Downloaded 68 times
Uploaded byRanjani thirumalai
Micro organisms in foods
Microorganisms play important roles in food as pathogens that can cause disease, as spoilage organisms that degrade food quality, and as cultured microbes used in food processing. Fruits and vegetables naturally contain saprophytic bacteria and fungi that can lead to spoilage when the protective barriers are broken during harvesting or processing. The major factors affecting microbial growth in fruits and vegetables include physical damage, pH, moisture content, and temperature. Common preservation methods include drying, freezing, acidification, and use of preservatives.
Food◦
More Related Content
Similar to Micro organisms in foods
Micro organisms in foods
- 1.
- 2. INTRODUCTION Microorganism In Foods Micro-organisms,in relation to food, can have one of these 3 roles: • Pathogenic micro-organisms can cause infections or intoxications • Saprophytic micro-organism play a role in biodegradation and cause food spoilage • Cultured micro-organisms like probiotic bacteria are used in food processing.
- 3. Basic Food BornePathogens • Listeria monocytogenes • Salmonella poona • Shigella spp. • S. aureus
- 4.
- 5. INTRODUCTION • Fruits andvegetables are rich source of energy, body-building nutrients, vitamins and minerals. • Protected mechanically by the pectins which constitute a protective gum between the cell sand gives firmness. • Spoilage in fruits and vegetable starts with the hydrolysis of the pectin. Once the pectinases have damage the structure of the fruit / vegetable, other organisms start to contribute to the soft rot. • Majority of the microorganisms in vegetables are saprophytes, such as lactic acid bacteria, coryniforms, coliforms, micrococci, spore-formers, and pseudomonas, which may be from the air, soil, and water. • The fungus namely Aureobasidium, Fusarium, and Alternaria, are also commonly present but lower in number as compare to bacteria.
- 6. BASIC TYPES OFSPOILAGE On the basis of appearance: • Microbial growth • Change in food colour Textural change • Slime formation • Tissue softening Changes in taste and odour • Development of nitrogenous compounds • Organic acids • Sulfides
- 7. FACTORS AFFECTING MICROBIAL GROWTH InFruits :- • Physical damage during harvesting causes breaks in outer protective layers of fruits that spoilage organisms can exploit. • High levels of sugar and a low pH in fruits juices generally favours growth of yeasts, moulds and acid-tolerant bacteria. In Vegetables :- • Bacterial spoilage start with softening of tissues as pectins are degraded and the whole vegetable finally become slimy mass. • The higher moisture content of vegetables as compared to grains allows different fungi to proliferate, but some species of Aspergillus attack onions
- 8. PRESERVATION METHODS Use ofAcidultants • Lactic acid • Acetic Acid Other Acidulants • Scalding or blanching in hot water • Drying fruits and vegetables • Natural sun drying Drying with a food dehydrator • Oven drying • Pasteurizing sun dried fruits • Conditioning dried fruits • Freezing • Use of ozone
- 9. CAUSATIVE MICROBES Saprophytic microorganisms P.fluorescens E. agglomerans E. herbicola Yeast and molds • Basidiophora • Peronospora • Phytophthora • Plasmopara Saprophytic microorganisms P. fluorosceces E. agglomerans E. herbicola Saprophytic microorganisms • P. fluorescens • E. agglomerans • E. herbicola
- 10.
- 11. Fruit Juices • Fruitjuices are commonly contaminated with yeasts and moulds, often from insect damage. • Fallen fruit should thus be avoided where possible, for all of the risks outlined below. • Sugars and sugar concentrates are commonly contaminated with osmophilic yeasts, for example Z.Rouxii. • Growth is slow in concentrated solutions, but one cell per container of diluted stock is enough to cause spoilage (davenport, 1996). Flavourings, water and other chemicals are all potential sources of microbial contamination. • Process machinery and filling lines are particularly problematic and strict hygiene is essential.
- 12. Pickles • Pickling, alsoknown as brining or corning is the process of preserving food by anaerobic fermentation in brine (a solution of salt in water) to produce lactic acid, or marinating and storing it in an acid solution, usually vinegar (acetic acid). • The resulting food is called a pickle. This procedure gives the food a salty or sour taste. In South Asia, edible oils are used as the pickling medium with vinegar. Another distinguishing characteristic is a pH less than 4.6, which is sufficient to kill most bacteria.
- 13. • Pickling canpreserve perishable foods for months. Antimicrobial herbs and spices, such as mustard seed, garlic, cinnamon or cloves, are often added. • If the food contains sufficient moisture, a pickling brine may be produced simply by adding dry salt. • Natural fermentation at room temperature, by lactic acid bacteria, produces the required acidity. Other pickles are made by placing vegetables in vinegar. • Unlike the canning process, pickling (which includes fermentation) does not require thatthe food be completely sterile before it is sealed.
- 14.
- 15. INTRODUCTION • Raw meatin general contains bacteria, including pathogenic and spoilage ones. • As warm blooded animals naturally carry bacteria such as salmonella spp. • Raw meat may be contaminated with bacteria during the slaughtering process such as evisceration and dressing procedures.
- 16. Microorganism In Meat •Raw meat may contain bacteria such as E.coli, Salmonella & Listeria. • Thorough cooking these harmful microbes but meat can become contaminated again if it is not handled and stored properly.
- 17. Main cause ofmeat spoilage • Three factor contribute to microbial growth Heat is the foremost concern. Microbes grow rapidly in a carcoss, if it allowed to stay warm. Meat begins spoil above 40F. The most common microorganism involved in spoilage are Psedomonas spp, Enterobacteriaceaae family, lactic acid bacteria
- 18. Prevention Of SpoilageBy Microbes • Remove expired or spoiled. • Store it in right place in fridge. • Prevent mold growth in the fridge. • Prefer freezer burn. • Set foods on the counter or in the pantry. • Separate some foods to prevent spoilage.
- 19. Spoilage Types Of Spoilage: Microbial spoilage Non – Microbiaol spoilage Condition For Spoilage Water pH Physical Structure Oxygen Temperature
- 20.
- 21. INTRODUCTION • Poultry canbe defined as domestic fowls, including chickens, turkeys, geese and ducks, raised for the production of meat or eggs and the word is also used for the flesh of these birds used as food.
- 22. Microorganism In Poultry •The principal spoilage bacteria found on poultry include Pseudomonas, Staphylococcus, Micrococcus, Acinetobacter, and Moraxella. • In addition, poultry often supports the growth of certain pathogenic(disease-causing) bacteria, such as Salmonella.
- 23. Spoilage Of Poultry •Most of microbes grow on the surface of skin lining of body cavity and any cut surface. • Enzymes of the fowl contributes to the deterioration of dressed birds. • Microbes is the chief cause of spoilage and intestion is the primary source
- 24. Contamination Of PoultryFood • Some of the microbial contaminants can grow or survive during food processing and storage. • Contamination of the skin and the lining of the body cavity occurs during washing, plucking, and evisceration. • The process of sticking and bleeding can also introduce contamination.
- 25. Use Of Preservatives •Poultry are soaked up in organic acids (acetic, adipic, succinic) at pH 2.5 helps lengthen shelf life • Some fowl, like Turkey, are cured in a solution of salt, sugar, and sodium nitrate for several weeks at about 3.3𝑜C
- 26. Spoilage of Poultry •Most bacterial growth takes place on the surfaces (skin, lining of the body cavity, and any cut surfaces). • Enzymes of the fowl contributes to the deteriorationof dressed birds. • Bacteria is the chief cause of spoilage and the intestines is the primary source.
- 27. Signs Of Spoilage •There is an off odour. • Change in colour. • Feels sticky, slimy or tacky to touch.
- 28.
- 29. INTRODUCTION • Fish isone of the most perishable food products, and therefore, quality deterioration of fresh fish occurs rapidly during handling and storage and limits the shelf life of the product . • Many pathogenic and spoilage bacteria are able to attach on food contact surfaces, and remain viable even after cleaning and disinfection
- 30. Microbial Quality ofFish and Fish Products • Humans and microbes have a long history together. • The normal microbial flora consists of organisms that make their home on or in some part of the body. In a healthy person, such organisms rarely cause disease. • Microorganisms of the normal flora may be in symbiotic relationship, where both microorganism and host benefit. • The enteric bacteria that form the normal flora of the intestine assist in the synthesis of vitamin K and some of the vitamins of the B complex. • In commensalism, microorganisms are neither beneficial nor harmful to their host as in the case of the large group of microbial flora that live on the skin, and the mucous membranes of the upper respiratory tract, intestines and vagina. • Fish is very important foodstuff in developing countries due to its high protein content, and nutritional value.
- 31. Fish Spoilage • Fishspoilage is a complex process, in which physical, chemical and microbiological mechanisms are implicated.Many spoilage producing bacteria (Aeromonas, Alcaligenes, Bacillus, Enterobacter, Enterococcus, Escherichia coli, Listeria, Pseudomonas, Shewanella) and fungi (Aspergillus, Candida, Cryptococcus, Rhodotorula) are isolated from fresh and spoiled fish and other sea foods. • Microbiological Spoilag Live fish is normally considered to be sterile, but microorganisms are found in varying numbers on all the outer surfaces (skin and gills) and in the alimentary tract of live and newly caught fish.