Spoilage of Dairy, and Fish Products  Of all foods, dairy, meat and fish products are more vulnerable for microbial growth  High nutrient content  High level of simple nutrients  Favorable pH  High water activity  Absence of antimicrobial factors

FT 5105 Food Microbiology 2  The quality and safety of milk, dairy, meat and fish products are of primary concern in the industry  30 million cases of foodborne diseases are reported each year in the U.S. at a cost of $5-8 billion annually and 900 fatalities.  The incidence rate in Canada is estimated at 2.2 million cases per year at a cost of $ 1-3 billion annually.

FT 5105 Food Microbiology 3 Common foodborne pathogens in dairy

 Salomnella typhimarium  typhi  Camphylobactor  E coli (verotoxigenic)  Listeria monocytogenes

FT 5105 Food Microbiology 4 Dairy Products

 Milk is very nutritious  Fresh milk contains MOs of a large variation  The type and number depend on the hygienic conditions of the dairy farm, cleanliness of utensils etc.  Milk contains lactoperoxidase and agglutinins but not effective

5 Point of sampling Range (SPC/mL)

Aseptically drawn milk 500-1000

Milk pail/machine 1000-10,000

Bulk tank 5000-20,000

6 Diseases potentially arises from contaminated milk

 Tuberculosis  Diphtheria  Scarlet fever 

 Mycobacterium paratuberculosis  post-pasteurization contamination  This may be as a result of cross- contamination of finished product with raw product, inadequate sanitation procedures in the plant environment, or inadequately sanitized equipment.

FT 5105 Food Microbiology 8  Commonly found spoilage in milk  Enterococcus Lactococcus  Leuconostoc  Lactobacillus Microbacterium  Propionibacterium Proteus  Pseudomonas  Upon pasteurization all Mos are destroyed except thermodurics (Micrococci, Enterococci, Lactobacilli and Sterptococci), spore formers of Bacillus group and spores  72C for 15 sec. may go up to 79 for 25 sec.  Pasteurized milk is spoilt by heat resistant Streptococci that utilize lactose

9

 They produce lactic acid which brings pH down to 4.5 thus, leading to curdling  can grow on the surface bringing pH up to neutrality  Thus, proteolytic type bacteria can start growing  Proteolytic Pseuodomonas can quickly grow and liquefy curdle

10 Raw Milk

 Milk spoilage Sourness Flavor changes Curdling Color changes Gas formation Fermentaiton

11  Sourness is developed and thus pH decreases  Curdling happens and then whey is released  Lactic acid formation is the major cause  Raw milk held at 10-37 is more likely to be fermented by Streptococcus lactis  In addition Colifirms, Enterococci, 12 Lactobacilli and Micrococci also contribute • 37-50C • Sterptococcus thermophillus and S. faecalis • Little acid is formed at elevated temperatures

• Gas production (hydrogen and carbon dioxide) is carried out by Clostridia • Gas production is evidenced by frothing on top • Proteolysis is favored at low temperatures

13

 Proteolysis 1. Acid proteolysis 2. Proteolysis with little acidity 3. Sweet curdling

14 Ropiness (Sliminess) in Milk

 Bacterial and non-bacterial  Bacterial sliminess is due to the slimy capsular materials from cells (gums and mucins)  Developed mostly at low temperature  Caused by Alcaligenes viscolactis  This is favored by low holding temperatures 15 1. Surface ropiness Alcaligenes viscolactis Grows best at 10C and Micrococcus spp.

2. Ropiness throughout and Klebsiella oxytoca, Enterobacter cloacae

 Alkaline producers  Pseudomonas fluorescens and A. viscolactis 16  Hydrolysis  Color changes  Blue milk  Yellow milk  Red milk  Brown milk

17 Flavor changes

• Cheesiness • Rancid • Beany • Musty • Flat flavor • Unclean • Malty • yeasty

18  Foods can be categorized into 3 groups on the basis of spoilage Stable – nonperishables – sugar, flour, dry seeds, cereals Semiperishable foods – potatoes, nuts Perishable foods – , fish, poultry, eggs, dairy etc.

FT 5105 Food Microbiology 19 Spoilage can happen due to

 Growth and activity of MO  Damages due to insects  Physical damages  Enzymic action  Non-enzymatic chemical reactions  Physical changes due to freezing, burning drying, high temperature etc.

FT 5105 Food Microbiology 20  Number and type of MO in a food depend on Source – where the food is originated Microbial quality of raw materials Sanitary conditions under which food is handled/processed Subsequent packaging/handling/storage  Inner parts of plant or animal tissues are sterile  Contaminations are most likely to happen

FT 5105 Food Microbiology 21  Thus, the microbial number in a fresh product reflects the quality of it  Therefore SPC is an important criterion in determining the quality of a fresh product

FT 5105 Food Microbiology 22 Spoilage of Meat and Meat Products

FT 5105 Food Microbiology 23 Composition of Meat

Constituent Percentage water 75 Protein 19 Lipids 2.5 CHO 1.2 Soluble NPN 1.65 Minerals 0.65

FT 5105 Food Microbiology 24  Tissues of healthy animal are relatively free of MOs  Microbial count of freshly slaughtered animal tissues is less than 10 cfu/Kg  Most contaminated areas of animal body are hide and GIT  Number and type of MOs depend on the envt. The animal lived

FT 5105 Food Microbiology 25  Animal hide contains Micrococci Staphylococci Pseudomonas  and molds  Viscera contains large no. of MOs including pathogens  Surface microbial count goes up to 102- 104/Cm2  Generally lamb and pork contains more MOs than beef

FT 5105 Food Microbiology 26  Skinning is not usually done with poultry  Thus, skin MOs are not removed  GIT of poultry too contain very high no. of MOs and pathogens such as Salmonella and Campylobacter

FT 5105 Food Microbiology 27 Common Genera of Bacteria Found in Meats Genus Fresh Vacu. Poultry Sea food Acenetobacter Aeromonas Alcaligenes Bacillus Brocathrix Carnobacterium Corynebacterium Enterobacter Enterococcus

FT 5105 Food Microbiology 28 Genus Fresh Vacu. Poultry Sea food Escherichia Flavobacterium Lactobacillus Listeria Micrococcus Moraxella Pseudomonas Psychrobacter Shewanella Salmonella

FT 5105 Food Microbiology 29 Genus Fresh Vacu. Poultry Sea food Staphylococcus Vibrio

FT 5105 Food Microbiology 30 Common Molds in Meats Genus Fresh Poultry Proces Fish & sed Seafood Alternaria Aspergillus Botrytis Cladosporium Fusarium Geotrichum Mucor Penicillium Rhizopus Thamnidium FT 5105 Food Microbiology 31  Comminuted meats contain more MOs Ground meat contains trimmings Higher surface area – most spoilage MOS are aerobic Handled many times – contaminated blades, saws, utensils One heavily contaminated piece can inoculate the whole lot  Organ meats such as kidney, liver, tongue, heart contain less MO

FT 5105 Food Microbiology 32  MOs in Vacuum packaged meat – mainly Pseudomonas  Oxygen permeability determines the refrigerated storage life  The higher the permeability the lesser the storage life  When permeability is very low CO2 concentration goes up and this favors LABs an Brochothrix

FT 5105 Food Microbiology 33  Common bacteria in vacuum packaged meats Streptococci Bacillus Micrococci Moraxella Acinetobactor Pseudomonas

FT 5105 Food Microbiology 34 Spoilage  Most common indications of spoilage are Off odor and slimy surface due to the action of aerobic bacteria on the cut surfaces Fungal growth favored at water activity low for bacterial growth Bone taint = deep spoilage due to anaerobic or facultative MOs Discolorations due to change of myoglobin color

FT 5105 Food Microbiology 35 A. Under aerobic conditions  Bacteria Surface slime Changes in meat color Changes in fat Off odors and off tastes  Yeasts Sliminess Lipolysis, off odors and tastes White, cream-pink, brown colors due to pigments

FT 5105 Food Microbiology 36  Molds Stickiness Whiskers – Thamnidium, Mucor and Rhizopus Black spots - Cladosporium White spots – Chrysoporium Green patches – Penicillium  of fats, off odors and tastes

FT 5105 Food Microbiology 37  Under anaerobic conditions Souring Putrefaction – production of foul smell under anaerobic conditions – hydrogen sulfide, mercaptans, indole, skatole, ammonia, amines.  When meat is stored in refrigerated conditions psychropilic and psychrotropic MOs attack Sliminess Discolorations & souring

FT 5105 Food Microbiology 38  Alcaligenes  Lactobacillus  Leuconostoc Mainly responsible MOs  Streptococcus  Flavobaterium

FT 5105 Food Microbiology 39  Molds do not grow on meats at temperatures less than -5C  Candida and Rhodotorula are partly responsible for spoilage of refrigerated meat  Ground meat is exclusively spoilt by bacteria Pseudomonas Acinetobacter

FT 5105 Food Microbiology 40 Growth of MO on meat

 1. Type and quantity of MO E.g. If psychrotroph population is high very high chance of spoilage under chilling conditions  2. Physical properties of meat The quantity of meat exposed to air has a great influence

FT 5105 Food Microbiology 41 Mincing of meat greatly increases spoilage Mincing increases aeration, distribute Mos throughout the mixture and releases moisture from tissues 3. Chemical properties of meat pH Moisture content – surface may go dry - this will promote growth

FT 5105 Food Microbiology 42 Low in CHO thus non fermenting Mos grow well 4. Availability of oxygen Aerobic conditions favor mold and yeast growth on the surface True putrefaction is favored by anaerobic conditions

FT 5105 Food Microbiology 43 5. Temperature Putrefaction is very low at low temperatures At room temperature mesophiles grow and produce moderate amounts of acids using limited quantities of CHO.

FT 5105 Food Microbiology 44 Types of Spoilage

 1. Surface Sliming Caused by Pseudomonas, Acinetobacter, Moraxella, Alcaligenes, Streptococcus, Leuconostoc, Bacillus and Micrococus In addition, some Lactobacilli too can produce Temperature and moisture mainly determine the type of MO

FT 5105 Food Microbiology 45 At chilling temperatures with high moisture – Pseudomonas and Alcaligenes Less moisture favors Micrococus  2. Color changes Red color may change to green/brown or gray Color change is mainly due to production of oxidizing compounds

FT 5105 Food Microbiology 46 Different colored spots are developed Red spot – Serratia marcenscens growing on surface Blue spots – Pseudomonas synscyaneae growing on surface Yellow coloration – Micrococcus

FT 5105 Food Microbiology 47 Greenish-blue or brownish black spots – Chromobacterium lividum Purple (stamping ink color) – discoloration by yellow pigmented cocci and rods due to discoloration of surface fat  Off odors and taste Called taints Sour odor is formed by acids

FT 5105 Food Microbiology 48 Leuconostoc, Heterofermentative Lactobacilli are mainly responsible  3. Changes in fat Unsaturated fatty acids undergo oxidation Hydrolysis Adds off flavors to meat

FT 5105 Food Microbiology 49

B – Under Anaerobic conditions

 1. Souring – due to Acetic, succinic, butyric, propionic and higher FAs  2. Putrefaction True putrefaction is due to decomposition of proteins under anaerobic conditions – produce foul smell – hydrogen sulfide, mercaptans, skatole. Ammonia and amines

FT 5105 Food Microbiology 50  Psuedomonas and Alcaligenes species are mainly responsible  Species ending with putrefaciens, putida, putrificum  Clostridium produces gases such as H and CO2

FT 5105 Food Microbiology 51  3. Taint development – Pseudomonas Acinetobacter Moraxella Alcaligenes Lactobacillus Leuconostoc, Streptococcus, Flavobacterium

FT 5105 Food Microbiology 52 Number of Mos at the time of appearance of odor and slime

Type When Odor is Slime is identifiable identifiable (X106/cm) (X106/cm)

Poultry 2.5-100 10-60 Beef 1.2-100 3-300 Frankfurters 100-130 130 Bacon 1.5 -100 Fish 1-130

FT 5105 Food Microbiology 53 Spoilage of fresh beef

 1. changes in hemoglobin and myoglobin  2. white, green, yellow and greenish blue or brown spots and purple discoloration  3. Phosphorescence –  4. Spots due to bacteria, yeasts and molds

FT 5105 Food Microbiology 54 Cured meat

 Curing selectively favor the growth of Lactic acid bacteria  Pathogens are destroyed

FT 5105 Food Microbiology 55 Sausages

 Bacterial growth in encased sausages is possible On the casing Between the casing and meat Interior meat  Greening is common in sausages

FT 5105 Food Microbiology 56  Greening is favored by slightly acidic pH and little oxygen  This happens 12-36 after production even under refrigerated conditions  Production of peroxides, mainly H2O2 is attributable

FT 5105 Food Microbiology 57  Lactobacillus and Leuconostoc and other catalase negative bacteria are responsible for peroxide production

FT 5105 Food Microbiology 58 Bacon

 Molds are common Aspergillus, Fusarium, Mucor, Rhizopus, Monilia, Oidium, Botrytis and Penicillium  Streptococcus faecalis – salt tolerant and can grow at low temperatures  Micrococcus can be present on surface

FT 5105 Food Microbiology 59 Sausage, Frankfurters, Bologna etc.

 Three major types  Souring – caused by Lactobacilli, Enterococci.  Sliminess – also known as slimy spoilage occurs on the outside of the casing  Greening – two types of greening can

occur by H2O2 and H2S

FT 5105 Food Microbiology 60  Greening due to H2O2 occurs mainly in frankfurters and other vacuum packaged meats  Generally appears after exposing anaerobically stored meat into air

 Upon exposure to air H2O2 is produced and it reacts with nitrosohemochrome  This produces green color oxidized porphyrin

FT 5105 Food Microbiology 61  Greening also occurs due to the

accumulation of H2O2 in the core where Redox potential is low.  Lactobacillus viridescens is the major causative agent

 H2S type greening occurs in fresh red meats held at 1-5C packed in vacuum packages

 H2S reacts with myoglobin to produce sulphmyoglobin

FT 5105 Food Microbiology 62

Microorganisms in cured meat

MO type Meat Salami Lactobacilli Bologna Leuconostoc mesenteroides , hetero Lactobacilli Pork (fresh) Leuconostoc, Lactobacillus, Pseudomonas Bacon Lactobacilli, Micrococcus Ham Lactobacilli, Micrococcus, Microbacterium

FT 5105 Food Microbiology 63 POULTRY  Poultry is mainly spoilt by Pseudomonas Acinetobacter Flavobacterium Corynebacterium  Fungi is less importance in poultry spoilage  Main symptom of poultry spoilage is sliminess on the surfaces and cut surfaces

FT 5105 Food Microbiology 64  Unlike meats in poultry spoilage is mainly restricted to the surface  The inner tissues do not contain high no. of Mos  Pseudomonas is the major spoilage organism which forms colonies on the surface which finally coalesce to form sliminess

FT 5105 Food Microbiology 65 Methods to Determine Meat Spoilage

 Measurement of

Mercaptans, H2S, TMA, tyrosine complexes Catalase, creatinine, hypoxanthine Lactic acid Change in color pH changes RI of meat juices Impedance

FT 5105 Food Microbiology 66 Bacteriological Methods

 Total aerobes  Total anaerobes  Ratio of aerobes to anaerobes

Extract Release Volume (ERV) This method is used to measure spoilage and potential shelf life

FT 5105 Food Microbiology 67  ERV is the volume of aq. Extract released by a homogenate of meat when allowed to pass through a filter paper

 Detection of foul odor due to H2S etc. happens only when amino acids are started to be utilized

FT 5105 Food Microbiology 68  Dark firm and dry meats (DFD) have high pH values (>6) are spoilt quicker than other meats  In vacuum packed meats – nitrites control Bacillus thermoscapta  Lactobacillus is insensitive to nitrites and thus they predominate

FT 5105 Food Microbiology 69 Spoilage of Fish and Shellfish

FT 5105 Food Microbiology 70  Fat is interspersed between muscle fibers  Little connective tissues  In non-fatty fish fat content is 0.5%  Fatty fish may contain from 3-25%  Contains 1% CHO

71  Like meat, fish and other sea foods are spoilt by Autolysis Oxidation and Microbial activity  Fish muscles are more quickly spoilt than meats due to higher enzyme activity Presence of highly unsaturated fats and Higher pH

72 Factors affecting fish spoilage

 Type of fish Flat fish spoil more rapidly than the round fish as flat fish undergo rigor mortis rapidly Fish with high content of PUFA undergo deterioration rapidly  Condition when caught Struggled, exhausted fish spoil faster Fish underwent lack of oxygen conditions

73

 Fish with the full gut contents are more perishable  The extent of contamination  Microbes come from water, mud, slime on the surface and gut contents  Gills are rich in MOs  The greater the microbial load the quicker the spoilage is

74  Spoilage might start in the net during transporting etc.

75 Microflora associated with fish

 Depends upon the environment they live in  They can be contaminated during catching, handling and storage  The slime is rich in Pseudomonas Alcaligenes Micrococcus Flavobacterium

76 Corynebacterim Serratia Vibrio Bacillus  Fish intestine is rich in Alcaligenes Pseudomonas Vibrio Bacillus Clostridium E coli

77

 Skin contains 102-107 cfu/cm2  Gills and guts 103 – 109 cfu/g  Most crucial factor in fish spoilage is temperature  Fish stored at 0C starts spoiling with a lag of 1-2 days  In fish spoilage the following microbes become dominant Pseudomonas Acinetobacter and Flavobacterium

78  As spoilage progresses the Pseudomonas population increases rapidly  The type of species changes with spoilage  When temperature is increased Pseudomonas population goes down and mesophilics start dominating  Trimethylamine oxide (TMAO) naturally present in fish is reduced to TMA  This is a volatile compound and

79 responsible for the fishy odor

 As spoilage progresses volatile bases, amines and organic acids are formed due to decarboxylaiton or deamination of amino acids  Hydrogen sulfide, mercaptans and disulfides are the main compounds producing the odor other than TMA  Spoilage organisms use TMAO, creatine, taurine, anserine and amino acids

80  Total volatile compounds include Total volatile bases (TVB) Total volatile acids (TVA) Total volatile nitrogen (TVN) Total volatile substances (TVS)  Fish odor is explained as a complex of Fishy stale

81 ◦ Musty ◦ Rancid ◦ Sour ◦ Ammonical ◦ Fruity and ◦ Acids

 Discoloration of fish leads to development of green and yellow colors  Pseudomonas fluorescens is mainly responsible

82  Histidine present in fish is converted to histamine by bacteria  Only bacteria that have decarboxylase enzymes can do the converion  Histamine is associated with scombroid poisoning

83 Indicators of Fish Spoilage

 Histamine  Cadaverine – a diamine  Putrescine – a diamine  Total volatile substances

84