Flashcards in Chapter 3 Factors Affecting The Growth And Survival Of Micro-organisms In Foods Deck (9)
What are the factors affecting the development of microbial associations in food?
Intrinsic factors: nutrients, pH and buffering capacity, redox potential, water activity, antimicrobial constituents and structures
Environmental factors: relative humidity, temperature, gaseous atmosphere
Implicit factors: specific growth rate, mutualism, antagonism, commensalism
Processing factors: slicing, washing, packing, irradiation, pateurization
Generally, what are the micro-organisms' optimal pH range?
Filamentous fungi 3.5-4.0
(Lactobacilli and acetic acid bacteria 5.0-6.0)
Give examples of obligate anaerobes and aerotolerant anaerobes.
Obligate: clostridia(梭菌), C. botulinum.
Aerotolerant: lactic acid bacteria.
What is the limiting value of water activity for the growth of any micro-organism?
What are the most micro-organisms' minimum water activities?
Most Gram-negative bacteria 0.97
Most Gram-positive bacteria 0.90
Most yeasts 0.88
Most filamentous fungi 0.80
Give examples of antimicrobial components.
Pigments, alkaloids(生物碱), benzoic and sorbic acids(苯甲酸和山梨酸), lysozyme, etc.
What is the growth range of bacteria and moulds?
Bacteria around 35 degree
Moulds about 30 degree
What are the reactions to CO2 of different micro-organisms?
Moulds and Gram-negative bacteria are most sensitive;
Gram-positive, particularly the lactobacilli, most resistant.
Some yeasts such as Brettanomyces spp. show considerable tolerance of high CO2 levels.