Ume boshi

Ume boshi

Ume boshi is the Japanese name given to a particular type of salted plum which has been salted, pressed and partially dried.

Ume are the fruit of a distinct tree species (prunus mume) which is related to both plum and apricot trees. The tree’s flowering in late winter and early spring is highly regarded as a seasonal symbol.

Boshi, derived from the Japanese word ‘hoshi’, simply means, ‘dried’.

Ume boshi are traditionally eaten in Japan to aid digestion, prevent nausea and reduce systemic toxicity, (good for hangovers). They are also thought to combat fatigue and were historically given to samurai as part of their field ration.

While ume trees grow wild throughout the country, the center of Japan’s pickled plum industry is in Wakayama Prefecture on Japan’s main island of Honshu. The area’s mild temperatures, plentiful rain fall and sheltered geographic location provide perfect growing conditions, resulting in the finest ume orchards with the most abundant fruit in the country.

The plums are picked around the end of June, when they are still green and their juice is at its peak of acidity. They reach their full size at the same time and must be picked within a week or two. Any delay means the plums will begin to ripen, reducing their acidity, flavor, and medicinal qualities.

Next, the plums are washed and then soaked overnight in water to remove any bitterness. The following day they are placed in large vats. A layer of plums is topped with a layer of sea salt, followed by another layer of plums and so on until each vat is filled. The salt content is about 12% and as the salt draws out the juice from the plums a flat pressing lid topped with a heavy weight is placed on the plums to keep them submerged in the liquid.

The plums are left to ferment for about a month until the end of July (the end of the rainy season) when they are taken from the vats, placed on wooden racks and left outside to dry for four to seven days, depending on the weather. The remaining salty/sour liquid is called Ume-zu, rich in citric acid and polyphenol, was traditionally taken as a tonic.

Although the basic ume boshi are now ready to eat they are often considered too salty and are usually put through a further stage to improve the taste.

Most commonly the ume boshi are soaked for a week in plum vinegar which has been infused with red shiso (perilla) leaf, giving them a dramatic deep red colour and the unique scent of shiso. Other common flavors include honey and dashi.

Following this process the ume boshi are removed from the vinegar and packed for sale.

This process of pickling is technically known as ‘lactic-acid fermentation’, one of the oldest and safest ways of preserving food. The secret to making good ume boshi is getting lactic-acid-forming bacteria to grow before other bacteria have a chance to multiply. Lactic-acid bacteria are salt-tolerant while other undesirable bacteria are not. To establish beneficial bacteria, traditional makers use the proper amount of salt, and store the fermenting plums in a cool, dark place. Lactic-acid bacteria multiply rapidly under these conditions.

Once flourishing, they produce enough lactic acid and carbon dioxide to create an acidic environment that further inhibits the growth of undesirable microorganisms and enzymes. The carbon dioxide contributes to favorable low oxygen conditions which further stimulate the growth of lactic-acid bacteria.

All our ume boshi are from Wakayama prefecture, produced using this traditional method.

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