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CHAPTER 4
SAFE FOOD HANDLING

4.1 Food Sources

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4.1.1 Approved Sources

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Food premises should obtain foods and food ingredients from approved sources (or sources that are approved by the regulatory authority having jurisdiction).

Examples of approved sources are:

1. Local Foods Manufactured by Licensed Food Premises

   1. Siu Mei and Lo Mei
      Siu mei and lo mei to be on sale in licensed siu mei and lo mei shops should be supplied from licensed food factories or other approved sources. One or more supplier certificates should be produced for inspection whenever requested by inspecting officers.

      Note: Failure to observe this is a breach of licensing condition.

   2. Bakery Products
      Bakery products should be supplied from licensed food factories (bakeries) or other approved sources. One or more supplier certificates should be produced for inspection whenever requested by inspecting officers.

      Note: Failure to observe this is a breach of licensing condition.

   3. Frozen Confections and Milk
      Frozen confections should be supplied from licensed frozen confection factories or other approved sources.  Fresh and reconstituted milk should be supplied from licensed milk factories or other approved sources.

      Note: Failure to observe this is a breach of licensing condition.

   4. Sushi, Sashimi, Oysters / Meat to be Eaten in Raw State
      Pre-prepared sushi, sashimi, oysters / meat to be eaten in raw state should be supplied from licensed food factories or other approved sources, and supplier certificates should be produced for inspection on demand by inspecting officers.

      Note: Failure to observe this is a breach of licensing condition.

   5. Meat and Meat Products
      All fresh meat (e.g. pork, beef, mutton, etc.) on sale in fresh provision shops / market stalls must be obtained from Government abattoirs, licensed slaughterhouses or other approved sources. All meat products (e.g. meat balls, hams and sausages, etc.) should be obtained from licensed food factories or other approved sources. Evidence (e.g. invoices) supporting that the meat or meat product is obtained from such an approved source should be produced on demand by inspecting officers.

      Note: Failure to observe this is a breach of licensing condition.

2. Imported Foods for Sale in Hong Kong

   1. Imported Meat, Game, Poultry and Eggs
      Imported meat, game, poultry and eggs must be obtained from sources approved by the Food and Environmental Hygiene Department for imports with valid official health certificates issued by competent authorities of exporting countries.

      Note: Any person who imports meat, game, poultry or eggs into Hong Kong without an official certificate commits an offence under regulation 4 of the Imported Game, Meat, Poultry and Eggs Regulations.

   2. Imported Milk and Frozen Confections
      Imported milk or milk beverage and frozen confections should be imported from a source of manufacturer which has been approved by the Food and Environmental Hygiene Department.

      Note:
      (1) Any person who imports milk or milk beverages into Hong Kong not from an approved source commits an offence under section 5A(1) of the Milk Regulation.
      
      (2) Any person who imports frozen confections into Hong Kong not from an approved source commits an offence under section 7(1) of the Frozen Confections Regulation.

4.1.2 Prohibited Foods

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The following Prohibited Foods should not be sold or used in the preparation of food in food premises:

1. Chinese dishes - Yu Sang;
2. fresh or frozen meat of animals which have not been slaughtered in a Government slaughterhouse or in a slaughterhouse approved by the Food and Environmental Hygiene Department, except where such meat was lawfully imported into Hong Kong; and
3. shellfish collected in the harbour or the harbour in Aberdeen.

Note: Sale of prohibited foods is an offence under section 29 of the Food Business Regulation.

Rationale

Safe food starts with reputable and reliable food suppliers who meet food hygiene and safety standards of the regulatory authority having jurisdiction. These suppliers operate in a manner which prevents and controls contamination of foods and ensures the foods are safe for human consumption.

4.2 Food Receiving

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4.2.1 Inspection

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Food products should be inspected as they are received to ensure that:

1. they are protected from contamination;
2. if of potentially hazardous food, they are kept at a temperature of:
   1. 4^oC or below; or
   2. above 60^oC;
3. if of potentially hazardous food intended to be received frozen, they should be in frozen state when they are accepted; and
4. if of pre-packaged food, the time gap between the date of receiving and "Use By" or "Best Before" date should be sufficient to avoid expiration of stock.

Rationale

Food contaminated with pathogenic micro-organisms, chemicals and foreign matters may compromise food safety. Therefore, food premises should not accept food known (or suspected) to be contaminated with these substances.

Most pathogenic bacteria grow and multiply rapidly at temperatures between 4^oC and 60^oC. This range of temperatures is therefore called the TEMPERATURE DANGER ZONE. At temperatures lower than 4^oC and higher than 60^oC, bacterial growth slows down or stops (however, most bacteria can survive cold temperatures and resume multiplication later when conditions become suitable again). Potentially hazardous food may be contaminated by pathogenic bacteria which can multiply to dangerous levels at ambient temperatures. As such, potentially hazardous food should be kept at or below 4^oC, or at above 60^oC during delivery, to prevent growth of these bacteria.

Freezing is a process in which the temperature of a food is reduced below its freezing point and the majority of the water inside the food undergoes a change in state to form ice crystals. Freezing preserves food for extended period of time by preventing the growth of micro-organisms that cause food spoilage and foodborne illnesses. To maintain the quality of frozen food, a temperature of -18^oC or less is preferred.

4.2.2 Product Identification

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1. A food business should ensure that all food on the food premises are clearly and properly identified and, upon request by an inspecting officer, can provide information relating to the names and business addresses of the vendors, suppliers, manufacturers, packers, or importers.
2. Records showing the dates, descriptions, quantities and sources / destination of supply should be kept for specific foods for at least 60 days and be readily available for inspection on demand. Such foods include siu mei and lo mei, live / dressed / chilled / frozen poultry, live water birds, fresh or chilled or frozen meat, processed meat and meat products (e.g. meat balls, hams and sausages, etc.), and pre-prepared mixtures for making frozen confections in dispensing machines for retail sale (for at least 3 months).

Rationale

A food business must be able to identify the food that they have on the premises in order to facilitate tracing products in the event of a recall or a food incident. The information can be available from an invoice, receipt or the packaging of the food.

4.3 Food Storage

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1. Raw materials should be stored in a suitable place as quickly as possible after delivery:
   1. storage places should be clean to minimize dirt and food scraps from contaminating the food to be stored; and
   2. storage places of dry food should be pest free and well ventilated.
2. Raw materials should be stored and maintained under conditions that prevent spoilage, protect against contamination and minimize damage:
   1. food should be stored in food-grade containers and covered;
   2. food stocks should be properly and regularly rotated to ensure that the "first-in-first-out" principle is adopted, batch labels may be used for this purpose;
   3. ready-to-eat food should be stored separately or away from raw food, ideally in separate refrigerators;
   4. raw food should be put below ready-to-eat food, if they have to be stored in the same refrigerator; and
   5. food should be stored at least 300mm above the floor.

   Note: Failure to observe (v) is a breach of licensing condition.

3. Potentially hazardous food should be stored:
   1. at or below 4^oC or at above 60^oC; and
   2. frozen if they are intended to be stored frozen (preferably stored at -18^oC or below).

Rationale

Food starts to deteriorate as soon as the crop is harvested or the animal is slaughtered. The rate of deterioration is related to the growth of spoilage bacteria and mould. Hence food should be stored under the right environmental conditions (e.g. suitable temperature, humidity, lighting and atmosphere) to minimize the growth of these micro-organisms and to prevent food from becoming unsafe or unsuitable during their expected shelf-lives.

Proper storage preserves and prolongs shelf-lives of raw food materials and prevents them from contamination by food poisoning bacteria, chemicals and foreign bodies that may finally render the food materials or products unfit for processing or human consumption. Proper storage is one of the essential steps for preventing food from becoming contaminated.

Temperatures between 4^oC and 60^oC are best for multiplication of food poisoning and other foodborne pathogens. Potentially hazardous food should be stored outside these temperatures (stored at or below 4^oC, or at above 60^oC) to suppress these bacteria from multiplying to an unsafe level in the food.

No food can be kept indefinitely. Food that is kept for a long time is likely to become spoiled and attract pest infestation. Effective stock rotation, to ensure that first-come is used first, is essential to avoiding spoilage and preventing pest infestation. In addition, good stock rotation has the advantage of helping to keep the correct levels of stock.

4.4 Food Handling

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4.4.1 Thawing

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1. Frozen potentially hazardous food should be thawed:
   1. at a temperature that will prevent the rapid growth of bacteria that causes foodborne diseases and food spoilage; and
   2. for a minimum time before these bacteria multiply to a dangerous level.
2. When thawing is carried out as an operation separated from cooking, this should be performed in:
   1. a refrigerator or thawing cabinet maintained at 0- 4^oC;
   2. cold running potable water; or
   3. a microwave oven.
3. Unless thawed food is processed immediately, it should be held at 4^oC or below until being used. Food thawed in microwave ovens should be cooked immediately.

Rationale

Freezing prevents bacteria from growing, but does not kill them. Improper thawing (e.g. thawing at room temperature) provides an opportunity for food poisoning bacteria to grow to harmful numbers and / or produce toxins. It should be noted that the food safety risk of thawing frozen ready-to-eat potentially hazardous food is much higher than thawing frozen raw potentially hazardous food that will be cooked or subject to other pathogen-reduction steps before eating.

4.4.2 Cooking

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1. The time and temperature of cooking should be sufficient to reduce any foodborne pathogen that may be present in the food to an acceptable level.
2. When cooking raw animal food (e.g. poultry, pork, minced meat), the centre of the food should reach a temperature of at least 75^oC for 30 seconds, or an effective time / temperature combination (e.g. 65^oC for 10 minutes, 70^oC for 2 minutes).
3. Microwave Cooking
   Raw animal food cooked in a microwave oven should be:
   1. rotated or stirred throughout or midway during cooking to compensate for uneven distribution of heat; and
   2. allowed to stand covered for a minimum of 2 minutes after cooking to obtain temperature equilibrium.

Rationale

It is generally recognized that cooking is to increase the palatability and to tenderize and change the character of food. Cooking, however, is also important in destroying organisms that may cause diseases. Proper cooking is often the critical control point in preventing foodborne disease outbreaks.

It is important to cook food thoroughly, especially meat and poultry, in order to ensure food safety. The centre or the thickest part of the food needs to reach 75^oC for 30 seconds to kill any bacteria causing foodborne diseases, although heating food to a lower temperature for longer periods of time may be equally effective. The centre temperature of cooked food should be checked regularly with an accurate thermometer, which should always be disinfected before use. (Please refer to Appendix II-How to Select and Use a Food Thermometer.)

4.4.3 Hot Holding

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Potentially hazardous food that has been prepared, cooked, and is to be served hot, should be held at a temperature of above 60^oC.

Rationale

It is unlikely for pathogenic bacteria to multiply in food that is above 60^oC. It is thus desirable to serve food that is held at this temperature or above.

4.4.4 Cooling after Cooking

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1. Potentially hazardous food that has been cooked, and is intended to be kept under refrigerated storage prior to serving, should be cooled:
   1. from 60^oC to 20^oC within 2 hours or less; and
   2. from 20^oC to 4^oC within 4 hours or less.
2. There are some ways that can help to cool food rapidly:
   1. reduce the volume of the food by dividing it into smaller portions and / or placing it in shallow containers;
   2. cut large joints of meat and poultry into smaller chunks; and
   3. ensure there is space around food containers so that the cold air in the refrigerator or cool room can circulate freely.

Rationale

Temperatures achieved during cooking are usually sufficient to destroy vegetative cells of pathogens; however, some spores are unaffected. In some cases, cooking activates spores which may germinate during subsequent cooling.

Excessive time for cooling of potentially hazardous food is one of the key contributing factors to foodborne illnesses. During extended cooling, foodborne pathogens that may be present in potentially hazardous food or developed from surviving spores may grow to a sufficient number (and / or produce toxins) to cause illnesses. By reducing the cooling time, the risk for pathogenic bacteria to grow to a dangerous level (and / or producing toxin) will be minimized.

4.4.5 Reheating of Food

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1. Potentially hazardous food that has been previously cooked and cooled, when reheated, should be reheated to 75^oC or above as quickly as possible. Normally, this reheating time should not exceed 2 hours.
2. Potentially hazardous food that has been reheated should not be cooled and reheated for a second time.

Rationale

Pathogenic bacteria may be present in cooked food due to germination of surviving spores or post-contamination after cooking. These pathogens can grow during cooling and cold storage. Proper reheating will minimize the time that cooked food is exposed to the temperature danger zone, which allows pathogenic bacteria to grow during the reheating process.

It should be noted that reheating cannot make potentially hazardous food safe if it has not been cooled properly or protected from contamination. This is because some pathogenic bacteria (such as Staphylococcus aureus) may continue to multiply and produce heat stable toxins under such circumstances. Reheating such food to 75^oC cannot destroy the toxins.

Potentially hazardous food that has been reheated should not be cooled and reheated for a second time to avoid it from repeatedly exposed to temperatures that can support the growth of pathogenic bacteria.

The potential for the growth of pathogenic bacteria is greater in cooked food than in raw food. This is because spoilage bacteria, which inhibit the growth of pathogenic bacteria by competition on raw products, are killed during cooking. Subsequent recontamination will allow pathogenic bacteria to grow without competition if temperature abuse occurs.

4.4.6 Preventing Food from Contamination

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When processing food, adequate steps should be taken to prevent it from contamination. They include:

1. access to food preparation areas should be restricted, as much as practically possible, to food handlers. For visitors including management and maintenance staff, all practicable measures should be taken to ensure that they will not contaminate food when visiting food preparation areas;
2. food handlers should avoid contacting the exposed areas of ready-to-eat food with their bare hands; and use, as much as practicably possible, clean and sanitized utensils such as tongs, spatulas or other food dispensing apparatus in handling such food;
3. raw or unprocessed food should be kept separate from ready-to-eat food;
4. raw fruits and vegetables should be thoroughly washed in potable water to remove soil and other contaminants before being cut, mixed with other ingredients, cooked and served, or offered for human consumption in ready-to-eat form;
5. food contact surfaces should be kept clean and, where necessary, sanitized between uses;
6. foods should not come into contact with surfaces of utensils and equipment that have not been cleaned and sanitized in accordance with procedures described in Chapter 3 of this Code;
7. cleaned and sanitized utensils should be used if organoleptic test is necessary. They should be immediately cleaned and sanitized after tasting or before tasting another food or the same food again;
8. ready-to-eat food under refrigerated storage should be stored above raw meat and fish products;
9. during thawing, drips from thawing food should be prevented from contaminating other food; and
10. chemicals should be kept separate from food processing areas.

Rationale

Bacteria exist everywhere. Pathogenic bacteria pose the greatest danger by causing foodborne illnesses. Good policies and procedures for preventing bacterial contamination can effectively reduce their risk.

4.5 Food Displaying and Serving

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Food under display should be properly protected from all risks of contamination as far as possible in the following ways :

1. Operators of food premises should, when displaying packaged food and unpackaged ready-to-eat food :
   1. securely wrap the packaged food; and
   2. cover unpackaged ready-to-eat food with lids or protect it with food guards.
2. Operators of food premises should, when displaying unpackaged ready-to-eat food for self service:
   1. ensure the display of the food is effectively monitored by employees trained in safe operation procedures;
   2. provide separate and suitable utensils (e.g. tongs, scoops, etc.), or other effective means of dispensing, for each type of food to protect the food from cross-contamination. These utensils should be regularly replaced by clean ones;
   3. provide display cases, food guards (e.g. salad bar sneeze guards) or other appropriate barriers that can effectively protect the food from contamination by customers; and
   4. ensure ice used to cool open food in buffet displays be made from potable water.
3. Operators of food premises should, when displaying potentially hazardous food:
   1. display the food at 4^oC or below, or at above 60^oC; and
   2. ensure the food intended to be displayed frozen remain frozen (preferably at -18^oC or below).
4. Food handlers serving food to consumers should observe the following hygiene practices:
   1. wash hands properly and frequently;
   2. keep hot food at above 60^oC and cold food at 4^oC or below;
   3. minimize bare-hand contact with ready-to-eat food. Whenever possible, handle such food with utensils like scoops, tongs, ladles, paper napkins and disposable gloves;
   4. if gloves are used to handle ready-to-eat food, they should be of single-use (i.e. used for one task only, such as for preparing / handling ready-to-eat food only) and should not be used for any other purpose. They should be discarded when damaged, soiled, or when interruptions (e.g. returning to work after visiting toilet, resting, etc.) occur in operations;
   5. hands should be properly washed before putting on gloves;
   6. ice to be used in food and drink should be dispensed only by clean utensils such as scoops, tongs, or other ice dispensing utensils and should not be handled with bare hands;
   7. ice dispensing utensils should be stored on a clean surface or in the ice with dispensing utensil's handle extended out of the ice;
   8. refresh food displays with completely fresh batches of food. Avoid mixing old food with fresh batches as far as possible;
   9. keep fingers away from rims of cups, glasses, plates and dishes, etc. Make wider use of trays for conveying food;
   10. hold cutlery (i.e. knives, forks and spoons) by the handles;
   11. avoid stacking glasses, cups or dishes on one another when serving food as far as possible;
   12. do not wipe utensils with aprons, soiled cloths, unclean towels, or hands;
   13. do not blow plates or utensils to remove dust or crumbs;
   14. re-wash and sanitize cups, glasses or other utensils that show signs of soiling (e.g. lipstick marks) or other possible contamination (e.g. having dropped on the floor);
   15. discard cracked or chipped dishes, utensils, glasses, etc.; and
   16. never re-use single-use items, such as straws, paper towels, disposable cups and plates.
5. Once served to a consumer, portions of leftover food should not be served again. However, packaged food, other than potentially hazardous food, that is still in an unopened package and is still in sound condition, may be served again.

6. If possible, a staff should be deployed to supervise self-service food display to discourage customers from mishandling or tampering with exposed food, and to remove contaminated food promptly from the service area.

   Note: Failure to store or display for sale any open food other than uncooked perishable food in suitable containers as to prevent the access of dust, insects and vermin is an offence under section 11(1) of the Food Business Regulation.

7. Customers of restaurants and factory canteens should be provided with additional chopsticks or spoons for the common serving of food.

Rationale

The most common food safety problems found during service or display of food are (a) inadequate temperature control and (b) cross-contamination.

Temperature control (i.e. hot food at above 60^oC and cold food at 4^oC or below) during display is essential to keeping potentially hazardous food safe and good quality. This is because bacteria including pathogens are unable to grow (or grow slowly) at these temperatures.

Cross-contamination is the transfer of bacteria from one food (usually raw) to another and is one of the major causes of foodborne illnesses. There are two ways where cross-contamination may occur. Firstly, bacteria can be transferred directly when one food touches another. Secondly, bacteria can be transferred indirectly from hands, equipment, work surfaces, or knives and other utensils to food.

People are a common source of pathogenic bacteria, so an important way to prevent food contamination is to maintain a high standard of personal hygiene and cleanliness such as frequent and thorough washing of hands. The other way is to minimize touching ready-to-eat food with bare hands to prevent pathogens that may be present on hands from transferring to the food.

Wearing gloves is one of the several acceptable ways to minimize unnecessary manual contact with ready-to-eat food. However, hands should be thoroughly washed before putting on gloves to avoid contaminating the outside of the gloves with dirty hands. Gloves should be changed at regular intervals during the day. Torn or punctured gloves should be discarded to avoid leakage of any accumulated perspiration, which will contaminate food with high number of bacteria.

Unpackaged food or drink that has been served to a consumer in a restaurant should not be resold because it is very likely to have been contaminated by consumers. However, completely wrapped packaged food, other than potentially hazardous food, that has been served and has remained completely wrapped may be resold. This includes packaged condiments such as salt, sugar, pepper and butter, etc.

4.6 Time as a Safety Control

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1. Food premises may display or hold for service potentially hazardous food that is intended for immediate consumption at temperatures between 4^oC and 60^oC for a period of not more than 4 hours.
2. The food in item (a) above should, as far as possible, be identified or marked to indicate the time when it was removed from temperature control.
3. The food in item (a) above should be discarded if it has been displayed or held for service for more than 4 hours.

Rationale

Food premises should keep potentially hazardous food at either 4^oC or below, or at above 60^oC, during storage, display and transportation. However, it is acceptable for ready-to-eat potentially hazardous food to be kept out of temperature control (i.e. between 4^oC and 60^oC) for a limited time because pathogens (and / or toxin production) need time to grow to an unsafe level. According to US Food Code, the total time that a ready-to-eat potentially hazardous food can be kept out of temperature control is 4 hours. The total time is the sum of the time the food is at temperatures between 4^oC and 60^oC after it has been cooked (or processed) to make it safe. It does not include the time taken to cool the food after cooking provided the food has been cooled within the required time and temperatures (see "Cooling after Cooking" in paragraph 4.4.4 of this Chapter).

4.7 Food Packaging

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1. Packaging materials should be appropriate for the food to be packed and sufficiently durable to withstand the conditions of processing, storage and transportation.
2. Packaging materials should not pose a threat to the safety of the food to be packed.
3. Packaging materials and design should provide adequate protection for the food to be packed to minimize contamination and prevent damage.
4. Packaging of food should be carried out under hygienic conditions to protect the food from risks of contamination. Packaging and wrapping of food should be carried out under hygienic conditions by staff with appropriate training in food hygiene and food safety.
5. Packaging materials should be stored and handled under hygienic conditions to minimize the risks of contamination and deterioration.

Rationale

In addition to prolonging shelf-life, retaining quality and nutritional values as well as providing a water vapour / gas barrier, packaging is important for preventing food from being contaminated with chemicals, physical matters and bacteria.

Packaging materials should not endanger the safety and suitability of the food in contact with them. They should be suitable for the food to be packed, non-toxic, durable and clean. Chemicals from packaging materials should not migrate into the food; and if migration occurs, there should be no known toxic effects to consumers.

Packaging materials may contaminate food if they are not clean. They should thus be kept in their original packages and stored in clean areas where they are not exposed to risks of contamination.

4.8 Food Transportation

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1. Food during transportation should be protected from risks of contamination:
   1. food transportation units (including vehicles, trolleys, boxes, trays, crates, etc.) should be designed, constructed, maintained and used in a manner that protects the food from contamination;
   2. food transportation equipment that is intended to be in direct contact with food products should be constructed with non-toxic materials, which should also be easy to clean and maintain, such as stainless steel and food-grade plastic containers;
   3. during transportation, open food should be carried in enclosed vehicles, packed in covered containers or completely wrapped or packaged, to protect it against contamination by dust / dirt / fumes from vehicles or traffic;
   4. food and non-food products transported at the same time in the same vehicle should be adequately separated (e.g. wrapped or packed) to ensure that there is no risk of spillage or contact that may contaminate the food; and
   5. if different types of food are transported within a vehicle, precaution should be taken to avoid cross-contamination. For example, if both raw meat and ready-to-eat food are transported at the same time, they should be wrapped or kept in separate covered containers and places so that no cross-contamination can occur.
2. Food business operators should, when transporting potentially hazardous food:
   1. keep the food at or below 4^oC, or at above 60^oC;
   2. ensure that the food which is intended to be transported frozen remain frozen during transportation; and
   3. preferably, transport potentially hazardous food that is required to be kept cold during transportation in vehicles fitted with refrigeration equipment. Alternatively, coolers, ice bricks or other means may also be used to keep food cold during transportation. However, they should be used only temporarily because they cannot help lower the temperature.

Rationale

Transportation of food provides a significant opportunity for contamination and spoilage. Contamination may occur if food is carried in dirty or inappropriate containers or vehicles, or is transported together with toxic chemicals, or is inadequately covered, or packaging becomes damaged by poor handling. A further risk is introduced if potentially hazardous food is transported under ambient temperature that encourages growth of pathogenic bacteria.

4.9 Food Disposal

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Food that has been found or suspected to be unsafe or unsuitable (e.g. food that is subject to recall or has been returned, temperature abused, contaminated or damaged) should be rejected or identified (e.g. marked, labelled, kept in a separated container or isolated area), kept separately and disposed of as quickly as possible. It should never be available for human consumption.

Rationale

Food intended for disposal should be kept separate so that it is not accidentally sold or used.

4.10 Use of deep-frying oil

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Food traders are recommended to follow the advice below on the use of deep-frying oil.

1. Before deep-frying
   1. minimise moisture on the food surface; and
   2. proper use of breadcrumbs or batter.
2. During deep-frying
   
   1. control the oil temperature between 150°C and 180°C.
3. After deep-frying
   1. remove residues in deep-frying oil;
   2. lower the oil temperature setting to 120-130°C when the fryer is idle;
   3. season after deep-frying as far as possible;
   4. cover the fryer after it is turned off;
   5. clean the fryer regularly; and
   6. if the level of deep-frying oil is too low, top up fresh oil as appropriate, but not as a means of diluting or prolonging oil use.
4. Changing oil

   When any of the following conditions occur in deep-frying oil:

   1. having an unusual colour or odour;
   2. starting to smoke;
   3. starting to foam.

Rationale

During the deep-frying process, oil is exposed to high temperatures in the presence of oxygen in air and moisture in food. This results in chemical compounds that can accelerate the deterioration of oils and may affect quality of oils as well as food safety. When the deep-frying oil is used repeatedly, both the deep-frying oil and deep-fried food would gradually become darker in colour and give off a rancid odour. Besides, using an excessively high temperature (>180^oC) accelerates the deterioration of deep-frying oil, however, using too low a temperature (<150^oC) increases oil absorption into deep-fried food.

CHAPTER III

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