Hypobaric storage removes scald-related volatiles during the
low temperature induction of superficial scald of apples
Zhenyong Wang, David R. Dilley *
Department of Horticulture,Michigan State Uni6ersity,East Lansing,MI48824,USA
Received 31 January 1999; accepted 23 November 1999
Abstract
‘Law Rome’ and ‘Granny Smith’ apples were stored hypobarically in air at 5 kPa total pressure and also in air or controlled atmosphere (CA) at 1.5 or 3% O2 with 0 or 3% CO2, for 8 months at 1°C. Fruit were placed under hypobaric storage immediately after harvest or after 0.5, 1, 2, 3, 4, 5 or 6 months storage in air at 1°C to determine the effects of delaying imposition of hypobaric storage on ripening and scald development and on the production of
a-farnesene and its oxidation product 6-methyl-5-hepten-2-one (MHO). If fruit were placed under hypobaric
conditions within 1 month after harvest, scald did not develop. After a 3-month delay, scald development was similar to that for fruit stored continuously in air. Both cvs. produced MHO which accumulated in their epicuticular wax when fruit were placed under hypobaric storage after a 1-month or more delay in air. MHO which had partitioned in the epicuticular wax of fruit stored hypobarically after 2 or more months delay was released upon transfer of fruit to atmospheric pressure of 20°C; MHO accumulated and/or was produced in direct proportion to the delay prior to hypobaric storage. In another experiment with five apple cvs., the production rates ofa-farnesene and MHO were low
during hypobaric storage, but upon removal of fruit from storage after 7 months, the rates increased over a 7 day period in air at 20°C and then sharply decreased afterward. After storage,a-farnesene and MHO production rates
were similar and high for ‘Law Rome’, ‘Mutsu’, ‘Red Delicious’ and ‘Golden Delicious’ apples and were the lowest for ‘Granny Smith’. Scald did not develop on any hypobarically stored fruit whereas it did on all cvs. except ‘Golden Delicious’ stored in air. It was proposed that hypobaric ventilation removes a scald-related volatile substance that otherwise accumulates and partitions into the epicuticular wax of fruit stored in air at atmospheric pressure. © 2000 Elsevier Science B.V. All rights reserved.
Keywords: Apple; Superficial scald; Hypobaric storage; Volatiles; a-Farnesene; 6-Methyl-5-hepten-2-one; antioxidants; Chilling
injury
www.elsevier.com/locate/postharvbio
1. Introduction
Hypobaric storage is a system of storing com-modities while ventilating with air at less than atmospheric pressure. The partial pressure of each component gas in air is reduced in direct
propor-* Corresponding author. Tel.: +1-517-3553286; fax: + 1-517-3530890.
E-mail addresses: [email protected] (Z. Wang), [email protected] (D.R. Dilley)
tion to the total pressure as a consequence of Dalton’s Law. Thus, at 10.1 kPa absolute total
pressure, the O2 partial pressure is equivalent to
2.1% (v/v) O2 at atmospheric pressure, and the
same is true for all other gases. The concept of hypobaric storage of fruit was introduced by Burg and Burg (1966). Since then it has been widely investigated (Dilley, 1972, 1982; Spalding and Reeder, 1976a,b) and reviewed (Jamieson, 1980). Hypobaric storage extends the useful life of perishable commodities well beyond that
achievable by CA storage at the equivalent O2
levels. Apples that are preclimacteric at harvest remain preclimacteric during hypobaric storage at 10.1 kPa (Dilley, 1972). Internal ethylene con-centration is decreased 10-fold which is well be-low the level required to induce ripening. When this is coupled to a reduction in the rate at
which ethylene is produced at the reduced O2
level equivalent to 2.1%, an even further reduc-tion in ethylene concentrareduc-tion may exist within
the tissue. Moreover, the concentration of CO2
produced in fruit metabolism is reduced, and one can assume that the concentration of metabolic products such as ethanol, acetaldehyde and other
compounds (e.g. a-farnesene) which have
signifi-cant vapor pressures at fruit storage tempertures would likewise be reduced under hypobaric
ven-tilation. a-Farnesene and its oxidation product(s)
have been implicated as factors in the superficial scald disorder (Anet, 1972; Song and Beaudry, 1996; Wang and Dilley, 1997; Mir et al., 1998; Mir and Beaudry, 1999). Apple fruit do not de-velop scald when stored hypobarically (Dilley, 1972), while fruit stored at the equivalent partial
pressure of O2 in CA storage can sometimes
de-velop scald. The combined effects of lower pro-duction rates of oxidatively produced metabolites
at reduced O2 levels and enhanced removal of
substances with significant vapor pressures under hypobaric storage conditions may at least par-tially explain prevention of scald. Hypobaric storage thus offers an experimental system to elucidate the nature of these substances. It was hypothesized that hypobaric storage controls scald by effectively decreasing the accumulation of scald-related volatile compounds in fruit that may affect fruit metabolism such as ethylene,
a-farnesene and its oxidation product MHO.
Hy-pobaric storage was investigated to determine ef-fective treatment regimens and to gain insight into the mechanism of scald control.
2. Materials and methods
2.1. Plant materials
‘Law Rome’, ‘Granny Smith’, ‘Red Delicious’, ‘Mutsu’ and ‘Golden Delicious’ apples were har-vested at the preclimacteric stage of maturity from the Michigan State University Clarkesville Experiment Station (CHES).
2.2. Hypobaric studies in 1995/96
Apples were placed in two 1270-l vacuum ves-sels in a 1°C storage room. The vesves-sels were maintained hypobarically at 5 kPa pressure of air with a ventilation rate of one vessel void volume change per hour at 97% RH (Dilley, 1982). After 2 months of hypobaric storage, fruit were
trans-ferred to CA at 1.5% O2 plus 3% CO2, or stored
in air at 1°C. After CA or air storage for 6 months, scald index was measured based on the percentage of fruit surface area affected, where
no scald=0, B25%=1, 25 – 50%=2, and \
50%=3. The scald index was normalized to 100
by multiplying the values by 100/3. Scald index
was measured again after an additional 10 months of storage in air.
2.3. Hypobaric studies 1996/97
Fruit were stored hypobarically, or in air or in
CA at 1.5 or 3% O2 with 0 or 3% CO2 for 8
months at 1°C. The hypobaric fruit were then placed in air for an additional 4 or 10 months. Some fruit stored in CA for 2 months were transferred to air. Scald index was measured as
before at various intervals of storage. a
Table 1
Effect of pretreatment with hypobaric storage (5 kPa of air) followed by controlled atmosphere (CA) (1.5% O2+3% CO2) or air storage on scald development in ‘Granny Smith’ and ‘Law Rome’ apples at 1°C in 1995
Scald indexa Storage durations
(months)
Air ‘Granny Smith’ ‘Law Rome’ Hypobaric CA was normalized to 100 by multiplying the values by 100/3. Means within columns followed by different letters differ at
P50.05.
scribed by Wang and Dilley (2000). After a 90-min enclosure, the headspace of a glass jar with about 1.2 kg of fruit was sampled by solid phase microextraction (SPME) equilibrating the fibre for 4 min to absorb volatiles. The volatiles were
measured by gas chromatography/mass
spec-trometry (GC/MS) as described by Song et al.
(1997) to determine volatile production/evolution. At the same time intervals, 14 mg of epicuticular wax sample was removed from five fruit in each treatment and placed in a 2-ml glass vial for 3 h at
20°C to determine the amount of a-farnesene and
MHO partitioned in the epicuticular wax by
SPME/GC/MS as described above. Fruit in
paral-lel samples were used for fruit firmness and ripen-ing changes immediately upon removal from storage and again after 7 days at 20°C (data not presented).
3. Results
3.1. Hypobaric studies in 1995–97
‘Granny Smith’ and ‘Law Rome’ apples stored hypobarically for 2 months then under CA at
1.5% O2 plus 3% CO2 for 6 months did not
develop scald during storage (Table 1). A slight amount of scald developed on the fruit when stored in air for a further 10 months. Fruit stored hypobarically and then in air for 6 or 16 months developed low scald indices (Table 1). Fruit stored
2.4. Hypobaric studies1997/98
‘Law Rome’ and ‘Granny Smith’ fruit were stored hypobarically or in air at 1°C. Fruit were placed under hypobaric storage immediately after harvest or after 0.5, 1, 2, 3, 4, 5 or 6 months storage in air at 1°C to determine the effects of delaying imposition of hypobaric storage on ripening and scald development, and production
ofa-farnesene and MHO. After total 6 months of
storage, fruit were removed from hypobaric or air storage and transferred to 20°C in air in 4-l glass
jars. a-Farnesene and MHO production rates at
daily or bi-daily intervals were measured as
de-Table 2
Effect of hypobaric (5 kPa of air) or controlled atmosphere (CA) and/or air storage on scald development of ‘Granny Smith’ and ‘Law Rome’ apples at 1°C in 1996
Scald indexa
Fig. 1. Effect of delaying hypobaric storage on control of scald of ‘Granny Smith’ and ‘Law Rome’ apples. Fruit was stored in air at 1°C prior to storing them hypobarically at 5 kPa in air. After 6 months of storage, fruit were removed from hypobaric storage and scald index (0=none; 1=slight; 2=moderate; 3=severe) was measured after 7 days poststorage at 20°C. The Scald index was normalized to 100 by multiplying the values by 100/3.
Progressively longer periods of storage in air at 1°C before ‘Granny Smith’ apples were placed in hypobaric storage resulted in a greater burst of
a-farnesene production (Fig. 2A), but in contrast,
for ‘Law Rome’ fruit a nearly opposite trend was
found (Fig. 2B). a-Farnesene production rates
were highest for ‘Law Rome’ apples stored hypo-barically within 1 month after harvest but lowest in ‘Granny Smith’ apples treated similarly. The
a-farnesene production of ‘Granny Smith’ fruit
placed in hypobaric storage within 1 month of harvest steadily increased after transferring the fruit to air at 20°C, eventually matching or ex-ceeding that of fruit stored after 2 months delay
(Fig. 2A). The amount of a-farnesene partitioned
in the cuticle largely followed the pattern of its volatilization into the headspace from whole fruit
(Fig. 2C). Upon transfer to 20°C, the a-farnesene
evolution rate from cuticle of ‘Law Rome’ apples
Fig. 2. Change ina-farnesene levels in headspace (A, B) and in
the epicuticular wax (C, D) of ‘Granny Smith’ (A, C) and ‘Law Rome’ (B, D) apples stored in air for 0 – 6 months before hypobaric storage at 5 kPa in air.
hypobarically for 8 months plus 4 months in air did not develop scald (Table 2), whereas scald did develop after an additional 6 months of storage in air. ‘Granny Smith’ and ‘Law Rome’ fruit stored
under CA with 1.5% O2 for 8 months developed
slight scald with indices of 8.3 and 10.3, respec-tively; those stored for 2 months in CA then
moved to air or those under CA at 3% or more O2
scalded severely (Table 2). Collectively, the data indicate that apples stored hypobarically do not scald during storage but may do so after subse-quent extended periods of time in a static air atmosphere (Table 2). Moreover, CA storage con-trols scald less effectively than hypobaric storage.
3.2. Hypobaric studies1997/98:
Fig. 3. Change in 6-methyl-5-hepten-2-one (MHO) levels in headspace (A, B) and in the epicuticular wax (C, D) of ‘Granny Smith’ (A, C) and ‘Law Rome’ (B, D) apples stored in air for 0 – 6 months before hypobaric storage at 5 kPa in air.
storage (Fig. 3C,D).
Based on the measurements taken for five dif-ferent cvs. including scald susceptible and
resis-tant cvs., the production rates ofa-farnesene and
MHO were low during 7 months of hypobaric storage but quickly increased upon removal from storage and transfer to air at 20°C. The rates then, decreased sharply after about a week (Fig. 4). The ‘Granny Smith’ cv. had the lowest rates among the five cvs. examined. None of the cvs. stored hypobarically scalded, whereas all scalded except ‘Golden Delicious’ when stored in air. In comparison, MHO evolution from air-stored ‘Granny Smith’ fruit after 5.5-months storage and transfer to 20°C, was 5-fold higher than that hypobarically stored fruit (data not shown).
Fig. 4. Change in headspace levels ofa-farnesene (A) and its
oxidation product 6-methyl-5-hepten-2-one (B) for different cultivars of apples after 7 months of hypobaric storage at 1°C and transfer to 20°C in air in 1997. (Scald did not develop on any fruits stored hypobarically but developed on all others except ‘Golden Delicious’ stored in air at atmospheric pres-sure.)
was higher for apples which were placed under hypobaric condition within 2 months than for those hypobarically stored after more than 2 months in air (Fig. 2D). This again mimicked the
pattern of the rate of a-farnesene evolution into
the headspace by whole apples.
4. Discussion
4.1. Remo6ing6olatiles controls scald
Hypobaric storage favors the removal of ethylene and other volatile substances produced by the fruit (Dilley, 1982). A low rate of synthesis coupled with continuous removal of these sub-stances by hypobaric ventilation results in com-plete control of scald during storage and even after the fruit are returned to a static air atmo-sphere for a few months. This indicates that the
fruit produce/accumulate some substance related
to scald development and that this can be greatly attenuated by hypobaric storage. That hypobar-ically stored fruit eventually scald when trans-ferred to air, suggests that hypobaric storage does not irreversibly inhibit scald development. Fur-thermore, since only 2 months of hypobaric stor-age was sufficient to largely prevent scald, this indicates that scald induction occurs primarily during the first few months of storage at low temperature. And, unless removed during this time frame, the action of this volatile may eventu-ally cause the fruit to scald. These data are consis-tent with the observations that fruit do not scald when flow-through CA is employed either in the
lab or commercially at 1.5% O2 with 3% CO2.
While hypobaric storage can prevent scald, fruit must be placed under these conditions within about 1 month after harvest (Fig. 1). Fruit stored in air at 1°C for 2 months or longer prior to placing them under hypobaric storage at 5 kPa developed scald following storage, while those kept in air for progressively shorter times before hypobaric storage did not. This is significant, because it indicates that the metabolism involved in scald development becomes irreversible after 2 months of storage in air. Moreover, although hypobaric storage favors the removal of all volatiles produced by the fruit, none of these volatiles, includinga-farnesene and its breakdown
products can be implicated as factors in scald beyond the initial 2 months of storage. A trienol
oxidation product ofa-farnesene has been
impli-cated in scald (Whitaker, et al., 1997). However, it is not appreciably volatile. This may, however, be involved during the early period during which the
potential for scald development is gained by stor-age in air (Shutak and Christopher, 1960; Meigh, 1970; Watkins et al., 1995). These results are consistent with the observation that for dipheny-lamine (DPA) to be effective in controlling scald it must be applied within a few weeks of placing the fruit in air storage (Dilley and Dewey, 1963). In addition, these studies reinforce the concept that scald is a chilling injury phenomenon (Watkins et al., 1995).
Volatiles that can be removed by effective venti-lation may be involved in scald development. DPA has been shown to attenuate conversion of
a-farnesene to triene hydroperoxides (Anet and
Coggiola, 1974) and to MHO (Mir and Beaudry, 1999). Since hypobaric storage favors the removal of ethylene and other volatile substances pro-duced by the fruit, this suggests some involvement of a volatile substance (Jamieson, 1980; Dilley, 1982). But if fruit were stored hypobarically only a couple of months, scald still developed after many months of subsequent storage in air (Table 1), indicating that short term hypobaric storage does not irreversibly inhibit scald development. Continuous removal of those volatile substances by hypobaric ventilation for longer time results in complete control of scald even after the fruit are returned to a static air atmosphere for up to 4 months (Table 2). This suggests that the ability of fruit to produce some metabolite(s) or factor(s) related to scald development has been altered by hypobaric ventilation.
4.2. In6ol6ement of a-farnesene and MHO
The role of a-farnesene and MHO was also
assessed in scald development. The pattern of
a-farnesene evolution/volatilization following
hy-pobaric storage was similar for five cvs. examined in 1996 (Fig. 4A). Moreover, the production levels are similar to those of fruit stored in CA and
scald develops during CA (1.5% O2and 0% CO2)
storage. The ability of the fruit to produce the
a-farnesene oxidation product MHO was also
demonstrated. Fruit stored hypobarically for 7 months did not develop scald. The evolution rates
of a-farnesene and MHO were initially low but
transfer to air at 20°C, following by a sharp decline (Fig. 4). CA storage at ultra-low O2levels
of ca. 1% can reduce but not prevent scald, and
this largely arrests conversion of a-farnesene to
MHO (Wang and Dilley, 2000). Static CA is less effective in controlling scald than ventilated CA at
the same O2 partial pressure (Dilley, 1990), which
suggests that ventilation removes some
scald-re-lated volatile from the storage atmosphere
(Brooks et al., 1919; Fidler, 1950). Moreover, the tissue surrounding open lenticels generally does not scald. Removing the cuticle prevents scald (Shutak and Christopher, 1960) and a needle puncture of the cuticle prevents scald of the adja-cent areas (Abdallah et al., 1997). Collectively, these observations support the premise that some volatile may be involved in scald. Hypobaric ven-tilation apparently removes a volatile substance that otherwise accumulates, perhaps by partition-ing the substance into the epicuticular wax.
Mir et al. (1998) found that a burst of MHO production by ‘Cortland’ apples occurred upon transferring fruit from storage in air at 0 – 20°C and this was correlated with scald development. MHO production was detected only in scalding fruit (Mir and Beaudry, 1999). Exogenous appli-cation of MHO vapor induced a scald-like skin browning in nine cvs. of apples and symptom development was greatest in scald-susceptible as compared with scald-resistant cvs. (Song and Beaudry, 1996). All cvs. of hypobarically-stored fruit produced MHO when transferred to air at 20°C but none of them developed scald; scald-re-sistant and scald susceptible cvs. produced similar levels of MHO. In fact, the highly scald-suscepti-ble ‘Granny Smith’ cv. produced the least amount of MHO (Fig. 4). This strongly suggests that MHO may not be the factor or only factor
caus-ing scald development. However, air-stored
‘Granny Smith’ apples which scalded produced MHO at a 5-fold greater rate when transferred to 20°C than those stored hypobarically. The data also indicate that MHO is not produced as a consequence of scald development. The dramatic
increase then decrease in a-farnesene production
at 20°C was seen in all cvs. and virtually all treatments (Fig. 4). Very interestingly,a-farnesene
production abruptly decreased after 7 days while
the MHO production rate was still increasing. Changes in MHO followed the same trend as
changes in a-farnesene except for a couple of
days’ delay (Fig. 4). This suggests that the trends are not due to aberrancies of analysis. These data clearly support the notion that MHO is derived
from a-farnesene.
It is possible that cultivars may differ from season to season in sensitivity to MHO. It is also possible that hypobarically stored fruit may lack the mechanism for MHO to cause scald. Alterna-tively, the action of MHO may be temporal or require participation of a yet to be determined co-factor. Fidler (1950) suggested that a volatile substance (Y) in addition to a non-volatile sub-stance (X) was necessary to explain the vagaries of the scald disorder. Moreover, that X must be present before Y is active. If, indeed, MHO is Fidler’s substance Y, the nature of X remains to be elucidated. The hypobaric studies are some-what consistent with Fidler’s hypothesis that two factors are needed for scald development in that the level of factor X was reduced by hypobaric ventilation if applied early or continuously. How-ever, both X and Y (MHO) would be volatiles.
Some portions of the fruit surface scald while adjoining portions do not scald. Yet, all cells
would be expected to produce a-farnesene and
MHO. Fruit lose susceptibility to scald as they mature (Couey and Williams, 1973; Hammett, 1976) while they obviously gain capacity to
pro-duce a-farnesene and MHO as they ripen. Levels
of natural antioxidants may mitigate scald devel-opment (Anet, 1972, 1974; Meir and Bramlage, 1988; Gallerani et al., 1990; Whitaker, 1998). The level of the natural antioxidant ascorbic acid in-creases as apple fruit mature, whereas other wa-ter-soluble antioxidants generally decrease during storage (Barden and Bramlage, 1994a,b); ascorbic acid and other natural antioxidants may be pro-tected from degradation when fruit are stored hypobarically. The correlation of the disorder with the pigment bearing cells of the hypodermis implicates pathways of pigment biosynthesis (Zu et al., 1996). These are the cells wherea-farnesene
is produced and oxidized. It is apparent that susceptibility of fruit to the scald disorder is
ethylene action since inhibition of ethylene action by diazocyclopentadiene can lower levels ofa
-far-nesene and conjugated trienols and control scald (Gong and Tian, 1998).
References
Abdallah, A.Y., Gil, M.I., Biasi, W., Mitcham, E.J., 1997. Inhibition of superficial scald in apples by wounding: changes in lipids and phenolics. Postharvest Biol. Technol. 12, 203 – 212.
Anet, E.F.L.J., 1972. Superficial scald, a functional disorder of stored apples: VIII. Volatile products from the autoxida-tion ofa-farnesene. J. Sci. Food Agric. 23, 605 – 608.
Anet, E.F.L.J., 1974. Superficial scald, a functional disorder of stored apples: XI. Apple antioxidants. J. Sci. Food Agric. 25, 299 – 304.
Anet, E.F.L.J., Coggiola, I.M., 1974. Superficial scald, a func-tional disorder of stored apples: X. Control ofa-farnesene
autoxidation. J. Sci. Food Agric. 25, 293 – 298.
Barden, C.L., Bramlage, W.J., 1994a. Relationships of antiox-idants in apple peel to changes in a-farnesene and
conju-gated trienes during storage, and to superficial scald development after storage. Postharvest Biol. Technol. 4, 23 – 33.
Barden, C.L., Bramlage, W.J., 1994b. Accumulation of antiox-idants in apple peel as related to preharvest factors and superficial scald susceptibility of the fruit. J. Am. Soc. Hort. Sci. 119, 264 – 269.
Brooks, C., Cooley, I.S., Fisher, D.F., 1919. Nature and control of apple scald. J. Agric. Res. 18, 211 – 240. Burg, S.P., Burg, E.A., 1966. Fruit storage at subatmospheric
pressures. Science 153, 314 – 315.
Couey, H.M., Williams, M.W., 1973. Preharvest application of ethephon on scald and quality of stored ‘Delicious’ apples. HortScience 8, 56 – 57.
Dilley, D.R., 1972. Hypobaric storage — a new concept for preservation of perishables. Proc. Mich. State Hort. Soc. 102, 82 – 89.
Dilley, D.R., 1982. Principles and effects of hypobaric storage of fruits and vegetables. Am. Soc. Heating Refrigeration Air Conditioning Eng. Trans. 88, 1461 – 1478.
Dilley, D.R., 1990. Application of air separator technology for the control of superficial scald of apples not treated with scald inhibiting chemicals. Proc. 23 Int. Hort. Congress, Firenze, Italy, August 27 – September 1, 1990, pp. 656. Dilley, D.R., Dewey, D.H., 1963. Dip treatment of apples in
bulk boxes with diphenylamine for control of storage scald. Mich. Agric. Exp. State Q. Bull. 46, 73 – 79. Fidler, J.C., 1950. Studies of the physiologically-active volatile
organic compounds produced by fruits: The rate of pro-duction of carbon dioxide and volatile organic compounds by King Edward VII apples in gas storage, and the effect of the removal of the volatiles from the atmosphere of the store in the incidence of superficial scald. J. Hort. Sci. 25, 81.
Gallerani, G., Pratella, G.C., Budini, R.A., 1990. The distribu-tion and role of natural antioxidant substances in apple fruit affected by superficial scald. Adv. Hort. Sci. 4, 144 – 146.
Gong, Y., Tian, M.S., 1998. Inhibitory effect of diazocy-clopentadiene on the development of superficial scald in Granny Smith apple. Plant Growth Regul. 26, 117 – 121. Hammett, L.K., 1976. Ethephon influence on storage quality
of ‘Starkrimson Delicious’ and ‘Golden Delicious’ apples. HortScience 11, 57 – 59.
Jamieson, W., 1980. Use of hypobaric conditions for refriger-ated storage of meats, fruits, and vegetables. Food Tech-nol. 1980, 64 – 71.
Meigh, D.F., 1970. Apple scald. In: Hulme, A.C. (Ed.), The Biochemistry of Fruits and Their Products, vol. 1. Aca-demic Press, London, pp. 555 – 569.
Meir, S., Bramlage, W.J., 1988. Antioxidant activity in ‘Cort-land’ apple peel and susceptibility to superficial scald after storage. J. Am. Soc. Hort. Sci. 113, 412 – 418.
Mir, N., Beaudry, R., 1999. Effect of superficial scald suppres-sion by diphenylamine application on volatile evolution by stored Cortland apple fruit. J. Agric. Food Chem. 47, 1 – 11.
Mir, N., Perez, R., Beaudry, R., 1998. A post-storage burst of 6-methyl-5-hepten-2-one from Cortland apple fruit may be related to scald development. J. Am. Soc. Hort. Sci. 124, 173 – 176.
Shutak, V., Christopher, E.P., 1960. Role of the cuticle in development of storage scald on Cortland apples. Proc. Am. Soc. Hort. Sci. 76, 106 – 111.
Song, J., Beaudry, R.M., 1996. Rethinking apple scald: new hypothesis on the causal reason for development of scald in apples. HortScience 31 (Abstract), 605.
Song, J., Gardner, B.D., Holland, J.F., Beaudry, R.M., 1997. Rapid analysis of volatile flavor compounds in apple fruit using SPME and GC/time-of-flight mass spectrometry. J. Agric. Food Chem. 45, 1801 – 1807.
Spalding, D.H., Reeder, W.F., 1976a. Low pressure (hypo-baric) storage of limes. J. Am. Soc. Hort. Sci. 10, 367 – 370. Spalding, D.H., Reeder, W.F., 1976b. Low pressure
(hypo-baric) storage of avocados. HortScience 11, 491 – 492. Wang, Z., Dilley, D.R., 1997. The relationship ofa-farnesene
production and its oxidation product 6-methyl-5-hepten-2-one to superficial scald of Granny Smith, Law Rome, Red Delicious and Idared apples during controlled atmosphere and air storage. Proc. 7th Int. Controlled Atmosphere Res. Conf. 2, 98 – 104.
Wang, Z., Dilley, R.D., 2000. Initial low oxygen stress con-trols superficial scald of apples. Postharvest Biol. Technol. 18, 201 – 213.
Watkins, C.B., Bramlage, W.J., Cregoe, B.A., 1995. Superficial scald of granny Smith apples is expressed as a typical chilling injury. J. Am. Soc. Hort. Sci. 120, 88 – 94. Whitaker, B.D., 1998. Phenolic fatty-acid esters from the peel
Whitaker, B.D., Solomos, T., Harrison, D.J., 1997. Quantifi-cation ofa-farnesene and its conjugated trienol oxidation
products from apple peel by C18-HPLC with UV detection. J. Agric. Food Chem. 45, 760 – 765.
Zu, Z., Yuan, Y., Liu, C., Zhan, S., Wang, M., 1996. Rela-tionship among simple phenol, flavonoid and anthocyanin in apple fruit peel at harvest and scald susceptibility. Postharvest Biol. Technol. 8, 83 – 93.
