ISOLATION OF MICROBES (BACTERIA AND FUNGI) FROM SPOILED FRUITS AND VEGTABLES
AIM:
To isolate kind of microorganism present in spoiled fruits and vegetables
PRINCIPLES:
Fruits and vegetables provide sufficient condition for the growth of several fungi and bacteria Microorganisms spoil the fruits and vegetables and changes the texture and makes them uneatable. There is a heavy loss of fruits and vegetables due to spoilage by microorganisms; how ever during handling and transportation also, there is a greater risk to get damaged. thus farmers suffered a great loss due to spoilage. Spoilage refers to any change in the condition of food in which the food becomes undesirable or unacceptable for human consumption. Bacterial spoilage first causes softening of tissues as pectins are degraded and the whole fruit may eventually degenerate into a slimy mass. Starch and sugars are metabolized next and unpleasant odours and flavours develop along with lactic acid and ethanol. Some spoilage microbes are capable of colonizing and creating lesions on healthy, undamaged plant tissue Present investigation was carried out to study the presence of various bacteria responsible for the post harvest decay and deterioration of economically important fruits.
Possible organism
Vegetables :
Bacteria - Pseudomonas sp., Alkaligens sp., Erwinia sp., Xanthomas sp., Micrococcus sp., Coryneforms, Bacillus sp., and other Enterobaceriaceae members
Fungi- Fusarium., Alternaria, Aerobasidium, penicillium, Rhizopus
Fruits :
Bacteria - Pseudomonas sp., Alkaligens sp., Erwinia sp., Xanthomas sp., Micrococcus sp., Bacillus sp.,
Fungi- Fusarium., Alternaria, Aerobasidium, penicillium, Rhizopus., Cladisporium., Trichoderma etc
MATERIALS REQUIRED:
- Sample: spoiled vegetables, fruits or its byproducts
- Media- Nutrient agar, SDA agar, SS agar, Mannitol salt agar (MSA), EMB agar, TCBS Agar, rose Bengal chloramphenicol agar
- Others- water/saline blank, test tubes, petriplates, conical flask, etc
- Preparation of sample
Weigh 1g of sample and blend with 1ml of distilled water and serially dilute
- Isolation on basal media
Streak a loopfull of culture into Nutrient agar and SDA plate Incubate Nutrient agar plate at 37°c for 24 hrs and SDA plate at 28°c for 48 hours
- Coliforms isolation
Streak a loopful of culture into EMB Agar plates and incubate at 37°c for 24 hrs
- Isolation of S. aureus
Streak a loopful of culture into MSA agar plate and incubate at 37°c for 24 hrs
- Isolation of vibrio
Streak a loopful of culture into TCBS Agar plate and incubate at 37°c for 24 hrs
- Isolation of Salmonella and Shigella
Streak a loopful of culture into SS agar plate and incubate at 37°c for 24 hrs
- Isolation of yeast and mold
Inoculate a loopful of culture into Rose Bengal chloramphenicol plate and incubate at 28°c for 48 hrs.
RESULT:
The microorganisms (bacteria and fungi) present in spoiled fruit and vegetables were isolated.
MEDIA OBSERVATION
- Nutrient agar -White, circular, golden yellow colonies
- SDA - Presence of both creamy to white(yeast)&filamentous(mold)colonies
- EMB -Presence of both pink and green metallic sheen colonies
- MacConkey agar -Presence of both lactose (pink colonies) and non lactose (colourless colonies)
- SS agar -Smooth, opaque and black centered colonies
- Cetrimide agar -Blue green colour colonies
- TCBS agar Yellow colour colonies due to sucrose fermentation
- Rose bengal chloramphenical agar Powdery white colonies
Microorganisms present on the surface of freshly harvested fruits and vegetables includes not only those of normal surface flora but also those from soil, water, perhaps plant pathogens. Vegetables and fruits may be Dried, frozen, fermented, pasteurized and canned. Generaly fruits and vegetables have low number of microbes. During transportation and processing mechanical damage may increased contamination. Pre cooling of the product and refrigeration during transport may reduce the growth of contaminated microorganism. Possible source of contamination trays, tanks, tables, aprons and filters
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