Pasteurization in Sake

## An Ancient Innovation

{{glossary:hi-ire}} (pasteurization) is the process of heating sake to approximately 60-65 degrees Celsius to deactivate enzymes and kill bacteria. Remarkably, Japanese brewers practiced hi-ire as early as the 16th century — three hundred years before Louis Pasteur developed the concept for wine.

## Why Pasteurize

Without hi-ire, the enzymes in sake continue working: amylases convert remaining starch to sugar, and proteases break down proteins. This ongoing activity changes the flavor over time, potentially creating unwanted sweetness or off-flavors. Pasteurization freezes the sake's profile at the point the brewer considers optimal.

## The Double Standard

Most sake undergoes hi-ire twice. The first pasteurization occurs after pressing and before storage, stabilizing the sake for aging. The second occurs before bottling, ensuring no microbial activity during distribution. This double treatment provides maximum stability for the supply chain.

## Modern Methods

Traditional hi-ire involved passing sake through a coiled pipe submerged in hot water. Modern plate heat exchangers achieve faster, more precise temperature control with less thermal damage to delicate aromas. Some breweries use bottle pasteurization, heating filled bottles in a water bath for exact timing control.

## Unpasteurized Variants

{{glossary:namazake}} skips both pasteurization steps. Nama-chozo skips the first (stored raw, pasteurized before bottling). Nama-zume skips the second (pasteurized after pressing, bottled raw). Each variant offers a different balance between freshness and stability.

## The Trade-off

Hi-ire provides stability at the cost of some freshness. The volatile compounds that give namazake its lively character are partially diminished by heat. However, well-executed pasteurization preserves the vast majority of a sake's aroma and flavor while ensuring consistent quality from brewery to consumer.