processblanching

Process blanching is a heat treatment used in food processing to inactivate enzymes, reduce microbial load, and prepare plant-based materials for subsequent processing such as freezing, canning, or dehydration. The term typically refers to brief exposure of vegetables, fruits, legumes, and herbs to hot water or steam, followed by rapid cooling.

The two most common methods are hot water blanching and steam blanching. In hot water blanching, product is immersed in water at temperatures around 85 to 100°C for short times, often from 30 seconds to several minutes depending on the item’s size and tissue. Steam blanching uses high-temperature steam, commonly around 95 to 100°C, with similar deactivation goals. After blanching, rapid cooling is used to halt heat transfer and preserve color and texture. Pre-washing, cutting, and uniform sizing improve process consistency.

The primary purpose of process blanching is to inactivate enzymes such as polyphenol oxidase and peroxidase that cause browning and quality deterioration. It also reduces surface microbial load and prepares products for reliable downstream processing. Blanching can help retain color and aroma, ease peeling, and improve subsequent dehydration or freezing performance. However, it does cause some loss of heat-sensitive nutrients, notably vitamin C, and can alter texture if overextended.

Equipment ranges from batch kettles and immersion blanchers to continuous belt or tunnel systems. Process control centers on timing, temperature, product size, and blanching method; some processes also use acidulants or anti-browning agents to enhance quality. Efficiency considerations include water and energy use, as well as minimizing nutrient loss and texture damage.

See also: blanching, food processing, thermal processing, enzymatic browning.