Agric. Biol. Chem ., 44 (8), 1917•`1922 , 1980 1917

Ethylene Production and Respiration of Postharvest Acid Citrus Fruits and Wase Satsuma Mandarin Fruit

Hirozo KUSUNOSE and Masayoshi SAWAMURA

Department of Agricultural Chemistry, Faculty of Agriculture, Kochi University,Nankoku, Kochi 783, Japan Received February 18, 1980

Ethylene production and respiratory rate were examined in acid citrus fruits such as yuzu, seedlessyuzu and daidai, and wase satsuma mandarin. A large amount of ethylene was produced from four varieties of citrus fruits harvested from May to July but not after September. A rise in ethylene production did not always coincide with a rise in respiratory rate. Excisedtissues of fruits contained the ability of ethylene production throughout the developmentalstages . The endogenous ethylene level at the ripening stage.reached the maximum when the color changed from green to yellow.

The acid citrus fruits, e.g. lemon, and their during the period from the young to ripening juices have been more successfully used for stage. culinary, beverage, industrial and medicinal purposes than any other citrus fruits, although they are not suitable for fresh eating. Yuzu, MATERIALS AND METHODS seedless yuzu, daidai and sudachi which have Materials. Fruits of the following 4 citrus varieties or

been used preferably in our country also species were used in the experiment: Citrus junos Tanaka

belong to the acid citrus fruit group. Ethylene (Yuzu), Citrus junos [Horticultural variety in Kochi: generally affects the fruit causing a series of Mukakuyu or seedless yuzu] (Seedless yuzu), Citrus biochemical changes and then leading to aurantium L. var. Daidai Makino (Daidai) and Citrus unshiu Marcov. var. Praecox Tanaka cv. Okitsu-wase senescence of fruit tissue. The acid citrus fruits (Wase satsuma mandarin). Fruits were obtained from the are often harvested at an immature stage, i.e. Kochi Fruit Tree Experimental Station. The experiment

before the attainment of horticultural ma was performed from May to November, 1979. turity, and then shipped to the market. Therefore, the occurrence of ethylene produc Ethylene and CO2 production from whole fruits. Fruits were carefully picked so as not to be wounded and placed tion in the postharvest fruit will affect the in desiccators in the dark at 24ßC according to Hyodo.3)

commercial quality of the fruit. In the young Gas samples of 2.5 ml were daily removed by plastic

fruits of orange,1,2)grapefruit,1,2) and satsuma syringes for determination of ethylene and CO2. mandarin3) a large amount of ethylene is produced, but lemon does not produce it in Ethylene production from excised tissues. Fruits harves any stage of development.2) From this fact it is ted from May till July 4 were cut longitudinally into six considered that there may be differences pieces of equal size. For fruits harvested from July 18 till November, 9 mm disks of peels including albedo and

among citrus varieties in the pattern of flavedo were used as excised tissues. The excised tissues ethylene production during fruit development. were immersed in 1% KCl solution with or without In the present study, the postharvest chan cycloheximide (3.6•~10-5„}) and subjected to vacuum infiltration according to Hyodo.3) Approximately 5g of

ges in ethylene production and respiratory the excised tissues were placed in 130-m1 Erlenmeyer flasks rate of acid citrus fruits, i.e. yuzu, seedless with silicon rubber caps and incubated in the dark at 24ßC. yuzu and daidai, were compared with those of Two and half milliliter-gas samples were periodically a non-acid fruit, wase satsuma mandarin, removed from the flasks for determination of ethylene. 1918 H. KUSUNOSE and M. SAWAMURA

The atmosphere in the flasks was flushed out with fresh air

after each determination. RESULTS Postharvest changes in ethylene production and Endogenous ethylene in fruits. Seedless yuzu and wase respiratory rate of whole fruits satsuma mandarin fruits harvested on October 9, i.e. just

before the color development, were stored in a room Fruits were first harvested on May 28,

(24ßC) for determination of the levels of endogenous approximately 2 weeks after anthesis, when ethylene. Samples of the internal gas phase were with every fruit weighed less than 1 g. Figure 1(a) drawn with plastic syringes from fruits submerged under shows that ethylene production to some degree water.4) occurred during storage not only of wase

Gas chromatography of ethyelene and CO2. A gas satsuma mandarin, but also of the acid citrus chromatograph equipped with a 1-ml gas cell was used. fruits; yuzu, seedless yuzu and daidai. The rise Ethylene was chromatographed on a 3 mm •~ 1 m activated in ethylene production preceded that in re alumina column at 70ßC and CO2 on a 3 mm•~3 m spiratory rate by 3 or 4 days for the acid citrus Porapak Q column at 70ßC according to a previous fruits, while both rises for satsuma mandarin paper.5) fruit occurred simultaneously on the 5th day after harvest. Browning of the fruit occurred

FIG. 1. Rates of Ethylene Production and Respiration in Yuzu, Seedless Yuzu, Daidai and Wase Satsuma

Mandarin Fruits Harvested at Different Stages.

•Z, yuzu; • , seedless yuzu;•¢, daidai; •œ, wase satsuma mandarin. Ethylene Production and Respiration of Postharvest Citrus Fruits 1919

near the peak of ethylene production in wase The relationship between the date when the satsuma mandarin, but it occurred before the yellowing of the postharvest fruit started and onset of the rise of ethylene production in the the rate of ethylene production at that time is

acid citrus fruits. In June 18-harvested fruits , shown in Fig. 2. The acid citrus fruits seem to however, large amounts of ethylene were be possibly differentiated from wase satsuma produced in the 4 varieties (Fig. 1(b)). The mandarin, in that there is a great difference maximum rates were in the range of 170•`210 between the former and the latter in the ,ƒÊl/kg/hr, and respiratory rates reached a ethylene level, enough to cause a physiological maximum almost simultaneously, showing a effect at each stage. Moreover, Fig. 2 shows similar pattern to typical climacteric fruits. In that the rate of ethylene production at the yuzu and daidai the rise of ethylene production color break decreases as the harvest date of the occurred one day earlier than that of CO2 fruit is delayed. production, and in seedless yuzu and satsuma mandarin the former coincided with the latter.

In yuzu fruit harvested on July 4, the peak of

ethylene production was not observed, though ethylene production of a small degree in

creased gradually during 17-day-storage (Fig.

1(c)). Seedless yuzu, daidai and wale satsuma

mandarin fruits still showed the clear rise and subsequent decline in ethylene production.

However, respiratory rates in the 4 varieties

showed no clear peak. As shown in Fig. 1(d),

yuzu fruit harvested on July 18 produced no ethylene, and daidai fruit produced it increas

ingly as the storage period was prolonged,

continuing to produce it even more after 16 - day-storage, so did wase satsuma mandarin

fruit. Seedless yuzu fruit had a small peak of

3.8ƒÊl/kg/hr 11 days after harvest and wale satsuma mandarin fruit had another peak of

4.9 ƒÊl/kg/hr 4 days after harvest. Respiratory

rates in the 4 varieties varied only within the FIG. 2. Changes in Rates of Ethylene Production at

range of 2 13 ml/kg/hr, without an apparent the Onset of Yellowing of Postharvest Fruits at Immature Stages. peak. Hence it seems to be difficult to find a Arrows indicate the picking date. relationship between ethylene production and

respiratory rate. Figure 1(e) shows the data of •Z, yuzu; • , seedless yuzu; •¢, daidai; •œ, wase satsuma mandarin. the fruits harvested on September 6. The fruits

harvested on September 25, October 30 and November 27 gave similar results. A detectable Ethylene production from excised tissues amount of ethylene was not produced in the 4 Figure 3 shows the time-course of ethylene varieties during 2-week-storage, and respi production from excised tissues of the fruits ratory rates also remained constant at a low harvested on June 18 either treated with level throughout the period. cycloheximide or not. Similar results were obtained in the case of other stages. When The relationship between ethylene production cycloheximide was applied to the excised and physiological change of the fruit at tissues to inhibit protein synthesis, ethylene immature stages production was blocked almost perfectly in the 1920 H. KUSUNOSE and M. SAWAMURA

4 varieties. The total amount of ethylene tissues of the 4 varieties have the ability of produced in the excised control tissues at every ethylene production throughout the develop stage is shown in Fig. 4. It is evident that the mental stage. The daidai tissues produced the largest amounts of ethylene, followed by wase satsuma mandarin, yuzu and seedless yuzu.

Endogenous ethylene levels at the period of the color development It was observed that ethylene concentration in the internal gas phase in the fruits increased around the breaking of the green color (Fig. 5). The endogenous ethylene levels reached the maximum 5 days after harvest when the green color of the fruit had turned yellow in the two varieties tested. The maximum levels were 3.9 ppm in seedless yuzu and 2.4 ppm in wase satsuma mandarin.

FIG. 3. Ethylene Production from Excised Tissues of

Fruits Harvested on June 18.

(a), control; (b), cycloheximide treatment.•Z

, yuzu; • , seedless yuzu; •¢, daidai; •œ, wase satsuma mandarin.

FIG. 5. Endogenous Ethylene Levels in Seedless Yuzu and Wase Satsuma Mandarin Fruits Harvested on October 9.

Arrows indicate the color development from green to yellow.•

, seedless yuzu; •œ, wase satsuma mandarin.

DISCUSSION

Fruits have generally been classified into two categories, the climacteric category which

includes tomato, banana and apple, and the

non-climacteric category which includes

grape, orange and pineapple,6) It has been, however, only discussed up to the present whether citrus fruit belong to the non FIG. 4. Total Amounts of Ethylene Produced from

Excised Tissues of Fruits Harvested at Each Stage.•Z climacteric6) or pseudoclimacteric type,2•`7) or the climacteric type.1) The steep rise in , yuzu; • , seedless yuzu; •¢, daidai; •œ, wase satsuma mandarin. ethylene production in the citrus fruits coin- Ethylene Production and Respiration of Postharvest Citrus Fruits 1921

cided with the rise of respiratory rate only at in Fig. 4, the values of ethylene production of the very young stages on May 28 and June 18 yuzu, seedless yuzu, daidai and wase satsuma

(Fig. 1(a) and (b)). But a correlation between mandarin were 91.3, 96.7, 25.0 and 42.6 ƒÊl/kg

ethylene production and respiration could not of tissue, respectively. Thus wounding of the

be found in the case of July 4 and July 18 due citrus fruits during the process of harvest,

to indistinct respiratory rise and after storage or transportation will affect signif

September due to no detectable ethylene icantly their commercial quality at any

production (Fig. 1(c)•`(e)). Murata and season. Miyashita7) reported that the behavior of From Fig. 5, it may be reasonable to say

ethylene and CO2 evolution from fruits was that the color break developed when the

not necessarily parallel in satsuma mandarin internal ethylene level had reached 3.9 ppm,

and natsudaidai fruits. Moreover, in the because this concentration surpassed the min

detached citrus fruits, considerable ethylene imum effective concentration of ethylene for

was produced from such young stages as when the citrus fruit that was less than 1 ppm.12,13)

the weight was less than 1 g (less than 10% of Luthra and Chima14) and Mizuno et al. 15)

maturity) (Fig. 1(a)), in contrast with typical observed that respiratory rate increased just at

climacteric fruit such as tomato which fail to the onset of the color change from green to

produce ethylene at the very young stage (less greenish yellow in malta orange and satsuma than 49% of maturity).8) Hence, these data mandarin fruit. Figure 5 also indicates that the

suggest that citrus fruits are not the climacteric behavior of endogenous ethylene level re

type, but the non-climacteric or pseudoclimac sembles the climacteric pattern although re

teric one as described previously .2,6,7) The role spiratory rate was not measured. Further

of ethylene at the young stage will be further investigation on endogenous gasses will be

investigated in detail. performed. The ethylene levels necessary for the color break, which results from the degradation of Acknowledgments. We wish to thank Mr. K. Yasuoka and Mr. T. Manabe, Kochi Fruit Tree Experimental chlorophyll,9) decreased with the age of the Station, Japan, for their generous supply of citrus fruits, and fruit at an immature stage (Fig. 2). It is likely Miss Y. Miyake, this Department, for her technical

that the older citrus fruits may become more assistance. sensitive to ethylene than the younger ones. In

regard to change of f sensitivity to ethylene,

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