Food Spoilage

Prepared by

القزاز عدنان محمد

Supervisor

المناعمة الرؤوف عبد

Food spoilage :means the original nutritional value, texture, flavor of the food are damaged, the food become harmful to people and unsuitable to eat.

:Food poisoning (or food borne illness ) is an illness that you

may get after eating food contaminated by , , , certain bacteria parasites viruses or

chemicals.

Conditions for Spoilage :

•Water

•pH

•Physical structure

•Temperature

Intrinsic Factors: Composition

pH

presence and availability of water

physical structure

presence of antimicrobial substances

Composition and pH

pH impacts make up of microbial community and therefore types of chemical reactions that occur when microbes grow in food

Water availabilityin general, lower water activity inhibits microbial growth

water activity lowered by:DryingAddition of salt or sugar

osmophilic microorganismsprefer high osmotic pressure

xerophilic microorganismsprefer low water activity

Physical structure

grinding and mixing increase surface area and distribute microbes promotes microbial growth

outer skin of vegetables and fruits slows microbial growth

Antimicrobial substancescoumarins – fruits and

vegetables

lysozyme – cow’s milk and eggs

aldehydic and phenolic compounds – herbs and spices

allicin – garlic

polyphenols – green and black teas

Extrinsic FactorsTemperature :

lower temperatures retard microbial Growth

relative humidity :higher levels promote microbial growth

Atmosphere :oxygen promotes growthmodified atmosphere packaging (MAP)

use of shrink wrap and vacuum technologies to package food in controlled atmospheres

Microbial Growth and Food Spoilage

food spoilageresults from growth of microbes

in food alters food visibly and in other ways, rendering it unsuitable for consumption

different foods undergo different types of spoilage processes

toxins are sometimes produced algal toxins may contaminate shellfish and finfish

Microbial spoilage :

There are three types of microorganisms that cause food spoilage -- yeasts, moulds and bacteria.

•Yeasts growth causes fermentation which is the result of yeast metabolism. There are two types of yeasts true yeast and false yeast. 

True yeast metabolizes sugar producing alcohol and carbon dioxide gas. This is known as fermentation.

 False yeast grows as a dry film on a food surface, such as on pickle brine. False yeast occurs in foods that have a high sugar or high acid environment.

•Moulds •grow in filaments forming a tough mass which is visible as `mould growth'. Moulds form spores which, when dry, float through the air to find suitable conditions where they can start the growth cycle again.

•Mould can cause illness, especially if the person is allergic to molds. Usually though, the main symptoms from eating mouldy food will be nausea or vomiting from the bad taste and smell of the mouldy food.

•Both yeasts and moulds can thrive in high acid foods like fruit, tomatoes, jams, jellies and pickles. Both are easily destroyed by heat. Processing high acid foods at a temperature of 100°C (212°F) in a boiling water canner for the appropriate length of time destroys yeasts and moulds.

Fungal SpoilageStorage rot in grapes caused

by Botrytis cinerea.

Storage rot in strawberry caused by Botrytis cinerea.

Blue mould rot in tomato caused by Penicilliumi spp. (also

by Fusarium spp.)

Black mummy rot of grapes caused by Guignardia bidwellii

Watery soft rot in apple caused by Sclerotinia sclerotiorum.

Blue mould on oranges caused by Penicillium digitatum.

•Bacteria are round, rod or spiral shaped microorganisms. Bacteria may grow under a wide variety of conditions. There are many types of bacteria that cause spoilage. They can be divided into: sporeforming and nonspore-forming. Bacteria generally prefer low acid foods like vegetables and meat. In order to destroy bacteria spores in a relatively short period of time, low acid foods must be processed for the appropriate length of time at 116°C (240°F) in a pressure canner. Temperatures higher than 100°C [212°F] can be obtained only by pressure canning

•Eatting spoiled food caused by bacteria can cause food poisoning.

Soft rot in tomato caused by Erwinia

carotovora

Microorganisms involved in food spoilage(Other than Canned Foods) with some examples of causative organisms

Food Type of Spoilage Microorganisms involved

BreadMouldy

Rhizopus nigricans Penicillium 

Aspergillus niger

Ropy Bacillus subtilis

Maple sap and syrup

Ropy Enterobacter aerogenes

YeastySaccharomyces 

Zygosaccharomyces

Pink Micrococcus roseus

MouldyAspergillus Penicillium

Fresh fruits and vegetables

Soft rotRhizopus Erwinia

Gray mold rot Botrytis

Black mold rot A. niger

Pickles, sauerkraut Film yeasts, pink yeasts Rhodotorula

Fresh meat Putrefaction

Alcaligenes Clostridium 

Proteus vulgaris Pseudomonas fluorescens

Cured meat

MouldyAspergillus Rhizopus Penicillium

SouringPseudomonas Micrococcus

Greening, slimeLactobacillus Leuconostoc

Fish

Discoloration Pseudomonas

PutrefactionAlcaligenes 

Flavobacterium

Eggs

Green rot P. fluorescens

Colorless rotsPseudomonas 

Alcaligenes

Black rots Proteus

Concentrated orange juice "Off" flavorLactobacillus Leuconostoc Acetobacter

Poultry Slime, odorPseudomonas 

Alcaligenes

Diseases of spoiled food

two primary typesfood-borne infectionsfood intoxications

Food-Borne Intoxications

ingestion of toxins in foods in which microbes have grown

include staphylococcal food poisoning, botulism, Clostridium perfringens food poisoning, and Bacillus cereus food poisoning

Toxins ergotism

toxic condition caused by growth of a fungus in grains aflatoxins

carcinogens produced in fungus-infected grains and nut products

fumonisins carcinogens produced in fungus-infected corn

•EnzymesEnzymes are proteins found in all plants and animals. If uncooked foods are not used while fresh, enzymes cause undesirable changes in colour, texture and flavour. Enzymes are destroyed easily by heat processing.

•Oxidation by airAtmospheric oxygen can react with some food components which may cause rancidity or color changes.

Other factors

Infestations (invasions) by insects and rodents, which account for huge losses in food stocks.

Low temperature injury - the internal structures of the food are damaged by very low temperature.

Controlling Food Spoilage

Removal of Microorganisms

usually achieved by filtration

commonly used for water, beer, wine, juices, soft drinks, and other liquids

Low Temperature

refrigeration at 5°C retards but does not stop microbial growth psychrophiles and psychrotrophs

can still cause spoilage growth at temperatures below -10°C

has been observed

High Temperature

Canning

Pasteurization

Canning

food heated in special containers (retorts) to 115 °C for 25 to 100 minutes

kills spoilage microbes, but not necessarily all microbes in food

Pasteurization

kills pathogens and substantially reduces number of spoilage organisms

different pasteurization procedures heat for different lengths of time shorter heating times result in

improved flavor

Radiation

ultraviolet (UV) radiation used for surfaces of food-handling

equipment does not penetrate foods

Gamma radiation use of ionizing radiation (gamma

radiation) to extend shelf life or sterilize meat, seafoods, fruits, and vegetables

Detection of Food-Borne Pathogens

must be rapid and sensitive methods include:

culture techniques – may be too slow

immunological techniques - very sensitive

molecular techniques probes used to detect specific DNA

or RNA sensitive and specific

T ANKH S