sake, particularly artisanal ones. The most visible symbol of this is the (), a globe of cedar leaves traditionally hung outside a brewery when the new sake is brewed. The leaves start green but turn brown over time, reflecting the maturation of the sake. These are now hung outside many restaurants serving sake. The new year's sake is called ('new sake'), and when initially released in late winter or early spring, many brewers have a celebration known as (warehouse opening). Traditionally sake was best transported in the cool spring to avoid spoilage in the summer heat, with a secondary transport in autumn, once the weather had cooled, known as ('cold wholesale distribution')—this autumn sake has matured over the summer. Storage Sake is sold in volume units divisible by (one gō), the traditional Japanese unit for cup size. Sake is traditionally sold by the -sized cup, or in a (one shō or ten )-sized flask (called an , or 'one shō-measure bottle'). Today sake is also often sold in bottles, which are divisible into four . Note that this is almost the same as the standard for wine bottles, which is divisible into four quarter bottles (187ml). Particularly in convenience stores, sake (generally of cheap quality) may be sold in a small bottle or a single serving (one gō) glass with a pull-off top ( ). Generally, it is best to keep sake refrigerated in a cool or dark room, as prolonged exposure to heat or direct light will lead to spoilage. Sake stored at a relatively high temperature can lead to the formation of diketopiperazine, a cyclo (Pro-Leu) that makes it bitter as it ages Sake has high microbiological stability due to its high content of ethanol, but incidences of spoilage have occurred. One of the microorganisms implicated in this spoilage is lactic acid bacteria (LAB) that has grown tolerant to ethanol and is referred to as -bacteria. Sake stored at room temperature is best consumed within a few months after purchase. Sake can be stored for a long time due to its high alcohol content and has no use-by dates written on the bottle or label. However, there is a best before date for good drinking, and it depends on the type of sake, with the typical twice-pasteurized sake having a relatively long best before date. According to major sake brewer Gekkeikan, the best before date when unopened and