揭示温度处理对Pandanus amaryllifolius速溶粉叶片结构和代谢组特征的影响：一种多分析方法

《Food Chemistry: X》：Unveiling the influence of temperature treatments on the structural and Metabolomic profile of Pandan leaves ( Pandanus amaryllifolius) instant powder: a multi-analysis approach

不同温度处理对香草兰叶即食粉末的结构与风味影响研究，通过UV-Vis、FT-IR、XRD、SEM及电子鼻舌分析，发现高温（HT）处理显著增强溶解性及鲜味（P<0.05），形成多孔结构；室温（RT）处理保留最高挥发性成分（44.02%），维持传统芳香气味；低温（LT）介于两者之间。GC-MS和UPLC-MS/MS揭示HT促进美拉德反应生成风味物质，RT更好保存热敏性芳香成分。

　　
Pandan leaves, a tropical herb with broad applications in food and fragrance industries, have gained increasing attention for their unique aroma and health benefits. This study systematically investigated the effects of three temperature-based extraction methods—room temperature (RT), low temperature (LT), and high temperature (HT)—on the structural and flavor properties of instant pandan leaf powder. Through a combination of analytical techniques and sensory evaluations, the research identified optimal processing conditions for balancing functional components and sensory quality.

### 1. Research Background and Significance
Pandan leaves (Pandanus amaryllifolius) are native to Southeast Asia and have been cultivated in Hainan, China since the 1950s. Their cultivation has been promoted by regional initiatives like "Green Hainan" and "Tropical Specialty Efficient Agriculture," positioning pandan as a key product in Hainan's agricultural economy. The plant's distinctive aroma stems from compounds like 2-acetyl-1-pyrroline, while its nutritional profile includes phenolic compounds, flavonoids, and essential vitamins and minerals. These attributes make pandan leaves promising for functional foods, pharmaceuticals, and natural fragrances.

However, industrial utilization faces challenges:
- **Seasonal variability** and extreme weather disrupt cultivation
- **Post-harvest preservation** issues due to leaf browning and aroma loss
- **Processing limitations** in current methods

Instant pandan powder, with its high solubility and stability, addresses these challenges by enabling year-round use in beverages, snacks, and supplements. The critical question becomes: how does extraction temperature affect the product's nutritional value, aromatic profile, and processing stability?

### 2. Methodological Approach
The research adopted a multi-stage analytical framework:
- **Preparation**: Fresh leaves were processed through slicing, drying, and temperature-assisted extraction. Three groups (RT:25°C/5h, LT:4°C/60h, HT:85°C/45min) were prepared using water extraction followed by freeze-drying.
- **Structural Analysis**:
- **XRD** assessed crystallinity (HT:68.3%, RT:55.2%, LT:52.4%)
- **SEM** revealed HT produced porous structures (pores diameter 5-15μm) while RT maintained smoother particles (2000× magnification)
- **Chemical Profiling**:
- **GC-MS** detected 266 metabolites across groups, with HT showing 40% higher non-volatile compounds
- **UPLC-MS/MS** identified 88 differential metabolites, including amino acids and nucleotides
- **Sensory Evaluation**:
- **Electronic tongue** quantified taste profiles (HT: sweet 8.2/umami 7.1 vs RT: sweet 5.3/umami 4.2)
- **Electronic nose** distinguished volatile profiles (HT: W2W 3.2% vs RT: 4.1%)

### 3. Key Findings and Analysis
#### 3.1 Structural and Physicochemical Properties
The HT treatment created a porous microstructure (SEM images showed 30-50% surface area increase) that enhanced solubility by 18-22% compared to RT and LT. This structural difference directly impacted product performance:
- **HT**: High crystallinity (68.3%) facilitated rapid dissolution (450ms vs 720ms for RT)
- **RT**: Smooth particle surface (2000×) improved flowability (reduced caking by 35%)
- **LT**: Cold extraction preserved 15-20% more heat-sensitive polar compounds

#### 3.2 Volatile Aroma Components
GC-MS analysis revealed temperature-dependent shifts in volatile profiles:
- **RT group** retained 44.02% of original volatile compounds, including signature pandan aroma components like 2-acetyl-1-pyrroline (0.12% concentration)
- **HT group** developed new Maillard reaction products (pyrazines +35%, furans +28%)
- **LT group** showed 30% lower alcohol content (alcohols: 30.08% vs HT/RT: 44.02-44.06%)

ROAV analysis highlighted critical aroma contributors:
| Compound | ROAV | Odor Note | Concentration(HT) |
|----------------|------|------------------|-------------------|
| Acetic acid | 100 | Sour/Fruity | 0.78% |
| 2,3-Pentanedione| 8.72 | Caramel | 0.12% |
| Ethanol | 8.22 | Neutral alcohol | 0.25% |
| Nonanal | 2.45 | Fishy | 0.03% |

**RT优势**：保留了更高比例的原始挥发性芳香物质（44.02% vs HT的38.7%），特别是乙醇（8.22%）和2-甲基丁醛（ROAV 1.51）这类低阈值风味物质。

**HT优势**：通过美拉德反应生成复杂风味前体（如吡嗪类化合物浓度提升42%），同时蛋白质水解产生的谷氨酸（ROAV 3.2）显著增强鲜味。

#### 3.3 Non-volatile Metabolites
UPLC-MS/MS identified critical functional components:
- **HT group** showed 40% higher total amino acids (13.6g/100g protein content)
- **RT group** preserved 15% more polyphenols (determined via Folin-Ciocalteu assay)
- **LT group** accumulated 25% more organic acids (formamide +18%)

Notably, HT treatment induced significant changes in bioactive compounds:
- **Amino acids**: Glutamic acid (up 47%), aspartic acid (up 32%)
- **Phenolic compounds**: Catechins (down 18%), epigallocatechingallate (up 12%)
- **Vitamins**: Vitamin C retention improved by 27% in HT vs RT

#### 3.4 Sensory Evaluation
Electronic tongue measurements showed:
- **Sweetness**: HT (8.2) > RT (5.3) > LT (4.1)
- **Umami**: HT (7.1) > RT (4.2) > LT (3.8)
- **Bitterness**: RT (1.8) > HT (1.2) > LT (1.5)

Flavor balance was optimized in RT samples (bitterness/astringency ratio 1:0.8) while HT achieved better taste complexity (bitterness/astringency ratio 1:0.3).

### 4. Industrial Applications and Optimization
#### 4.1 Functional Food Development
HT-extracted powder shows superior nutritional profile:
- **Solubility**: 92% solubility (HT) vs 78% (RT)
- **Stability**: 40% longer shelf life due to lower moisture content (9.0% vs 9.9%)
- **Bioactive content**: 35% higher antioxidant capacity (DPPH assay)

But RT powder remains superior for:
- **Aromatic preservation**: Retained 88% of original pandan fragrance
- **Color retention**: Total color difference ΔE_ab <0.5 (HT) vs 1.2 (LT)

#### 4.2 Processing Optimization
Temperature selection depends on product goals:
- **Aroma-focused products** (e.g., pandan tea): RT extraction (25°C/5h) recommended
- **Functional supplements** (e.g., protein powder): HT extraction (85°C/45min) preferred
- **Flowable ingredients** (e.g., baking additives): LT extraction (4°C/60h) suitable

Critical processing parameters identified:
1. **Extraction time**: 60h cold extraction vs 45min hot extraction achieved similar yields (20%)
2. **Drying method**: Freeze-drying preserved 95% of volatile compounds vs spray drying
3. **Final moisture content**: <10% optimal for stability

### 5. Future Research Directions
1. **Metabolite interaction studies**: Investigate how pyrazines (HT+) and catechins (RT+) influence flavor perception
2. **Processing scale-up**: Evaluate heat transfer efficiency in industrial-scale hot water extraction
3. **Combination techniques**: Explore low-temperature pre-treatment followed by high-temperature extraction
4. **Health impact assessment**: Correlate amino acid profiles with specific health benefits

This research provides a critical reference for industrial applications, showing that:
- **HT processing** enhances umami and solubility but reduces aromatic complexity
- **RT processing** preserves volatile compounds but limits functional component extraction
- **LT processing** balances stability and aroma but sacrifices solubility

The optimal processing strategy depends on whether the priority is sensory quality (RT), functional value (HT), or production efficiency (LT). Future studies should integrate感官 science with metabolic fingerprinting to develop predictive models for product formulation.

通过温度梯度调控提取工艺，研究者成功实现了风味物质与功能成分的定向优化。高低温协同处理（如4°C预冷后85°C短时处理）可能成为新型解决方案，这种组合工艺理论上能同时保留挥发性芳香物质和促进热敏感营养素的释放，但需要进一步实验验证。

该研究不仅为 pandan leaf 加工提供了科学依据，更为其他芳香植物的工业化处理建立了方法论框架。通过精确控制温度参数，企业可在风味保留、功能成分提取和产品稳定性之间找到最佳平衡点，推动热带特色农产品向高附加值方向转型。