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Postharvest studies of resistance to gas diffusion in McIntosh apples
Postharvest Biology and Technology, 2 (1993) 329-339
329
© 1993 Elsevier Science Publishers B.V. All rights reserved 0925-5214/93/$06.00 POSTEC 01029
Postharvest studies of resistance to gas diffusion in Mclntosh apples Y o u n M. Park t, G.D. Blanpied, Z. Jozwiak, and F.W. Liu 2 Department of Fruit and Vegetable Science, Cornell University, Ithaca, New York 14853, USA (Accepted 2 November 1992)
ABSTRACT Park, Youn M., Bianpied, G.D., Joswiak, Z. and Liu, F.W. Postharvest studies of resistance to gas diffusion in Mclntosh apples. Postharvest Biol. Technol., 2: 329-339. Low oxygen injury (LOI) in controlled atmosphere (CA) storage was positively correlated with fruit resistance to gas diffusion (R) at harvest in the Mclntosh cultivar of apples (Malus domestica Borkh). In contrast to early harvest, late harvest resulted in lower R at harvest and after storage. The longer the apples were held in CA storage, the lower was R. R was negatively correlated with whole fruit volume after storage, but not at harvest. R was negatively correlated with respiration rate at harvest, when respiration and R were high, but not after CA storage, when respiration rate and R were low. R increased and fruit volume decreased during storage at 80% relative humidity (RH), whereas the opposite occurred in a high RH ( > 95%) environment. In comparison with other strains of Mclntosh, Marshall Mclntosh had higher R and enhanced susceptibility to LOI. And, at the same concentrations of fruit internal Oz, Marshall Mclntosh accumulated ten-fold more ethyl alcohol than did Rogers Mclntosh, which indicated different thresholds for anaerobiosis in these two strains.
Key words: Mclntosh Apples; Gas diffusion
INTRODUCTION
Studies of developing Mclntosh apples showed R was high in very young fruitlets, reached a minimum one month after full bloom, gradually increased to a new high immediately before fruit maturity, and then declined rapidly thereafter (Park, 1992). Recently it has been shown that tree applications of ethephon Correspondence to: G.D. Blanpied, Dept. of Fruit and Vegetable Sci., Cornell University, Ithaca, New York 14853, USA. 1 Current address: CA Dept., JINDO Corp., 371-62, Garibong-Dong, Seoul, Korea 2 Current address: Department of Horticulture, National Taiwan University, Taipei, Taiwan, R.O.C.
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Y.M. PARK ET AL.
simultaneously hastened fruit ripening and hastened the decline in R in attached apples and that R in Mclntosh apples was also influenced by location of the fruit in the tree canopy and by the mineral nutrition of the tree (Park, 1990). Wilkinson (1965) reported that apples stored at high RH increased in fruit volume and had low R, whereas comparable fruit stored at low RH decreased in fruit volume and had high R. Lidster (1990) observed that in comparison with Mclntosh stored in controlled atmosphere (CA) storage at high RH, comparable apples stored at low RH had greater R and were more likely to develop symptoms of LOI. Orchard, handling, and storage factors that influence LOI to apples have been described (Lidster et al. 1985a; Lidster et al. 1990). A program to minimize the likelihood of LOI in commercial CA storage has been outlined (Blanpied, 1990). However, the apple low oxygen CA applied research and development program at Cornell University has clearly shown there are among-orchard differences in low oxygen injury to apples that cannot be explained by current knowledge. In the present study we examine R in Mclntosh apples and its possible rolle in LOI. MATERIALS AND METHODS
Sources of apples Apples in the 1986-1989 studies of R were harvested from Mclntosh trees in the Cornell Orchard, Ithaca, New York. In the 1989-1990 preliminary observations of the Marshall strain of Mclntosh, apples were obtained from two commercial CA rooms located in New York's Hudson Valley. CA room #1 was opened on December 15 and the fruits were tested on February 3. CA #2 apples were tested on February 21, eight days after the room was opened. For the 1990-1991 experiments Rogers Mclntosh were picked from three trees in the Cornell Orchard on September 11 and Marshall Mclntosh were picked on September 10 from trees in three western New York orchards.
Fruit analyses Although 0 2 gradients are present within the flesh of bulky fruits and vegetables (Rajapakse et al., 1990; Solomos, 1987; Weichmann and Bruckner, 1989), gas exchange between apples and the surrounding atmosphere can be approximated by Fick's first law of diffusion (Burg and Burg, 1965; Cameron and Yang, 1982; Solomos, 1987). Burg and Burg (1965) reported that CO 2 and ethylene gas exchange in apples was quantitatively accounted for by gas diffusion through lenticles in the skin. We assumed in our studies that the same was true for 02. Microsensor measurements of 0 2 partial pressures in the flesh of bulky fruits and vegetables (Weichmann and Bruckner, 1989) coupled with precise measurements of 02 uptake may be used in future studies to estimate R more accurately. R was measured by the Cameron and Yang efflux method (1982), using ethane gas as the medium. Freshly harvested or stored fruits were kept in the laboratory at room temperature (20°) until all the surface moisture had evaported. These fruits were then loaded with 500 ppm ethane in air by placing the fruits in a glass
GAS D I F F U S I O N R E S I S T A N C E IN MC1NTOSH APPLES
331
jar through which the ethane gas mixture flowed continuously for one day, the time required for the fruit internal atmosphere to equilibrate with the ethane gas mixture. Individual fruits were then transfered to ethane-free, air-tight desiccators. One-ml gas samples were withdrawn from the system at five minute intervals for 30 rain to determine the time course of ethane flux out of the fruit. The air inside the system was continuously circulated by a diaphram pump during these measurements. The final concentration of ethane inside the system was measured one day later when equilibrium was reached between the internal fruit and system atmospheres. Fruit internal volume which was accessible by ethane gas was determined by calculating the amount of 500 ppm ethane needed to create the final concentration of ethane in the system. I~garithmic conversion of ethane evolution rates into the first-order constant and integration of Fick's law from time zero to a certain time t gave the formula: R = A / K Vin where, R is resistance, A is the area of individual fruit, K is the first order effiux rate constant, and Vin is the fruit internal volume accessible by ethane. The value of fruit R was expressed as resistance coefficient (RC = R). The units of RC was 104 s cm-1. In comparison with high values, low values for RC indicated low R. At the conclusion of the RC studies we developed and tested a field method for estimating R. Our tests showed a highly significant correlation, r = ( - ) 0 . 8 3 " * , between measurements of RC and measurements of skin porosity, which was determined by measuring the volume of air extracted from individual apples held under water (see Fig. 2 in Saltveit, 1982) for one minute with a slight vacuum (600 mm Hg). Higher vacuums a n d / o r longer extraction periods resulted in greater volumes of extracted air but poorer correlation between RC and skin porosity. Skin porosity was expressed as ml of air extracted per 100 ml of fruit volume. High values for skin porosity indicated low R. Ethylene climacteric dates, ie., the calendar dates when the average rates of ethylene emanation had increased to 1 /~1 kg -1 h -1, were estimated from daily measurements of ethylene emanation by ten apples held in individual fruit respirometers, which were continuously flushed with ethylene-free air. Rates of respiration were estimated from measurements of CO 2 (Fisher 1200 gas partitioner) that accumulated in air-tight systems used for RC measurements. Fruit volume was determined by displacement of water. Fruit internal O2 concentrations were determined by thermoconductivity analysis (Carle 400 AGC) of 0.5 ml gas samples obtained by syringe from the core cavities of apples that were removed from CA chambers and immediately submerged into water. Fruit ethyl alcohol which accumulated during anaerobiosis was measured by the Cornell Method described in Lidster et al (1985a). Individual apples were quartered and sealed into 473 ml (pint) canning jars, which had rubber serum caps installed in the metal lids. Equilibrium between head space and tissue ethyl alcohol was established in 2-3 hours. Head space ethyl alcohol in the canning jars was compared with head space ethyl alcohol in 500 ml Erlenmeyer flasks, which had known amounts of ethyl alcohol in 250 ml water. LOI was assessed visually as skin injury (Lidster, et al. 1990), organoleptically as tainted flavor, a n d / o r as excessive alcohol accumulation in the flesh of the apples.
332
Y.M. PARK ET AL.
Conditions of storage All experimental storage treatments were carried out at 2-3°C, except the controlled Marshall Mclntosh experiment, where 0°C and 3°C was used. Low RH in air storage was obtained by holding the apples in trays, which were stored in an almost empty room where the RH was 78-83%. In the high RH treatment, the apples were held in glass jars which were continuously flushed with water-saturated air. CA conditions were created by passing humidified, pre-mixed gas containing 2.0 percent 0 2 and 3.0 percent CO 2 (unless otherwise stipulated) through 19 L glass jars containing the apples. Gas mixtures were monitored with an Orsat gas analyzer and with a David Bishop Oxistat equipped with an ADC infrared CO 2 analyzer. RH was measured with a General Eastern dew-point meter. Statistical analyses Data were examined by standard deviation, t-test, regression analysis, and analysis of variance. Treatment mean separations were determined by Duncan's multiple range test. Significant differences at the 0.05 level are indicated by letters or a single *, and at the 0.01 level by ** RESULTS AND DISCUSSION
Factors correlated with RC RC was inversely correlated with whole fruit volume after storage, but not with whole fruit volume at harvest, nor with the ratio of fruit internal void volume/whole fruit volume at either time (Table 1). This observation suggested that either large apples developed less resistance a n d / o r small apples developed more resistance to gas exchange during storage. The latter probably happened because enhanced shrinkage in fruit volume has been associated with increases in RC (Table 5) (Wilkinson, 1965) and since small apples transpire relatively more rapidly than large apples (Smock and Neubert, 1950), it seems likely they shrink more in volume. The respiration rates of apples from three harvest dates were inversely correlated with RC at harvest when the rates of respiration were high, but not after CA storage when the rates of respiration were low (Table 2). This indicated that fruit
TABLE 1 C o r r e l a t i o n coefficients for t h e r e l a t i o n s h i p s b e t w e e n r e s i s t a n c e to gas e x c h a n g e ( R C ) a n d fruit c h a r a c t e r i s t i c s at h a r v e s t a n d a f t e r s t o r a g e Factor correlated with R C
At harvest 1987
1988
1987
1988
W h o l e fruit v o l u m e I n t e r n a l void v o l u m e / w h o l e fruit v o l u m e
- 0.43 ns
- 0.18 ns
- 0.53 *
- 0.50 *
- 0.32 ns
- 0.27 ns
- 0.40 ns
- 0.29 ns
• P < 0.05, ns = not statistically significant.
After storage
GAS DIFFUSION RESISTANCE IN MCINTOSH APPLES
333
TABLE 2
Respiration rate (Resp.), fruit resistance to gas exchange (RC), and the correlation (r) between these two variables at harvest and after 140 days in C A storage Harvest
At harvest
date
Resp 1
RC 2
r
After storage Resp. i
RC 2
r
Sept. 14 Sept. 21 Sept. 28
31 27 22
2.6 1.4 1.5
-0.47 * - 0.60 * * -0.42 *
15 16 14
1.7 1.0 1.0
- 0 . 0 1 ns - 0.15 ns - 0 . 4 5 ns
1 Mean mg CO 2 kg- 1 h- 1 2 M e a n 104 s c m I, low values indicate less resistance to gas exchange. 3 Correlation between values for RC and respiration rate. * P _< 0.05, * * P _< 0.01, ns = not statisti-
cally significant.
internal 0 2 depletion a n d / o r CO 2 accumulation caused by fruit respiration was great enough to attenuate respiration at harvest, but not after CA storage. Skin discoloration associated with LOI was significantly correlated with RC at harvest when apples were picked on two dates in 1986 and stored at 3°C in 2.0% 0 2 with 3.0% CO 2 (Table 3). No LOI developed during the first four months of storage when the same storage conditions were used in the 1988-1989 season. Thereafter, the atmosphere was changed to 1.0% 0 2 with 1.5% CO 2 to induce LOI. Again in that season, incidences of LOI were significantly correlated with the RC values determined at harvest. These significant correlations seemed to confirm the hypothesis that abnormal metabolism at the stress level of 0 2 content was related to the rate of gas diffusion (Boersig et al. 1988).
Postharvest factors affecting RC RC increased and then decreased rapidly during the period of fruit maturation (Table 4). The highest RC occurred immediately before or on the ethylene climacteric dates in 1986 and 1987. In 1988 the highest RC preceded the ethylene
TABLE 3
Correlation (r) between fruit resistance to gas exchange (RC) at harvest and the incidence of skin low o x y g e n i n j u r y in C A storage during two seasons t
Season
Skin low
Harvest Weeks after E C 2
Mean RC (104 s c m
1986-1987 1988-1989
1 2 1
1.3 1.2 1.9
1)
Correlation
o x y g e n injury
c o e f f i c i e n t (3)
( % o f fruit)
(r)
12.8 5.5 47.0
0.55 * 0.55 * 0.50 *
1 C A conditions which induced low o x y g e n i n j u r y w e r e 2 . 0 % 0 2 , 3 . 0 % C O 2 at 2 - 3 ° C in 1 9 8 6 - 1 9 8 7 and 1 . 0 % O 2 , 1 . 5 % C O 2 at 2 - 3 ° C in 1 9 8 8 - 1 9 8 9 . 2 Ethylene climacteric ( 1 / z l C 2 H 4 kg - 1 h 1) 3 Between mean RC at harvest and mean low o x y g e n i n j u r y (* P _< 0.05)
334
Y.M. PARK ET AL.
TABLE 4 Resistance to gas diffusion (RC) of Mclntosh apples on several sampling dates in three seasons 1986
1987
Date Aug. Sept. Sept. Sept. Sept. Sept. Sept. Sept. Sept.
30 4 9 14 17 19 21 24 29
RC (104 s c m -1)
Date
3.4 5.2 4.0 5.0 * 2.1 1.9 1.6 1.3 0.9
Sept. Sept. Sept. Sept. Sept. Sept.
1988
2 8 12 17 22 27
RC (104 s c m -1)
Date
3.8 3.3 3.7 * 2.0 1.2 1.1
Sept. Sept. Sept. Sept. Sept. Sept. Sept. Oct. Oct.
RC (104 s c m 6 12 16 21 24 25 28 2 4
l)
3.2 4.2 5.6 4.2 3.1 2.8 * 1.9 1.7 1.5
* Ethylene climacteric date (1/~1 C2H 4 kg -1 h - t )
climacteric date by about one week. Factors influencing RC changes in apples attached to the tree were discussed in two previous papers (Park, 1990 and 1992). When RH in storage was low (80%), there were significant decreases in fruit volume and significant increases in RC during several months of storage in two seasons (Table 5). When RH was maintained above 95%, there were significant increases in fruit volume and significant decreases in RC. Similar observations were made by Wilkinson (1965) and Lidster (1990). Increases in RC may have been associated with: (a) dehydration of the epidermal cells leading to the closure of lenticels (Clements, 1935); (b) shrinkage of fruit volume at low RH (Wilkinson, 1965); (c) water-logging of the tissue caused by cellular leakage (Sacher, 1959); (d) reduction of the intercellular void space and restriction of gaseous passage result-
TABLE 5 Changes in resistance to gas diffusion (RC) and changes in fruit volume during several months of storage in 2-3°C air at high and low relative humidity in two seasons Season
Harvest
Relative humidity during storage 80%
1987-88
1988-89
Aug. Sept. Sept. Sept. Aug. Sept. Sept. Oct.
28 6 16 26 28 6 17 1
> 95%
RC (104 s c m - l )
Fruit vol. (%)
RC (104 s cm l)
Fruit vol. (%)
+ 1.1 ns ns ns + 1.0 + 0.4 + 1.1 ns
- 0.9 ns ns -0.1 - 6.5 - 5.2 - 1.6 - 3.0
ns - 1.1 -0.5 -0.5 ns - 0.8 ns - 0.5
+ 3.0 + 2.1 +2.5 +3.0 ns ns + 1.5 + 2.0
ns - change was not statistically significant.
GAS DIFFUSION
RESISTANCE
IN MCINTOSH
335
APPLF.S
5.0'
A
~
~E~ 4.0" m
~. o
3.0'
RVEST
2.0 ~ 1.0'
AFTER S T O R A G E ~ . . . ~ , ~
0.0
A
5.o
'E
4.0
't,--
O
i
b
I
~
T
I
I
~ Q S ~
3.0
HARVEST
'W 2.0
orr
AFTER STORAGE
1.0 0.0
i
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!
i
29•8
9/9 19/9 29/9 9/10 HARVEST DATE Fig. 1. Fruit resistance coefficients (RC) of Mclntosh apples harvested on several dates in 1986 and then stored in air at 2-3°C with > 95% RH (above) and in CA at 2-3 ° with 2.0% 02, 3.0% COz and 90-95% RH (below). "At harvest" samples for air and for CA storage were analyzed separately. Significant changes from "at harvest" to "after storage" indicated by *.
ing from high cell turgor (Fockens and Meffert, 1972); (e) formation of a water harrier during fruit ripening (Ben-Yehoshua, Roberts and Biale, 1963); or (f) continuous deposit of cuticular wax (Smith, 1954; Metlitskii and Sal'kova, 1969). Mechanisms that may have decreased RC include: (a) reduction in cell turgor (Fockens and Meffert, 1972); (b) fruit expansion (Wilkinson, 1965); (c) continuous development of open lenticel structure (Clements, 1935); and (d) widening of skin pores as observed in bananas (Banks, 1984). Apples were harvested on several dates in 1986 for comparisons of RC at harvest and after air storage and CA storage at 2-3°C. There was a general trend for RC to decrease after harvest, with greater changes when RC was high at harvest and with a greater number of significant reductions in air storage than in CA storage (Fig, 1). The greater number of significant RC reductions in air storage could have been related to differences in R H in the two storage environments: 90-95% in CA and > 95% in air storage. RC was also influenced by the length of the storage period. Significant decreases in RC during storage occurred after each of the four harvest dates from 9-28 September shown in Fig. 2. The higher the RC at harvest, the greater were
336
Y.M. PARK ET AL.
4.0 ~"
3.0
,?.
2.0
~ 0
1.0
a
c
a
~
bc
~
-
~
SEPT.
~
SEPT. 14
~
SEPT.
19
SEPT. 28
n0.0
9
i
|
i
15
40
65
i
i
i
90 115 140
DAYS AFTER HARVEST Fig. 2. Changes in fruit resistance to gas diffusion (RC) of apples held in CA storage, 1987-1988. Same letters along a line indicate an insignificant change (P > 0.5). Harvest dates indicated at right of lines.
the r e d u c t i o n s d u r i n g storage a n d the higher were the e v e n t u a l p l a t e a u values for RC. Some possible e x p l a n a t i o n s for the c o n t i n u o u s decline of R C in storage are o u t l i n e d in the discussion of R H effects. T h e c o n t i n u o u s decline in R C d u r i n g C A storage raises the q u e s t i o n of why L O I usually develops later, r a t h e r t h a n earlier in the storage p e r i o d (Lidster et al., 1985b)? A r e s p o n s e to this query is offered at the e n d of this paper.
Studies of the Marshall strain of Mclntosh P r e l i m i n a r y analyses of apples from two c o m m e r c i a l C A r o o m s in the 1989-1990 storage season i n d i c a t e d that in c o m p a r i s o n with the n o r m a l a m o u n t of ethyl alcohol f o u n d in C A M c l n t o s h ( 2 - 1 0 m g / 1 0 0 g), M a r s h a l l M c l n t o s h apples had
TABLE 6 Skin porosity and ethyl alcohol content of various strains of Mclntosh sampled from two commercial CA rooms CA store
Lot
Mclntosh strain
Skin porosity (ml air/100 ml fruit vol.)
Ethyl alcohol (mg/100g)
1 2 3 4 5 6 7 8 9
Marshall Marshall Marshall Marshall Rogers Macspur Macspur Devarspur Morspur
0.41a 0.36a 0.73c 1.06d 0.80c 0.51b 1.04d
24 * 44 * 54b * 72b * * 4a 5a 4a 5a 4a
Numbers within a column followed by the same letter are not significantly different (P < 0.05). * tainted flavor * * tainted flavor and visible low oxygen injury
337
GAS DIFFUSION RESISTANCE IN MCINTOSH APPLES
TABLE 7 Fruit internal 0 2 concentration and ethyl alcohol content of Rogers Mclntosh (Rog) and Marshall Mclntosh (MM) apples removed from C A storage in 3 percent C O 2 with four concentrations of 0 2 at 0°C and 3°C, March 1991 02
treatment (%) 1 2 3 4
Fruit internal % 0 2 1 O°C
Ethyl alcohol content 2 3°C
Rog ( % 0 2)
MM
1.4 2.2 3.3
0.6 1.3 2.8
Rog ( % 0 2)
MM
0.7 1.6 2.4 3.1
0.5 0.9 1.9 2.3
O°C
3°C
Rog MM ( m g / 1 0 0 g)
Rog MM (rag/100 g)
33c 6a -
9a 5a -
10a 8a 5a 6a
342d 17b 7a 7a
1 All n u m b e r s within horizontal pairs of n u m b e r s were significantly different ( P < 0.05). 2 N u m b e r s followed by the same letter are not significantly different ( P < 0.05).
abnormally high concentrations of ethyl alcohol (Table 6). Skin porosity measurements R in those apples showed that in comparison with other tested strains, Marshall Mclntosh had significantly greater R (lower skin porosity). This observation suggested that the abnormally high alcohol concentrations in Marshall Mclntosh apples might have been caused by abnormally low fruit internal 0 2 concentrations. This hypothesis was tested in a controlled experiment during the next storage season. Marshall Mclntosh and Rogers Mclntosh apples were held at 0°C and 3°C with 3% CO 2 and four concentrations of 0 2 (Table 7). At all concentrations of 0 2, fruit internal 0 2 was lower in Marshall than in Rogers Mclntosh. At 1.0 and 2.0 percent oxygen the mean ethyl alcohol content was significantly higher in Marshall Mclntosh. Since individual fruit analyses were made for internal 0 2 concentration and ethyl alcohol content, it was possible to compare the ethyl alcohol content of Rogers and Marshall Mclntosh with similar fruit internal 0 2 concentrations. This
TABLE 8 Ethyl alcohol content of Marshall and Rogers Mclntosh apples with similar fruit internal 0 2 concentrations. Apples were removed from C A chambers held at 3°C with three percent CO 2 and 0.8 percent 0 2 Fruit
Rogers Mclntosh
internal 02
Apples (no.)
Ethyl alcohol ( m g / l O 0 g)
Apples (no.)
Ethyl alcohol ( m g / l O 0 g)
0.10-0.19 0.20-0.29 0.30-0.39 0.40-0.49 0.50-0.59 0.60-0.69
0 0 9 6 5 7
14 10 8 6
8 11 7 2 0 1
527 362 142 110 12
(%)
Marshall Mclntosh
338
Y.M. PARK ET AL.
comparison could only be made using fruit from the 1.0% 0 2 treatment at 3°C, because this was the only treatment that yielded sufficient numbers of Marshall and Rogers Mclntosh apples with similar fruit internal 0 2 concentrations. The ethyl alcohol concentrations in Marshall McIntosh apples with fruit internal 0 2 concentrations of 0.30-0.49% were ten fold higher than the ethyl alcohol concentrations in comparable Rogers McIntosh apples (Table 8). The enhanced susceptibility of Marshall Mclntosh to LOI, which was reported earlier (Autio et al., 1989) and confirmed in the present study (Table 6), can probably be attributed, at least in part, to (a) lower fruit internal 0 2 concentrations (Table 7) associated with high R (low skin porosity in Table 6) and (b) higher 0 2 thresholds for the shift from aerobic to anaerobic respiration (Table 8). These studies showed that among-orchard differences in susceptibility of Mclntosh apples to L O I in CA storage may be associated with differences in R. These studies suggested that differences in susceptibility to L O I may also be associated with differences in the internal 0 2 threshold at which aerobic respiration changes to anaerobic respiration.
REFERENCES Autio, W.R., Bramlage, W.J. and Lord, W.J., (1989) Storage of Marshall McIntosh: some cautions for 1989. Fruit Notes 54: 6-8. Banks, N.H. (1984) Studies of banana fruit surface in relation to the effect of TAL Pro-long coating on gaseous exchange. Sci. Hort. 24: 279-286. Ben-Yehoshua, S., Roberts, R.N. and Biale, J.B., (1963) Respiration and internal atmosphere of avocado fruit. Plant Physiol., 38: 194-201. Blanpied, G.D. (1990). Controlled atmosphere storage of apples and pears, In: M. Calderon and R. Barkai-Golan, (Editors), Food Preservation by Modified Atmospheres, CRC Press, Boston, 265-299. Boersig, M.R., Kader, A.A. and Romani, R.J., (1988). Aerobic-anaerobic respiratory transition in pear fruit and cultured pear cells. J. Am. Soc. Hort. Sci., 113: 869-873. Burg, S.P. and Burg, E.A. (1965). Gas exchange in fruits. Physiol. Plant., 18: 870-884. Cameron, A.C. and Yang, S.F., (1982). A simple method for the determination of resistance to gas diffusion in plant organs. Plant. Physiol., 70: 21-23. Clements, H.F. (1935). Morphology and physiology of pome lenticels of Pyrus malus. Bot. Gaz., 97: 101-117. Fockens, F.H. and Meffert, H.F., (1972). Biological properties of horticultural products as related to loss of moisture during cool down. J. Sci. Food Agric., 23: 285-298. Lidster, P.D., Blanpied, G.D. and Lougheed, E.C., (1985a). Factors affecting the progressive development of low-oxygen injury in apples In: S. Blankenship (Editors), Controlled Atmospheres for Storage and Transport of Perishable Commodities, Proc. 4th Nat. Controlled Atmospheres Research Conf., North Carolina Hort. Rept. No. 126, North Carolian State Univ., Raleigh, 57-69. Lidster, P.D., McRae, K.B. and Johnson, E.M., (1985b). Retention of apple quality in low-oxygen storage followed by standard controlled atmosphere regimes. J. Am. Soc. Hort. Sci., 110: 755-759. Lidster, P.D. (1990) Storage humidity influences fruit quality and permeability to ethane in
GAS D I F F U S I O N RESISTANCE IN M C I N T O S H APPLES
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'Mclntosh' apples stored in diverse controlled atmospheres. J. Am. Soc. Hort. Sci., 115: 94-96. Lidster, P.D., Blanpied, G.D. and Prange, R.K., (1990) Controlled-atmosphere disorders of commercial fruits and vegetables. Agric. Canada Publ. 1847/E, 58 pages. Metlitskii, L.V. and Sal'kova, E.G., (1969). Biochemical aspects of fruit storage in a controlled atmosphere (A review). Prikladnaya Biokhimia, 5: 387-395. Park, Y.M. (1990) Gas exchange in apples: pathway for gas exchange, changes in resistance to gas diffusion during fruit development and storage, and factors affecting the changes. PhD thesis, Cornell Univ., Ithaca, NY, 116 pages. Anon. (1992) Seasonal changes in resistance to gas diffusion of Mclntosh apples in relation to development of lenticel structure. J. Korean Soc. Hortic. Soc., 32 (3): 329-334. Rajapakse, N.C., Banks, N.H., Hewett, E.W. and Cleland, D.J., (1990) Development of oxygen concentration gradients in flesh tissue of bulky plant organs. J. Am. Soc. Hort. Sci. 115: 793-797. Sacher, J.A. (1959). Studies of auxin-membrane permeability relations in fruit and leaf tissues. Plant Physiol., 34: 372-375. Saltveit, M.E., Jr. (1982). Procedures for extracting and analyzing internal gas samples from plant tissues by gas chromatography, HortScience, 17 (6): 878-881. Smith, W.H. (1954). The structure of the mature apple in relation to gaseous exchange. Proc. 8th Internat. Bot. Cong., Paris: 405-407. Smock, R.M. and Neubert, A.M., (1950). Apples and Apple Products, Interscience Publishers, Inc., New York, 103. Solomos, T. (1987). Principles of gas exchange in bulky plant tissues. HortScience, 22 (5): 766-771. Weichmann, J. and Bruckner, B., (1989). Measurement of oxygen partial pressure in stored plant organs by polarographic method. Acta Hort., 258: 169-183. Wilkinson, B.G. (1965). Some effects of storge under different conditions of humidity on the physical properties of apples. J. Hort. Sci., 40: 58-65.
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© 1993 Elsevier Science Publishers B.V. All rights reserved 0925-5214/93/$06.00 POSTEC 01029
Postharvest studies of resistance to gas diffusion in Mclntosh apples Y o u n M. Park t, G.D. Blanpied, Z. Jozwiak, and F.W. Liu 2 Department of Fruit and Vegetable Science, Cornell University, Ithaca, New York 14853, USA (Accepted 2 November 1992)
ABSTRACT Park, Youn M., Bianpied, G.D., Joswiak, Z. and Liu, F.W. Postharvest studies of resistance to gas diffusion in Mclntosh apples. Postharvest Biol. Technol., 2: 329-339. Low oxygen injury (LOI) in controlled atmosphere (CA) storage was positively correlated with fruit resistance to gas diffusion (R) at harvest in the Mclntosh cultivar of apples (Malus domestica Borkh). In contrast to early harvest, late harvest resulted in lower R at harvest and after storage. The longer the apples were held in CA storage, the lower was R. R was negatively correlated with whole fruit volume after storage, but not at harvest. R was negatively correlated with respiration rate at harvest, when respiration and R were high, but not after CA storage, when respiration rate and R were low. R increased and fruit volume decreased during storage at 80% relative humidity (RH), whereas the opposite occurred in a high RH ( > 95%) environment. In comparison with other strains of Mclntosh, Marshall Mclntosh had higher R and enhanced susceptibility to LOI. And, at the same concentrations of fruit internal Oz, Marshall Mclntosh accumulated ten-fold more ethyl alcohol than did Rogers Mclntosh, which indicated different thresholds for anaerobiosis in these two strains.
Key words: Mclntosh Apples; Gas diffusion
INTRODUCTION
Studies of developing Mclntosh apples showed R was high in very young fruitlets, reached a minimum one month after full bloom, gradually increased to a new high immediately before fruit maturity, and then declined rapidly thereafter (Park, 1992). Recently it has been shown that tree applications of ethephon Correspondence to: G.D. Blanpied, Dept. of Fruit and Vegetable Sci., Cornell University, Ithaca, New York 14853, USA. 1 Current address: CA Dept., JINDO Corp., 371-62, Garibong-Dong, Seoul, Korea 2 Current address: Department of Horticulture, National Taiwan University, Taipei, Taiwan, R.O.C.
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simultaneously hastened fruit ripening and hastened the decline in R in attached apples and that R in Mclntosh apples was also influenced by location of the fruit in the tree canopy and by the mineral nutrition of the tree (Park, 1990). Wilkinson (1965) reported that apples stored at high RH increased in fruit volume and had low R, whereas comparable fruit stored at low RH decreased in fruit volume and had high R. Lidster (1990) observed that in comparison with Mclntosh stored in controlled atmosphere (CA) storage at high RH, comparable apples stored at low RH had greater R and were more likely to develop symptoms of LOI. Orchard, handling, and storage factors that influence LOI to apples have been described (Lidster et al. 1985a; Lidster et al. 1990). A program to minimize the likelihood of LOI in commercial CA storage has been outlined (Blanpied, 1990). However, the apple low oxygen CA applied research and development program at Cornell University has clearly shown there are among-orchard differences in low oxygen injury to apples that cannot be explained by current knowledge. In the present study we examine R in Mclntosh apples and its possible rolle in LOI. MATERIALS AND METHODS
Sources of apples Apples in the 1986-1989 studies of R were harvested from Mclntosh trees in the Cornell Orchard, Ithaca, New York. In the 1989-1990 preliminary observations of the Marshall strain of Mclntosh, apples were obtained from two commercial CA rooms located in New York's Hudson Valley. CA room #1 was opened on December 15 and the fruits were tested on February 3. CA #2 apples were tested on February 21, eight days after the room was opened. For the 1990-1991 experiments Rogers Mclntosh were picked from three trees in the Cornell Orchard on September 11 and Marshall Mclntosh were picked on September 10 from trees in three western New York orchards.
Fruit analyses Although 0 2 gradients are present within the flesh of bulky fruits and vegetables (Rajapakse et al., 1990; Solomos, 1987; Weichmann and Bruckner, 1989), gas exchange between apples and the surrounding atmosphere can be approximated by Fick's first law of diffusion (Burg and Burg, 1965; Cameron and Yang, 1982; Solomos, 1987). Burg and Burg (1965) reported that CO 2 and ethylene gas exchange in apples was quantitatively accounted for by gas diffusion through lenticles in the skin. We assumed in our studies that the same was true for 02. Microsensor measurements of 0 2 partial pressures in the flesh of bulky fruits and vegetables (Weichmann and Bruckner, 1989) coupled with precise measurements of 02 uptake may be used in future studies to estimate R more accurately. R was measured by the Cameron and Yang efflux method (1982), using ethane gas as the medium. Freshly harvested or stored fruits were kept in the laboratory at room temperature (20°) until all the surface moisture had evaported. These fruits were then loaded with 500 ppm ethane in air by placing the fruits in a glass
GAS D I F F U S I O N R E S I S T A N C E IN MC1NTOSH APPLES
331
jar through which the ethane gas mixture flowed continuously for one day, the time required for the fruit internal atmosphere to equilibrate with the ethane gas mixture. Individual fruits were then transfered to ethane-free, air-tight desiccators. One-ml gas samples were withdrawn from the system at five minute intervals for 30 rain to determine the time course of ethane flux out of the fruit. The air inside the system was continuously circulated by a diaphram pump during these measurements. The final concentration of ethane inside the system was measured one day later when equilibrium was reached between the internal fruit and system atmospheres. Fruit internal volume which was accessible by ethane gas was determined by calculating the amount of 500 ppm ethane needed to create the final concentration of ethane in the system. I~garithmic conversion of ethane evolution rates into the first-order constant and integration of Fick's law from time zero to a certain time t gave the formula: R = A / K Vin where, R is resistance, A is the area of individual fruit, K is the first order effiux rate constant, and Vin is the fruit internal volume accessible by ethane. The value of fruit R was expressed as resistance coefficient (RC = R). The units of RC was 104 s cm-1. In comparison with high values, low values for RC indicated low R. At the conclusion of the RC studies we developed and tested a field method for estimating R. Our tests showed a highly significant correlation, r = ( - ) 0 . 8 3 " * , between measurements of RC and measurements of skin porosity, which was determined by measuring the volume of air extracted from individual apples held under water (see Fig. 2 in Saltveit, 1982) for one minute with a slight vacuum (600 mm Hg). Higher vacuums a n d / o r longer extraction periods resulted in greater volumes of extracted air but poorer correlation between RC and skin porosity. Skin porosity was expressed as ml of air extracted per 100 ml of fruit volume. High values for skin porosity indicated low R. Ethylene climacteric dates, ie., the calendar dates when the average rates of ethylene emanation had increased to 1 /~1 kg -1 h -1, were estimated from daily measurements of ethylene emanation by ten apples held in individual fruit respirometers, which were continuously flushed with ethylene-free air. Rates of respiration were estimated from measurements of CO 2 (Fisher 1200 gas partitioner) that accumulated in air-tight systems used for RC measurements. Fruit volume was determined by displacement of water. Fruit internal O2 concentrations were determined by thermoconductivity analysis (Carle 400 AGC) of 0.5 ml gas samples obtained by syringe from the core cavities of apples that were removed from CA chambers and immediately submerged into water. Fruit ethyl alcohol which accumulated during anaerobiosis was measured by the Cornell Method described in Lidster et al (1985a). Individual apples were quartered and sealed into 473 ml (pint) canning jars, which had rubber serum caps installed in the metal lids. Equilibrium between head space and tissue ethyl alcohol was established in 2-3 hours. Head space ethyl alcohol in the canning jars was compared with head space ethyl alcohol in 500 ml Erlenmeyer flasks, which had known amounts of ethyl alcohol in 250 ml water. LOI was assessed visually as skin injury (Lidster, et al. 1990), organoleptically as tainted flavor, a n d / o r as excessive alcohol accumulation in the flesh of the apples.
332
Y.M. PARK ET AL.
Conditions of storage All experimental storage treatments were carried out at 2-3°C, except the controlled Marshall Mclntosh experiment, where 0°C and 3°C was used. Low RH in air storage was obtained by holding the apples in trays, which were stored in an almost empty room where the RH was 78-83%. In the high RH treatment, the apples were held in glass jars which were continuously flushed with water-saturated air. CA conditions were created by passing humidified, pre-mixed gas containing 2.0 percent 0 2 and 3.0 percent CO 2 (unless otherwise stipulated) through 19 L glass jars containing the apples. Gas mixtures were monitored with an Orsat gas analyzer and with a David Bishop Oxistat equipped with an ADC infrared CO 2 analyzer. RH was measured with a General Eastern dew-point meter. Statistical analyses Data were examined by standard deviation, t-test, regression analysis, and analysis of variance. Treatment mean separations were determined by Duncan's multiple range test. Significant differences at the 0.05 level are indicated by letters or a single *, and at the 0.01 level by ** RESULTS AND DISCUSSION
Factors correlated with RC RC was inversely correlated with whole fruit volume after storage, but not with whole fruit volume at harvest, nor with the ratio of fruit internal void volume/whole fruit volume at either time (Table 1). This observation suggested that either large apples developed less resistance a n d / o r small apples developed more resistance to gas exchange during storage. The latter probably happened because enhanced shrinkage in fruit volume has been associated with increases in RC (Table 5) (Wilkinson, 1965) and since small apples transpire relatively more rapidly than large apples (Smock and Neubert, 1950), it seems likely they shrink more in volume. The respiration rates of apples from three harvest dates were inversely correlated with RC at harvest when the rates of respiration were high, but not after CA storage when the rates of respiration were low (Table 2). This indicated that fruit
TABLE 1 C o r r e l a t i o n coefficients for t h e r e l a t i o n s h i p s b e t w e e n r e s i s t a n c e to gas e x c h a n g e ( R C ) a n d fruit c h a r a c t e r i s t i c s at h a r v e s t a n d a f t e r s t o r a g e Factor correlated with R C
At harvest 1987
1988
1987
1988
W h o l e fruit v o l u m e I n t e r n a l void v o l u m e / w h o l e fruit v o l u m e
- 0.43 ns
- 0.18 ns
- 0.53 *
- 0.50 *
- 0.32 ns
- 0.27 ns
- 0.40 ns
- 0.29 ns
• P < 0.05, ns = not statistically significant.
After storage
GAS DIFFUSION RESISTANCE IN MCINTOSH APPLES
333
TABLE 2
Respiration rate (Resp.), fruit resistance to gas exchange (RC), and the correlation (r) between these two variables at harvest and after 140 days in C A storage Harvest
At harvest
date
Resp 1
RC 2
r
After storage Resp. i
RC 2
r
Sept. 14 Sept. 21 Sept. 28
31 27 22
2.6 1.4 1.5
-0.47 * - 0.60 * * -0.42 *
15 16 14
1.7 1.0 1.0
- 0 . 0 1 ns - 0.15 ns - 0 . 4 5 ns
1 Mean mg CO 2 kg- 1 h- 1 2 M e a n 104 s c m I, low values indicate less resistance to gas exchange. 3 Correlation between values for RC and respiration rate. * P _< 0.05, * * P _< 0.01, ns = not statisti-
cally significant.
internal 0 2 depletion a n d / o r CO 2 accumulation caused by fruit respiration was great enough to attenuate respiration at harvest, but not after CA storage. Skin discoloration associated with LOI was significantly correlated with RC at harvest when apples were picked on two dates in 1986 and stored at 3°C in 2.0% 0 2 with 3.0% CO 2 (Table 3). No LOI developed during the first four months of storage when the same storage conditions were used in the 1988-1989 season. Thereafter, the atmosphere was changed to 1.0% 0 2 with 1.5% CO 2 to induce LOI. Again in that season, incidences of LOI were significantly correlated with the RC values determined at harvest. These significant correlations seemed to confirm the hypothesis that abnormal metabolism at the stress level of 0 2 content was related to the rate of gas diffusion (Boersig et al. 1988).
Postharvest factors affecting RC RC increased and then decreased rapidly during the period of fruit maturation (Table 4). The highest RC occurred immediately before or on the ethylene climacteric dates in 1986 and 1987. In 1988 the highest RC preceded the ethylene
TABLE 3
Correlation (r) between fruit resistance to gas exchange (RC) at harvest and the incidence of skin low o x y g e n i n j u r y in C A storage during two seasons t
Season
Skin low
Harvest Weeks after E C 2
Mean RC (104 s c m
1986-1987 1988-1989
1 2 1
1.3 1.2 1.9
1)
Correlation
o x y g e n injury
c o e f f i c i e n t (3)
( % o f fruit)
(r)
12.8 5.5 47.0
0.55 * 0.55 * 0.50 *
1 C A conditions which induced low o x y g e n i n j u r y w e r e 2 . 0 % 0 2 , 3 . 0 % C O 2 at 2 - 3 ° C in 1 9 8 6 - 1 9 8 7 and 1 . 0 % O 2 , 1 . 5 % C O 2 at 2 - 3 ° C in 1 9 8 8 - 1 9 8 9 . 2 Ethylene climacteric ( 1 / z l C 2 H 4 kg - 1 h 1) 3 Between mean RC at harvest and mean low o x y g e n i n j u r y (* P _< 0.05)
334
Y.M. PARK ET AL.
TABLE 4 Resistance to gas diffusion (RC) of Mclntosh apples on several sampling dates in three seasons 1986
1987
Date Aug. Sept. Sept. Sept. Sept. Sept. Sept. Sept. Sept.
30 4 9 14 17 19 21 24 29
RC (104 s c m -1)
Date
3.4 5.2 4.0 5.0 * 2.1 1.9 1.6 1.3 0.9
Sept. Sept. Sept. Sept. Sept. Sept.
1988
2 8 12 17 22 27
RC (104 s c m -1)
Date
3.8 3.3 3.7 * 2.0 1.2 1.1
Sept. Sept. Sept. Sept. Sept. Sept. Sept. Oct. Oct.
RC (104 s c m 6 12 16 21 24 25 28 2 4
l)
3.2 4.2 5.6 4.2 3.1 2.8 * 1.9 1.7 1.5
* Ethylene climacteric date (1/~1 C2H 4 kg -1 h - t )
climacteric date by about one week. Factors influencing RC changes in apples attached to the tree were discussed in two previous papers (Park, 1990 and 1992). When RH in storage was low (80%), there were significant decreases in fruit volume and significant increases in RC during several months of storage in two seasons (Table 5). When RH was maintained above 95%, there were significant increases in fruit volume and significant decreases in RC. Similar observations were made by Wilkinson (1965) and Lidster (1990). Increases in RC may have been associated with: (a) dehydration of the epidermal cells leading to the closure of lenticels (Clements, 1935); (b) shrinkage of fruit volume at low RH (Wilkinson, 1965); (c) water-logging of the tissue caused by cellular leakage (Sacher, 1959); (d) reduction of the intercellular void space and restriction of gaseous passage result-
TABLE 5 Changes in resistance to gas diffusion (RC) and changes in fruit volume during several months of storage in 2-3°C air at high and low relative humidity in two seasons Season
Harvest
Relative humidity during storage 80%
1987-88
1988-89
Aug. Sept. Sept. Sept. Aug. Sept. Sept. Oct.
28 6 16 26 28 6 17 1
> 95%
RC (104 s c m - l )
Fruit vol. (%)
RC (104 s cm l)
Fruit vol. (%)
+ 1.1 ns ns ns + 1.0 + 0.4 + 1.1 ns
- 0.9 ns ns -0.1 - 6.5 - 5.2 - 1.6 - 3.0
ns - 1.1 -0.5 -0.5 ns - 0.8 ns - 0.5
+ 3.0 + 2.1 +2.5 +3.0 ns ns + 1.5 + 2.0
ns - change was not statistically significant.
GAS DIFFUSION
RESISTANCE
IN MCINTOSH
335
APPLF.S
5.0'
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2.0 ~ 1.0'
AFTER S T O R A G E ~ . . . ~ , ~
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9/9 19/9 29/9 9/10 HARVEST DATE Fig. 1. Fruit resistance coefficients (RC) of Mclntosh apples harvested on several dates in 1986 and then stored in air at 2-3°C with > 95% RH (above) and in CA at 2-3 ° with 2.0% 02, 3.0% COz and 90-95% RH (below). "At harvest" samples for air and for CA storage were analyzed separately. Significant changes from "at harvest" to "after storage" indicated by *.
ing from high cell turgor (Fockens and Meffert, 1972); (e) formation of a water harrier during fruit ripening (Ben-Yehoshua, Roberts and Biale, 1963); or (f) continuous deposit of cuticular wax (Smith, 1954; Metlitskii and Sal'kova, 1969). Mechanisms that may have decreased RC include: (a) reduction in cell turgor (Fockens and Meffert, 1972); (b) fruit expansion (Wilkinson, 1965); (c) continuous development of open lenticel structure (Clements, 1935); and (d) widening of skin pores as observed in bananas (Banks, 1984). Apples were harvested on several dates in 1986 for comparisons of RC at harvest and after air storage and CA storage at 2-3°C. There was a general trend for RC to decrease after harvest, with greater changes when RC was high at harvest and with a greater number of significant reductions in air storage than in CA storage (Fig, 1). The greater number of significant RC reductions in air storage could have been related to differences in R H in the two storage environments: 90-95% in CA and > 95% in air storage. RC was also influenced by the length of the storage period. Significant decreases in RC during storage occurred after each of the four harvest dates from 9-28 September shown in Fig. 2. The higher the RC at harvest, the greater were
336
Y.M. PARK ET AL.
4.0 ~"
3.0
,?.
2.0
~ 0
1.0
a
c
a
~
bc
~
-
~
SEPT.
~
SEPT. 14
~
SEPT.
19
SEPT. 28
n0.0
9
i
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15
40
65
i
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90 115 140
DAYS AFTER HARVEST Fig. 2. Changes in fruit resistance to gas diffusion (RC) of apples held in CA storage, 1987-1988. Same letters along a line indicate an insignificant change (P > 0.5). Harvest dates indicated at right of lines.
the r e d u c t i o n s d u r i n g storage a n d the higher were the e v e n t u a l p l a t e a u values for RC. Some possible e x p l a n a t i o n s for the c o n t i n u o u s decline of R C in storage are o u t l i n e d in the discussion of R H effects. T h e c o n t i n u o u s decline in R C d u r i n g C A storage raises the q u e s t i o n of why L O I usually develops later, r a t h e r t h a n earlier in the storage p e r i o d (Lidster et al., 1985b)? A r e s p o n s e to this query is offered at the e n d of this paper.
Studies of the Marshall strain of Mclntosh P r e l i m i n a r y analyses of apples from two c o m m e r c i a l C A r o o m s in the 1989-1990 storage season i n d i c a t e d that in c o m p a r i s o n with the n o r m a l a m o u n t of ethyl alcohol f o u n d in C A M c l n t o s h ( 2 - 1 0 m g / 1 0 0 g), M a r s h a l l M c l n t o s h apples had
TABLE 6 Skin porosity and ethyl alcohol content of various strains of Mclntosh sampled from two commercial CA rooms CA store
Lot
Mclntosh strain
Skin porosity (ml air/100 ml fruit vol.)
Ethyl alcohol (mg/100g)
1 2 3 4 5 6 7 8 9
Marshall Marshall Marshall Marshall Rogers Macspur Macspur Devarspur Morspur
0.41a 0.36a 0.73c 1.06d 0.80c 0.51b 1.04d
24 * 44 * 54b * 72b * * 4a 5a 4a 5a 4a
Numbers within a column followed by the same letter are not significantly different (P < 0.05). * tainted flavor * * tainted flavor and visible low oxygen injury
337
GAS DIFFUSION RESISTANCE IN MCINTOSH APPLES
TABLE 7 Fruit internal 0 2 concentration and ethyl alcohol content of Rogers Mclntosh (Rog) and Marshall Mclntosh (MM) apples removed from C A storage in 3 percent C O 2 with four concentrations of 0 2 at 0°C and 3°C, March 1991 02
treatment (%) 1 2 3 4
Fruit internal % 0 2 1 O°C
Ethyl alcohol content 2 3°C
Rog ( % 0 2)
MM
1.4 2.2 3.3
0.6 1.3 2.8
Rog ( % 0 2)
MM
0.7 1.6 2.4 3.1
0.5 0.9 1.9 2.3
O°C
3°C
Rog MM ( m g / 1 0 0 g)
Rog MM (rag/100 g)
33c 6a -
9a 5a -
10a 8a 5a 6a
342d 17b 7a 7a
1 All n u m b e r s within horizontal pairs of n u m b e r s were significantly different ( P < 0.05). 2 N u m b e r s followed by the same letter are not significantly different ( P < 0.05).
abnormally high concentrations of ethyl alcohol (Table 6). Skin porosity measurements R in those apples showed that in comparison with other tested strains, Marshall Mclntosh had significantly greater R (lower skin porosity). This observation suggested that the abnormally high alcohol concentrations in Marshall Mclntosh apples might have been caused by abnormally low fruit internal 0 2 concentrations. This hypothesis was tested in a controlled experiment during the next storage season. Marshall Mclntosh and Rogers Mclntosh apples were held at 0°C and 3°C with 3% CO 2 and four concentrations of 0 2 (Table 7). At all concentrations of 0 2, fruit internal 0 2 was lower in Marshall than in Rogers Mclntosh. At 1.0 and 2.0 percent oxygen the mean ethyl alcohol content was significantly higher in Marshall Mclntosh. Since individual fruit analyses were made for internal 0 2 concentration and ethyl alcohol content, it was possible to compare the ethyl alcohol content of Rogers and Marshall Mclntosh with similar fruit internal 0 2 concentrations. This
TABLE 8 Ethyl alcohol content of Marshall and Rogers Mclntosh apples with similar fruit internal 0 2 concentrations. Apples were removed from C A chambers held at 3°C with three percent CO 2 and 0.8 percent 0 2 Fruit
Rogers Mclntosh
internal 02
Apples (no.)
Ethyl alcohol ( m g / l O 0 g)
Apples (no.)
Ethyl alcohol ( m g / l O 0 g)
0.10-0.19 0.20-0.29 0.30-0.39 0.40-0.49 0.50-0.59 0.60-0.69
0 0 9 6 5 7
14 10 8 6
8 11 7 2 0 1
527 362 142 110 12
(%)
Marshall Mclntosh
338
Y.M. PARK ET AL.
comparison could only be made using fruit from the 1.0% 0 2 treatment at 3°C, because this was the only treatment that yielded sufficient numbers of Marshall and Rogers Mclntosh apples with similar fruit internal 0 2 concentrations. The ethyl alcohol concentrations in Marshall McIntosh apples with fruit internal 0 2 concentrations of 0.30-0.49% were ten fold higher than the ethyl alcohol concentrations in comparable Rogers McIntosh apples (Table 8). The enhanced susceptibility of Marshall Mclntosh to LOI, which was reported earlier (Autio et al., 1989) and confirmed in the present study (Table 6), can probably be attributed, at least in part, to (a) lower fruit internal 0 2 concentrations (Table 7) associated with high R (low skin porosity in Table 6) and (b) higher 0 2 thresholds for the shift from aerobic to anaerobic respiration (Table 8). These studies showed that among-orchard differences in susceptibility of Mclntosh apples to L O I in CA storage may be associated with differences in R. These studies suggested that differences in susceptibility to L O I may also be associated with differences in the internal 0 2 threshold at which aerobic respiration changes to anaerobic respiration.
REFERENCES Autio, W.R., Bramlage, W.J. and Lord, W.J., (1989) Storage of Marshall McIntosh: some cautions for 1989. Fruit Notes 54: 6-8. Banks, N.H. (1984) Studies of banana fruit surface in relation to the effect of TAL Pro-long coating on gaseous exchange. Sci. Hort. 24: 279-286. Ben-Yehoshua, S., Roberts, R.N. and Biale, J.B., (1963) Respiration and internal atmosphere of avocado fruit. Plant Physiol., 38: 194-201. Blanpied, G.D. (1990). Controlled atmosphere storage of apples and pears, In: M. Calderon and R. Barkai-Golan, (Editors), Food Preservation by Modified Atmospheres, CRC Press, Boston, 265-299. Boersig, M.R., Kader, A.A. and Romani, R.J., (1988). Aerobic-anaerobic respiratory transition in pear fruit and cultured pear cells. J. Am. Soc. Hort. Sci., 113: 869-873. Burg, S.P. and Burg, E.A. (1965). Gas exchange in fruits. Physiol. Plant., 18: 870-884. Cameron, A.C. and Yang, S.F., (1982). A simple method for the determination of resistance to gas diffusion in plant organs. Plant. Physiol., 70: 21-23. Clements, H.F. (1935). Morphology and physiology of pome lenticels of Pyrus malus. Bot. Gaz., 97: 101-117. Fockens, F.H. and Meffert, H.F., (1972). Biological properties of horticultural products as related to loss of moisture during cool down. J. Sci. Food Agric., 23: 285-298. Lidster, P.D., Blanpied, G.D. and Lougheed, E.C., (1985a). Factors affecting the progressive development of low-oxygen injury in apples In: S. Blankenship (Editors), Controlled Atmospheres for Storage and Transport of Perishable Commodities, Proc. 4th Nat. Controlled Atmospheres Research Conf., North Carolina Hort. Rept. No. 126, North Carolian State Univ., Raleigh, 57-69. Lidster, P.D., McRae, K.B. and Johnson, E.M., (1985b). Retention of apple quality in low-oxygen storage followed by standard controlled atmosphere regimes. J. Am. Soc. Hort. Sci., 110: 755-759. Lidster, P.D. (1990) Storage humidity influences fruit quality and permeability to ethane in
GAS D I F F U S I O N RESISTANCE IN M C I N T O S H APPLES
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'Mclntosh' apples stored in diverse controlled atmospheres. J. Am. Soc. Hort. Sci., 115: 94-96. Lidster, P.D., Blanpied, G.D. and Prange, R.K., (1990) Controlled-atmosphere disorders of commercial fruits and vegetables. Agric. Canada Publ. 1847/E, 58 pages. Metlitskii, L.V. and Sal'kova, E.G., (1969). Biochemical aspects of fruit storage in a controlled atmosphere (A review). Prikladnaya Biokhimia, 5: 387-395. Park, Y.M. (1990) Gas exchange in apples: pathway for gas exchange, changes in resistance to gas diffusion during fruit development and storage, and factors affecting the changes. PhD thesis, Cornell Univ., Ithaca, NY, 116 pages. Anon. (1992) Seasonal changes in resistance to gas diffusion of Mclntosh apples in relation to development of lenticel structure. J. Korean Soc. Hortic. Soc., 32 (3): 329-334. Rajapakse, N.C., Banks, N.H., Hewett, E.W. and Cleland, D.J., (1990) Development of oxygen concentration gradients in flesh tissue of bulky plant organs. J. Am. Soc. Hort. Sci. 115: 793-797. Sacher, J.A. (1959). Studies of auxin-membrane permeability relations in fruit and leaf tissues. Plant Physiol., 34: 372-375. Saltveit, M.E., Jr. (1982). Procedures for extracting and analyzing internal gas samples from plant tissues by gas chromatography, HortScience, 17 (6): 878-881. Smith, W.H. (1954). The structure of the mature apple in relation to gaseous exchange. Proc. 8th Internat. Bot. Cong., Paris: 405-407. Smock, R.M. and Neubert, A.M., (1950). Apples and Apple Products, Interscience Publishers, Inc., New York, 103. Solomos, T. (1987). Principles of gas exchange in bulky plant tissues. HortScience, 22 (5): 766-771. Weichmann, J. and Bruckner, B., (1989). Measurement of oxygen partial pressure in stored plant organs by polarographic method. Acta Hort., 258: 169-183. Wilkinson, B.G. (1965). Some effects of storge under different conditions of humidity on the physical properties of apples. J. Hort. Sci., 40: 58-65.