1. Overview

This technical reference manual provides a comprehensive description of the historical background, legal definitions, manufacturing processes, and raw material specifications of diluted-type soju (Heuiseok-sik Soju) — the category that defines the Korean spirits market.

Diluted-type soju is produced by blending food-grade ethanol (food-grade spirit) with purified water to achieve a target alcohol content, followed by the incorporation of functional additives designed to enhance organoleptic quality. This category accounts for the substantial majority of domestic soju market volume, and product differentiation is achieved through ingredient composition and process design.

2. Legal Framework and Liquor Tax Act Definitions

The manufacturing methods and ingredient usage standards for soju are governed by the Liquor Tax Act (주세법) and the Enforcement Decree of the Liquor Tax Act, Article 3 (Standards for Raw Material Usage and Filtration Methods).

Enforcement Decree of the Liquor Tax Act, Article 3, Paragraph 6 (Excerpt):

When manufacturing alcoholic beverages under Attached Table No. 3, Item (a)(3) of the Act, the amount of alcohol derived from the blended spirit (주정) or grain spirit (곡물주정) must be less than 50/100 of the total alcohol content of the final blended product. When manufacturing alcoholic beverages under Attached Table No. 3, Item (a)(8), the amount of alcohol derived from blended products under Items (a)(1) or (a)(4) must also be less than 50/100 of the total alcohol content.

※ Historically, distilled soju (증류식 소주) and diluted-type soju (희석식 소주) were classified as separate legal categories. Following subsequent legislative amendments, they have been consolidated into a single liquor category.

※ This manual addresses diluted-type soju exclusively. Distilled soju is reserved for separate technical review.

3. Historical Background

Traditionally, Korean soju was produced through the fermentation and distillation of grains such as rice. However, during the food shortage period of the 1960s, government policy prohibited the use of rice and other grains in soju production.

As an alternative, the diluted-type soju method was introduced — blending food-grade ethanol derived from starchy materials such as sweet potato with purified water. Because this approach lacked the distinctive aroma, umami character, and body associated with distilled soju, the incorporation of functional additives became essential to improve organoleptic quality.

Initially, saccharin was used as a sweetener, but it was subsequently banned due to safety concerns. Aspartame was introduced as a replacement, though its tendency to degrade during storage — resulting in diminished sweetness — prompted continued development of alternative sweeteners. Today, high-potency natural sweeteners such as enzymatically modified stevia and thaumatin are predominantly used.

4. Manufacturing Process Overview

The standard manufacturing process for diluted-type soju consists of the following sequential stages:

1. Spirit Sourcing and Incoming Inspection: Verification that food-grade ethanol (≥95% alcohol by volume) meets all applicable quality specifications.
2. Purified Water Production: Removal of residual chlorine from municipal tap water through activated carbon filtration or UV treatment, producing food-grade process water.
3. Alcohol Content Adjustment: Blending of food-grade ethanol and purified water to achieve the target alcohol by volume (ABV).
4. Addition of Distilled Soju Base (Optional): Incorporation of a small quantity of rice or barley distillate to supplement flavor complexity and mouthfeel.
5. Additive Incorporation: Addition and homogeneous blending of sweeteners, umami-enhancing compounds, functional ingredients, and other concept-driven additives.
6. Filtration: Removal of off-flavors and off-aromas using activated carbon or bamboo charcoal filtration; quality standardization.
7. Quality Control and Filling: Final ABV verification, sensory evaluation, bottle filling, and packaging.

5. Comparative Analysis of Key Product Ingredients

The table below presents a comparative analysis of label-declared ingredients for the top two market-share brands in the Korean diluted-type soju segment: Chamisul and Jinro Is Back (both by HiteJinro), and Chum-Churum (by Lotte Chilsung Beverage).

Ingredient / Specification	Chamisul (참이슬)	Jinro Is Back (진로 이즈백)	Chum-Churum (처음처럼)
Alcohol Content (%)	17.0	16.9	16.9
Purified Water	✓	✓	✓
Food-Grade Ethanol	✓	✓	✓
Fructose	Fructose	Fructose	Other Fructose
Distilled Soju Base	Rice distillate (domestic rice, 100%)	Rice distillate (domestic rice, 100%)	Rice & barley distillate (domestic, 100%)
Enzymatically Modified Stevia	✓	✓	✓
Steviol Glycoside	—	—	✓
Erythritol	✓	✓	—
Thaumatin	✓	✓	—
L-Arginine	—	—	✓
Filtration Method	Bamboo charcoal filtration (label-declared)	Not specified on label	Not specified on label

※ Ingredients are listed on product labels in descending order of quantity used. Detailed formulation ratios for trace additives are not publicly disclosed. As formulations are subject to change, the data above may differ from currently marketed products.

※ Chamisul explicitly declares a bamboo charcoal filtration step on its label. Jinro Is Back and Chum-Churum do not specify a filtration method.

6. Technical Characteristics of Raw Materials

6-1. Purified Water

All water used in food production must comply with the Drinking Water Management Act (먹는물관리법). The majority of soju manufacturers currently use municipal tap water (as opposed to groundwater) as their primary water source. Since municipal water contains trace residual chlorine for disinfection purposes, it is treated via activated carbon filtration or UV irradiation to remove residual chlorine prior to use in the production process.

6-2. Food-Grade Ethanol (주정)

Food-grade ethanol refers to edible ethyl alcohol (C₂H₅OH) produced through the fermentation of starchy substrates using yeast, followed by continuous distillation to achieve a purity of 95% or greater.

It is important to distinguish ethanol from methanol at the molecular level: methanol is not suitable for human consumption and is acutely toxic, causing irreversible vision loss and potentially fatal outcomes. Food-grade ethanol and industrial ethanol are clearly differentiated by raw material and manufacturing process; industrial ethanol is synthesized from petrochemical feedstocks such as naphtha and is categorically prohibited from use in food production.

6-3. Distilled Soju Base (증류식소주원액)

This refers to distillate obtained through the fermentation and distillation of grain-based substrates such as rice, barley, or sweet potato. When added in small quantities to food-grade ethanol, it imparts a soft, rounded flavor profile and improved mouthfeel, effectively counteracting the flat, austere character of neutral ethanol. The specific grain substrate used influences the sensory profile of the final product in subtle but meaningful ways.

※ Chamisul and Jinro Is Back: rice-based distillate (100% domestic rice)

※ Chum-Churum: rice and barley blend distillate (100% domestic grains)

6-4. Enzymatically Modified Stevia (효소처리스테비아)

Enzymatically modified stevia is a natural high-potency sweetener derived from the leaves and stems of Stevia rebaudiana Bertoni through extraction and purification. Its sweetness potency is approximately 200–300 times that of sucrose, with minimal bitterness and excellent sweetness persistence.

The enzymatic modification process involves the attachment of glucose units via α-glucosyltransferase, yielding a product with reduced bitterness and improved sweetness quality relative to unmodified stevia. In soju production, it is primarily used to mask the inherent bitterness of ethanol; its sustained sweetness through the finish is particularly effective in this application.

6-5. Steviol Glycoside (스테비올배당체)

Steviol glycoside is a natural high-potency sweetener refined to concentrate Rebaudioside A, the stevia glycoside with the most favorable sweetness profile. It is produced by hot-water extraction of dried stevia leaves, followed by adsorption resin treatment, recrystallization using methanol or ethanol, and a drying step.

6-6. Thaumatin (토마틴)

Thaumatin is a protein-based natural high-potency sweetener isolated by aqueous extraction and purification from the seeds of Thaumatococcus daniellii Benth, a plant native to the tropical rainforests of West Africa. It exhibits a high-quality sweetness profile free from bitterness and off-flavors, and is a relatively recently approved food ingredient.

6-7. Fructose / Other Fructose (과당 / 기타과당)

Fructose is a naturally occurring monosaccharide found in fruits. Under the Korean Food Standards Codex (식품공전), ‘fructose’ designates a product containing ≥98% fructose content, while ‘other fructose’ (기타과당) contains ≥35% fructose, with the remainder consisting of glucose, sucrose, and related sugars.

The primary function of fructose in soju is to impart sweetness that counterbalances the bitter and astringent qualities of ethanol. Published literature also indicates that fructose may accelerate alcohol metabolism, potentially contributing to hangover relief.

6-8. Erythritol (에리스리톨)

Erythritol (C₄H₁₀O₄) is a sugar alcohol produced through fermentation using yeasts such as Moniliella pollinis and Trichosporonoides megachilensis. Upon dissolution, it generates an endothermic reaction that produces a cooling, refreshing sweetness. In soju, it contributes to the mitigation of harsh alcoholic heat and an overall improvement in mouthfeel. It belongs to the same functional sweetener class as xylitol, another well-known sugar alcohol.

6-9. L-Arginine (L-아르지닌)

L-Arginine is an amino acid reported to promote the enzymatic breakdown of acetaldehyde — the principal metabolite responsible for hangover symptoms following alcohol consumption. It is commonly co-formulated with aspartic acid in commercial hangover-relief beverages. Its inclusion in Chum-Churum as a standalone functional ingredient suggests a deliberate hangover-mitigation differentiation strategy.

7. Additive Formulation Design Principles

The additive system of diluted-type soju is architected around three functional pillars:

• Alcohol Bitterness Masking: Utilization of high-potency natural sweeteners (enzymatically modified stevia, steviol glycoside, thaumatin, etc.) to neutralize the inherent bitterness of ethanol.
• Umami and Body Enhancement: Use of sugar alcohols (e.g., erythritol) and distilled soju base to build mouthfeel and depth of flavor.
• Product Differentiation and Functional Value-Add: Incorporation of concept-driven ingredients such as hangover-relief compounds (L-arginine, fructose) to establish category distinction.

When multiple ingredients serving the same functional role are combined, the intent is mutual complementation — compensating for sweetness imbalances or sensory gaps that can arise when relying on any single ingredient. Because each high-potency sweetener exhibits a distinct sweetness onset pattern, finish character, and degree of residual bitterness, the formulation developer must engineer the optimal combination to match the intended sensory target profile.

8. Summary Assessment

The analysis presented in this manual demonstrates that commercially available diluted-type soju products share a common structural foundation of food-grade ethanol and purified water, upon which each brand differentiates through a curated selection of high-potency sweeteners, sugar alcohols, distilled soju base, and functional amino acids — each calibrated to a specific product concept.

Raw material selection in this category extends well beyond simple flavor optimization. It encompasses a multi-dimensional evaluation of functional efficacy (e.g., hangover mitigation), cost-efficiency, regulatory compliance, and strategic alignment with the product’s market positioning. This reflects the quintessential multi-variable optimization challenge inherent to advanced food technology development.