Asian Pear

Maturity & Quality

Maturity Indices

• Change in skin color from green to yellowish green (Nijisseiki or 20th Century, Shinseiki, Tsu Li, Ya Li) or to golden brown (Hosui, Kosui, Niitaka, Shinko).
• Delayed harvest (which does not always mean higher soluble solids content) results in increased incidence and severity of physiological disorders and greater susceptibility to physical injury.

Quality Indices

• Freedom from mechanical injuries (’20th Century’ pears are very sensitive to impact and compression bruising; ‘Tsu Li’ and ‘Ya Li’ pears increase in susceptibility to bruising after storage; ‘Chojuro’ pears are firmer and more resistant to mechanical damage).
• Flesh firmness (penetration force using an 8-mm tip) of 7 to 10 lb-force depending on cultivar is optimum for eating; only small changes in firmness occur during storage at 0°C (32°F).
• Juiciness (not mealy) and sweetness (11 to 14% soluble solids depending on cultivar).
• Nutritive value: good source of dietary fiber

Temperature & Controlled Atmosphere (CA)

Optimum Temperature

0° ± 1°C (32 ± 2°F)

Freezing point: -1.5°C (29°F); may vary depending on soluble solids content.

Optimum Relative Humidity

90-95%

Rates of Respiration

To calculate heat production multiply ml CO₂/kg·h by 440 to get Btu/ton/ day or by 122 to get kcal/metric ton/day.

Rates of Ethylene Production

• Some cultivars (such as Nijisseiki, Kosui, and Niitaka) produce very little ethylene (<0.1 µl/kg·h).
• Other cultivars (such as Tsu Li, Ya Li, Chojuro, Shinsui, Kikusui, and Hosui) have a climateric respiratory pattern (rise in CO₂ production with ripening) and produce ethylene, up to 9 to 14 µl/kg·h (Tsu Li and Ya Li) or 1 to 3 µl/kg·h (other cultivars) at 0°C (32°F).

Responses to Ethylene 
Exposure of climacteric cultivars to >1 ppm ethylene accelerates loss of green color and slightly increases softening at 20°C (68°F). The effect of 0°C (32°F) are minimal.

Responses to Controlled Atmospheres (CA)

• Based on limited studies it appears that the magnitude of CA benefits for Asian pears is cultivar-specific and is generally less than that for European pears and apples.
• CA may extend storage durations of some Asian cultivars by about 25% relative to storage in air.
• Oxygen levels of 1-3% for some cultivars (such as Nijisseiki) or 3-5% for others (such as Ya Li) help retain firmness and delay changes in skin color.
• Asian pears are sensitive to CO₂ injury (above 2% CO₂ for most cultivars) when stored longer than a month.