Rare Blog of a Novice Brewer

This article provides an easy-to-understand guide on how to make sugar-free fermented anko (sweet red bean paste) using a rice cooker, yogurt maker, or pressure cooker. It also covers the benefits, ways to enjoy it, and tips for foolproof results, making it a comprehensive resource. Additionally, we will share insights from a brewery's perspective on the key points for choosing rice koji, which greatly influences the finished product.

Decomposition and Fermentation: There's Only One Difference "Decomposition" and "fermentation" are, scientifically speaking, exactly the same phenomenon. Both refer to the process where microorganisms attach to food and break down and alter its components.So what's the difference? The answer is simple: whether it's beneficial to humans, and that's it. I used to eat expired natto and cheese, thinking they were made by decomposition anyway, and ended up with stomach aches. No matter how beneficial the bacteria are said to be, it's possible that non-beneficial bacteria have attached themselves later, turning fermentation into decomposition. So, I should be more moderate with expired foods. Fermented foods like natto, cheese, miso, and soy sauce transform into foods that are beneficial for our bodies, with enhanced umami and nutritional value, thanks to the action of specific bacteria. On the other hand, when food forgotten in the back of the refrigerator "goes bad," wild bacteria are also actively at work. However, because the outcome is harmful to humans, it's called "decomposition."In other words, fermented foods can be seen as the culmination of human wisdom, having carefully selected "beneficial decomposition" over a long period of time. Common Mechanisms in Fermented Foods like Sake, Bread, and Cheese Understanding the mechanism of fermentation changes how you view everyday foods. When brewing sake, the term "kamosu" (to brew) is used.First, koji mold breaks down the starch (carbohydrates) in rice into sugar, and then yeast ferments that sugar into alcohol. This two-stage process produces that rich aroma and flavor.Bread is similar. Yeast consumes the sugars in flour, and the carbon dioxide gas produced in this process causes the dough to rise. "Secondary fermentation," where the shaped dough rises again, is also due to the action of the same yeast.The fluffy texture of baked bread can be said to be the result of the activities of unseen microorganisms. Cheese and natto are also products where specific microorganisms like lactic acid bacteria and natto bacteria have transformed the raw ingredients.The fundamental principle in all of them is the same: "bacteria breaking down organic matter." The "Life-Threatening Tastings" of Our Ancestors Created Today's Food Culture A symbolic episode of this is the origin of natto. A person in extreme hunger ate beans that had spoiled in the scorching sun, and surprisingly found them delicious.This is said to be the beginning of natto.It was precisely because it was a situation one would normally avoid that an accidental discovery was made. The Miraculous Moment the World's Oldest Alcohol, "Mead," Was Born Mead (honey wine) is indispensable when talking about the history of fermentation.It is known as the world's oldest alcohol, predating wine and beer, dating back approximately 8,000 to 10,000 years. There's a theory about its origin: a wild beehive fell into a puddle, and natural yeast attached to it, leading to natural fermentation.Someone accidentally passing by noticed the fragrant aroma, approached, and found a liquid mixed with honey. Normally, you wouldn't dare drink liquid from a puddle when you don't know what's in it, would you? It could even be animal urine... However, that person was apparently so intensely thirsty that they were resigned to death.Thinking, "I'm going to die anyway," they drank it and found it surprisingly delicious, experiencing the pleasant sensation of intoxication for the first time. This is said to be the beginning of mead, and by extension, humanity's encounter with alcohol. As this anecdote, which overlaps with the story of natto's discovery, suggests, many great discoveries in human food culture may have originated from chance encounters in extreme conditions. The Origin of "Honeymoon" Lay in Mead There's another interesting anecdote related to mead.That is the etymology of "honeymoon." In ancient Europe, there was a custom where newly married couples would gather honey themselves, brew mead, and serve the finished drink to family, friends, and acquaintances. Since mead takes about a month to mature, the first month after marriage is said to have become known as the "honey moon." Honey has long been a symbol of "fertility, prosperity, and love," and it seems that newlywed couples drinking mead also expressed a wish for a harmonious marriage and many children. It's deeply moving that such a warm culture of sharing carefully brewed alcohol with loved ones remains worldwide as the term for modern "honeymoon trips." From Kura-Tsuki Yeast to Kyokai Yeast: Technological Innovation in Sake Brewing In sake brewing, too, there is a history surrounding yeast, the main actor in fermentation. In old sake breweries, instead of sourcing yeast externally, they utilized "kura-tsuki yeast," which naturally inhabited the land and buildings of the brewery. It wasn't sold anyway (laughs). The unique yeast strains produced by the local climate, natural features, and building structures created the distinctive flavors of each brewery. The turning point came in the Showa era. The Brewing Society of Japan was established and collected and analyzed superior yeast from sake breweries across the country, successfully cultivating high-quality yeast strains.A system was then put in place to provide this "Kyokai yeast" to breweries nationwide. This initiative is said to have improved the overall quality of sake and significantly reduced inconsistencies in taste. The ability for any brewery to produce consistently high-quality sake greatly contributed to the spread and development of sake culture.However, some toji (master brewers) and breweries continue to adhere to kura-tsuki yeast or self-cultivated yeast, going against this trend. The attitude of not purchasing yeast from the association, but rather cultivating yeast by their own hands and imbuing the sake with characteristics unique to that land, can be seen as an attempt to preserve the essence of fermentation culture. A Long, Long Collaboration Between Microorganisms and Humans From the origin of natto to the world's oldest alcohol, mead, and up to modern sake brewing, the history of fermentation is a long history of collaboration between humans and microorganisms. Tiny, unseen microbes have transformed ingredients, created beverages, and fostered culture.We are able to enjoy these benefits thanks to our ancestors who, through countless stomachaches, identified and passed down "beneficial fermentation."The glass of sake you hold today is filled with such an ancient history of fermentation. Of course, I can only be grateful that I can brew sake thanks to the history cultivated by my predecessors.  

Sake is not just a simple "alcoholic beverage." First, it is a uniquely complex fermented beverage, starting from the starchy substrate of white rice, where multiple microorganisms divide roles to perform stepwise transformations. Let's unravel that fermentation process from the perspective of microbiology and biochemistry. 1. Koji-making Process: Building a Platform for Enzyme Production The first key to sake brewing lies in the koji-making process by Aspergillus oryzae (koji mold). It begins by scattering koji mold spores onto steamed rice that is firm on the outside and soft on the inside. The steamed rice, inoculated with tane-koji, is then cultivated in a koji room (koji-muro) with precisely controlled temperature and humidity for about 48 hours.During this time, the koji mold extends its hyphae into the rice grains and secretes a wide variety of hydrolytic enzymes. Particularly important is the production of amylases (α-amylase and glucoamylase) and proteases.α-amylase hydrolyzes the α-1,4-glycosidic bonds of starch in an endo-type manner to produce dextrin, and glucoamylase sequentially releases glucose from its ends.This two-stage saccharification reaction supplies fermentable monosaccharides to the yeast.Protease breaks down proteins into amino acids and peptides, serving as a nitrogen source for yeast in subsequent processes and acting as a precursor to umami components in sake. While using technical terms, essentially, koji mold breaks down rice, which is a lump of starch, into sugar, making it easier for the yeast in the next step to break it down into carbon dioxide and alcohol. 2. Shubo (Yeast Starter): Selection of Microbial Flora and Yeast Proliferation Next, koji obtained from koji-making, steamed rice, water, and yeast are brewed in a small tank to cultivate a high-density yeast culture solution called "shubo" (moto). In traditional kimoto and yamahai-moto methods, wild lactic acid bacteria (of the Lactobacillus genus, etc.) are naturally propagated, but this is rarely done in modern sake brewing.Instead, in the modern mainstream sokujo-moto method, instead of propagating lactic acid bacteria like in kimoto or yamahai-moto, brewing lactic acid is directly added. Homo-lactic acid fermentation by lactic acid bacteria (C₆H₁₂O₆ → 2CH₃CH(OH)COOH) rapidly lowers the pH of the moromi (main mash). This pH drop acts as a selective pressure, eliminating miscellaneous bacteria that are weak to acidic conditions, while giving an advantage to the proliferation of acid-resistant brewing yeast (Saccharomyces cerevisiae). At this stage, the yeast enters its exponential growth phase, increasing cell density in preparation for the subsequent moromi fermentation. The acidification of the moromi aims to eliminate miscellaneous bacteria that could negatively affect brewing by making the acidic environment unsuitable for their survival. In this environment, yeast, being strong against acid, can perform its function without being destroyed along with other miscellaneous bacteria. 3. Moromi Fermentation: A Globally Rare Fermentation Method Called Parallel Multiple Fermentation The greatest characteristic of sake is this concurrent saccharification and fermentation. Unlike beer, where saccharification and fermentation are separated, in sake, saccharification by koji and alcohol fermentation by yeast proceed simultaneously within the same tank. This is an extremely rare fermentation method among brewed beverages worldwide. The gradual addition of koji rice, steamed rice, and water in three stages ("hatsugoe," "nakagoe," and "tomegoe") during "sandan-jikomi" (three-stage preparation) is also to maintain the substrate concentration within an appropriate range relative to the yeast cell density and to prevent a decrease in yeast activity due to osmotic stress. Furthermore, this operation, combined with low-temperature, long-term fermentation (approximately 20-30 days), promotes the production of aromatic components (isoamyl acetate, ethyl caproate, etc.), forming a complex flavor profile. The central reaction of alcoholic fermentation is the production of ethanol via glycolysis (Emden-Meyerhof-Parnas pathway): C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂. The alcohol concentration at the end of fermentation reaches 14-20%, which is close to the upper limit of the yeast's own alcohol tolerance. Ultimately, the power of yeast transformed it into carbon dioxide and alcohol through fermentation, but as the alcohol concentration increases, the yeast also dies off. 4. Joso and Hi-ire: Termination of Fermentation and Stabilization of Quality Once the moromi has matured, it undergoes a solid-liquid separation process called "joso" to be separated into sake and sake lees, resulting in clear sake. Afterward, in most cases, hi-ire (pasteurization) is performed. Even after separation from sake lees, there are still living yeast cells, so a short-time heat treatment at 60-65℃ is carried out to inactivate residual wild yeasts and lactic acid bacteria, and to deactivate enzyme activity (especially residual amylase). This concept of pasteurization, a technology uniquely developed in Japan, is said to predate Western Pasteur (named after the person who elucidated the principle of wine making from grapes) by about 300 years. Sake fermentation is a precise biological process where microbiology, enzyme chemistry, and food engineering intersect. Koji mold, lactic acid bacteria, and yeast each occupy different spatiotemporal niches and cooperate to create that clear cup of sake. Although sake is consumed worldwide, the method of sake production is uniquely Japanese, as this story explains.