Test on Non-Stick Frying Pans: Heat Conduction Speed Varies by over 3 Times Use with Care Noting Divergence in Scratch Resistance & Durability
City dwellers are generally keen for efficiency even in their everyday chores. Non-stick frying pans, that are fast in heat conduction and easy to clean, are no wonder the handy choice of many in home cooking. A Consumer Council test has shown wide differences in their heat conduction speed and heat distribution – under the same hob heating, the samples varied by over 3 times in heat conduction speed, and a difference of up to 139°C in heat distribution when the sample is heated with induction hob. The test also found nearly 90% of the models were dissatisfactory in scratch resistance of the coating and, furthermore, care should be taken to ensure the loading strength of the handles to prevent deformation or damage when in use.
Among the 25 test models, 12 were with the traditional plain PTFE coating (without stone/particle pattern) priced from $115 to $2,388, and 9 with the stone/particle pattern coating from $70 to $1,598. In both types, the most expensive and the cheapest samples were also rated with a relatively high overall score of 4 points, reflecting that products with good quality and low price can be found in the market. For example, a model priced $150 with plain PTFE coating (without stone/particle pattern) scored the same 4 points as the model priced more than $2,000, but with even more steady performance across the test items. Consumers should shop around well before purchase. For the remaining models, 2 were with plain ceramic coating (without stone/particle pattern), priced from $799 to $999, and 2 were with net/honeycomb pattern coating, priced from $898 to $988, their overall score were 4 or 4.5 points.
In the test, some of the items were conducted and evaluated with reference to the European Standard EN 12983-1, and the British Standard BS 7069: the release of chemicals, heat distribution, heat conduction speed, handle temperature, abrasion and scratch resistance of coating, in addition to examiners’ assessment on cooking performance and ease of use. The result indicated that among 3 categories, namely the plain PTFE (or Teflon) coating, the stone/particle coating and the plain ceramic coating, each had 1 model rated overall a 4.5 points, 16 others scored 4 points and the 6 remainders scored relatively low from 2.5 to 3.5 points.
The models were heated on gas hob, induction hob and ceramic hob. The result showed that when using identical hobs, heat conduction speed of the models could vary by 3 times; when heated on induction hob, the time taken to reach 180°C differed from 1 min 14 secs to 5 mins 2 secs, varying by 3.1 times; with gas hob, the time varied from 1 min 31 secs to 6 mins 22 secs, a variation again of over 3 times; and with ceramic hob from 3 mins 35 secs to 10 mins, a difference of 1.8 times.
For the test on heat distribution, there was a vast difference among the models’ performance. Surface temperature difference in the models when heated on gas hob ranged from 25°C to 68°C while heated on induction hob the surface temperature difference was even from 40°C to 139°C, and in the case of ceramic hob the surface temperature difference from 20°C to 100°C. When handling food ingredients that require even heat distribution, like searing steak or making pancake, cooking technique of consumers would be put under test when using a frying pan with wider difference in surface temperature.
The result showed that when using non-stick frying pan on induction hob or ceramic hob, the models’ performance in heat distribution and heat conduction speed both varied in greater extent. Consumers therefore should choose according to the type of cooking hob they use at home to purchase respective non-stick frying pans that most suit their purpose.
The durability of a non-stick frying pan is another important factor to consider. The abrasion resistance of the coating including the ease with which the coating could be scratched and flaked off among the models varied considerably. According to the abrasion test result, 1 model of the plain PTFE coating and 2 with the net/honeycomb pattern coating were found to exhibit marked colour fading and reduced anti-stick performance, and thus were rated with a low 2.5 points.
In the test on scratch resistance, when forced with 3, 10 and 20 Newton to scratch the frying pan surface (i.e. the strength for removing stubborn stains with a hard object), near 90% (22 models) of the samples were found with their coatings flaking off, exposing the metal substrate of the frying pans when subjected to greater forces of 10 and/or 20 Newton – all with only 2.5 or 3.5 points in the rating.
In animal experiments, both chemical substances PFOA and PFOS that might be used in the process of making the non-stick coating have demonstrated to be hepatotoxic, reprotoxic and carcinogenic. Many consumers are concerned that once flaking off of the non-stick coating occurs and is used continually in food cooking may put their health in jeopardy. The test showed that the release of PFOA and PFOS in all samples was lower than the suggested upper limit of the German Federal Institute for Risk Assessment. Further, the release of metals was also lower than the Council of Europe’s recommended upper limit. Consumers therefore need not overly worried.
In the simulated loading test, each model was loaded with equivalent to 2 times the mass of water at the capacity of the sample to test the handle fatigue resistance by 15,000 times raising and lowering exercise. It was found in 2 models which loaded with 5.2kg and 5.5kg of water respectively and after some 13,000 and 4,600 cycles of raising and lowering the connection between the handle and the frying pan were broken, indicating that the handle fatigue resistance to be rather weak – with a score of only 3 and 2 points. Though the loading adopted for the test was higher than the standard requirement, consumers should use with care to avoid overloading and to minimize the risk of deformation of the handles or even causing damage.
The test also covered the handle temperature. 2 models’ helper handle and 5 samples’ metal screws on the handle were measured to exceed the upper temperature limit of the standard (55°C). In the case of 2 models, users were not reminded from the operation instructions, to employ heat protective equipment (such as oven mitts), thus scored only 2 and 2.5 points. The findings were referred to the Customs and Excise Department.
Consumers using non-stick frying pans should heed the following usage and maintenance:
- Use warm water with detergent, and sponge or cloth to clean the non-stick frying pan before using for the first time, never wash with metal scrub or coarse cleaning cloth to avoid scratching the non-stick coating;
- Never use high heat or temperature on an empty non-stick frying pan, put in first cooking oil or water and use low to medium heat for cooking;
- Sustained high temperature heating may shorten the life span of non-stick frying pans and may cause deformation in the shape of the pans;
- Avoid using sharp metallic spatula or fork, better use tools made of wood, plastic or silicone to stir the food;
- It's not advisable to leave food in the pan over a long period of time, remove the food and store it in a proper container;
- Leave the non-stick frying pan to cool off naturally by itself after use, rather than immediately filling it with cold water to avoid deformation due to abrupt change in temperature;
- Once the non-stick coating flaked off, the frying pan will gradually lose its anti-stick function, and consumer should stop using when the flaking off situation becomes serious.
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