Evaluation of Sample Preparation Procedures for Trace Element Determination in Brazilian Propolis by Inductively Coupled Plasma Optical Emission Spectrometry and Their Discrimination According to Geographic Region

Propolis is a complex mixture of substances collected by honeybees from buds or exudates of plants, beeswax, and other constituents, as pollen and sugars. The main purpose of this study was to evaluate two digestion procedures for determination of major, minor, and trace elements (Ba, Ca, Cd, Cr, Co, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, and Zn) in natura propolis samples by inductively coupled plasma optical emission spectrometry (ICP OES). The first procedure studied was an open-vessel digestion using HNO₃ + H₂SO₄ + H₂O₂ in a heating block and the second one was a microwave-assisted concentrated acid digestion using HNO₃ + H₂O₂. Both digestion procedures led to similar results and quantitative recoveries. The residual carbon contents (RCCs) for propolis sample digests were 0.269?±?0.012 % when using the first procedure with conventional heating and 0.458?±?0.023 % by microwave-assisted closed vessel digestion, demonstrating high efficiency of both procedures. Accuracy of the results was demonstrated using a certified reference material and by comparison with a recommended official method. The t test (unpaired) at 95 % confidence level showed that there was no significant difference between determined and certified values of all analytes under investigation, except Ca concentration employing conventional procedure. The optimized microwave-assisted digestion procedure led to recoveries around 89–103 % and precision better than 5 % for most samples. The second procedure was faster, safer, and more accurate than the one based on conductive heating. Additionally, principal component analysis (PCA) was applied for checking if there was correlation between inorganic composition and source of propolis samples collected around Bahia State in the Northeast of Brazil.     

Influence of phytosterol and phytostanol food supplementation on plasma liposoluble vitamins and provitamin A carotenoid levels in humans: An updated review of the evidence

Phytosterols and phytostanols (PAP) compete with cholesterol absorption in the intestine, resulting in a 5–15%-reduction in plasma total and LDL cholesterol. An important issue is the PAP potential to reduce the plasma concentrations of fat-soluble vitamins and provitamin A carotenoids. Here, an update of the scientific evidence is reviewed to evaluate plant PAP-enriched foods impact on plasma fat-soluble vitamins and carotenoid levels, and to discuss potential implications in terms of cardiovascular risk. Based on 49 human interventional and 3 bioavailability studies, results showed that regular consumption, particularly over the long term, of foods fortified with PAP as recommended in labeling does not significantly impact plasma vitamins A, D, and K concentration. A 10% significant median reduction was observed for α-tocopherol. Concerning carotenoids, while 13 studies did not demonstrate statistically significant plasma β-carotene reduction, 20 studies showed significant reductions, with median effect size of ?24%. This decline can be mitigated or offset by increased fruits and vegetables consumption. Furthermore, higher cardiovascular risk was observed for differences in plasma β-carotene concentration of the same magnitude as the estimated average decrease by PAP consumption. These results are supported by the only study of β-carotene bioavailability showing decrease in absorption by phytosterols daily intake.     

Characterization of bacteriocins from two Lactococcus lactis subsp. lactis isolates

In this study, bacteriocins from two Lactococcus lactis subsp. lactis isolates from raw milk samples in Turkey designated OC1 and OC2, respectively, were characterized and identified. The activity spectra of the bacteriocins were determined by using different indicator bacteria including Listeria, Bacillus and Staphylococcus spp. Bacteriocins were tested for their sensitivity to different enzymes, heat treatments and pH values. Loss of bacteriocin activities after alpha-amylase treatment suggested that they form aggregates with carbohydrates. Molecular masses of the purified bacteriocins were determined by SDS-PAGE. PCR amplification was carried out with specific primers for the detection of their structural genes. As a result of these studies, the two bacteriocins were characterized as nisin and lacticin 481, respectively. Examination of plasmid contents of the isolates and the results of plasmid curing and conjugation experiments showed that in L. lactis subsp. lactis OC1 strain the 39.7-kb plasmid is responsible for nisin production, lactose fermentation and proteolytic activity, whereas the 16.0-kb plasmid is responsible for lacticin 481 production and lactose fermentation in L. lactis subsp. lactis OC2 strain.     

Tenderisation of the dog cockle (Glycymeris glycymeris) meat by polyphosphates

Clams are widely used in the preparation of several seafood dishes but there are still a few bivalve species which have not been extensively used. Among these species is dog cockle (Glycymeris glycymeris), which is a major by-catch of surf clam (Spisula solida) fishing. However, dog cockle has a low commercial value because its texture is too tough after cooking. This study was initiated to find the best way of tenderising the meat of this species to make it suitable for human consumption. Based on preliminary trials using different tenderising products, a mixture of sodium tripolyphosphate and sodium chloride (3% and 1.5% respectively) was considered the most effective. The optimization of the processing parameters (time and temperature) was done by response surface methodology. According to the sensory analysis, objective texture evaluation and phosphate determinations the optimum conditions for the tenderisation process were an immersion time of 3 h at a temperature of 20  °C. The tenderised meat was used in the preparation of two types of canned products (light brine and a pickling sauce known as "escabeche"), which were evaluated by a taste panel and judged satisfactory.     

Non-culture-based identification of mastitis-causing bacteria by MALDI-TOF mass spectrometry

The purpose of this study was to evaluate the detection limit of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for direct identification, without previous microbiological culture, of bovine mastitis-causing bacteria from milk samples. Milk samples (n = 15) were experimentally contaminated with Staphylococcus aureus, Streptococcus uberis, Streptococcus agalactiae, Streptococcus dysgalactiae, and Escherichia coli to have bacterial counts ranging from 10³ to 10⁹ cfu/mL. These contaminated milk samples were subjected to a preparation protocol for bacterial ribosomal protein extraction using the MALDI Sepsityper kit (Bruker Daltonik, Bremen, Germany), which allowed MALDI-TOF MS coupled with Biotyper software (Bruker Daltonik) to identify bacterial fingerprints based on intact ribosomal proteins. The ability of MALDI-TOF MS to correctly identify bacterial strains from experimentally contaminated milk (without previous microbiological culture) depended on the bacterial count of the samples and on the species of the bacteria evaluated. Adequate identification at the bacterial species level (score ≥2.0) directly from milk samples required bacterial counts in the following ranges: ≥10⁶ cfu/mL of Staph. aureus, ≥10⁷ cfu/mL of E. coli, and ≥10⁸ cfu/mL of Strep. agalactiae, Strep. dysgalactiae, and Strep. uberis. We concluded that direct identification of mastitis-causing pathogens is possible for Staph. aureus, E. coli, Strep. agalactiae, Strep. dysgalactiae, and Strep. uberis, but correct identification depended on the bacterial count in the milk samples.     

Effect of inoculation of Carnobacterium divergens V41, a bio-preservative strain against Listeria monocytogenes risk, on the microbiological, chemical and sensory quality of cold-smoked salmon

The aim of this study was to develop a bio-preservation strategy for cold-smoked salmon (CSS) by the use of lactic acid bacteria previously selected for their capability to inhibit the growth of Listeria monocytogenes in the product. The spoiling potential of three Carnobacterium strains (Carnobacterium divergens V41, Carnobacterium piscicola V1 and SF668) was tested in sterile CSS blocks inoculated by 10(4-5) CFU g(-)(1) and stored under vacuum for 9 days at 4 degrees C followed by 19 days at 8 degrees C. C. divergens V41 grew a little faster than the other strains and none of the three carnobacteria showed any adverse effect on quality of the product, i.e. no off-odour detected by a trained panel, no total volatile basic nitrogen (TVBN) production, no acidification and no biogenic amine except a slight production of tyramine. An application on commercial CSS was tested by spraying C. divergens V41 (10(4-5) CFU g(-1)) on slices of four batches freshly processed in different smoke-houses. Microbial, chemical and sensory characteristics were weekly compared to a control during 4 weeks of vacuum storage. When the natural microflora was initially weak (two batches<20 CFU g(-1)), C. divergens V41 quickly reached 10(7-8) CFU g(-1) and a slight inhibition of endogenous Enterobacteriaceae, lactobacilli and yeasts was observed. The presence of C. divergens V41 was slightly detected (odour and flavour) but none of the sample was considered as spoiled by the sensory panel. When the natural microflora was initially high (2 batches>10(4-5) CFU g(-1)), no effect on the microflora, TVBN and biogenic amine production, nor on the sensory characteristics was observed in presence of C. divergens V41. In conclusion, bio-preservation of CSS using lactic acid bacteria such as C. divergens V41 is a promising way to inhibit the growth of pathogenic bacteria such as L. monocytogenes with low effect on the quality of the product.     

Rapid virus detection procedure for molecular tracing of shellfish associated with disease outbreaks

Detection of pathogenic viruses in oysters implicated in gastroenteritis outbreaks is often hampered by time-consuming, specialist virus extraction methods. Five virus RNA extraction methods were evaluated with respect to performance characteristics and sensitivity on artificially contaminated oyster digestive glands. The two most promising procedures were further evaluated on bioaccumulated and naturally contaminated oysters. The most efficient method was used to trace the source in an outbreak situation. Out of five RNA extraction protocols, PEG precipitation and the RNeasy Kit performed best with norovirus genogroup III-spiked digestive glands. Analyzing 24-h bioaccumulated oysters revealed a slightly better sensitivity with PEG precipitation, but the RNeasy Kit was less prone to concentrate inhibitors. The latter procedure demonstrated the presence of human noroviruses in naturally contaminated oysters and oysters implicated in an outbreak. In this outbreak, in four out of nine individually analyzed digestive glands, norovirus was detected. In one of the oysters and in one of the fecal samples of the clinical cases, identical norovirus strains were detected. A standard and rapid virus extraction method using the RNeasy Kit appeared to be most useful in tracing shellfish as the source in gastroenteritis outbreaks, and to be able to make effective and timely risk management decisions.     

Authenticity Control of Roasted Coffee Brands Using Near-Infrared Spectroscopy

In this work, a methodology based on near-infrared spectroscopy (NIRS) was exploited in order to discriminate between commercial coffee brands. The main advantages of this approach compared to other strategies (e.g., wet chemistry methods) are its lower cost, less labor, and lower time per analysis. Two commercial brands were discriminated among several others present in the Portuguese market. The chemometric method used to estimate discriminant models was partial least squares discriminant analysis (PLSDA). Results show that it is possible to discriminate coffee brands using this strategy with a correct classification of 100 %. The spectral region, more favorable to discrimination of roasted coffee brands, can be related with differences in the concentrations of compounds, such as, chlorogenic acid and sucrose, and also due to differences on lipid fraction. This methodology is adequate for field implementation, namely, adopting handheld NIRS instruments.