What does the microorganism need to grow?

1. …………. 2. …………. 3. …………. 4. …………. 5. …………. 6. …………. 7. …………. Factors affecting microbial growth in food

 Temperature  Water (water activity Aw)  Oxygen availability O 2  Presence of nutrition  pH - acidity  Presence of antimicrobial substances  Physical structure Factors affecting microbial growth in food

 The most important factor affecting microbial growth  Optimum: 37°C  lower temperatures retard microbial growth  Higher temperatures eliminate microbes ◦ refrigeration at 5°C retards but does not stop microbial growth ◦ microorganisms can still cause spoilage with extended spoilage ◦ growth at temperatures below -10°C has been observed Temperature Sterilisation Pasteurisation Cooling Freezing Frozen food !!!

 To prevent growth  To eliminate Temperature (2)

Water activity 01 Pure water No water  Water Activity – Aw: Amount of Water available for chemical reactions and microbial growth   Most Fresh Foods - Aw > 0.99 !

 Foods with lower water activity: ……………………………  Foods with higher water activity:……………………………  Water activity lowered by:  drying  addition of salt or sugar  freezing Water activity (2) 01 Pure water No water

 Moulds< Yeasts < Bacteria << Water activity (3) Spoilage Bacteria 0.91 Spoilage Yeasts0.88 Spoilage Moulds0.80

 The best source of bacteria in your kitchen? a) fridge b) sponge c) sinkd) dustbin Quiz

 Aerobic– must have oxygen Pseudomonas aeruginosa  Anaerobic - no oxygen Clostridium botulinum  Micro-aerophiles- small amounts of oxygen Helicobacter pylori  Facultative anaerobes – both aerobic and anaerobic Escherichia coli, Listeria, Staphylococcus Oxygen

 Preservation: Changes with packaging – canning, MAP, vacuum packaging Oxygen (2)

 Moulds>Yeasts>Bacteria  Optimal:  Meat, corn, vegetable, eggs pH 6-7  pH: most pathogens not grow below pH 4.5 (except Lactic acid bacteria), Clostridium botulinum: pH 4.5  Yeast and Moulds can grow at lower pH.  Acidic Foods-fruits, soft drinks, vinegar, wines, Citrus fruits, pickles, kiwi, condiments (mayo) pH<3,5  Fermentation and acidification to reduce pH pH - acidity

 Presence of nutrition  Bacteria need protein, fats, vitamins, minerals  Structure ◦ G rinding and mixing increase surface area and distribute microbes - promotes microbial growth ◦ Outer skin of vegetables and fruits slows microbial growth are natural microbiological barriers - Whole lemons last longer than slices ◦ Shells on nuts and eggs

 Antimicrobial Factors: ◦ Organic acids (fruits), some enzymes (milk and egg), essential oils (spices), pesticides, antibiotics, food preservatives, chlorine. ◦ Naturally occurring factors ◦ coumarins – fruits and vegetables ◦ lysozyme – cow’s milk and eggs ◦ aldehydic and phenolic compounds – herbs and spices ◦ allicin – garlic ◦ polyphenols – green and black teas ◦ Preservatives:E 200 – E 285 Antimicrobial Factors

 Bacteria are single-celled microorganisms found in nearly all natural environments.  Size: ◦ 10 µm length, 0,5-2,5 µm diameter  Morphology: Morphological types are grouped into the general categories of: spherical (the cocci), cylindrical (the rods) and spiral. Bacteria

 Unicellular microorganisms  2-6 µm width and µm  Important role both in ◦ production and ◦ spoilage of food  pH > 4.5 Fungi - Yeasts

 Multicellular microorganisms  1.6 – 9.3 µm  Ability to produce toxins (peanut, maize) Aspergillus  Food spoilage Rhisopus, Penicillum  Food production Roquefort cheese Fungi - Moulds

 Toxin in the farm!  Mycotoxins can appear in the food chain as a result of fungal infection of cropsfungal infectioncrops  cooking and freezing, do not destroy mycotoxins  Aflatoxin  Ochratoxin  Fusarium toxins  Patulin Fungi - Moulds Cancer, kidney’s damage, damage of immune and nervous systems, death.

 Alive or not?  They require living cells of plants, animals, or bacteria for growth.  Extremely small (0.2 – µm )  Only visible with electronic microscope  Sources: ◦ Water, foods  Pathogen Viruses

 Results from growth of microbes in food  Sometimes harmful  Bacteria tend to spoil moist foods; fungi dry or acidic foods  Spoilage organisms cost the food industry millions of dollars each year. Food spoilage

„GOOD”- Why do we need them?

 Bread involves growth of Saccharomyces cerevisiae (baker’s yeast) under aerobic conditions  Dairy Products Yoghurt: Milk is fermented by a mixture of Streptococcus salivarius ssp thermophilus and Lactobacillus bulgaricus Cheese: milk is treated with lactic acid bacteria  Other Fermented Foods ◦ sausages ◦ hams ◦ bologna ◦ salami ◦ izushi – fish, rice, and vegetables ◦ katsuobushi – tuna ◦ sauerkraut Good microbes - Why do we need them in a food industry?

Why do we love them?  „Wine is fine”  Produced from the fermentation of fruit juice, usually from grapes “Liqueur is quicker” Produced by the fermentation of grain mash followed by distillation to increase the alcohol content  „Beer is dear”  Produced by the fermentation of malted grain

Why do we hate some of them? - Food born diseases

Physical and chemical hazards

 Hazard – a biological, chemical or physical agent, or condition of food with the potential to cause an adverse health effect  In addition to biological agents (bacteria, viruses, parasites), there are further contamination risk in foods:  Chemical  Physical  Condition of food What is the hazard?