1. Gene transfer techniques
In the laboratory, specific enzymes may be used to cut and splice DNA:
Restriction enzymes break DNA at specific parts of the molecule (nucleotide base sequences) - usually leaving so called "sticky ends".
This can be done to both DNA from which genes are being taken, and to DNA in which genes are being inserted. Then, DNA ligase enzymes may be used to rejoin such sections into the other DNA.
The DNA containing the selected gene for the desired characteristic may then be inserted into cells of the target organism by means of vectors. There are 2 main types of vectors:plasmids and viruses (see previous notes on micro-organisms).
1.1 Gene transfer using plasmids
Agrobacterium tumefaciens is a bacterium that contains a section of DNA called a plasmid in addition to its usual component of DNA. This tumour inducing plasmid has the ability to incorporate its DNA into the cells of the plant host, thus acting as a medium to allow the insertion of other genes into crop plants during genetic engineering.
1.2 Gene transfer using viruses
lambda (λ) phage - a bacteriophage which can modify bacteria, stays in the DNA of the host, and replicate the host’s DNA. It does not harm the host during the replication process, but it evolves with the host DNA. The microphage can remain inside the host indefinitely without having any harmful effect. These bacteriophages can be modified using restriction enzymes and foreign DNA. When the bacteriophages are opened, gene modification can be carried out by inserting the desired viral DNA to integrate with the host cells's "chromosome".
2. Others
2.1 Ballistic techniques
Minute tungsten particles are coated with the DNA to be inserted, then shot into the target cells with an explosive charge.
2.2 Electroporation
In this technique, a brief pulse of electric current is passed through the cell, temporarily increasing surface permeability so that DNA is taken up from the surrounding liquid. This has been especially useful with pollen tubes and has resulted in the genetic transformation of seeds.
author: Monica
Showing posts with label Monica. Show all posts
Showing posts with label Monica. Show all posts
Sunday, 24 July 2011
The risk of Gene modification (at a glance)
Genetic engineering is capable of introducing dangerous allergens and toxins into foods (Mohan, 2005). As a gene is a building block for a protein, the introduction of a foreign gene that is not originally produced by the organism, will has the possibility of evoking an allergy that is not found in the conventional food crop (Wesseler, 2005).
This is because the cellular metabolisms are altered and may result in the production of dangerous by-products such as toxins and allergens. Furthermore, the newly-introduced protein may be enzymes that may interupt with the growing process of the food-producing organism, where the vitamins and mineral production may be short-changed (Mohan, 2005).
go to here to see the beenfits of gene modification
author: monica
This is because the cellular metabolisms are altered and may result in the production of dangerous by-products such as toxins and allergens. Furthermore, the newly-introduced protein may be enzymes that may interupt with the growing process of the food-producing organism, where the vitamins and mineral production may be short-changed (Mohan, 2005).
go to here to see the beenfits of gene modification
author: monica
Polymerase chain reaction (PCR)
The polymerase chain reaction (PCR) is a scientific technique in molecular biology to magnify and increase a single or a few copies of a piece of DNA across various extent, generating thousands to millions of copies of a particular DNA sequence (White, 1993). One of the major concept in PCR is thermal cycling, a process where the sample is heated and cooled alternately into a defined series of temperature steps.
During thermal cycling, two strands of the DNA double helix gets separated under high temperature. After heating, the sample is then cooled, where DNA polymerase uses each strand as a template to select the target DNA (Narayanasamy, 2010). The DNA polymerase used are also heat stable. An example will be Taq polymerase, an enzyme originally isolated from the bacterium Thermus aquaticus (Maier, 2009).
This DNA polymerase, through enzymatic action, assembles a new DNA strand from nucleotides (Mullis, 1994). This process is done by using single-stranded DNA as a template and DNA oligonucleotides, which are required for initiation of DNA synthesis (White, 1993). PCR is used in functional analysis of genes, the diagnosis of hereditary diseases and infectious diseases. PCR’s ability in targeting selected DNA also made this process widely used in genetic manipulation (Maier, 2009).
author: monica
During thermal cycling, two strands of the DNA double helix gets separated under high temperature. After heating, the sample is then cooled, where DNA polymerase uses each strand as a template to select the target DNA (Narayanasamy, 2010). The DNA polymerase used are also heat stable. An example will be Taq polymerase, an enzyme originally isolated from the bacterium Thermus aquaticus (Maier, 2009).
This DNA polymerase, through enzymatic action, assembles a new DNA strand from nucleotides (Mullis, 1994). This process is done by using single-stranded DNA as a template and DNA oligonucleotides, which are required for initiation of DNA synthesis (White, 1993). PCR is used in functional analysis of genes, the diagnosis of hereditary diseases and infectious diseases. PCR’s ability in targeting selected DNA also made this process widely used in genetic manipulation (Maier, 2009).
author: monica
Friday, 22 July 2011
genetic modification (in more details)
Firstly, the donor organism,’s DNA is cut by a restriction enzyme. The cut-up section is called “sticky-ends”, which enables the cut sections to meet up with other DNA strands (Mohan, 2005). Proceeding on, plasmids that induce tumour is treated with the same restriction enzyme, opening out the circle of DNA leaving 2 sticky ends. These plasmids consists of Agrobacterium tumefaciens ‘s DNA (Roller, 1998).
Then, the sticky ends are then mixed with plasmid DNA. Next, DNA ligase enzymes are necessary to rejoin the plasmids. However, these ligase enzymes can only be activated with specific conditions such as temperature. The rejoined plasmids are then reintroduced into the bacterium and the bacterium is cultured under standard microbial methods (Mohan, 2005).
The bacterium is then introduced into the plant, where the plant will grow a gall in reaction to the bacterium. A certain number of cells from the gall might contain the required insecticidal gene (Roller, 1998). These sections of the gall may be encouraged to grow by special plant tissue culture techniques, bulked up in the lab before conditions in the medium are changed to encourage growth of roots and shoots (Mohan, 2005). The resulting small plants are then transferred into the field, along with other crops.
author: monica
Then, the sticky ends are then mixed with plasmid DNA. Next, DNA ligase enzymes are necessary to rejoin the plasmids. However, these ligase enzymes can only be activated with specific conditions such as temperature. The rejoined plasmids are then reintroduced into the bacterium and the bacterium is cultured under standard microbial methods (Mohan, 2005).
The bacterium is then introduced into the plant, where the plant will grow a gall in reaction to the bacterium. A certain number of cells from the gall might contain the required insecticidal gene (Roller, 1998). These sections of the gall may be encouraged to grow by special plant tissue culture techniques, bulked up in the lab before conditions in the medium are changed to encourage growth of roots and shoots (Mohan, 2005). The resulting small plants are then transferred into the field, along with other crops.
author: monica
various lab methods used for food testing
Differential scanning calorimetry (DSC)
Differential scanning calorimetry is a thermo-analytical technique in which the difference in the amount of heat required to increase the temperature of a sample and reference is measured as a function of temperature (Flammersheim, 2003). During an analysis, heat flows in (endothermic process) or flows out (exothermic process) of the sample as it undergo physical transformation (Dean, 1995). The differential scanning calorimeters are able to measure the difference in heat flow between the sample and reference and the amount of heat absorbed or released during such transitions (Sheehan, 2009). In the study of food science, DSC is used in the correlation measurement of water dynamics with food texture (Dean, 1995).
Loop-mediated isothermal amplification (LAMP)
Loop mediated isothermal amplification (LAMP) is a single tube technique for the amplification of DNA. LAMP is used in nucleic acid amplification which uses single temperature incubation. During the amplification process, two or three sets of primers and a polymerase with high strand displacement activity are directed at the target sequence (Narayanasamy, 2010). The sequence is amplified at a constant temperature of 60 - 65 °C, and at the same time, replication activity is also carried out. At the end of the process, the release of Magnesium pyrophosphate results in turbidity, thus allowing visible results (Tian, 2008). Due to the specific nature of the action of these primers, the amount of DNA produced in LAMP is considerably higher than PCR based amplification (Tian, 2008).
author: monica.
Differential scanning calorimetry is a thermo-analytical technique in which the difference in the amount of heat required to increase the temperature of a sample and reference is measured as a function of temperature (Flammersheim, 2003). During an analysis, heat flows in (endothermic process) or flows out (exothermic process) of the sample as it undergo physical transformation (Dean, 1995). The differential scanning calorimeters are able to measure the difference in heat flow between the sample and reference and the amount of heat absorbed or released during such transitions (Sheehan, 2009). In the study of food science, DSC is used in the correlation measurement of water dynamics with food texture (Dean, 1995).
Loop-mediated isothermal amplification (LAMP)
Loop mediated isothermal amplification (LAMP) is a single tube technique for the amplification of DNA. LAMP is used in nucleic acid amplification which uses single temperature incubation. During the amplification process, two or three sets of primers and a polymerase with high strand displacement activity are directed at the target sequence (Narayanasamy, 2010). The sequence is amplified at a constant temperature of 60 - 65 °C, and at the same time, replication activity is also carried out. At the end of the process, the release of Magnesium pyrophosphate results in turbidity, thus allowing visible results (Tian, 2008). Due to the specific nature of the action of these primers, the amount of DNA produced in LAMP is considerably higher than PCR based amplification (Tian, 2008).
author: monica.
Friday, 15 July 2011
The two analytical methods used for testing GM food
info taken from Asian food Information centre (org)
Saturday, 9 July 2011
GM food examples (2)- Strawberries with flounder genes
Scientist are currently experimenting it with genes of sea flounder and artic char. They want to see if it can help strawberies to have anti-freeze properties, so that strawberry can be resistant to cold temperatures during growing or transporting.
so next time, when you feel fishy about the unbelievable juicy strawberry that you just bit on.. the fishy feeling may not be unfounded...
and the genes are also implanted to other vegetables like potatoes and tomatoes too :PP
contributor: Monica
so next time, when you feel fishy about the unbelievable juicy strawberry that you just bit on.. the fishy feeling may not be unfounded...
and the genes are also implanted to other vegetables like potatoes and tomatoes too :PP
contributor: Monica
benefits of GM food- at a glance
Genetic modification allows seeds to grow in conditions that may seem impossible for conventional crops. These conditions include high-salt, less fertile lands, shorter periods of seasons, etc.
The ability to of GM crops to grow in less favourable conditions allows flexibility and a wider variety of crops to be cultivated at more places and in a wider scale. It also allows crops to use nitrogen in soil more efficiently and effectively. With all the above mentioned factors, this helps the farmer generates a more stable profit.
In addition, the ability of gene modified crops with lesser or no reliance on the usage of pesticides, helping farmers to save money on pesticides.
Farmers can also save money on labour cost because GM crops does not need regular maintenance such as weeding and fertilizing, compared to conventional crops.
The ability to of GM crops to grow in less favourable conditions allows flexibility and a wider variety of crops to be cultivated at more places and in a wider scale. It also allows crops to use nitrogen in soil more efficiently and effectively. With all the above mentioned factors, this helps the farmer generates a more stable profit.
In addition, the ability of gene modified crops with lesser or no reliance on the usage of pesticides, helping farmers to save money on pesticides.
Farmers can also save money on labour cost because GM crops does not need regular maintenance such as weeding and fertilizing, compared to conventional crops.
blog entry contributor: monica
Patenting GM technology- A monopoly game
Companies that produce genetically modified seeds are allowed to own legal rights to their high-tech product creations. This legalisation encourages companies to produce their products, such as seeds using terminator technology, whereby the farmers have to buy seeds from the company every year because seeds gathered from the GM crops grown from seeds bought in the previous year, do not germinate.
image courtesy from aaronsenvironmental.com
By doing this, the company is monopolizing the seed market and killing off healthy competition among farmers. This monopolization puts farmers from poorer societies into a state of losing out to a big portion of possible income from their conventional farming crops.
Monsanto, Dupont, Bayer are big players in the GM seed market.
image courtesy from (faculty.umf.maine.edu) website.the writer of this blog altered the image a little because the picture contains hints that may be racist.
Contributor: Monica.
Examples of genetically modified food- (1): Golden Rice
Genetically modified food- (1): Golden Rice
Golden rice contains a large amount of A-vitamins. Or more correctly, the rice contains the element beta-carotene which comes from two daffodil genes and one bacterium gene. The advantage of golden rice is that it allows people to get beta carotene from rice. This is especially helpful for people living in poorer countries in Asia, where their staples are rice.
Having beta-carotene from rice allows lesser occurance of deficiencies of Vitamin A, such as eyes problems and night blindness. On the flip side of the coin, this means that there is reliance of large private companies to develop these genetically modified food seeds. As mentioned earlier of the use of terminator technology, the consumption of Golden rice does not benefit farmers in the long-run because they would have to spend money each year to buy these monopolized food crop seeds.
more updates from Monica on other GM food coming up.. continue to watch on!
Golden rice contains a large amount of A-vitamins. Or more correctly, the rice contains the element beta-carotene which comes from two daffodil genes and one bacterium gene. The advantage of golden rice is that it allows people to get beta carotene from rice. This is especially helpful for people living in poorer countries in Asia, where their staples are rice.
Having beta-carotene from rice allows lesser occurance of deficiencies of Vitamin A, such as eyes problems and night blindness. On the flip side of the coin, this means that there is reliance of large private companies to develop these genetically modified food seeds. As mentioned earlier of the use of terminator technology, the consumption of Golden rice does not benefit farmers in the long-run because they would have to spend money each year to buy these monopolized food crop seeds.
more updates from Monica on other GM food coming up.. continue to watch on!
Saturday, 11 June 2011
Cow that produces human milk
source: The telegraph
entry contributor: monica
Saturday, 7 May 2011
Friendship Bread
I didnt know that there's such thing as sharing bacterial culture!
A popular type of bread to make and share is known as ‘Friendship Bread.’ Friendship bread is made using a yeast-based sourdough starter that is kept for an extended period of time, often passing from family to family.
Friendship bread batter is a type of starter culture similar to the sourdough starters used by the pioneers of the Old West.
While foodborne illness outbreaks haven’t been directly linked to modern-day starters used in friendship bread, food safety experts advise asking questions and taking precautions when making and sharing these batters.
• What’s in the starter? High-protein ingredients, such as eggs and milk, can support the growth of disease-causing bacteria. Some recipes call for raw (unpasteurized) milk, which is unsafe to consume.
• Unpasteurized milk contains a wide variety of microorganisms, many of which can cause serious illnesses.
• Eggs may contain bacteria, such as salmonella. Contaminated kitchen equipment or people could add some undesirable bacteria to the mixture, too. A starter containing water, flour, sugar and yeast is a safer option than using milk and “wild yeast.” You can use whole- wheat flour, rye flour, cultured buttermilk or yogurt with live cultures in sourdough starters, too.
• Do the directions recommend keeping the batter refrigerated? Usually starters need two or three days at room temperature to get the fermentation process started, but after that, most food safety experts advise keeping the batter refrigerated. The culture still will grow, but more slowly. Starters can be frozen, too.
• Does the batter have an acidic, “yeasty” aroma? That’s a good sign. If it smells bad, discard it.
• Does the batter have orange or red spots or slime? If so, the batter is spoiled. Discard it carefully in a place where no humans or animals will come in contact with it. (North Dakota State University, 2011).
Author: Monica
Bread
Bread is the staple food in Europe, European-derived cultures such as the Americas, and the Middle East/North Africa, as opposed to East Asia whose staple is rice. Bread is usually made from a wheat-flour dough that is cultured with yeast, allowed to rise, and finally baked in an oven.
Made from wheat, it contributes to the high content of gluten. Gluten gives the dough its springiness and elasticity too!
In addition, wheat flour is also made with other wheat species (including durum, spelt and emmer), rye, barley, maize (or corn), and oats, usually, but not always, in combination with wheat flour. Spelt bread (Dinkelbrot) continues to be widely consumed in Germany, and emmer bread was a staple food in ancient Egypt. Canadian bread is known for its heartier consistency due to high protein levels in Canadian flour.
Other ingredients such as salt, fat and leavening agents such as yeast and baking soda are added during the dough making process. The process of making bread include baking, steaming, frying, or baked on an unoiled skillet. It may be leavened or unleavened.
Author: Monica
Monday, 25 April 2011
Product Specification and sampling
Author: Monica
Product specification
helps in identifying an individual sample product by providing a detailed information and describing the characteristics of the product. The information provided in a product specification allows the stringent quality aspects to be met so that quality product can be produced. It helps to convey the ideal and expected products aspects so that technicians or workers in the manufacturing plant can follow. This ensures uniformity among manufactured products, allowing customer satisfaction. Therefore it helps attain its objective in ensuring that the product stays consistent every time, so as to earn the trust and continued customer’s loyalty.
A product Specification is a company’s Food Standard and a Trade Specification. It bears the statements of the attributes of the product and manufacturing process. By setting specifications, the manufacturer has control over the quality of raw materials and out-going quality of finished product. These specifications and standards will eventually become Standard Operating Procedures (SOP) for the operation departments as they provide information and parameters for the desirable qualities of finished products (Shahidi, 2004).
Sampling is the selection of a small segment of the product to represent the quality of the larger segment of the product. The objective of sampling is to decrease the size of the batch so as to make it more appropriate for laboratory testing and satisfy the sampling plan specifications (Bower,. 2009). There are many types of sampling plan such as Military Standard, Single and Double sampling plan and Second and Third class sampling plan.
In Two and Three Class Sampling Plans, some of the notations are being used to represent certain items:
• n – number of samples that is being tested.
• c – maximum allowable number of sample(s) that gives results that are of unsatisfactory.
• m – upper microbiological limit of the Good Manufacturing Practice (GMP)
• M – (applicable for 3rd class sampling only) limit beyond which the microbial count is considered hazardous or unacceptable.
Sampling methods
A single sampling plan decides to accept or reject the batch based on the examination of a single sample while a double sampling plan involves the inspection of a first sample and a second sample for rejection or acceptance after deciding to accept or reject the first sample (Schilling, 2009).
Random sampling is a method used to select a set of product from the batch to be examined in such a way so that every product in the batch had an equal opportunity to appear in the sample.
Cluster Random Sample is a technique that is used when the population is naturally divided into many clusters. The number of units within clusters is the same as the number of units between clusters. In such conditions, cluster random sample can give an estimation of the population mean that is much accurate as compared to performing a single random sample based on the same sample size (Beri, 2010).
Types of Sampling Plan
Systemic Random Sampling is a sampling that “spreads out” the random selection process so that no two random samples are too close together and it avoids grouping within the sample. The sampling of food can also be done this way, but if there are periodic differences, the data will be misleading (Hubbert, 2003).
A two class sampling plan is a simple plan used to select an acceptable or reject a whole batch of food while a third class sampling plan is used to select an acceptable, marginally acceptable or even unacceptable food of a batch of product.
A military standard creates a batch sampling plan for the examination of the product so as to decide whether to accept or to reject the batch of product (Bower, 2009).
The purpose of microbiological testing is to determine the degree of bacterial contamination on surfaces of equipment, tools, and premises as well as in products.Only proceed to test for the microbial results when leakage is present and nitrate ix insufficient. Microbial testing can be done qualitatively as microbiological screening, for example by contact such as using an impression plate or quantitatively by determining the exact number of microorganism per sample unit (in cm2 or grams) by using the swab or the destructive method.
ISO Packaging
ISO (International Standardization Organization) 11607 Part 2 describes the validation requirements for forming, sealing and assembly processes of sterile barrier systems. The sterile barrier system (SBS) keep the contents sterile up to the point of use (Charles 2001). This protective packaging system is needed the configuration of materials designed to prevent damage to the sterile barrier system and its contents from the time of assembly until the point of use.
Examples of outer protective packaging are dust covers, or trays. Specific names of inner protective packaging material includes Multi Wrap Vacuum Pack MW/VAC. Documentation needs to clearly show the minimum requirements to prevent of ingress of micro-organisms (Debby, 2001).
Quality Control (QC)
ISO 8402 defines Quality Control (QC) as “the operational techniques and activities that are used to fulfill requirements for quality” (Vasconcellos, 2004.) . In the industrial manufacturing profession, quality is being defined in a variety of ways, mainly on product based, user-based, manufacture-based and value-based.
• Product based is the product’s properties or traits that add to the quality of the product.
• User-based quality of the goods is established by the customers.
• Manufacture-based abide international rules.
• Value-based is the incorporation of price into the definition of quality. Value of a product is made up of the cost and grade of product. It also made up of the cost and grade of product.
Conclusion
The consumer’s expectation of quality products have lead to the evolution of stringent checks such as Military standards that are available in 3 different categories mainly “Normal, Reduced and Tightened”. The acceptable level of results is given in range as it is impossible for every batch to abide to a specific result number during testing.
The Sampling plans on the same batch of product is used in different objectives, such as “Normal” is used during outgoing checks, but “Tightened” is used to re-examine products when complaints are received.
Although there may be hidden cost from the maintenance of Quality Control (using Total Quality Management) and abide of ISO packaging requirements, in the long run, the manufacturing company still benefits compare to the additional cost that will incur due to product recall and product re-examination.
Thorough checks have to be checked right from the beginning. It allows safe in-coming materials and high quality out-going materials.
Product specification
helps in identifying an individual sample product by providing a detailed information and describing the characteristics of the product. The information provided in a product specification allows the stringent quality aspects to be met so that quality product can be produced. It helps to convey the ideal and expected products aspects so that technicians or workers in the manufacturing plant can follow. This ensures uniformity among manufactured products, allowing customer satisfaction. Therefore it helps attain its objective in ensuring that the product stays consistent every time, so as to earn the trust and continued customer’s loyalty.
A product Specification is a company’s Food Standard and a Trade Specification. It bears the statements of the attributes of the product and manufacturing process. By setting specifications, the manufacturer has control over the quality of raw materials and out-going quality of finished product. These specifications and standards will eventually become Standard Operating Procedures (SOP) for the operation departments as they provide information and parameters for the desirable qualities of finished products (Shahidi, 2004).
Sampling is the selection of a small segment of the product to represent the quality of the larger segment of the product. The objective of sampling is to decrease the size of the batch so as to make it more appropriate for laboratory testing and satisfy the sampling plan specifications (Bower,. 2009). There are many types of sampling plan such as Military Standard, Single and Double sampling plan and Second and Third class sampling plan.
In Two and Three Class Sampling Plans, some of the notations are being used to represent certain items:
• n – number of samples that is being tested.
• c – maximum allowable number of sample(s) that gives results that are of unsatisfactory.
• m – upper microbiological limit of the Good Manufacturing Practice (GMP)
• M – (applicable for 3rd class sampling only) limit beyond which the microbial count is considered hazardous or unacceptable.
Sampling methods
A single sampling plan decides to accept or reject the batch based on the examination of a single sample while a double sampling plan involves the inspection of a first sample and a second sample for rejection or acceptance after deciding to accept or reject the first sample (Schilling, 2009).
Random sampling is a method used to select a set of product from the batch to be examined in such a way so that every product in the batch had an equal opportunity to appear in the sample.
Cluster Random Sample is a technique that is used when the population is naturally divided into many clusters. The number of units within clusters is the same as the number of units between clusters. In such conditions, cluster random sample can give an estimation of the population mean that is much accurate as compared to performing a single random sample based on the same sample size (Beri, 2010).
Types of Sampling Plan
Systemic Random Sampling is a sampling that “spreads out” the random selection process so that no two random samples are too close together and it avoids grouping within the sample. The sampling of food can also be done this way, but if there are periodic differences, the data will be misleading (Hubbert, 2003).
A two class sampling plan is a simple plan used to select an acceptable or reject a whole batch of food while a third class sampling plan is used to select an acceptable, marginally acceptable or even unacceptable food of a batch of product.
A military standard creates a batch sampling plan for the examination of the product so as to decide whether to accept or to reject the batch of product (Bower, 2009).
The purpose of microbiological testing is to determine the degree of bacterial contamination on surfaces of equipment, tools, and premises as well as in products.Only proceed to test for the microbial results when leakage is present and nitrate ix insufficient. Microbial testing can be done qualitatively as microbiological screening, for example by contact such as using an impression plate or quantitatively by determining the exact number of microorganism per sample unit (in cm2 or grams) by using the swab or the destructive method.
ISO Packaging
ISO (International Standardization Organization) 11607 Part 2 describes the validation requirements for forming, sealing and assembly processes of sterile barrier systems. The sterile barrier system (SBS) keep the contents sterile up to the point of use (Charles 2001). This protective packaging system is needed the configuration of materials designed to prevent damage to the sterile barrier system and its contents from the time of assembly until the point of use.
Examples of outer protective packaging are dust covers, or trays. Specific names of inner protective packaging material includes Multi Wrap Vacuum Pack MW/VAC. Documentation needs to clearly show the minimum requirements to prevent of ingress of micro-organisms (Debby, 2001).
Quality Control (QC)
ISO 8402 defines Quality Control (QC) as “the operational techniques and activities that are used to fulfill requirements for quality” (Vasconcellos, 2004.) . In the industrial manufacturing profession, quality is being defined in a variety of ways, mainly on product based, user-based, manufacture-based and value-based.
• Product based is the product’s properties or traits that add to the quality of the product.
• User-based quality of the goods is established by the customers.
• Manufacture-based abide international rules.
• Value-based is the incorporation of price into the definition of quality. Value of a product is made up of the cost and grade of product. It also made up of the cost and grade of product.
Conclusion
The consumer’s expectation of quality products have lead to the evolution of stringent checks such as Military standards that are available in 3 different categories mainly “Normal, Reduced and Tightened”. The acceptable level of results is given in range as it is impossible for every batch to abide to a specific result number during testing.
The Sampling plans on the same batch of product is used in different objectives, such as “Normal” is used during outgoing checks, but “Tightened” is used to re-examine products when complaints are received.
Although there may be hidden cost from the maintenance of Quality Control (using Total Quality Management) and abide of ISO packaging requirements, in the long run, the manufacturing company still benefits compare to the additional cost that will incur due to product recall and product re-examination.
Thorough checks have to be checked right from the beginning. It allows safe in-coming materials and high quality out-going materials.
Wednesday, 30 March 2011
Clostridium botulinum
Author: Monica
One of the feared microbe is Clostridium botulinum. This strain is very common in under-processed meat products. The toxins produced by the bacterium causes botulism, a condition that can lead to paralysis of the patient. Botulism in humans is always caused by toxin types A, B or E and occasionally by toxin type F. C. botulinum type E (group II) is one of the food-borne pathogenic bacteria that can survive in temperature of 3oC (Blackistore, 1998).
Clostridium botulinum is an anaerobic, Gram-positive, spore forming rod-shaped bacterium that is found widely in the environment such as soil and animal guts. It was first being isolated from salted raw ham in 1897. Clostridium botulinum type E , one of the food-borne pathogenic produce heat resistant spore of up to 90 oC. In addition, most food are pH 5 or pH6 and above. Clostridium botulinum grows from pH 4.5 and above and at water activity level (a w) of 0.94. Inactivation of Clostridium botulinum’s spores is done when the pressure is increased to 600-1400 Megapascal (MPa) and an increase in temperature of 90 oC to 110 oC, the use of pressure-temperature to inhibit the spores during vacuum packaging (Doyle, 2001). Clostridium botulinum can grow in a salt environment of lower than 7% (Sprenger, 2004). Clostridium botulinum causes the food-borne illness botulism. Botulism is caused by neuron toxins produced during the growth of the bacterium in food before eating.
Symptoms of this disease may occur within 12 to 36 hours or after 8 days of consuming the contaminated food. The initial symptoms include vomiting and nausea (Labbe, 2001). The toxin first affects the neuromuscular junctions in the head and neck area, causing the person to have symptoms like double vision, not being able to focus, drooping eyelids, dry mouth, difficulty in speaking clearly and the inability to swallow. The muscles of the body will continue to fail, resulting in paralysis and in severe cases, death (Labbe, 2001).
The growing of spores in food causes the bacterium to produce botulinum toxins. The spores of the bacteria grow best in the presence of oxygen, a pH environment of 4.6 or higher, a low salt environment of 7% and below and a high moisture environment of 95%. This factors suits especially well during the scenario whereby the ham was taken out from its packaging and left in the air for a relatively long time before being served. This could be so if the ham is left on a tray while waiting to be put into a sandwich order. This allows the conversion of the dormant spores from the curing to be reactivated into spores that proliferate. To avoid the production of the toxin in food, it is important to destroy the spores of the bacteria such as cooking the ham (Eco Lab website).As mentioned earlier, one of the ways to destroy the spores of the bacterium is by adding food preservatives such as sufficient sodium nitrite in food to inhibit the growth of C. Botulinum. The food product should also not be stored in the temperature of above 3oC.
One of the feared microbe is Clostridium botulinum. This strain is very common in under-processed meat products. The toxins produced by the bacterium causes botulism, a condition that can lead to paralysis of the patient. Botulism in humans is always caused by toxin types A, B or E and occasionally by toxin type F. C. botulinum type E (group II) is one of the food-borne pathogenic bacteria that can survive in temperature of 3oC (Blackistore, 1998).
Clostridium botulinum is an anaerobic, Gram-positive, spore forming rod-shaped bacterium that is found widely in the environment such as soil and animal guts. It was first being isolated from salted raw ham in 1897. Clostridium botulinum type E , one of the food-borne pathogenic produce heat resistant spore of up to 90 oC. In addition, most food are pH 5 or pH6 and above. Clostridium botulinum grows from pH 4.5 and above and at water activity level (a w) of 0.94. Inactivation of Clostridium botulinum’s spores is done when the pressure is increased to 600-1400 Megapascal (MPa) and an increase in temperature of 90 oC to 110 oC, the use of pressure-temperature to inhibit the spores during vacuum packaging (Doyle, 2001). Clostridium botulinum can grow in a salt environment of lower than 7% (Sprenger, 2004). Clostridium botulinum causes the food-borne illness botulism. Botulism is caused by neuron toxins produced during the growth of the bacterium in food before eating.
Symptoms of this disease may occur within 12 to 36 hours or after 8 days of consuming the contaminated food. The initial symptoms include vomiting and nausea (Labbe, 2001). The toxin first affects the neuromuscular junctions in the head and neck area, causing the person to have symptoms like double vision, not being able to focus, drooping eyelids, dry mouth, difficulty in speaking clearly and the inability to swallow. The muscles of the body will continue to fail, resulting in paralysis and in severe cases, death (Labbe, 2001).
The growing of spores in food causes the bacterium to produce botulinum toxins. The spores of the bacteria grow best in the presence of oxygen, a pH environment of 4.6 or higher, a low salt environment of 7% and below and a high moisture environment of 95%. This factors suits especially well during the scenario whereby the ham was taken out from its packaging and left in the air for a relatively long time before being served. This could be so if the ham is left on a tray while waiting to be put into a sandwich order. This allows the conversion of the dormant spores from the curing to be reactivated into spores that proliferate. To avoid the production of the toxin in food, it is important to destroy the spores of the bacteria such as cooking the ham (Eco Lab website).As mentioned earlier, one of the ways to destroy the spores of the bacterium is by adding food preservatives such as sufficient sodium nitrite in food to inhibit the growth of C. Botulinum. The food product should also not be stored in the temperature of above 3oC.
source of salts and sugar in foods
Author: Monica
Nitrates and nitrites
Nitrates and nitrites
Nitrates helps in preventing oxidation (Doyle, 2007). Nitrate (NO3), in the form of either sodium nitrate or potassium nitrate, is used as a source for nitrite (NO2). Nitrate in meat products is converted into nitrite by the action of bacteria. The nitrite further breaks down in the meat into nitric oxide (NO), which then binds to the iron atom in the center of myoglobin's heme group, preventing oxidation (Sebranek, 1991). Nitrite acts as oxygen scavenger or anti-oxidative substance (Pegg, 2000). The interaction of nitrite in the meat acts as a chelating agent. Trace metals, as well as any liberated non-heme iron from denatured heme pigments are tied up and their effects inactivated (Sebranek, 1991). Nitrate act as decreasing the Oxidation reduction potential (Eh) of cured meat, therefore at low pH 5.5 and below, the meat is not prone to oxidation and in addition, the initial lag phase of bacteria is prolonged (Lawrie, 1998). Oxidation reduction potential is a measure of the tendency of a chemical to be reduced through acquiring electrons. It is measured in Eh (1 Eh = 1 mV).
According to the Sales of Food Act, the legal limit for nitrites in products is capped at 250ppm. This is the legal and sufficient inhibitory amount of nitrites. Furthermore, nitrites help to prevent the spoilage due to the growth of Clostridium botulium. In the study of the effect of nitrite on the pyruvate metabolism of anaerobes, it was found out that the addition of nitrites caused the rate of hydrogen and carbon dioxide to reduce (Hill, 1991). The amount of the Adenosine Triphosphate (ATP) in cell had reduced quickly. This means that the cell has lost much energy, since ATP is the energy source of cell. Thus it was concluded that the presence of nitrites inhibits the pyruvate metabolism of anaerobes (Hill, 1991).
The outgrowth and germination of bacterial spores happens chronologically in five stages; germination (becoming non-refractile, stainable, heat sensitive), swelling of germinated spore, forming new vegetative cells, elongation and cell division. The spore of Clostridium botulisum after germination are inhibited when insufficient concentrations of nitrites were used, while sufficient concentration at 250ppm of nitrites inhibited the germination process itself (Sebranek, 1991). This means although the germinated spores are inhibited with insufficient amount of nitrites, it is not able to prevent the dormant germinated spore’s activation when conditions are suitable. Therefore it is crucial that sufficient nitrites are used. Input concentrations of more than100 mg/kg (ppm) are used for protections against normal flora. At a concentration of 200 mg/kg at the pH of 6.0 is enough to inhibit the strains of Achromobacter, Aerobacter, Escherichia, Clostridium botulisum, Flavobacterium, Micrococcus, and Pseudomonas spp (Sebranek, 1991).
In addition to that, nitrites serves as an antioxidant giving the meat the stable colour and prevent the microbiological growth by retarding it. Apart from giving a pleasant flavor, it also help to prevent the development of oxidative rancidity in the beef. Nitrite also prevents lipid oxidation of cured meats by four mechanisms (Nation webmaster, 2005). The first mechanism is the formation of a stable complex between heem pigments and nitrites, thus preventing release of iron from porphyrin molecule. The second mechanism is the stabilization of unsaturated lipids within tissue membranes against oxidation. The third mechanism is the interaction of nitrite as a metal chelator so that it ties up trace metals in meat as well as any liberated non-heme iron from denatured heme pigments. And lastly, the fourth mechanism is the formation of nitroso and nitrosyl compounds in meat which possess antioxidative properties by acting as radical scavengers (Nation webmaster, 2005).
Salt (NaCl)
Salt is a multifunctional ingredient in cured meat. Sodium ions are responsible of contributing the flavor from salt. An important function of sodium in the perception of flavor is the increased intensity of other flavors that result in the presence of sodium (Ruusunen, 2005). Salt is also a flavor enhancer for the other flavor components in food.
Salt lowers the water activity of the food system by its osmotic property (Doyle, 2007). This also helps to make the conditions less suitable for micro-organisms to survive by inhibiting bacterial growth on the beef ham by dehydration and osmotic pressure (Hui, 2006). The salt penetrates through the beef ham and draw out moisture from it. Salt dehydrates the membranes of bacterial cells, thus inhibiting the growth of most pathogens in food (Ruusunen, 2005). Concluded from the study of Siegel (1981), a salt concentration of at least 13% is able to achieve inhibition of pathogenic microorganisms. However, a higher concentration, maximum 5g in one serving of the meat product, is needed to prevent loss of salt during process such as water drip. Five grams of salt is also the maximum recommended salt intake for adults (Health promotion board, 2010). Together with nitrates, both ingredients help inhibit C. botulinum spores from developing into toxins even at those higher smoking temperature (up to 82°C).
Sucrose
Widely known as table sugar, is used to lower the water activity (aw value) of the food system due to its hygroscopicity. Having the ability to retain water, it reduces water available in the food system and thus reduces the opportunities for the survival of micro-organisms. It gives the similar effect as the common salt (Forsythe, 1994). When sugar is rubbed onto the beef, it diffuses into the ham. Water present in the beef is extracted out through osmotic action, lowering the water activity (Doyle, 2007). Depending on the amount of water activity in the food, sugar is added accordingly to lower the water activity into the desired water activity.
Author: Monica
Enzymatic reaction in meat
Enzymatic reaction in meat
During early postmodern, enzymatic reactions take place due to the hydrolysis of fatty acid. The absence of blood allows lactic acid to be accumulated into muscle and produce pH drop to 5.6 within a few hours. In addition, during the rigor mortis, the pH levels decline (Toldrá, 2009). The amount of water retained in the myofibril structure also decreased, lead to contraction and meat size reduction. The reduction of the space within the structure is due to pH6, the isoelectric point of proteins. The higher the intramuscular content is present in the meat, the longer the time required for efficient salt diffusion (at pH6) and appropriate moisture loss levels will take longer to attain (Toldrá, 2007).
Meat composition
Red meat has many fibres large amount of myoglobin, lipid and high oxidative enzymatic activity. The dipeptides in the muscles are the anti-oxidant which to act as the neurotransmitter and modulators of in the enzyme reaction. As mentioned earlier, the higher the intramuscular content is present in the meat, the longer the time required for salt diffusion and moisture loss.
Apart from the addition of salt in cured meat, migration of water from depth of meat to surface of the meat also decrease the water activity in the meat (Toldrá, 2009). There are two types of water migration. One is from depth to product and second is water evaporation in the surface. Together with process such as curing and smoking, the decrease in water activity in cured meat products meant less favourable conditions are created for the microorganisms to thrive, since microorganism thrives lesser in levels 0.80aw. Diffusion coefficient depends on the salt and water, which is irreversible correlated to the fat content (Toldrá, 2007).
Fats in the meat also affect the dehydration process (Doyle, 2007). Although intramuscular fat gives marbling which is the main factor affecting the juicing, it also controls the reaction of desiccation and the development of flavour. Lipoxygenase catalyze the incorporation of molecular oxygen in polyunsaturated fatty acids, to give a conjugated hydroperoxide as final products (Toldrá, 2007).
Process
When the beef is slaughtered, the beef is drained off. After the drain off, the cow’s hide is carefully cut off. Care is also taken to prevent puncturing the intestine. This is to prevent microorganism from the hide and intestine from contaminating the meat. Water is then sprayed to wash off remaining blood and bone pieces. Then the cut meat is being rubbed with curing ingredients and is stored in the chiller at 0-4°C. It takes 12-15 hours to chill the meat to an internal temperature to 4°C (USDA, 2009). This is essential to prevent anaerobic bacteria at bone joints to cause bone souring spoilage before the salt penetrates the centre of the meat cut (Frederick K, 1981). Lower than 4 degree Celsius may slow down curing process or even halt it. This prevents the development of bacteria and may not be able to react with nitrites. Higher temperatures may increase the curing process but also encourage the growth of undesired micro-organisms.
Ordinary table salt (sodium chloride) is added because of its effect on flavor. Sugar is added to reduce the harshness of salt. Spices and other flavorings often are added to achieve a characteristic "brand" flavor. Nitrate is used as dry curing salt, having the mixture of nitrate, common salt and sucrose are rubbed into the meat. After which the cuts of meat are placed in the curing room. Curing process has other purpose such as removing water, activating some chemical reactions to develop taste and flavor. The refrigerator temperature is used as for optimum reaction between meat and nitrites. Also on the other hand, the low temperature discourages most microorganism growth
It takes about 24 hours to smoke and cook hams. Smoking is usually accomplished in three stages. During curing process first phase, or drying stage, the smokehouse is heated to 51°C. All dampers are opened to allow all excess moisture to escape and there is no smoking during this 8-hour period (Otwell, 2006). During the next eight-hour stage, the dampers are partially closed and the temperature on the house increased to 57°C. Smoke is generated at this phase. The smoke is continued throughout the third stage with all dampers closed, and the temperature on the house raised to 82°C (Otwell, 2006).. The humidity is kept at above 80% to increase heat transfer. The wood used to generate the smoke should be logs from hardwood species. Unlike pine or any other resinous wood or sawdust, smoke from hardwood does not give sooty smoke. Cured meat products are smoked after the curing process to impart a smoked meat flavor. The temperature of the smokehouse will maintain at 82°c, until the temperature inside the product reaches 61°C. During curing, water comes out from the ham, and as mentioned earlier, the decrease in water activity lesser chance for a variety of microorganisms to thrive.
Smoke
Smoking is usually combined with meat drying in meat preservation in many countries. Both smoking and curing reduce water activity reduction. In addition, smoking has bacteriostatic effect on pH (Doyle, 2007). Both techniques have uses the effect of enzymes and heat to help increase protein and lipid changes in the previously salted material. This helps in increasing nutritional quality and also increases the shelf life and safety quality of the product.
Smoke imparts flavor, color, and other sensory effects to foods. Smoking also creates a physical barrier for the meat. When the meat is being smoked, a layer of “skin” is being formed on the surface of the meat. Not only that, smoke also provides preservation to the food product. It functions as an antimicrobial and antifungal agent. In a study done by Wendorff (1981), the results of antibacterial and antifungal activities from a few smoke condensates show that the phenolic content of smoke contributes greatly to the antimicrobial and antifungal effects of smoke. But when it is faced with a few types of microorganisms, smoke is not an effective antimicrobial agent. Therefore, the usage of other hurdles such as salt or nitrates is used together with smoking.
In dry cured meat, the desired value of water value activity of 0.8, and moisture value of 24%. This is the value that can ensure good keeping shelf-quality. However, these moisture value and water activity are actually too dry for most preference. In order not to compromise the preservation quality while trying to retain enough moisture to suit most people’s taste, products which have undergone drying are accompanied with the use of smoking to increase the preservation of the product quality. In addition, drying and smoking are deployed with other technology in preservation, which are refrigeration, curing, salting, spicing, package and storage.
Packaging
Vacuum Packaging
Vacuum packaging is needed for the dry cured beef ham so as to prevent continued weight lost. Too much weight loss affects the sensory quality of the product. Vacuum packaging also prevents freezer burn by protecting the meat with vacuumed packed plastics. It also prevents unwanted colour change from freezer burn, thus preventing unsightly products (Stringer, 2000).
Vacuum packaging is widely used in the packaging industry. Before hermetic sealing, air is evacuated from a pack. The removal of atmospheric air inhibits the growth of aerobic and anaerobic spoilage micro-organism and thus, reduces the rate of oxidative deterioration. Therefore it is capable of extending the shelf life of perishable foods. It is an established technique for packaging chilled foods like primal red meats, cured meats and cheese. The presence of anaerobic Clostridium botulisum in the affected food product suggests that carbon dioxide from the atmospheric air has entered into the product due to faults from the packaging, since there should be no air in vacuum packaging (Doyle, 2007).
Refer to next post on the details of the packaging materials and the specific measurement regarding vacuum processing
Refer to next post on the details of the packaging materials and the specific measurement regarding vacuum processing
Material
Packing materials
Materials for vacuum products need to have high O2 barrier and high levels of seal integrity. The plastic bags normally used for vacuum packing are made of multi-ply formulations based on polyolefin resins, with either polyvinylidene chloride or ethylvinyl alcohol as the gas barrier component (Sprenger, 2004). The oxygen permeability of packaging films is measured in terms of the amount of oxygen which passes through a square metre of film in 24hours at atmospheric pressure. This measurement is called the oxygen transmission rate (OTR) and has units of ml/m2/24hr/atmosphere. O2 transmission rates of less than 15cm³m-²day-1atm-1 are required for vacuum packaging. Any greater OTR leads to oxygen and accumulation of oxygen in the pack (Otwell, 2006). The diffusion of atmospheric air will spoil the vacuum condition and make microorganisms viable. The material, in addition, must consist of coextruded or laminated films. This highly ductile plastic barrier laminate which will be draped gently over the food product (Stringer, 2000), this prevents formation of ice-crystals from gathering on the product surface during freezing. During the manufacturing process, the top and bottom web films are sealed from the edge of pack to edge of product, pack integrity is maximized and juice exudation is limited.
Therefore from the above discussed properties of an ideal vacuum packing material, PVDC (poly vinylinden chloride) is chosen. In addition of the properties mentioned above, it also has barrier properties which prevent the transmission of water vapor or oxygen (Sprenger, 2004). Apart from preventing the ice crystal formation, this plastic material also helps in eliminating freezer burn and dehydration, which helps in the preservation of the product’s sensory qualities.
There are 2 methods in which the process is carried out, Grace System and chamber system. The Grace system is carried out by subjecting the bag interiors to a vacuum i.e., reduced pressure after which the bags are sealed by any suitable means such as by the application of clips round the bag neck or by heat sealing the openings of the bag. The chamber system is carried out in a sealed vacuum chamber which is capable of being subjected to reduced pressure; in the chamber the bags previously filled with the meat, are sealed, and then the chamber is returned to atmospheric pressure by the admission of air so that the material of the bag is drawn into contact with the meat (Spooncer, 2010).
The reason for using curing and vacuum packaging
Vacuum packaging is needed for the dry cured beef ham so as to prevent continued weight lost. During curing, water comes out from the ham. During curing, salt is rubbed over the surface of the ham and it is pressed. This pressing helps draw out the moisture. Moisture is drawn out from the ham by the sodium chloride which preserves it. The salt penetrates through the beef ham and draw out moisture from it. Vacuum packaging also prevents freezer burn by protecting the meat with vacuumed packed plastics. It also prevents unwanted colour change from freezer burn, thus preventing unsightly products.
Storage
The spores of the bacteria grow best in the presence of oxygen, a pH environment of 4.6 or higher, a low salt environment of 7% and below and a high moisture environment of 95%. The food product should also not be stored in the temperature of above 3oC (Stringer, 2000). As light accelerates oxidation, the manufacturer can store the vacuum meat product in chiller storage with dim light. However, the light must be bright enough for workers to realize any damage in the products such as holes and discolouration (Doyle, 2007).
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