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Microbiological Changes, Intrinsic Factors, Extrinsic Factors, Implicit…
Microbiological Changes
food preservation
goal: to satisfy the needs of modern consumers > use good-quality raw materials + keep food from losing its quality
ensures that the product > stays fresh or well-prepared + keeps its quality from collection to consumption
industrial reason: enjoy foods that are out of season + have high-quality food + have food that's quick & easy to prepare
all actions & processes to: keep food in the best condition for as long as possible + reduce changes that lower quality or hygiene
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- decide which food qualities to keep 2. understand what causes food to spoil 3. use the best preservation methods
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qualities to preserve
sensory: maintain taste, smell & texture
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hygienic & organoleptic: prevent contamination & preserve appearance, flavor & aroma
food stability
- perishable: spoil quickly (eg. meat, fish, milk)
- semi-perishable: last longer with proper care (eg. potatoes, apples, nuts)
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- non-perishable: almost never spoil (eg. sugar, flour, salt)
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preventing food spoilage
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environmental conditions: temperature, humidity, light
processing methods: use techniques like freezing, drying or sealing
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physical methods
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new methods: irradiation, high pressure or electric pulses
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general principles
from raw materials: water, soil, air or animal surfaces
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types of microorganisms
spoilage microorganisms: change food's smell, color or taste but aren't harmful
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helpful microorganisms: used to make products like yogurt, cheese or butter
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Intrinsic Factors
physical state
damage (bruises, cuts) > makes food more vulnerable
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natural protection: skins (fruits), shells (eggs)
chemical properties
oxidation-reduction potential (Eh): foods with more oxygen (high Eh) > oxidizing & favor aerobic microbes + foods with less oxygen (low Eh) > reducing & favor anaerobic microbes
water activity (aw): microbes need water + less water in food > slows their growth + examples: salted meats, honey, jams last longer
pH: low pH (acidic) protects food (eg. fruits resist bacteria but can attract molds + microbes grow slower at pH levels not optimal for them + acid addtives can further improve preservation
nutrients
microorganisms need water, energy, nitrogen, vitamins & minerals
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Implicit Factors
microbial relationships
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antagonism: some microbes slow or stop the growth of other (eg. lactic acid bacteria lower pH > killing harmful bacteria)
metabolic effects
some microbes prepare food for others to grow (eg. raw milk can allow harmful microbes to grow over time if untreated)
Consequences
chemical changes
organoleptic changes: alters color, taste & smell due to chemical reactions (oxidation, reduction)
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depolymerization: breaks down large molecules (eg. starch, pectin, proteins or fats)
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fermentation: microorganisms process carbohydrates > altering flavor (eg. souring, gas production)
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