Total Nitrogen (TN)
Total nitrogen
Japanese: 全窒素（ぜんちっそ）
Total nitrogen content in miso. An indirect indicator of protein content and quality standard baseline.
Total nitrogen is measured by Kjeldahl method or similar, representing all nitrogen compounds in miso. Since protein contains about 16% nitrogen, total nitrogen estimates protein content.
JAS standards classify miso grades by total nitrogen — higher values indicate more protein-rich miso. Reflecting raw material ratios and soybean quality, it also functions as a raw material management indicator. A fundamental food analysis metric guaranteeing quality through numbers.
The Kjeldahl method is the classical standard for total nitrogen measurement, widely adopted in the industry. Recently, near-infrared spectroscopy enables rapid measurement. Tracking total nitrogen consistently from raw materials to finished product ensures quality traceability.