Stability and Quality Parameters of Probiotic Cantaloupe Melon Juice Produced with Sonicated Juice

The use of sonicated melon juice as substrate for Lactobacillus casei growth in cantaloupe melon juice and its effect on product quality were investigated. The survival of L. casei in the fermented juice, the product color, the post-acidification and other quality parameters were evaluated in the refrigerated product (4 °C) for a period of 42 days. Storage pH, color, sugar content, lactic acid concentration, biomass and viable cells count were determined. The caloric value of the product was also evaluated. During the refrigerated storage period, acidification and a slight reduction in the number of viable cells were observed. However, a sufficient number of viable cells were observed to guarantee the beneficial properties from probiotic consumption (>8 log CFU?ml^?1) throughout the storage period, for both stocked samples (with and without sugar addition). The product color was also preserved during storage. The developed product resulted in a low caloric product. The caloric value was reduced during the storage period due to sugar consumption by the remaining microorganisms.     

Physicochemical Characterization of Lemongrass Essential Oil–Alginate Nanoemulsions: Effect of Ultrasound Processing Parameters

The formation of lemongrass oil (1 %?v/v) nanoemulsions in aqueous sodium alginate solution (1 %?w/v) containing Tween 80 (1 %?v/v) as nonionic surfactant was studied in terms of droplet size, electrical charge, viscosity, and whiteness index considering different ultrasonication times (0, 30, 60, 120, and 180 s) and amplitudes (30, 60, and 100 μm). The droplet size and size distribution of the emulsions decreased at increasing treatment time and amplitude. The minimum average droplet size observed in nanoemulsions was 4.31?±?0.18 nm with a narrow size distribution. The interface electrical charge of the coarse emulsion was ?18.0?±?2.9 mV, whereas in ultrasonicated nanoemulsions, it diminished up to ?55.8?±?6.4 mV when the sonication time was extended for 180 s. The viscosity of nanoemulsions also decreased at increasing treatment time and amplitude. Moreover, nanoemulsions became translucent after sonicating for 180 s at 30, 60, or 100 μm with whiteness indices of 28.61?±?0.17, 27.93?±?0.21, and 27.86?±?0.33, respectively. Therefore, it can be stated that ultrasound processing might be a feasible technology to produce highly translucent lemongrass oil–alginate nanoemulsions, with extremely small droplet sizes and high stability to be used as delivery systems of essential oils in food products. However, it is necessary to investigate the effect of ultrasound processing parameters on the antimicrobial potential of essential oils incorporated to nanoemulsions.     

Comparison of Simple and Rapid Extraction Procedures for the Determination of Pesticide Residues in Fruit Juices by Fast Gas Chromatography–Mass Spectrometry

Three sample treatment methods, based on QuEChERS, solid-phase extraction (SPE) and solid-phase microextraction (SPME), were compared and evaluated in order to obtain the best conditions to determine pesticide residues in fruit juice by fast gas chromatography–mass spectrometry (single quadrupole GC-MS). Analysis were performed under selected ion monitoring, acquiring the three most abundant and/or specific ions for each analyte and using their relative intensity ratios as a confirmatory parameter. The 3 methodologies (QuEChERS, SPE and SPME) were validated taking 15 selected pesticides as model compounds, using commercial apple juice. QuEChERS procedure was based on the AOAC Official Method 2007.01, using acetonitrile (containing 1 % acetic acid) as extraction solvent and primary–secondary amine during the dispersive solid-phase extraction. Oasis hydrophilic–lipophilic balance cartridges were used for SPE, and polyacrylate fibers were used for direct immersion SPME procedure. Three isotopically labeled standards were added to the samples before extraction and used as surrogate standards. Validation parameters as recoveries, limits of detection, and limits of quantification (LOQ), as well as matrix effects and sample throughput, were obtained and compared for the three extraction procedures. QuEChERS was considered faster and led to the best quantitative results. In this way, validation was extended to up to 56 pesticides by applying QuEChERS in multi-fruit juice samples, obtaining LOQs ranging from 2 to 20 μg/L for most compounds. Accuracy and precision were evaluated by means of recovery experiments at two concentration levels (10 and 100 μg/L), obtaining recoveries between 70 and 120 % in most cases and relative standard deviations below 15 %. Finally, the QuEChERS method was applied to the analysis of commercial juices, including mango–apple, pineapple, grapefruit and orange.     

The evaluation of a PCR-based method for identification of Salmonella enterica serotypes from environmental samples and various food matrices

The most commonly used method for serotyping Salmonella spp. is based on the Kaufmann–White scheme, and is composed of serological reactions using antibodies to LPS agglutinins. The multiplex PCR used in this investigation was established by Kim et al. to serotype the 30 most common clinical Salmonella serotypes, as determined by CDC. The PCR assay consists of two five-plex reactions and a single two-plex PCR reaction, based on six genetic loci from Salmonella enterica serotype Typhimurium and four loci from S. enterica serotype Typhi. In this investigation, we further evaluated the method for serotyping Salmonella spp. using a reference collection, environmental samples collected from a Mid-Atlantic region tomato farm study, four food matrices spiked with different Salmonella serotypes and a proficiency test. The PCR assay was first evaluated using DNA isolated from pure cultures of isolates obtained from various clinical and environmental samples, and then DNA isolated from broth cultures of food matrices of “Red round” and Roma tomatoes, Romaine lettuce, green onions and Serrano peppers spiked with serotypes Newport, Typhimurium, Javiana and Saintpaul, respectively. The results showed that the PCR assay correctly serotyped Salmonella spp. from the clinical, environmental, spiked food matrices, and proficiency test samples. These findings are significant because the PCR assay was successful in the identification of Salmonella in the spiked samples in a broth culture containing other non-salmonella organism. This method may be a useful resource for the food safety community.     

Wild Lactobacillus strains: Technological characterisation and design of Coalho cheese lactic culture

To design a specific lactic culture for the controlled manufacture of coalho cheese, 13 Lactobacillus rhamnosus, two Lactobacillus fermentum and one Lactobacillus plantarum strains isolated from artisanal coalho cheeses were identified and characterised. Two Lb. rhamnosus, one Lb. plantarum and one Lb. fermentum were selected and grouped in pairs designing four different culture formulations that demonstrated a good performance in cheesemaking experiments at pilot scale. Further studies to adjust the balance of strains used are necessary to attain adequate sensorial and technological attributes as expected for artisanal cheeses.     

Proposal of visual strength grading rules for Uruguayan pine timber

A previous database with bending and density data of 261 structural size specimens of currently produced Uruguayan slash pine and loblolly pine timber was adjusted to meet testing and characterization requirements of European standards. Visual parameters and mechanical properties for each specimen were evaluated and their relationship was statistically analyzed. Results suggested that all specimens can be grouped in one visual grade with engineered properties similar to those of European C14 strength class. Modulus of elasticity and characteristic bending strength were the defining properties for class assignation.     

Pasting,thermal, gel texture,resistant starch and colour properties of unripe banana flour from 10 desert banana varieties cultivated in South Africa

Unripe banana flour is a potential commercial ingredient in various food products for increased resistant starch and reduced gluten contents. In the present study, the pasting (rapid visco-analysis), gel texture (penetration test), thermal (differential scanning calorimetry), colour (tri-stimulus colour indices) and the resistant starch properties of unripe banana flour produced from different dessert banana varieties (n?=?10) cultivated in South Africa, were analysed and juxtaposed to wheat and maize flour. The functional properties varied significantly (p?≤?0.05) between banana varieties, and from wheat and maize flours, to various extents. Selected functional property ranges of unripe banana, wheat and maize flours, respectively included; flour colour index (63.16–76.42, 77.34 and 80.96), paste viscosity (405.5–556.6, 124.7 and 115.6 RVU), gelatinization temperature (64.67–71.21, 71.11 and 69.95?°C), gel firmness (7.24–11.44?×?10^??2 N, 3.49?×?10^??2 N and 6.56?×?10^??2 N) and resistant starch content (19.9–47.4, 2.8 and 2.2% w/w). Multivariate analysis (principle component analysis) showed that the unripe banana flours from different varieties were distinguished from each other based on the pasting temperature. The unripe banana flours were distinguished from both wheat and maize flour based on breakdown and peak paste viscosities. The breakdown viscosity was the most positively related measure to the resistant starch content with a linear regression R-squared value of 0.898, indicating a significant role played by granule structure in resistance to enzymatic hydrolysis. The present research demonstrates that selection of appropriate dessert banana variety is important when replacing staple flours (wheat and maize) with unripe dessert banana flour as a functional ingredient.     

Detection of methicillin-resistant coagulase-negative staphylococci and PVL/mecA genes in cefoxitin-susceptible Staphylococcus aureus (t044/ST80) from unpasteurized milk sold in stores in Djelfa,Algeria

This study was designed to determine antimicrobial resistance phenotypes and genotypes and virulence factors in Staphylococcus aureus and coagulase-negative staphylococci (CNS) in unpasteurized milk sold in Djelfa, Algeria. Eighty-two unpasteurized cow milk samples were randomly obtained from 82 retail stores in Djelfa and tested to detect staphylococci. Species were identified by biochemical tests and MALDI-TOF. Antimicrobial resistance phenotypes and genotypes were determined by disk diffusion test, PCR, and sequencing. The Staph. aureus isolates were subjected to spa typing, multilocus sequence typing, and detection of virulence genes and the scn gene by PCR and sequencing. Forty-five (54.9%) milk samples were contaminated by staphylococci and 45 isolates were recovered: 10 Staph. aureus (12.2% of total samples) and 35 CNS (42.7%). Resistance to penicillin (blaZ), tetracycline (tetL/tetK), and erythromycin (ermB/msrA/ermC) were the most common phenotypes (genotypes). Three CNS were methicillin-resistant and all were mecA-positive. The Staph. aureus isolates were ascribed to the following lineages [spa type/sequence type/associated clonal complex (number of isolates)]: t267/ST479/CC479 (n = 6), t1510/ST5651/CC45 (n = 1), t359/ST97/CC97/ (n = 1), t346/ST15/CC15 (n = 1), and t044/ST80 (n = 1). The mecA gene was detected in the cefoxitin-susceptible t044/ST80 isolate and co-harbored the lukF/lukS-PV and scn genes. The detection of mecA-PVL-positive Staph. aureus, methicillin-resistant CNS, and multidrug-resistant staphylococcal species indicates a potentially serious health issue and reveals that unpasteurized milk sold in Djelfa city could be a potential vehicle for pathogenic and antimicrobial-resistant staphylococci.