Respiratory Changes of Several Varieties of Citrus Fruits During and After Conditioning with Two Different Humidities

Abstract

Respiratory changes of several varieties of citrus fruits including Ponkan cv. Ota (Citrus reticulata Blanco), Iyo cv. Miyauchi (C. iyo Hort. ex Tanaka), navel orange cv. Morita (C, sinensis Osbeck var. brasiliensis), Hassaku (C. hassaku Hort. ex Tanaka), Natsudaidai cv. Kawano (C. natsudaidai Hayata), Sanbokan (C. sulcata Hort. ex Tanaka), Murcott (C. reticulata Blanco×C, sinensis Osbeck), Seminole (C. grandis Macfadyen×C. tangerina Tanaka), Minneola (C. paradisi Macfadyen×C tangerine Tanaka), and sweet orange cv. Liu Cheng (C. sinensis Osbeck forma Liu Cheng) during conditioning (curing of rind) at 20°C with two differnt humidities (64 and 92% RH) for 7 days and subsequent storage at 5°C were investigated to elucidate the role of conditioning for long-term storage of citrus fruits.
1. The rate of weight loss of the fruits during conditioning and storage varied among different varieties. Among these varieties, Hassaku and Natsudaidai fruits showed less weight loss than other varieties during conditioning, while Ponkan, Iyo and Murcott tended to show much weight loss.
2. The respiratory rates of the fruits including Hassaku, Natsudaidai, Sanbokan, Seminole, navel orange, Iyo and Ponkan were inhibited significantly by conditioning at low humidity. However, this significant inhibition of respiration was not observed in varieties of Murcott, Minneola and Liu Cheng.
3. There was a significantly positive correlationship between changes in fruit weight and respiratory rate of the fruits in some varieties at the end of conditioning-period. Coefficient correlation (r) was found to be 0.902 for seminole, 0.819 for Natsudaidai, 0.748 for Iyo, 0.555 for Hassaku, 0.471 for navel orange, 0.430 for Ponkan, 0.420 for Sanbokan and 0.362 for Murcott, respectively. No significant correlation was found in varieties of Liu Cheng and Minneola.
4. The inhibition of respiratory rate of the fruits including Ponkan, navel orange, Hassaku, Natsudaidai, Sanbokan, Minneola and Liu Cheng from conditioning was found to continue for considerable period of storage at 5°C. This tendency in the respiration was not observed in varieties of Iyo, Murcott and Seminole.
From the above results, the role of conditioning for long-term storage of citrus fruits was discussed.