Sources of Microorganisms PDF

‫بسم اهلل الرمحن الرحيم‬ ‫‪In the name of Allah‬‬ ‫‪1‬‬  Sources of Microorganisms By Prof. Dr./ Mohamed Abdel-Shafi Abdel-Samie Course name Food Microbiology 2  Contents Plants Animals, Birds, Fish, and Shellfish...

‫بسم اهلل الرمحن الرحيم‬ ‫‪In the name of Allah‬‬ ‫‪1‬‬  Sources of Microorganisms By Prof. Dr./ Mohamed Abdel-Shafi Abdel-Samie Course name Food Microbiology 2  Contents Plants Animals, Birds, Fish, and Shellfish Other Air Soil Sources Sewage Water Human Food Ingredients 3 Introduction 4  Introduction The internal tissues of healthy plants (fruits and vegetables) and animals (meat) are essentially sterile Yet raw and processed (except sterile) foods contain different types of molds, yeasts, bacteria, and viruses.  Introduction. Cont….. Microorganisms get into foods from: Natural sources (including internal) External sources: to which a food comes into contact from the time of production until the time of consumption. 6  Natural sources of contamination Natural sources for foods of plant origin include : surfaces of fruits, vegetables, and grains pores in some tubers (e.g., radish and onion) 7  Natural sources of contamination Natural sources for foods of animal origin include: skin hair feathers gastrointestinal tract urinogenital tract respiratory tract milk ducts (teat canal) in udders of milk animals 8  Microflora as a contaminant Natural microflora exist in ecological balance with their hosts, and their types and levels vary greatly with: type of plants and animals Their geographical locations and environmental conditions 9  Extrernal contaminant Besides natural microorganisms, a food can be contaminated with different types of microorganisms coming from outside sources such as: air, soil, sewage, water, feeds, humans, food ingredients, equipment, packages, and insects. 10  Level of contamination Microbial types and their levels from these sources getting into foods vary widely and depend on the degree of sanitation used during the handling of foods. 11 Plants (Fruits and Vegetables) as a source of food contamination 12  Plant as a source of contaminants The inside tissue of foods from plant sources are essentially sterile except for a few porous vegetables (e.g., radishes and onions) and leafy vegetables (e.g., cabbage and Brussels sprouts). 13  Plant as a source of contaminants The inside tissue of foods from plant sources are essentially sterile except for a few porous vegetables (e.g., radishes and onions) and leafy vegetables (e.g., cabbage and Brussels sprouts). Some plants produce natural antimicrobial metabolites that can limit the presence of microorganisms. 14 Plant as a source of contaminants Fruits and vegetables harbor microorganisms on the surface their type and level vary with: soil condition type of fertilizers water used air quality 15  Plant as a source of contaminants Contaminant expected from plant source include: Molds, yeasts, lactic acid bacteria, and bacteria from genera Pseudomonas, Alcaligenes, Micrococcus, Erwinia, Bacillus, Clostridium, and Enterobacter Pathogens, especially of enteric types, can be present if the soil is contaminated with untreated sewage.  Factors increases contamination levels from plant sources Diseases of the plants, damage of the surface (before, during, and after harvest), long delay between harvesting and washing, and unfavorable storage and transport conditions after harvesting and before processing Improper storage conditions following processing can also increase their numbers.  Animals, Birds, Fish, and Shellfish 18  Animals and birds Animals and birds normally carry many types of indigenous microorganisms in the: digestive, respiratory, and urinogenital tracts, the teat canal in the udder, as well as in the skin, hooves, hair, and feathers. Their numbers, depending on the specific organ, can be very high (large intestinal contents can have as high as 1010 bacteria/g).  Sources of M.O in animal and birds In normal conditions, animals, as carriers, can harbor pathogens such as: Salmonella serovars pathogenic E. coli Campylobacter jejuni Yersinia enterocolitica Listeria monocytogenes and without showing symptoms.  Sources of M.O in animals and birds Disease situations, such as mastitis in cows and intestinal, respiratory, and uterine infections, as well as injury can change the ecology of normal microflora. Similarly, poor husbandry resulting in fecal contamination on the body surface (skin, hair, feathers, and udder) and supplying contaminated water and feed (e.g., contaminated with salmonellae) can also change their normal microbial flora.  Sources of M.O in Fish Fish and shellfish also carry normal microflora in the scales, skin, and digestive tracts. Water quality, feeding habits, and diseases can change the normal microbial types and level. Pathogens such as Vibrio parahaemolyticus, Vib. vulnificus, and Vib. cholerae are of major concern from these sources.  Contamination of food of animal sources Many spoilage and pathogenic microorganisms can get into foods of animal origin (milk, egg, meat, and fishery products) during production and processing.  Contamination of food of animal sources Milk can be contaminated with fecal materials on the udder surface, egg shells with fecal material during laying Meat can be contaminated with the intestinal contents during slaughtering Fish can be contaminated with intestinal contents during processing.  Contamination of food of meat In addition to enteric pathogens from fecal materials, meat from food animals and birds can be contaminated with several spoilage and pathogenic microorganisms from skin, hair, and feathers, namely Staphylococcus aureus, Micrococcus spp., Propionibacterium spp., Corynebacterium spp., and molds and yeasts.  Prevention of Contamination in meat Prevention of food contamination from these sources needs the use of effective husbandry of live animals and birds, which includes good housing and supply of uncontaminated feed and water. Also, testing animals and birds for pathogens and culling the carriers are important in reducing the incidence of pathogenic microorganisms in foods.  Ways to Prevent Contamination in meat Cleansing using good-quality water for washing carcasses (preferably with acceptable antimicrobial agents); hair removal; feather removal; careful removal of digestive, urinogenital, and respiratory organs without contaminating tissues removal of contaminated parts; and proper sanitation during the entire processing stage are necessary during slaughter to keep microbial quantity and quality at desirable levels.  Ways to Prevent Contamination in milk and eggs Proper cleaning of the udder before milking, cooling milk immediately after milking, processing as soon as possible, and sanitization at all stages are important to keep microbial levels low in milk. Eggs should be collected soon after laying and washed and stored as per recommended procedures.  Ways to Prevent Contamination in food of Fish Fish and marine products should be harvested from unpolluted and recommended water. Proper sanitation should be used during processing. They should be stored properly to prevent further contamination and microbial growth. Ice to be used for storage should be produced from potable water.  Air as a source of food contamination 30  Air as a source of food contamination Filamentous fungi are capable of growing on many different foods, such as grains, meats, milk, fruits, vegetables, seeds, and high-fat products. They are an important group of food spoilage organisms and cause significant economic losses in agriculture and the food industry. 31  Filamentous fungi spoilage of foods These obligate aerobic microorganisms are capable of growing in wide ranges of pH, temperature, and water activity and of using a great variety of substrates as food. Filamentous fungi grow more commonly in products with low pH and water activity. 32 Filamentous fungi spoilage of foods They are located mainly on the surface of the food because of their dependence on oxygen. The main food spoilage fungi are Penicillium, Aspergillus, Rhizopus, Mucor, Geotrichum, Fusarium, Alternaria, Cladosporium, Eurotium, and Byssochlamys. 33  Filamentous fungi spoilage of foods Some of these species are also known for their ability to synthesize secondary toxic metabolites called mycotoxins, constituting a problem for agribusiness and the food industry. 34  Controlling Microbiological spoilage of food  Controlling Microbiological Spoilage of Foods Avoiding or retarding spoilage of raw and processed foods but at the same time preserving the sensory and nutritional characteristics of foods is a great challenge for the industry. The methods used for controlling microbial spoilage include preventing access of the organisms to the foods, removing their cells or spores, inhibiting their growth, and using thermal and nonthermal methods to inactivate them.  Controlling Microbiological Spoilage of Foods The good manufacturing and handling practices are very important means of reducing the baseline microbial load and increasing shelf life. They are considered the minimum hygienic requirements for the production of any type of food. These practices should be used throughout the entire food production chain, from production of raw materials to con- sumer consumption.  Controlling Microbiological Spoilage of Foods Other methods of preventing spoilage include: (1) washing the raw materials before processing, which removes microbial cells from its surface (2) centrifuging (3) using membrane filtration processes, which can only be used on certain food groups.  Controlling Microbiological Spoilage of Foods foods can also be preserved by manipulating factors that not only influence microorganism growth and survival but are also safe for consumers. Control of microbial growth by changing intrinsic and extrinsic factors, also called barrier theory, is the main way of reducing food spoilage. Controlling Microbiological Spoilage of Foods The most important barriers used for food preservation are : temperature (high and low) low aw acidity (pH) redox potential (Eh) preservatives microbial competition These microbial control methods use changes in food characteristics and storage conditions to prevent or reduce microbial growth. Controlling Microbiological Spoilage of Foods Combining different sublethal conditions to prevent microbial growth is a successful approach mainly because it does not change the sensory characteristics of the foods significantly. The great disadvantage of these methods is that microorganisms can resume growth if favorable growth conditions occur. Controlling Microbiological Spoilage of Foods Some food preservation methods focus on microbial inactivation. They can be classified as thermal or nonthermal methods of food preservation. Thermal Non-Thermal Treatments Treatments Controlling Microbiological Spoilage of Foods Thermal methods Such as pasteurization and commercial sterilization, are widely used to efficiently inactivate pathogens and reduce the load of spoilage microorganisms. Despite this, they can also change the nutritional and sensory properties of the food. Controlling Microbiological Spoilage of Foods Non-Thermal methods To replace these methods and meet the increasing consumer demand for healthier products, many nonthermal methods are being developed and used. The main nonthermal methods are radiation, high hydrostatic pressure, pulsed electric field, and ultrasound. Controlling Microbiological Spoilage of Foods Non-Thermal methods Many of these methods are still difficult to implement because of equipment cost, need of trained personnel, and consumer distrust. Inquiries 46  End Thanks for your cooperation 47