Postharvest Biology and Technology 19 2000 129 – 137
Ascorbic acid and tissue browning in pears Pyrus communis L. cvs Rocha and Conference under controlled atmosphere
conditions
R.H. Veltman , R.M. Kho, A.C.R. van Schaik, M.G. Sanders, J. Oosterhaven
Agro-Technological Research Institute ATO
, Bornsesteeg
59
, PO Box
17
,
6700
AA, Wageningen, The Netherlands Received 17 December 1998; accepted 6 March 2000
Abstract
The relationships between storage gas composition and ascorbic acid AA levels, and between AA levels and the development of internal browning, were studied in ‘Conference’ and ‘Rocha’ pears Pyrus communis L.. In both
cultivars, AA levels declined under browning-inducing controlled atmosphere CA conditions, i.e. lowered O
2
and enhanced CO
2
concentrations. Browning was initiated in a cultivar-dependent manner when an AA level threshold was passed. Several models describing the relation between AA levels and browning were fitted to estimate these AA
thresholds. The thresholds depend on cultivar, picking date and growing location, varying between 2 and 6 mg 100 g FW
− 1
. AA losses in both cultivars exceeded 50 of the initial values. In ‘Conference’ fruit, most AA was lost when fruits were transferred to CA. In ‘Rocha’ fruit, AA was lost mainly during long-term CA. © 2000 Elsevier Science
B.V. All rights reserved.
Keywords
:
Ascorbic acid; Brown core; CA storage; Pear; Pyrus communis; Vitamin C www.elsevier.comlocatepostharvbio
1. Introduction
Ascorbic acid AA is an antioxidant, which acts against reactive O
2
species in concert with other antioxidants such as glutathione and a-to-
copherol, in a system referred to as the ascor- bate – glutathione cycle Jime´nez et al., 1997. AA
may also be involved in the conversion of 1- aminocyclopropane-1-carboxylic acid ACC to
ethylene Smith et al., 1992, and in photosynthe- sis, where it removes hydrogen peroxide formed
during photoreduction in PSI Smirnoff, 1996.
AA is not only important during the life of plants and during storage or shelf-life of fruits,
but also for human health. In this regard, AA is a quality parameter of fruits, and should be kept at
an appropriate level. AA levels, however, tend to decrease during storage and processing of fruits
and vegetables.
Corresponding author. Tel.: + 31-317-475000; fax: + 31- 317-475347.
E-mail address
:
r.h.veltmanato.wag-ur.nl R.H. Veltman 0925-521400 - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 5 - 5 2 1 4 0 0 0 0 0 9 5 - 8
Generally AA levels in various apple cultivars are lower under ultra low oxygen ULO condi-
tions than under air in cold storage Haffner et al., 1997. Levels slowly decrease both under CA
and during air storage in ‘Boskoop’ and ‘Golden Delicious’ apples Gerber, 1958; Bohling and
Hansen, 1985, and they slowly decline in pota- toes during storage by as much as 16 of the
original amount after 8 or 9 months Nobile and Woodhill, 1981.
In pears, a relationship was found between AA content and the susceptibility to browning during
experimental storage under various brown core- inducing conditions Veltman et al., 1999. ‘Con-
ference’ pears tend to develop tissue disorders, like brown core, when AA levels drop below a
certain value.
In this paper, we tested and expanded on these results. Pears were monitored in a static system,
and gas conditions and storage temperatures were comparable to those in commercial practice. AA
levels and the susceptibility towards browning in ‘Conference’ and ‘Rocha’ pears were monitored
during CA storage throughout the season. AA and browning values are discussed in relation to
storage conditions, harvest date and growing location.
2. Materials and methods
