Food tech Flashcards
What are the main intrinsic factors affecting microbial behavior in foods?
Nutrient Availability: Microorganisms require water, energy sources (e.g., sugars, alcohols, amino acids), nitrogen, vitamins, and minerals.
pH: Most microorganisms grow best at pH 6.6–7.5. Some resist changes in pH (e.g., buffered foods like meats).
Redox Potential (Eh): Reflects the food’s ability to gain/lose electrons, impacting microbial growth (aerobes need positive Eh; anaerobes need negative Eh).
Water Activity (aw): Measures how water participates in chemical reactions. Low aw preserves food by limiting microbial growth.
Natural Antimicrobials: Found in some foods (e.g., lysozyme in eggs, lactoferrin in milk).
Food Matrix: Mechanical barriers like skin or membranes.
What are the main extrinsic factors affecting microbial behavior in foods?
Temperature: Microbial growth ranges from psychrophiles at 15°C or lower to thermophiles above 45°C. D and Z values describe thermal destruction.
Relative Humidity (RH): High RH favors spoilage by molds and bacteria; low RH can prevent surface spoilage.
Atmosphere: Gases like CO₂ (MAP) and ozone have antimicrobial properties.
Time: Critical during storage, preparation, and handling.
What are the basic aspects of microbial food spoilage?
Chemical/Biochemical Changes:
Carbohydrates: Fermentation produces acids, alcohols, and gases.
Proteins: Breakdown releases ammonia and sulfur compounds.
Fats: Oxidation leads to rancidity.
Sensory Changes: Alterations in taste, odor, color, texture, or combination of these.
Accumulation of Detrimental End-Products: Compounds that reduce food quality.
How does food preservation work to prevent microbial growth?
Lowering Water Activity (aw): Drying or adding solutes (salt, sugar).
Temperature Control: Refrigeration, freezing, pasteurization.
Atmosphere Control: Vacuum packaging, CO₂ use in MAP.
Use of Natural or Added Antimicrobials: Essential oils, lysozyme, or preservatives.
What do D and Z values represent in food microbiology?
D-Value (Decimal Reduction Time): Time required to reduce 90% of a microbial population at a specific temperature.
Z-Value: Temperature change needed to alter the D-value by a factor of 10.
What are common symptoms of food spoilage?
Organoleptic Changes: Altered taste, odor, appearance, or texture.
Physical Damage: Freezer burn, staling, bruising.
Foreign Bodies: Hair, soil, or contaminants.
Chemical Contamination: Cleaning agents or environmental pollutants.
What are the technical aspects and effects of meat processing on microbiology and quality?
Meat Cutting, Deboning, and Mincing:
Increases surface area for microbial activity.
Introduces spoilage organisms and pathogens like Salmonella.
Meat Curing:
Addition of salt, nitrites, and nitrates.
Inhibits Gram-negative bacteria and enhances growth of lactic acid bacteria.
Meat Fermentation:
Utilizes starter cultures (e.g., Lactobacillus plantarum, Pediococcus acidilacti).
Produces lactic acid, lowering pH and reducing water activity for preservation.
What are the main food preservation technologies?
Canning:
Minimum heat process ensures 12 decimal reductions of Clostridium botulinum.
Spoilage may occur from underfilling, seam issues, or poor hygiene.
Smoking:
Antimicrobial compounds in smoke (e.g., formaldehyde, phenols) inhibit microorganisms.
Drying:
Reduces water activity to inhibit microbial growth.
What are the technical aspects of producing dairy products like cheese, yoghurt, and butter?
Cheese Production:
Pasteurization removes pathogens and spoilage flora.
Rennet coagulates milk proteins, with lactic acid development enhancing flavor and texture.
Yoghurt Production:
Involves fermentation of lactose into lactic acid using Streptococcus thermophilus and Lactobacillus bulgaricus.
Types: Set, stirred, and drinkable.
Butter Production:
Churning cream to separate fat and buttermilk, followed by salting and packaging.
What are the principles for microbiological testing and sampling plans?
Targets for Testing:
Total microorganism numbers.
Indicator organisms and pathogens (E. coli, Listeria monocytogenes).
Sampling Plans:
Two-Class Plan: Tests for presence/absence. Parameters: n (number of samples), c (acceptable defective samples), m (limit).
Three-Class Plan: Adds M (maximum limit).
How is shelf life determined, and what is challenge testing?
Shelf-Life Evaluation:
Assesses organoleptic qualities (flavor, texture), microbial growth, and product stability under various storage conditions.
Challenge Testing:
Inoculates food with specific organisms (e.g., Listeria monocytogenes).
Monitors growth, death, or survival under controlled conditions.
What are the characteristics of fermented meat products like sausages?
Made from pork, beef, or other meats with salt, nitrites/nitrates, and fermentable carbohydrates.
Fermentation produces lactic acid, reducing pH (~4.8) and water binding capacity.
Drying lowers water activity; ripening develops flavor via protein and fat breakdown.
How are microbiological criteria used in the food industry?
Purpose: Ensure food safety and quality.
Parameters:
Pathogens (Salmonella, Listeria).
Spoilage organisms.
Sampling frequency and sample type.
Conformance involves testing against defined limits using industry standards (e.g., EC Regulation 2073/2005).
