Chinese cuisine 中國菜

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### **转谷氨酰胺酶（Transglutaminase，TG酶）详解**

转谷氨酰胺酶（Transglutaminase，简称TG酶或TGase）是一种能够催化蛋白质分子间或分子内交联的酶，通过形成**ε-(γ-谷氨酰基)赖氨酸异肽键**，改变蛋白质结构，广泛应用于食品加工、医药和生物材料领域。

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### **一、作用机制**
1. **催化反应**：
- 将蛋白质中的**谷氨酰胺残基**（供体）与**赖氨酸残基**（受体）连接，形成共价交联。
- 若无赖氨酸，TG酶也可催化水解反应（如脱酰胺作用）。
2. **功能特点**：
- **增强蛋白质网络**：使松散蛋白质形成致密结构，改善质地与保水性。
- **无需高温或高压**：在温和条件下（pH 5–8，温度5–50℃）即可作用。

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### **二、来源与生产**
1. **天然来源**：
- 动物（如猪、牛血液）、植物（如豆类）、微生物（如茂原链轮丝菌*Streptomyces mobaraensis*）。
2. **工业化生产**：
- 主要通过**微生物发酵**（如细菌或真菌）提取，成本低且适合大规模应用。

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### **三、在食品工业中的应用**
#### **1. 肉制品加工**
- **重组肉**：
将碎肉粘合为整块（如重组牛排、肉卷），降低成本并提高利用率。
- 应用场景：快餐汉堡肉、火锅肉片。
- **改善质地**：
增强肉类的弹性、切片性和保水性，减少烹饪损失。
- 例如：火腿、香肠中添加TG酶提升口感。

#### **2. 乳制品**
- **奶酪改良**：
增加奶酪的弹性和拉伸性（如马苏里拉奶酪）。
- **酸奶与乳酪**：
优化蛋白质网络，减少乳清析出，提升质地稳定性。

#### **3. 面制品**
- **增强面筋**：
交联小麦蛋白，改善面包体积、柔软度及抗老化性。
- **无麸质食品**：
利用TG酶交联其他植物蛋白（如大豆、豌豆蛋白），模拟麸质口感。

#### **4. 植物蛋白产品**
- **人造肉**：
交联植物蛋白（如大豆、小麦蛋白），改善纤维结构与咀嚼感。
- **素食奶酪**：
替代动物凝乳酶，提升植物基奶酪的质地。

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### **四、安全性及法规**
1. **安全性评估**：
- **GRAS认证**：美国FDA认定微生物来源的TG酶为安全物质（GRAS No. GRN 000063）。
- **欧盟**：批准为食品添加剂（E1101）。
2. **潜在争议**：
- **过敏风险**：可能引起对谷蛋白敏感人群的交叉反应（需标注）。
- **伦理问题**：早期动物来源的TG酶涉及屠宰副产物，现微生物发酵为主流。

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### **五、使用方法与注意事项**
1. **添加量**：
- 通常为原料重量的**0.1%–1%**，过量可能导致过度交联而变硬。
2. **反应条件**：
- **温度**：最佳活性范围**40–50℃**，高温（>70℃）失活。
- **pH值**：最适pH **6–7**（中性至弱酸性）。
3. **步骤示例（肉类重组）**：
- 碎肉表面均匀撒TG酶粉末 → 按压成型 → 冷藏（4℃）静置数小时 → 加热定型。

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### **六、与其他酶类的区别**
| **特性** | **转谷氨酰胺酶** | **蛋白酶** | **脂肪酶** |
|----------------|---------------------------------|------------------------------|---------------------------|
| **功能** | 交联蛋白质，增强结构 | 分解蛋白质为小肽/氨基酸 | 分解脂肪为脂肪酸和甘油 |
| **应用目标** | 改善质地、粘合、保水性 | 嫩化肉类、水解蛋白 | 脱脂、风味释放 |
| **反应类型** | 合成（形成新化学键） | 分解（切断肽键） | 分解（酯键水解） |

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### **七、常见问题**
**Q1：TG酶是否适合家庭使用？**
- 是！市售TG酶粉可直接用于家庭烹饪（如自制重组牛排），需注意用量与反应时间。

**Q2：使用TG酶后需要加热吗？**
- 交联反应在冷藏条件下即可进行，但最终需加热使酶失活并固定结构（如煎牛排）。

**Q3：TG酶会改变食物的营养吗？**
- 仅改变蛋白质结构，不影响营养价值（氨基酸组成不变）。

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### **总结**
转谷氨酰胺酶是食品工业中的“分子胶水”，通过交联蛋白质实现质地改良、成本优化和资源高效利用。其安全性和广泛适用性使其成为现代食品加工的重要工具，尤其在重组肉、乳制品和植物基产品中表现突出。使用时需遵循推荐条件，以确保最佳效果与安全性。


### **Transglutaminase (TG Enzyme) Detailed Explanation**

Transglutaminase (TG enzyme or TGase) is an enzyme that catalyzes intra- or intermolecular cross-linking of proteins by forming **ε-(γ-glutamyl)lysine isopeptide bonds**, thereby altering protein structures. It is widely used in food processing, medicine, and biomaterials.

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### **I. Mechanism of Action**
1. **Catalytic Reaction**:
- Links **glutamine residues** (donor) and **lysine residues** (acceptor) in proteins to form covalent cross-links.
- In the absence of lysine, TG enzyme can also catalyze hydrolysis (e.g., deamidation).
2. **Functional Features**:
- **Strengthens Protein Networks**: Creates dense structures from loose proteins, improving texture and water retention.
- **No High Temperature or Pressure Required**: Works under mild conditions (pH 5–8, temperature 5–50°C).

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### **II. Sources and Production**
1. **Natural Sources**:
- Animals (e.g., pig or bovine blood), plants (e.g., legumes), microorganisms (e.g., *Streptomyces mobaraensis*).
2. **Industrial Production**:
- Primarily via **microbial fermentation** (bacteria or fungi), offering cost efficiency and scalability.

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### **III. Applications in the Food Industry**
#### **1. Meat Processing**
- **Restructured Meat**:
Binds meat scraps into whole cuts (e.g., restructured steaks, rolls), reducing costs and improving yield.
- Use Cases: Fast-food patties, hotpot meat slices.
- **Texture Enhancement**:
Improves elasticity, sliceability, and moisture retention in meats (e.g., ham, sausages).

#### **2. Dairy Products**
- **Cheese Modification**:
Enhances elasticity and stretchability (e.g., mozzarella cheese).
- **Yogurt and Curd**:
Stabilizes protein networks, reducing whey separation.

#### **3. Bakery Products**
- **Gluten Strengthening**:
Cross-links wheat proteins to improve bread volume, softness, and anti-staling properties.
- **Gluten-Free Foods**:
Mimics gluten texture by cross-linking plant proteins (e.g., soy, pea protein).

#### **4. Plant-Based Protein Products**
- **Artificial Meat**:
Enhances fibrous texture in plant-based proteins (e.g., soy, wheat protein).
- **Vegan Cheese**:
Replaces animal-derived rennet, improving plant-based cheese texture.

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### **IV. Safety and Regulations**
1. **Safety Evaluation**:
- **GRAS Certification**: Recognized as safe by the U.S. FDA (GRAS No. GRN 000063) for microbial-derived TG enzyme.
- **EU Approval**: Approved as food additive E1101.
2. **Controversies**:
- **Allergy Risks**: Potential cross-reactivity in gluten-sensitive individuals (requires labeling).
- **Ethical Concerns**: Early animal-derived TG enzyme involved slaughter byproducts; microbial production now dominates.

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### **V. Usage Guidelines and Precautions**
1. **Dosage**:
- Typically **0.1%–1%** of raw material weight; excess may cause over-crosslinking and hardening.
2. **Reaction Conditions**:
- **Temperature**: Optimal activity at **40–50°C**; deactivates above 70°C.
- **pH**: Optimal range **6–7** (neutral to slightly acidic).
3. **Step-by-Step Example (Meat Restructuring)**:
- Sprinkle TG enzyme powder evenly on meat scraps → Press into shape → Refrigerate (4°C) for hours → Heat to set.

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### **VI. Comparison with Other Enzymes**
| **Feature** | **Transglutaminase** | **Protease** | **Lipase** |
|--------------------|-------------------------------|-------------------------------|------------------------------|
| **Function** | Cross-links proteins | Breaks proteins into peptides | Breaks fats into fatty acids |
| **Application** | Texture improvement, binding | Meat tenderization, hydrolysis | Defatting, flavor release |
| **Reaction Type** | Synthesis (new bonds) | Breakdown (peptide cleavage) | Breakdown (ester hydrolysis) |

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### **VII. Frequently Asked Questions**
**Q1: Is TG enzyme suitable for home use?**
- Yes! Commercial TG enzyme powder can be used in home cooking (e.g., homemade restructured steak), but dosage and reaction time must be controlled.

**Q2: Is heating required after using TG enzyme?**
- Cross-linking occurs under refrigeration, but final heating is needed to deactivate the enzyme and fix the structure (e.g., pan-frying steak).

**Q3: Does TG enzyme alter food nutrition?**
- Only modifies protein structure; nutritional value remains unchanged (amino acid composition preserved).

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### **Summary**
Transglutaminase acts as a "molecular glue" in food technology, enhancing texture, reducing costs, and optimizing resource efficiency through protein cross-linking. Its safety and versatility make it indispensable in modern food processing, particularly in restructured meats, dairy, and plant-based products. Adherence to usage guidelines ensures optimal results and safety.