What to look out for when you have to store sake

2020 has been full of surprises, and their consequences remain to be fully seen. One knock-on effect of the closure of bars and restaurants and stay-home campaigns has been that many businesses – including brewers, wholesalers and retailers – have had to store their sake for longer than anticipated.

But never fear, the National Research Institute of Brewing (NRIB) is here with a pandemic update that highlights the effects of storage on different types of alcohol. They are supporting anyone who plans to store sake for long periods by working with appraisers at Regional Tax Bureaus across the country to evaluate the potential for generation of dimethyl trisulfide (DMTS) in sake, which they see as an indicator of how easily a sake may suffer from deterioration in storage (“ageing”, in a negative sense).

Their main method of evaluation is to force deterioration by keeping sake at 70°C (158°F) for one week, then measuring levels of DMTS. They hope the results of these tests will help anyone storing sake make decisions such as what order to ship out different types in, but warn that it does not predict the occurrence of hineka [老香, aromas negatively associated with “going off”].

The NRIB asks anyone with questions about the test results to first contact their local Regional Tax Bureau. In theory, only sake produced in BY2019 (the “brewing year” between July 2019 and June 2020) are subject to testing.

They also suggest a simple do-it-yourself test for seeing if a sake risks generating DMTS over time in storage. Dilute to the level at which the sake is sent to market and agitate well to incorporate air. Force deterioration by storing the sake at 45°C (113°F) for one month, 60°C (140°F) for two months, or 70°C (158°F) for one week. Then observe the colour and aroma of the sake – a photo shows deterioration-resistant sake as still clear, while a deterioration-prone one is light brown.

They also point out that the production process and quality of a sake influence how likely it is to deteriorate, and give a list of qualities they have found to be associated with resistance to deterioration:

• Made with rice with low sulphur content (low protein content)
• Product kept at low temperatures so the yeast does not die
• Dilution such as addition of alcohol or water
• Pressed without excessive pressure, or separate treatment of components found at the end of the pressing process
• Nama [生, unpasteurised] sake kept at low temperature
• Removal of yeast by taking out sediment
• Early pasteurisation, etc.

So based on these results, they generally recommend any sake that does not meet the above criteria to be shipped quickly and stored at low temperatures.

Noting that they have recently received many enquiries from distributors and the public about how long is too long to store sake, they also include a number of links to other pages and documents.

• Alcohol FAQ: Storage requirements for sake depend on the type, but as a general rule if bottles are resealed after opening they should last a month.[*] Low-aroma types like futsūshu, honjōzō and junmai can be stored at room temperature so long as they are kept away from light, but types with more delicate aromas such as ginjō or junmai ginjō are more vulnerable to deterioration and should preferably be kept in a cool place with particularly aromatic ones refrigerated.[**]
• Sake Sales Support News No. 44: I found some old sake, can it still be drunk? Old sake shouldn’t cause any health problems, but it may have deteriorated during storage due to oxidation, temperature or light. Brewed drinks contain a wider range of compounds are therefore more vulnerable to deterioration than brewed drinks. Brewers and distillers bottle and release their products when they are in peak condition, so they may be past their peak if stored for a long time at home. Some people like sake aged in this way and some do not, so it’s up to your personal preference. The colour change seen in sake is due to the Maillard reaction, which occurs between sugars and amino acids. The longer the sake is stored the more the reaction progresses, and proteins or pigments in the sake may come out of solution and create haziness or sediment. The aroma and flavour changes to become like shaoxing wine.

The NRIB also plans to publish a leaflet on sake storage soon, and invite anyone with questions to contact them.

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* This is not my experience with sake – many more aromatic ones start to change within a few days. I have had a few that have survived well for a month (usually sealed with a wine saver/vacuum sealing device) but I’d say they’re the exception. It may be that I’m getting ones that have been stored for longer before I get them.

** Japanese often includes daiginjō in ginjō in contexts like these.

There was a lot more on DMTS, which I may cover in a future translation!

Links

• Original article (Japanese, National Research Institute of Brewing, undated)
• National Research Institute of Brewing (Japanese)
• National Research Institute of Brewing (English, less content and less frequently updated)