NOTES
An 18-month old rượu cái, or Vietnamese rice wine. Made entirely from glutinous rice fermented with microbials (yeast, fungi, bacteria). Distinguished by tart complex acidity and layered umami and nuttiness. Drinks similarly to an oloroso sherry or vin jaune and historically used in cooking (freshwater seafood or game) or enjoyed with before or during meals.
Rice varieties:
Yellow Flower Sticky Rice (nếp cái hoa vàng): a prized sticky rice strain known for its aromatic qualities and fermentation capabilities (low amylose content). Popular and well known in Vietnamese lowlands, it is considered to be a precious rice strain for special occasions – festivals, ancestor offerings, etc.
Purple Sticky Rice (nếp cẩm): considered superior and rare (during the period of Vietnamese monarchy, this rice was reserved exclusively for the emperor and royalty), it is a staple in H’mông cuisine and best cultivated in the highlands. When fermented, nếp cẩm yields flavors akin to port wine with distinct levels of amino acids and umami.
Production:
Like most traditional rice wines (rượu cái), production with rice cultivation. Rice varieties are selected based on terroir (whether grown in highlands or lowland rice paddies), amylose content, and bran structure (impacts amino acid levels). Khà is a combination of nếp cái hoa vàng (lowland variety with low amylose content) and nếp cẩm (highland variety with higher amylose content but more intact bran structure for amino acid integrity).
After harvest, both rice are milled to remove husk but are not polished. The rice is soaked, steamed, then inoculated with a mix of local microbes (fungi, bacteria, and yeast). Microbees include koji (aspergillus oryzae), but also include amylomyces, endomycopsis, rhizopus, and penicillium. The rice undergoes saccharification and solid-state fermentation until liquefaction and is formed into a mass to bring fermentation temperature up to 55-60C. This step yields a liquid of 27-30 brix (over 300g/l sugar). Yeast converts sugar to alcohol during primary fermentation which continues for roughly 2 months. Once ethanol fermentation and primary fermentation is concluded, the resulting wine is roughly 15.3-15.7 ABV with nearly 30g/l of residual sugar.
The young wine is racked (to remove rice solids) and transferred to a solera-system of neutral wood and terracotta amphora for maturation and secondary fermentation. The wine is matured sur lies for a minimum of 18 months with batonnage (depending on the quality of wine, can occur weekly or monthly). This process also continues the breakdown of sugars to ethanol and builds flavor due to controlled oxidation and maillard reactions from amino acid production (from the breakdown of proteins via protease in fungi).
Maturation is not temperature controlled (winters go as low as 2-5C and summers go as high as 45C) and the wine does not age under flor. The result is a wine yellow in color with a marked maillard reaction.