Aassalamu alikum how are you I hope you are all well. All the praise to Allah subhanahu oatala.I am Abu Saeid Studying MS in Food Processing and Preservation in Hajee Muhammad Danesh Science and Technology University, Dinajpur. Stay in Zia hall room no#226# 1st floor in HSTU campus, Basher hat, Dinajpur.


Thursday, June 9, 2016

Food quality

Food quality:
Quality of foods and food products may be defined as the degree of excellence and includes such things as taste , appearance and nutritional content, evaluation of food quality for consumer acceptance is based on the use of sensory organs or by the use of appropriate instruments,
Sensory evaluation of food quality:
Sensory evaluation of foods may be carried out by human operators or by automated instruments. Sensory evaluation includes three factors
1.      Appearance
2.      Texture
3.      Flavors
Appearance factors include such things as size, shape, different forms of damage, color, transparency and consistency.
Textural factors include various physical factors such as softness, hardness, firmness, juiciness felt by the consumer  when consumer handled the food with fingers (hand feel) or with the tongue, teeth (mouth feel)
Flavor factors depends the sense of smell as well as the sense of taste as experience by a consumer. Flavor characteristics may be evaluated by instrumented methods as well  by panels of judge.
Quality factor for consumer safety:
1.      Nutritional quality
2.      Sanitary quality
3.      Keeping (storage) quality
Nutritional quality: Evaluated by specific analysis such as protein, vitamins, minerals and other nutrients. Chemical instrumental methods are used for evaluating the nutritional quality.
Sanitary quality: Evaluation of sanitary quality of food is based on determining the microbial load. Reduction of microbial load and prevention of recontamination right from the raw material stage through various processing steps to the final product is absolutely essential.
Two newer concepts in product quality and safety have been developed and widely adopted in recent years. Total quality management (TQM) and Hazard analysis and critical control point (HACCP)
TQM is a management system which strives to continuously improve the quality of products by making small but incremental changes in a product ingredient, manufacture, storage which result in overall improvement.
HACCP is applied in food-chain from primary producer to final consumer. HACCP is a preventive food safety system in which a process for manufacturing, storing and distribution a food product is carefully analyzed step-by-step. Points at which light control of the process will result in elimination of a potential hazard are identified and appropriate control measure taken before a problem occurs.
Keeping quality of foods:
The storage stability or keeping quality of foods may be determined by accelerated tests simulating the conditions under which the product is expected to be handled and stored before it reaches the consumers.
Beverage are consumed for their food value, (e.g. milk) thirst quenching and stimulating effects or simply because consumption is pleasurable and drinks are considerable healthful.
Three groups of beverage are commonly consumed.
1.      Carbonated non-alcoholic beverage or soft drink
2.      Non-carbonated non-alcoholic stimulating beverage such as coffee and tea, cocoa
3.      Alcoholic beverage-wine, beer
Carbonated non-alcoholic beverage are generally sweetened, flavored, acidified, colored, artificially carbonated and sometimes chemically preserved. The carbonated beverage may contain artificial flavor or natural fruit juice.
The major ingredients of carbonated soft drink beverages in addition to water and carbon dioxide are sugar, flavorings, colors and acids; water constitutes the largest component to the extent of 92-93%. It must be free from suspended matter, coloring matter and minerals which may interfere with the flavor and color of the soft drink. Sucrose is the most commonly used sweetener. Sodium benzoate is the most commonly used preservative. Pure carbon dioxide gas enhances the flavor and extends the life of the drink.
Carbonated soft drinks are packaged in glass or polyethylene terephthalate (PET) bottles or cans.
Stimulated beverage:
Both coffee and tea have no food value but are consumed entirely for their refreshing and stimulating beverage characteristics due to the presence of caffeine to the extent of about 1% in coffee and about 4% in tea.
Tea is the beverage made when the processed leaves of the tea plants are infused with boiling water. Its leaves contain the chemicals caffeine and tannin.
Types of tea include fermented (black), unfermented (green) and partially fermented (oolong)
1.      Leaves are hand plucked by experience worker.  Only the smallest, youngest leaves are used to produce tea.
2.      Harvested leaves are spread on withering racks to dry
3.      Leaves become soft and pliable and are then roller crushed to break the cell walls and release the enzyme. This process gives the tea its flavors. After rolling the lumps of tea are broken and spread in a fermentation room to oxidize, which turns the leaves to a copper color.
4.      The leaves are finally hot air dried in a process that stops fermentation and turns the leaves black
5.      After the tea is processed, it is sieved to produce tea leaves of a uniform size
Withering, rolling, fermentation, drying, grading and packing
1.      Leaves are hand plucked by experience workers. Only the smallest, youngest leaves are used to produce tea.
2.      Harvested leaves are spread thin and withered in trays or drying racks in drying rooms. During this withering step which lasts over 4 to 18 hr. partial drying of leaves occurs reducing the moisture content of the fresh leaves from about 75% to about 60-65%
3.      The leaves become soft and pliable and are then roller crushed to break the cell walls and release the enzyme. After rolling the leaves are spread out thinly in layers of 5-7cm thick and fermentation occurs over about 1-4 hours at 35-40oC. During fermentation the enzymes, particularly polyphenol oxidase, resulting in a change of color from green to a copper color.
4.      Heating the fermented leaves in over at 85-95oC for about 20 minutes stop the fermentation process.
5.      The dried tea is cleaned and graded into various commercial varieties according to the quality.
6.      Tea is generally blended and packed into aluminum foil lined wooden boxes or paper cartons of smaller sizes.
Green tea is made similar to the black tea without involving the withering and fermentation steps. Green tea is a light yellow-green.
Oolong tea is an intermediate between black and green tea in color and taste, and is obtained by partial withering and light fermentation steps before drying the leaf.
Coffee beans or cherries come from a small tree of the genus coffee. Three species of coffee are of commercial importance, coffea Arabica best quality, coffea robusta and coffea liberiaca lower quality. Ripe fruits are referred to as cherries.
The steps involved include:
        I.            Coffee processing
     II.            Roasting
   III.            Grinding
  IV.            Brewing the decoction
The processing steps involves removal of the skin, pulp around the beans removed. Two methods used dry and wet method. In the dry method of curing, the cherries are hulled and air-dried in the sun on artificially. In the wet or washed-coffee method, the cherries after removal of the outer skin are soaked in water and passed through pulping machines to separate the pulp from the rest of the bean. The dry and wet methods of preparation produce distinctive flavors in the beans.
During roasting the characteristics flavor of coffee is developed. Both and continuous-roasting equipment is available. Roasting is typically carried out at about 260oC for about 5 minutes when the bean temperature reaches about 200o.
The roasted beans are cooled and ground to a size depending upon its intended end use such as home brewing, vacuum extraction, percolator or vending machine.
Freshly ground coffee is contacted with hot water in suitable vessels to extract the soluble caffeine and flavoring materials. Brewing coffee to the correct strength and flavor depends on several variables. These include the ratio of coffee to water, particle size of the ground coffee, temperature of the water, mixing action in the brewer and time.

Cocoa is consumed as a suspension in water and in large amounts to get the stimulating effect in contrast to a clear extract as in the case of coffee and tea. The primary stimulants in cocoa products are the alkaloids, particularly the bromine. Cocoa products provide nutrients such as carbohydrates, fats and proteins

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