Postharvest Biology and Technology 18 2000 99 – 107
Effect of 1 and 100 kPa O
2
atmospheric pretreatments of whole ‘Spartan’ apples on subsequent quality and shelf life
of slices stored in modified atmosphere packages
Changwen Lu, Peter M.A. Toivonen
Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, Summerland, BC, Canada V H
1
Z Received 3 March 1999; accepted 30 September 1999
Abstract
Whole ‘Spartan’ apples were exposed to 1 kPa O
2
, air 21 kPa O
2
and 100 kPa O
2
at 1°C for 5, 12 and 19 days. Subsequent to the pretreatment, apples were cored, sliced and 400 9 5 g of slices were sealed in 40-mm-thick low
density polyethylene film bags having a moderate O
2
transmission rate OTR 2.28 fmol s
− 1
m m
− 2
Pa
− 1
at 23°C and held for up to 2 weeks at 1°C. Cut surface browning and flesh softening were inhibited for packaged slices by
pretreating the whole fruit with 100 and 1 kPa O
2
as compared with those from the air pretreatment. However the slices from the 100 kPa O
2
- and air-pretreated apples contained a much lower content of fermentation products associated with off-flavors compared with the slices from apples pretreated in 1 kPa O
2
. Packages containing apple slices from the air pretreatment developed a more highly modified atmosphere than packages containing apples slices
from the other two pretreatments, suggesting that both 1 and 100 kPa O
2
pretreatments suppressed the respiration rate of apple slices. Slices from apples pretreated with 1 kPa O
2
developed more cut surface browning and greater tissue solute leakage and enhanced accumulations of acetaldehyde, ethanol and ethyl acetate in apple slice tissue as
compared with slices cut from the 100 kPa O
2
-pretreated apples. © 2000 Elsevier Science B.V. All rights reserved.
Keywords
:
Fermentation products; Pure oxygen; Browning; Solute leakage; Respiration; Firmness www.elsevier.comlocatepostharvbio
1. Introduction
Fresh-cut products comprise approximately 10 of all fresh produce sold in North America
and it is expected by the year 2000 that 25 of all produce sold will be in fresh-cut form Vance
Publishing, 1996. Fresh-cut, packaged and ready- to-eat vegetables already have a significant market
share and recently processors have begun placing more emphasis on the development of the fresh-
cut fruit market. Unfortunately, it is difficult to consistently assure reasonable shelf life in fresh-
cut fruit products due to the fact that many fruits must be processed at their optimal ripening qual-
ity and therefore are at the brink of senescence Gorny and Kader, 1996. Most of the current
This article is Centre Contribution Number 2022. Corresponding author. Tel.: + 1-250-4946386; fax: + 1-
250-4940755. E-mail address
:
toivonenpem.agr.ca P.M.A. Toivonen 0925-521400 - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 5 - 5 2 1 4 9 9 0 0 0 6 9 - 1
research has focussed on post-cutting processes and application of anti-browning chemicals or
artificial coatings Baldwin et al., 1996; Gil et al., 1998. Post-cutting application of low O
2
or pure N
2
atmospheres have been shown to be useful in delaying apple slice softening and browning, but
these atmospheres can induce flavor problems due to accumulation of acetaldehyde, ethanol, ethyl
acetate and other volatiles Toivonen, 1997. In terms of chemical approaches, ascorbic acid vita-
min C has been widely used as an anti-browning additive Vamos-Vigyazo, 1981. However, ascor-
bic acid is quickly consumed in the anti-browning process, and thus provides only temporary protec-
tion Vamos-Vigyazo, 1981; Sapers, 1993. The fresh-cut industry would like to use approaches to
maintain fresh flavor, color and texture of cut fruit with little or no addition of chemical addi-
tives Anon., 1995, therefore non-chemical treat- ments are of interest.
It is generally accepted that O
2
plays a major role in apple browning Whitaker et al., 1998.
Reduced O
2
atmospheres have been shown to be beneficial in maintaining quality and extending
the shelf life of apple slices Nicoli et al., 1994; Gil et al., 1998 as well as pear and strawberry slices
Rosen and Kader, 1989. Low O
2
atmospheres inhibit color and texture changes of sliced
‘Granny Smith’ apples, however, they cause devel- opment of off-flavors Ke et al., 1991 and fer-
mentative deterioration Watada et al., 1998. Recent research on quality changes of several
fresh-cut fruits, has shown that low oxygen atmo- sphere storage has significant inhibitory effects on
the respiration and ethylene production as well as quality retention Qi and Watada, 1997. Using a
different approach, researchers have recently tested the use of superatmospheric O
2
levels on fruit. Solomos et al. 1997 applied pure O
2
to whole ‘Gala’ and ‘Granny Smith’ apples and this
treatment reduced both respiration rate and ethylene production rate to similar levels as low
O
2
treatment when applied at 18°C. It has also been found that pure O
2
atmosphere treatment for 4 weeks at 2°C inhibits both cut surface
browning and chilling injury in peaches Lu and Solomos, unpublished data.
Whole fruit have been shown to be more able to adapt to stresses such as chilling than cut pieces
of the same fruit Kang and Lee, 1997. Therefore it was hypothesized that pretreatment of whole
apple fruit prior to slicing could provide an ap- proach to modifying deterioration of tissue when
it is subsequently sliced and packaged rather than applying the treatment after the fruit had been
cut. The objective of this work was to investigate and compare the effects of 1 and 100 kPa O
2
pretreatments in whole apple fruit and their resid- ual effect on shelf life of subsequently cut slices.
Changes in cut surface color, tissue solute leak- age, firmness and the accumulations of acetalde-
hyde, ethanol and ethyl acetate were evaluated for apple slices that had been cut from whole apples
pretreated in 100 kPa O
2
, 21 kPa O
2
air control and 1 kPa O
2
and stored 14 days in modified atmosphere packages.
Two different experiments were conducted. The first experiment was designed to evaluate the ef-
fect of pretreatment duration of whole apples with 1, 21, and 100 kPa O
2
atmospheres on subsequent quality of packaged slices, made from the whole
apples, at 14 days of storage. The second experi- ment was designed to evaluate both quality and
physiological changes in packaged slices made from apples that had been pretreated for 12 days
with 1, 21, and 100 kPa O
2
atmospheres prior to slicing.
2. Materials and methods
