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Jithendra Nath: For hoteliers, what are the points to be concerned in terms of free radicals and carbon content for regenerated oils?
Nina Da-Costa: Let’s start by having a fundamental understanding of oil chemistry. Fats and oils exist as triglyceride molecules in food and body fat, which has three types of attached fatty acids, namely saturated – heat stable (e.g. butter, clarified butter (ghee), coconut); mono -unsaturated fatty acids (MUFA) – touted to be heart friendly (e.g. Olive oil, peanut oil, avocado, sesame, canola, etc) and Poly-unsaturated –fatty- acids (PUFA) – least heat stable (e.g. soya, corn, walnut, fish oils, etc).
When fats are attacked by oxygen, heat or light; they begin to break down mostly into free fatty acids and glycerol. This is when we say that oil is rancid due to the presence of free radicals, like what usually happens in reheated / regenerated oils. Those highest at risk are the PUFAs and transfats (altered fat) found in Hydrogenated Vegetable Oils (HVOs).
Some of the major health concerns of reheated oilsare production of free radicals which decrease the Vitamin E content of oils, production of 4-hydroxy- trans-2-nonenal (HNE) which leads to disorders of liver, Parkinson’s and Alzheimer’s disease, cancer, etc,. Carbon particles from burnt foods are also
carcinogenic.
High Smoking Point is an important consideration for selecting a cooking oil and is the temperatureat which a cooking fat or oil begins to break down to glycerol and free fatty acids, and produce bluish smoke ( acrolein). The smoke point of an oil does tend to increase as free fatty acid content decreases and degree of refinement increases. Oils which have a higher smoke point include avocado (271cC), high oleic canola (271cC), refined coconut (232cC), ghee (25cC), extra virgin olive oil (191cC), rice bran (254cC), refined sunflower (227cC), soya (238cC), etc.
Some useful practical suggestions for hoteliers to control the above include:
- Where possible, store all cooking oils in the refrigerator to avoid rancidity or in a cool dark place away from light and heat. During ongoing use,ensure that opened oil bottles are not stored close to heat sources.
- Avoid PUFAs in general for reheating purposes. PUFAs should not be used for reheating /cooking purposes after the expiry date. Ban transfats for cooking or frying purposes.
- Select oils for deep frying with depending on preference for higher smoking point, type of fat (as categorized above – saturated and MUFAs are preferred), preferably Vitamin E rich due to its anti- oxidant properties (e.g. olive, peanut, sesame,canola).
- Use deep frying systems with built in thermostats, where oil temperature can be regulated to a maximum of 180c C, on deep fat fryers. Fry food by placing it in hot oil to prevent it from soaking the oil.
- Turn off the heat after you are done cooking. Exposing oil to prolonged heat accelerates rancidity.
- Don’t mix different types of oil.
- Shake off excess batter from food before frying it, to prevent it from burning.
- Avoid iron or copper pots or pans for frying oil that is to be reused. These metals also accelerate rancidity.
- Use deep frying equipments with built-in filtration systems / micro filters which can remove sediment, carbon, FFA’s, OFA’s (peroxides, aldehydes, ketones), etc. For domestic purposes strain it through a few layers of cheesecloth to catch any food particles.
- Design recipes stating the types of oils for specific types of cooking purposes, with attempts to use healthier oils.
- Train staff on usage of oils. Discard oils which are discoloured, smoking, viscous and show foam presence and sediment.
A special note to food safety specialists Rancidity or oxidative breakdown including carbon particles must be addressed in the hazard analysis with specific controls identified. Peroxide Value (PV) and Free Fatty Acids (FFA) checks may be used to detect used oil quality just prior to discarding. On a quick note... Oil that’s well, ends well!
Jithendra Nath: How can caterers differentiate between food allergy and food intolerance, considering both as individual or customer’s problem?
Nina Da-Costa: The major differentiating factors of food allergy (FA) and food intolerance (FI) are the nature of symptoms and the onset time.
FA is an immunological response to specific proteins found in food caused by ingestion, inhalation or even by contact with the food. Common foods that can cause FAs include peanuts/tree nuts, milk, soy, wheat, crustaceans, etc.
FI is an inability to properly digest certain foods e.g. wheat, dairy, yeast, etc, due to a deficit of enzymes in the gastrointestinal (GI) tract. Hence small amounts of the food may be tolerated.
Symptoms of FA are typically immediate, dramatic and visible: coughing, sneezing, vomiting, migraines, watering eyes, rashes, swelling tissue, hives, etc. Associated GI responses like nausea, vomiting and diarrhoea can be delayed for hours or even days. Food allergy in some cases can be life threatening due to anaphylaxis (swelling of the tissues of throat, mouth and tongue) making breathing difficult. An adrenaline injection can help in treating the symptoms.
FI on the other hand is a slow onset reaction, hours, days or even weeks. The food passes through unprocessed, or lingers in the gut fermenting and producing excess ‘gas’. In some cases protein fragments rupture the lining of the intestine allowing foreign particles into the bloodstream. If left untreated they can lead to serious illness and tissue damage. Other symptoms detected long term may include gastro-intestinal (diarrhea, bloating, flatulence, etc.) and subsequent malabsorption problems like anaemia and osteoporosis,; respiratory
system distress including bronchitis, breathlessness, sinusitis, congestion ;miscarriage; infertility in males and females ; skin irritations from eczema to dandruff ; general ailments including headache, lethargy, migraine, inability to concentrate, sleep disorders, mouth ulcers, urinary problems, weight fluctuation and obsessive (addictive) eating , etc
FA is thought to be common because many people who have food intolerance mistake it to be an allergy. Most children may outgrow food allergies to milk, eggs, soya, wheat, etc. However those noticed in adulthood are likely to be lifelong allergies.
Jithendra Nath: Kindly advise the technical reason, for revising the cooking and reheating temperatures as the same (above 75ËšC with respect to time/earlier it was above 75ËšC and 83ËšC with respect to time)?
Nina Da-Costa: The earlier local regulation was based on the reheating temperature requirement of 82cC for Scotland. Reheating unlike cooking addresses the heat treatment of food which is already cooked/ high risk.
Spoilage microbes abound in raw foods creating a competition for pathogens to outgrow them while in cooked food the trend is reversed as spores easily take over due to germination and subsequent growth of vegetative cells eg. Bacillus cereus or Clostridium perfringens due to low numbers of spoilage microbes. Unfortunately most pathogens prefer anaerobic environments and cooking creates a likely anaerobic condition due to loss of oxygen in the cooking process. Hence a higher risk with pathogen growth in cooked food.
Heat processing of foods are based on what we call the D-value which indicates the time required to destroy 90 percent ( 1 – log )of the target or most resistant organism at a given temperature. Some of the indicator organisms used to validate the cooking processes are Salmonella to achieve a 7-log reduction or Listeria monocytogenes to achieve a 6-log reduction, depending on the regulations.
Hence based on the above, minimum temperatures according to the new rules, whether cooked or reheated does not make a difference , and a core temperature of minimum 75 Deg C or an equivalent can achieve the above. The new regulations probably are aimed at harmonizing temperatures based on the scientific logic of either of the heat treatment processes.
An important note to caterers and food service setups
Monitoring food temperatures at an instantaneous of 75 degrees Celsius is more effective than at an equivalent e.g. 70 degrees Celsius for two minutes.
Reheating may not be critical for foods which have been cooked, cooled and stored correctly and intended for quick service but more critical for foods to be held hot for longer periods.
