Food Spoilage in Eggs, Poultry, and Fish

UNIVERSITY OF BASRAH / COLLEGE OF SCIENCE lecture 10 Food spoilage Department of Pathological Analyses Presented by Prof.Dr. Saad S. Mahdi Al-amaradi Al-Amara

Egg Freshly laid eggs are generally sterile, but can be contaminated by environmental sources like bird fecal matter, bedding, handlers, wash water, and packaging materials. Eggs protect themselves through extrinsic and intrinsic mechanisms. lysozymes high pH (pH 9-10) high pH (pH 9-10) of albumin inhibits the microbial growth. lysozymes present in the egg white is effective against Gram positive bacteria 4 2 1 5 3 Waxy shell membrane Waxy shell membrane retards the entry of microorganisms. Further, the shell also prevents the entry of microorganisms. The membranes inside the shell behave as mechanical barriers to the entry of microorganisms. avidin Binding of riboflavin Binding of riboflavin by the apo protein and chelation of iron by conalbumin further helps in hindering the growth of microorganisms that might have gained entry inside the egg. avidin in the egg white forms a complex with biotin, thus making it unavailable for the microorganisms

Spoilage of egg Egg shell cracks due to transportation or mechanical damage can allow microorganisms to enter the egg yolk, leading to spoilage during storage. Eggs lose moisture and weight, and their white becomes thinner and more watery. Spoilage is primarily caused by bacteria, not molds. 1. green rot due to the growth of Pseudomonas fluorescens. 2. colourless rot due to the growth of Pseudomonas, Acinetobacter and other species. 3. black rots due to Proteus, Pseudomonas. 4.Red rots due toSerratia spp. 5. Custard rots due to Proteus vulgaris and Pseudomonas intermedium. 6. Growth of Aeromonas in the egg yolk turns it to black colour and also there is strong.

Spoilage of egg putrid odour due to the formation of hydrogen sulphide ( H2S ). Storage of eggs in high humid atmosphere may help in growth of several molds on the surface of the egg shell. Molds causing spoilage of eggs include species of Pencillium, Mmucor, Alterneria , etc Spoilage of poultry Poultry meat like meat of other animals is also susceptible to contamination by various sources. Contamination of skin and lining of the body cavity take place during various processing operations. The organisms of great importance in poultry are Salmonella spp. and Campylobacter jejuni. Several Gram negative psychrotropic bacteria, Pseudomonas, Acenitobacter and Flavobacterium have also been isolated from poultry carcasses.

Spoilage of fish Fish meat is free from microbes, but scales, gills, and skin contain large amounts of microorganisms. When the fish dies, these microorganisms move to the meat, contaminating the fish most from internal organs. Bacterial standard specifications limit the number of bacteria in fish flesh to half a million per gram, 200 per gram for coliform bacteria, and 100 per gram for E. coli and Staphylococcus bacteria. The most important genera usually found on fish are Pseudomonas, Achromobacter, flavobacterium, Photobacterium, Alcaligenes, Cytophaga, Serratia, Sarcina, Micrococcus, Aeromonas, Escherichia, Lactobacillus, Microbacterium, Vibrio, Cactobacillus, Microbacterium, Vibrio, Bacillus. Achromobacter Freshwater fish also contain trace numbers of bacteria from saltwater marine and infested with salt-tolerant bacteria such as Vibrio, Photobacterium fisheri

Contamination of fish comes from several sources Fishing tools Fishing tools, nets, boat decks and boxes in which fish are placed. Sellers Sellers with skin diseases such as boils and pimples containing Staphylococcus aureus or patients carrying Salmonella and Shigella bacteria 4 2 1 5 3 Marketing The water Marketing in unclean markets, vendors, and rudimentary sales methods The water in which the fish live, which may come from sewage residues and dead animals.

Spoilage of fish Fish spoil as a result of the following factors 1. Autolysis 2. As a result of oxidation 3. By the action of a microbial activity, often by the action of all three together. Autolysis: - The lytic enzymes reduce the compositional efficiency during the first stages of lyses resulting in production of hypoxanthine and formaldehyde . Among the enzymes that are released is cathepsin from the lysosome, leading to the degradation of proteins and peptides, also, digestive enzymes such as chemotrypsin and trypsin will release.

Spoilage of fish Oxidation: It is represented by oxidation of fats, which is very rapid and takes place in three stages 1. Initiation and at this stage free radicals are formed from fats and these free radicals combine with oxygen to be peroxyle radicals where oxygen interacts with the double bond of fatty acids, so fats consisting of unsaturated fatty acids are more susceptible to oxidation. 2. Propagation, and over this stage, peroxyle radicals interact with other lipid molecules to form hydroperoxide and new free radicals. 3. Termination, which occurs when new free radicals interact with each other to form nonradical products.

Spoilage of fish Microbial activity, |Fish spoiled faster than other meats because of the following reasons: 1. High humidity 2. Softness and texture 3. The speed of action of enzymes on such tissues 4. The acidity is less than that of other meats 5. Fish fat is faster in oxidation The most important species that cause fish spoilage are Pseudomonas, Acinitobacter, Moraxilla.

Spoilage of fish Spoiled fish can be distinguished from healthy fish by observing the following: 1. Spoiled fish loses its natural color and turns into a dark brown and yellow color. 2. Increased amount of sticky material on its surface, gills and fins. 3. The nostrils turned from red to gray, and the eyes sunken down. 4. The softness of the muscles because they are full of fluids. There are chemical methods for examining spoilage in fish, namely: 1. Measuring the amount of trimethylamine as a measure of fish spoilage, as the greater the amount of this substance, the greater the corruption. 2. Estimating the amount of volatile organic acid, or some other compounds formed as a result of corruption, such as hydrogen sulfide and ammonia.

Microorganisms that cause fish spoilage The manifestations of fish spoilage caused by microbiology are the following: 1. The slime layer appears. This layer contains mucopolysaccharide, tri methyl amine and free amino acids. 2. The emergence of different odors as a result of the release of volatile compounds. 3. formation of Tri methyl amine from tri methyl amine oxide. 4. Formation of histamine from histidine by the action of the enzyme decarboxylase

Microorganisms that cause fish spoilage The most important species responsible for fish spoilage is the Pseudomonas, which constitutes 90% of the coriander spoilage fish, as the type Ps. perolens causes fish spoilage, fruit aroma and Ps. fragi causes a musty and bacterial smell, Ps.putrefaciens, due to its ability proteolytic and putrefuction, and it can easily penetrate through the skin of the fish and cause corruption and the appearance of the smell of onions or fruits. In general, proteolytic bacteria are the ones that predominate in fish, causing protein decomposition and rotting, producing moldy substances such as hydrogen sulfide and ammonia and sulfur amino acids such as methionine, cystine, cysteine.