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Food spoilage student Food spoilage Definition n Food spoilage can be defined as a disagreeable change in a food''''s normal state n NOT acceptable for human consumption and for food industrial usage n S[.]
Food spoilage Definition n n n Food spoilage can be defined as a disagreeable change in a food's normal state NOT acceptable for human consumption and for food industrial usage Such changes can be detected by smell, taste, touch, or sight (disgusting) n Food safety ↔ food quality Classifications of food spoilage n Stable or non perishable foods (sugar, flour, dry beans) n Semi perishable foods Foods handled and stored properly → remain unspoiled for long period (potatoes, apples) n Perishable foods Spoil readily without special preservative methods (fish, meat, eggs, milk) Main causes of food spoilage q Physical changes n n q aw, temperature, mechanical effects Caused by the inappropriate transport, handling and storage Biological factors n Microbiological q n Macrobiological q q bacteria, yeasts, moulds (most common) rodents, insects, birds, parasites Chemical, biochemical factors n n non-microbial or enzymatic changes usually involving oxygen → oxidation processes (e.g., rancidity of fats and oils) activity of endogenous tissue enzymes (food of vegetable or animal origin) Consequences/effects of food spoilage q changes in nutritional value n q changes in organoleptic features n q Decomposition of proteins, carbohydrates, vitamins colour, flavour, taste, consistency → mucilaginous surface, unpleasant odour, unwholesome effects n n n Biogenic amines, toxins, Metabolites of microorganisms Pathogen microbes Sources of microbial spoilage n Ubiquiter microorganisms q n Can originate from: natural habitat of microorganisms; e.g soil, water, air, Special sources contamination q q q q Spoiled raw materials Food waste Biofilm on the surface of equipments Human → personal hygiene Ubiquiter microorganisms • natural habitat of microorganisms is the soil (except for pathogen bacteria) • Way of contamination of animals and plants can be direct from soil or indirect by water or air • Related microorganisms: – Gram (-): Pseudomonas, Acinetobacter, Alcaligenes, Enterobacter spp.; – Gram (+): Micrococcus, Arthrobacter, Streptomyces spp.; – Aerobic and anaerobic sporoforms: Bacillus, Clostridium Ubiquiter microorganisms • Microorganisms can contaminate the surface of plant or fur and skin of animals • These are not harmful for plants or animals, but after harvesting or slaughtering can cause spoilage during storage of products (Micrococcus, Lactobacillus spp.) • Meat products also can be contaminated by microorganisms from mouth (Streptococcus spp.) or from the gastrointestinal tract (Bacteroides, Eubacterium, Clostridium spp) Special sources contamination • Surfaces of equipment, instruments, utensils, the wall and floor surfaces, – Inappropriate hygiene of plant → Food waste → resulting a specified, adapted micro-flora typical to plant and products • Spoiled raw material – Plant: mechanical lesions during the harvesting, transport can enhance the penetration of microbes into the deeper tissues – Animal: contaminated mainly during slaughter • Rodents, insects (fly, fruit fly, bee, wasp) can contaminate the products during storage and processing Characteristic of microorganisms • Reproductive potential – Among optimal circumstances the fastest – The fastest growing microbe becomes dominant (mainly bacteria, but …) • Metabolism, nutrient requirements – Substrate → metabolism in cells → metabolites (useful or harmful) – The process is influenced by the environment (presence/absence of oxygen, available nutrients)