The processing of raw milk for drinking or into other diary products requires stringent control to obtain a product that is hygienic and of high organoleptic quality.
Milk is produced on the dairy farm under good hygienic conditions, primarily as a result of using milking macines. The warm milk (30°C) is strained in the milk house, cooled and stored in cans or storage tanks to avoid sunlight. Milk is usually transported to the processing plant in cans or in the tank of a milk truck. Transportation of milk from mountains to valleys by pipelines made of polyethylene or PVC was first introduced in Austria, France and Switzerland.
The milk is first purified with a continuously-operated clarifier (centrifuge). Contaminants are removed in the sediment. Cream separation is often achieved simultaneously. The process is conducted at 40°C at 5,500-6,500 rpm. Such centrifuges have a flow production capacity of up to 20,000 kg/h. Back-mixing allows the milk fat content to be adjusted as desired.
The fluid milk is heated after clarification to improve its durability and to kill disease-causing microorganisms. Heat treatments used are:
• Pasteurization
The milk is treated: at high temperature (85°C for 2 sec); in a short-time, flash process (71-74°C for 15-40 sec) in plate heaters; or by the low temperature or holder process, in which it is heated at 62-65°C for at least 30 min, with stirring, and it is then cooled.
• Ultrahigh temperature (UHT) treatment
The process involves indirect heating by coils or plates at 135-140°C for 6-10 sec, or direct heating by live steam injection at 140-150°C for 2-4 sec, followed by aseptic packaging.
• Sterilization
Milk in retail packages is heated in autoclaves at 110-120°C for 10-20 min.
Heat treatment affects several milk constituents. Casein, strictly speaking, is not a heat-coagulable protein; it coagulates only at very high temperatures. Heating at 120°C for 5 h dephosphorylates sodium or calcium caseinate solutions (100% and 85%, respectively) and releases 15% of the nitrogen in the form of low molecular weight fragments.
However, temperature and pH strongly affect casein association and cause changes in micellular structure. An example of such a change is the pH-dependent heat coagulation of skim milk.
All pasteurization processes supposedly kill the pathogenic microorganisms in milk. The inactivation of the alkaline phosphatase is used in determining the effectiveness of pasteurization. At higher temperatures or with longer heating time, the whey proteins start to denature-this coincides with the complete inactivation of acid phosphatase.
Thursday, September 2, 2010
Sunday, August 22, 2010
Nutritional Properties of Food
Many unit operations, especially those that do not involve heat, have little or no effect on the nutritional quality of foods. Examples include mixing, cleaning, sorting, freeze-drying, and pasteurization. Unit operations that that intentionally separate the components of foods alter the nutritional quality of each fraction compared with the raw material. Unintentionally separation of water-soluble nutrients (minerals, water-soluble vitamins, and sugar) also occurs in some unit operations (for example blanching, and in drip losses from roast or frozen foods).
Heat processing is a major cause of changes to nutritional properties of foods. For example, gelatinization of starches and coagulation of proteins improve their digestibility, and anti-nutritional compounds (for example a trypsin inhibitor in legumes) are destroyed. However, heat also destroys some types of heat-labile vitamin, reduces the biological value of proteins, (owing to destruction of amino acids or Maillard browning reactions) and promotes lipid oxidation.
Oxidation is a second important cause of nutritional changes to foods. This occurs when food is exposed to air (for example in size reduction or hot-air drying) or because of the action of heat or oxidative enzymes. The main nutritional effects of oxidation are:
1.The degeneration of lipids and subsequent reactions to form a wide variety of carbonyl compounds, hydroxy compounds and short chain fatty acids, and in frying oils to toxic compounds.
2.Destruction of oxygen-sensitive vitamins.
The importance of nutrient losses during processing depends on the nutritional value of a particular food in the diet. Some foods (for example bread and milk) are an important source of nutrients for large numbers of people. Vitamin losses are therefore more significant in these foods than in those, which either are eaten in small quantities or have low concentration of nutrients.
In industrialized countries, the majority of the population achieve an adequate supply of nutrients from the mixture of foods that is eaten. Losses due to the processing of one component of the diet are therefore insignificant to the long-term health of an individual. In an example, complete meals, which initially contained 16.5 micro-grams of vitamin A lost 50% on canning and 100% after storage for 18 months. Although the losses appear to be significant, the original meal contained only 2% of the recommended daily intake (RDA) and the extent of loss is therefore of minor importance. The same meal contained 9 mg of thiamin and lost 5% after 18 months’ storage. The thiamin content is ten times the RDA, and adequate quantities therefore remained. Possible exceptions are the special dietary needs of pre-term infants, pregnant women, and the elderly. In these groups, there may be either a special need for certain nutrients or a more restricted diet than normal.
Variation in nutrient losses between cultivars or varieties can exceed differences caused by alternative methods of processing. Growth conditions, or handling and preparation procedures before processing, also cause substantial variation in nutrients loss.
Heat processing is a major cause of changes to nutritional properties of foods. For example, gelatinization of starches and coagulation of proteins improve their digestibility, and anti-nutritional compounds (for example a trypsin inhibitor in legumes) are destroyed. However, heat also destroys some types of heat-labile vitamin, reduces the biological value of proteins, (owing to destruction of amino acids or Maillard browning reactions) and promotes lipid oxidation.
Oxidation is a second important cause of nutritional changes to foods. This occurs when food is exposed to air (for example in size reduction or hot-air drying) or because of the action of heat or oxidative enzymes. The main nutritional effects of oxidation are:
1.The degeneration of lipids and subsequent reactions to form a wide variety of carbonyl compounds, hydroxy compounds and short chain fatty acids, and in frying oils to toxic compounds.
2.Destruction of oxygen-sensitive vitamins.
The importance of nutrient losses during processing depends on the nutritional value of a particular food in the diet. Some foods (for example bread and milk) are an important source of nutrients for large numbers of people. Vitamin losses are therefore more significant in these foods than in those, which either are eaten in small quantities or have low concentration of nutrients.
In industrialized countries, the majority of the population achieve an adequate supply of nutrients from the mixture of foods that is eaten. Losses due to the processing of one component of the diet are therefore insignificant to the long-term health of an individual. In an example, complete meals, which initially contained 16.5 micro-grams of vitamin A lost 50% on canning and 100% after storage for 18 months. Although the losses appear to be significant, the original meal contained only 2% of the recommended daily intake (RDA) and the extent of loss is therefore of minor importance. The same meal contained 9 mg of thiamin and lost 5% after 18 months’ storage. The thiamin content is ten times the RDA, and adequate quantities therefore remained. Possible exceptions are the special dietary needs of pre-term infants, pregnant women, and the elderly. In these groups, there may be either a special need for certain nutrients or a more restricted diet than normal.
Variation in nutrient losses between cultivars or varieties can exceed differences caused by alternative methods of processing. Growth conditions, or handling and preparation procedures before processing, also cause substantial variation in nutrients loss.
Saturday, August 21, 2010
Retinol (Vitamin A)
Foreword
Vitamins are minor but essential constituents of food. They are required for the normal growth, maintenance and functioning of the human body. Hence, their preservation during storage and processing of food is of far-reaching importance.
The vitamin requirement of the body is adequately supplied by a balanced diet. A deficiency can result in hypovitaminosis and, if more severe, in avitaminosis. Both can occur not only because insufficient supply of vitamins by food intake, but can be caused by disturbances in resorption, by stress and by disease.
An assessment of the extent of vitamin supply can be made by determination of vitamin content in blood plasma, or by measuring a biological activity which is dependent on the presence of a vitamin, as are many enzyme activities.
Vitamins are usually divided into two general classes: the fat-soluble vitamins, such as A, D, E, and K, and the water-soluble vitamins B1, B2, B6, B12, nicotinamide, pantothenic acid, biotin, folic acid, and C.
Biological Role
Retinol is of importance in protein metabolism of cells, which develop from the ectoderm (such as skin or mucous-coated linings of the respiratory or digestive systems). Lack of retinol in someway negatively affects epithelial tissue (thickening of skin, hyperkeratosis) and causes night blindness.
Requirement and Occurrence
The daily adult requirement of vitamin A is 1.5-1.8 mg. Approx. 75% is provided by retinol intake (as fatty acid esters), while the remaining 25% is through beta-carotene and other provitamin active carotenoids. Due to the limited extent of carotenoid cleavage, at least 6 g of beta-carotene are required to yield 1 g retinol.
Vitamin A resorption and its storage in the liver occur essentially in the form of fatty acid esters. Its content in liver is 250 micro grams/grams fresh tissue, i.e. a total of about 240-540 mg is stored. The liver supplies the blood with free retinol, which then binds to protein in blood. Vitamin A concentration is 45-84 micro grams/100 milliliters plasma in adults; values below 15-24 micro g/100 ml indicate a deficiency.
A hypervitaminosis is known, but the symptoms disappear if the intake of retinal is decreased.
Vitamin A occurs only in animal tissue, above all in fish liver oil, in livers of mammals, in milk fat and in egg yolk. Plants are devoid of vitamin A but do contain carotenoids, which yield vitamin A by cleavage of the centrally located double bond (provitamins A)
Carotenoids are present in almost all vegetables but primarily in green, yellow, and leafy vegetables (carrots, spinach, cress, kale, bell peppers, paprika peppers, tomatoes) and in fruit, with outstanding sources being rose hips, pumpkin, apricots, oranges and palm oil, which is often used for yellow coloring. Animal carotenoids are always of plant origin, derived from feed.
Stability and Degradation
Food processing and storage can lead to 5-40% destruction of vitamin A and carotenoids. In the absence of oxygen and at higher temperatures, as experienced in cooking or food sterilization, the preferential reactions are isomerization and fragmentation. In the present of oxygen, oxidative degradation leads to a series of products, some of which are volatile. This oxidation often parallels lipid oxidation. The rate of oxidation is influenced by oxygen partial pressure, water activity, temperature, etc. Dehydrated foods are particularly sensitive to oxidative degradation.
Tuesday, August 17, 2010
Major Modes of Food Degradation
Preharvest Biological Decay
Before harvest and slaughter, plant and animal foods are subject to a myriad of microbiological diseases including viruses, molds, yeasts, and bacteria. In addition, some foods before harvest can be attacked and diseased or eaten by insects, birds, and rodents. For plants, competition by weeds can result in poor yield. To prevent or control this, one form of processing is the use of chemical or physical means of control or prevention. The use of pesticides, and herbicides are examples of chemical control. Another method of chemical control is the use of drugs such as antibiotics to prevent disease in animals prior to slaughter. Weeding by machine is a physical means of control. These modes of deterioration are not generally considered about shelf life or open dating. However, if the food is subjected to damage, its initial quality will be less. Processing does not make low quality foods better, and overall shelf life will be less after slaughter or harvest than with undamaged foods.
Senescence
Once a fruit, vegetable, cereal grain, or animal product is slaughtered, it is separated from its source of nutrients and water. However, since it is still a viable living system, the enzymes present continue to operate and utilize the available carbohydrate and nutrient stores. For fruits, this process can be of benefit because they can repair post harvest damages, and more important, fruits can be picked prior to optimum maturity, transported long distances to the marketplace and home, and then develop into a high quality product.
For all foods, however, eventually enzymatic biochemical processes occurring post harvest lead to degradation, including loss of color, flavor, nutrients, and texture. In addition, the breakdown products produced damage the tissue so that the foods become subject to microbiological attack with subsequent more rapid decay. To prevent this mode of deterioration, three major processing methods can be used: (1) lowering of temperature slows the reaction; (2) raising the temperature denatures the enzymes and makes them inactive; and (3) removal or binding of water reduce availability (or water activity), which reduces the ability of the enzymes to operate.
Microbiological Disease
Microorganisms constitute a major mechanism by which many foods, especially fresh ones, lose their quality. This is because microbes are ubiquitous in the environment, and can grow rapidly. After a food is harvested or slaughtered, it loses some degree of its ability to fight off microbial attack. If it is physically damaged, then it becomes more susceptible to attack. Bruising, cutting, and trimming constitute such damage. Microbes can grow rapidly on foods (starting with one microbe which divides every 10 min, with sufficient available nutrients, in five hours there would be over one billion microbes present). The basic principle of preservation is to control or destroy them. Much the same controls, are employed as those used for enzymes:
(1) Lower temperature to slow growth.
(2) Raise temperature to kill them.
(3) Remove or bind water to slow or prevent their growth.
(4) Lower pH to slow or stop their growth by adding-acid or fermentation.
(5) Control O2 or CO2 level to control population.
(6) Manipulate food composition to remove nutrients needed by the microbes.
Because in some cases the above methods change the food into a form not desirable by the consumer, chemical means of preservation can be used. These chemicals are used to slow growth or kill the organisms. At the level of use, the chemicals should have no ill effect on the consumer. Examples are the use of calcium propionate in bread and sodium benzoate in some soft drinks.
Knowledge of the rate of growth of microbes as a function of the environmental conditions of the food is very important in the prediction of shelf-life and, thus, the open dating of some foods such as: fresh and ground meats and fresh poultry; fresh fish; dairy products such as milk. Cheese and yogurt; cured meats such as hot dogs, bacon, and bologna: pasteurized fruit drinks; fruits and vegetables; and whole grains.
A second and more serious problem with microorganisms is the fact that some are pathogenic to humans, i.e., they either cause infection when ingested or result in the production of chemicals in the food, which are toxic to humans. Most food processes are designed to guard against contamination with pathogens and the subsequent growth of these pathogens after processing, or as important, to treat the food in such n way as to destroy any potentially harmful microbes that might be inadvertently present in the food. For example, fermentation of foods with useful microbes results in alcohol or acid production. The acid and alcohol prevent the growth of pathogens.
Chemical Deterioration
During the processing of foods, tissue damage occurs which causes the release of various food chemical constituents into the cellular fluid environment. These chemicals can then react with each other or with external factors to lead to deterioration of the food and result in a shortening of the shelf life. Many different reactions can occur which lead to quality and nutrient loss. The major ones are classified below.
Enzymatic
The normal post-harvest enzymatic reactions can lead to a loss in food quality and shelf life. In addition, destruction of cell tissues releases enzymes, which can lead to further deterioration. This reaction is usually very rapid at room temperature, but is controlled in the natural state. Once the food is handled, deterioration starts. Enzymatic decay also occurs in the frozen state unless the enzymes are previously denatured by blanching. Enzymatic reactions also lead to the major mode of deterioration of many refrigerated dough. Unfortunately, heat treatment to denature the enzymes results in loss results in loss of dough functionality. Control of the enzymatic reactions is the same as was discussed for senescence. Knowledge of the rate of these reactions as a function of environmental conditions is very important in prediction of shelf life for open dating. The major environmental factors are oxygen, water, pH, and temperature. Other enzymatic degradations include color losses and vitamin tosses such as for vitamin C.
Lipid Oxidation
Many foods contain unsaturated fats, which are important in the nutrition of humans. Unfortunately, these fats are subject to direct attack by oxygen through an auto catalytic free radical mechanism. This results in the production of rancid off-flavors, which make the food undesirable to consume. Very little fat has to oxidize for the consumer to detect rancidity and reject the food. Unfortunately, the food will still be very nutritious. The free radicals and peroxides produced in this process can react and blench pigments, such as occurs in dried vegetables, and can destroy vitamins C, E, and A. They can also result in protein degradation, making it of poorer quality, as can happen in whole dry milk; can cause darkening of the fat as happens in deep fat frying; and produce toxic substances which have been implicated in some animal studies as potential carcinogens.
Knowledge of the rate of lipid oxidation is important in foods where it be the principal mode of deterioration, for example:
(1) Fried snacks,
(2) Nuts,
(3) Dried meats/vegetables/fish/poultry,
(4) Cereals,
(5) Wheat germ,
(6) Frozen vegetables/meats/fish/poultry,
(7) Some dairy products,
(8) Semi-moist meat products,
(9) Pre cooked refrigerated meats and fish,
(10) Cured meat and fish, coffee, cooking and salad oils, margarine, spices, and dried vegetables such as potatoes and carrots.
Non Enzymatic Browning (NEB)
Non Enzymatic Browning (NEB) is another major chemical reaction leading to a loss of quality and nutritional value. This reaction is the result of reactions between reducing compounds (such as glucose, fructose and lactose) and proteins or amino acids. Browning can also occur as the result of heating sugars to very high temperatures or through the oxidation of vitamin C. In certain cases the reaction is desirable, such as in the toasting of the bread, the crust formed in roasting meats, malting of barley for beer and spirits manufacture, and the production of syrups, molasses, and caramel candies.
Other Chemical Reactions
Other chemical reactions that can lead to food degradation include the thermal destruction of vitamins such as A, B, and C, the effect of light an pigments such as occurs in the browning of meat and bleaching of chlorophyll, the direct oxidation of vitamin C, the effect of light on riboflavin, and the direct oxidation of carotenoid pigments and the loss of flavor through some mechanism. In ever case the effect of temperature, oxygen level, moisture content, and light must be known for the rate of the reaction to be predicted and the time to reach end of shelf life measured. Of importance in all these reactions is a decision as to what extent of degradation is considered to be the end of shelf life.
Physical Degradation
Physical damage can also lead to loss of shelf life. The types of physical damage can be classified into the following categories.
Physical Bruising/Crushing
This mode of deterioration is related to physical abuse of in food harvest, processing, and distribution. It is particularly important to fruits and vegetables, since physical abuse leads to microbial attack and decay. Packaging to prevent abuse is key to long shelf life. With dry materials such as chips, crushing can lead to unacceptability based on consumer desires.
Wilting
Fresh leafy and tuber vegetables can deteriorate if subjected to low relative humidity, losing moisture to their surroundings. This results in loss of crispness and an increased rate of senescence reactions with subsequent quality and nutrient losses. Proper knowledge of the rate of moisture loss for various packaging materials and the maximum allowable moisture loss can be used as one means of setting open dates for fresh produce.
Moisture Loss/Gain
With some food products such as candy, semi moist pet foods, cakes and bread, moisture loss leads to an increase in hardening. If a limit of hardness is known to be unacceptable then predictions to reach this level based on equations which describe the moisture change with time, can be used as one method of prediction of end of shelf life. From this, the open date for best quality can be set. These same equations can be used to predict the moisture loss of flour, pasta, and similar dry products for which a natural loss of moisture occurs and a net weight limit is set for sale. Similarly, some products that gain moisture have a textural limit at which they become too soft, such as potato chips, other dried or fried snacks, and crackers.
Temperature Induced Texture Changes
Temperature fluctuations per se can affect physical modes of deterioration. For example, the continuous rise and fall of temperature around a phase change point leads to melting of fat and the subsequent degradation of quality of some candies and formulated foods.
Staling
Staling is a mode of deterioration important in processed wheat flour products such as bread and cakes. The reaction is a crystallization ion of amylopectin, one of the major starches present in wheat flour. The rate is increased as temperature decreases, which is opposite to the chemical, enzymatic, and microbial reactions discussed earlier. Thus, to prevent staling, the food must not be refrigerated. However, this can result in other reactions causing loss of shelf life.
Induced Textural Changes
Both lipid oxidation and non-enzymatic browning result in degradation of proteins, which leads to toughening and loss of shelf life.
Before harvest and slaughter, plant and animal foods are subject to a myriad of microbiological diseases including viruses, molds, yeasts, and bacteria. In addition, some foods before harvest can be attacked and diseased or eaten by insects, birds, and rodents. For plants, competition by weeds can result in poor yield. To prevent or control this, one form of processing is the use of chemical or physical means of control or prevention. The use of pesticides, and herbicides are examples of chemical control. Another method of chemical control is the use of drugs such as antibiotics to prevent disease in animals prior to slaughter. Weeding by machine is a physical means of control. These modes of deterioration are not generally considered about shelf life or open dating. However, if the food is subjected to damage, its initial quality will be less. Processing does not make low quality foods better, and overall shelf life will be less after slaughter or harvest than with undamaged foods.
Senescence
Once a fruit, vegetable, cereal grain, or animal product is slaughtered, it is separated from its source of nutrients and water. However, since it is still a viable living system, the enzymes present continue to operate and utilize the available carbohydrate and nutrient stores. For fruits, this process can be of benefit because they can repair post harvest damages, and more important, fruits can be picked prior to optimum maturity, transported long distances to the marketplace and home, and then develop into a high quality product.
For all foods, however, eventually enzymatic biochemical processes occurring post harvest lead to degradation, including loss of color, flavor, nutrients, and texture. In addition, the breakdown products produced damage the tissue so that the foods become subject to microbiological attack with subsequent more rapid decay. To prevent this mode of deterioration, three major processing methods can be used: (1) lowering of temperature slows the reaction; (2) raising the temperature denatures the enzymes and makes them inactive; and (3) removal or binding of water reduce availability (or water activity), which reduces the ability of the enzymes to operate.
Microbiological Disease
Microorganisms constitute a major mechanism by which many foods, especially fresh ones, lose their quality. This is because microbes are ubiquitous in the environment, and can grow rapidly. After a food is harvested or slaughtered, it loses some degree of its ability to fight off microbial attack. If it is physically damaged, then it becomes more susceptible to attack. Bruising, cutting, and trimming constitute such damage. Microbes can grow rapidly on foods (starting with one microbe which divides every 10 min, with sufficient available nutrients, in five hours there would be over one billion microbes present). The basic principle of preservation is to control or destroy them. Much the same controls, are employed as those used for enzymes:
(1) Lower temperature to slow growth.
(2) Raise temperature to kill them.
(3) Remove or bind water to slow or prevent their growth.
(4) Lower pH to slow or stop their growth by adding-acid or fermentation.
(5) Control O2 or CO2 level to control population.
(6) Manipulate food composition to remove nutrients needed by the microbes.
Because in some cases the above methods change the food into a form not desirable by the consumer, chemical means of preservation can be used. These chemicals are used to slow growth or kill the organisms. At the level of use, the chemicals should have no ill effect on the consumer. Examples are the use of calcium propionate in bread and sodium benzoate in some soft drinks.
Knowledge of the rate of growth of microbes as a function of the environmental conditions of the food is very important in the prediction of shelf-life and, thus, the open dating of some foods such as: fresh and ground meats and fresh poultry; fresh fish; dairy products such as milk. Cheese and yogurt; cured meats such as hot dogs, bacon, and bologna: pasteurized fruit drinks; fruits and vegetables; and whole grains.
A second and more serious problem with microorganisms is the fact that some are pathogenic to humans, i.e., they either cause infection when ingested or result in the production of chemicals in the food, which are toxic to humans. Most food processes are designed to guard against contamination with pathogens and the subsequent growth of these pathogens after processing, or as important, to treat the food in such n way as to destroy any potentially harmful microbes that might be inadvertently present in the food. For example, fermentation of foods with useful microbes results in alcohol or acid production. The acid and alcohol prevent the growth of pathogens.
Chemical Deterioration
During the processing of foods, tissue damage occurs which causes the release of various food chemical constituents into the cellular fluid environment. These chemicals can then react with each other or with external factors to lead to deterioration of the food and result in a shortening of the shelf life. Many different reactions can occur which lead to quality and nutrient loss. The major ones are classified below.
Enzymatic
The normal post-harvest enzymatic reactions can lead to a loss in food quality and shelf life. In addition, destruction of cell tissues releases enzymes, which can lead to further deterioration. This reaction is usually very rapid at room temperature, but is controlled in the natural state. Once the food is handled, deterioration starts. Enzymatic decay also occurs in the frozen state unless the enzymes are previously denatured by blanching. Enzymatic reactions also lead to the major mode of deterioration of many refrigerated dough. Unfortunately, heat treatment to denature the enzymes results in loss results in loss of dough functionality. Control of the enzymatic reactions is the same as was discussed for senescence. Knowledge of the rate of these reactions as a function of environmental conditions is very important in prediction of shelf life for open dating. The major environmental factors are oxygen, water, pH, and temperature. Other enzymatic degradations include color losses and vitamin tosses such as for vitamin C.
Lipid Oxidation
Many foods contain unsaturated fats, which are important in the nutrition of humans. Unfortunately, these fats are subject to direct attack by oxygen through an auto catalytic free radical mechanism. This results in the production of rancid off-flavors, which make the food undesirable to consume. Very little fat has to oxidize for the consumer to detect rancidity and reject the food. Unfortunately, the food will still be very nutritious. The free radicals and peroxides produced in this process can react and blench pigments, such as occurs in dried vegetables, and can destroy vitamins C, E, and A. They can also result in protein degradation, making it of poorer quality, as can happen in whole dry milk; can cause darkening of the fat as happens in deep fat frying; and produce toxic substances which have been implicated in some animal studies as potential carcinogens.
Knowledge of the rate of lipid oxidation is important in foods where it be the principal mode of deterioration, for example:
(1) Fried snacks,
(2) Nuts,
(3) Dried meats/vegetables/fish/poultry,
(4) Cereals,
(5) Wheat germ,
(6) Frozen vegetables/meats/fish/poultry,
(7) Some dairy products,
(8) Semi-moist meat products,
(9) Pre cooked refrigerated meats and fish,
(10) Cured meat and fish, coffee, cooking and salad oils, margarine, spices, and dried vegetables such as potatoes and carrots.
Non Enzymatic Browning (NEB)
Non Enzymatic Browning (NEB) is another major chemical reaction leading to a loss of quality and nutritional value. This reaction is the result of reactions between reducing compounds (such as glucose, fructose and lactose) and proteins or amino acids. Browning can also occur as the result of heating sugars to very high temperatures or through the oxidation of vitamin C. In certain cases the reaction is desirable, such as in the toasting of the bread, the crust formed in roasting meats, malting of barley for beer and spirits manufacture, and the production of syrups, molasses, and caramel candies.
Other Chemical Reactions
Other chemical reactions that can lead to food degradation include the thermal destruction of vitamins such as A, B, and C, the effect of light an pigments such as occurs in the browning of meat and bleaching of chlorophyll, the direct oxidation of vitamin C, the effect of light on riboflavin, and the direct oxidation of carotenoid pigments and the loss of flavor through some mechanism. In ever case the effect of temperature, oxygen level, moisture content, and light must be known for the rate of the reaction to be predicted and the time to reach end of shelf life measured. Of importance in all these reactions is a decision as to what extent of degradation is considered to be the end of shelf life.
Physical Degradation
Physical damage can also lead to loss of shelf life. The types of physical damage can be classified into the following categories.
Physical Bruising/Crushing
This mode of deterioration is related to physical abuse of in food harvest, processing, and distribution. It is particularly important to fruits and vegetables, since physical abuse leads to microbial attack and decay. Packaging to prevent abuse is key to long shelf life. With dry materials such as chips, crushing can lead to unacceptability based on consumer desires.
Wilting
Fresh leafy and tuber vegetables can deteriorate if subjected to low relative humidity, losing moisture to their surroundings. This results in loss of crispness and an increased rate of senescence reactions with subsequent quality and nutrient losses. Proper knowledge of the rate of moisture loss for various packaging materials and the maximum allowable moisture loss can be used as one means of setting open dates for fresh produce.
Moisture Loss/Gain
With some food products such as candy, semi moist pet foods, cakes and bread, moisture loss leads to an increase in hardening. If a limit of hardness is known to be unacceptable then predictions to reach this level based on equations which describe the moisture change with time, can be used as one method of prediction of end of shelf life. From this, the open date for best quality can be set. These same equations can be used to predict the moisture loss of flour, pasta, and similar dry products for which a natural loss of moisture occurs and a net weight limit is set for sale. Similarly, some products that gain moisture have a textural limit at which they become too soft, such as potato chips, other dried or fried snacks, and crackers.
Temperature Induced Texture Changes
Temperature fluctuations per se can affect physical modes of deterioration. For example, the continuous rise and fall of temperature around a phase change point leads to melting of fat and the subsequent degradation of quality of some candies and formulated foods.
Staling
Staling is a mode of deterioration important in processed wheat flour products such as bread and cakes. The reaction is a crystallization ion of amylopectin, one of the major starches present in wheat flour. The rate is increased as temperature decreases, which is opposite to the chemical, enzymatic, and microbial reactions discussed earlier. Thus, to prevent staling, the food must not be refrigerated. However, this can result in other reactions causing loss of shelf life.
Induced Textural Changes
Both lipid oxidation and non-enzymatic browning result in degradation of proteins, which leads to toughening and loss of shelf life.
Saturday, August 14, 2010
Hygienic Design of Fish Processing Plants
Introduction
Hygienic design of fish and food handling areas is concerned primarily with prevention of microbial hazards, but should also include consideration of occupation safety, convenience of handling or even aesthetics. This article will deal mainly with the reasons behind the hygienic design requirements, stressing the particular hazards involved and their control. In terms of microbiology, this includes preventing contamination of the product and limiting multiplication and spread of microorganisms in the environment.
Food including fish has to pass through many operations as they are handled from the very first steps of harvesting or primary production to the final stages of distribution, retailing and handling in food service establishments or in the home. Hygienic aspects of the sign of food operating areas have to be considered in respect of:
a. Production, harvesting and slaughter;
b. Incoming raw materials;
c. Processing;
d. Storage;
e. Distribution, handling and use
- In wholesale markets and retail premises;
- In food service establishments;
- In kitchens.
In each of these categories, great variability exists in the size and the extent of handling (e.g. a small fishing boat compared with a large factory vessel; a rural market in a developing region compared with a supermarket in an industrialized region). Accordingly, the hygienic requirements for the design of a food handling area may vary considerably even when the same foods are handled. All design factors commonly listed in legislation and codes of practice are not equally important in respect of hygiene. The more important factors include facilities for water supply, waste-disposal and cooling and cold storage facilities. Of less importance with respect to microbiological hazards are buildings (including floors, walls and storage rooms), ventilation, factory location, and clothes changing facilities, lighting, and roadways. However, all requirements need be considered in order to meet national and/or international requirements.
Some General Considerations and Definitions
For a better understanding of the problems involved it is necessary to consider briefly a few terms which are often used, particularly in the Codes of Hygienic Practice.
‘Designed in a hygienic way’
In microbiological terms, this means the creation of environmental conditions, which are not conducive to the growth of microorganisms. Thus, no facilities may be deemed ‘hygienic’ that offers an opportunity for the accumulation of organic matter and/or moisture (e.g. edges, nooks, crevices, fissures, breaks, cracks and scratches or absorbent materials which are resistant to cleaning).
‘Easy to clean’
This is closely related to the term ‘hygienic’. It refers to the arrangement of construction elements with an area (e.g. surfaces of the ceilings or walls, arrangement of pipes leading from sinks or tanks to the wall or to the ground). Dirt, soil, and moisture cannot be easily removed from floors unless joints between walls and floors are covered. ‘Easy to clean’ describes any design, which will minimize the efforts required for thorough and effective sanitation operations.
‘Surface’
In respect of the handling of fish, it has proved useful to distinguish three categories of surfaces encountered within a processing facility
a. Surfaces of materials that are intended to are exposed to foods (e.g. silos and storage bins). The risk of contamination of foods is high.
b. Surfaces of materials not intended to be exposed to foods, but which may accidentally have such contact (e.g. walls in a processing area). The risk of contamination of foods is low.
c. Surfaces of materials not intended to be exposed to foods (e.g. floors and ceilings in processing areas). These are of concern primarily for aesthetic reasons and for safety of personnel but need to be cleanable and kept clean. The risk of contamination of food is low.
‘Clean and unclean’
These terms cannot be defined precisely because their meanings are relatives and vary with the intended purpose and with the products. In fact, there are several degrees of cleanliness. The requirements for cleanliness for storing raw agricultural products are quite different from those in a filling section of Ultra High Temperature milk in dairy plant.
Location and Surrounding Area
In the design phase of fish harvesting and processing areas, several aspects are of particular concern in respect of hygiene. These may include:
a. Proximity of potential source of contamination;
b. Sufficiency and quality of water supply;
c. Waste water removal;
d. Adequacy of power supply, particularly in emergencies;
e. Availability of transportation.
Climate can have an important bearing on design criteria. For example, average, minimum and maximum annual temperatures and relative humidifies must be taken into account in the design of facilities and may require different approaches in hot humidity climates than in cooler, drier regions.
Potential locations for fish plants should be surveyed to assess possible hygienic hazards, e.g. nearby dumping areas may contribute to atmospheric pollution and harbor vermin. Fish handling establishments should not be located close to bone yards, stables or other places where live animals are held or to establishments handling skins and hides such as tanneries, waste disposal sites and other enterprises which deal with highly contaminated material.
To prevent accumulation of water and the generation of dust, roadways and yards serving the establishment should have a hard, and where practicable, paved surface, and adequate drainage.
Hygiene and the Design of Facilities
The micro flora of processing plants is composed of microorganisms that gain entry from the air and water and, more importantly, those brought in by animals, raw materials, dust, dirt, and people. Equipment may also serve as vehicles of contamination.
The following general principles can be summarized for the hygienic design of fish handling areas:
a. Arrangement of Rooms, Areas and Processes within Establishments
- The plant and surrounding area should be such as can be kept reasonably free from objectionable odors, smoke, dust, or other contamination. The building should be sufficient in size without crowding of equipment or personnel, well constructed and kept in good repair. They should be of such design and construction to protect against the entrance and harboring of insects, birds, or other vermin, and to permit ready and adequate cleaning.
- Fish processing plants should be designed and equipped so that all handling and processing operations can be carried out efficiently, and all materials and products can pass from one stage of processing to the next in an orderly manner and with minimum delay.
- Areas where fish are received or stored should be so separated from areas in which final product preparation or packaging is conducted as to prevent contamination of the finished product.
- Separate and adequate storage should be provided for wood, saw dust or similar materials used in smoking of fish.
- Separate and adequate facilities should be provided for drying fish.
- Salt and other ingredients used in the curing or processing of fish or fish products should be stored where appropriate in a dry state and in a manner to prevent their contamination.
- Storage facilities should be available for the proper dry storage of packaging materials.
- If poisonous or harmful materials, including cleaning compounds, disinfectants and pesticides are stored, they should be kept in a separate room designed or marked specifically for this purpose.
b. Structural Components of Establishments
- Floors should be hard surfaced, non-absorbent and adequately drained.
- Internal walls should be smooth, waterproof, resistant to fracture, light colored and readily cleanable.
- Ceiling should be so designed, constructed, and finished as to prevent accumulation of dirt and minimize condensation, mould development, flaking, and should be easy to clean.
- Windowsills should be kept to a minimize size, be sloped inward at least 45 degrees and be at least one meter from the floor.
- All doors through which fish or their products are moved should be sufficiently wide, well constructed of a suitable materials and should be of a self-closing type.
- Stairs, lift cages and auxiliary structures should be so situated and constructed as not to cause contamination to fish
c. Control of environmental
- Premises should be well ventilated to prevent excessive heat, condensation, and contamination with obnoxious odor, dust, vapor, or smoke.
- A minimum illumination of 220 lux (20 foot candles) in general working areas and not less than 540 lux (50 foot candles) at points requiring close examination of the product should be provided and should not alter colors.
- An ample supply of cold and hot potable water and/or clean sea water under adequate pressure should be available at numerous points throughout the premises at all times during the working ours.
- When in-pant chlorination of water is used, the residual content of free chlorine should be maintained at no more than the minimum effective level for the use intended.
- Ice should be made from potable water or clean seawater and should be manufactured, handled and stored to protect it from contamination.
- Proper facilities for washing and disinfection of equipment should be provided.
- Drains should be of an adequate size, suitable type, equipped with traps and with removable grating to permit cleaning.
- A separate refuse room or other equally adequate offal storage facilities should be provided on the premises.
- Staff amenities such as lunchrooms and changing rooms or rooms containing shower or washing facilities should be provided.
- Adequate and conveniently located toilet facilities should be provided.
- Facilities should be available in the processing areas for employees to wash and dry their hands and for disinfection.
Hygienic design of fish and food handling areas is concerned primarily with prevention of microbial hazards, but should also include consideration of occupation safety, convenience of handling or even aesthetics. This article will deal mainly with the reasons behind the hygienic design requirements, stressing the particular hazards involved and their control. In terms of microbiology, this includes preventing contamination of the product and limiting multiplication and spread of microorganisms in the environment.
Food including fish has to pass through many operations as they are handled from the very first steps of harvesting or primary production to the final stages of distribution, retailing and handling in food service establishments or in the home. Hygienic aspects of the sign of food operating areas have to be considered in respect of:
a. Production, harvesting and slaughter;
b. Incoming raw materials;
c. Processing;
d. Storage;
e. Distribution, handling and use
- In wholesale markets and retail premises;
- In food service establishments;
- In kitchens.
In each of these categories, great variability exists in the size and the extent of handling (e.g. a small fishing boat compared with a large factory vessel; a rural market in a developing region compared with a supermarket in an industrialized region). Accordingly, the hygienic requirements for the design of a food handling area may vary considerably even when the same foods are handled. All design factors commonly listed in legislation and codes of practice are not equally important in respect of hygiene. The more important factors include facilities for water supply, waste-disposal and cooling and cold storage facilities. Of less importance with respect to microbiological hazards are buildings (including floors, walls and storage rooms), ventilation, factory location, and clothes changing facilities, lighting, and roadways. However, all requirements need be considered in order to meet national and/or international requirements.
Some General Considerations and Definitions
For a better understanding of the problems involved it is necessary to consider briefly a few terms which are often used, particularly in the Codes of Hygienic Practice.
‘Designed in a hygienic way’
In microbiological terms, this means the creation of environmental conditions, which are not conducive to the growth of microorganisms. Thus, no facilities may be deemed ‘hygienic’ that offers an opportunity for the accumulation of organic matter and/or moisture (e.g. edges, nooks, crevices, fissures, breaks, cracks and scratches or absorbent materials which are resistant to cleaning).
‘Easy to clean’
This is closely related to the term ‘hygienic’. It refers to the arrangement of construction elements with an area (e.g. surfaces of the ceilings or walls, arrangement of pipes leading from sinks or tanks to the wall or to the ground). Dirt, soil, and moisture cannot be easily removed from floors unless joints between walls and floors are covered. ‘Easy to clean’ describes any design, which will minimize the efforts required for thorough and effective sanitation operations.
‘Surface’
In respect of the handling of fish, it has proved useful to distinguish three categories of surfaces encountered within a processing facility
a. Surfaces of materials that are intended to are exposed to foods (e.g. silos and storage bins). The risk of contamination of foods is high.
b. Surfaces of materials not intended to be exposed to foods, but which may accidentally have such contact (e.g. walls in a processing area). The risk of contamination of foods is low.
c. Surfaces of materials not intended to be exposed to foods (e.g. floors and ceilings in processing areas). These are of concern primarily for aesthetic reasons and for safety of personnel but need to be cleanable and kept clean. The risk of contamination of food is low.
‘Clean and unclean’
These terms cannot be defined precisely because their meanings are relatives and vary with the intended purpose and with the products. In fact, there are several degrees of cleanliness. The requirements for cleanliness for storing raw agricultural products are quite different from those in a filling section of Ultra High Temperature milk in dairy plant.
Location and Surrounding Area
In the design phase of fish harvesting and processing areas, several aspects are of particular concern in respect of hygiene. These may include:
a. Proximity of potential source of contamination;
b. Sufficiency and quality of water supply;
c. Waste water removal;
d. Adequacy of power supply, particularly in emergencies;
e. Availability of transportation.
Climate can have an important bearing on design criteria. For example, average, minimum and maximum annual temperatures and relative humidifies must be taken into account in the design of facilities and may require different approaches in hot humidity climates than in cooler, drier regions.
Potential locations for fish plants should be surveyed to assess possible hygienic hazards, e.g. nearby dumping areas may contribute to atmospheric pollution and harbor vermin. Fish handling establishments should not be located close to bone yards, stables or other places where live animals are held or to establishments handling skins and hides such as tanneries, waste disposal sites and other enterprises which deal with highly contaminated material.
To prevent accumulation of water and the generation of dust, roadways and yards serving the establishment should have a hard, and where practicable, paved surface, and adequate drainage.
Hygiene and the Design of Facilities
The micro flora of processing plants is composed of microorganisms that gain entry from the air and water and, more importantly, those brought in by animals, raw materials, dust, dirt, and people. Equipment may also serve as vehicles of contamination.
The following general principles can be summarized for the hygienic design of fish handling areas:
a. Arrangement of Rooms, Areas and Processes within Establishments
- The plant and surrounding area should be such as can be kept reasonably free from objectionable odors, smoke, dust, or other contamination. The building should be sufficient in size without crowding of equipment or personnel, well constructed and kept in good repair. They should be of such design and construction to protect against the entrance and harboring of insects, birds, or other vermin, and to permit ready and adequate cleaning.
- Fish processing plants should be designed and equipped so that all handling and processing operations can be carried out efficiently, and all materials and products can pass from one stage of processing to the next in an orderly manner and with minimum delay.
- Areas where fish are received or stored should be so separated from areas in which final product preparation or packaging is conducted as to prevent contamination of the finished product.
- Separate and adequate storage should be provided for wood, saw dust or similar materials used in smoking of fish.
- Separate and adequate facilities should be provided for drying fish.
- Salt and other ingredients used in the curing or processing of fish or fish products should be stored where appropriate in a dry state and in a manner to prevent their contamination.
- Storage facilities should be available for the proper dry storage of packaging materials.
- If poisonous or harmful materials, including cleaning compounds, disinfectants and pesticides are stored, they should be kept in a separate room designed or marked specifically for this purpose.
b. Structural Components of Establishments
- Floors should be hard surfaced, non-absorbent and adequately drained.
- Internal walls should be smooth, waterproof, resistant to fracture, light colored and readily cleanable.
- Ceiling should be so designed, constructed, and finished as to prevent accumulation of dirt and minimize condensation, mould development, flaking, and should be easy to clean.
- Windowsills should be kept to a minimize size, be sloped inward at least 45 degrees and be at least one meter from the floor.
- All doors through which fish or their products are moved should be sufficiently wide, well constructed of a suitable materials and should be of a self-closing type.
- Stairs, lift cages and auxiliary structures should be so situated and constructed as not to cause contamination to fish
c. Control of environmental
- Premises should be well ventilated to prevent excessive heat, condensation, and contamination with obnoxious odor, dust, vapor, or smoke.
- A minimum illumination of 220 lux (20 foot candles) in general working areas and not less than 540 lux (50 foot candles) at points requiring close examination of the product should be provided and should not alter colors.
- An ample supply of cold and hot potable water and/or clean sea water under adequate pressure should be available at numerous points throughout the premises at all times during the working ours.
- When in-pant chlorination of water is used, the residual content of free chlorine should be maintained at no more than the minimum effective level for the use intended.
- Ice should be made from potable water or clean seawater and should be manufactured, handled and stored to protect it from contamination.
- Proper facilities for washing and disinfection of equipment should be provided.
- Drains should be of an adequate size, suitable type, equipped with traps and with removable grating to permit cleaning.
- A separate refuse room or other equally adequate offal storage facilities should be provided on the premises.
- Staff amenities such as lunchrooms and changing rooms or rooms containing shower or washing facilities should be provided.
- Adequate and conveniently located toilet facilities should be provided.
- Facilities should be available in the processing areas for employees to wash and dry their hands and for disinfection.
Tuesday, August 10, 2010
Hazard Analysis and Assignment of Risk Categories
Overview
Hazard analysis consists of a system evaluation of a specific food and its raw materials or ingredients to determine the risk from biological (primarily infectious or toxin producing food borne illness microorganism), chemical, and physical hazards. The hazard analysis is a step procedure: hazard analysis and assignment of risk categories.
The first step is to rank the food and its raw materials or ingredients according to six hazard characteristics (A-F). A food is scored by using a plus if the food has the characteristic, and a zero (0), if it does not exhibit the characteristic. The six characteristics ranking system is applied for microbiological, chemical and physical hazard ranking, although the characteristics are somewhat different for microbiological and chemical/physical hazard as described later.
The second step is to assign risk categories (VI) to the food and its raw materials and ingredients based on the results of ranking by hazard characteristics. In addition, note that whenever there is a plus for hazard characteristics A (special class that applies to food designated for high risk population), the resulting hazard categories is always VI, even though other hazard characteristics B-F may or may not be a plus.
Several preliminary steps are needed before conducting the hazard analysis. These include developing a working description of the product, listing the raw materials and ingredients required for producing the product, and preparation of a diagram of the complete food production sequence. The listing of raw materials and ingredients is the starting point for the hazard analysis. If the specific mode of preservation for an ingredient is not known (raw, frozen, canned, etc), the ingredient may be assessed for each type of preservation technique that may be utilized in preserving the ingredient.
Microbiological Hazard Characteristics Ranking
Several minor changes in hazard F, to differentiate ranking for consumer products and raw materials and ingredients as received by the processor before any manufacturing steps. As indicated earlier, rank the product and its raw materials and ingredients exhibit the characteristic and a zero when they do not.
A sensitive ingredient is defined as any ingredient historically associated with a known microbiological hazard. The term ingredient normally also applies to raw materials. Sensitive ingredient was coined for microbiological hazards (infectious agents and their toxins) but it is also now used for ingredients and raw materials that are historically associated with known chemical or physical hazards.
The original list of microbiologically sensitive foods was based on the potential presence of the Salmonella species. Now any type of hazardous microorganism may cause a food to be sensitive, and the list of sensitive foods has grown, particularly with the recognition that Listeria monocytogenes is a known threat in many foods. If there is a question as to whether foods sensitive, it should considered sensitive until more information is available for purposes of clarifying its status.
Compounded ingredients may be considered sensitive if they are combinations of sensitive and non-sensitive ingredients. For example, a fat coated on milk powder, or compounded cheese flavor coated on starch. It is best to list all components of a blended materials to determine if the blend contains a sensitive ingredient and also determine if it has received a controlled processing step that destroy hazardous microorganisms. In some cases, it is important to determine if microbiological toxins may also be present in a processed food if it is to be used as an ingredients (e.g. heat stable staphylococcus enterotoxin in canned mushroom).
Many raw materials and ingredients are not considered microbiologically sensitive even though they may occasionally be contaminated with hazardous microorganism.
Chemical and Physical Hazard Risk Assessment Procedures
Hazard characteristics for chemical and physical agents were developed in 1990 for use in the ESCA genetics Corporation training course, “A Practical Application of HACCP,” and were recently published. They are designed so that both chemical and physical hazards in food may be assessed by using the same six hazard characteristics.
Generally, hazard analysis for chemical and physical hazard is conducted like the procedure for microbiological hazards provided in the NACMCF guide. Although the six hazard characteristics are somewhat different, the same plus (+) and zero (0) scoring system and hazard assignment procedure are used.
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