Citrus Varieties Storage Requirements
Citrus fruit varieties exhibit significant differences in refrigeration requirements, chilling injury susceptibility, and storage duration capabilities. The HVAC system design for citrus processing and storage facilities must accommodate variety-specific temperature ranges, relative humidity parameters, and air velocity limitations to prevent physiological damage while maximizing shelf life.
Storage Parameter Overview
Citrus fruits are classified as non-climacteric, meaning they do not continue ripening after harvest. Temperature management directly affects respiration rate, moisture loss, and decay development. The fundamental storage relationship follows:
Respiration Rate Reduction: Q₁₀ = 2.0 to 3.0 for citrus fruits
For every 10°C reduction in storage temperature, respiration rate decreases by a factor of 2 to 3, extending storage life proportionally.
Orange Varieties
Orange varieties demonstrate wide variation in optimal storage temperatures and chilling injury sensitivity. Storage temperature selection depends on intended storage duration and variety physiology.
Valencia Oranges
Storage Parameters:
- Optimal Temperature: 3-6°C (37-43°F)
- Relative Humidity: 85-90%
- Maximum Storage Duration: 8-12 weeks
- Chilling Injury Threshold: Below 2°C (36°F) after 4 weeks
Valencia oranges tolerate slightly lower temperatures than most citrus varieties. The HVAC system must maintain precise temperature control within ±0.5°C to prevent temperature cycling that accelerates decay. Air velocity across fruit surfaces should remain below 0.25 m/s to minimize moisture loss while providing adequate circulation for CO₂ removal.
Physiological Considerations: Valencia oranges stored below 3°C develop pitting after 6-8 weeks. The rind becomes susceptible to Penicillium infection at relative humidity below 85%. High-velocity air distribution causes stem-end desiccation.
Navel Oranges
Storage Parameters:
- Optimal Temperature: 5-7°C (41-45°F)
- Relative Humidity: 85-90%
- Maximum Storage Duration: 6-8 weeks
- Chilling Injury Threshold: Below 4°C (39°F) after 3 weeks
Navel oranges are more sensitive to chilling injury than Valencia varieties. The characteristic navel aperture creates vulnerability to moisture loss, requiring tight humidity control. Storage below 5°C causes rind pitting and internal granulation after 4 weeks.
Blood Oranges
Storage Parameters:
- Optimal Temperature: 4-6°C (39-43°F)
- Relative Humidity: 90-95%
- Maximum Storage Duration: 4-6 weeks
- Chilling Injury Threshold: Below 3°C (37°F) after 2 weeks
Blood orange anthocyanin pigments degrade at temperatures above 7°C, resulting in color loss. Storage below 4°C maintains pigment stability but increases chilling injury risk. The HVAC system must provide higher relative humidity (90-95%) compared to other orange varieties due to thinner rind structure.
Grapefruit Varieties
Grapefruit varieties generally tolerate lower storage temperatures than oranges, with chilling injury thresholds varying by type and maturity.
White Grapefruit
Storage Parameters:
- Optimal Temperature: 10-15°C (50-59°F)
- Relative Humidity: 85-90%
- Maximum Storage Duration: 6-8 weeks
- Chilling Injury Threshold: Below 10°C (50°F) after 4 weeks
White grapefruit requires warmer storage than pigmented varieties. Storage below 10°C causes rind pitting, scald development, and increased decay susceptibility. The higher storage temperature necessitates increased ventilation rates to remove respiration heat and metabolic CO₂.
Pink and Ruby Red Grapefruit
Storage Parameters:
- Optimal Temperature: 10-13°C (50-55°F)
- Relative Humidity: 85-90%
- Maximum Storage Duration: 6-8 weeks
- Chilling Injury Threshold: Below 10°C (50°F) after 3 weeks
Pigmented grapefruit varieties maintain better color at slightly lower temperatures (10-13°C) compared to white varieties. Lycopene pigment stability improves at the lower end of the temperature range. Storage facilities must prevent temperature excursions above 15°C, which accelerate decay and reduce acidity.
Mandarin and Tangerine Varieties
Mandarin-type citrus exhibits high sensitivity to chilling injury and requires careful temperature management.
Clementine Mandarins
Storage Parameters:
- Optimal Temperature: 7-9°C (45-48°F)
- Relative Humidity: 90-95%
- Maximum Storage Duration: 4-6 weeks
- Chilling Injury Threshold: Below 6°C (43°F) after 2 weeks
Clementines possess thin rinds with high essential oil content, making them susceptible to moisture loss and chilling injury. Storage requires higher relative humidity (90-95%) and air velocities below 0.15 m/s. Temperature fluctuations exceeding ±1°C cause condensation on fruit surfaces, promoting decay.
Tangerines (Dancy, Honey)
Storage Parameters:
- Optimal Temperature: 4-7°C (39-45°F)
- Relative Humidity: 85-90%
- Maximum Storage Duration: 3-4 weeks
- Chilling Injury Threshold: Below 3°C (37°F) after 2 weeks
Traditional tangerine varieties demonstrate moderate chilling sensitivity. Storage duration remains limited (3-4 weeks) regardless of temperature due to rapid senescence. HVAC systems must provide rapid cooling to remove field heat within 12 hours of harvest.
Satsuma Mandarins
Storage Parameters:
- Optimal Temperature: 5-8°C (41-46°F)
- Relative Humidity: 90-95%
- Maximum Storage Duration: 2-4 weeks
- Chilling Injury Threshold: Below 4°C (39°F) after 1 week
Satsuma mandarins exhibit extreme sensitivity to both chilling injury and moisture loss. The loose rind structure requires precise humidity control with minimal air movement. Storage facilities must maintain dew point within 1°C of air temperature to prevent condensation while avoiding desiccation.
Lemon and Lime Varieties
Lemon and lime varieties require significantly different storage temperatures compared to sweet citrus types.
Lemons (Eureka, Lisbon)
Storage Parameters:
- Optimal Temperature: 10-13°C (50-55°F)
- Relative Humidity: 85-90%
- Maximum Storage Duration: 12-16 weeks
- Chilling Injury Threshold: Below 10°C (50°F) after 2 weeks
Lemons demonstrate excellent storage life at proper temperatures. Storage below 10°C causes pitting and membranous staining. The extended storage duration requires careful control of ethylene levels (below 0.1 ppm) to prevent premature senescence. Ventilation rates should provide 10-15 air changes per hour.
Persian Limes
Storage Parameters:
- Optimal Temperature: 9-11°C (48-52°F)
- Relative Humidity: 85-90%
- Maximum Storage Duration: 6-8 weeks
- Chilling Injury Threshold: Below 7°C (45°F) after 2 weeks
Persian limes are highly susceptible to chilling injury below 7°C, developing brown pitting within 1-2 weeks. Storage above 12°C accelerates yellowing and decay. The narrow optimal temperature range (9-11°C) requires precise HVAC control with temperature sensors calibrated to ±0.2°C accuracy.
Key Limes
Storage Parameters:
- Optimal Temperature: 10-12°C (50-54°F)
- Relative Humidity: 85-90%
- Maximum Storage Duration: 3-4 weeks
- Chilling Injury Threshold: Below 9°C (48°F) after 1 week
Key limes demonstrate even higher chilling sensitivity than Persian limes. The small fruit size results in rapid moisture loss, requiring relative humidity maintenance at 88-90%. Storage life remains inherently limited due to thin rind structure.
Specialty Citrus Varieties
Specialty citrus types present unique refrigeration challenges due to unusual morphology and physiology.
Kumquats
Storage Parameters:
- Optimal Temperature: 8-10°C (46-50°F)
- Relative Humidity: 90-95%
- Maximum Storage Duration: 3-4 weeks
- Chilling Injury Threshold: Below 7°C (45°F) after 2 weeks
Kumquats feature edible rinds with high essential oil content, requiring elevated humidity levels to prevent oil gland desiccation. The small fruit size (20-40 g) creates high surface area to volume ratio, accelerating moisture loss. Air velocities must remain below 0.10 m/s.
Pomelos
Storage Parameters:
- Optimal Temperature: 10-13°C (50-55°F)
- Relative Humidity: 85-90%
- Maximum Storage Duration: 8-12 weeks
- Chilling Injury Threshold: Below 9°C (48°F) after 3 weeks
Pomelos possess thick albedo layers that provide protection against moisture loss but increase chilling injury susceptibility. The large fruit size (500-2000 g) requires extended cooling times (24-36 hours) to reach core temperature. Storage facilities must accommodate reduced stacking density due to fruit weight.
Tangelos (Minneola, Orlando)
Storage Parameters:
- Optimal Temperature: 7-10°C (45-50°F)
- Relative Humidity: 85-90%
- Maximum Storage Duration: 4-6 weeks
- Chilling Injury Threshold: Below 5°C (41°F) after 2 weeks
Tangelo hybrids demonstrate intermediate storage characteristics between parent types. Minneola variety tolerates slightly lower temperatures (7-8°C) compared to Orlando (9-10°C). The characteristic neck formation creates vulnerability to stem-end moisture loss.
Variety-Specific Storage Requirements
| Variety | Temperature (°C) | RH (%) | Max Storage | Chilling Threshold | Air Velocity |
|---|---|---|---|---|---|
| Valencia Orange | 3-6 | 85-90 | 12 weeks | <2°C, 4 weeks | <0.25 m/s |
| Navel Orange | 5-7 | 85-90 | 8 weeks | <4°C, 3 weeks | <0.25 m/s |
| Blood Orange | 4-6 | 90-95 | 6 weeks | <3°C, 2 weeks | <0.20 m/s |
| White Grapefruit | 10-15 | 85-90 | 8 weeks | <10°C, 4 weeks | <0.30 m/s |
| Pink Grapefruit | 10-13 | 85-90 | 8 weeks | <10°C, 3 weeks | <0.30 m/s |
| Clementine | 7-9 | 90-95 | 6 weeks | <6°C, 2 weeks | <0.15 m/s |
| Tangerine | 4-7 | 85-90 | 4 weeks | <3°C, 2 weeks | <0.20 m/s |
| Satsuma | 5-8 | 90-95 | 4 weeks | <4°C, 1 week | <0.10 m/s |
| Lemon | 10-13 | 85-90 | 16 weeks | <10°C, 2 weeks | <0.25 m/s |
| Persian Lime | 9-11 | 85-90 | 8 weeks | <7°C, 2 weeks | <0.20 m/s |
| Key Lime | 10-12 | 85-90 | 4 weeks | <9°C, 1 week | <0.15 m/s |
| Kumquat | 8-10 | 90-95 | 4 weeks | <7°C, 2 weeks | <0.10 m/s |
| Pomelo | 10-13 | 85-90 | 12 weeks | <9°C, 3 weeks | <0.25 m/s |
| Tangelo | 7-10 | 85-90 | 6 weeks | <5°C, 2 weeks | <0.20 m/s |
Chilling Injury Susceptibility Rankings
Citrus varieties ranked from most to least susceptible to chilling injury:
High Susceptibility (Injury within 1-2 weeks):
- Key Lime
- Satsuma Mandarin
- White Grapefruit
Moderate Susceptibility (Injury within 2-4 weeks): 4. Clementine Mandarin 5. Persian Lime 6. Blood Orange 7. Tangerine 8. Kumquat 9. Tangelo 10. Pomelo
Low Susceptibility (Injury after 4+ weeks): 11. Navel Orange 12. Lemon 13. Pink Grapefruit 14. Valencia Orange
HVAC System Design Implications
Multi-variety citrus storage facilities require zone-based refrigeration systems with independent temperature control for each variety group:
Temperature Zones Required:
- Cool Zone: 3-7°C (Valencia, Navel, Blood oranges, Tangerines)
- Intermediate Zone: 7-10°C (Clementines, Kumquats, Tangelos, Persian Limes)
- Warm Zone: 10-15°C (White Grapefruit, Pink Grapefruit, Lemons, Key Limes, Pomelos)
Each zone requires dedicated refrigeration capacity, humidity control, and air distribution systems. Temperature monitoring must employ calibrated sensors at multiple locations within each storage room to detect thermal stratification and ensure uniform conditions throughout the fruit mass.
The evaporator coil design must maintain approach temperatures within 2-3°C of room setpoint to prevent excessive dehumidification. Direct expansion systems provide superior humidity control compared to flooded systems for citrus storage applications due to faster response to load changes and reduced coil frosting cycles.