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Food Preservation (food + preservation)
Selected AbstractsThree-dimensional MRI mapping of minimum temperatures achieved in microwave and conventional food processingINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 3 2001John R. Bows Microbiological assurance protocols for food preservation are based on the ,worst-case' slowest heating point within the food product. For conduction-limited processing, this leads to well-known overheating near surface regions of products, with resultant quality loss. For volumetric heating processes such as microwave heating, it is practically impossible to guarantee where the slowest heating point will be. Consequently, microwave heating regimes are generally excessive and product quality is often similar to conventional conduction-limited heating processes. It is well known that Magnetic Resonance Imaging (MRI) can provide three-dimensional (3D) images which quantify the spatial distribution of water in foods, and also that the MRI parameters of water are temperature dependent. The present study demonstrates that a combination of these two concepts has led to a new approach for the validation of thermal processing in food manufacture. The potential for on-line assurance of minimum and maximum temperatures for manufacture of microbiologically assured, minimally processed, high quality food is discussed. [source] Growth inhibition of Listeria monocytogenes by a nonbacteriocinogenic Carnobacterium piscicolaJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2005L. Nilsson Abstract Aims:, This study elucidates the mechanisms by which a nonbacteriocinogenic Carnobacterium piscicola inhibits growth of Listeria monocytogenes. Methods and Results:,Listeria monocytogenes was exposed to live cultures of a bacteriocin-negative variant of C. piscicola A9b in co-culture, in a diffusion chamber system, and to a cell-free supernatant. Suppression of maximum cell density (0,3·5 log units) of L. monocytogenes was proportional to initial levels of C. pisciola (103,107 CFU ml,1). Cell-to-cell contact was not required to cause inhibition. The cell-free C. piscicola supernatant caused a decrease in L. monocytogenes maximum cell density, which was abolished by glucose addition but not by amino acid, vitamin or mineral addition. The fermentate also gave rise to a longer lag phase and a reduction in growth rate. These effects were independent of glucose and may have been caused by acetate production by C. piscicola. 2D gel-electrophoretic patterns of L. monocytogenes exposed to C. piscicola or to L. monocytogenes fermentate did not differ. Treatment with C. piscicola fermentate resulted in down-regulation (twofold) of genes involved in purine- or pyrimidine metabolism, and up-regulation (twofold) of genes from the regulon for vitamin B12 biosynthesis and propanediol and ethanolamine utilization. Conclusions:, A nonbacteriocinogenic C. piscicola reduced growth of L. monocytogenes partly by glucose depletion. Significance and Impact of the Study:, Understanding the mechanism of microbial interaction enhances prediction of growth in mixed communities as well as use of bioprotective principles for food preservation. [source] Occurrence of sublethal injury after pulsed electric fields depending on the micro-organism, the treatment medium ph and the intensity of the treatment investigatedJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2005D. García Abstract Aims:, The objective was to investigate the occurrence of sublethal injury after pulsed electric field (PEF) depending on the treatment time, the electric field strength and the pH of the treatment media in two Gram-positive (Bacillus subtilis ssp. niger, Listeria monocytogenes) and six Gram-negative (Escherichia coli, Escherichia coli O157:H7, Pseudomonas aeruginosa, Salmonella serotype Senftenberg 775W, Salmonella serotype Typhimurium, Yersinia enterocolitica) bacterial strains. Methods and Results:, A characteristic behaviour was observed for the Gram-positive and Gram-negative bacteria studied. Whereas Gram-positive bacteria showed a higher PEF resistance at pH 7·0, the Gram-negative were more resistant at pH 4·0. In these conditions, in which bacteria showed their maximum resistance, a large proportion of sublethally injured cells were detected. In most cases, the longer the treatment time and the higher the electric field applied, the greater the proportion of sublethally injured cells that were detected. No sublethal injury was detected when Gram-positive bacteria were treated at pH 4·0 and Gram-negative at pH 7·0. Conclusions:, Sublethal injury was detected after PEF so, bacterial inactivation by PEF is not an ,all or nothing' event. Significance and Impact of the Study:, This work could be useful for improving food preservation by PEF. [source] PURIFICATION AND CHARACTERIZATION OF BACTERIOCIN FROM WEISSELLA PARAMESENTEROIDES DFR-8, AN ISOLATE FROM CUCUMBER (CUCUMIS SATIVUS)JOURNAL OF FOOD BIOCHEMISTRY, Issue 5 2010AJAY PAL ABSTRACT Bacteriocin from Weissella paramesenteroides DFR-8 isolated from cucumber (Cucumis sativus) was purified by using only two steps, viz., pH-mediated cell adsorption,desorption method and gel permeation chromatography. A single peak observed in the purity check by analytical Reverse Phase-High Performance Liquid Chromatography (Waters 600 analytical HPLC system, Milford, MA) and a single band (molecular weight,3.74 kDa) shown on SDS-PAGE analysis strongly indicated the homogeneity of the bacteriocin preparation. Treatment with proteolytic enzymes abolished the antimicrobial activity indicating the proteinaceous nature of bacteriocin. The purified bacteriocin exhibited a broad inhibitory spectrum against foodborne pathogens and spoilage microorganisms, including gram-negative bacteria such as Salmonella typhimurium, Vibrio parahaemolyticus, Aeromonas hydrophila and Listeria monocytogenes. Response surface methodology was employed to study the interactive effect of temperature and pH on bacteriocin activity, and a regression equation was developed. The bacteriocin retained full activity after storage at,20C for 90 days, while partial and complete activity loss was observed when stored at 4 and 37C, respectively. PRACTICAL APPLICATION In recent years, bacteriocins of lactic acid bacteria have gained much attention as food biopreservatives because of their origin from generally regarded as safe organisms. In spite of various bacteriocins studied worldwide, studies on bacteriocins of Weissella paramesenteroides remain rare. The present work involves the purification of bacteriocin up to absolute homogeneity from W. paramesenteroides, an isolate first time reported from cucumber (Cucumis sativus). The purified bacteriocin (molecular weight ,3.74 kDa) was found to inhibit a large number of foodborne pathogens, including Listeria monocytogenes, which is resistant to commercially available bacteriocin, i.e., nisin. The application of central composite rotatable design enabled us to design a regression equation from which the residual activity of bacteriocin can be predicted at any given conditions of temperature and pH within the experimental domain. The broad inhibitory spectrum and thermostability of bacteriocin suggest its potential application in food preservation. [source] ESSENTIAL OIL COMPOSITION OF SALVIA VERBENACA L. GROWING WILD IN TUNISIAJOURNAL OF FOOD BIOCHEMISTRY, Issue 1 2010MOUNA BEN TAARIT ABSTRACT The essential oil of aerial parts of Salvia verbenaca L., collected in three different locations in Tunisia, were obtained by hydrodistillation and analyzed by gas chromatography (GC) and GC,mass spectrometry. The oil yields of dried plants (w/w) were 0.09, 0.10 and 0.12% in Sabelet Ben Ammar, Sers and Somaa, respectively. Seventy-seven compounds were identified. The monoterpene hydrocarbons and oxygenated sesquiterpenes had the highest contributions. The major constituents in Sabelet Ben Ammar were viridiflorol (21.8%), camphene (17.6%), methyl eugenol (9.4%) and ,-caryophyllene (7.1%), while those of essential oil collected from Somaa, were tricyclene (18.8%), nonane (10.3%), methyl eugenol (7.7%) and terpinolene (7.3%). In samples collected from Sers, essential oil consists mainly of (Z)-,-ocimene (29.5%), ,-phellandrene (8.2%), ,-thujone (7.9%) and ,-pinene (5.5%). PRACTICAL APPLICATIONS In this study, it has been found that the oils of wild-growing Salvia verbenaca L. in Tunisia are rich in oxygenated sesquiterpenes and monoterpene hydrocarbons with great economical values. The plant family Labiatae contains several species with potential therapeutic activity due to their essential oils. Pharmacology, pharmaceutical botany, medical and clinical microbiology, phytopathology and food preservation are some fields in which essential oils can be applied. Many Salvia spp. are used as herbal tea and for food flavoring, as well as in cosmetics, perfumery and the pharmaceutical industry. It has shown that essential oil of S. verbenaca have strong antibacterial, antioxidant, antifungal, anti-inflammatory activities and peripheral analgesic properties. [source] DRYING OF CHILI PEPPER (CAPSCIUM FRUTSCENS)JOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2010T.Y. TUNDE-AKINTUNDE ABSTRACT Drying is one of the common methods of food preservation and is carried out on untreated/unblanched and treated/blanched chili pepper using sun, solar and hot-air drying. The drying curves generated from the three methods showed that drying of treated/blanched pepper was faster than that of untreated/unblanched pepper. The drying rate period observed for all the methods and samples was the falling rate drying regime. This suggests that the blanching pretreatment assisted water loss and thus decreased the resistance to water loss at the surface of the product. The drying time of the dried pepper varied from 27 h for hot-air drying to 144.5 h for sun drying respectively. The values of moisture diffusivity coefficient ranged from 2.163 × 10,9 m2/s for hot-air drying to 1.125 × 10,9 m2/s for sun drying. PRACTICAL APPLICATIONS A common method of preserving pepper, a vegetable with versatile use, is drying and this is done by sun, solar and oven-drying methods. Climatic variations of sun and solar drying make it unsuitable for large-scale production. Hot-air drying is thus considered as an alternative drying method because it decreases drying time and improves the hygienic quality of the dried product. Pretreating pepper by blanching increases its rate of drying. The effect of each drying method on the drying rate, equilibrium moisture content and moisture diffusivity coefficient were used to compare the drying methods. Hot-air drying had the lowest drying time whereas pretreated samples also dried faster. The effective moisture diffusivity of oven dried samples as well as pretreated samples were highest. This indicates that oven drying reduces drying time and can be used to dry pepper samples for large-scale production. [source] ANTIBACTERIAL ACTIVITY AND CHEMICAL CONSTITUTIONS OF OLEA EUROPAEA L. LEAF EXTRACTSJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 3 2010MIHRIBAN KORUKLUOGLU ABSTRACT The in vitro antimicrobial activity of aqueous, acetone, diethyl ether and ethyl alcohol extracts of olive leaves (Olea europaea L.) was studied. The aqueous extract of olive leaves had no antibacterial effect against the test microorganisms, whereas acetone extract showed inhibitory effect on Salmonella enteritidis, Bacillus cereus, Klebsiella pneumoniae, Escherichia coli, Enterococcus faecalis, Streptococcus thermophilus and Lactobacillus bulgaricus. Furthermore, the antimicrobial activities of some phenolic compounds against microorganisms were tested. The most effective compound was found to be oleuropein while syringic acid was found ineffective. The characterization of phenolic compounds in different extracts determined by high performance liquid chromatography-air pressure chemical ionization-mass spectrometry detector (HPLC-APCI-MSD GC-MS) gas chromatography-mass spectrometry (GC-MS). The acetone and the ethyl alcohol extracts had the most and the least oleuropein content, respectively. PRACTICAL APPLICATIONS In recent years the extracts of many plant species have become popular, and attempts to characterize their bioactive principles have gained speed for many pharmaceutical and food-processing applications. Especially, antimicrobial properties of plants have revived as a consequence of current problems associated with the use of chemical preservatives. Because of consumers' negative perspectives of synthetic preservatives, attention is shifting toward natural alternatives. The findings suggest that olive leaf extracts and their phenolic compounds have good potential as antibacterial substances in food preservation as they may be more acceptable to consumers and the regulatory agencies in comparison with synthetic chemical compounds. [source] A PREDICTIVE MODEL FOR HIGH-PRESSURE CARBON DIOXIDE INACTIVATION OF MICROORGANISMSJOURNAL OF FOOD SAFETY, Issue 2 2009S. BUZRUL ABSTRACT The Weibull model, which is commonly used for thermal inactivation of microorganisms in literature, was used to describe microbial inactivation by high-pressure carbon dioxide (HPCD). The number of parameters of the model was reduced from two to one in order to avoid interrelationship of these parameters with a slight loss of goodness-of-fit. A second-order polynomial function fulfilling a number of constraints was proposed for the secondary modeling of the time-constant parameter of the reduced Weibull model. This function consists of both pressure and temperature and therefore can be used for HPCD treatments. PRACTICAL APPLICATIONS The application of any new technology in food preservation requires a reliable model that accurately describes and predicts the inactivation data of microorganisms. In principle, the methodology presented here could be used to describe and predict the survival data for high-pressure carbon dioxide inactivation of microorganisms at least for some pressure and temperature ranges if the isobaric/isothermal survival curves of these microorganisms are linear, concave upward or downward. [source] CHEMICAL CHARACTERIZATION AND ANTIFUNGAL ACTIVITY OF ORIGANUM ONITES L. ESSENTIAL OILS AND EXTRACTSJOURNAL OF FOOD SAFETY, Issue 1 2009MIHRIBAN KORUKLUOGLU ABSTRACT Essential oils (EOs) and extracts (methanol, acetone and diethyl ether) of fresh and dried oregano (Origanum onites L.) were used to determine the antifungal effect on Alternaria alternata, Aspergillus flavus (two strains), Aspergillus niger (two strains), Aspergillus parasiticus, Fusarium semitectum, Fusarium oxysporum, Mucor racemosus and Penicillium roqueforti by disk diffusion methods. Minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of all samples were determined. The antifungal activity of the fresh herb was greater than that of the dried herb. MIC values for fresh and dried methanol extracts were 150,950 µg/mL and 750,950 µg/mL, respectively. MFC values for methanol extracts were determined between 300 and 1200 µg/mL for fresh oregano and between 750 and 1100 µg/mL for dried oregano. The EOs of fresh and dried oregano totally inhibited test fungi. EOs produced the lowest MIC and MFC values: 8.5 µg/mL and 9.0 µg/mL, respectively (P < 0.005). The highest extract activity was exhibited by fresh oregano against A. alternata (24 mm) followed by P. roqueforti (20 mm). The greatest total antifungal effect was observed from methanol extracts. The chemical composition of fresh oregano EO and extracts was examined using gas chromatography-mass spectrometry (GC-MS). Over 80 volatiles were detected, of which 42 were positively identified by matching both MS fragmentation patterns with standardized retention characteristics. p-Cymene, thymol and carvacrol were the most prominent, followed by ,-pinene, camphor and borneol. PRACTICAL APPLICATIONS In the past decade interest in natural antimicrobial plant extracts has been growing. Various plants have historically been used for the purposes of food preservation and flavor enhancement as well as medicinal purposes. An example is oregano, the leafy part of the plant belonging to the Labiatae family. It has been used to improve the flavor and the organoleptic properties of many foods from numerous cultures. It has also been used to prolong the storage life of foods probably because of antifungal properties. The preservative nature of fresh oregano has been employed in many food applications, including meat and fish products, as well as in pharmaceuticals, alternative medicines and natural therapies. [source] Keeping quality of tomato fruit by high electrostatic field pretreatment during storageJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2008Yu Wang Abstract BACKGROUND: High electrostatic field, as a feasible and non-chemical technique, applied to food preservation is a new area of study. The present article intensively investigated this new preservation method, together with its effects on post-harvest physiology and quality of tomato. RESULTS: Green mature tomatoes were exposed to negative (or positive) high electrostatic field for 2 h at 20 °C and then stored for 30 days at 13 ± 1 °C, 85,90% RH. Our results indicated that negative high electrostatic field (,2 kV cm,1) could delay the decline of firmness and the change in color, total soluble sugar and titratable acidity of tomato fruit during storage. The peak of respiration and ethylene production of tomato fruit during storage were delayed by negative high electrostatic field treatment for 6 days and 3 days, respectively. Increases of malondialdehyde content and electrical conductivity in tomato fruit were inhibited significantly by negative high electrostatic field treatment during storage (P < 0.05). CONCLUSION: A high electrostatic field of , 2 kV cm,1 can be used to keep the qualities and extend the shelf-life of tomato fruit. Further research should be highly recommended to understand the mechanisms improving the storability of tomato fruit by negative high electrostatic field. Copyright © 2007 Society of Chemical Industry [source] Comparative proteome approach to characterize the high-pressure stress response of Lactobacillus sanfranciscensis DSM 20451TPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 6 2006Sebastian Hörmann Abstract High hydrostatic pressure (HHP) exerts diverse effects on microorganisms, leading to stress response and cell death. While inactivation of microorganisms by lethal HHP is well investigated in the context of food preservation and the hygienic safety of minimal food processes, sublethal HHP stress response and its effect on adaptation and cross-protection is less understood. In this study, the HHP stress response of Lactobacillus sanfranciscensis was characterized and compared with cold, heat, salt, acid and starvation stress at the proteome level by using 2-DE so as to provide insight into general versus specific stress responses. Sixteen proteins were found to be affected by HHP and were identified by using N-terminal amino acid sequencing and MS. Only one slightly increased protein was specific to the HHP response and showed homology to a clp protease. The other proteins were influenced by most of the investigated stresses in a similar way as HHP. The highest similarity in the HHP proteome was found to be with cold- and NaCl-stressed cells, with 11,overlapping proteins. At the proteome level, L.,sanfranciscensis appears to use overlapping subsets of stress-inducible proteins rather than stereotype responses. Our data suggest that a specific pressure response does not exist in this bacteria. [source] Nitrite anions induce nitrosative deamination of peptides and proteinsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2006Haiteng Deng In the present study, reactions of sodium nitrite with proteins/peptides were characterized with mass spectrometry. The reaction generates two major products: replacement of the amino group by a hydroxyl group and formation of an alkene derivative by loss of a NH3 group at the N-terminus and the side chain of lysine residues of proteins/peptides. The reaction proceeds rapidly in weak acidic solution and at 37°C in the presence of a millimolar concentration of nitrite, demonstrating that nitrite induces nitrosative deamination in proteins and peptides. The facile nitrite-induced modification of amino groups of protein/peptides changes the chemical nature of proteins and may have various applications in peptide synthesis, analytical chemistry, and protein engineering. It also provides information to enhance our understanding of functions of nitrite ions in biology and food preservation. Copyright © 2006 John Wiley & Sons, Ltd. [source] Stress Response of Escherichia coliCOMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY, Issue 3 2006H.J. Chung ABSTRACT:,Escherichia coli encounter numerous different stresses during their growth, survival, and infection. These stresses are relevant to survival in foods and food processing environments. E. coli and other bacteria respond to stress conditions by activating small or large groups of genes under the control of common regulator proteins. Stress conditions result in the accumulation of these regulator proteins and subsequent transcription of many genes allows cells to cope with specific stress situations, conferring stress tolerance and survival. In addition, induced stress tolerance of cells is attributed to enhanced virulence and enhanced tolerance to other stresses (cross-protection). In this review, regulation of stress and the stress tolerance response of E. coli to heat, acid, starvation, and cold stresses that are commonly used in food preservation and food production will be addressed. The effect of different stress on survival, adaptation, and cross-protection of E. coli studied using laboratory media, and real foods will be briefly summarized. Finally, the relationship of stress response and subsequent virulence and cross-protection will also be discussed. [source] | ||||||||||