PCR detection and identification of histamine-forming bacteria in filleted tuna fish samples

Total of 14 filleted yellowfin tuna fish (Thunnus albacares) sold in wholesale fish market and supermarkets in Milan, Italy, were purchased and tested to determine microbial count, histamine level, histamine-forming bacteria, and their ability to produce histamine in culture broth. Although histamine level was less than 10 ppm, many samples showed high total viable bacterial and enterobacterial counts that reached dangerous levels after temperature abuse for short periods of time. A PCR assay targeting a 709-bp fragment of the histidine decarboxylase gene (hdc) revealed that 30.5% of the 141 enteric bacteria isolated from samples were positive and potentially able to produce histamine. The hdc positive strains were mainly isolated from fish bought at wholesale fish market, where we observed several possible risk factors, such as handling in poor and non-refrigerated conditions during fillet preparation. These positive strains were identified as Citrobacter koseri/Enterobacter spp. and Morganella morganii, by 16S/23S rRNA internal transcribed spacer amplification and 16S rRNA sequence analysis. The strains showed a variable ability of histamine production, with Morganella morganii being the most active histamine-producing species. A direct DNA extraction from fish and a PCR targeting the hdc gene showed a high degree of concordance with the results obtained through microbiological and chemical analyses, and could aid in the prompt detection of potentially contaminated fish products, before histamine accumulates. PRACTICAL APPLICATION: The use of methods for the early and rapid detection of bacteria producing biogenic amines is important for preventing accumulation of these toxic substances in food products. In this study, we used a molecular approach for the detection of histamine-forming bacteria in fish. PCR-based methods require expensive equipment and a high degree of training for the user, but are fast (< 24 h) and reliable. They now represent the best predictive methods to identify a potential risk factor in fish products during processing, storage, and marketing and can be used in the investigation of risk reduction strategies.     

Skin extracts from 2 italian table grapes (italia and palieri) inhibit tissue factor expression by human blood mononuclear cells

Grape and its products such as red wine and grape juice have well-known antithrombotic properties, which have been attributed to their high content in polyphenolic compounds. Most studies on the mechanisms underlying these beneficial effects, among which the suppression of tissue factor (TF) synthesis in blood mononuclear cells (MNC) and vascular endothelium is a prominent one, have been performed with purified polyphenols, while little is known about the effect of fresh grapes which contain a multitude of phytochemicals whose interaction may lead to different cell responses. In this study, we investigated the effect of grape skin extracts (GSEs) on TF expression in isolated blood MNC and in whole blood. Alcoholic extracts from skins of 2 grape varieties (Palieri and Italia) inhibited TF expression in lipopolysaccharide (LPS)-stimulated MNC in a concentration-dependent manner with ≥90% inhibition of TF activity and antigen at 6 μg/mL of gallic acid equivalents. Noteworthy, GSEs were also able to inhibit the appearance of TF in whole blood challenged with LPS. The 2 grape varieties displayed a fairly similar TF-inhibiting capacity despite marked differences in phenolic profile. When selected purified polyphenols were tested, their ability to inhibit TF expression was markedly lower as compared to grape extracts, whereas a mixture of some representative polyphenols was much more efficient, supporting the occurrence of a synergistic effect. Given the key role of cell TF in thrombotic diseases, the inhibition of MNC-mediated clotting activation, if confirmed by in vivo studies, might represent an important antithrombotic mechanism. Practical Application: Our data indicate that the combination of different polyphenols, as in grape extracts, is much more efficient than the single constituents, a finding that might be useful as starting point for the development of new antithrombotic nutraceutics. In addition, our study validated a simple, inexpensive, and physiologically relevant in vitro method on whole blood that allows the evaluation of one of the most important antithrombotic activities of food and food-derived products. The simplicity of the method makes it suitable also for screening purposes in large-scale studies.     

'Fagiolo a Formella', an Italian lima bean ecotype: biochemical and nutritional characterisation of dry and processed seeds

BACKGROUND: An ecotype of the lima bean, named ‘fagiolo a Formella’, which, to the best of our knowledge, is the only example of an Italian lima bean (Phaseolus lunatus L.) ecotype, is cultivated in the Campania region of southern Italy. Physical, nutritional and processing traits of dry seeds were evaluated for two consecutive growing seasons (2009 and 2010). The canning quality was also investigated, but only for the harvest of 2010. RESULTS: Sodium dodecyl sulfate–polyacrylamide gel electrophoresis of total seed proteins allowed the attribution of ‘fagiolo a Formella’ to the Mesoamerican gene pool and Sieva morphotype. Seeds have a trapezoid shape, white coat and 100‐seed weight greater than 42 g. Yield, protein, trypsin inhibitor and phytic acid values were found comparable with those reported for lima bean varieties cultivated in sub‐tropical areas. Moreover, we found that this ecotype is devoid of lectin. CONCLUSIONS: The good adaptation to growing environment is indicated by the fact that ‘fagiolo a Formella’ seed quality is comparable to that of lima beans grown in America. Overall the canning quality was found satisfactory and canning significantly destroys the main anti‐nutritional compounds present in dry seeds. Copyright © 2012 Society of Chemical Industry     

A Bifidobacterium-based synbiotic product to reduce the transmission of C. jejuni along the poultry food chain

With the ban of dietary antimicrobial agents, the use of probiotics, prebiotics and synbiotics has attracted a great deal of attention in order to improve intestinal health and control food-borne pathogens, which is an important concern for the production of safe meat and meat products. Recently, Campylobacter jejuni has emerged as a leading bacterial cause of food-borne gastroenteritis in humans, and epidemiological evidences indicate poultry and poultry products as the main source of human infection. This work aimed at the development of a synbiotic mixture capable of modulating the gut microbiota of broiler chickens to obtain an increase of the beneficial bacteria (i.e. bifidobacteria, lactobacilli) and a competitive reduction of C. jejuni. The prebiotic compound used in the mixture was chosen after an in vivo trial: a fructooligosaccharide and a galactooligosaccharide were separately administered to broilers mixed with normal feed at a concentration of 0.5% and 3%, respectively. Quantitative PCR on DNA extracted from fecal samples revealed a significant (p<0.05) increase of Bifidobacterium spp. in broilers treated with the galactooligosaccharide, coupled to a decrease (p<0.05) of Campylobacter spp. The galactooligosaccharide was then combined with a probiotic Bifidobacterium strain (B. longum subsp. longum PCB133), possessing in vitro antimicrobial activity against C. jejuni. The strain was microencapsulated in a lipid matrix to ensure viability into the feed and resistance to stomach transit. Finally, the synbiotic mixture was administered to broiler chickens for 14 days mixed with normal feed in order to have an intake of 10(9)CFU of PCB133/day. Bifidobacterium spp., Lactobacillus spp., Campylobacter spp., B. longum subsp. longum and C. jejuni were quantified in fecal samples. PCB133 was recovered in feces of all animals. C. jejuni concentration in poultry feces was significantly (p<0.05) reduced in chickens administered with the synbiotic mixture. This study allowed to highlight the positive effect of the synbiotic approach for C. jejuni reduction in broiler chickens, which is of fundamental importance for the safety of poultry meat consumers.     

In situ formation of noble metal nanoparticles on multiwalled carbon nanotubes and its implication in metal–nanotube interactions

A simple method to decorate multiwalled carbon nanotubes (MWCNTs) with Au, Ag and Cu nanoparticles is illustrated. The method consists in directly depositing the selected metals by thermal evaporation on the carbon nanotubes. Comparative measurements carried out on samples that differ in the quantity and type of the deposited metal, reveal that isolated discrete particles form on the nanotube outer wall for all three metals. The CNT-based composites have been investigated by scanning and transmission electron microscopy to determine the size, shape and distribution of the nanoparticles. The results indicate that the quantity of evaporated metal only affects the nanoparticle size and not the average particle density. Particle composition was determined by X-ray photoelectron spectroscopy study. The results are discussed in terms of metal nanoparticle–tube interactions, an important issue for the fundamental and practical applications of similar MWCNT based composites.     

Effects of 1‐methylcyclopropene and post‐controlled atmosphere air storage treatments on fresh‐cut Ambrosia apple slices

BACKGROUND: The effect of 1‐methylcyclopropene (1‐MCP) treatment and two different post‐controlled atmosphere air storage (PCAAS) durations on the quality and chemistry of fresh‐cut Ambrosia apple slices was studied. RESULTS: PCAAS for 1 or 2 weeks prior to slicing had an overall positive effect on the resultant quality of fresh‐cut apple slices. The most significant responses to PCAAS were the suppression of both phenolic and o‐quinone accumulation in slices, and this was related to the significantly lower browning potential values obtained for slices from PCAAS‐treated apples. Polyphenol oxidase (PPO), peroxidase (POX) and ascorbate peroxidase (APOX) activities were not affected by 1‐MCP or PCAAS treatments. PPO and POX activities were almost completely inhibited by a 50 g L^?1 calcium ascorbate anti‐browning dip of apple slices from all treatments. CONCLUSION: The most dramatic effect of the PCAAS treatments was to reduce the accumulation of soluble phenolics, which is likely the reason that o‐quinone accumulation was also inhibited in treated fruits. The consequent reduction in browning potential may be the explanation as to why PCAAS treatment has been shown to reduce fresh apple slice browning in previous work. Copyright © 2012 Society of Chemical Industry     

Key points for maximum effectiveness and safety for cholesterol‐lowering properties of plant sterols and use in the treatment of metabolic syndrome

According to the American Diabetes Association and the Adult Treatment Panel III, the starting point for treating metabolic syndrome (MS) is a change of lifestyle. In addition, action on the main symptoms of MS by means of dietary supplements, can be helpful in view of the chronic course of the disease. The term ‘phytosterols’ refers to sterols and stanols composed of lipophilic triterpenes, a family that is widely distributed in the plant kingdom and whose cholesterol‐lowering properties have been amply demonstrated. In the light of the recent literature, the key points for maximum effectiveness and safety of sterols are the following. (A) Plant sterols should be taken with meals: clinical trials have shown that when plant sterols are consumed close to mealtimes, low‐density lipoprotein cholesterol may decrease by 9.4%, while when they are taken between meals, the reduction is about 6%. (B) The optimal dosage is 2–2.5 g day^?1 in a single dose. More than 3 g day^?1 has not been found to have any additional beneficial effect and increases the risk of side effects. (C) The food matrix used to dissolve the phytosterols should contain a certain amount of fat. A milk‐based matrix appears optimal from this point of view. © 2013 Society of Chemical Industry     

Bioprotection of Ready‐to‐eat Probiotic Artichokes Processed with Lactobacillus paracasei LMGP22043 against Foodborne Pathogens

The survival of 3 pathogens Listeria monocytogenes ATCC19115, Salmonella enterica subsp. enterica ATCC13311, and Escherichia coli ATCC8739 was evaluated over time in ready‐to‐eat (RTE) artichoke products processed or not with the probiotic strain Lactobacillus paracasei LMGP22043. Both probiotic and standard products (final pH about 4.0; a_w = 0.98) dressed with oil and packaged in modified atmosphere were inoculated with pathogens at a level of about 3 log CFU/g and stored at 4 ºC for 45 d. Pathogens decreased in the probiotic product in 2 descent phases, without shoulder and/or tailing as observed by fitting the models available in the GInaFit software to the experimental data. S. enterica subsp. enterica was completely inactivated after 14 and 28 d in probiotic and standard products, respectively; E. coli was inhibited in the probiotic food at day 4 (count <detection limit (DL) 1 log CFU/g), while in the standard product, it survived until the end of experiment. L. monocytogenes decreased in the probiotic product at day 1 reaching values below the DL after 14 d, while 21 d were needed in the standard product, and survived in both samples until the end of the experimental period. Therefore, the probiotic strain, representing always more than the 93% of lactic acid bacteria (about 7 log CFU/g) during the entire experimental period, combines the efficacy of a protective culture, which can control the development of pathogens during storage with probiotic benefits.     

Recycled paper–paperboard for food contact materials: Contaminants suspected and migration into foods and food simulant

Contaminant residues in food packaging is a new challenge of our time, as it may pose a threat for consumers. Higher levels of contaminants were observed in food packaging made by recycled materials, even if little information is available for some groups of contaminants. The present study proposes a procedure for analyzing three different groups of organic contaminants in recycled paper and paperboard. Seventeen commercial samples were analyzed for the presence of bisphenol A (BPA), bis (2-ethylhexyl) phthalate (DEHP), nonylphenol monoethoxylate (NMP) and nonylphenol di-ethoxilate (NDP). Not all the samples contained all the contaminants; BPA was the only substance present in all the samples. The concentrations detected were quite high and, in most of the cases, in agreement with results reported in previous studies. Substance migration tests from spiked/non-spiked samples for two dry foods and Tenax® food simulant were undertaken. BPA migration quotients were always lower than 1%, whereas the migration quotients of DEHP were higher than 2.0%. The highest nonylphenols migration quotients were 6.5% for NMP and 8.2% for NDP. Tenax® simulates well the contaminants migration from paperboard to dry food, in some cases being even more severe than the food.     

Lachancea thermotolerans and Saccharomyces cerevisiae in simultaneous and sequential co-fermentation: A strategy to enhance acidity and improve the overall quality of wine

In the last few years there is an increasing interest on the use of mixed fermentation of Saccharomyces and non-Saccharomyces wine yeasts for inoculation of wine fermentations to enhance the quality and improve complexity of wines. In the present work Lachancea (Kluyveromyces) thermotolerans and Saccharomyces cerevisiae were evaluated in simultaneous and sequential fermentation with the aim to enhance acidity and improve the quality of wine.