Mangoes could be an
attractive addition to the growing market for fresh-cut produce, but browning
and drying have prevented such marketing. Researchers at the USDA-ARS Horticultural
Crops Quality Laboratory found that fresh-cut mangoes could be preserved
by treating the slices with a combination of hexylresorcinol, isoascorbic
acid and potassium sorbate (all food-safe compounds derived from natural
products) and storing the slices in plastic containers to prevent drying.
Treating whole fruits
with methyl jasmonate (an inexpensive product derived from plant essential
oils) prevented the development of chilling injury during cold storage
and hence markedly increased fruit quality after storage. The treatment
worked on fruits at various stages of maturity and had no effect on ripening
or softening processes or water loss.
For further information
contact: Chien Y. Wang, USDA-ARS Horticultural Crops Laboratory, Beltsville,
Maryland, USA. Tel: (301) 5046128 Email: cwang@asrr.arsusda.gov
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FAIR
Project Assesses Mealiness in Apples
Participants in the
European FAIR project (CT 95-302) developed non-destructive techniques
for the measurement of mealiness in apples and studied the factors affecting
mealiness and its effects on consumers.
Mealiness is described
as the tendency of fruits to disintegrate, combined with a sensation of
lack of juiciness and dryness in the mouth, as well as the absence of flavour.
In December 1996, researchers from the Universidad Politécnica de
Madrid (UPM), from Katholieke Universiteit Leuven (KU) and from the Institute
of Food Research in the UK carried out trials to determine correlations
between the assessment of mealiness by a panel and objective measurements
(mechanical resonance and confined compression). The results allowed the
development of techniques for determining crispness (the absence of which
is correlated with mealiness), hardness and juiciness (also correlated
with mealiness) without the need for taste panels.
A scale for determining
mealiness was used by UPM, in collaboration with IRTA (Spain), for studying
factors which could affect the incidence of mealiness in apples. The studies
concluded that (i) large-size Top Red apples harvested late showed a high
incidence of mealiness, and (ii) no effect of harvesting date on mealiness
was observed in Golden Delicious apples, although fruit size and mealiness
were linked. Similar studies carried out at KU and VCBT (Flemish Centre
for Storage of Agricultural Products), combining harvesting dates, fruit
size and the concentration of oxygen in the storage atmosphere, showed
that, after 6 months' storage, apples stored in air showed a higher incidence
of mealiness than those held in a low-oxygen atmosphere.
Surveys of producers,
distributors and consumers indicated that all groups perceived mealiness
as detrimental to fruit quality, although there was a segment of older
consumers who preferred mealy fruits because they were softer and overmature.
The quality characteristic rated highest was taste, followed by appearance
and firmness.
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Hawaiian
Bananas Free from Fruit Flies
Research carried out
by John W. Armstrong and colleagues at the US Pacific Basin Agricultural
Research Center in Hilo, Hawaii has allowed the USDA's Animal and Plant
Health Inspection Service to approve new, workable regulations for shipping
bananas grown in Hawaii to the US mainland. Since the ban on ethylene dibromide
was imposed in 1984, bananas have not been shipped to the mainland due
to the threat of fruit fly infestation. Mediterranean (Ceratitis capitata)
and oriental fruit flies (Bactrocera dorsalis) are established in
Hawaii and pose a threat to mainland agriculture where they can attack
more than 200 fruits and vegetables.
Using laboratory-reared
fruit flies, thousands of bananas from nearly 2 dozen plantations throughout
the State were tested. The research, carried out in the laboratory and
outdoors, demonstrated that bananas won't harbour these pests if shipped
full-size, green-skinned and without cuts or punctures. Shipments to other
markets such as Japan are now on the horizon.
For further information contact:
John Armstrong, USDA-ARS,
US Pacific Basin Agricultural Research Center, Stainback Highway,
PO Box 4459, Hilo, HI 96720, USA.Tel:
(808) 959 4336, Fax: (808) 959 4323
Email: jwa@aloha.net
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Postharvest
Calcium Drench Research
CaCl2, used
as a postharvest drench on many apple cultivars, can increase calcium levels,
reduce the incidence of bitter pit and other calcium-related physiological
disorders, and improve fruit firmness, storage potential and packout.
Research has been carried
out in the UK at HRI (East Malling) on postharvest application of the Phosyn
product Stopit (a CaCl2 formulation) on Braeburn apples. Part
of this research involved photographs being taken using a scanning electron
microscope looking over the surface of apple tissue plugs. The research
showed skin quality to be of major importance. Fruits with poor skin quality
had an increased susceptibility to damage from CaCl2. Some fruits
had uneven, broken skin from heat and drought stress, making them more
susceptible to damage. Also, many of these fruits had high residues of
CaCl2 on the skin from excessive spray applications preharvest
which also put the fruits further at risk of damage. Visual examination
of fruits before treatment may help in deciding whether to use posharvest
calcium drench but apple skins can be sensitized without this being apparent
to the naked eye.
Phosyn have now set
international guidelines covering the postharvest application of Stopit
on apples. These are listed in a booklet, which is part of a kit available
to packhouse operators using Stopit in their drench plants. The kit consists
of the booklet, guidelines and a sample bottle to test the dilution of
the drench solution.
For further information
contact:
Phosyn plc - Head Office,
Manor Place, Wellington Road, The Industrial Estate, Pocklington,
York YO42 1DN, UK. Tel: +44 1759 302545 Fax: +44 1759 303650 Telex: 57679,
Email: postbox@phosyn.com
From: The Orchardist
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Postharvest
2000. 4th International Conference on Postharvest Science, Jerusalem, Israel,
26-31 March 2000
A most successful International
Society for Horticultural Science (ISHS) Symposium was held in Jerusalem,
Israel, 26-31 March 2000. Convened by Professor Ruth Ben-Arie and her formidable
Organizing Committee, this action-packed Symposium was appreciated and
enjoyed by over 400 registrants from more than 40 countries. With scientific
sessions spread over 3 days, separated by an excellent choice of 4 professional
tours to various parts of this extraordinary diverse country, participants
were fortunate to be exposed to a broad range of up-to-the-minute topics
covering the broad range of subjects that comprise postharvest science.
Each day commenced with
a plenary session in which a leading expert in the field gave an overview
of pertinent and relevant subjects. Professor Don Grierson, University
of Nottingham, UK, in his characteristically inimical style, provided an
erudite and dispassionate (and sometimes passionate) outline of the advances
and prospects made in biotechnology for postharvest. He outlined the potential
for molecular biology to contribute to both an understanding of maturation
and senescence processes that lead to postharvest problems in fresh products,
as well as describing potential benefits that genetic manipulation holds
for improving food quality and reducing losses in both developed and developing
countries.
Dr Dov Prusky from the
Volcani Research Center in Israel, provided an elegant and broad ranging
discussion of mechanisms influencing susceptibility to diseases and the
process of pathogenesis for postharvest pathogens in important horticultural
crops. Drawing from a wide range of sources, as well as recent unpublished
work in Israel, he was optimistic about the opportunities for modern technologies
to help solve some of the basic conundrums still facing pathologists and
suggested future research options for reducing food losses resulting from
postharvest diseases.
Programmed cell death
(is it or is it not apoptosis?), a topic receiving widespread attention
in the animal research world, is also being examined increasingly in plants;
it clearly plays a major role in physiological disorders, cellular responses
to stress as well as the senescence process in fruits and vegetables. Dr
Ian Ferguson, HortResearch, New Zealand, gave a laconic, fluent and incisive
explanation of the subject, drawing heavily on experiments from his laboratory
where the use of flow cytometry techniques is allowing ever more detailed
investigation of cell death events derived from a number of different causes.
Much more will be learned about postharvest problems and processes as this
type of work is developed in laboratories utilizing such tools.
A timely reminder that
quality in the eyes of the consumer constitutes many attributes and that
flavour and aroma, as well as crispness and juiciness, will increasingly
become key decision making features with buyers of fresh fruit and vegetables,
was provided by Professor Adel Kader, University of California, USA. He
reminded the audience that introduction of quality assurance systems to
all crops was essential for the successful development and retention of
markets, and that benefits were to be gained by developing systems that
were consistent and took into account a wider spread of attributes than
those commonly used today. The ability to segregate product lines as a
result of non-destructive techniques for measuring quality in line, has
become possible through the development of a range of technologies, some
of which are now being introduced into commercial packhouses.
The remaining sessions were concurrent
and covered the main topics of interest to postharvest scientists. Inevitably
the importance of the Symposium topic (perhaps rivalled by the significance
of the venue in this momentous year 2000) meant that there were a large
number of oral and poster presentations that could only be presented in
multiple or concurrent sessions. For those who were interested in all topics
some difficult choices had to be made about which sessions to attend. However,
all the sessions were well attended and the overall quality of both poster
and oral presentations was excellent.
Overall there were 145 oral and more
than 200 poster presentations. Topics dealt with in detail included: sensor
technology and non-destructive quality assessment; developmental regulation
from germination to senescence; texture and cell wall metabolism; preharvest
effects on postharvest behaviour; plant growth regulators and ethylene;
colour and pigmentation; volatiles including flavour and scent compounds;
refrigeration; senescence; CA/MAP technology; coatings and waxes; biological
control and host resistance; alternatives to chemical control of postharvest
pests and diseases; quarantine related issues; freshcut produce; food safety;
physiological disorders; postharvest trends in developing countries; future
trends and postharvest science in the new Millennium.
In addition to the main programme,
a representative from the EU outlined new programmes whereby collaborative
projects between EU and developing countries might be funded with the objective
of providing R&D support for projects that would improve both scientific
expertise and food security in developing countries. This programme is
commended to postharvest scientists in appropriate countries, who should
actively seek funds to further postharvest R&D and associated technology
transfer activities.
A Business meeting of the Postharvest
Commission of the ISHS was well attended and final decisions were made
as to the postharvest topics that will form the basis of Postharvest Symposia
at the XVI International Horticultural Congress in Toronto 2002. Approval
was given for the Commission to re-organize its structure to form two new
Working Groups, one on Controlled Atmosphere Storage, (the next CA Conference
to be held in Rotterdam, 8-13 July 2001), and the second to develop strategies
for the Commission to become involved in postharvest science in developing
countries. Finally the decision was made that the venue for the next Postharvest
Symposium in this series will be in Verona, Italy in 2004 with Dr Pietro
Tonutti being Convenor, assisted by Dr Fabio Mencarelli and the postharvest
group within the Italian Society for Horticultural Science.
Professional tours were to the northern
part of the country including Upper Galilee and the Golan Heights, the
Lower Galilee, to see exotic crop production the southern desert and to
visit the Postharvest and Storage Laboratory, Bet Dagan, Volcani Center.
All participants appreciated each of these visits, having the chance to
see a small part of what constitutes a very successful horticultural industry.
In addition, most participants took the opportunity to visit both the old
and new city of Jerusalem, made easier when His Holiness the Pope had completed
his momentous visit to this special city.
This was an extremely successful Symposium,
enjoyed by a large gathering of Postharvest scientists. Congratulations
to Ruth Ben-Arie and her team for making this such a special event. Proceedings
will be published in an Acta Horticulturae later this year. Further
details can be obtained on the ISHS web site at http://www.ishs.org/.
Errol W. Hewett Chair,
ISHS Postharvest Commission
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Postharvest
Heat Treatments: Effects on Commodity, Pathogens and Insect Pests
Immediately prior to
the ISHS Postharvest meeting in Jerusalem, a satellite meeting on Postharvest
Heat treatments was held at Maagan on the shores of the Sea of Galilee,
Israel, on 22-24 March 2000. This Workshop was hosted by BARD, (a cooperative
agricultural research programme between Israel and the USA) and organized
by Dr Susan Lurie, Volcani Center, Israel with the assistance of Dr Roy
McDonald, USDA, and Professor Robert Paull, University of Hawaii.
Attended by about 50
participants from 15 countries, this was an excellent example of a highly
specific meeting where all participants could interact professionally and
socially, with time on the programme for ample discussion of the papers
presented. Seventeen papers were presented ranging from reviews to reports
of ongoing research.
A highlight of the Workshop
was the mix of skills and expertise of participants. It is rare for truly
multidisciplinary meetings to be organized these days as scientists become
more and more specialized in their activities. But this Workshop was successful
because it provided an opportunity for plant pathologists, entomologists,
plant physiologists and biochemists, molecular biologists and engineers
to listen to research and experiences of colleagues in different disciplines.
The programme consisted
of 5 sessions. Professor Lutz Nover provided an elegant insight into the
molecular complexities of the heat response in plants indicating how such
primary events may be manifested as thermotolerance. This was followed
by sessions on heat treatments of fruits and vegetables with overviews
of the physiological, biochemical and cellular changes that occur following
exposure to temperatures in the range from 38 to 55oC. Knowledge of the
responses of plant pathogens and insects to heat is crucially important
if we are to be able to replace chemical treatments with some form of heat
application. A series of contributions outlined the varied responses that
can occur depending on the time/temperature interactions as well as the
importance of the host condition and the developmental stage of the organism.
It is all very well
for scientists and regulatory authorities in different countries to come
up with detailed recommendations for controlling pests and/or diseases
on different products; it can be a different and difficult challenge to
achieve such conditions on a commercial scale. Thus the experiences of
an engineering company in establishing hot water treatment systems for
treating mangoes in Central and South America were a salutary reminder
to the participants that increasing the complexity of treatment protocols
makes it increasingly difficult to achieve required quarantine conditions
in spite of sophisticated computer-controlled systems.
Several important messages emerged from
this Workshop. It is clear that in plants, pathogens and insects, a multiple
range of processes is involved in responses to heat, but there is no one
blanket response for all species. Production of heat shock proteins, while
important and still an active topic of research, is not the only response
occurring, and we must continue to explore other metabolic processes to
identify critical points that may be amenable to manipulation. A strong
case was made for re-examination of the role of membranes in heat responses;
it is felt that perhaps they are not the key as has been widely believed,
but the changes that occur may be a consequence of the stress or merely
a reflection of its role as a sensor of the stress received.
It must be remembered that heat treatments
can and will be used for different purposes including delay of senescence,
reduction of decay and mortality of insects. Each should be examined separately
as they will require different operating parameters for successful implementation.
Such treatments will affect multilayered processes and hence each must
be investigated both independently and then holistically. For example,
it was shown that insects become conditioned very rapidly to heat, although
this may be reduced by anoxia. Of particular interest was the development
of mathematical models, based on models derived from extensive data sets,
that have potential to be used to identify the most promising, efficient
and user friendly quarantine solutions for industry.
The session on the technology of heating
was particularly interesting. Scientists were reminded that their laboratory
results always had to be scaled up to a large scale before they could be
used commercially. Practical examples of some of the constraints and difficulties
in achieving this were graphically presented with a plea to researchers
to provide generic and relatively straightforward recommendations for treatments
wherever possible.
Apart from the valuable networking
that took place in this highly specialized but diverse meeting, 3 main
messages emerged: