Etiket Arşivleri: Blanching
Kuru ısıda pişirme
Yağ çeşitlerine göre dumanlanma noktaları
Karkasın bölümlerine uygun pişirme yöntemleri
Et, tavuk ve balıkta hedef pişirme sıcaklıkları
Pişirme sırasında meydana gelen değişiklikler
1) SUDA PİŞİRME YÖNTEMLERİ
Ön haşlama (Blanching)
Hafif ateşte haşlama (Poaching)
Kısık ateşte, az suda pişirme (Brasing)
Kendi suyu ile pişirme (Stewing)
PASTEURIZATION AND BLANCHING
PURPOSE OF THE PROCESSES
DESCRIPTION OF PROCESSING SYSTEMS
ESTABLISHMENT OF THE PASTEURIZATION PROCESS
DETERMINATION OF BLANCHING PROCESS
PROCESSES FOR PRODUCT QUALITY IMPROVEMENT
mild \severe \batch-type \continuous
brucellosis tuberculosis Salmonella Listeria
plate heat exchanger\ \a flow diversion
valve (FDV) \cooling medium\ \high
temp.-short-time (HTST) \
\ultra-high-temperature (UHT) \\conveyor tunnel
The processes that utilize relatively mild thermal treatments to achieve the desired results are pasteurization and blanching. Both processes apply thermal treatment to food products in an effort to improve the stability of the product during storage.
Although the magnitude of the thermal processes is similar, application of the processes involves two distinctly different types of food products. Pasteurization is most often associated with liquid foods, while blanching is most often associated with solid foods.
The magnitude of thermal treatment used for both processes is not sufficient to establish storage stability at room temperature. The criteria utilized in establishing these modest thermal treatments are rather specific and are different for different food commodities.
Purpose of Pasteurization Processing
Pasteurization is a mild thermal process applied to a liquid food to increase the product shelf life during refrigeration and to destroy vegetative pathogens (brucellosis and tuberculosis), Salmonella and Listeria.
In fruit juice ,to inactivate enzymes
Thermal processing CANNING
Canning means, the preservation of food in permanent, hermetically sealed containers (of metal, glass, thermostable plastic, or a multi-layered flexible pouch) through agency of heat. Heating is the principle factor to destroy the microorganisms and the permanent sealing is to prevent re-infection.
Containers for canned foods:
The container plays a vital role in food canning, it must be:
1-) Capable of being hermetically sealed to prevent entry of microorganisms.
2-) Impermeable to liquids and gases, including water vapour
3-) Maintain the state of biological stability (i.e, commercial sterility) that was induced by the thermal process alone or in combination with other chemical and physical processes.
4-) Physically protect the contents against damage during transportation, storage and distribution.
Wide varieties of materials are used now for manufacture of cans for meat and poultry preservation. Yet metal containers remain the most frequent used package for canning foods.
Tinplate, tin-free steel, and nickel-plated steel coated with a very thin film of tin are the materials used to manufacture metal food cans.
The amount of tin used being only about 1.5% of the can’s weight and should not contain more than 1% lead. It is used to prevent rusting .
To prevent interaction between meat product and the metal, cans are coated on the inside with an organic material. Two general kinds of organic coatings are used in the food industry : (i) acid-resistant and (ii) sulfur-resistant. Acid-resistant coated cans are used primarily for fruit. Meat products are generally packed in cans that have been lined with sulfur-resistant materials.
(b) Aluminum (c) Plastic
(d) Glass containers and metal closures
Although the wide variety of containers for canned foods, the metal ones are preferable as:
1-) It has a high conductivity of heat.
2-) It cannot easily be broken.
3-) Being opaque, so any possible bad effects of light on
food stuffs are avoided.
4-) Be able to withstand the stresses imposed during thermal
processing and cooling.
5-) Be able to withstand the subsequent handling, which
includes transportation, storage and distribution.
Important food groups
(a) Low acid foods: Meat, fish, poultry, dairy fall into a pH range of 5.0 to 6.8. This large group is commonly referred to as the low acid group.
(b) Acid foods: With pH values between 4.5 and 3.7. Fruits such as pear, oranges, apricots and tomatoes fall in this class.
(c) High acid foods: Such as pickled products and fermented foods. The pH values range from 3.7 down to 2.3, also Jams and Jellies are in this classification.
Preservation of meat by high temperature “canning” commercial sterilized canned meat”
In which all or most bacteria are killed,
In practice, complete sterility is seldom achieved, in the fact that certain microorganisms form spores, which may be heat-resistant. To destroy the spores of certain thermophiles would require a degree of heating which would greatly lower the organoleptic characteristics of canned meat products.
In canning practice “commercial sterility” is achieved by giving a degree of heat treatment sufficient to kill non-sporing bacteria and all spores that might germinate and grow during storage without refrigeration.
(A) Preparatory process
(1)Receiving and storage of raw materials:
(2) Preparation procedures
(i)Thawing (ii) Boning, cutting and trimming
On the trimming table where the inedible parts (such as bones, cartilages blood clots, skins and tendons together with the increased fat are removed. In fish,head,fins,scals and viscera also are removed
(B) Production processes
This is a heat treatment given to many foods prior to canning in hot water (100°C) for 1½-5 minutes, it may extend to 9-11 minutes in some types of fruit and vegetable. Blanching is significance to :
Inactivates enzymes reaction, which may occur during preparation periods.
Aids in cleaning.
Expels internal gases.
Aids in filling of containers by shrinkage or softening of the food.
Assure adequate can vacuum.
Destroys many vegetative microbial cells.
Steam blanching is preferable than hot water.
Meat cuts of variable size and shape and with a variable fat content are ground to form uniform particles of fat and lean. Proper mixing of these particles is extremely important to obtain a uniform blend.
(iii) Mixing with addition of suitable ingredients:
Particles of fat and lean obtained by grinding are tumbled in a mixer to give a uniform distribution of fat and lean particles, and with suitable additions of required ingredients as salt, sodium nitrite, sugar, spices.
(iv) Filling of cans
The mix is then transferred to automatic piston-type-filters and packed into the appropriate cans on the fill line with required weights
The head space volume or depth should be checked due to its critical factor in the attainment of an appropriate vacuum closure.
Such process should be carefully controlled due to: a-) economic aspect
b-) Efficiency of exhausting procedure.
c) Rate of heat penetration.
(v) Exhausting and sealing:
Exhaustion or removal of air from the can before it is sealed, is necessary for the following reasons:
1-) To prevent expansion of the contents during processing which may force the seam.
2-) To produce concave can ends so that any internal pressure may be readily detected and the can rejected.
3-) To lower the amount of oxygen in the can and prevent discolouration of the food surface.
4-)To reduce chemical action between the food and container and hydrogen swells.
5-)To prevent internal corrosion of the cans.
Exhausting methods a) Thermal exhausting (Steam vacuum)
(b) Mechanical exhausting: (machine vacuum)
After the cans are closed, they pass through a detergent spray washer to remove grease and other material. The washing should consist of hot water (66°C) then by suitable pre-rinse, detergent spray wash. Followed by a fresh warm water rinse (66°C).
(vii) Thermal processing:
The cans must be processed (heat treated) immediately after closing (hermetic sealed) at suitable time and temperature
Food to be canned is threatened on the one hand by bacterial spoilage (if under processed) and on the other by danger of lower the nutritive quality by over heating .
vegetative bacteria are killed at 80C/30min.
Spore formers at a temp.110C/30min.
For destroying the spores 121C/3min.
The total time required to sterilize canned food is largely depends on:
a) Size of can. b) Processing temperature
c) Rate of heat penetration at the center of the can. d) pH of the food
e) The type and number of organisms present.
During processing, heat penetrates to the centre of the can by “conduction” and by “convection” currents. In solid meat packs, the heat diffuses by conduction and the process is therefore, slow, the convection current in loosely packed foodstuffs transfer heat faster
Immediately after processing, the cans are cooled in water to a temperature of 36°C to 42°C. to avoid thermophilic spoilage or can rust. If the cans are cooled much below 36°C, they may not dry thoroughly and rusting well result. If the cans are cased at temperatures much over 42°C, thermophilic spoilage may occur.
only potable water, as defined in International Standards of Drinking Water (WHO) should be used in food handling or as an ingredient.
(ix) Container washing
Cans that have just been cooled are dirty and greasy on the outside, and are therefore washed in a bath with detergent and then rinsed to facilitate subsequent handling.
(x) Container drying:
Cooled cans should be immediately dried as the externally dry seams and closures are almost free from microbial infection.
One method that has been found to be quite efficient is the heated bed drier, which rolls cans over a surface heated by steam to 127-130°C covered by an absorbent cloth. Contaminating bacteria are rapidly killed at these temperatures.
(xi) Outside lacquering
Commercial lacquer or enamel is a coloured varnish containing vegetable or synthetic resin Lacquer may be applied to the outside of the can to prevent external corrosion.
(xii) Testing of post-processed container
Processed cans should be incubated at, for example, 30°C for 14 days and/or 37°C for 10-14 days. In addition, if the product is intended to be distributed in areas of the world with tropical climate or is to be maintained at elevated temperatures containers should also be incubated at higher temperatures (5 days at 55°C). Since thermophiles may die during such incubation period, it is advisable to examine containers periodically for the evidence of gas production before the end of incubation
(xiii) Labeling and casing
The role of a label is to inform. The information can be grouped as follow:
Product identification (corned beef, beef stew, luncheon) and grade (fancy, choice, standard).
Brand name, a distinctive name protected by trademark
Net contents by weight or volume.
List of ingredients including additives as per the appropriate regulation.
Country of origin if the product was not processed in the country in which it will be offered for sale.
Production date and the shelf life should be clarified.
b) Casing: (Protective covering)
Containers are usually cased immediately after labeling. Casing which was formerly a manual operation is now highly automated in most canneries.
(xiv) Storage and shelf life
Commercially sterile canned meats should be placed in a cool, dry place since both relative humidity and temperature influence their keeping quality. The storage place must be dry, preferably no more than 30-40% relative humidity.
Storage temperatures of sterile canned meat products should not be above 21.1°C, because higher temperatures markedly accelerate deterioration during storage, thus limiting shelf life.
(A) Spoilage of canned meat according to the condition and content of the can:
1- Swell: bulging of both can ends by +ve internal pressure due to gas generated by microbial or chemical activity. Either hard or soft swell.
2- flipper: a can with normal appearance but one end flips out when the can is struck against a solid object but snaps back to the normal under light pressure.
3- springer: a can bulged from one end which if forced back into normal position, the opposite end bulgs.
4- Leakage: perforated can.
5- overfilled can: has convex ends due to overfilling and not regarded as spoiled.
4(B) Spoilage of canned meat according to the cause:
(i) – Microbial spoilage:
May result from insufficient processing or leakage.
-3 types of spore forming bacteria:
1- gas producing anaerobes and aerobes with optimum growth temp. 37 C.
2- gas producing anaerobes with opt. temp. 55 C.
3- Non-gas producing aerobes or facultative anaerobes with opt. temp. 55 C.——-produce flat souring.
-Leak can be detected by:
1- Bubbles when squeezed under water.
2- Disappearance of vacuum (concavity) when heated to 38 C followed by slow cooling.
Flat souring :
high acid formation without gas production.
-Sour odour, bitter taste, container not swollen.
-Caused by thermophilic bacteria:
1- Bacillus coagulans.
2- Bacillus stearothermophilus.
3- Bacillus circulans.
———–these bacteria attck CHO producing acid without gas.
-Common in tropical and subtropical countries
– Affected cans should be condemned.
(ii)- Chemical spoilage:
1- Hydrogen swell:
Formation of hydrogen gas in can due to internal corrosion or scratch.
-Occur mainly in acidic foods (canned fruits).
-Rarely in canned meat but seen in canned sardines.
-Not related to fermentation or bacterial spoilage.
-Can show varying degree of bulging——when opened—–odorless burnable gas.
-Quite harmless but undifferentiated from swell of spoiled can So, it is rejected.
2- Sulphiding (Sulphur stinker spoilage):
Discolouration of inside of can with pink to dark purple.
-Occur due to reaction of sulphur-containing proteins (liver, kidney, tongue) with liberated H2S from bacterial spoilage (Cl. nigrificans (sulphur stinker)) with the odor of rotted egg.
-It may be accompanied with blackening when H2S react with steel base of tin forming iron sulphide and may lead to pitting.
-Sulphiding can be prevented by——-sulphur-resistant lacquer.
(iii)- Rust and damage:
Rust—— reddish brown ferric oxide seen under label.
– Slight rust—-pass for rapid consumption.
– Severe rust—condemned and rejected.
– Slight damage—–pass for rapid consumption.
– severe damage——rejected.
Preservation of meat by radiation (Irradiation of meat):
1- Preservation of very large meat cuts.
2- Killing all vegetative cells including salmonella, campylobacter, listeria.
3- No change in physical and chemical composition of meat.
1- Vitamins destruction.
2- Off-flavours( fat oxidation by generating free radicals).
3- probable carcinogenic effect and public distrust of irradiation.
Preservation of meat by antibiotics
The choice of suitable antibiotics depend on:
-The type of spoilage to be controlled.
-The stability and solubility of antibiotic at the pH of the food.
-Its stability to heat (Nisin, Tylosin).
-Its lack of toxicity.
Methods of antibiotic application:
1- Feeding the antibiotic for a short period before slaughtering.
2- Injection of antibiotic pre slaughter.
3- Perfusing the whole or quartered carcase by inj..
4- spraying of antibiotics on the carcase or cut surface.
5- the meat may be dipped in an antibiotic containing solution.
6- Using the antibiotics as an aid to processing ttt such as sterilization during canning thus lower heat ttt for processed foods.
Any questions ?
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جزاكم الله خيرا وأتمني لكم دوام التوفيق
Ön haşlama yapılacak malzeme bol soğuk suyun içine konur. (Burada “bol” olmaktan kasıt, genellikle malzemenin hacminin 10 misli su kullanılmasıdır.) Su ağır ağır kaynatılır ve kısa bir süre kaynamaya bırakılır. Bu kısa kaynama süresinin hemen ardından malzeme kaptan alınır. Eğer ön haşlama yapılmış yiyecekler hemen kullanılmayacaksa, hiç bekletmeden süzülüp soğuk su dolu bir kaba aktarılır. Böylece pişme işlemi durdurulmuş olur..
Bu teknik, kemikler ve özellikle tuzlu etler için kullanılır. Böylece kemiklerin gözenekleri açılır, kuvvetli ve istenmeyen ağır kokular yok edilir, kemik ve etteki fazla kan atılır ve nihayet tuzlanmış etlerdeki tuz tadı kabul edilebilir bir düzeye indirilir
•FE 546 THERMAL PROCESS ENGINEERING
•Manolya E. Oner, PhD
•Assistant Professor of Food Engineering
•FE 546 Thermal Process Engineering
•Food processing technology: Principles and practice. 2009. Third ed. P.J. Fellows
•Continuous thermal processing of foods: Pasteurization and UHT Sterilization. 2002. Michael Lewis and Neil Heppell
•Engineering aspects of thermal food processing. 2009. Ricardo Simpson.
•Thermal food processing: New Technologies and Quality Issues. 2006. Da-Wen Sun
Heat treatment remains one of the most important methods used in food processing, not only because of the desirable effects on eating quality (e.g. baking), but also because of the preservative effect on foods by the destruction of enzymes, micro- organisms, insects and parasites.
•Advantages of Heat Processing
•Relatively simple control of processing conditions.
•Capability to produce shelf-stable foods that do not require refrigeration.
•Destruction of anti-nutritional factors (e.g. trypsin inhibitor in some legumes)
•Improvement in the availability of some nutrients (e.g. improved digestibility of proteins, gelatinization of starches and release of bound niacin).
Blanching serves a variety of functions, one of the main ones being to destroy enzymic activity in vegetables and some fruits, prior to further processing. As such, it is not intended as a sole method of preservation but as a pre-treatment which is normally carried out between the preparation of the raw material and later operations (particularly heat sterilization, dehydration and freezing).
•The Factors Influence Blanching Time
• Type of fruit or vegetable
• Size of the pieces of food
• Blanching temperature
• Method of heating
•Why blanching is necessary?
•The maximum processing temperature in freezing and dehydration is insufficient to
inactivate enzymes. If the food is not blanched, undesirable changes in sensory characteristics and nutritional properties take place during storage.
•In canning, the time taken to reach sterilizing temperatures, particularly in large cans, may be sufficient to allow enzyme activity to take place. It is therefore necessary to blanch foods prior to these preservation operations.
•Under-blanching may cause more damage to food than the absence of blanching does, because heat, which is sufficient to disrupt tissues and release enzymes, but not inactivate them, causes accelerated damage by mixing the enzymes and substrates. In addition, only some enzymes may be destroyed which causes increased activity of others and accelerated deterioration.
•Blanching reduces the numbers of contaminating micro-organisms on the surface
of foods and hence assists in subsequent preservation operations. This is particularly
important in heat sterilization, as the time and temperature of processing are designed to achieve a specified reduction in cell numbers.
•Blanching also softens vegetable tissues to facilitate filling into containers and removes air from intercellular spaces which increases the density of food and assists in the formation of a head-space vacuum in cans.
•The two most widespread commercial methods of blanching involve passing food through an atmosphere of saturated steam, steam blanching, or a bath of hot water, water blanching. Both types of equipment are relatively simple and inexpensive.
•Advantages of Water Blanchers
•Lower capital cost and better energy efficiency than steam blanchers.
•Limitations for Water Blanchers
•Higher costs in purchase of water and charges for treatment of large volumes of dilute effluent. Risk of contamination by thermophilic bacteria.
•A product is transported by a chain or belt conveyor through a chamber where ‘‘food-grade’’ steam at approximately 100 C is directly injected.
•Usually temperature in the headspace is measured and the flow rate of steam is controlled.
•Advantages of Steam Blanchers
•Smaller loss of water-soluble components.
•Smaller volumes of waste and lower disposal charges than water blanchers, particularly with air cooling instead of water.
•Easy to clean and sterilize.
•Limitations for Steam Blanchers
•Limited cleaning of the food so washers also required.
•Uneven blanching if the food is piled too high on the conveyor.
•Some loss of mass in the food.
•Individual Quick Blanching (IBQ)
•IBQ was developed to overcome with problems in conventional steam blanching:
– There is often poor uniformity of heating in the multiple layers of food.
-The time–temperature combination required to ensure enzyme inactivation at the centre of the bed results in overheating of food at the edges and a consequent loss of texture and other sensory characteristics.
First stage: The food is heated in a single layer to a sufficiently high temperature to inactivate enzymes. Second stage (termed adiabatic holding): a deep bed of food is held for sufficient time to allow the temperature at the centre of each piece to increase to that needed for enzyme inactivation.
•Effect of blanching on cell tissues:
•Effect of blanching on nutrients
Some minerals, water-soluble vitamins and other water-soluble components are lost during blanching. Losses of vitamins are mostly due to leaching, thermal destruction and, to a lesser extent, oxidation.
• the maturity of the food and variety
• methods used in preparation of the food, particularly the extent of cutting, slicing or dicing
•the surface-area-to-volume ratio of the pieces of food method of blanching time and temperature of blanching (lower vitamin losses at higher temperatures for shorter times)
• the method of cooling
• the ratio of water to food (in both water blanching and cooling).
•Effect of blanching method on ascorbic acid losses in selected vegetables
•Effect of blanching on color and texture
• The time and temperature of blanching also influence the change in food pigments according to their D value.
•The time and temperature conditions needed to achieve enzyme inactivation cause an excessive loss of texture in some types of food. Calcium chloride (1–2%) is therefore added to blancher water to form insoluble calcium pectate complexes and thus to maintain firmness in the tissues.