Organic Acids

Organic acids such as lactic and acetic acids are effective antibacterial agents 97 and are classified by the FDA as GRAS 98,99 (21CFR184.1005 21CFR184.1061). Lactic acid dips and sprays are used commercially to decontaminate animal carcasses containing E. coli O157 H7, L. monocytogenes, and salmonella 100 (see additional information from Purac America, Inc., www.purac.com). Lactic acid rinses might have applications for the decontamination of fruits and vegetables. A 5 acetic acid wash was...

Microflora Of Melons

Melons, especially cantaloupe, present a variety of surfaces to which microorganisms may bind. In cantaloupe the epidermal cell surface is ruptured with a meshwork of raised tissue (the net). This net consists of lenticels and phellum (cork) cells. These cells have hydrophobic suberized walls to reduce water loss and protect against pathogen ingress. Also imparting a hydrophobic nature to the outer surface of cantaloupe is the cuticle composed of waxes and cutin that cover the epidermal cells...

Contamination By Human Pathogens

While produce quality can be judged by outward appearance based on such criteria as color, turgidity, and aroma, food safety cannot. Casual inspection of produce cannot determine if it is in fact safe and wholesome to consume. Most fresh fruits and vegetables are grown in nonsterile environments, and conventional fruit and vegetable growers have less control over conditions in the production field as compared to an enclosed production or food preparation facility. The surfaces of produce have...

Applications 2631 Spatial Distribution

The microscopic investigation of the localization of human or plant pathogenic bacteria on plant surfaces has provided new insights into their ecology in that environment. The observations by confocal microscopy that GFP-labeled Salmonella enterica formed microcolonies on the leaves of cilantro plants provided evidence that this enteric pathogen has the ability to colonize plants in a preharvest environment and may cause outbreaks due to contamination that occurred in the field 19 ....

Properties

Allyl isothiocyanate (AITC) is the major component in essential oils of cruciferous plants, such as black mustard seeds (Brassica nigra), brown mustard seeds (Brassica juncea), cabbage (Brassica oleracia), and horseradish (Armoracia rusticana) 101,102 . AITC is a specific compound from the isothiocyanate (ITC) group that has been shown to have bactericidal, bacteristatic, and antifungal activities. AITCs are released upon disruption or injury of plant tissue due to hydrolysis of glucosinolates...

Application to Juices

PEF research had been mostly focused on the inactivation of microorganisms suspended in foods, including semisolid and liquid foods such as pea soup, milk, liquid eggs, and juices, particularly orange and apple juices. Sitzmann 67 obtained a 3 log10 reduction of native microbiota for freshly squeezed orange juice using a continuous PEF process with an electric field of 15kV cm. There was no significant change in quality. Zhang et al. 68 found that total aerobic counts of reconstituted orange...

Assessing Stress Adaptation And Associated Risks

Safety of food may be achieved using treatment factors that halt the growth of pathogens. The optimization of these treatments requires an understanding of the limits between conditions that support growth and those in which growth is not possible, also known as the growth-no-growth interface 96 . The growth-no-growth interface can be defined as the boundary at which the microbial growth rate is zero and the lag phase is infinite 97 . The behavior of foodborne pathogens at the growth-no-growth...

Instrumentation And Biomass Measurements

As the field of rapid methods and automation has developed, the boundaries between instrumentation and diagnostic tests have begun to merge. Instrumentation is now playing an important function in improving the efficiency of diagnostic kit systems, and the trend will continue. The following discussions are mainly on instrumentation measuring signals related to microbial growth. Instruments can be used to monitor changes in a population such as ATP levels, levels of specific enzymes, pH,...

Generation of Ozone

Ozone is commonly produced from oxygen or air by utilizing ultraviolet (UV) light or corona discharge generators. UV light systems use radiation at 185 nm wavelength emitted from high-transmission UV lamps. These systems are relatively low cost and do not require dry air for ozone production. The corona discharge generators can produce larger concentrations of ozone, up to 4 , compared to UV light systems. They mainly consist of two electrodes separated by a dielectric or nonconducting...

Info

Forney, C.F. et al., Vapor phase hydrogen peroxide inhibits postharvest decay of table grapes, HortSci., 26, 1512, 1991. Aharoni, Y., Copel, A., and Fallik, E., The use of hydrogen peroxide to control postharvest decay on Galia melons, Ann. Applied Biol., 125, 189, 1994. Simmons, G.F. et al., Reduction of microbial populations on prunes by vapor-phase hydrogen peroxide, J. Food Prot., 60, 188, 1997. Sapers, G.M. and Simmons, G.F., Hydrogen peroxide disinfection of minimally processed fruits and...

Visualization Of Bacteria On Plants Available Tools

26.2.1 Labeling of Bacteria with Fluorescent Proteins The recent renaissance in the application of microscopy to the study of bacterial behavior on plants is largely attributable to the discovery of GFP. The popularity of GFP as a fluorophore lies in its bright and relatively stable fluorescence, the expression of gfp in most bacterial species, and the ability to use it as an intrinsic label without the need for a substrate. The latter property means that samples can be mounted without prior...

Organic Acids And Destruction Of Pathogens

Organic acid preservatives have widespread application for preventing food spoilage and contribute to the manufacture of safe food products 87-89 . The survival or death of pathogenic bacteria in acid and acidified foods has been investigated in a variety of products, including apple cider 68,90-93 , mayonnaise, dressings and condiments 76,84,94,95 , and fermented meats 96-98 . The mechanism of action of organic acids is commonly attributed to acidification of the cytoplasm of target cells, but...

Biological Fumigation

The production of volatile antibiotics is rare among microorganisms and has been reported only in a few soilborne organisms such as Trichoderma spp. and Bacillus spp. 32,33 . A recently discovered fungus, Muscodor albus, produces about 28 volatile compounds, mainly alcohol, ester, ketone, and acid derivatives, which together can inhibit or kill fungi, bacteria, and oomycetes 34 . The fungus, which was isolated from a cinnamon tree in Honduras, was described as a new genus and is related to...

Immunological Testing

The antigen and antibody reaction has been used for decades for detecting and characterizing microorganisms and their components in medical, food, and diagnostic microbiology. This reaction is the basis for serotyping bacteria such as salmonella, Escherichia coli O157 H7, and Listeria monocytogenes. These antibodies can be polyclonal (a mixture of several antibodies in the antisera which can react with different sites of the antigens) or monoclonal (only one pure antibody in the antiserum which...

Industrial Importance

7.5.1 Emergence as Spoilage Organisms Food manufacturers continually investigate innovations in product development, processing aids, and processing equipment to meet changing consumer demands in order to maintain adequate profit margins. Changes in products and manufacturing procedures frequently result in unique quality and stability challenges. For example, in the 1980s and 1990s the use of oxygen barrier films in gable-top cartons allowed orange juice packers to increase refrigerated shelf...

General Gas Vapor Treatment Systems

Batch and continuous ClO2 gas treatment systems have been developed and used for decontamination of fruits and vegetables 31-34,36-38,40-42 . Typically, the batch system (Figure 18.4) includes a ClO2 gas generator (such as a bench-scale CDG Technology or ClorDiSys Solutions generator), a treatment chamber, a diaphragm vacuum pump, and a thermo-hydro recorder. Produce samples are placed on expanded stainless steel shelves inside the chamber. ClO2 gas is generated from the generator and is stored...

Establishing Spc Monitoring Procedures Haccp Principle

Selection of the correct monitoring system is an essential part of any HACCP study because it is what the HACCP team relies upon to maintain control at the CCPs. By definition, monitoring is a planned sequence of observations or measurements to assess whether a CCP is under control and produces an accurate record for future use in verification 7 . Monitoring serves to (1) track the operation of a process and enable the identification of trends toward a CL that may trigger process adjustment (2)...

Stress Adaptation and the General Stress Response

Exposure of a microorganism to stress triggers a series of metabolic responses that may adapt the cell to subsequent lethal levels of the same type of stress or to multiple lethal stresses. The cell's adaptive response is generally referred to as stress adaptation. Stress, ensuing adaptive response, and the manifestation of this phenomenon in food preservation are collectively described as stress hardening. Food microbiota are regularly subjected to stress hardening. Therefore, the stress...

References

Beuchat, L.R., Surface Decontamination of Fruits and Vegetables Eaten Raw A Review, Food Safety Unit, World Health Organization, WHO FSF FOS 98.2, 1998. 2. FDA, Methods to reduce eliminate pathogens from fresh and fresh-cut produce, in Analysis and Evaluation of Preventative Control Measures for the Control and Reduction Elimination of Microbial Hazards on Fresh and Fresh-cut Produce, U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, 2001, chap. V 3. Sapers, G.M.,...

Tomatoes and Apples and Salmonella

Outbreaks of salmonella illness associated with raw tomatoes have been reported 140,141 . Tomatoes inoculated with high doses of S. Montevideo (SeM) and stored for 3 days retained viable cells on skin and stem scars 142 . However, SeM survived at 2 to 4 log10 higher concentrations in scars and cracks compared to skin, both after washes in water and 100 mg ml aqueous chlorine. Tomato plants inoculated at stems or flowers with a combination of five different S. eraierzca serovars including SeM...

Thermal Resistance Characteristics 741 D And Zvalues

Although juice spoilage from heat-resistant molds has been known for decades, the thermal resistance of spore-forming bacteria in low pH fruit juice and beverages was of little concern to fruit juice manufacturers prior to the 1990s. Despite the isolation of thermoacidophilic spore-formers from apple juice in 1982 1 , the importance of this genus to juice stability and consumer acceptance received little attention until reports of spoilage surfaced in the early 1990s from Europe and the U.S....

Antimicrobial Activity Of Map Gases 1921 Co2

Dissolved CO2 has been found to inhibit microbial growth 3-5 , affecting the lag phase (a), maximum growth rate ( max)m and or maximum population (Nmax) densities reached levels in excess of 5 in MAP systems have been found to be bacteriostatic 6 . The mode of action, although not yet fully understood, is thought to be due to a number of effects, including changes in intracellular pH, alteration of microbial protein and enzyme structure and function, and alteration of cell membrane function and...

Overview Of Internalized Microorganisms

Microorganisms embedded in plant tissues may be defined as internalized, derived from internal, meaning located inside the plant surface. Functionally, internalized microbes cannot be washed off the plant, they are protected from environmental stresses, and they cannot be inactivated by contact bio-cides or other surface disinfectants. Inside the plant, most microorganisms are located in spaces between cells called intercellular spaces, whereas plant viruses and certain other pathogens are...

Efficacy of Surface Pasteurization Process Using Hot Water Immersion on Salmonella Poona Populationsa on Inoculated

2 h control 24 h control 76 C for 3min 3.66 0.43 3.31 0.16 0.10 0.00d 4.23 0.32 3.66 0.43 5.54 0.09 0.16 0.08d 5.08 0.20 a S. Poona populations were selectively isolated on XLT4 agar medium, and reported as log CFU cm2 rind. b Data are reported as the mean standard deviation for three separate cantaloupes. c Cantaloupes were dip inoculated with S. Poona for 5 min, allowed to air dry under biosafety cabinet for 2h, and were stored at either room temperature or 4 C for 24 h prior to washing...

Enzymatic And Molecular Mechanism Of Tissue Maceration By Softrot Bacteria

5.4.1 Biochemical Characterization of Pectate Lyase (PL) 5.4.1.1 Analysis of PL Isozymes Soft-rot erwinia including Ech, Ecc, and Eca are characterized by their ability to produce an array of pectolytic enzymes including pectin methylesterase (PME), polygalacturonase (PG), pectin lyase (PNL), and pectate lyase (PL). These enzymes can be readily detected in filtrates of bacterial cultures and assayed by the standard biochemical procedures 58 . The PLs produced by Ech, Ecc, and Eca are usually...

Film Permeability and CO2O2 Permselectivity

The specific gases employed, the gas permeability coefficients of the film, and the EMA desired will in part dictate the packaging films utilized. Concentrations of the two most commonly metabolically active gases employed in MAP, O2 and CO2, will impact produce quality and levels of both should be optimized within the package. CO2 O2 permselectivity, the ratio of CO2 to O2 permeation coefficients, will vary for different films and can be selected or altered to concurrently optimize levels of...

Microbiology Of Fresh Mushrooms

Doores et al 19 demonstrated that normal healthy mushrooms have high bacterial populations. Total bacterial numbers ranged from 6.3 to 7.2 log CFU g of fresh mushroom tissue. The majority (54.0 ) of bacteria isolated from the mushrooms were identified as fluorescent pseudomonads with flavobacteria comprising the second largest group (10.0 ). Recent experiments in our laboratory have confirmed this pattern, but we have also been able to isolate the chryseobacterium genus (5.5 log CFU g) and the...

Advantages and Disadvantages of Application

In the thermal processing of foods, heat inactivates both microorganisms and enzymes to extend the shelf life of the treated foods. With application and incorporation of nonthermal processing methods the same microorganisms and enzymes in the food are usually targeted with the same expectation of inactivation or control however, the actual mechanisms of microbial inactivation and protein denaturation are usually different when comparing thermal processing to nonthermal processing methods....

Suppression of Outgrowth

The application of effective antibacterial agents to the surface of fresh-cut melons may suppress outgrowth of the native microflora and any human pathogens. Studies showing antilisterial activity of nisin in TSB or PBS62, and demonstrating its activity against native microflora on whole and minimally processed cantaloupe have been reported 17 . However, total elimination of salmonella on the surface of whole or fresh-cut melon could not be achieved, probably due to surface irregularities and...

Conclusions

The many years of difficult and labor-intensive studies on plant-microbe interactions involved in plant symbiosis and disease have begun to yield fundamental molecular information regarding bacterial attachment to plants (Table 2.1). The attachment factors designated in Table 2.1 can be grouped essentially into five categories polysaccharides (EPS, CPS, LPS), outer membrane proteins, flagella, pili, and fimbriae. In some systems, bacterial protein factors have been identified that bind to plant...

Section Ii Microbial Spoilage of Fruits and Vegetables

Beelman Spoilage of Juices and Beverages by Alicyclobacillus spp 159 Interventions to Ensure the Microbial Safety of Sprouts 187 Microbiological Safety of Fresh Citrus and Apple Juices 211 Susanne E. Keller and Arthur J. Miller Microbiological Safety Issues of Fresh 231 Outbreaks Associated with Cyclospora and Cryptosporidium 267 Ynes R. Ortega and Charles R. Sterling 281 Safety of Minimally Processed, Acidified, and Fermented

Vegetable Microflora

Coli Fruit Surface

The microflora on fresh fruits, grains, and vegetables can range from as low as 102 to 109 colony forming units (CFU) per gram 9,10 . On pickling cucumbers, for example, the aerobic microflora is typically between 104 to 106CFU ml for fresh fruit, with LAB less than 101CFU g 11 . In the absence of processing, degradative aerobic spoilage of plant material by mesophylic microorganisms occurs, with Pseudomonas spp., Enterobacter spp., and Erwinia spp. initiating the process 10 . A variety of...

Table

Microbiological Populations of Fresh Agaricus bisporus Mushrooms Treated with Pulsed UV Light at Varying Treatment Times and Distances from the UV Strobe Coliforms 5 x 102 4 x 102 < 1 x 102 < 1 x 102 < 1 x 102 Yeast and mold 1.6 x 104 2.1 x 104 3.4 x 103 1.3 x 103 1.2 x 103 Aerobic plate count 1.6 x 106 4 x 104 1.7 x 105 8 x 104 4 x 104 aerobic populations. Also, increasing treatment time improved reduction in microbial populations. However, all pulsed UV treatments had a negative impact...

Effects of Ozone Gas Treatments on Quality of Fruits and Vegetables

Ozone gas can be used to prevent fungal decay and rot of fruits and vegetables during cold storage 55 . Those products include bananas, citrus fruits, apples, berries, peaches, and potatoes. Ozone can also retard the ripening process of fruit and vegetables by oxidation of ethylene released during storage. Ewell 95 indicated that the shelf life of strawberries, raspberries, and grapes could be doubled when 2 to 3ppm ozone is applied continuously for a few hours per day. Barth et al. 86 reported...

Hydrogen Peroxide

Hydrogen peroxide is a highly effective antimicrobial agent against bacteria but is less active against yeasts, fungi, and viruses 59 . Characteristics and potential food applications of hydrogen peroxide as a sanitizer for produce were recently reviewed by the author 74 . Hydrogen peroxide may be considered as a potential alternative to chlorine. Numerous studies have demonstrated the efficacy of dilute hydrogen peroxide in sanitizing fresh produce including mushrooms 75-77 , apples 16,67,78 ,...

Mode of Microbial Attachment to Melons

The external surface of cantaloupe melons is characterized by the presence of a net comprising porous lenticellar tissue on the epidermis 14 . Such tissue provides numerous attachment sites for microorganisms and also may shield attached cells from contact with cleaning or antimicrobial agents (Figure 10.1). Microbial attachment and the possibility of internalization may occur in the stem scar region. In contrast, honeydew melon and watermelon have a smooth surface that should be less favorable...

Us World Market And Testing Trends 19992008

There is no question that many microbiological tests are being conducted nationally and internationally on food, pharmaceutical products, environmental samples, and water. The most popular tests are total viable cell count, coliform E. coli count, and yeast and mold counts. A large number of tests are also performed on pathogens such as salmonella, listeria and Listeria mono-cytogenes, E. coli O157 H7, Staphylococcus aureus, campylobacter, and other organisms. Applied microbiologists working in...

Potential Applications of Ozone in the Food Industry

Ozone is a strong antimicrobial agent in both gaseous and aqueous phases. It is well known that ozone is an effective disinfectant in water and waste-water treatments 55 . Ozone is 1.5 times more effective as an antimicrobial agent than chlorine. Additionally, ozone is much more effective for a wider spectrum of microorganisms than chlorine and other disinfectants 56 . It reacts up to 3000 times faster than chlorine with organic materials and produces no harmful decomposition products 57 ....

Alpf Medical Research - Mushroom

Anonymous, Classification of fungi, The online msn-Encarta Encyclopedia, retrieved from http encarta.msn.com. 2. Mau, J.-L., Miklus, M.B., and Beelman, R.B., The shelf life of Agaricus mushrooms, in Shelf Life Studies of Foods and Beverages Chemical, Biological, Physical and Nutritional Aspects, Charalambous, G., Ed., Elsevier Science, 1993, pp. 255-288. 3. Chang, S.T., World production of edible and medicinal mushrooms in 1997 with emphasis on Lentinus edodes (Berk.) Sing. in China., Int. J....

Structures That Enable Internalization

Naturally occurring surface apertures and wounds are keys to the internalization of microbes. Two apertures, stomata and lenticels, function in gas exchange, whereas hydathodes provide relief of excessive internal water pressures. Stomata occur in the epidermis of all above-ground parts of plants. Specialized stomata function as nectaries (secrete nectar) in certain types of flowers 1 . Stomata are apertures in the plant's epidermis that are created by two specialized cells called guard cells....

Active Packaging Antimicrobial Films 19321 Synthetic Polymer Films

Antimicrobial packaging is an active packaging strategy that can serve a variety of distinct barrier functions in MAP systems, such as package self-sterilization, sterilization of produce, or reduction of growth of spoilage organisms and or pathogens on packaged produce. Synthetic polymer films are most commonly researched for this functionality. Antimicrobial packaging films can be grouped into two general categories, nonmigratory and migratory. Nonmigratory packaging incorporates...

Advances In Miniaturization And Diagnostic Kits

Identification of microorganisms constituting normal flora, spoilage organisms, foodborne pathogens, starter cultures, etc., in food microbiology is an important part of microbiological manipulations. Conventional methods, dating back more than 100 years, utilize large volumes of medium (10 ml or more) to test for a particular characteristic of a bacterium (e.g., lactose broth for lactose fermentation by Escherichia coli). Inoculating a test culture into these individual tubes one at a time is...

Spoilage Of Fresh Mushrooms

Quality is the single most important factor affecting retail mushroom sales 21 . Whiteness, cleanliness, and brown blotches on fresh mushrooms are the principal factors determining mushroom quality. Consumers prefer to purchase mushrooms that are bright white, free of casing material or other unwanted particulate contaminants clinging to the mushroom surface, and free of brown blotches. The brown blotch discoloration of mushrooms is perceived as a symptom of decreased freshness or...

Alicyclobacillus On Bat Agar

Aliciclobacillus

7.2 Taxonomic 7.3 Physiological and Phenotypic 7.3.2 Thermoacidophilic Growth 164 7.3.3 Alicyclic Fatty Acids in Membrane 165 7.4 Thermal Resistance 7.4.2 Factors Affecting Thermal Resistance 166 7.5 Industrial 7.5.1 Emergence as Spoilage Organisms 172 173 175 177 7.7 Significance of Detection Isolation from Foods 179 7.8 Future The versatility and diversity of the microbial world often lead to unique and valuable discoveries that expand our knowledge and yield advancements for humankind....

Natural Occurrence Of P expansum And Patulin In Fruits And Vegetables

Penicillium expansum is one of the most pervasive and destructive postharvest pathogens of pome fruits such as apples and pears, but it can affect other fruits including tomatoes, strawberries, avocados, bananas, mangoes, grapes, peaches, and apricots 3,68 . The primary habitat of P. expansum is in fruit storage and packinghouse facilities, but it can also be found in orchard soil, seeds of various plants, and on the surface and in the core of unblemished fruit. The fungus is primarily a wound...

Selection of Test Strains for Sanitizer Efficacy and Challenge Studies

The strain or strains of a particular microorganism selected for studies designed to determine the efficacy of a decontamination treatment or survival and growth in challenge studies are extremely important. The use of well-characterized reference strains enhances the comparative assessment of a given method among laboratories. Five or more strains, preferably recently isolated from produce or other plant materials, and from patients suffering from illness associated with consumption of a raw...

Interventions Seeds 831 Chemical and Physical

Sanitizing sprout seed presents a unique challenge in the arena of produce safety in that even a low residual pathogen population remaining on contaminated seed after treatment appears capable of growing to very high levels up to 8 log10 CFU g due to favorable conditions of moisture, relative humidity, temperature, and nutrient availability during seed germination and subsequent sprout growth 51,52 . In addition, after a sanitizing procedure seed germination as well as sprout yield and quality...

Basic Anatomy And Biochemistry Of Roots And Leaves

Epiphytic Bacteria

The rhizoplane is the area of the root interfacing with soil. Root tips and root hairs are immersed in mucigel, a substance created by the combination of plant-secreted mucilage composed of pectins and hemicelluloses and complex polysaccharides produced by bacteria that also degrade mucilage 23 . Bacteria are exposed to the mucilage when the cuticle covering it on root hairs is punctured or degraded physically or chemically. Depending on the plant, root exudates contain a variety of substances...

Listeria monocytogenes

Although not implicated in a foodborne outbreak associated with fresh juices, other foodborne pathogens do exist that also exhibit a tolerance resistance to high levels of acid. Given an opportunity to contaminate fresh juice, these acid-resistant organisms could result in foodborne outbreaks. Chief among these possible pathogens is Listeria monocytogenes. L. monocytogenes is ubiquitous within the environment, carried by animals, and frequently found on fruits and vegetables 57-59 . The minimum...

Contents

6.1.2 Commercial Growing Practices 136 6.2 Microbiology of Fresh 6.3 Spoilage of Fresh 6.3.1 Sources of Microorganisms Causing Spoilage 142 6.3.2 Cultural Growing Practices Favoring Spoilage 142 6.3.3 Cultural Practices to Suppress Spoilage of 6.3.4 Postharvest Conditions Favoring Spoilage of 6.3.5 Postharvest Practices to Suppress Spoilage of 148 150 6.3.5.4 Pulsed Ultraviolet Light Treatment 151 6.1 FRESH MUSHROOMS 6.1.1 Introduction Based on phylum classification, fungi are classified as...

D

FIGURE 8.2 Scanning electron micrograph of alfalfa seeds showing extensive cracking of a seed coat and natural openings C, crack in the seed coat H, hilum M, micropyle. FIGURE 8.2 Scanning electron micrograph of alfalfa seeds showing extensive cracking of a seed coat and natural openings C, crack in the seed coat H, hilum M, micropyle. MN , Tween 80, Vegi-cleanTM Microcide, Inc., Detroit, MI , and Vortex Ecolab . Treating with aqueous chemicals at elevated temperatures can lead to greater...