Key Takeaways
- Blanching involves briefly boiling food and then rapidly cooling it in ice water, while parboiling only involves the boiling step.
- Blanching is often used for fruits and vegetables to improve color and texture, while parboiling is typically used to partially cook foods before using another cooking method.
- Blanched foods are usually mildly cooked, whereas parboiled foods are considered pre-cooked.
The terms blanching and parboiling are frequently used interchangeably, although there is a difference between them. Blanching refers to the method of quickly dipping a food item in boiling water and then rapidly chilling it by dropping it into ice water. On the other hand, parboiling refers to the rapid boiling process but does not include the rapid chilling step. Parboiling is often used to pre-cook a food item that will then be cooked in a different way, such as boiling, stewing, grilling, or stir-frying. Parboiled rice is the best example of a parboiled product. Blanched food is an uncooked or mildly cooked product, while parboiled food is a pre-cooked product. Both cooking methods are utilized in home cooking and the food industry and are closely interconnected.
What is Blanching?
Blanching is the process of boiling food in 100°C water for a short time (1-2 minutes) and then immediately placing it in ice-cold water to halt any further nutritional losses and cooking. Some blanched vegetables need to have excess water squeezed out before consumption. It is often used for fruits and vegetables that will be eaten raw or used for salad preparation. This technique is used to deactivate color-changing enzymes such as polyphenol oxidase enzyme. Blanching can also be used to remove off-color and off-flavors (bitterness) from foods and to soften vegetables before roasting them.
What is Parboiling?
Parboiling is typically used to cook an item to speed up the cooking time for the subsequent cooking method. The food items are put into boiling water and cooked until they begin to soften, and then removed before they are fully cooked. Parboiling is often used to partially cook or pre-cook a food item which will then be cooked in a different way. Parboiling differs from blanching, as one does not rapidly cool the food items using ice water after removing them from the boiling water. Raw rice or paddy is parboiled, and this process usually changes the color of rice from white to light reddish. Approximately half of the world’s paddy production is parboiled, and the treatment is practiced in many parts of Asian and African countries, such as Sri Lanka, India, Bangladesh, Pakistan, Malaysia, Nepal, Myanmar, Guinea, South Africa, Nigeria, and Thailand.
What is the difference between Blanching and Parboiling?
Blanching and parboiling processes may have substantially different cooking conditions and some organoleptic properties of finished products. These differences may include:
Definition of Blanching and Parboiling
Blanching: Blanching means to peel, remove by scalding, or immerse temporarily in boiling water.
Parboiling: Parboiling means to boil until partially cooked or boil for half the time of cooking.
Characteristics of Blanching and Parboiling
Purpose
Blanching: The objectives include enhancing the color of fruits and vegetables, preventing enzymatic browning, deactivating undesirable enzymes, making peeling easier, softening vegetables before roasting them, and reducing or removing undesirable strong odors (e.g., onion, cabbage) or setting the color of fruits and vegetables.
Parboiling: The objectives include speeding up the cooking time for the subsequent cooking method, increasing the nutritional value of the food (e.g., rice), and increasing the shelf-life of the product. Rice is parboiled to enhance texture, increase the milling yield, and reduce head rice loss.
Processing Steps
Blanching: Two basic steps of blanching are boiling and rapid cooling.
Parboiling: Three basic steps of parboiling are soaking, steaming or boiling, and drying.
Use of Food Additives
Blanching: Sometimes, calcium is added to reduce the softening of vegetables, and magnesium salt is added to prevent degradation of chlorophyll or retention of green color.
Parboiling: Food additives are not commonly used.
Time and Temperature Conditions
Blanching: The food is boiled for 30 seconds to 1 minute and immersed in 0-4°C water. Hot water at temperatures ranging typically from 70°C to 100°C is used for boiling.
Parboiling: Food is boiled for 3-20 hours depending on the method of parboiling, such as the traditional method or modified high pressure or steam generation method. Therefore, parboiling processes take more time and use high-temperature hot water or steam compared to blanching.
Cooking Stage of the Final Product
Blanching: Only the outermost layer of the food is cooked.
Parboiling: The entire food is cooked and is known as a pre-cooked product.
Nutritional Loss
Blanching: Some water-soluble and heat-sensitive nutrients can be destroyed (e.g., Vitamin C, Vitamin B).
Parboiling: Minimum nutritional losses can be observed. The nutritional value of parboiled rice is enhanced because vitamins in the husk are transferred to the center of the rice grain during the process of parboiling.
Chemical Changes
Blanching: Deactivation of enzymes is the major chemical change that occurs during blanching.
Parboiling: The starch content in parboiled rice becomes gelatinized, and then retrograded during storage. As a result of gelatinization, alpha-amylose molecules leak out of the starch grain complex. Cooling the parboiled rice storage brings retrogradation, where amylase molecules re-associate with each other and form a closely packed arrangement. This growth develops type 3-resistant starch, which can act as a prebiotic and benefit gut health in humans.
Examples of Blanching and Parboiling
Blanching: Mainly fruits and vegetables.
Parboiling: Mainly rice and nuts.
In conclusion, both blanching and parboiling involve boiling food. The difference is that blanched food is given an ice bath afterward to prevent overcooking, a step not required when parboiling. Thus, after the process of parboiling, the food is fully or partially cooked.
