Fermented Milk Samples Research Articles

Preliminary study on kinetics of pyroglutamic acid formation in fermented milk

Pyroglutamic acid (pGlu) influences the aromatic and sensory properties of foods and has several benefits for human health. The presence and kinetics of pGlu formation in fermented milk samples were investigated from a chemical point of view. Plain yoghurt, kefir and other probiotic fermented milk products available on the market were analysed to quantify lactic acid and pGlu. The pGlu concentrations in fermented milks ranged from 51.65 to 277.37 mg 100 g−1 dry matter. Laboratory-scale fermented milk was produced, and samples were taken at different times of fermentation and storage to construct the kinetics curve. At the beginning of the fermentation process, pGlu was already present in UHT milk (188.69 mg 100 g−1 dry matter) used to elaborate fermented milk, and its content increased not only during fermentation but during storage as well, reaching up to 403.56 mg 100 g−1 dry matter after 30 days.

DETERMINATION OF FLOW AND VISCOELASTIC PROPERTIES OF THE KYRGYZ ETHNIC FOOD “SÜZMÖ” DEPENDING ON TEMPERATURE AND MOISTURE CONTENT

Consumer interest in concentrated protein-rich food is growing. Kyrgyz traditional food Süzmö, which is a highly viscous dairy product that is produced from fermented milk Ayran, needs to be introduced into the dairy industry. In this study, the rheological parameters of this indigenous food product were investigated in steady and dynamic rheological experiments. The flow behaviours of Süzmö were evaluated at six temperatures (20, 30, 40, 50, 60, and 70°C) and suitable rheological models were found. The flow curves of Süzmö at investigated temperatures have the yield stress (τ0) values between 32.64 Pa and 285.87 Pa. The flow properties of Süzmö samples at 20 and 30°C correspond to the Bingham model. The Casson model was suitable for describing flow curves at 40, 50, 60, and 70°C with correlation coefficients R=0.9506 ‒ 0.9973. The effective viscosity (ƞeff) of Süzmö decreased from 15.88 to 0.26 Pa·s with increasing temperature from 20 and 70°C. The effect of temperature on the viscosity corresponds to the Arrhenius relationship. The calculated activation energy was 61.66 kJ/(mol). A linear model was defined taking into account the influence of moisture content (p>0.05) on effective viscosity (ƞeff) and yield stress (τ0). A temperature-sweep was performed at 20 to 80°C to determine the thermal denaturation of the fermented milk samples. The measured parameters are essential for the industrial production of Süzmö and other concentrated fermented milk products.

Assessment of Aflatoxin M1 Contamination in Egyptian Milk and Cheese تقييم تلوث اللبن والجبن في السوق المصري بالأفلاتوکسين M1

A screening survey of the presence of aflatoxin M1 (AFM1) was carried out on 170 samples of Egyptian dairy products. Selected samples included raw buffalo or cow milk, pasteurized milk, UHT milk, fermented milk, soft cheese, hard cheese, and processed cheese were analyzed by competitive ELISA technique. Out of 60 liquid milk and fermented milk samples analyzed, 12 samples (20%) were found to be contaminated with AFM1, at levels ranging from 10.12 to 86.54 ng/kg. Eight from the positive samples (66.6%) failed to reach the acceptable level of the European Commission Regulation (50 ng/kg). Buffalo’s milk is safe regarding AFM1 contamination since all the buffalo milk samples were consistently negative. AFM1 was found in 22 samples (36.67%) of out 60 cheese samples at concentrations between 25.12 to 253.04 ng/kg. The highest mean value of AFM1, 231.39 ng/kg, was found in Ras cheese (hard type) samples followed by the processed cheeses with 114.76 ng/kg. Kariesh cheeses displayed the lowest levels, 53.32 ng/kg. Cheeses made from cow’s milk showed higher AFM1 positive samples, while cheeses made from buffalo’s milk tested were consistently negative. Regarding the cheese ripening age, out of 50 cow milk cheese samples, 26 were found to be positive to AFM1. The highest positive incidence was noted in long-term ripened hard cheeses (70%), while the lowest in fresh unripened cheeses (40%). It is highly recommended from the results that milk and cheese products have to be controlled periodically for AFM1 contamination.

Effects of Fructose and Oligofructose Addition on Milk Fermentation Using Novel Lactobacillus Cultures to Obtain High-Quality Yogurt-like Products.

The incorporation of prebiotics in fermented milk products is one of the best ways to promote health benefits while improving their sensory characteristics at the same time. The aim of this study was to evaluate the effects of the addition of fructose and oligofructose (1% and 2%) on the physicochemical, rheological, sensory, and microbiological quality attributes of fermented milk products inoculated with indigenous probiotic starter cultures of Lactobacillus isolated from Polish traditional fermented foods. The samples were evaluated during 35 days of refrigerated storage. The oligofructose and fructose caused increases in the populations of bacteria in comparison to the control fermented milk products without the addition of saccharides. The degrees of acidification in different fermented milk samples, as well as their viscosity, firmness, syneresis, and color attributes, changed during storage. The highest overall sensory quality levels were observed for the samples supplemented with L. brevis B1 and oligofructose. This study is the first attempt to compare the influences of different sugar sources on the physicochemical, rheological, sensory, and microbiological quality attributes of fermented milk products.

Metabolomic profile of milk fermented with Streptococcus thermophilus cocultured with Bifidobacterium animalis ssp. lactis, Lactiplantibacillus plantarum, or both during storage

In this study, the microbial interactions among cocultures of Streptococcus thermophilus (St) with potential probiotics of Bifidobacterium animalis ssp. lactis (Ba) and Lactiplantibacillus plantarum (Lp) in fermented milk were investigated during a storage period of 21 d at 4°C, in terms of acidifying activity (pH and titratable acidity), viable counts, and metabolites. A nontargeted metabolomics approach based on ultra-high-performance liquid chromatography coupled with mass spectrometry was employed for mapping the global metabolite profiles of fermented milk. Probiotic strains cocultured with St accelerated milk acidification, and improved the microbial viability compared with the single culture of St. The St-Ba/Lp treatment manifested a higher bacteria viability and acidification ability in comparison with the St-Ba or the St-Lp treatment. Relative quantitation of 179 significant metabolites was identified, including nucleosides, AA, short peptides, organic acids, lipid derivatives, carbohydrates, carbonyl compounds, and compounds related to energy metabolism. The principal component analysis indicated that St treatment and coculture treatments displayed a complete distinction in metabolite profiles, and Lp had a larger effect than Ba on metabolic profiles of fermented milk produced by cofermentation with St during storage. The heat map in combination with hierarchical cluster analysis showed that the abundance of metabolites significantly varied with the starter cultures over the storage, and high abundance of metabolites was observed in either St or coculture samples. The St-Ba/Lp treatment showed relatively high abundance for the vast majority of metabolites. These findings suggest that the profile of the metabolites characterizing fermented milk samples may depend on the starter cultures, and incorporation of probiotics may considerably influence the metabolomic activities of fermented milks.

The Functionality of African Streptococcus Thermophillus and Streptococcus Infantarius Sub Sp. Infantarius in Milk Fermentation

Fermentation serves a key role in inhibiting spoilage microorganism through acidification and production of antimicrobial compounds. The technological information on properties of Streptococcus infantarius sub sp. infantarius which is predominant in most African fermented is dairy products very little. This study was therefore carried out to determine the functionality of selected African Streptococci strains in fermented dairy products. Pasteurized milk samples from camels and cows were inoculated with different strains and a selected combination at a rate of 3% v/v and incubated at different temperatures of 25 oC, 30 oC, 37 oC, and 45 oC for 9 hours. Analysis was done after every 3 hours for pH and titratable acidity while viscosity was done after incubation and cooling of the product. The different fermented milk samples were subsequently evaluated for consumer acceptability. Milk inoculated with both African type Streptococcus thermophillus (146A8.2) and Streptococcus infantarius sub sp. infantarius CJ 18 (9377), and incubated for nine hours recorded the highest amount of titratable acidity of 0.97 for the camel milk and had the least pH value of 4.12 for cow milk compared to the other strains. The cow milk had the highest viscosity level of 59.64 cPs compared to camel milk which was 29.44 cPs. The levels of titratable acidity and viscosity depended on the strain and incubation temperature. The African type Streptococcus thermophillus (146A8.2) and Streptococcus infantarius sub sp. infantarius CJ 18 (9377), isolated from fermented camel milk had good technological properties that are useful as starter culture for development of fermented milk products.

Identification and Evaluation of Preservative Plants on Traditionally Fermented Cow Milk

The majority of communities in different regions of Ethiopia are relying on a variety of plants to improve the quality of their dairy products. However, this cultural perception was scientifically not well strengthened. Therefore, the objectives of the study were to identify milk preservative plants and evaluate the effects of preservative plants on fermented milk redox potential, Potential hydrogen (pH), and sensory analysis. The survey study was conducted on purposefully selected 80 households in the Haramaya district. However, the laboratory study was conducted on four top-ranked plants for the preparation of fermented milk samples at ambient temperature following similar techniques and procedures observed at households. All the collected data were analysed by Statitsical Analysis software (SAS). In the study area, five plants in the families of Oleaceae, Celastraceae, Lamiaceae, and Rutaceae were identified and used by the majority of respondents with perceptions of enhancing the flavour of their products. The Analysis of variance (ANOVA) results of redox potential were proved the cultural perception of the majority of respondents that they were used both Olea Africana and Catha edulis in substitute to each other for the same purpose. The pH of all treatments was continuously decreased and the milk samples treated by Olea Africana and Catha edulis were recorded the lowest values at the end. The observed pH results have disproved the communities cultural perceptions that they believed smoking increased the shelf life and extended the fermentation time whereas the Hedonic scores of panelists proved the local perceptions of respondents that they were mainly intended to make their products much more acceptable and preferable by its flavour to the consumers.

Dendrobium candidum extract on the bioactive and fermentation properties of Lactobacillus rhamnosus GG in fermented milk

Dendrobium candidum has a long medicinal history and good nutritional value. It has been used in the health food industry. However, the effect of D. candidum on the biological activity and the fermentation of probiotics need further study. This study evaluated the effect of D. candidum extract (DCE) on the chemical, viable bacteria count, and acid production capacity of milk fermented using probiotics. The tolerance of Lactobacillus rhamnosus GG (LGG) to simulated gastrointestinal fluids, the ability of the strain to scavenge free radicals, adhesion capacity, and antibacterial activity were measured. The differences in volatile flavor substances and sensory properties of fermented milk with and without DCE added were measured. The results showed that DCE supplementation increased the use of proteins and carbohydrates by LGG, and rate of carbohydrate using LGG increased by 25%. The growth and acid production ability of the strain were increased. The number of viable bacteria in the fermented milk with DCE supplementation was >8.5 log CFU/mL, and the survival rates of LGG in simulated gastric and intestinal juices were improved. O2− and hydroxyl radicals in the fermented milk samples with DCE added were significantly decreased. In addition, DCE did not significantly affect the flavor quality of fermented milk. DCE supplements are a promising type of transfer protection agent.

Isolation and identification of fungi found in contaminated fermented milk and antifungal activity of vanillin

Fungi contamination is an important factor affecting the quality and commercial value of fermented milk. Vanillin is known as a safe and efficient natural antimicrobial additive with great potential value as a food bio-preservative. In this study, the microbiological quality of fermented milk of different brands retailed in China and the antimicrobial activity of vanillin were investigated. A total of 27 fermented milk samples were purchased and evaluated. Fungal isolates obtained were characterized by DNA sequencing of the internal transcribed spacer (ITS) region. The effects of vanillin on the growth of fungi were studied by plate dilution method, radical colony diameter, and mycelium biomass. The result showed that 14.8% of the samples were contaminated with three different species of fungi with Cladosporium spp. being the most predominant fungal contaminant. The study further showed that vanillin had significant inhibitory activity against the growth of the fungi species. The cell number, radical colony diameter, and the mycelium biomass of the fungal contaminant were significantly reduced by the inhibitory action of the vanillin. The study thus provides reliable data evidence that will help relevant stakeholders in the fermented milk industries to improve their quality control strategies and consider vanillin as a bio-preservative with the potential to increase the shelf-life and safety of fermented milk.

Physicochemical Properties, Proximate Composition and Total Viable Counts of Staphylococcus aureus in ‘Nono‘ And Yoghurt Samples in Kaduna, Nigeria

The study aims at determining the physicochemical, proximate composition and the total viable count of Staphylococcus aureus in ‘Nono‘ and yoghurt samples in Kaduna, Nigeria.Three hundred and eighty-four (384) fermented milk samples (Nono and yoghurt) were obtained from different selling points and were evaluated for the occurrence of S. aureus. The physicochemical and proximate analyses (pH, total titratable acidity, moisture content, ash content, protein content, and fat content) were determined. The results of the analyses showed that Nono had pH range of 3.56-3.61, total titratable acidity: 0.71-1.72, moisture content: 82.23-83.87%, ash content: 0.30-0.31%, crude protein content: 1.50-1.61%, crude fat content: 0.35-0.38 %. For yoghurt, the pH ranged from 3.76 -3.82, total titratable acidity: 1.10 -1.15, moisture content: 77.76-80.06%, ash content: 0.68- 0.70%, crude protein content: 3.40-3.45% and crude fat content: 1.76-1.79% from all the study areas. One hundred and four of the total samples were contaminated with S. aureus. Out of the 104 isolates of S. aureus that were isolated and identified, 88 were coagulase positive S.aureus. The Microgen Staph ID kit (Oxoid) was used to further confirm the characteristics of the 60 isolates of the coagulase positive S. aureus. The kit confirmed 43 isolates as S. aureus, the results indicated the presence of S. aureus in the milk samples which is of public health importance, as this can contribute to food-borne intoxication which can lead to food poisoning. There is a need for proper pasteurisation of raw milk to help eradicate S. aureus infection before human consumption.

Characterization of the relationship between olfactory perception and the release of aroma compounds before and after simulated oral processing

Aroma is an important property of fermented milk, and it directly affects consumer acceptance. However, previous studies have mainly focused on analyzing the composition of aroma compounds in fermented milk in vitro, and the composition may be different from the real aroma composition that stimulates the sense of smell. Furthermore, the relationship between olfactory attributes and the release of aroma compounds was not fully understood. In this study, we selected 6 samples of fermented milk differing in aroma perception intensity based on our pretest. A descriptive sensory analysis focusing on orthonasal and retronasal olfaction of fermented milk was first conducted by semitrained panelists. Artificial saliva was mixed with the fermented milk samples and continuously stirred at 37°C for 15 s to simulate oral processing conditions. Headspace solid-phase microextraction-gas chromatography coupled with quadrupole time-of-flight mass spectrometry was applied to identify the head space composition of 6 kinds of fermented milk before and after the simulated oral processing. Twenty-five volatile compounds were identified in the fermented milks, 15 of which were predicted to have an influence on the olfactory perception of fermented milks during oral processing. Partial least squares regression analysis based on chemical and sensory data was then applied to explore the correlation between sensory perception and volatile aroma release. The results showed that oral processing greatly increased the perception of creamy aroma compounds, such as diacetyl and acetone, but did not increase the perception of dairy sour aroma compounds, such as butanoic acid and hexanoic acid. This study can help improve our understanding of the relationship between olfactory perceptions and the release of volatile aroma compounds under oral processing. It might also contribute to the design of palatable fermented milks catering to specific consumer preferences.

Carbonate and silicate dissolving bacteria isolated from home-made yogurt samples.

In the current study, twenty-eight bacterial strains were isolated from home-made yogurt samples from Ağrı Province, Turkey. The bacterial strains were identified by conventional and molecular techniques. Among the twenty- eight isolates, seventeen isolates were identified according to the 16 S rDNA region and determined to belong to five different genus including Sphingomonas (8 isolates), Burkholderia (5 isolates), Lactobacillus (2 isolates), Lactococcus (1 isolate), Staphylococcus (1 isolate). In this study, the presence of Burkholderia in home-made yogurt samples were reported for the first time, whereas Sphingomonas was detected for the second time. We also investigated the carbonate (CaCO3 and MgCO3) and silicate (‎CaSiO3 and MgSiO3) dissolving potential of seventeen bacterial isolates. Among these seventeen bacterial isolates, fifteen bacterial isolates have CaCO3-dissolving and 10 bacterial isolates have MgCO3-dissolving potential. The silicates dissolution ability was relatively less than that of carbonates dissolving. We observed that six bacterial isolates have CaSiO3 and only two bacterial isolates have MgSiO3 dissolution abilities. In conclusion, this work clearly shows the diversity of bacteria existing in fermented cow milk samples in Ağrı Province, Turkey, which could be considered as valuable sources for lactic acid bacteria (LAB) isolation and further probiotic potential.

Effect of different fat levels on physicochemical, sensory and microbiological attributes of fermented laban milk

ABSTRACT The present study analyses the effect of storage time and varying fat levels in fermented laban milk samples obtained from different sources through physicochemical, sensory and microbiological attributes. The milk samples were divided into three groups (T1 = Buffalo Milk, T2 = Cow Milk, T3 = Mixed Milk) with replication. Viscosity, acidity and syneresis of all three laban milk samples increased, whereas pH decreased significantly (P ≤ .05) across storage days. The viscosity, protein and total solids (TS) were significantly (P ≤ .05) decreased in all Laban milk samples with a 3.5% fat level compared to a 1.5% fat level at the 21st day of the storage period. The colour and appearance scores were unaffected for the T1 group but decreased with increased fat levels for T2 and T3 groups. The Total Plate Count tended to decrease with a 3.5% fat level in all three laban milk samples. However, days of storage had a non-significant effect. Buffalo laban milk seems best in terms of viscosity, protein, TS, taste and aroma. Furthermore, these attributes are affected by days of storage and fat level. The fermented laban prepared from mixed milk (T3) showed results at par with that from buffalo milk. Hence, considering the economical aspect, mixed milk laban at a fat level of 3.5% is highly recommended.

Development of Antioxidant and Antihypertensive Properties during Growth of Lactobacillus helveticus, Lactobacillus rhamnosus and Lactobacillus reuteri on Cow's Milk: Fermentation and Peptidomics Study.

Bioactive peptides derived from milk proteins are an active research area. Exhibiting numerous positive physiological effects on digestive, cardiovascular, immune and nervous systems, these peptides thought to be one of the most promising ingredients for functional food. Generally, these peptides are inactive within the parent proteins and can be liberated during milk fermentation by the specific proteolytic systems of various Lactobacillus spp. Here we present the study of milk fermentation by Lactobacillus helveticus NK1, Lactobacillus rhamnosus F and Lactobacillus reuteri LR1 strains. It was demonstrated that the antioxidant activity of the milk fermented by these strains concomitantly increased with the strains’ proteolytic activity. For the angiotensin I-converting enzyme (ACE) inhibitory activity, the same tendency was not observed. Although the proteolytic activity of L. helveticus NK1 was two times higher than that of L. rhamnosus F, the milk fermented by these strains showed comparable ACE inhibition. The analysis of the peptide profiles of the fermented milk samples allowed us to hypothesize that some previously unreported peptides can be produced by L. rhamnosus F. In addition, it was demonstrated that these potential ACE-inhibiting peptides originated from the C-terminus of αS2-casein.

In vitro screening of probiotic properties of Lactobacillus plantarum isolated from fermented milk product

Abstract Objectives The screening of traditional fermented products is essential for the assessment of safety, security, and further development of functional foods for the well-being of human health. The aim of the present study was to isolate and identify bacteria from fermented raw milk samples that exhibit health benefits upon consumption. Methods In order to confirm the isolates as probiotics, several in vitro assays were conducted to assess the probiotic properties of isolated bacteria. The initial screening includes tolerance to acid, bile, pancreatin, and NaCl. The cell surface properties demonstrate their interaction with mucosal epithelium, which includes hydrophobicity and auto-aggregation assay. Safety assessment was done by performing haemolytic test and antibiotic susceptibility test. The antagonistic activity of probiotic strain was further evaluated against some pathogenic bacteria. Results Lactobacillus plantarum (L. plantarum) isolated from fermented raw milk was preliminarily identified by biochemical tests and further confirmed using 16S rRNA identification. The isolate designated as L. plantarum strain GCC_19M1 demonstrated significant tolerance to low pH, 0.3% bile, 0.5% pancreatin, and 5% NaCl. In the presence of simulated gastric juice (at pH 3), the isolate exhibited a survival rate of 93.48–96.97%. Furthermore, the development of ecological niches in the human gut and their successful accumulation have been revealed by auto-aggregation and hydrophobicity properties. Absence of haemolytic activity ensures the non-virulent nature of the strain. Lactobacillus plantarum strain GCC_19M1 showed susceptibility towards gentamicin, tetracycline, kanamycin, meropenem, and ceftriaxone and exhibited an antagonistic effect on pathogenic bacteria. Conclusion The obtained results conveyed that L. plantarum strain GCC_19M1 has strong probiotic potential, and its presence in the fermented raw milk products may serve as a potent functional probiotic food.

Effect of some fermentation conditions on antibacterial activity of fermented milk by kefir grains

The present study aimed to investigate the effect of type of milk, fermentation time, temperature, and stirring conditions on the antibacterial activity of fermented milk by kefir grains. All fermentation conditions had a significant effect on the antibacterial activity of kefir samples against four bacteria, except for the effect of temperature on the diameter of the inhibition zone of Shigella dysenteriae. Considering all factors and their interactions, fermented samples in full-fat milk compared to nonfat milk, at 37°C compared to 25°C and under stirred conditions compared to non-stirred samples showed higher antibacterial activity. Also, fermented samples for 48, 72, and 120 hr showed higher antibacterial activity against Escherichia coli, Staphylococcus aureus, and Bacillus cereus, respectively, and fermented samples for 48 and 120 hr showed higher antibacterial activity against S. dysenteriae. Practical applications Several studies have investigated the antibacterial activity of kefir. But the novelty of the present study is that we have also investigated the effect of some fermentation conditions on the antibacterial activity of kefir samples. Furthermore, in this study, the interactions of these variables in the antibacterial activity of kefir samples using Design-Expert software have been analyzed. The fermentation conditions had a significant effect on the antibacterial activity of fermented milk samples. In general, to achieve the most of antibacterial activity, is recommended fermentation in full-fat milk, at 37°C, and under stirred conditions. In addition to these conditions, to achieve the most antibacterial activity against E. coli, S. aureus, B. cereus, and S. dysenteriae, is recommended fermentation times of 48, 72, 120, and 120 hr, respectively.

Microbiological quality and HACCP of nono production in a Fulani settlement, Zaria Kaduna state, Nigeria

This research studied the frequency of occurrence of Escherichia coli, Bacillus cereus, yeasts and moulds in some retail uncontrolled fermented milk samples (nono), and a hazard analysis was conducted to trace the sources of contamination during processing and suggest critical control measures. Fifty (50) nono samples purchased from Fulani milkmaids in Samaru market of Zaria town, Kaduna, Nigeria, were analyzed for presence of E. coli, B. cereus, Yeasts and Moulds. The traditional processing of nono by 3 producers of some of the market samples analyzed was studied by observing processing steps, processing environment, collecting raw and fermented milk samples, cow dung, hand swabs, swabs of milk contact surfaces, and exposing sterile plates to milking environment. Nono processing for all 3 producers involved spontaneous fermentation of fresh unpasteurized milk in calabashes at ambient temperature (25±40C) for 24 hours, fat separation from fermented milk, addition of water, whisking, packaging in calabashes and storing at ambient temperature before sale. Mean plate counts of market nono samples were at levels considered unsatisfactory for E. coli (≥ 102) in 76 %of samples, potentially hazardous for B. cereus (≥104) in 78% of samples and exceeded satisfactory limits for yeasts and moulds (<10) in all samples (100%). E. coli, B. cereus, yeasts and moulds were present in all 9 milk samples collected before and after fermentation during traditional processing. Yeasts and moulds were isolated from all samples (100%) during traditional processing except for wooden spoons (78%) and hand swabs (78%). Substandard practices like using unclean hands in manual milking and use of unpasteurized milk observed during traditional processing could explain presence of these microorganisms in market samples, as was also detected in raw and fermented milk during traditional processing. Findings of this study support that of previous researchers which established the impact of substandard processing techniques and hygiene on food quality.

Traditional milk transformation schemes in Côte d'Ivoire and their impact on the prevalence of Streptococcus bovis complex bacteria in dairy products.

The Streptococcus bovis/Streptococcus equinus complex (SBSEC) and possibly Streptococcus infantarius subsp. infantarius (Sii) are associated with human and animal diseases. Sii predominate in spontaneously fermented milk products with unknown public health effects. Sii/SBSEC prevalence data from West Africa in correlation with milk transformation practices are limited. Northern Côte d’Ivoire served as study area due to its importance in milk production and consumption and to link a wider Sudano-Sahelian pastoral zone of cross-border trade. We aimed to describe the cow milk value chain and determine Sii/SBSEC prevalence with a cross-sectional study. Dairy production practices were described as non-compliant with basic hygiene standards. The system is influenced by secular sociocultural practices and environmental conditions affecting product properties. Phenotypic and molecular analyses identified SBSEC in 27/43 (62.8%) fermented and 26/67 (38.8%) unfermented milk samples. Stratified by collection stage, fermented milk at producer and vendor levels featured highest SBSEC prevalence of 71.4% and 63.6%, respectively. Sii with 62.8% and 38.8% as well as Streptococcus gallolyticus subsp. macedonicus with 7.0% and 7.5% were the predominant SBSEC species identified among fermented and unfermented milk samples, respectively. The population structure of Sii/SBSEC isolates seems to reflect evolving novel dairy-adapted, non-adapted and potentially pathogenic lineages. Northern Côte d’Ivoire was confirmed as area with high Sii presence in dairy products. The observed production practices and the high diversity of Sii/SBSEC supports in-depth investigations on Sii ecology niche, product safety and related technology in the dairy value chain potentially affecting large population groups across sub-Saharan Africa.

Direct analysis of ascorbic acid in food beverage samples by flow injection analysis using reduced graphene oxide sensor

In this paper, a simple, sensitive and precise electroanalytical method was developed using flow injection analysis (FIA) with amperometric detection and reduced graphene oxide sensor for ascorbic acid determination in samples of multivitamin beverages, milk, fermented milk, and milk chocolate. The advantages of this sensor include a potential displacement of 450 mV and a 2-fold peak current increase for electrochemical oxidation of ascorbic acid, which resulted in a highly sensitive method. No interference of sample matrix was observed, avoiding solvent extraction procedures (samples were only diluted). The FIA allowed a high analytical frequency, approximately 96 injections per hour, together with adequate detection limit of 4.7 μmol L−1. Good precision (RSD < 7%) and accuracy (recoveries between 91 and 108%) evidenced the robustness of the method. The method was compared with ultra-fast liquid chromatography (UFLC) obtaining statistically similar results (95% confidence level). The ascorbic acid content in samples varied from 0.065 to 2.53 mmol L−1.

Lipase inhibitory activity assay for fermented milk

The lipase inhibitory activity method described here was developed to identify potential anti-obesity properties in milk fermented with different strains of lactic acid bacteria via inhibition of pancreatic lipase and a subsequent decrease in fat digestion and absorption in the gut. The method is based on the hydrolysis of 4-nitrophenyl octanoate by pancreatic lipase and the subsequent release of p-nitrophenol, a coloured product whose absorbance can be measured at 412 nm. Inhibition of lipase leads to a decrease in the amount of p-nitrophenol released and a subsequent reduction in the absorbance with respect to a 100% activity control. The assay was developed by adapting various methods previously described in published literature and includes modifications that are key to adapt the existing protocols to fermented milk samples, in particular the pH issues encountered when analysing acidic samples:•A two buffer system is introduced to allow optimal pH control after addition of fermented milk samples with pH values between 3.5 and 6.5.•A post-clarification filtration step is added for samples where turbidity remains after addition of the clarifying reagent for dairy products.•An absorbance correction factor is calculated and applied to the samples to account for the reduction in the absorbance of p-nitrophenol caused by milk.