Yogurt Samples Research Articles

Determination of Chemical and Microbiological Quality of Strained Yoghurt Samples Marketed in Aydın Province

In this study, 60 strained yoghurt samples, including 30 public bazaar and 30 dairy-markets were examined in terms of chemical and microbiological properties. According to chemical analysis of bazaar samples, average levels of pH, acidity, fat, protein, salt, total solid and ash are determined; 3.94, 2.19% (LA), 8.09%, 11.21%, 1.83%, 21.74%, 0.71%, respectively. The average levels of given elements above in samples gathered from dairy stores are determined; 3.94, 1.86% (LA), 9.47%, 11.95%, 1.81%, 23.26%, 0.71%, respectively. No presence of starch was found in any of the samples. The chemical analysis results of the strained yoghurt samples were determined in accordance with the values specified in Turkish Food Codex except for the amount of fat analysis gave a result over the specified value. Coliform bacteria level was determined

Investigation of aroma profiles, textural, rheological, and sensorial qualities of yogurts with various starter cultures and goat–cow milk combinations

Abstract In the present study, aroma components, textural, rheological and sensory qualities of yogurts produced using YC-350 and ABT-2 starter cultures and combinations of goat/cow milk were investigated during the storage period. For this purpose, aroma components were analyzed by GC-MS, textural analyses by TA.XTplus Texture Analyzer and rheological analyses by Anton Paar MCR 102 rheometer. The effects of goat/cow milk combinations and variety of starter culture on aroma components, textural, rheological and sensory properties of yogurt samples were found significant (p < 0.01). Also, the storage period significantly (p < 0.01) affected all parameters tested except cohesiveness, resilience, and appearance. While it was found that the use of cow milk in the experimental yogurt samples increased the acetaldehyde content, it was found that it had varying effects on the diacetyl content, acetoin content, and textural and rheological analysis parameters. It was determined that the content of diacetyl and acetoin reduced with the progression of the storage times. In the sensory evaluations, the use of goat milk had positive effects on the parameters of appearance and consistency by spoon, and the use of probiotic culture (ABT-2) had positive effects on the parameters of consistency by mouth and overall acceptability.

Influence of green pepper extract on the physicochemical, antioxidant, and sensory properties of stirred yogurt

The green pepper has garnered interest in different societies as a functional food and food additive. Numerous studies have indicated that the phytochemicals found in pepper possess antioxidant, anti-cancer, anti-inflammatory, anti-obesity, and anti-arteriosclerotic properties. In this study, green pepper extract was used in yogurt to increase the acceptability of consumption and improve its health properties. For this purpose, green pepper extract was added in concentrations 100, 200, and 300 ppm in the preparation of yogurt. And pH, acidity, total content of phenolic compounds, DPPH inhibition percentage, viscosity, syneresis, and sensory properties were evaluated in 1, 7, 14, and 21 days after production. The results showed that by increasing the amount of extract, the percentage of antioxidant activity and phenolic compounds increased significantly. The effect of storage time on these indicators was also significant (p < 0.05). in such a way that over time, there was a decrease in antioxidant activity. But, there was a slight increase in antioxidant activity on the 14th day of storage. Also, the effect of treatment type on some physicochemical characteristics of yogurt containing green pepper extract including pH, acidity, viscosity, and syneresis was significant (p < 0.05). During storage, acidity, syneresis, and viscosity increased and pH decreased significantly in all yogurt samples. Regarding the tested sensory attributes, the 200 ppm sample received the highest score among the evaluators, and in terms of overall acceptance, the samples containing the extract were more favorable than the control sample.

Investigating the impact of exopolysaccharides on yogurt network mechanics and syneresis through quantitative microstructural analysis

Exopolysaccharides produced by lactic acid bacteria are widely used to improve the sensory properties of yogurt. The relation between the physical properties of the microbial exopolysaccharides and the structural and rheological properties of the yogurt are incompletely understood to date. To address this knowledge gap, we studied how two distinct exopolysaccharides influence the microstructure, rheological properties, and syneresis of yogurt. The effect of a negatively charged, capsular exopolysaccharide produced by Streptococcus thermophilus and a neutral, non-capsular exopolysaccharide produced by Lactococcus lactis were investigated. Using quantitative microstructural analysis, we examined yogurt samples prepared with either the capsular or the non-capsular exopolysaccharide, and with mixtures of the two. Confocal laser scanning microscopy and stimulated emission depletion microscopy were employed to visualize the microstructures, revealing differences in pore size distribution, protein domain size, and casein interconnectivity that were not apparent through visual inspection alone. Additionally, variations in rheological properties were observed among the different yogurt types. In the yogurt fermented with both bacterial strains, we observed a combined impact of the two exopolysaccharide types on relevant microstructural and rheological properties. The negatively charged capsular exopolysaccharide enhanced casein interconnectivity and gel stiffness, while the neutral non-capsular exopolysaccharide led to thicker protein domains, an abundance of small pores, and a lower loss tangent. These factors collectively hindered syneresis, resulting in improved structural integrity. Our study not only provides valuable insights into the influence of different exopolysaccharides on yogurt properties, but also presents the first demonstration and quantification of the effect of multiple types of exopolysaccharides on casein interconnectivity. These findings offer guidance for the production of yogurts with customized microstructure, rheological properties, and resistance to syneresis.

Isolation of Lactic Acid Bacteria from Local Yogurt Samples in Chaharmahal and Bakhtiari Province: The Assessment of Probiotic Characteristics

Isolation of Lactic Acid Bacteria from Local Yogurt Samples in Chaharmahal and Bakhtiari Province: The Assessment of Probiotic Characteristics

Identification of Previously Unrecorded Bacills, Serratia, and Mucor Strains Isolated from Yogurt

(1) Background: Foodborne illnesses are recognized as a significant threat to public health and the economy in both developed and developing nations. The safety of foods containing microorganisms has consequently become a major worldwide concern. One of the most frequent causes of food deterioration in the world is microbial contamination. (2) Methods: Yogurt containers that were bought commercially in Riyadh, Saudi Arabia during their validity period contained four different species of bacteria and one type of fungus. Using nutritional agar and Czapek-Dox agar medium, the bacteria and fungi were isolated. The isolates of the fungi and bacteria were identified using a scanning microscope. The isolates were further identified and classified for molecular evolutionary analyses using the 16S rRNA and ITS sequences from the bacteria and fungi, respectively, in conjunction with the universal primers 27F, 1492R, ITS1F, and ITS4R. (3) Results: A total of 131 separate strains were identified from 12 yogurt samples based on their phenotypic characteristics. In total, 79 isolates (60.3%) consisted of Serratia marcescens, Bacillus subtilis, and Mucor circinelloides, with 52 isolates (39.7%) being Bacillus cereus. While the cells of Bacillus and Serratia are shaped like rods, the sporangia of Mucor are large, round, and black. Each strain was identified by its accession number, which were as follows: MK590996.1: B. cereus; MK591144.1: B. subtilis; MK591002.1 and MK591014.1: S. marcescens; and MK559692.1: M. circinelloides. The maximum identification was found to be between 98.64 and 100% when BLAST was used to compare the sequences to the NCBI GeneBank database. (4) Conclusions: Genus and species identification was performed using the similarity score values. Yogurt products containing high concentrations (39.7%) of Bacillus cereus isolates carry a significant risk of health hazards due to the potential for spreading pathogenic bacteria to humans.

Effect of roasting and high-pressure homogenization on texture, rheology, and microstructure of walnut yogurt

The effect of roasting and high-pressure homogenization on the quality of yogurt made from peeled walnut kernels was explored in this study. The G' and G'' values of yogurt made from walnuts roasted at high temperatures were reduced. The water-holding capacity and hardness of walnut yogurt were reduced to 47.73% and 24.22 g, respectively. Increasing the homogenization pressure reduced the particle size of the walnut yogurt to 20.50 μm. Homogenized walnut milk at 150 MPa increased the viscosity, hardness, and consistency of yogurt product from 11.71 to 16.74 Pa.s, from 30.01 to 71.63 g and from 283.17 to 455.24 g·s, respectively. The confocal laser scanning microscope observation demonstrated a reduction in the size of fat and protein micelles in the homogenized yogurt samples, resulting in a compact structure. This study will contribute valuable scientific insights to the advancement of plant-based yogurt quality.

Yoghurt quality when using probiotic starter cultures and vegetable filler

In order to increase the biological value of yogurt, increase and improve its assortment, it is necessary to continue the search and use of new additives and fillers of natural origin. Such fillers should be well combined with the milk base, contain mineral elements, vitamins and other biologically active substances. The article substantiates the use of bacterial starters and vegetable filler in yogurt technology. The results of studies on the use of dry bacterial starter cultures of direct application of the Ukrainian manufacturer of the “YOGURTON” trademark and the vegetable filler “Black currants dry extract of 30 % anthocyanins” in the production of yoghurt are presented. An evaluation of the prototypes showed that when using the Yoghurt Probio TM «YOGURTON» starter, the product had a more pronounced taste and smell. The time of clot formation, changes in titrated acidity, and organoleptic characteristics of yogurt with filler were studied. It was found that all samples of yogurt on organoleptic parameters meet the requirements of DSTU and high scores on the scoring system of fermented milk products. The tested starter cultures at a fermentation temperature range of 40 ± 2 °C form a clot for 6–8 hours with a titratable acidity of 75 °T. Yogurt with a content of dry currant powder in an amount of 1 % in terms of organoleptic characteristics turned out to be the best; with an increase in the content of currant powder in yogurt up to 1.5 %, an increase in the taste of currants and a decrease in the characteristic sour milk taste of the product were noted. High acidity gives the product a sour taste and smell, which reduces its organoleptic characteristics. The acidity of yogurt with a filler content of 1 % was 116 °T on the first day of storage and increased to 140 °T for ten days. During storage of yogurt at the temperature of +6 ± 2 °C there is a gradual increase in lactic acid microorganisms, which affects the organoleptic characteristics of yogurt. “Black currant extract dry 30 % anthocyanins” enriches yogurt with anthocyanins, flavonoids, organic acids, pectin, which improve the taste and quality of the product.

Technology of fermented milk product with increased protein content

The article contains the results of research into the development of yogurt technology with a high protein content and added Jerusalem artichoke syrup. Milk protein contains casein and whey protein, so it is a valuable source of protein. Modern technologies make it possible to separate and purify a specific type of milk proteins to a concentration that meets the technological requirements that are necessary in food systems. The low glycemic index and probiotic properties has a Jerusalem artichoke syrup, it has a positive effect on the development and stability of lactic acid bacteria and is recommended for consumption by people with diabetes. The biological value of the whey isolate was studied and it was established that the content of essential amino acids is 47.7 g per 100 g of the product, or 48.4 % of the total amount of amino acids. The content of BCAA (leucine, isoleucine and valine) is 23 g, which is 23.3 % of the total amount of amino acids. It was found that lysine has the highest score (176.3 %), and the limiting amino acids are phenylalanine (50 %) and methionine (62.8 %). The sum of amino acids of the “ideal” protein according to the recommendations of FAO/WHO and whey protein isolate was compared, and it was determined that the protein content in the studied raw material is 460 mg, which exceeds the values of the “ideal” protein (360 mg) by 27.7 %. It has been experimentally established that the optimum from the point of view of the complex of organoleptic properties and cost of the product is the sample where the content of whey isolate is 7.2 g per 100 g of the product. The protein content per 100 g of finished yogurt is 10 g. During fermentation, a slight difference in the rate of change of acidity in yogurt samples was noted, which was 4.5 h (75 °T) in the experimental sample and 5 h in the control sample. The shelf life of the product is set for 12 days according to titrated acidity levels for 21 days. According to the organoleptic indicators of yogurt, the difference between the tested and the control sample was noted. Yogurt, with added protein and Jerusalem artichoke syrup, was rated highest for taste, smell, and consistency, but not rated high enough for appearance and color. Regarding the biological value of the product, the protein content is 10 %, the fat content is 2.5 %, and the carbohydrate content is 8.3 %. The energy value of yogurt with additional ingredients is 84.4 kcal per 100 g of product.

Effects of mulberry pomace polysaccharide addition before fermentation on quality characteristics of yogurt

Mulberry pomace, a by-product of mulberry juice processing, is rich in natural bioactive substances including polysaccharides and polyphenols and is useful for the production of functional foods. As such the effects of mulberry pomace polysaccharide (MPP) on physicochemical, textural and microstructural features of yogurt during cold storage were investigated. MPP was incorporated into reconstituted skim milk at 0% (control), 0.5%, 1.0% and 1.5%, respectively and then fermented to yogurt and stored at 4 °C for 28 days. The color, pH, titratable acidity, syneresis, rheology, texture and microstructure of yogurt samples were analyzed. The addition of MPP before fermentation dose-dependently affected the pH value and titratable acidity of yogurt samples such that the addition of 0.5% MPP showed the most significant effect in reducing syneresis, increasing gel strength and viscosity, and improving texture and microstructure of yogurt. The results indicate that the appropriate amount of MPP can effectively improve the gel properties and physicochemical parameters of yogurt, and MPP played an important role in the yogurt quality improvement by mulberry pomace.

An oxygen-insensitive amperometric galactose biosensor based on galactose oxidase co-immobilized with an Os-complex modified redox polymer

Monitoring galactose levels in dairy products can help to prevent severe complications with a hereditary metabolic disease such as galactosemia, a life-threatening disease. The current state of the art requires the development of less expensive, more reliable and specific methods to determine galactose levels in food in a practical way. We report the development and optimization of an amperometric biosensor for determination of galactose in dairy products based on galactose oxidase (GaOx) co-immobilized with an osmium-complex modified redox polymer on glassy carbon electrodes. To attain the maximum catalytic currents based on mediated electron transfer, two Os-complex based polymers with different redox potentials and different enzyme:redox polymer ratios were studied. The optimized GaOx-modified electrode gave a maximum electrocatalytic response of galactose oxidation that was not affected by the presence of O2, indicating fast wiring of the enzyme by the Os-complex modified redox polymer. The biosensor that gave the best analytical parameters for galactose detection was further tested for measuring galactose concentration in lactose-containing and lactose-free milk and yogurt samples under aerobic conditions. The results obtained with the amperometric biosensor were validated by high-performance anion-exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD).

Physicochemical properties and survival assessment of potential probiotics in a novel dairy drink during storage.

A novel fermented dairy drink utilizing microbial strains displaying potential probiotic attributes was formulated. The study constituted several experimental cohorts, including Lactiplantibacillus plantarum AB6-25, isolated from a human stool sample; Lacticaseibacillus casei K2, sourced from a koumiss sample; Lacticaseibacillus rhamnosus 3B7, derived from a traditional yogurt sample; and identical lactic acid bacteria (LAB) in combination with yeast (Saccharomyces boulardii T8-3C from chicken feces) strains. Two distinct iterations of probiotic-fermented dairy drinks were generated by introducing subcultured microorganism cultures: LAB strains at a concentration of 1% each (designated as combination A) and a blend of LAB strains at 1% each along with T8-3C at 0.5% (designated as combination B) into both whole and semi-skimmed milk matrices. The fermentation process persisted until the pH reached 4.6 under constant conditions of 37 ± 1°C. Subsequently, the samples were held at 4 ± 1°C for 15 days. The groups' physicochemical, microbiological, and sensory characteristics were determined on days 1, 8, and 15 of storage, and the protein profile was determined. Standardized regression analysis and principal component analysis evaluated the results. Fat content affected the changes in dry matter. pH decreased in all samples during storage, particularly in the yeast group. The microorganism group positively affected syneresis, whereas fat content and the interaction of fat content and the microorganism group had a negative effect. The most critical factor in the decrease in syneresis was the increase in fat content. LAB and yeasts maintained their probiotic effects during storage, with a viability level of approximately 109 and 108 cfu/mL, respectively.

Influences of Yogurt with Functional Ingredients from Various Sources That Help Treat Leaky Gut on Intestinal Barrier Dysfunction in Caco-2 Cells.

The impact of yogurts made with starter culture bacteria (L. bulgaricus and S. thermophilus) and supplemented with ingredients (maitake mushrooms, quercetin, L-glutamine, slippery elm bark, licorice root, N-acetyl-D-glucosamine, zinc orotate, and marshmallow root) that can help treat leaky gut were investigated using the Caco-2 cell monolayer as a measure of intestinal barrier dysfunction. Milk from the same source was equally dispersed into nine pails, and the eight ingredients were randomly allocated to the eight pails. The control had no ingredients. The Caco-2 cells were treated with isoflavone genistein (negative control) and growth media (positive control). Inflammation was stimulated using an inflammatory cocktail of cytokines (interferon-γ, tumor necrosis factor-α, and interleukin-1β) and lipopolysaccharide. The yogurt without ingredients (control yogurt) was compared to the yogurt treatments (yogurts with ingredients) that help treat leaky gut. Transepithelial electrical resistance (TEER) and paracellular permeability were measured to evaluate the integrity of the Caco-2 monolayer. Transmission electron microscopy (TEM), immunofluorescence microscopy (IM), and real-time quantitative polymerase chain reaction (RTQPCR) were applied to measure the integrity of tight junction proteins. The yogurts were subjected to gastric and intestinal digestion, and TEER was recorded. Ferrous ion chelating activity, ferric reducing potential, and DPPH radical scavenging were also examined to determine the yogurts' antioxidant capacity. Yogurt with quercetin and marshmallow root improved the antioxidant activity and TEER and had the lowest permeability in fluorescein isothiocyanate (FITC)-dextran and Lucifer yellow flux among the yogurt samples. TEM, IM, and RTQPCR revealed that yogurt enhanced tight junction proteins' localization and gene expression. Intestinal digestion of the yogurt negatively impacted inflammation-induced Caco-2 barrier dysfunction, while yogurt with quercetin, marshmallow root, maitake mushroom, and licorice root had the highest TEER values compared to the control yogurt. Yogurt fortification with quercetin, marshmallow root, maitake mushroom, and licorice root may improve functionality when dealing with intestinal barrier dysfunction.

Investigation of the Physiochemical and Microbiological Quality of Fruit Yoghurt Sold in Elazig Province

This study was conducted to determine some quality parameters of 25 fruit yoghurt samples (strawberry, forest fruit, blueberry, apricot, fig, mango, peach) sold in Elazig province. For this purpose, physicochemical (pH, acidity, fat, dry matter, starch, peroxidase, heat treatment) and microbiological [total mesophilic aerobic (TMA) bacteria, psychrotrophic bacteria, Lactobacillus-Leuconostoc-Pediococcus (LLP), lactic streptococcus, proteolytic and lipolytic microorganism, coliform, Enterobacteriaceae, Escherichia coli, Staphylococcus-Micrococcus, Staphylococcus aureus, Salmonella spp. and yeast-mold] analyzes of fruit yoghurt samples were performed. It was determined that 14 samples (8%) did not comply with the Turkish Food Codex Fermented Dairy Products Communiqué and TSE yoghurt standard regarding acidity value (% l.a.). The presence of starch in 91 (52%), peroxidase in 91 (52%) and heat treatment tests in 147 (84%) of the samples were positive. In the 161 (92%) samples coliform, Enterobacteriaceae and Staphylococcus-Micrococcus; and in the 154 (88%) of yeast and mold microorganisms were observed to be less than &lt;1.0 log10 cfu/g of. Total psychrophilic bacteria, E. coli, Staphylococcus aureus, and Salmonella spp. have not emerged in any of these samples (&lt;1.0 log10 cfu/g). There is only a statistical significance observed in Proteolytic bacteria between fruit yoghurt groups (P &lt; 0.05). The lowest number (5.36 ± 0.10 log10 cfu/g) of proteolytic bacteria was observed in forest fruit; the highest (7.02 ± 0.52 log10 cfu/g) was determined in yoghurt with figs. As a result, it was concluded that the microbiological quality of the examined fruit yoghurt samples was not adequate for the hygienic conditions. It is thought that hygienic conditions were not considered during the production process and it could pose a risk to public health.

Development of a Multiplex PCR Assay for Efficient Detection of Two Potential Probiotic Strains Using Whole Genome-Based Primers.

Probiotics are microorganisms that exert strain-specific health-promoting effects on the host. Τhey are employed in the production of functional dairy or non-dairy food products; still, their detection in these complex matrices is a challenging task. Several culture-dependent and culture-independent methods have been developed in this direction; however, they present low discrimination at the strain level. Here, we developed a multiplex PCR assay for the detection of two potential probiotic lactic acid bacteria (LAB) strains, Lactiplantibacillus plantarum L125 and Lp. pentosus L33, in monocultures and yogurt samples. Unique genomic regions were identified via comparative genomic analysis and were used to produce strain-specific primers. Then, primer sets were selected that produced distinct electrophoretic DNA banding patterns in multiplex PCR for each target strain. This method was further implemented for the detection of the two strains in yogurt samples, highlighting its biotechnological applicability. Moreover, it can be applied with appropriate modifications to detect any bacterial strain with available WGS.

Rapid prediction of the aroma type of plain yogurts via electronic nose combined with machine learning approaches

The unique aroma attributes of yogurts are associated with their quality and consumer acceptance. However, the aroma types of plain yogurts and methods for quickly identifying them have not been systematically established. This study used quantitative descriptive analysis (QDA) to label the aromas of commercial plain yogurts into four primary types, namely fermented, cheesy, milky, and fruity, for the first time. Electronic nose (e-nose) data were rapidly collected from the headspace of plain yogurt samples, and the aroma types classification models were established using linear discriminant analysis (LDA), logistic regression (LR), support vector machine (SVM), and decision trees (DT). Among these models, the SVM-based model displayed the best classification performance, with accuracy and F1 values at 0.933. Furthermore, this study revealed that the LR classification model, based on refined smaller-size e-nose datasets, improved the accuracy and F1 values to 0.867 and 0.872, respectively, compared to the original LR model using the complete dataset, thus demonstrating the applicability of model simplification. This work provides a theoretical basis for rapid plain yogurt aroma type identification by combining e-nose data with machine learning approaches.

Occurrence of Aflatoxin M1 in yogurt samples found in markets in Kosovo during spring 2023

Aflatoxin M1 (AFM1), a toxic byproduct of aflatoxin B1 (AFB1) produced by Aspergillus fungi, is a carcinogenic mycotoxin that can contaminate various agricultural commodities. It can be transferred from AFB1-contaminated feed to milk and dairy products, including yogurt, posing a potential health risk to consumers. In spring 2023, a total of 74 yogurt samples were collected from the largest food suppliers in Kosovo for analysis, including samples produced in Kosovo and seven other countries: Albania, North Macedonia, Bosnia and Herzegovina, Slovenia, Greece, Italy, and Germany. A rapid and sensitive analytical method, Enzyme-linked immunosorbent assay (ELISA), was used for the analysis. The results of the study highlight discernible differences in the maximum tolerable levels of AFM1 between the countries. More specifically, yogurt samples from Slovenia and Germany had lower levels than those from other countries. Additionally, the median levels of AFM1 in samples from Slovenia and Germany were significantly lower. The mean concentrations of AFM1 in yogurt samples from Kosovo and other countries were 0.071 μg/kg and 0.080 μg/kg, respectively. Out of all samples, 66 (89%) exceeded the maximum tolerable limit of 0.05 μg/kg. Among the exporting countries, Albania had the highest median AFM1 level of 0.085 μg/kg and the highest maximum level of 0.195 μg/kg. Slovenia had the lowest median AFM1 level, while Germany had the lowest maximum AFM1 level. All samples from Albania, Greece, and Bosnia and Herzegovina exceeded the maximum tolerable limit. High prevalence was also observed in samples from Kosovo, North Macedonia, and Slovenia. Considering the average daily consumption of about 250 grams of yogurt, and the total median value of Aflatoxin M1 concentration (0.071 μg/kg), the estimated daily intake was calculated to be 0.017 μg. These findings highlight the importance of monitoring and enforcing regulatory limits to ensure yogurt safety and to protect public health. Efforts should be focused on mitigating AFM1 contamination and implementing measures to minimise its presence in dairy products, especially in regions where levels exceed the established limits.

Volatile compounds, antioxidant activity, ACE inhibitory activity, HMF content and microstructure of fruit yoghurts

Stirred-type fruit yoghurts with two different fruit purees (kiwifruit and banana) were produced and were investigated the physicochemical, volatile compounds, 2,2-diphenylpicrylhydrazyl (DPPH) free radical scavenging activity, cupric ion reducing capability (CUPRAC), total phenolic compounds (TPC), angiotensin-converting enzyme (ACE) inhibitory activity, 5-hydroxymethylfurfural (HMF) content, reducing sugar content and microstructure. The addition of fruit puree affected (p&lt;0.01) total solids, fat, protein, ash, L*, a*, b*, volatile compounds, DPPH, CUPRAC, TPC, ACE inhibitory activity, HMF content, reducing sugar content and overall acceptability whereas it had an insignificant effect on the pH, titratable acidity, apparent viscosity, syneresis (p&gt;0.05). Storage period significantly (p&lt;0.01) affected the titratable acidity, DPPH, CUPRAC, TPC, ACE inhibitory activity, HMF content, reducing sugar content and overall acceptability, as well as the pH, apparent viscosity and a* (p&lt;0.05). Although the addition of banana and kiwi relatively suppressed the characteristic flavour of the experimental yoghurt samples, it improved the DPPH, CUPRAC and TPC. On the other hand, the addition of banana-kiwi was found to increase the content of HMF, the toxic compound. Yoghurt can be recommended as an important source of bioactive compounds with ACE inhibitory activity. According to the microstructure analysis results, a more homogeneous structure was observed in the control group samples compared to the fruit-added yoghurt samples and it was determined that the serum pore diameters were smaller.

Tahran, İran'da yüksek performanslı sıvı kromatografi ile süt ve süt ürünlerinde aflatoksin M1 içeriğinin değerlendirilmesi

Aflatoxin M1 (AFM1) is the most important aflatoxin in milk and dairy products, which is carcinogenic and hepatotoxic. This study aimed to evaluate the AFM1 content in the milk and distributed dairy products in Tehran. 75 samples, including 15 samples of raw milk, 15 samples of pasteurized milk, 15 samples of ultra-high temperature milk, 15 samples of pasteurized yogurt, and 15 samples of pasteurized cheese, were collected from October to December 2020 in Tehran by simple random sampling. The dietary exposure or estimated dietary intake (EDI) and hazard index (HI) were calculated for milk and dairy product consumers. The AFM1 content in the samples was determined by using high-performance liquid chromatography (HPLC) along with a fluorescence detector. AFM1 was observed in all samples. The values of AFM1 in all samples were higher than the acceptable range determined by the European Union. 100% of milk and yogurt samples and 82% of cheese samples exceeded the Iranian maximum limit (100 ng kg-1 in milk and yogurt, and 250 ng Kg-1 in cheese). Mean AFM1 content in raw milk samples, pasteurized milk samples, UHT milk samples, pasteurized yogurt samples, and pasteurized cheese samples were 337±17.7, 306±15.5, 305±17.4, 320±17.6, and 309±18.5 ng Kg-1, respectively. The highest value of HI was observed in children of Tehran, Iran. Based on the results, the aflatoxin content in milk and distributed dairy products in Tehran in the autumn is inconvenient. It is recommended that the aflatoxin levels should be measured at different times of the year, especially in raw milk, and feed monitoring is intensified for contamination with toxin-producing molds.

Development and properties of functional yoghurt enriched with postbiotic produced by yoghurt cultures using cheese whey and skim milk.

This study aimed to examine the effects of supplementation of postbiotics derived from Streptococcus thermophilus (ST) and Lactobacillus delbrueckii subsp. bulgaricus (LB) in cheese whey (CW) and skim milk (SM) on antioxidant activity, viability of yoghurt starters, and quality parameters of low-fat yoghurt during 22 days of storage. The LB-CW (L delbrueckii ssp. bulgaricus postbiotic-containing cheese whey) sample exhibited the highest antioxidant activity, with 18.71% inhibition (p > 0.05). This sample also showed the highest water holding capacity (77.93%; p < 0.05) and a trend toward receiving the most favorable sensory attributes (p > 0.05) compared to the other samples. The LB-CW and LB-SM yoghurt samples exhibited significantly higher body and texture scores compared to the ST-SM-fortified yoghurt (p < 0.05). However, there was no significant difference in the overall acceptability of the LB-SM and ST-SM yoghurt samples across both starters (p > 0.05). Such findings highlight the potential of postbiotics as functional ingredients to enhance the nutritional and sensory aspects of yoghurt, further contributing to its appeal as a health-promoting product.