Tuesday, July 20, 2010
MSc FOOD SCIENCE
St. Mary’s College for Women, Paliakara, Thiruvalla-689 101 (2002) Tel: 0469-2606560,0469-2600710 Fax:0469-2734710 Web: www.stmaryscw.com E-mail: stmarycw@rediffmail.com Principal:Prof:Prasad Thomas Kodiyatt Tel: 0469- 2603932 (R)
Thursday, September 24, 2009
Brandy
The name brandy comes from the Dutch word brandewijn, meaning "burnt wine." The name is apt as most brandies are made by applying heat, originally from open flames, to wine. The heat drives out and concentrates the alcohol naturally present in the wine. Because alcohol has a lower boiling point (172°F, 78°C) than water (212'F, 100°C), it can be boiled off while the water portion of the wine remains in the still. Heating a liquid to separate components with different boiling points is called heat distillation. While brandies are usually made from wine or other fermented fruit juices, it can be distilled from any liquid that contains sugar. All that is required is that the liquid be allowed to ferment and that the resulting mildly-alcoholic product not be heated past the boiling point of water. The low-boiling point liquids distilled from wine include almost all of the alcohol, a small amount of water, and many of the wine's organic chemicals. It is these chemicals that give brandy its taste and aroma.
Almost every people have their own national brandy, many of which are not made from wine: grappa in Italy is made from grape skins, slivivitz in Poland is made from plums, shochu in Japan is made from rice, and bourbon in the United States is made from corn. Beer brandy is better known as Scotch whiskey. It is universally acknowledged that the finest brandies are the French cognacs that are distilled from wine.
Brandies are easy to manufacture. A fermented liquid is boiled at a temperature between the boiling point of ethyl alcohol and the boiling point of water. The resulting vapors are collected and cooled. The cooled vapors contain most of the alcohol from the original liquid along with some of its water. To drive out more of the water, always saving the alcohol, the distillation process can be repeated several times depending on the alcohol content desired. This process is used to produce both fine and mass-produced brandy, though the final products are dramatically different.
History
It is unknown when people discovered that food could be converted to alcohol through fermentation. It appears that the discovery of fermentation occurred simultaneously with the rise of the first civilizations, which may not be a coincidence. At about the same time that people in Europe discovered that apple and grape juice—both containing fructose—would ferment into hard cider and wine, people in the Middle East discovered that grains—which contain maltose—would naturally ferment into beer, and people in Asia discovered that horse milk—containing lactose—would naturally ferment into airag. The first distilled liquor may in fact have been horse milk brandy, with the alcohol separated from fermented horses' milk by freezing out the water during the harsh Mongolian winter.
It is also not known when it was discovered that the alcohol in fermented liquids could be concentrated by heat distillation. Distilled spirits were made in India as long ago as 800 B.C. The Arabic scientist Jabir ibn Hayyan, known as Geber in the West, described distillation in detail in the eighth century. Regardless of its origin, alcohol was immensely important in the ancient world. In Latin, brandy is known as aqua vitae, which translates as "water of life." The French still refer to brandy as eau de vie meaning exactly the same thing. The word whiskey comes from the Gaelic phrase uisge beatha also meaning water of life. People in the Middle Ages attributed magical, medicinal properties to distilled spirits, recommending it as a cure for almost every health problem.
Raw Materials
The raw materials used in brandy production are liquids that contain any form of sugar. French brandies are made from the wine of the St. Émillion, Colombard (or Folle Blanche) grapes. However, anything that will ferment can be distilled and turned into a brandy. Grapes, apples, blackberries, sugar cane, honey, milk, rice, wheat, corn, potatoes, and rye are all commonly fermented and distilled. In a time of shortage, desperate people will substitute anything to have access to alcohol. During World War II, people in London made wine out of cabbage leaves and carrot peels, which they subsequently distilled to produce what must have been a truly vile form of brandy.
Heat, used to warm the stills, is the other main raw material required for brandy production. In France, the stills are usually heated with natural gas. During the Middle Ages it would have required about 20 ft4 of wood (0.6 m4) to produce 25 gal (100 l) of brandy.
The ManufacturingProcess
The fine brandy maker's objective is to capture the alcohol and agreeable aromas of the underlying fruit, and leave all of the off-tastes and bitter chemicals behind in the waste water. Making fine brandy is an art that balances the requirement to remove the undesirable flavors with the necessity of preserving the character of the underlying fruit. Mass-produced brandies can be made out of anything as the intent of the people is to remove all of the flavors, both good or bad, and produce nothing but alcohol—taste is added later. Fine brandies are required to retain the concentrated flavor of the underlying fruit.
A demonstration against Prohibition.
The Eighteenth Amendment made it a crime to make, sell, transport, import, or export liquor. It is the only amendment to be repealed by another (the Twenty-first). The Prohibition era (1920-1933) had been a long time in coming. From the mid-nineteenth century through the beginning of World War I, a growing movement demanded a prohibition on alcohol. When members of Congress finally bowed to pressure from prohibition supporters and passed a constitutional amendment, many did so under the belief that it would not be endorsed by the states. In fact, a clause was added to make it more likely not be sanctioned: if three-quarters of the states did not ratify the amendment before seven years had expired, it would be deemed inoperative.
The amendment was passed by Congress in December 1917 and ratified by three-quarters of the states by January 1919. The popularity of the amendment disappeared soon after it was put into effect. The Volstead Act of 1919 banned beer and wine, something few people had anticipated, and in the minds of many Prohibition became a mistake. Crime rose as gangsters took advantage of the ban on alcohol by making huge profits in bootlegging and smuggling. When Franklin D. Roosevelt campaigned for president in 1932, he called for the repeal of Prohibition. His opponent, President Herbert Hoover, called it "an experiment noble in motive." Roosevelt won the election and his Democratic party won control of the government. Within months the Eighteenth Amendment was repealed.
Fine brandy
1. The first step in making fine brandies is to allow the fruit juice (typically grape) to ferment. This usually means placing the juice, or must as it is known in the distilling trade, in a large vat at 68-77°F (20-25°C) and leaving it for five days. During this period, natural yeast present in the distillery environment will ferment the sugar present in the must into alcohol and carbon dioxide. The white wine grapes used for most fine brandy usually ferment to an alcohol content of around 10%.
2. Fine brandies are always made in small batches using pot stills. A pot still is simply a large pot, usually made out of copper, with a bulbous top.
3. The pot still is heated to the point where the fermented liquid reaches the boiling point of alcohol. The alcohol vapors, which contain a large amount of water vapor, rise in the still into the bulbous top.
4. The vapors are funneled from the pot still through a bent pipe to a condenser where the vapors are chilled, condensing the vapors back to a liquid with a much higher alcohol content. The purpose of the bulbous top and bent pipe is to allow undesirable compounds to condense and fall back into the still. Thus, these elements do not end up in the final product.
5. Most fine brandy makers double distill their brandy, meaning they concentrate the alcohol twice. It takes about 9 gal (34 1) of wine to make I gal (3.8 1) of brandy. After the first distillation, which takes about eight hours, 3,500 gal (13,249 1) of wine have been converted to about 1,200 gal (4,542 1) of concentrated liquid (not yet brandy) with an alcohol content of 26-32%. The French limit the second distillation (la bonne chauffe) to batches of 660 gal (2,498 1). The product of the second distillation has an alcohol content of around 72%. The higher the alcohol content the more neutral (tasteless) the brandy will be. The lower the alcohol content, the more of the underlying flavors will remain in the brandy, but there is a much greater chance that off flavors will also make their way into the final product.
6. The brandy is not yet ready to drink after the second distillation. It must first be placed in oak casks and allowed to age, an important step in the production process. Most brandy consumed today, even fine brandy, is less than six years old. However, some fine brandies are more than 50 years old. As the brandy ages, it absorbs flavors from the oak while its own structure softens, becoming less astringent. Through evaporation, brandy will lose about 1% of its alcohol per year for the first 50 years or so it is "on oak."
7. Fine brandy can be ready for bottling after two years, some after six years, and some not for decades. Some French cognacs are alleged to be from the time of Napoleon. However, these claims are unlikely to be true. A ploy used by the cognac makers is to continually remove 90% of the cognac from an old barrel and then refill it with younger brandy. It does not take many repetitions of this tactic to dilute any trace of the Napoleonic-age brandy.
8. Fine brandies are usually blended from many different barrels over a number of vintages. Some cognacs can contain brandy from up to a 100 different barrels. Because most brandies have not spent 50 years in the barrel, which would naturally reduce their alcohol contents to the traditional 40%, the blends are diluted with distilled water until they reach the proper alcohol content. Sugar, to simulate age in young brandies, is added along with a little caramel to obtain a uniform color consistency across the entire production run. The resulting product can cost anywhere from $25 to $500 or even more for very rare brandy.
Mass-produced brandy
1. Mass-produced brandy, other than having the same alcohol content, has very little in common with fine brandy. Both start with wine, though the mass-produced brandies are likely to be made from table grape varieties like the Thompson Seedless rather than from fine wine grapes. Instead of the painstaking double distillation in small batches, mass-produced brandies are made via fractional distillation in column stills. Column stills are sometimes called continuous stills as raw material is continuously poured into the top while the final product and wastes continuously come out of the side and bottom.
2. A column still is about 30-ft (9-m) high and contains a series of horizontal, hollow baffles that are interconnected. Hot wine is poured into the top of the column while steam is run through the hollow baffles; the steam and wine do not mix directly. The alcohol and other low boiling point liquids in the wine evaporate. The vapors rise while the non-alcoholic liquids fall. As the still is cooler at the top, the rising vapors eventually get to a part of the still where they will condense, each type of vapor at a temperature just above its own boiling point.
The distillation of brandy.
3. Once they have recondensed, the liquids begin to move downward in the still. As they fall, they boil again. This process of boiling and condensing, rising and falling, happens over and over again in the column. The various components of the wine fraction and collect in the column where the temperature is just below the boiling point of that component. This allows the ethyl alcohol condensate to be bled out of the column at the height where it collects. The resulting product is a pure spirit, colorless, odorless, and tasteless, with an alcohol content of about 96.5%. At 96.5% alcohol, it can be used to fuel automobiles. It can be diluted and called vodka or diluted and flavored with juniper berries and called gin.
4. Mass-produced brandies are also aged in oak casks and pick up some flavors from them. Like its fine counterpart, the brandies are blended, diluted to around 40% alcohol, and bottled.
Quality Control
The quality control process for fine brandies involves trained tasters with years of experience sampling brandy. A large cognac house might have 10,000 barrels of brandy in its cellars, each of which must be tasted annually. Hence, most of the brandy "tasting" involves only smelling, as tasting several hundred barrels of brandy in a day would result in alcohol poisoning. The tasters usually "taste" each of the barrels at least once a year to assess how it is aging and to evaluate it for its blending qualities. Brandies that pick up off-flavors during distillation are discarded.
As mass-produced brandies are manufactured to be odorless and tasteless, the only real quality control required is to check their alcohol content. Because alcohol is less dense than water, the alcohol content of brandy can be checked with a hydrometer. A hydrometer is a glass float with a rod sticking out the top of it. The rod is calibrated so that a line on the rod will be exactly at the liquid surface if the hydrometer is floating in water. As alcohol is less dense than water, the hydrometer will sink deeper in alcohol than it will in water. By calibrating the rod scale with different blends of known alcohol content, it can be used to determine the percentage of alcohol in a water/alcohol mixture.
Byproducts/Waste
The waste products from brandy production include the solids from the wine production and the liquids left over from the still. The solids from brandy production can be used for animal feed or be composted. The liquid wastes are usually allowed to evaporate in shallow ponds. This allows the residual alcohol in the waste to go into the atmosphere, but the United States Environmental Protection Agency does not consider this to be a major pollutant source.
The Future
For the foreseeable future, the vast bulk of all the brandies will be produced in column stills. However, there is an increasing interest in luxury goods throughout the world. Not just fine brandies, but Calvados (fine apple brandy) and slivovitz (fine plum brandy) are getting increasing amounts of attention from collectors and ordinary citizens.
Sunday, September 6, 2009
GMP
According to FDA, GMP is defined as the sanitary & processing requirements of food companies. They are broad and general and used as a guide for the development of SOPs which are very specific. GMPs belong in every food quality control system. The Code of Federal Regulations provides excellent definitions &criteria which determine if the product has been manufactured under conditions which make it unfit for food;or if the product has been processed under insanitary conditions resulting in contamination with filth;or is otherwise rendered injurious to health. Since sampling product will statistically only ensure that the samples themselves are suitable for use, and end-point testing relies on sampling, GMP takes the holistic approach of regulating the manufacturing and laboratory testing environment itself. An extremely important part of GMP is documentation of every aspect of the process, activities, and operations involved with drug and medical device manufacture. If the documentation showing how the product was made and tested is not correct and in order, then the product does not meet the required specification and is considered contaminated
Additionally, GMP requires that all manufacturing and testing equipment has been qualified as suitable for use, and that all operational methodologies and procedures utilized in the drug manufacturing process have been validated (according to predetermined specifications), to demonstrate that they can perform their purported functions.
Other 'Good Practice' systems, along the same lines as GMP, exist:Good Laboratory Practice (GLP)for laboratories conducting non-clinical studies (toxicology and pharmacology studies in animals); Good Clinical Practice' (GCP)for hospitals and clinicians conducting clinical studies on new drugs in humans; Good Regulatory Practice (GRP) for the management of regulatory commitments, procedures and documentation.
CFR contains detailed requirements for avoiding these possibilities in the following areas:
n PERSONNEL
n PLANT AND GROUNDS
n SANITARY OPERATIONS
n SANITARY FACILITIES AND CONTROLS
n EQUIPMENT AND UTENSILS
n PROCESSES AND CONTROLS
n MANUFACTURING OPERATIONS
n WARE HOUSING AND DISTRIBUTION
PERSONNEL
n Disease control
n Cleanliness
n Education and training
n Supervision
PLANT AND GROUNDS
n Proper equipment storage
n Maintenance of surrounding property
n Effective systems for waste disposal
n Space for equipment placement and storage of materials
n Seperation of operations likely to cause contamination
n Sanitation precautions for outside fermentation vessels
n Building construction to permit adequate cleaning,adequate lighting,ventilation and screening.
SANITARY OPERATIONS
n BUILDING AND FIXTURES
Maintenance,cleaning and sanitizing to prevent contamination.Special precautions for toxic sanitizing agents
n PEST CONTROL
n FOOD CONTACT SURFACES:Sanitary procedures.
SANITARY FACILITIES AND CONTROLS
n Water supply
n Plumbing
n Sewage disposal
n Toilet facilities
n Handwashing facilities
n Rubbish and offal disposal
EQUIPMENT AND UTENSILS
n Design,materials and workmanship shall be cleanable
n Protected against contamination
n Non toxic
n Seamless
n Properly maintained
PROCESSES AND CONTROLS
n Adequate sanitation in receiving
inspection,transporting,segregating,
manufacturing,packaging and storing
n Appropriate quality control operations to ensure that food is suitable for human consumption and that packaging operations are unsafe and suitable
n Chemical, microbial and extraneous material testing
n Rejection of adulterated or contaminated material.
RAW MATERIALS
n Shall be inspected for suitability for processing into food.
n Stored to minimize deterioration
n Wash and conveying water to be adequate
sanitary quality
n Containers shall be processed for possible contamination or deterioration of food.
n Microorganisms presence shall not be at a level which might produce food poisoning ,and shall be pasteurized during manufacturing to maintain a safe level.
n Levels of toxins (like aflatoxins),or presence of pest contamination or extraneous material to be in compliance with FDA regulations
n Storage of raw materials,ingredients or rework shall be protected against contamination &held at a temperature and humidity which will prevent adulteration
n Frozen raw materials shall be thawed only as required prior to use and protected from adulteration.
MANUFACTURING OPERATIONS
n Equipment,utensils and finished food containers to be sanitized as necessary
n Manufacturing,packaging and storage to be controlled for minimum contamination
n Growth of undesirable organisms shall be prevented by refrigeration,freezing,sterilising,irradiating,water activity control..
n Protection against inclusion of metals or other extraneous materials shall be effective
n Adulterated food,ingredients or raw materials shall segregated and if reconditioned,shall be proven to be effectively free from adulteraion
n Mechanical manufacturing steps such as peeling,trimming,washing,cutting,cooling,inspectingetc shall be performed without contamination
n Preparation of batters,breading,sauces,gravies,dressings and similar preparations shall be prepared without contamination by effective means.
n Compliance may be accomplished by a quality control operation in which CCPs are identified and controlled during operation;all food contact surfaces are cleaned and sanitized;all materials used are safe and suitable;physical protection from contamination.
WAREHOUSING AND DISTRIBUTION
n Storage and transportation of finished foods shall be protected against physical,chemical and microbial contamination as well as deterioration of the food and the container
CONCLUSION
It shall be noted that the FDA regulations for GMP is modified from time to time and it is necessary to review quality control proceduresto ensure compliance
Tuesday, July 21, 2009
microbiological tests in spice industry
MICROBIOLOGY
Microbial infections of concern with respect to spices:
1. Bacterial infections of concern with respect to spices.
v Highest health hazard
• Salmonella typhi
• E.coli (pathogenic)
v Moderate health hazard
•Clostridium botulinum
• Bacillus cereus
• Other salmonella
2. Microbial intoxications
v Bacterial
• Bacillus cereus
• Staphylococcus aureus
• Clostridium botulinum
v Fungal
• Mycotoxins namely aflatoxins
Determination:
• Aerobic mesophilic bacterial count
• Yeast and mold count
• Indicators bacterial count the coliforms.
General procedures for microbial quality assessment:
ENUMERATION:
•Preparation of food homogenate
•Preparation of dilution
•Dispensing of required inoculums into
Petri plates
•Mixing with appropriate agar medium for
preparation of the gel.
•Incubation of plates
•Counting of colonies and interpretation
DETECTION:
•Enrichment with specific growth
Medium
•Plating on selective agar medium
•Detection of particular bacterial colony
on plates
•Biochemical conformation
•Serological conformation
VIBRIO CHOLARAE
MEDIUM:
1) Alkaline peptone water
2) TCBS agar
PROCEDURE:
Prepare 225ml alkaline peptone water, 25g sample is added to it. The solution is incubating 6 hours at 37°C. The prepared solution is loop to TCBS agar in petri plate and incubates 24 hours at 37°C. After incubation observe the growth of yellow colony.
SALMONELLA
DETECTION & IDENTIFICATION
INTRODUCTION:
Salmonella are gram negative nonsporing, facultative anaerobes that belong to the family enterobacteria. They are usually motive and produce both acid and gas from glucose. This rod- shaped bacteria is of important because it can cause food borne salmonellas (food poisoning) over 2,300 servers have been indentified and are distinguished according to their antigenic stricture. A wide variety of foods have been involved in food borne salmonellas, however, egg, poultry , meat and products have been the main vehicles.
SCOPE:
This method is applicable to processed and unprocessed foods and environmental samples. Only the pre-enrichment protocols ground and whole spices and herbs fruits, vegetables, seasoning blends, cheese, cheese bread, flour, flour based blends, onion, garlic & liquid whole eggs have been outlined. Salmonella is pathogen. It is imperative that standard laboratory safely practices be followed. Handle all inoculated media as bio-hazard materials
MEDIUM:
TSB
RV
TTB
XLD
BSA
HEA
TSI
LIA
SALMONELLA CONVENTIONAL
Pre enrichment (225ml/RSB, 25g
sample kept room temperature
for the (60+/5) 18-24 hr incubation)
RV (0.1 sample – 10 ml media) TTB (1 ml sample)
Enrichment
Selective media
TSI, LIA media
Glucose Lysine Bio chemical identification (IMVIC Test)
XLD:
Suspect colonies are pink or red with or without black center of completely black, same atypical colonies are yellow with or without black center and should be picked for confirmation.
BSA:
Suspect colonies are dark brown, gray or block usually with surrounding black 30 ml and metallic sheet with little or nor darkening of the surrounding medium, same a typical colonies are green with little or nor darkening of the surrounding medium should be picker for confirmation.
HEA:
Suspect colonies are blue green with or without black centers or completely black, same typical colonies are yellow with or without black centers and should be picked for confirmation.
BIOCHEMICAL IDENTIFICATION:
SUBJECT:
IMVIC Test
INTRODUCTION:
An important group of tests to distinguish between the coliform bacteria as well as other organisms in the family enterobacteriaceae is known by the acronym
IMVIC, these tests determine whether an organism has the ability to produce:
a) Indole from tryptophan (I)
b) Sufficient acid to reduce the medium ph to below 4.4, the point of the indicator methyl red (M)
c) Acetoin (acetyl methyl carbind-voges proskaner)
d) The ability to and utilize citrate (C)
These tests may be used for the bio chemical conformation of E. coli as well as acid in the identification if the rapid.
SCOPE:
This method is applicable to all microbiological laboratories.
VIDAS- SALMONELLA (SLM):
VIDAS Salmonella is an automated quantitative test for use on the VIDAS instruments, for the detection of salmonella in food and environmental specimens, using the ELRA technique (Enzyme Linked Fluorescent Assay).
PRINCIPLE:
VIDAS salmonella is an enzyme immune assay for use on the automated VIDAS system for the detection of salmonella antigens using the ELFA. This solid phase Receptacle (SPR) serves as the solid phase as well as the pipetting device the interior of the SPR is coated with anti-salmonella antibodies soaked and pre-dispensed in the sealed reagent strips.
TECRA-SALMONELLA:
225ml mpw + 25g sample
¯ 16-20 hours incubation
Loading to kit (wells)
VIDAS (Vital Immune Diagnostic Assay System)
225ml BPW + 25 g sample (18-24 hours at 36°)
¯
1ml 0.1ml
TTB RV media (6-8 hr incubation)
1 ml
¯
m broth (post enrichment) 42-2°C
incubation (18-24 hrs)
¯
1ml +1ml 1ml -15 boiling water
then cool
T-tube
(95+100°c) ¯
VIDAS ®loading 0.5 ml to vidas
¯
XLD, BSA to confirm
All of the assay steps are performed automatically by the instrument. The reaction media is cycled in and out of the SPR several times.
Part of the enrichment broth is dispensed into the reagent strip. The antigen present will bind to the anti-salmonella are during the washing antibodies coating the inferior of the SPR. Unbound components are eliminated during the washing steps. Antibodies conjugated with alkaline phosphate are cycled in and out of the SPR and will bind to any salmonella antigens which are themselves bound to the antibodies on the SPR. A final wash step removes unbound conjugate. During the final detection step, the substrate (4methyl-umbelliferone) the fluorescence of which is measured at 450nm.
At the end of the assay, results are automatically analyzed by the instruments which is calculated a test value for each sample. This value is then compared to internal reference and each result is interpreted (positive, negative).
TUBE MOST PROBABLE NUMBER (MPN) COLIFORM,
FECAL COLIFORM, AND E. COLI DETERMINATION:
INTRODUCTION:
In general, coli form bacteria are represented by 4 genera of the family Enterobacteriaceae, Escherichia, Enterobacter.
They are gram negative, rod-shaped micro organisms that are commonly found in nature and the intestinal tract of animal humans. They have the capacity to ferment lactose with the production of gas and are able to grow in the presence of bile salts. Because of the genera case with which coli forms can be cultivated and differentiated they are used as indicator organisms to assess food safety and sanitation.
The modified to grow and on the ability of fecal coli forms to grow and produce bas at 45-5c in a lactose broth media. Escherichia coli are the coliform of most concern because its presence in food indicted fecal contamination or unsanitary practices during or after production.
SCOPE:
This is the traditional method for enumerating total coli forms, fecal coli forms and E. coli in foods.
DETERMINATION OF E. coli:
MEDIUM:
§ LSB medium
§ EC Broth
§ EMB agar
§ Macon key agar
PROCRDURE:
MPN coli form, fecal coli form, and E. coli determination:
Prepare sample dilutions. Using a sterile 10ml pipette, transfer 10.0 ml of the 10-1 dilution into three tubes of double strength. Lauryl sulfate broth. This is equivalent to a 10° dilution. Using a sterile 1 or 2.0 ml pipette and working from the highest dilution to the lowest, transfer 1ml of each dilution into each of three tubes of single strength Lauryl sulphate broth. By working from the separate one for each dilution must be employed. Incubate the tubes at 35°C for 48±2 hours. A tube is presumptively positive if there is effervescence when the tube is gently agitated. Confirm each presumptively positive lauryl sulfate tube by transferring a loop full of the broth into a tube of brilliant green bile broth and into a tube of EC broth. Incubate the Brilliat green Bile tubes at 35±1°c for 48±2 hours and incubate the EC broth tubes in a 45.5±-021° water bath for 48±-2 hours. Production of gas in the BGB tubes incubate, confirmed coli form bacteria. Record the number of positive tubes for each dilution.
Tubes evidencing gas production in EC broth are considered positive for fecal coli forms. Record the number of positive tubes for each dilution. To confirm the presence of E. coli in EC positive tubes, streak Levine EMB agar plates with a loop full of broth from each positive tube of EC broth incubate for 24±-2 hours at 35 ±-1°C
After incubation, examine the plates for typical E. coli: colonies: small, wine colored with or without a gram metallic sheath.
STANDARD PLATE COUNT DETERMINATION:
INTRODUCTION:
The standard plate count or total plate count enumerates viable mesophilic aerobes capable of growth on designated media. the method which is highly empirical, is based on the assumption organism. The standard plate count method or aerobic plate count is one of major application of the colony count method. These procedures are based on the assumption that each microbial cell in a sample will form a visible, separate colony when mixed with an agar or other solid medium and permitted to grow. The microorganism found in foods, often represent the number of population with many growth requirements, it can be possible that some organism may not be able to grow under conditions employed consequently, the counts are, at best, an estimate and should not be reported as absolute.
SCOPE:
This method is applicable to all foods standard plate count aerobic mesophilic
MEDIUM-TPC (total plate count agar):
Prepare the buffer solution (make up 34 g phosphate buffer in 1000ml water). Take 100ml to each bottle. This solution is mix well in ‘8’ shaped 25 times. Take clean and sterilized Petri dishes and 1ml mixed solution is poured into the sample. The sample is then mixed clock wise and anticlockwise and up and down manner. It is then stand for setting the solution. Then incubate at 37°C for 48 hour. After two days observe the growth. The PH range is between 7.0 ± 2.
YEAST AND MOLD DETERMINATION:
MEDIUM:
PDA (Potato dextrose agar)
INTRODUCTION:
Both yeast and mold cause varying degrees of deterioration and decomposition of foods. The ability of fungi to spoil many foods is due to part to their relatively versatile environment requirement.
PROCEDURE:
Prepare the buffer solution. Take 100ml to each bottle. This solution is mix well in ‘8’ shaped for 25 times. Take clean and sterilized Petri dishes and 1ml mixed solutions poured into the Petri dishes. Prepared PDA media poured into the sample. The sample is then mixed clockwise and anticlockwise and up and down manner. It is then stand for few minutes on laminar air flow bench for 3-5 days. After five days count the number of yeast and mold.