The Role of Salt in the Production of Fish Paste Products

In the production of fish paste products (such as kamaboko, chikuwa, and crab sticks), salt plays more than just a flavoring role—it is the **”chemical and structural protagonist.”** Without salt, the characteristic firm, springy texture (known as “ashi”) cannot be achieved. Its primary roles can be summarized in three key points: 1. Solubilization of Salt-Soluble Proteins (Most Important Role) Among the proteins that make up fish muscle, “salt-soluble proteins” like myosin and actin are insoluble in water but soluble in saltwater. • Process: Salt is added to the minced fish and kneaded in a process called “salt kneading.” • Phenomenon: Salt breaks down muscle structure, causing proteins to dissolve outward, forming a highly viscous paste-like substance. • Result: Heating this paste causes proteins to form a mesh-like structure, creating that distinctive texture (chewiness). 2. Improved Moisture Retention When salt interacts with proteins, it alters the charge of protein molecules, enabling them to hold onto more water. • Moistness: Prevents moisture separation during heating, maintaining a juicy and smooth texture. • Yield: Prevents water loss during manufacturing, preserving product volume. 3. Enhanced Shelf Life and Flavor Enhancement It also fulfills the standard roles in food science. • Preservative Effect: By lowering water activity, it inhibits microbial growth and extends shelf life. • Flavor Contrast Effect: It enhances the fish’s natural umami while balancing flavors with seasonings like sugar. Salt Concentration Guidelines for Paste Products Generally, a salt content of around 2% to 3% is considered necessary to achieve both flavor and elasticity. While recent health trends demand “reduced salt,” excessive reduction weakens elasticity. Manufacturers are therefore focusing on innovations like using potassium salts and ultrasonic technology.

How Low-Salt Fish Cakes Maintain Their Elasticity

Manufacturers have overcome the physical barrier that “reducing salt = loss of elasticity” through a scientific approach. The key lies in the presence of “helpers” that substitute for salt (sodium chloride). The main techniques for maintaining elasticity in low-salt fish cakes are as follows: 1. Replacement with potassium chloride, etc. This is the most common method. It utilizes other mineral components that, like salt (sodium chloride), have the ability to dissolve proteins. • Potassium chloride: It has the ability to dissolve myosin while reducing saltiness (sodium). However, it has a distinctive bitterness, so it is common to adjust the flavor with other seasonings. • Calcium and magnesium salts: These also support strengthening the protein network structure. 2. Utilizing Polyphosphates Polyphosphates possess a powerful effect of loosening protein bonds, making them more soluble in water. • Even with a small amount of salt, polyphosphates assist in efficiently creating a “meat paste.” • They also significantly enhance water retention, helping maintain a firm, springy texture. 3. Selecting High-Quality “Fish Paste” This strategy relies on maximizing the inherent potential of the raw materials themselves. • Freshness: Fresh fish exhibit minimal protein denaturation, enabling strong binding even with low salt content. • Species Selection: Generously using premium fish like threadfin bream, which naturally possess strong “texture (elasticity),” compensates for structural weaknesses. 4. Physical and Scientific Support Beyond additives, manufacturing processes incorporate specialized techniques. • pH Adjustment: The pH of the meat paste is finely tuned to create an environment where proteins most readily form a mesh-like structure. • Enzyme (Transglutaminase) Addition: An enzyme that bonds proteins together like glue is added to artificially reinforce the mesh structure. • Heating Temperature Control: Adjusting the duration of the low-temperature resting period (“settling” process) maximizes the development of the protein network. Fun fact: Recent technological advancements include research using **ultrasound** to physically promote protein solubilization. We are now on the cusp of an era where “elasticity can be achieved without salt.”

Differences in Mixing Methods by Surimi Product Type

In surimi-based products, the mixing (kneading) method must be adjusted by product type because the target texture, air incorporation, and gel structure differ significantly.
From a quality control perspective, this is a critical control point.

🔷 Basic Concept by Product Category

Product Type	Target Texture	Air Incorporation	Mixing Intensity	Temperature Control	Typical Equipment
Kamaboko	Firm, dense gel	Very low	Medium–High	Strict	Silent cutter
Chikuwa	Elastic + grilled texture	Low	Medium	Strict	Silent cutter
Satsuma-age	Soft, fluffy bite	Moderate	Medium	Moderate	Mixer
Fish ball	Very strong elasticity	Minimal	High	Strict	High-speed cutter
Hanpen	Very soft, foamy	High	Low–Medium	Low temp	Foaming mixer

Key Differences in Mixing by Product

① Kamaboko-type Products (Steamed surimi products)

Objective: Strong and uniform gel formation

Mixing Conditions

• Vacuum or minimal air incorporation
• High-speed cutting
• Strong salt grinding (shio-zuri)
• Strict temperature control (≤10°C)

Standard Process

1. Coarse chopping
2. Salt grinding (high speed)
3. Addition of seasonings/starch (medium speed)
4. Final mixing (low speed)

Technical Focus

• Maximize myosin extraction
• Uniform hydration
• Air bubbles are defects

👉 Most “gel-oriented” mixing profile

② Chikuwa

Objective: Elastic texture plus good grilling performance

Mixing Characteristics

• Similar to kamaboko
• Slightly softer formulation
• Slightly higher moisture

Key Points

• Proper adhesion during molding
• Consider shrinkage during grilling

👉 A derivative of the kamaboko mixing approach

③ Satsuma-age (Important for your application)

Objective: Fluffy texture with clean bite and good frying performance

This category differs significantly.

Typical Mixing Conditions

• Moderate air incorporation allowed
• Medium mixing intensity
• Temperature tolerance: up to ~10–15°C
• Often includes vegetable mixing

Recommended Process

1. Salt grinding (medium speed)
2. Add seasonings and starch (medium speed)
3. Add vegetables (low speed, short time)

Technical Characteristics

• Overmixing → rubbery texture
• Zero air → heavy/dense texture
• Prevent vegetable breakdown

⭐ Quality Balance for Satsuma-age

Parameter	Too Strong	Optimal	Too Weak
Mixing	Rubbery	Fluffy	Water separation
Air	Oil splashing risk	Light texture	Dense/heavy
Temperature	Gel damage	Stable	Low viscosity

④ Fish Balls (Especially in Asia)

Objective: Extremely strong elastic “QQ” texture
Mixing Conditions
Intensive salt grinding
High speed and long duration
Vacuum strongly recommended
Strict temperature control (≤8–10°C)
Characteristics
Maximum protein extraction
Maximum hydration
Very fine and uniform structure
👉 Even more aggressive than kamaboko mixing

⑤ Hanpen

Objective: Light, sponge-like texture

Mixing Conditions

• Foaming process
• High air incorporation
• Low shear
• Low temperature

Typical Equipment

• Continuous foaming mixer
• Whipping mixer

👉 Opposite philosophy from kamaboko

📊 Critical QC Control Indicators

✔ Key Mixing KPIs

Parameter	Kamaboko	Satsuma-age	Fish Ball
Final temperature	≤10°C	≤15°C	≤10°C
Salt grinding time	Long	Medium	Longest
Vacuum	Recommended	Optional	Strongly recommended
Air content	Minimal	Moderate	Minimal
Specific gravity	High	Medium	High

✔ Common Factory Issues

Kamaboko

• Weak gel → insufficient salt grinding
• Sponge holes → air incorporation

Satsuma-age

• Oil splashing during frying → too much air
• Heavy texture → overmixing or insufficient air
• Vegetable water release → improper late-stage mixing

Fish balls

• Poor elasticity → temperature rise
• Rough surface → insufficient hydration

🎯 Summary (Most Important Point)

Surimi mixing falls into three fundamental categories:

🟥 Strong gel type

• Kamaboko
• Fish balls→ Intensive salt grinding + low temperature + minimal air

🟨 Intermediate type

• Satsuma-age→ Moderate mixing + controlled air + vegetable care

🟩 Foamed type

• Hanpen→ Air incorporation is primary