Thermal Processing
Thermal processing involves heating foods in hermetically sealed containers for specific time at a specific temperature to eliminate the microbial pathogens that endanger public health and microorganisms and enzymes that deteriorate food during storage.
Credit for invention of thermal processing (canning, as it was originally called) goes to Nicholas Appert, a French confectioner.
The original concept of in-container sterilization of foods, however, has come a long way since Appert first introduced “the art of canning” in 1810.
As introduced and developed in the initial stages the primary focus of canning was safety and shelf stability.
Today, however, the consumer demands much more than just safe and shelf stable food – including, primarily, higher quality food with greater convenience in the end use.
And food processors look for more energy-efficient, cost effective and high-speed processing technologies.
High temperature, short-time (HTST) techniques have primarily involved to minimize the severity of heat treatment and promote product quality.
Continuous aseptic processing and packing further minimize the heat severity by quick heating and cooling of the food, prior to packaging, under aseptic conditions.
This profile, thermostable, microwavable packages have been developed for promoting faster heat transfer rates, which minimizes the heat damage to product quality while adding the convenience of package microwavability.
Rotary and continuous cooker for canned food have been based on product agitation during processing to accelerate the rate of heat transfer in order to promote better quality in processed foods.
Microwave, radio frequency, and ohmic heating techniques have gained attention as alternate and nonconventional rapid heating techniques. However, although different procedures can be employed for thermal processing, it is still necessary to design a process that would deliver the required minimum heat treatment to render the food safe.
Thermal Processing
Wednesday, November 18, 2009
Sunday, November 01, 2009
Citrus Processing
Citrus Processing
Botanically, citrus varieties are forms of berry fruits n which the hairs inside the ovary walls form juice sacs.
Epicarp is the familiar highly colored, oil bearing outer layer. Both juice and oils are now valuable commodities in all citrus varieties and the recovery of both material is important to the economics of processing.
Many different processes are used world-wide for citrus types with a two stage operation being widely employed. In a typical process, the fruit passes over an abrasive surface or roller where the sacs in the epicarp are pierced and oil washed away by water spray.
The resulting oil-in-water emulsion is screened to remove vegetable debris and oil is separated by centrifugation and then dried and packed.
The rasped fruit then moved onto an extractor where the juice is removed leaving albedo (pith) and peel (flavedo).
Various juice extractors have been used with fruit being encompassed in a roll mill or screw press, or the juice bearing material reamered out.
Expressed juice is subjected to screening (sometimes referred to as finishing) before being further processed.
Limes are normally processed in a slightly different manner. Washed fruit is compressed in a screw press to yield a pulpy juice that typically also contains the oil emulsion.
Larger pieces of pulp are screened out and in the classical process, juice and oil emulsion are fed to large tanks where a natural separation process occurs.
Naturally occurring enzymes, which may be enhanced by the addition of commercially available synthetic pectolytic enzymes, clarify the juice while the oil bearing emulsion and pulp settle to the top of the tank. At the same time other debris settles below the clarified layer.
Clarified juice is then typically filtered and concentrated while oil bearing emulsion is steam distilled. The process often requires a period of some hours of heating before actual distillation starts and it is in this way that the oil is brought to the specification required by the consumer.
Stream distillation of lime oils usually brings about a number of changes to the components present in the undistilled oil.
The fate of citrus juices both during and after processing will vary with their subsequent use. Whereas lime juice us normally available only as a clarified juice, lemon and orange juices are available both clear and cloudy.
Because of the very high natural acidity (up to 8% s citric acid) of lime and lemon juices, clarification can take place using unpasteurised juices which will not normally ferment.
Orange juice must be treated differently. Clarification is carried out by addition of pectolytic enzymes after pasteurization to destroy microbiological activity.
As with soft drinks fruit juices, the bulk of citrus are subjected to concentration to facilitate shipping and during the process, volatile component are usually collected separately from the juice concentrate.
Both oil an water phase volatile fractions are collected from processes and these are widely used in flavorings.
Citrus Processing
Botanically, citrus varieties are forms of berry fruits n which the hairs inside the ovary walls form juice sacs.
Epicarp is the familiar highly colored, oil bearing outer layer. Both juice and oils are now valuable commodities in all citrus varieties and the recovery of both material is important to the economics of processing.
Many different processes are used world-wide for citrus types with a two stage operation being widely employed. In a typical process, the fruit passes over an abrasive surface or roller where the sacs in the epicarp are pierced and oil washed away by water spray.
The resulting oil-in-water emulsion is screened to remove vegetable debris and oil is separated by centrifugation and then dried and packed.
The rasped fruit then moved onto an extractor where the juice is removed leaving albedo (pith) and peel (flavedo).
Various juice extractors have been used with fruit being encompassed in a roll mill or screw press, or the juice bearing material reamered out.
Expressed juice is subjected to screening (sometimes referred to as finishing) before being further processed.
Limes are normally processed in a slightly different manner. Washed fruit is compressed in a screw press to yield a pulpy juice that typically also contains the oil emulsion.
Larger pieces of pulp are screened out and in the classical process, juice and oil emulsion are fed to large tanks where a natural separation process occurs.
Naturally occurring enzymes, which may be enhanced by the addition of commercially available synthetic pectolytic enzymes, clarify the juice while the oil bearing emulsion and pulp settle to the top of the tank. At the same time other debris settles below the clarified layer.
Clarified juice is then typically filtered and concentrated while oil bearing emulsion is steam distilled. The process often requires a period of some hours of heating before actual distillation starts and it is in this way that the oil is brought to the specification required by the consumer.
Stream distillation of lime oils usually brings about a number of changes to the components present in the undistilled oil.
The fate of citrus juices both during and after processing will vary with their subsequent use. Whereas lime juice us normally available only as a clarified juice, lemon and orange juices are available both clear and cloudy.
Because of the very high natural acidity (up to 8% s citric acid) of lime and lemon juices, clarification can take place using unpasteurised juices which will not normally ferment.
Orange juice must be treated differently. Clarification is carried out by addition of pectolytic enzymes after pasteurization to destroy microbiological activity.
As with soft drinks fruit juices, the bulk of citrus are subjected to concentration to facilitate shipping and during the process, volatile component are usually collected separately from the juice concentrate.
Both oil an water phase volatile fractions are collected from processes and these are widely used in flavorings.
Citrus Processing
Wednesday, October 21, 2009
Homogenization of Milk
Homogenization of Milk
Homogenization is the disintegration if particles in which uniformly or non-uniformly distributed phases of a liquid reach a higher level of mixing and the distribution level stabilizes.
The main purpose of homogenization in the dairy industry is to reduce the size of the fat globules and achieve a uniform diameter of 0.5 – 1 um. This results in both desirable and non desirable changes.
Advantages are:
- Increase of the total surface of the fat globule, which prevents or delays creaming of the fat and increases light reflection
- Enhancement of taste and texture
- Increase in digestibility
Disadvantages are:
- Increased area for attack of microbial lipase, resulting lipolytic changes
- Increased sensitivity to light influences, leading to taste defects such as “rancid’” “soapy” or “oxidized”
- Increased area for microbial contamination
- Reduced thermal stability of the protein (homogenization must be one after the UHT treatment for UHT milk)
Homogenization of Milk
Wednesday, October 14, 2009
Processing and Varieties of Tea
Processing and Varieties of Tea
Tea has more naturally occurring caffeine than does coffee.
However, the brewing process typically dilutes tea more than coffee, resulting in on quarter to one third less caffeine per cup.
The processing of all teas begins with the Camellia sinensis plant.
Only the top two leaves and the unopened leaf bud from the plants are used.
There are four principal methods for processing the plant, and they result in the major of tea that are the most widely consumed.
These are white, green (or fermented), oolong (or semi-fermented), and black (or fermented) tea.
White Tea
White tea tea is derived by the simplest of the four processing methods and in some classification schemes, is group with green tea.
Only the youngest leaves are picked for white tea, and these leaves still contain short white “hair”.
The leaves are simply steamed and dried and their appearance is relatively unaltered.
Brewing then produces a pale yellow cup of tea with a fresh flavor. Examples of white tea are imperial Silver Needles, Drum Mountain White Cloud, Pai Mu Tan and Poobong White Tea Darjeeling.
Tea leaves for the production of green tea are handled with special care because preservation of the healthy natural, active substance in the fresh leaves is essential for the tea to be at its best.
After picking the leaves are set in hot air wither and them usually pan fried to prevent oxidation or fermentation.
The more oxidation takes place, the darker and more pungent the tea is.
Once fried, the leaves are rolled, giving them a twisted, curly or balled appearance and increasing their durability.
This process also helps regulate release of natural substance during steeping.
The leaves are next dried, using a process called firing, in which the leaves are placed in a heat controlled environment.
The most common approach is to move the tea on a conveyor through a rotating drum.
The drum is heated by fire to a temperature that is constantly controlled to ensure even firing of the leaves.
The goal is to reduce the moisture in the leaves to about 4%. In addition, some sugars are caramelized in the process and the polyphenols undergo epimerization.
Firing stabilizes the fragrance and flavor of the tea. The resulting green colored leaves yield a cup of tea high in nutrients and minerals that is the subject of many medical studies.
During production of oolong team the leaves are allowed to mature longer before picking, which results in fuller body.
Upon picking, the leaves are withered much as they are in green tea. However, after withering, their edges are bruised by shaking.
Bruising mixes the cellular constituents and starts the oxidation process. Bruising is typically repeated several times and the leaves are the spread out to dry.
The next step is oxidation, which continues until 20 to 60% of the tea leaf is fermented, depending on the variety of oolong.
Although avoided in creating green teas, this process is essential in oolong and black teas because it yields the heartier, richer flavors characteristic of these varieties.
Fermentation is finally stooped by pan firing and the leaves are ready for export.
Black Tea
Unlike other teas, black tea is completely fermented, giving their characteristic color as well as a strong, rich flavor.
The first treatment of the leaves for black tea is again withering, followed by rolling. Then the leaves are piled up in cool humid rooms to ferment.
After full fermentation, the leaves are fired to stop the process, and the juices that are the product of fermentation dry on the surfaces of the leaves an remain until steeping.
The processed leavers have budding tips called pekoe from Chinese Pak-Ho, meaning hair, probably a reference to the white “down” that appears in the budding leaves.
Processing and Varieties of Tea
Tea has more naturally occurring caffeine than does coffee.
However, the brewing process typically dilutes tea more than coffee, resulting in on quarter to one third less caffeine per cup.
The processing of all teas begins with the Camellia sinensis plant.
Only the top two leaves and the unopened leaf bud from the plants are used.
There are four principal methods for processing the plant, and they result in the major of tea that are the most widely consumed.
These are white, green (or fermented), oolong (or semi-fermented), and black (or fermented) tea.
White Tea
White tea tea is derived by the simplest of the four processing methods and in some classification schemes, is group with green tea.
Only the youngest leaves are picked for white tea, and these leaves still contain short white “hair”.
The leaves are simply steamed and dried and their appearance is relatively unaltered.
Brewing then produces a pale yellow cup of tea with a fresh flavor. Examples of white tea are imperial Silver Needles, Drum Mountain White Cloud, Pai Mu Tan and Poobong White Tea Darjeeling.
Tea leaves for the production of green tea are handled with special care because preservation of the healthy natural, active substance in the fresh leaves is essential for the tea to be at its best.
After picking the leaves are set in hot air wither and them usually pan fried to prevent oxidation or fermentation.
The more oxidation takes place, the darker and more pungent the tea is.
Once fried, the leaves are rolled, giving them a twisted, curly or balled appearance and increasing their durability.
This process also helps regulate release of natural substance during steeping.
The leaves are next dried, using a process called firing, in which the leaves are placed in a heat controlled environment.
The most common approach is to move the tea on a conveyor through a rotating drum.
The drum is heated by fire to a temperature that is constantly controlled to ensure even firing of the leaves.
The goal is to reduce the moisture in the leaves to about 4%. In addition, some sugars are caramelized in the process and the polyphenols undergo epimerization.
Firing stabilizes the fragrance and flavor of the tea. The resulting green colored leaves yield a cup of tea high in nutrients and minerals that is the subject of many medical studies.
During production of oolong team the leaves are allowed to mature longer before picking, which results in fuller body.
Upon picking, the leaves are withered much as they are in green tea. However, after withering, their edges are bruised by shaking.
Bruising mixes the cellular constituents and starts the oxidation process. Bruising is typically repeated several times and the leaves are the spread out to dry.
The next step is oxidation, which continues until 20 to 60% of the tea leaf is fermented, depending on the variety of oolong.
Although avoided in creating green teas, this process is essential in oolong and black teas because it yields the heartier, richer flavors characteristic of these varieties.
Fermentation is finally stooped by pan firing and the leaves are ready for export.
Black Tea
Unlike other teas, black tea is completely fermented, giving their characteristic color as well as a strong, rich flavor.
The first treatment of the leaves for black tea is again withering, followed by rolling. Then the leaves are piled up in cool humid rooms to ferment.
After full fermentation, the leaves are fired to stop the process, and the juices that are the product of fermentation dry on the surfaces of the leaves an remain until steeping.
The processed leavers have budding tips called pekoe from Chinese Pak-Ho, meaning hair, probably a reference to the white “down” that appears in the budding leaves.
Processing and Varieties of Tea
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