Applications of Freeze-Dried Citrus Peel in Medicine and Health Products

Freeze-drying technology plays two core roles in the medical and health applications of citrus peel:

1. “Preservation Lock” for Active Ingredients: Maximizes retention of natural compounds in citrus peel.

2. “Booster” for High-End Formulations: Provides key technological support for converting these compounds into stable and efficient modern pharmaceutical products.

01 Main Application Methods

1. Retention of Active Ingredients

• Application: Fresh citrus peel is freeze-dried for making chenpi (dried citrus peel) and fruit powders as primary health products.

• Advantages: Compared to traditional sun-drying or hot-air drying, freeze-drying maximizes the retention of heat-sensitive compounds such as flavonoids and vitamin C.

• Representative Compounds/Products: Neoeriocitrin, naringin, hesperidin-1, synephrine-5, vitamin C.

2. Functional Component Research

• Application: Preparation of high-purity citrus peel extracts in laboratories for scientific efficacy evaluation.

• Advantages: Ensures sample stability and preserves activity, making antioxidant and antidiabetic evaluations more reliable.

• Representative Compounds/Products: Flavonoid extracts used for antioxidant (free radical scavenging) and antidiabetic (α-glucosidase inhibition) studies.

3. Drug Delivery Systems

• Application: Active compounds (e.g., naringin) are formulated into high-end carriers such as solid lipid nanoparticles and then freeze-dried into powders.

• Advantages: Improves solubility and stability, enables sustained release, and enhances bioavailability.

• Representative Compounds/Products: Freeze-dried naringin solid lipid nanoparticles for pulmonary delivery systems.

4. Stabilization of Nutritional Components

• Application: Whole fruit or peel is processed into powders, or citrus peel essential oils are microencapsulated and then freeze-dried.

• Advantages: Converts liquid or volatile components into stable solid powders, facilitating storage, transportation, and inclusion in health products.

• Representative Compounds/Products: Drinkable whole orange powder, microencapsulated citrus peel oil with enhanced stability.

02 Differences Between Freeze-Drying and Traditional Drying Methods

Drying methods significantly affect flavonoid content and antioxidant activity in citrus peel. Studies indicate:

1. Highest Extraction Yield

   • Freeze-drying significantly increases essential oil yield. For example, freeze-dried Thomson navel orange peel achieves a yield of 6.90%, higher than fresh samples and other drying methods.

   • Reason: Low-temperature processing preserves oil cell structures, reducing volatile losses.

2. Enhanced Bioavailability

   • Best Color: Freeze-dried oils have the purest color with the lowest browning index.

   • Natural Aroma Preservation: Retains a flavor closest to fresh fruit.

   • Comprehensive Chemical Preservation: Minimal destruction of heat-sensitive compounds, high retention of monoterpenes.

3. Strongest Bioactivity

   • Antioxidant Activity: Highest total phenolic content (60.10 GAE/100 g), strongest FRAP activity, lowest IC50 (5.00 mg/ml).

   • Antimicrobial Activity: Lowest MIC and MBC compared to other drying methods.

4. Protection of Active Ingredients by Low-Temperature Processing

   • Avoids high-temperature damage to heat-sensitive compounds (e.g., terpenes), maximizes retention of vitamin C, flavonoids, and reduces losses of volatile components.