Artisanal cheeses relying on spontaneous fermentation as sources of unusual microbiota – The example of the Bulgarian ‘mehovo sirene’ skin bag cheese

The Bulgarian ‘mehovo sirene’ cheese is a type of regional artisanal cheese prepared from raw ewe milk in a skin bag relying on spontaneous fermentation. A metagenomics study revealed an unusual microbiome comprising beneficial bacteria such as Staphylococcus equorum, Lactococcus lactis, Streptococcus thermophilus, Lactobacillus delbrueckii, Lactobacillus kefiranofaciens, Lactococcus raffinolactis, Lactiplantibacillus plantarum, Limosilactobacillus fermentum and Loigolactobacillus coryniformis. Our findings suggest that ‘mehovo sirene’ could have some functional food properties and is a source of beneficial microorganisms.     

Determination and validation of D-values for Listeria monocytogenes and Shiga toxin–producing Escherichia coli in cheese milk

Certain cheeses can be legally produced in the United States using raw milk, but they must be aged for at least 60 d to reduce pathogen risks. However, some varieties, even when aged for 60 d, have been shown to support growth of Listeria monocytogenes or survival of Shiga toxin–producing Escherichia coli (STEC). Thermization, as a subpasteurization heat treatment, has been proposed as a control to reduce the risk of pathogens in raw cheese milk while retaining some quality attributes in the cheese. However, the temperature and time combinations needed to enhance safety have not been well characterized. The objective of this research was to determine and validate decimal reduction values (D-values) for L. monocytogenes and STEC at thermization temperatures 65.6, 62.8, and 60.0°C; a D-value at 57.2°C was also determined for L. monocytogenes only. Nonhomogenized, pasteurized whole-milk samples (1 mL) were inoculated with 8-log cfu/mL L. monocytogenes or STEC (5- or 7-strain mixtures, respectively), vacuum-sealed in moisture-impermeable pouches, and heated via water bath submersion. Duplicate samples were removed at appropriate intervals and immediately cooled in an ice bath. Surviving bacteria were enumerated on modified Oxford or sorbitol MacConkey overlaid with tryptic soy agar to aid in the recovery of heat-injured cells. Duplicate trials were conducted, and survival data were used to calculate thermal inactivation rates. D_65.6°C-, D_62.8°C-, and D_60.0°C-values of 17.1 and 7.2, 33.8 and 16.9, and 146.6 and 60.0 s were found for L. monocytogenes and STEC, respectively, and a D_57.2°C-value of 909.1 s was determined for L. monocytogenes. Triplicate validation trials were conducted for each test temperature using 100 mL of milk inoculated with 3 to 4 log cfu/mL of each pathogen cocktail, A 3-log reduction of each pathogen was achieved faster in larger volumes than what was predicted by D-values (D-values were fail-safe). Data were additionally compared with published results from 21 scientific studies investigating L. monocytogenes and STEC in whole milk heated to thermization temperatures (55.0–71.7°C). These data can be used to give producers of artisanal raw-milk cheese flexibility in designing thermal processes to reduce L. monocytogenes and STEC populations to levels that are not infectious to consumers.     

Novel use of biomass derived alkyl-xylosides in wetting agent for?paper impregnation suitable for the wood-based industry

Today, papers impregnated with thermosetting resins like urea-formaldehyde and/or melamine-formaldehyde are broadly used as covers for wood-based panels like particleboards (PB) and medium density fibreboards (MDF), because they offer flexibility in surface decoration, mechanical endorsement and protection from emissions of Volatile Organic Compounds (VOCs) of the panel. The resin is enhanced with various additives, like hardeners, de-foaming agents, surfactants, wetting agents etc. that are traditionally derived from petroleum. In this study, CHIMAR Hellas tested for the first time biomass-derived surfactants, produced by ARD company, in resin mixtures suitable for paper impregnation. From a chemical point of view, these natural surfactants are alkyl xylosides and particularly amyl and butyl xylosides and proved to have performance equivalent to the petrochemical surfactants conventionally used in this industrial field. Although such surfactants have already been used successfully in other industrial fields, they had never been tested before in paper impregnation processes.     

Method for determination of aflatoxin M₁ in cheese and butter by HPLC using an immunoaffinity column

A rapid, sensitive convenient method for determination of aflatoxin M? (AFM?) in cheese and butter by HPLC was developed and validated. The method employs a safe extraction solution (mixture of acetonitrile, methanol and water) and an immunoaffinity column (IAC) for clean-up. Compared with the widely used method employing chloroform and a Florisil column, the IAC method has a short analytical time and there are no interference peaks. The limits of quantification (LOQ) of the IAC method were 0.12 and 0.14 μg/kg, while those of the Florisil column method were 0.47 and 0.23 μg/kg in cheese and buffer, respectively. The recovery and relative standard deviation (RSD) for cheese (spiked at 0.5 μg/kg) in the IAC method were 92% and 7%, respectively, while for the Florisil column method the corresponding values were 76% and 10%. The recovery and RSD for butter (spiked at 0.5 μg/kg) in the IAC method were 97% and 9%, and those in the Florisil method were 74% and 9%, respectively. In the IAC method, the values of in-house precision (n=2, day=5) of cheese and butter (spiked at 0.5 μg/kg) were 9% and 13%, respectively. The IAC method is superior to the Florisil column method in terms of safety, ease of handling, sensitivity and reliability. A survey of AFM? contamination in imported cheese and butter in Japan was conducted by the IAC method. AFM? was not detected in 60 samples of cheese and 30 samples of butter.     

Reduction of Lactococcus lactis phage contamination in whey by means of membrane filtration: Impact of phage morphology and of bacterial host cells functioning as “phage fishing tool”

For dairy bacteriophages, the impact of phage morphology and whey components on phage retention efficiencies in filtration processes is not known. Therefore, the influence of (i) five differently shaped Lactococcus lactis phages as well as (ii) differently treated bacterial host cells added to native whey were analysed via cross-flow membrane filtration experiments with polyethersulfone membranes. Filtration efficiency with respect to phage retention and whey protein permeation was investigated. Compared with untreated native whey, phage retention was significantly higher (up to 4.8 log units) in the experiments using whey that was spiked with mechanically disrupted lactococcal host cells. However, the retention of phages commonly found in the dairy environment (i.e., members of the 936, c2, and P335 phage groups) did not correlate with the phage morphology. Results of this model study clearly demonstrate that phage titres can be reduced in whey (containing a sufficient protein concentration) by flat sheet membrane filtration processes.     

Calibration of an Evaporative Light-Scattering Detector for the Universal Quantitative Analyses in Liquid Chromatography—Application to the Determination of Triacylglycerols in Cucurbitaceous Oils

The goal of this work is to validate a quantitative method to analyze 15 triacylglycerols (TAG) which are present in cucurbitaceous oils using a new liquid chromatography-evaporative light-scattering detector (LC-ELSD) methodology. For the majority of the TAG, the absence of chromophoric groups absorbing in a spectral zone different from those of the high performance liquid chromatography mobile phases limits the use of UV detectors. The most convenient detectors for this type of analyses are the “universal” aerosol-based detectors, and the most frequently used one among these detectors is the ELSD. TAG responses using ELSD can vary according to their structure and the analyst may not possess all the 15 different TAG standards. Therefore, the determination of these analytes in unknown samples cannot be accurate and depends on the nature of the available standards. We propose here a new quantification methodology by LC-ELSD using the standard response model A = a × m ^b , where a and b are numerical coefficients which are specific for each solute and both correlated. The method uses a sample dilution procedure which provides for each compound to quantify an accurate b value, and by calculation, the corresponding a value. The quantification of both coefficients a and b easily gives the direct mass determination of each TAG. Such LC-ELSD results are validated by the comparison with the fatty acid methyl ester (FAME) analysis using the conventional capillary gas chromatography-flame ionization detector that transforms non-volatile TAG in FAME after a transesterification step. To perform this validation, we compared the experimental FAME composition to the theoretical one calculated from the TAG results obtained by LC-ELSD. For each TAG, theoretical and experimental values were statistically similar, which proves and validates the relevance of the new quantification methodology proposed in this work. The concordance between the two different methods also highlights the great advantage of the direct LC-ELSD method which additionally provides more information on TAG structures.     

Validation of an Electrochemical Detection–High-Performance Liquid Chromatography Method for Simultaneous Determination of Lignans in Flaxseed (Linum usitatissimum L.)

Flaxseed is a major source of lignans, which are important bioactive compounds. The aims of this work were to validate a liquid chromatographic method for the rapid and simultaneous determination of the main lignans in flaxseed using high-performance liquid chromatography coupled with electrochemical detection and to analyze the composition of commercial samples of flaxseed. The performance criteria of the proposed method demonstrate that the method can be used for the analysis of secoisolariciresinol diglucoside (SDG), secoisolariciresinol (SECO), matairesinol (MATA), pinoresinol (PINO), lariciresinol (LARI), hydroxymatairesinol (HYDROXY), and isolariciresinol (ISOLARI) in flaxseeds at suitable levels. Calibration curves were determined for six different concentrations of standard solutions injected in triplicate. The sensitivity of the calibration curve was evaluated considering the confidence intervals of the intercept and slope. The limit of detection and limit of quantification were 7.4 and 10.9 μg/l, respectively, for LARI and 17.7 and 37.5 μg/l, respectively, for MATA. The relative standard deviation of repeatability values were lower than 2.59 %, which are acceptable because the Horwitz ratio values were 0.1 for all of the lignans. The recoveries of lignans were in the range of 74–100 % of SECO, which are consistent with the literature. The precision of the proposed method was determined by analyzing four flaxseed samples of different years and varieties. SDG was the main lignan present in all the samples, followed by ISOLARI and HYDROXY.     

Determination of mineral oil paraffins in foods by on-line HPLC–GC–FID: lowered detection limit; contamination of sunflower seeds and oils

A method is described to lower the detection limit for mineral oil saturated hydrocarbons (MOSH) in foods as compared to the on-line HPLC–LC–GC–FID method described previously: samples are preseparated (enriched) by conventional liquid chromatography on activated silica gel and activated aluminum oxide. The silica gel retains up to 1 g of fat or oil, the aluminum oxide up to 2 mg n-alkanes of at least 24 carbon atoms, i.e. plant paraffins which may severely hinder the analysis of the mineral paraffins. The efficacy of the method is shown for an apple and sunflower oil. Oils extracted from manually harvested seeds grown in fields or gardens contained between 0.14 and 0.77 mg/kg MOSH. In the oils from seeds sampled in an oil mill, this value was increased to 3.3–9.3 mg/kg, indicating a contamination during harvest, transport and/or storage. Concentrations in commercial refined sunflower oils ranged between 2.7 and 32 mg/kg, averaging 11.2 mg/kg. Since deodorization removes a substantial part of the MOSH, this suggests a further contamination in the oil mill. The contamination affected all samples at a similar level, indicating that it occurs systematically by the presently used technology.     

Assessment of the potential of Arabic gum as an antimicrobial and antioxidant agent in developing vegan “egg-free” mayonnaise

The main factors affecting the spoilage of mayonnaise are lipid oxidation and microbial contamination. Therefore, the investigation was carried out to estimate the antimicrobial and antioxidant properties of the aqueous extract of the Arabic gum (AG). The effect of the addition of AG powder on physical–chemical and sensory properties has been evaluated in different percentages of 25, 50, 75, and 100 into mayonnaise. At the highest concentration of AG 20 mg/ml, the DPPH result represented high antioxidant activity at 92.13%. AG had inhibitory effects on gram-negative and gram-positive bacteria, with Staphylococcus aureus and Bacillus subtilis being the most susceptible bacteria. The use of AG as an egg substitute in mayonnaise has been shown to have a great effect on physical–chemical properties. All mayonnaise samples were sensory acceptable, particularly vegan mayonnaise (100% AG) and still acceptable for consumption at 5°C for 5 months of storage. AG could be considered an additive with significant emulsifier properties, antioxidant, and antimicrobial activities. Therefore, AG is a good choice to produce new vegetarian products for consumers who are unable to eat egg-based foods.     

Coating of Sol–Gel Film on Silver Nanodendrite as a Novel Solid-Phase Microextraction Fiber for Determination of Volatile Aldehydes in Edible Oils

In this work, a novel solid-phase microextraction fiber was fabricated by a new substrate applied for quantitative analysis of trace volatile aldehydes emitted during thermal oxidation of edible oils, analyzed by GC–MS. Ag nanodendrites as a porous substrate, spontaneously coated on a Cu wire, and polydimethylsiloxane/polyethylene glycol (PDMS/PEG) were deposited onto the substrate by sol–gel dip-coating. Parameters affecting the extraction efficiency, such as the substrate porosity, extraction time and temperature, and desorption time and temperature were investigated and optimized. The desorption temperature was chosen as 260 °C, and desorption time was set at 3 min. Results shows that extraction efficiency of sol–gel coating deposited on Ag nanodendrite substrate is meaningfully higher than that of deposited on bare Cu wire. Under the optimum conditions, the limits of detection (LODs) ranged between 0.5 to 0.2 μg/L. The relative standard deviations including repeatability (within fibers) and reproducibility (between fibers) varied between 7.5–11.2 and 9.3–16.2%, respectively.     

Short communication: Is consumption of a cheese rich in angiotensin-converting enzyme-inhibiting peptides,such as the Norwegian cheese Gamalost,associated with reduced blood pressure?

Epidemiological and clinical studies have shown that angiotensin-converting enzyme (ACE)-inhibiting peptides derived from dairy products may decrease blood pressure. These peptides have been identified in many cheeses, and Gamalost, a traditional Norwegian cheese, is particularly rich in these peptides. The aim of this cross-sectional study was to examine whether frequency of Gamalost intake was associated with blood pressure in a Norwegian population sample. Blood pressure and other clinical measurements, including the factors of metabolic syndrome, were obtained from 168 participants (56% female, mean age = 51 yr) who completed a questionnaire about dietary habits and other health-related factors. Mean Gamalost intake was 2 servings per week. The prevalence of hypertension was 23.8% in the population, with mean systolic and diastolic blood pressures of 128 and 78 mmHg, respectively. Intake of Gamalost was inversely associated with systolic blood pressure. Each increase in frequency unit of Gamalost intake corresponded to a reduction in systolic blood pressure of 0.72 mmHg, after controlling for sex, age, education, waist circumference, physical activity, smoking status, and dairy food intake. Results from this study indicate that consumption of Gamalost (or other foods rich in ACE-inhibiting peptides) may reduce blood pressure.     

Microassay for the quantitation of protein precipitable polyphenols: use of bovine serum albumin–benzidine conjugate as a protein probe

A simple, sensitive and indirect spectrophotometric method for the determination of protein precipitable polyphenols (tannins) has been developed, based on the ability of the polyphenols to precipitate the synthetic, brown coloured azo-protein, bovine serum albumin–benzidine conjugate (BSA–benzidine, mole ratio 1:7), which shows an absorption maxima at 405 nm. The amount of unprecipitated BSA–benzidine is measured directly at 405 nm, which is inversely related to the polyphenol concentration. Tannic acid was used as a reference standard. The microassay was performed in citrate/phosphate buffer (0.1 m), pH 4.8. The method was found to be linear in the range of 5–150 μg (3–88 nmol) of tannic acid (y=1.0+(−0.007)x; r=−0.989). Spiking studies carried out with various levels of tannic acid (0.01, 0.1 and 1.0%) indicated a recovery in the range of 94–101% and 94–98% in rice and sorghum samples, respectively. Free phenolics, when added in the range of 50–150 μg (catechin, chlorogenic acid, ferulic acid, caffeic acid and p-coumaric acid) had no influence on the protein precipitation in the microassay. Also spectral analysis of free phenolics and acid-methanolic sorghum extracts showed no interference in the present method. The conjugate was found to be stable over a period of 24 weeks in a freeze-dried condition and at 4°C, with <5% deterioration in aqueous condition. The microassay method developed has been used for the quantitation of protein precipitable polyphenols in various sorghum (Sorghum bicolor L. Moench) genotypes and compared with the widely used Folin–Denis chemical method of analysis.     

Use of ultrasounds in the food industry–Methods and effects on quality,safety, and organoleptic characteristics of foods: A review

The use of ultrasounds has recently gained significant interest in the food industry mainly due to the new trends of consumers toward functional foods. Offering several advantages, this form of energy can be applied for the improvement of qualitative characteristics of high-quality foods as well as for assuring safety of a vast variety of foodstuffs, and at the same time minimizing any negative effects of the sensory characteristics of foods. Furthermore, the non-destructive nature of this technology offers several opportunities for the compositional analysis of foods. However, further research is required for the improvement of related techniques and the reduction of application costs in order to render this technology efficient for industrial use. This review paper covers the main applications of ultrasounds as well as several advantages of the use of the technology in combination with conventional techniques. The effects of ultrasounds on the characteristics, microbial safety, and quality of several foods are also detailed     

Development and characterization of dehydrated peanut–cowpea milk powder for use as a dairy milk substitute in chocolate manufacture

This study explored the feasibility of producing peanut–cowpea milk for use in vegetable milk chocolates. Development of the vegetable milk followed a 3 × 2 factorial design, with peanut–cowpea ratio (1:1, 1:2 and 1:3), and treatment with enzyme (i.e. enzyme hydrolyzed and non-hydrolyzed milk) as the factors. The milk was dehydrated and then milled using a hammer mill (mesh size 40). It was then used in recipes to produce chocolates and evaluated sensorially based on ranking for preference. Skimmed milk powder was used to produce the control chocolate. The ratio of cowpea to peanut affected the chemical and functional characteristics of the vegetable milk. Vegetable milk made from 1:2 ratios of peanuts:cowpea produced the most preferred chocolates. The successful application of this by industry will improve the utilization of the legume crops and enhance their market value.