September 18th， according to media reports， “oil-preserved” delicacies such as oil-preserved fish and oil-preserved cherry tomatoes are widely popular among many people. However， nutrition experts remind us that while oil-preserved dishes have a unique flavor， they should not be consumed in excess， as this may increase health risks such as high blood pressure.
The so-called “oil immersion” processing technique combines cooking and preservation. By immersing ingredients in edible oil， the physical barrier created by the oil reduces contact between the food and oxygen. This process inhibits microbial growth， slows down fat oxidation and enzymatic reactions， and effectively extends the shelf life of food.
Oil immersion is not a new cooking method; it has a long history in China， primarily for food preservation. For instance， the Yunnan region has a tradition of pan-frying meat until dry and then preserving it in oil. It is said that meat prepared this way retains its rich aroma and can last for years without spoiling.
In today’s era of advanced food preservation technologies， the preservation function of oil immersion has gradually weakened. However， the rich flavor it imparts to food remains highly appreciated. Compared to steaming， it offers a richer mouthfeel from the added oil， yet unlike deep-frying， it does not easily result in dry， tough， or greasy ingredients. Low-temperature oil immersion can also better release fat-soluble fragrant compounds from the ingredients and ensures that the aroma of aromatics like scallions and ginger penetrates more thoroughly. This creates a wonderful experience where the aromas of oil， the freshness of the ingredients， and the aromatics of the seasonings interweave. For this reason， dishes like oil-preserved mandarin fish and oil-preserved seabass have become signature offerings in many Cantonese restaurants.
However， improper consumption of oil-immersed dishes can lead to potential health concerns:
Firstly， it increases the intake of fat and calories. While the oil absorption of oil-immersed foods is lower than that of deep-frying， their overall fat content remains higher compared to cooking methods like steaming or cold dressing. Long-term or excessive consumption can lead to exceeding recommended daily fat and calorie intake. For individuals who need to manage their weight or regulate blood lipid levels， it is advisable to control the quantity and frequency of consumption.
Secondly， it may lead to the formation of trans fatty acids and oxidized oils. Although the temperature for oil immersion typically does not exceed 200℃ and the heating time is relatively short， vegetable oils are rich in unsaturated fatty acids， which can still produce a certain amount of trans fatty acids at high temperatures. Furthermore， conditions such as high temperature， exposure to oxygen， or repeated use of oil can cause oil oxidation， producing harmful substances. This not only reduces the nutritional value of the oil but may also increase the risk of chronic inflammation， cardiovascular diseases， and even cancer.
It is also important to note the extremely low risk of botulism contamination in oil-immersed foods. Botulism bacteria are anaerobic and can survive in the sealed environment of oil immersion. There have been reported cases abroad of botulism poisoning from consuming oil-immersed garlic; although the probability is very low， caution is still necessary.
Therefore， when enjoying oil-immersed delicacies， it is important to practice balanced eating. Control the fat content of other dishes within the same meal. For example， oil-preserved cherry tomatoes can be paired with boiled eggs and lettuce to create a sandwich with steamed buns， oil-free European bread， or whole-wheat toast. Oil-preserved fish can be accompanied by low-fat dishes such as cold salads or steamed dishes to avoid exceeding overall calorie intake.
