Microbial development is aided by foods of both plant and animal origin. Microorganisms’ capacity to grow or proliferate in such food is determined by the food environment.
Microbial proliferation is influenced by intrinsic, extrinsic, and implicit dietary components, as well as diverse food processing processes. And what is one factor that affects the growth of bacteria in food
Molds and yeasts, on the other hand, can thrive at lower pH than bacteria, while Gram-negative bacteria are more susceptible to low pH than Gram-positive bacteria.
Molds thrive best in a pH range of 1.5 to 9.0, yeasts in 2.0 to 8.5, Gram-positive bacteria in 4.0 to 8.5, and Gram-negative bacteria in 4.5 to 9.0. Microorganisms may be classified into the following groups based on their pH ranges:
Neutrophiles thrive best when the pH is between 5 and 8.
Acidophiles thrive in environments with a pH below 5.5.
At a pH of over 8.5, alkaliphiles thrive.
The quantity of water accessible for biological processes that may be lowered by an osmotic action is known as water activity (aw). Water is made accessible in meals in a variety of ways, including
Water in the solution is bound by solutes and ions.
Colloids that are hydrophilic
The crystallization or hydration water
To develop in the food, microorganisms need water in a readily accessible form. The ratio of the food’s water vapor pressure to that of pure water at the same temperature may be used to calculate food’s water activity. Because no meal may have a water activity of 0 or 1, it ranges from >0 to 1.
In comparison to fungus, bacteria need more water activity for growth. Bacteria cannot grow below a pH of 0.91, but molds may thrive to a pH of 0.80.Gram-negative bacteria are more susceptible than gram-positive bacteria to low water activity. Microorganisms are classified according to their water activity range.
The ability to grow in the presence of high salt concentrations is referred to as halotolerant. Osmotolerant plants that can thrive in high concentrations of unionized organic molecules like sugars. Aerotolerant and capable of growing on dry meals.
A substance’s oxidation-reduction or redox potential is defined as a measurement of electron transfer between atoms or molecules. Eh is the standard abbreviation for the oxidation-reduction potential, which is measured in millivolts (mV). Food’s redox potential is determined by the the food’s pH
Oxygen availability (physical state, packaging)
Poising capacity, often known as buffering capacity, is a term used to describe the ability to
Composition of food (such as protein, ascorbic acid, reducing sugars)
The Eh ranges at which certain microorganism families may thrive are as follows:
Molds, yeasts, Bacillus, Pseudomonas, Moraxella, and Micrococcus may all grow best from +500 to +300 mV.
Lactic acid bacteria and members of the Enterobacteriaceae family are facultative anaerobes that thrive best at +300 to +100 mV.
Clostridium spp., for example, may grow best from +100 to –250 mV or below.
Proteins, carbohydrates, sulfur, phosphorus, vitamin, lipids, water, energy, nitrogen, and minerals are all required for bacteria to develop and carry out metabolic processes. For microbial development, food is the finest source of nutrients.
Microorganisms typically found in food have a wide range of nutritional needs, and those that can use available nutrition in large quantities prevail in meals. The most basic forms of carbohydrates and amino acids are used first, followed by the simpler forms.
Gram-positive bacteria have greater nutritional needs than yeasts, followed by Gram-negative bacteria. Molds demand the least amount of nutrients.
Antimicrobial components in many foods protect against the microbial assault of numerous foodborne illnesses.
Antimicrobial components may be found in plant and animal products.
Microbial invasion is prevented by the biological structure of certain foods. The natural coating protects the food from harm and helps to prevent microbial deterioration.
Foodborne infections and spoilage microorganisms are prevented by structures such as the outer coatings of fruits, the shells of nuts, and the shells of eggs, meat has fascia, and skin.
The temperature of the environment has an impact on enzyme processes and microbiological development. The temperatures at which yeasts and molds grow span a wide range of 10–35° C. Bacteria may be classified according on their temperature.
Psychrotrophs are cold-tolerant microorganisms that can thrive in temperatures ranging from 0 to 20 degrees Celsius. Pseudomonas spp. and Enterococcus spp. are two examples.
Mesophiles are microorganisms that can thrive at temperatures ranging from 25 to 40 degrees Celsius, with an optimal temperature of about 37 degrees Celsius. Salmonella, Staphylococcus, Clostridium, Shigella, and Bacillus are among them.
Thermophiles are microorganisms that thrive at temperatures over 45 degrees Celsius, with an optimal temperature range of 50 to 70 degrees Celsius. Bacillus, Clostridium, and Geobacillus species are among them.
The quantity of moisture in the atmospheric or food environment is measured by relative humidity.
Relative humidity can affect the level of water activity (aw) on food, and thus the growth of microorganisms.
Dry grains, for example, will absorb water and get moldy if kept in a high-humidity environment.
Gases including carbon dioxide (CO2), ozone (O3), and oxygen (O2) have a direct harmful impact on cells, preventing them from growing and reproducing.
Anaerobic bacteria are highly toxic to ozone (O3) and oxygen (O2), while obligate aerobes are resistant to carbon dioxide.
Implicit factors are the third component to consider when assessing the type of microbial proliferation in food.
This element determines the traits of organisms and how they react to different surroundings.
Microorganisms may either impede or boost each other’s growth. Predation, parasitism, commensalism, amensalism, allotropy, asymbiosis, and neutrality are some of the different behaviors and responses that may be destructive or helpful to microorganisms.
Antibiotics, bacteriocins, hydrogen peroxide, and organic acids are examples of compounds that are either inhibiting or fatal to other species.
Microorganisms may be exposed to a variety of physical and chemical stressors during food preparation.
Heat, freezing, drying, osmotic effects, irradiation, and different chemicals are examples of processing variables.
By disrupting the cytoplasmic membrane and altering metabolic and enzymatic activity, heating aids in the reduction of bacteria levels in food.
Freezing inhibits the development of microorganisms by lowering the pH and increasing the Aw.
Drying inhibits microbial development by causing metabolic damage that prevent cells from proliferating.
Raw food items have the potential to contaminate food, kitchen utensils, and surfaces (i.e., meat and poultry). By using the same knife, cutting board, or other instrument repeatedly without wiping the surface or item between usage, microbes may be transmitted from one meal to another.
The greater the temperature, the easier it is for germs to proliferate to a certain degree. Both very high and extremely low temperatures disrupt the enzymatic activities that bacteria rely on to thrive.
Microbial activity may be hampered by moisture in a variety of situations, including saline water, food, wood, biofilms, and soils. By decreasing intracellular water potential and consequently limiting hydration and enzyme activity, low water availability may decrease microbial activity.
In the presence of light, both bacteria strains take in more organic carbon, including sugars, and metabolize them more quickly. These functions are inhibited in the dark, and bacteria accelerate protein synthesis and repair, constructing and repairing the equipment required to grow and divide.
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