Rare Blog of a Novice Brewer

Learn about the next generation of sake brewing, evolving with IoT technology. We will introduce how ESP32 and sensors are used to measure the temperature, humidity, and CO2 of koji and fermentation in real-time, and how this data is centrally managed with Google Sheets. We will also explain how to achieve optimal brewing management based on this data.

A micro-brewery run by a single person is combining Arduino, Wi-Fi sensors, Google Spreadsheet, and the TILT hydrometer to manage brewing in real-time. We introduce a new sake brewing site that fuses the craftsman's intuition with IoT.

Managing the Koji Room with IoT! "Koji" is a crucial element indispensable for sake brewing. The quality of koji directly impacts the taste of sake, so it's no exaggeration to say that sake brewing is koji making. As the quality of sake depends on the temperature control of the koji room (kojimuro), we have introduced a self-made temperature control system in our koji room to achieve a more precise koji production environment. Here, we will introduce the mechanism and the process leading up to its implementation in detail. Why Temperature Control in the Koji Room is Important In sake brewing, koji plays a central role in fermentation. The enzymes produced by koji mold proliferating on rice convert starch into sugar, which eventually leads to alcohol fermentation. In the koji room where koji is cultivated, temperature, humidity, and carbon dioxide concentration significantly influence the quality of the koji. Especially for sake koji, temperature control is much more critical compared to koji used for miso or soy sauce.If you take your eyes off it for even a moment and the internal temperature rises too much, the koji mold can die or unwanted bacteria can grow, ruining the precious koji. To consistently produce high-quality koji suitable for sake brewing, meticulous 24-hour management is essential. In the past, when precise temperature control was not as advanced, koji production relied on human effort. From seeding to final koji, frequent movement between locations was necessary to monitor the growth environment and manage the temperature. The Reality That Commercial Koji-Making Machines Cannot Cope With There are specialized machines for making koji, called koji-making machines.They have a relatively simple mechanism that combines a constant temperature environment with heaters, automatically managing the koji room environment. Household versions can be found for tens of thousands of yen, but for sake brewing, koji is sometimes needed in units of 100 kg, so a machine of a certain scale is required. Even a simple commercial koji-making machine costs about 200,000 yen, and a high-performance machine that can perfectly control temperature and even produce a special type of koji called "tsuki-haze" used for Daiginjo sake costs a whopping 4 million yen per unit. Tsuki-haze refers to a state of koji where the hyphae of the koji mold spread only on the surface of the rice grains and do not penetrate deeply inside. It is an essential technique for brewing refined and smooth-tasting Daiginjo sake. While high-performance koji-making machines are excellent in that they can automate this management, they are simply out of reach for a small brewery like ours. Moreover, our brewery is a renovated private house. It's questionable whether large machinery could even be brought in through the entrance, so it was immediately rejected. First, I DIYed a Koji Room I built a wooden frame in a one-tatami mat space, enclosed it with insulation, applied FRP (fiber-reinforced plastic) for waterproofing, and installed a door. Paint might seem suitable for waterproofing, but it releases organic solvents during drying, and it's unclear how long it continues to do so, so it was rejected. On the other hand, FRP is used in brewing tanks, so there's no problem, and I'm already familiar with handling FRP, so I adopted it. Also, by installing shelves inside, the koji room's basic functions are fully established, and the production cost was only about 10,000 yen for materials, which could be sourced from a local hardware store. Inside, I ran electricity and installed LED lights. Initially, I tried managing it by manually controlling the heater's ON/OFF while checking temperature, humidity, internal temperature, and CO2 concentration on my smartphone using SwitchBot. This method had a major problem. Since someone had to check it regularly, if a check was inadvertently delayed, the internal temperature would rise too high, ruining the koji. Although it was partly due to my own inexperience in koji production, the lack of precision in temperature control directly led to poor koji quality. With this, it was impossible to produce koji suitable for sake brewing. Solved with IoT! Automatic Temperature Control System using Arduino (ESP32) The solution I came up with afterwards was IoT (Internet of Things) technology.I was originally interested in microcontroller control but hesitated because I couldn't write code, but with the advent of AI, the barrier suddenly lowered. So I adopted "Arduino," an open-source microcontroller board. It's a marvel used worldwide as an introductory tool for electronics, capable of reading sensor values and controlling external devices by programming it. Raspberry Pi is also famous for similar purposes, but its price has increased recently due to performance improvements. Therefore, I chose "ESP32," an Arduino-compatible board that can be purchased for about 2,000 yen on Amazon. Despite its compact size, it has built-in Wi-Fi communication capabilities, making it ideal for IoT projects.Sensors can also be acquired for around 1,000 to 5,000 yen each, so even with an internal temperature sensor, a temperature/humidity sensor, and a CO2 sensor, the total cost is about 10,000 yen. Adding the cost of building the koji room, a full-fledged smart koji production system was completed for a total of approximately 20,000 yen. System Mechanism The current koji room management system operates as follows:Each sensor connected to ESP32 constantly measures the internal temperature, room temperature/humidity, and CO2 concentration, and automatically transmits and records data to a server (Google Sheet operated on Google Drive) every minute via Wi-Fi. The accumulated data can be checked in real-time on a computer and also on a smartphone.When the internal temperature is low, the heater automatically turns ON to raise the room temperature.When the internal temperature rises, the system maintains the optimal temperature range by frequently turning the heater ON and OFF. This is arguably a function equivalent to the temperature control performed by expensive koji-making machines. The program is written in C++ language, but since I had never written a single line of code, I relied on Google's generative AI, "Gemini" (laughs).It's amazing how modern AI tools have made it possible for someone like me, who can't program, to build an IoT system. Thinking back 40 years ago, when I was in high school and taking computer classes, the teacher said that the more digits of pi you used, the more beautiful the circle became, and all I could say was "Oh, really?" It's an incredible evolution since then. Changes After Implementation Since activating this system, the koji management process has undergone significant changes.The biggest change is no longer needing to wake up in the middle of the night to check the koji's internal temperature. Furthermore, by observing the data trends, we can now predict when maintenance is needed, virtually eliminating late-night work. The quality of koji has also stabilized, allowing us to consistently produce koji of a standard suitable for sake brewing. While it certainly doesn't compare to a 4 million yen koji-making machine, reaching this point with an investment of 20,000 yen has been a highly meaningful endeavor for our small brewery. By combining traditional sake brewing techniques with modern IoT and AI technology, even small breweries can strive for quality improvement. This system demonstrates such potential. We will continue to accumulate data and pursue even better sake brewing in the future.