, this study aimed to evaluate the effect of fortification of yoghurt with peanut skin extract powder (PSEP) at 50, 100 and 200mg/L milk on the antioxidant activity (radical scavenging activity RSA%) and some quality characteristics of the resultant yoghurt during cold storage. The obtained results revealed that total phenolic content of PSEP is 109.46mg GAE/g while it's radical scavenging activity % reached 90.57%. Fortification of yoghurt with PSEP increased the apparent viscosity, antioxidant activity, and total phenolic, acetaldehyde, and diacetyl contents as compared to control, while the syneresis of fortified yoghurt was reduced. Microbiological analysis showed that fresh control yoghurt had the highest counts of Streptococcus thermophilus and Lactobacillus bulgaricus and decreased at the end of storage in all treatments. Both control and T1 (the low concentration of PSEP) gained the highest acceptability; therefore, it was recommended that fortification of yoghurt with 50mg of PSEP/L is more preferable than the other concentrations. In addition, it could be considered as a natural antioxidant source in formulating functional yoghurt either in industrial and/or small industrial scale.