Survival of Lactic Acid Bacteria and Their Lactases under Acidic Conditions

Effects of sonication, survival, and β-galactosidase activity of four lactic cultures were investigated in pH 1.5-3.5 range. Lactobacillus delbruekii subsp. bulgaricus and Streptococcus thermophilus exhibited the highest β-galactosidase activity in skim milk and broth systems, respectively. The β-galactosidases from L. delbruekii subsp. bulgaricus, S. thermophilus, and L. acidophilus showed optimum activity in the neutral pH range and 55°C. Viable count of all four cultures decreased most rapidly at pH 1.5, but L. acidophilus and L. delbruekii subsp. bulgaricus survived better than the other organisms. The decrease of enzyme activity of unsonicated cultures with pH was slight, especially at pH 3.5. However, acidification of sonicated cultures to pH 3.5 or lower resulted in rapid and permanent loss of enzyme activity.     

Reduction of Numbers of Salmonella typhimurium on Poultry Parts by Repeated Freeze-Thaw Treatments

Cells of Salmonella typhimurium suspended in 50 ml of 0.1% buffered peptone were subjected to five cycles of rapid or slow freezing and rapid or slow thawing. A five cycle rapid freeze-rapid thaw process was found to be an effective treatment resulting in 99% reduction in the numbers of S. typhimurium cells. Of the surviving cells after treatment, 75% was sublethally injured. The five cycle rapid freeze-rapid thaw process was investigated for its effectiveness in reducing numbers of S. typhimurium cells on experimentally inoculated chicken wings. The part of chicken wings consisting of ulna and radius with attached skin and muscle was inoculated with low (16–20 CFU/g) or high (ca 1,100 CFU/g) numbers of S. typhimurium and each wing was subjected to five cycles of the rapid freeze-rapid thaw process. There was over 90% reduction in the numbers of S. typhimurium cells on the chicken wings after the freeze-thaw treatment.     

Investigation of some factors affecting the antibacterial activity of rosemary extracts in food models by a food microdilution method

The activity of rosemary phenolic extracts against Listeria monocytogenes and Escherichia coli was evaluated in 50% food models of meat, vegetable and dairy products in relation to some factors that can affect MIC (minimal inhibitory concentration) values (inoculum level, proportion of food, temperature) using a new food microdilution method. It was shown that the interactions of meat and milk components with plant extracts reduced the antibacterial effectiveness of rosemary extracts. MIC values for L. monocytogenes were lower than for E. coli in all tested conditions. A lower inoculation level caused a decrease in MIC values for E. coli but an increase in MIC values for L. monocytogenes in control media. In food models, MIC values were higher or equal to MIC values in control media regardless of bacterial type. We showed that the food microdilution method represents a simple, rapid, reproducible and inexpensive method for testing the antimicrobial efficiency of plant extracts in food systems.     

A microwire sensor for rapid detection of Escherichia coli K-12 in fresh produce

A rapid immunofluorescence method for foodborne pathogens in food systems using microwire sensor coupled with high frequency alternating current was developed. The method was intended to enrich and quantify E. coli cells internalized in baby spinach leaves. The targeted bacterial cells in the sample solution were captured on microwires in a diameter of 25 μm, and were bound to fluorescein isothiocyanate (FITC) labeled polyclonal E. coli antibodies. Fluorescent images of the FITC antibodies were obtained using a fluorescence microscope equipped with a charge-coupled-device (CCD) camera, and the fluorescent intensity (FI) was quantified through image processing. The capture of E. coli K-12 in PBS buffer was optimized when the electric field was generated at the frequency of 3 MHz and 20 Vpp with bacterial concentration of 10⁷ CFU/mL. The detection limit of our sensing device was determined to be 10³ CFU/mL. Field emission scanning electron microscopy (FESEM) was used to validate and visualize E. coli cells captured on the tip surface. The sensitivity and specificity of the developed sensor has been successfully validated by testing E. coli internalized in baby spinach leaves. The immunofluorescence detection has been completed within 15 min. Moreover, it was found that the enrichment process of E. coli cells using the dielectrophoretic force was rarely affected by food particles, which proved the sensing selectivity. The developed sensor is expected to meet the steady demand for a simple, rapid, highly sensitive detection approach to quantify the targeted microbes in food systems.

Industrial Relevance

There has been an increase in the number of foodborne illnesses linked to the consumption of fresh and minimally processed fruits and vegetables. Some E.coli strains such as E.coli O 157:H7, can cause a variety of diseases, including diarrhea, urinary tract infections, respiratory diseases, meningitis and more. In general, consumers wash the fresh produces under cold running tap water to remove any lingering dirt on the surface of the produces before eating or preparing. However, how do the consumers know if there is any possible pathogen hiding inside of the fresh produce after rinsing? It was reported from many researchers that, the E.coli internalization, which may occur when fresh produces intake E. coli containing water or manure from the soil, would be a main cause of the foodborne illness outbreak. To ensure the safety of drinking water, E.coli concentration cannot be higher than 1 CFU/mL. How can we detect such a low level of E.coli in an easy yet efficient way? To our knowledge, none of the traditional detecting approaches such as cultural based method, polymerase chain reaction(PCR), surface plasmon resonance (SPR) biosensor, and Latex Agglutination, has performed perfectly. Hence, a rapid and accurate technique for detecting foodborne pathogens in fresh produce is urgently needed in order to secure the food safety.To overcome this issue, a simple detection method for foodborne pathogens in food systems using the microwire sensor coupled with high frequency alternative current was developed. The sensitivity and specificity of the developed sensor have been successfully validated by testing with E. coli internalized inside baby spinach leaves. It was found that spinach particles rarely affect the performance of our sensing device, which shows a promising prospect of its application in food industries.     

Thin-Layer Chromatography of Carotenoids with Tertiary Alcohol-Petroleum Ether Solutions as Developing Solvents

Carotenoid thin-layer chromatography on silica layers using petroleum ether containing tert-butanol or tert-pentanol gave chromatograms with improved separation of oxygenated carotenoids compared with acetone-petroleum ether systems. The effects on the retention of the individual compounds due to the presence of oxygenated substitutents were different for the tert-alcohol and acetone systems. The tert-alcohol systems thus provided separations not available with the acetone system.     

Additional modules for versatile and economical PCR-based gene deletion and modification in Saccharomyces cerevisiae

An important recent advance in the functional analysis of Saccharomyces cerevisiae genes is the development of the one-step PCR-mediated technique for deletion and modification of chromosomal genes. This method allows very rapid gene manipulations without requiring plasmid clones of the gene of interest. We describe here a new set of plasmids that serve as templates for the PCR synthesis of fragments that allow a variety of gene modifications. Using as selectable marker the S. cerevisiae TRP1 gene or modules containing the heterologous Schizosaccharomyces pombe his5⁺ or Escherichia coli kan^r gene, these plasmids allow gene deletion, gene overexpression (using the regulatable GAL1 promoter), C- or N-terminal protein tagging [with GFP(S65T), GST, or the 3HA or 13Myc epitope], and partial N- or C-terminal deletions (with or without concomitant protein tagging). Because of the modular nature of the plasmids, they allow efficient and economical use of a small number of PCR primers for a wide variety of gene manipulations. Thus, these plasmids should further facilitate the rapid analysis of gene function in S. cerevisiae. © 1998 John Wiley & Sons, Ltd.     

Effects of bread making methods,lupin variety and gluten powder on the quality of bread enriched with high percentage of lupin flour

Lupin is an economical source of protein, fibre and bioactive compounds, and to obtain these health and nutritional benefits lupin flour has been used in bread production. However, addition of more than 10% lupin flour markedly reduces bread quality mainly due to gluten dilution. The main aim of this research was to retain lupin bread quality enriched with higher percentages of lupin flour (20%) by addition of vital gluten powder (0%, 2%, 3.5% and 5%), investigating the effects of lupin variety (Lupinus albus and L. angustifolius) and two baking systems (rapid and sponge & dough). Impact on bread staling qualities was also determined through texture analysis of samples over a 72-h storage period. Compared to lupin bread with nil gluten addition, significant improvements in loaf volume and crumb texture were observed with addition of gluten powder especially at 5% which increased loaf volume by an average of 20% across lupin sources and baking methods, and crumb softness by 30–50%. Differences were observed between the lupin flour sources. L. angustifolius had a reduced weakening effect when blended with the base flour compared with L. albus. The Sponge & Dough process was found to be more suitable to the inclusion of lupin flour than the rapid process.     

Development of Molecular Typing Methods for Bacillus spp. and Paenibacillus spp. Isolated from Fluid Milk Products

Bacillus spp. and related sporeformers are important food spoilage organisms. While use of molecular subtyping methods has provided important information on the ecology and transmission of foodborne pathogens, the lack of rapid, reliable, and affordable subtyping methods for Bacillus spp. has limited our ability to understand and control their transmission throughout the food chain. We used a previously described collection of Bacillus spp. and Paenibacillus spp. isolated from dairy products to develop a DNA sequencing‐based subtyping approach for these spoilage microorganisms. After optimization of polymerase chain reaction (PCR) parameters, primers targeting the rpoB housekeeping gene allowed for successful amplification in all isolates. rpoB sequencing allowed differentiation of 29 subtypes (that is, sequence types) among the 57 isolates characterized. Phylogenetic analyses of rpoB sequences revealed distinct monophyletic lineages that correlated with bacterial genera (Bacillus and Paenibacillus) as well as with species or species‐like assemblages within each genus. rpoB sequencing provided improved subtype discrimination over 16S rDNA sequencing; therefore, rpoB sequencing allows for both sensitive subtype discrimination as well as for species and genus identification. Analysis of subtypes isolated over time in dairy products revealed the presence of both persistent and transient bacterial subtypes, indicating that application of these methods can improve our understanding of the ecology of these spoilage organisms and can help in identification of bacterial niches that may contribute to the persistence of these spoilage organisms in food systems.     

The sensory quality of dry fermented sausages as affected by fermentation stage and curing agents

The effects on the quality of dry fermented sausages of applying either a slow or rapid fermentation stage, and the addition of either nitrate or nitrite was studied. In the slow fermentation process, TBARS were higher in the batch made with nitrite than in the batch containing nitrate. For rapid fermentation, both batches, with added nitrate and nitrite, presented intermediate TBARS levels. Volatile compounds coming from lipid oxidation and microbial lipid β-oxidation were more abundant (p < 0.05) in the samples submitted to a rapid fermentation stage, whilst compounds coming from amino acid catabolism and carbohydrate fermentation were higher (p < 0.05) in samples subjected to a slow fermentation stage. A significant preference (p < 0.05) was shown during sensory analysis for the batch made with nitrate and submitted to the slow fermentation process in aroma, taste and overall quality, whilst no differences in sensory analysis were detected among batches in the rapid fermentation process. Therefore, the use of nitrate is only justified in slow fermented processes due to its positive effect on the sensory quality of fermented sausages.     

Ingredient Functionality During Foam‐Type Cake Making: A Review

Foam‐type cakes are complex food systems. Their main ingredients are wheat flour, hen eggs, sugar, leavening agent, and, in some cases, oil and/or surfactants. In contrast to the vast amount of research outcomes on the contribution of ingredients to the quality of batter‐type cake systems, information on the functionality and importance of the ingredients and their constituents in foam‐type cake systems is lacking. This review defines foam‐type cakes, describes how they are made, summarizes the current knowledge of factors determining their quality, and identifies the current knowledge gaps.     

Biological Availability and Preliminary Selenium Speciation in Selenium-Enriched Mycelium of Lentinula edodes (Berk.)

Our goal is to obtain a new food supplement — a chemopreventive preparation derived from selenium (Se)-enriched Lentinula edodes mycelium. In the present study the bioavailability of selenium from Se-enriched mycelium preparations was tested in vitro and in vivo. Three different preparations of selenated mycelium were compared: dried mycelium, lyophilized mycelium, and lyophilized-autolyzed mycelium. In vitro, estimated Se bioavailabilities were 60%, 82%, and 98%, respectively. In vivo bioavailability was determined in rats. As reference, sodium selenite and Se yeast formulations were used at an Se-equivalent dose. The pharmacokinetic data for tested mycelial preparations suggest a rapid but incomplete Se absorption, and rapid elimination, without risk of accumulation. The speciation of selenium in Se-enriched mycelial cultures was carried out by specific oxido-reduction reactions. For tested mycelium the main part of Se was in the 0 and IV oxidation states in inorganic form or combined in a lipid or carbohydrate structure, about 47% was in the –II state in Se-amino acids or in other undefined water- or alcohol soluble organic compounds. Differences in pharmacokinetic data for Se yeast and L. edodes mycelial formulations probably arise from differences in Se speciation. Our data suggest that formulations of selenized Lentinula edodes mycelium could be used in chemoprevention as food supplements.     

The stability of pectolytic enzymes in sulphite liquor in relation to breakdown of sulphited strawberries

The stability of pectate and pectin depolymerising enzymes produced by Mucor piriformis, Rhizopus sexualis, R. stolonifer, Botrytis cinerea, Aureobasidium pullulans, Trichosporon pullulans and Cryptococcus albidus var. albidus in sulphite liquor was studied in relation to the breakdown of sulphited fruit. Marked breakdown of fruit occurred only when pectolytic activity could be detected in the liquor for more than 2 weeks using a viscometric assay. Of the fungi tested Rhizopus spp. produced enzymes which were most stable in sulphite liquor. For each of the Mucor and Rhizopus species tested, the stability of polygalacturonases in sulphite liquor was very similar for extracts of infected fruit and culture filtrates. The rapid decrease in polygalacturonase activity for both systems in the first 48 h contrasted with a slower inactivation where infected tissue was used. The reasons for this are discussed and it is suggested that sulphite labile (= acid labile) and sulphite stable (= acid stable) forms of the polygalacturonases are present.     

Progress in microencapsulation of probiotics: A review

The potential health benefits of probiotics may not be realized because of the substantial reduction in their viability during food storage and gastrointestinal transit. Microencapsulation can be used to enhance the resistance of probiotics to unfavorable conditions. A range of oral delivery systems has been developed to increase the level of probiotics reaching the colon including embedding and coating systems. This review introduces emerging strategies for the microencapsulation of probiotics and highlights the key mechanisms of their stress–tolerance properties. Recent in vitro and in vivo models for evaluation of the efficiency of probiotic delivery systems are also reviewed. Encapsulation technologies are required to maintain the viability of probiotics during storage and within the human gut so as to increase their ability to colonize the colon. These technologies work by protecting the probiotics from harsh environmental conditions, as well as increasing their mucoadhesive properties. Typically, the probiotics are either embedded inside or coated with food‐grade materials such as biopolymers or lipids. In some cases, additional components may be coencapsulated to enhance their viability such as nutrients or protective agents. The importance of having suitable in vitro and in vivo models to evaluate the efficiency of probiotic delivery systems is also emphasized.     

Bacillus cereus and Bacillus stearothermophilus Spore Inactivation in Batch and Continuous Flow Systems

Thermal inactivation kinetics were evaluated in batch and continuous flow systems using phosphate buffer between 99 and 107°C for Bacillus cereus T and 128.5 and 139°C for Bacillus stearothermoohilus ATCC 12980 spores. z_D-Values for B. cereus spores in batch aid continuous flow systems were not significantly different; the continuous flow system was more lethal than the batch system. z_D-Values obtained using B. stearothermophilus spores in batch and continuous flow systems were different; the batch system was more lethal than the continuous flow system. Thus, use of batch generated data to predict or design continuous flow processes may not be accurate.     

EVALUATION OF FLUORESCENT IN SITU HYBRIDIZATION (FISH) AS A RAPID SCREENING METHOD FOR DETECTION OF SALMONELLA IN TONSILS OF SLAUGHTERED PIGS FOR CONSUMPTION: A COMPARISON WITH CONVENTIONAL CULTURE METHOD

The pork tonsils are an important carrier of Salmonella, which could be involved in the contamination of pork products during the slaughter process. This paper reports a 23S rRNA fluorescent in situ hybridization (FISH) method used as a rapid screening tool for Salmonella detection in tonsils of slaughtered pigs and its comparison with the conventional culture method. As a rapid screening method, the FISH technique would reduce the high volume of negative samples that are routinely analyzed, indicating presumptive positive samples in a real and practical time. The use of a Sal3 probe allowed the rapid (7 h) Salmonella detection in 16 (34%) of 47 naturally contaminated tonsils, without pre‐enrichment. Salmonella was isolated by the culture method in six samples that were also FISH‐positive samples, and FISH failed to identify only one of the culture‐positive samples. The results indicate the potential of this technique as a rapid screening method for detecting Salmonella in tonsils from pork slaughtered for consumption.     

Biofilm formation in the industry: A review

Abstract

Biofilm and biofouling refer to biological deposits on any surface. Biofilms consist of both microbes and their extracellular products, usually polysaccharides. The purpose of biofilm is to protect the microbes from hostile environments or to act as a trap for nutrient acquisition. Biofilm formation causes problems in many branches of industry, such as in industrial water systems and the medical and process industries. Besides causing problems in cleaning and hygiene, biofilm may cause energy losses and blockages in condenser tubes, cooling fill materials, water and wastewater circuits, and heat exchange tubes, and on ship hulls. Biofilm can also present microbial risks due to the release of pathogens from cooling towers or by reducing water quality in drinking water distribution systems. In the medical industry biofilm is referred to as glycocalyx when diseases of the lungs or the gastrointestinal or urinary tract are involved.     

Detection of External and Internal Insect Infestation in Wheat by Near-Infrared Reflectance Spectroscopy

Near-infrared spectroscopy (NIR) in the reflectance mode was investigated for the rapid, automatic and non-destructive detection of insect stored-grain pests external or internal to wheat kernels. Convincing calibration performance was obtained for external adult Oryzaephilus surinamensis (L) (saw-toothed grain beetle) in unmilled samples including varieties Beaver (soft wheat) and Mercia (hard wheat) at two moisture contents. With this large substrate variability, the method could differentiate between uninfested samples and samples with approximately 270 insects kg⁻¹ or more. Milling made no improvement. Large spectral differences were observed between uninfested kernels and kernels infested internally with Sitophilus granarius (L) (grain weevil) larvae or pupae, arising from both a changed chemical composition and physical structure. Single uninfested and infested kernels were discriminated by their second derivative (d²) spectra. For both external and internal infestation there was substantial evidence that insect protein and/or chitin and moisture were being detected. NIR should be useful as a rapid method of detection.     

Determination of polycyclic aromatic hydrocarbons (PAHs) in commonly consumed Nigerian smoked/grilled fish and meat

Smoking and/or grilling, when carried out with traditional methods involving direct contact with wood combustion fumes, is responsible for high contamination levels with carcinogenic polycyclic aromatic hydrocarbons (PAHs). The aim of this work was to investigate the PAH content of different smoked or grilled meat and fish products commonly consumed in Nigeria. A rapid method involving microwave-assisted saponification and simultaneous extraction followed by solid-phase extraction (SPE), high-performance liquid chromatography (HPLC) separation and spectrofluorometric detection was employed. Samples that were smoked or grilled using traditional systems, which use a wood fire, were heavily contaminated with benzo[a]pyrene (BaP) at levels ranging from 2.4 to 31.2 µg kg^?1 wet weight. Considerably lower contamination levels were found in samples smoked or grilled in the laboratory using a charcoal fire (BaP from 0.7 to 2.8 µg kg^?1 wet weight). The health risk associated with a daily consumption of 100 g of these products was also evaluated using the margin of exposure (MOE) approach. MOE values lower than 10,000 were obtained for all smoked/grilled commercial samples, indicating a potential concern for consumer health.     

Identification of Genetically Modified Zebrafish ( Danio rerio ) by Protein- and DNA-Analysis

The import, sale and possession of fluorescent transgenic zebrafish, offered under the name “GloFish^?” in U.S. aquarium shops, are not permitted in the European Union. A PCR-based method has been developed to detect transgenic zebrafish harbouring the gene (dsRed) coding for the red fluorescent protein, originally isolated from the marine sponge Discosoma striata. Two types of PCR have been performed: (i) PCR to detect amplifiable genomic zebrafish DNA was checked using primers specific for the zebrafish parvalbumin gene; (ii) PCR with primers to specifically amplify the dsRed gene. In both PCR systems, genomic DNA isolated from wild type zebrafish was used as control template, in the second PCR system, the plasmid dsRed2-N1 was used as a positive control. Applying this method to several specimens of presumed GloFish^? from traders in the Netherlands and Germany revealed the presence of transgenic fish. In addition, a rapid method for screening zebrafish suspected to be genetically modified has been developed by measuring the fluorescence of water-soluble protein.     

Improvement in regression of corn yield with plant height using relative data

BACKGROUND: The traditional approach of analyzing absolute variable data across multiple locations and/or years has drawbacks in precision agriculture. This study was conducted to evaluate the impacts of using relative yield and plant height data of corn (Zea mays L.) on the regression of yield with plant height using linear and exponential models in a nitrogen (N) rate field trial under four cropping systems. RESULTS: The use of relative yield to replace absolute yield frequently increased the determination coefficient (R²) values in the regression of yield with plant height on datasets combined across cropping systems or/and years. Relative yield and relative plant height sometimes further enhanced the R² values compared with relative yield and absolute plant height. All these improvements mostly occurred when the fit of the model was not strong with absolute yield and absolute plant height or relative yield and absolute plant height. The advantages of using relative data of yield or/and plant height were similar for the two regression models. CONCLUSION: The use of relative yield or relative data of both yield and plant height may be effective in improving the regression of corn yield with plant height across multiple cropping systems/locations and years in precision agriculture. Copyright © 2011 Society of Chemical Industry