13.7.2014 Intrinsic and extrinsic environmental food factors What do bacteria need to grow? LU B O M I R VA L I K Outlines Food processing - Food environment - Microorganisms aw T pH Cardinal values Factors affecting microbial growth/behaviour in foods Intrinsic factors Extrinsic factors Implicit factors Processing factors Determine Type, extent and rate of microbial changes Shelf-life of foods Contribute to food safety 1 You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) 13.7.2014 Factors affecting microbial growth/behaviour in foods Intrinsic factors Nutrients pH and buffering capacity Redox potential Water activity Antimicrobial structures Extrinsic factors Implicit factors Processing factors Factors affecting microbial growth/behaviour in foods Intrinsic factors Extrinsic factors Relative humidity Temperature Gazeous atmosphere Time Implicit factors Processing factors Factors affecting microbial growth/behaviour in foods Intrinsic factors Extrinsic factors Implicit factors Specific growth rate Synergism Antagonism Commensalism Processing factors 2 You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) 13.7.2014 Factors affecting microbial growth/behaviour in foods Intrinsic factors Extrinsic factors Implicit factors Processing factors Heat treatment Washing Packing Slicing Irradiation Factors affecting microbial growth/behaviour in foods Intrinsic factors Extrinsic factors Implicit factors Processing factors Heat treatment Washing Packing Slicing Irradiation FOOD SPOILAGE FOOD SAFETY HAZARD FOOD SUITABILITY FOOD SAFETY MULTIPLICATION / GROWTH CONTROL INTRINSIC FACTORS • aw value • pH • Eh value • Nutritive potential • Structure •Antimicrobial constituents IMPLICIT FACTORS • Symbiosis • Antagonism • Competitivness • Commensalism • Antibiosis EXTRINSIC FACTORS • Temperature • Time • Gaseous atmosphere COMPOSITION OF MICROFLORA PROCESSING FACTORS Technology of production (washing, slicing, heat treatment, preservation, irradiation, packaging) Transportation, Storage 3 You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) 13.7.2014 Nutritive potential Abundance of nutrients Limiting – ability/inability of utilization cereals vs. amylolytic enzymes Macromolecules Available key nutrients determine Extent Rate of microbial growth and metabolism Water activity/ aw - value Availability of water Related to osmotic pressure Microbial osmoregulation Compatible solutes Polyols: glycerol, arabitol, manitol a w p 1 ERH p 0 100 freezing point depression T ln a w 9 . 6934 10 3 T 4. 761 10 6 T 2 Most microorganisms grow well at aw > 0.98 No microbial growth aw < 0.61 Water activity/ aw - value Water activity affects behavior of microorganisms Growth Sporulation Toxin production Survival during processing storage Recovery on agar media Chemical reactions Enzyme activity 4 You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) 13.7.2014 Minimal aw - value Specific for species Depends on the factors Temperature pH Nutrient availability Antimicrobial substances Type of solute aw - value NaCl [% w/w] 0.99 1.7 0.98 3.4 0.96 6.5 0.94 9.3 0.,92 11.9 0.90 14.1 0.88 16.2 0.86 18.1 0.85 - 0.84 19.9 0.82 21.5 0.80 23.1 0.75 26.5* Minimum aw for growth of microorganisms Range of aw 1.00 – 0.95 0.95 – 0.91 Microorganisms inhibited by lowest aw in this range Foods generally within this range Pseudomonas, Escherichia, Proteus, Shigella, Klebsiella, Bacillus, Clostridium Highly perishable (fresh) foods and canned fruits, vegetables, meat, fish, and milk; cooked sausages and breads, foods containing 40 % (w/w) sucrose or 7% NaCl Salmonella, V. parahaemolyticus, C. botulinum, Pediococcus, some molds, yeasts (Rhodotorula, Pichia) Some cheese (Chedar, Swiss, Provolone), cured meat (ham), some fruite juice concentrates, foods containing 55% (w/w) sucrose or 12 % NaCl Minimum aw for growth of microorganisms Range of aw 0.91 – 0.87 0.87 – 0.80 Microorganisms inhibited by lowest aw in this range Foods generally within this range Many yeasts (Candida, Torulopsis, Hansenula), Micrococcus Fermented sausages (salami), sponge cake, dry cheeses, margarine, foods containing 65 % (w/w) sucrose or 15% NaCl Most moulds (mycotoxigenic penicillia), Staphylococcus aureus, most Saccharomyces, Debaryomyces Most fruite juice concentrates, sweetened condesed milk, chocolate syrups, flour, rice, pulses containing 15-17% moisture, country-style ham, fondants, highratio cakes 5 You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) 13.7.2014 Minimum aw for growth of microorganisms Range of aw Microorganisms inhibited by lowest aw in this range Foods generally within this range 0.80 – 0.75 Most halophilic bacteria, mycotoxinogenic aspergilli Jam, marmelade, marzipan 0.75 – 0.65 Xerophilic moulds (Aspergillus chevalieri, A. candidus, Walemia sebi), Saccharomyces bisporus Rolled oats containing approx. 10 % moisture, grained nugats, jelly, raw cane sugar, some dried fruits, nuts 0.65 – 0.61 Osmophilic yeasts (Zygosaccharomyces rouxii), few moulds (Aspergillus echinulatus, Monascus bisporus) Dried fruits containing 15-20 % moisture, some toffees and caramels, honey Minimum aw for growth of microorganisms Range of aw Microorganisms inhibited by lowest aw in this range 0.50 0.40 0.30 0.20 No microbial proliferation No microbial proliferation No microbial proliferation No microbial proliferation Foods generally within this range Pasta containing 12% moisture, spices containing approx. 10% moisture Whole egg powder containing aprox. 5 % moisture Cookies, some crackers, etc. Containing 3.5 % moisture Whole milk powder containing 2-3% moisture. Dried vegetables ocntaining 5% moisture, corn flakes cont. 5% moisture, some crackers Minimal aw – values for growth Species Most of bacteria Bacillus subtilis Pseudomonas spp. Bacillus cereus Clostridium botulinum E Clostridium botulinum A,B C. perfringens Salmonella typhimurium > 0.95 0.99 0.97 0.93 0.97 0.95 0.93 0.94 Most of moulds Aspergillus candidus Aspergillus flavus Aspergillus nidulans Aspergillus terreus Aspergillus versicolor Aspergillus ochraceus Min aw > 0.85 0.75 0.78 0.78 0.77 Salmonella orianenburg 0.92 Penicilium chrysogenum 0.81 Vibrio parahaemolyticus Lactobacillus spp. Staphylococcus aureus Halobacterium spp. 0.95 0.88 0.86 0.75 Penicillium citrinum Penicillium cyclopium Penicillium expansum Penicillium viridicatum 0.80 – 0.82 0.81 0.82 0.81 Most of yeasts A, D two organisms adapted to a different aw B, C – different humectant Ross (1999) Min aw Species > 0.85 Rhodotorula, Pichia 0.92 Candida, Torulopsis 0.88 Sacharomyces, Hansenula Debaryomyces hansenii Zygosaccharomyces bailii Zygosacharomyces rouxii 0.90 0.83 0.80 0.62 Rhizopus nigricans 0.93 Walemia sebi Eurotium chevalieri Eurotium echinulatum Monascus bisporus 0.75 0.71 0.62 0.61 6 You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) 13.7.2014 Minimal aw – values for growth aw = 0.99 aw = 0.96 Mc Meekin and Ross (1996) aw – value for food storage Nuts – water content 4-9 % Protein rich legumes 9-13 % the same aw - value Dried fruits 18-25 % aw > 0.95 aw ≤ 0.85 av ≤ 0.75 av ≤ 0.65 av ≤ 0.60 - a few days - two weeks - two months - two years - no limit Critical water content – value for food storage Dehydraed fruits 18-25 % 18 % Dehydraed vegetables 14-20 % Milk powder 15 % Dehydrated meat 15 % Rice, wheat flour 13-15 % Dehydrated whole eggs 10-11 % Whole milk powder 8% Starch 7 You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) 13.7.2014 Measuring aw - value Direct methods Indirect method Gravimetric method by Landroc and Proctor (1953) Instrumental methods Dew point Freezing point rRH % Resistive electrolytic cell Capacitive measurement Acidity/ pH - value pH = - log (aH+) = log 1/ (aH+) log 1/[H+] Acidity/alkalinity affect stability of macromolecules Enzymes Growt and metabolism Fastest growth Bacteria - pH of 6.0 – 8.0 Yeasts - pH of 4.5 – 6.0 Filamentous fungi - pH of 3.5 – 4.0 Range of pH value for growth of selected microorganisms A) B) C) Alcaligenes faecalis in broth In broth + 0.2 % Na Cl In broth + 0.2 M Na ci trate 8 You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) 13.7.2014 Minimal pH value for growth of selected microorganisms pH value Approximate pH ranges of some common food commodities pH 14 13 12 11 10 9 8 7 6 5 4 3 2 Fermented shark Egg white fish milk flour meat Citrus fruits Soft drinks vegetables beer pH value of the product Rate of food spoilage Character of food spoilage Vegetables – moderately acid pH Soft-rot producing E. carotovora and pseudomonads Fruits – lower pH Yeasts and molds dominate in spoilage Buffering capacity Important – concentration of undissiociated weak acid 9 You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) 13.7.2014 Redox potential/ Eh - value Tendecy of medium to accept/donate electrons ae ro b i c en v i r o n me nt Canned food - 100 mV Ripened cheeses Post-rigor meat -200 mV -300 mV perfringens 0 mV Clostridium Fresh meat Heat treated milk Obr. Redoxné + 100 mV potenciály niektorých potravín a baktérií Redox couples Ratio oxidant to reductant pH Equilibrium capacity Availability of oxygen Microbial activity Clostridium spp. raw milk + 200 mV Optimal growth and toxin production Foods of plant origin methylene blue (leucoform) + 300 mV Staphylococcus aureus + 400 mV Pseudomonas fluorescens + 500 mV Eh E0 R.T [ox] ln n. F [ red ] oxidation an ae ro b i c e n vi ro n me n t - reduced substance oxidized substance + n×e reduktion Cardinal values for growth of toxinogenic bacteria Factors Clostridium botulinum Group I Group II Staphylococcus aureus Bacillus cereus Clostridium perfringens < 15 °C T < 10 °C < 3.5 °C < 10 °C < 4 °C pH < 4.6 < 5.0 < 4.5 < 4.4 < 5.,0 aw < 0.94 < 0.97 < 0.86 < 0.91 < 0.95 Eh > +200 mV > +200 mV > +200 mV Minimal pH - values, water activity (aw) and temperature *Min. pH Max. % NaCl Min. aw Tmin 5.0 5 0.97 3.3 °C 4.6 10 0.94 10 °C 5.0 7 0.93 7 °C Staphylococcus aureus 4.1 18 0.86 7 °C Bacillus cereus 4.6 12 0.92 4 °C Vibrio parahaemolyticus 4.8 10 0.94 5 °C Yersinia enterocolytica 4.2 7 0.95 -1 °C 4.4 10 0.92 -0.4 °C 4.5 4.4/*5.4 5 8 0.97 0.94 10 °C 5.2 °C Mikroorganism C. botulinum typ E a non-prot. group B a F C. botulinum typ A a prot. group B a F Clostridium perfringens Listeria monocytogenes Plesiomonas shigelloides Salmonella spp. kys. mliečna/*kys. octová Lactic acid/*acetic acid 10 You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) 13.7.2014 Minimal aw – values for growth and toxin production Toxins Growth Toxin production Aspergillus flavus Species aflatoxin B1 0.78 – 0.80 0.83 Aspergillus parasiticus aflatoxin B1 ochratoxin ochratoxin A ochratoxin A 0.82 0.77 0.76 0.81 0.87 0.85 0.80 0.87 Penicillium viridicatum ochratoxin A 0.83 0.83 Aspergillus ochraceus penicilinic acid 0.76 0.81 Penicillium cyclopium penicilinic acid 0.81 0.87 patulin 0.81 0.85 stachybotrin kys. mliečna/*kys. 0.82 – 0.84 0.94 0.99 0.94 Aspergillus ochraceus Penicillium cyclopium Penicillium patulin Penicillium expansum Stachybotrys altra octová Temperature Microbial growth from -8°C up to 100°C Temperature span of 35 °C for bacteria Temperature span of 30 °C for moulds Mesophilic and psychrotrophic – greatest importance in food microbiology Temperature [°C] Group Minimum Psychrofiles (obligate psychrophiles) Psychrotrophs (facultative psychrophiles Optimum Maximum -5 ... +5 12 ... 15 15 ... 20 -5 ... +5 25 ... 30 30 ... 35 Mesofiles +5 ... 15 30 ... 40 40 ... 47 Thermophiles 40 ... 45 55 ... 75 60 ... 90 Relative humidity Interrelated to water activity Water tranfers between areas with diferent RH Physiologically active microorganisms may produce water Condensation water in grain silos Caking grain Microbial growth Different critical RH-values The same critical aw-value 11 You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)
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