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Growth of Microbes
In food, intrinsic and extrinsic parameters
| Term | Definition |
|---|---|
| Botulism | Disease caused by clostridium botulinum, symptoms include difficulty breathing, muscle, and body nerves problems |
| Endogenous population | Natural microflora of food |
| Intrinsic parameters | Physiological properties of food that are inherent part of plant or animal tissues |
| Fungi ph optimum growth | Around ph below 3.5 or wide range of ph |
| Food classification: low acid or non acid | Food ph greater than 5.3 is classified as |
| Medium acid food ph range | Ph 4.6-5.3 |
| Acidic food ph range classification | Ph 1.7-4.6 |
| Highly acidic foods ph range classification | Ph below 3.7 |
| The higher the protein content, | The higher is the buffering capacity |
| Which has high buffering capacity: meat or vegetables | Meat |
| Microorganisms cannot easily change the ph of food with (high or low) buffering capacity | With high buffering capacity |
| Food with ph greater than 7, basic / alkaline foods | Egg (8-9), corn (7.3) , fermented shark (10-11) |
| Foods with ph lower than 7 | Ph 5.5-6.2: Meat, chicken, shrimps; 4.6-5.3: green beans,carrot; 2.4-3.4: pineapple, lemon juice |
| Toxicity of adverese ph (bad effects) | Stops nutrient transport, denature membrane, stops enzyme functions, etc. |
| Water activity | Ratio of water vapor pressure of food substrate to the vapor pressure of pure water at same temperature |
| Moisture content (%) | Amount of bound water and free water in sample, quantitative |
| Water activity measures | Amount of free water in sample, qualitative |
| The closer the water activity to 1, the _____ the stability of food items | Lower |
| Water content percent of meat: pork | 53-60% |
| Water content in percent of chicken | 74% |
| Foods with the highest water content 90-95% | Strawberries, tomatoes, cabbage, cauliflower |
| Relative humidity formula | 100 × aw |
| Most fresh foods water acitivity is aw: | 0.99 |
| Most spoilage bacteria do not grow below water activity aw: | 0.91 |
| Spoilage nolds can grow as low as water activity aw: | 0.80 |
| Adding solutes like salt/sugar can? | Lower water activity and shrink/kill cells |
| Freezing food effect to unavailability of water to microbes | Ice is unavailable water , low temperature slows down microbial growth |
| Oxidation reduction potential or redox potential | The reducing and pxidizing power of food will influence tge type of organism and chemical changes produced in food |
| Oxidizing agents example | O2, SO4 |
| Reducing agents example | Sulfhydryl groups, ascorbic acid, reducing sugars |
| An oxidizing agent is also known as | Electron acceptor |
| A reducing agent is also known as | Electron donor |
| Nutrient content | Directly influences the growth of microorganisms |
| Antimicrobial constituent in eggwhite | Lysozyme |
| Anticrobial constituent in milk | Lactenin |
| Antimicrobial constituent in cranberries | Benzoic acid |
| Antimicrobial constituent in cinnamon | Cinnimic aldehyde |
| Biological structures | The natural covering of some foods which provide protection against the entry of microorganisms and subsequent damage |
| The water activity, ph, redox potential, nutrients content, antimicrobial constituents in food, and biological structure are what parameters? | They are the intrinsic parameters |
| The temperature, relative humidity, presence and conc of gases in the environment, and presence and acts of other organisms are what parameters? | They are the extrinsic parameters |
| Extrinsic parameters | Properties of the storage environment that affects both the foods and their microorganisms |
| Pschrophile | Type of bacteria that grow well below 20 degree C with optimum temp between 20 to 30 |
| Mesophile | Bacteria that grow well at temps 20 and 45 with optimum between 30 and 40 |
| Thermophile | Bacteria that grow well above 45 degree C with optimum between 55 to 65 degree C |
| What genera are usually considered psychotrophs? | Genera pseudomonas and enterococcus |
| What genera are thermophilic | Genera Bacillus and Clostridium |
| Example of genera of molds that grow well at wide temperature, found in eggs | Genera Aspergillus |
| Relative humidity (RH) | The amount of water vapor in air, in % of the maximum that air can hold at any given temp |
| Why is there more moisture in warm air | Envi with high RH: food will pick up moisture until equilibrium has been established |
| Capnophiles | Microorganisms that thrive in CO2 rich environments |
| Campylobacter spp | Microorganisms that require CO2 in their metabolism, campylobacter coli/jejuni |
| Co2 | Gas that slows down fungal rotting, extend shelf life |
| Overall effect of co2 | Increase both lag phase and generation time of spoilage microbes |
| What gram bacteria is more sensitive to co2 | Gram negative bacteria |
| Ozone O3 | Gas added to food storage envi with preservative effect, but it is a strong oxidizing agent and cannot be used for high lipid containing foods |
| Why Ozone should not be used for high lipid foods | It can cause increase in rancidity |
| Hurdle technology | Method of preservation that usually combine teo parameters like combine bacteria inhibiting or killing factors such as salt, reduced ph, low aw, heat treatment etc. |
| Greatest tolerance to low aw occurs at the ____ temp | Optimum |
| If ph is below or greater than optimum, the aw must be______ | Greater |
Created by:
honeybunch
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