The scope of food microbiology includes studying microorganisms in water and on plants. Water sources like rivers and lakes harbor a diverse array of microorganisms, some of which can impact food safety. Fungi in water can produce toxic metabolites affecting shellfish. Similarly, plants host specialized microbial floras on their surfaces, playing roles in nutrient cycling and spoilage prevention. However, certain bacteria and fungi can lead to storage issues and diseases in plant products. Understanding these microorganisms is crucial for ensuring food safety.
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Micro-organisns of water In warmer seas, unpolluted water may contain Vibrio parahaemolyticus, which may cause food poisoning outbreaks. Fresh waters of rivers and lakes have a complex flora of microorganisms, including aquatic species and components from terrestrial, animal, and plant sources. Fresh water may also act as a vehicle for bacteria, protozoa, and viruses causing disease through contamination with sewage effluent containing human fecal material. Indicator organisms, such as Escherichia coli, are used to infer the presence of these organisms.
Micro-organisms of water Fungi, including cyanobacteria and dinoflagellates, can impact food quality and safety by producing toxic metabolites that can become concentrated in shellfish without causing harm.
Micro-organisms of plant Plant surfaces have a specialized phylloplane flora for leaf surfaces and rhizoplane flora for roots surfaces. Healthy leaves may have low numbers of organisms, but species are well-adapted. Moulds like Cladosporium and black yeast Aureobasidium pullulans are common, covering leaf surfaces with black sooty deposits. Aureobasidium behaves like yeast in laboratory culture but develops into filamentous mould-like organisms.
Micro-organisms of plant Mirror yeasts and bacterial flora are found in plants, including flowers, fruits, and grapes. Mirror yeasts produce spores that germinate on a Petri dish containing malt extract agar, forming a mirror image of the leaf. The bacterial flora on aerial plant surfaces is predominantly Gram-negative, but also includes fermentative Gram-positive bacteria like Lactobacillus and Leuconostoc. These specialized moulds, yeasts, and bacteria are harmless on healthy plant surfaces, preventing spoilage after harvest.
Micro-organisns of plant As plants mature, bacterial and fungal floras change, with increased numbers of pectinolytic bacteria and mould species colonizing senescent plant material. These organisms help break down complex plant materials, returning carbon, nitrogen, and other nutrients for plant growth. However, humans harvesting plant products can cause spoilage problems during storage and transport. Some species of fungi and bacteria can overcome resistance and cause disease, such as the potato plant's blackleg disease, which can cause severe soft rot during storage.
Micro-organisms of plant Cereals undergo significant changes in microbial flora after harvesting. Field fungi, including Cladosporium, Alternaria, Helminthosporium, and Chaetomium, infect senescent plant structures carrying cereal grain. After harvesting, these components decrease and are replaced by storage fungi, including Penicillium and Aspergillus. Fusarium contains a spectrum of species, including specialized plant pathogens and saprophytic field fungi. Aspergillus flavus, a carcinogenic fungus, may infect growing plants in the field before harvesting and storage.
Micro-organisms of ainmal origin Healthy animals have a complex microbial flora, specialized for growth and survival, and transient for immediate interactions with the environment. The gut, a topological surface, offers a specialized environment. The Skin Human and animal surfaces are exposed to air, soil, and water, posing a risk of contamination in food and food handling equipment. Skin surfaces are unfavorable for microorganisms due to their dryness and low pH. However, hair follicles, sebaceous glands, and skin surface have specialized flora adapted to each environment. In humans, the normal skin flora is dominated by Gram-positive bacteria. Foulage organisms can be found in meat-killed animals, while feathers and exposed follicles can affect carcass microbial quality.
The Nose and Throat The nose and throat, with mucous membranes, are specialized environments inhabited by microorganisms that can cause disease, especially during extremes of temperature,starvation, or overcrowding. Staphylococcus aureus, a significant human strain, can produce a powerful toxin causing vomiting.
