I managed to find some time to work on this last night and this
morning, so I?m able to post your answer before I go.
I?ve done a thorough search of PubMed as well as an overall Google
search. I found a number of articles, reports, and research papers
which all seem to corroborate each other when it comes to optimum and
safe irradiation doses for prevention of Anthracnose in Mangoes.
First is a summary of the data I found in all the literature and
sources I?ve provided later in my answer. I?ve pulled the irradiation
doses from each article to make it easier for you to compare them.
Next is some background which describes the development of Anthracnose
in ripening mangoes and then are the sources and links to either the
abstracts or the articles containing the actual data.
Where the link takes you to an abstract, I?ve indicated whether or not
the full text of the article is available for purchase online. In most
cases it is.
In some cases I?ve provided bibliographies of literature cited in the
articles. In these cases, the article cited was not available online,
but you may be able to follow up via your library.
Before we start -- a quick note on units (which I understand you may
already be aware of) ?
The unit of absorbed dose is the gray (Gy) where 1 gray is equivalent
to 1 joule per kilogram
1 Gray (Gy) = 100 rads
1 Kgy = 1000 Gray
1 krad = 1000 rads
.25 kilograys = 25 kilorads
1 --- Colletotrichum gloeosporioides is the fungus that causes
2 --- The peel of an unripe mango contains antifungal chemicals that prevent
the growth of Colletotrichum gloeosporioides
3 --- Irradiation delays ripening of Mangos, thus preventing
4 --- Irradiation also sterilizes and controls insects
IRRADIATION DOSAGES CITED AS NECESSARY TO STERILIZE / CONTROL INSECTS.
300 Gy control mango seed weevil
150 Gy control 11 species of Tephritid fruitfly
IRRADIATION DOSAGES CITED AS NECESSARY TO DELAY RIPENING:
Low-dose UV irradiation protects against postharvest storage rots and
extends storage life, increasing resistance to fungal pathogens.
25 Krad extension in shelf life of 6 to 8 days at ambient temperature
25 Krad extension of storage life of about 10 days at ambient temperatures
30 Krad causes ripening delay of 7 days at room temperature
0.25 kGy to 1.5 kGy in order to accommodate mangoes of various
varieties and different types of irradiators
0.25 - 0.75 kGy for shelf life extension (reports examined encompass 12 varieties)
Low doses (up to 1 kGy) delay physiological processes (ripening, etc.)
Medium doses (1 to 10 kGy) extend the shelf life of commodities,
eliminate spoilage and pathogenic microorganisms, and improve the
technical properties of food.
3 minute exposure to infrared found to be as effective as the
commercially used five minute hot water treatment in controlling
COMBINATION OF IRRADIATION AND OTHER TREATMENTS CITED
Hot water: 550 C for 5 minutes followed by 30 Gy
TBZ, Benlate, Antracal and hot water dip alone and in combination with
gamma irradiation (300Gy)
Irradiation followed by hot benomyl treatment controls anthracnose
IRRADIATION LEVELS THAT CAUSE DAMAGE
In excess of 600 Gy caused lenticel spotting, surface discolouration
Physical defects seem to be minimal up to a total overall average
absorbed dose of 0.60 kGy (maximum of approximately 1.0 kGy, assuming
a dose uniformity ratio of 1.2).?
Wholesomeness not affected by gamma-irradiation at a dose of 75 krd
30 Gy ? no radiation injury
For mangoes - 650 Gray necessary to ensure a minimum dose of 300 gray throughout
?FAO estimated that over 23 million metric tons (MT) of mangos were
produced in 1998,about half of which were grown in India. Mexico,
however, is the world?s
largest exporter of fresh fruit; it shipped about 187,000 MT in 1997
??Mexican mangos have little or no anthracnose since they are produced
on the arid Pacific coast of that country. Thus, they are often
esthetically superior to Florida mangos.These factors, coupled with
low production costs in Mexico, have severely crippled the Florida
?..Anthracnose is caused by, Colletotrichum gloeosporoides
?..Infection may then proceed with the formation of infection pegs
from the base of the appressoria ? this usually occurs, however, only
after fruits have begun to ripen.
?...the reason that these infections remain quiescent is not known,
but may be related to antifungal compounds that are found in the peel
of mango fruits?
Anthracnose: The Most Important Disease in Much of the Mango-producing World
Anthracnose. Caused by Colletotrichum gloesporioides, begins as latent
Disorders infections in unripe fruit and develops when the mangoes
begin to ripen. Lesions may remain limited to the skin or may invade
and darken the flesh.
UC DAVIS - POST HARVEST ? PRODUCE FACTS - MANGO
Antifungal Compounds and Fruit Ripening
?..The resistance of unripe fruits to fungal decay has been associated
with the presence of preformed antifungal compounds in the peel.
Pathogens often infect unripe fruits but then remain quiescent, with
the onset of decay coinciding with decreases in the concentrations of
antifungal compounds to subtoxic levels as the fruit ripens. Thus,
quiescence may represent a mechanism for avoiding toxic levels of
antifungal plant compounds. This area has been studied in particular
detail for interactions involving Colletotrichum gloeosporioides and
the subtropical fruits mango and avocado.
?..The peel of unripe mango fruit contains a mixture of the antifungal
5-alkylated resorcinols 5-12-cis-heptadecenyl resorcinol and
5-pentadecyl resorcinol (51), while avocado peel contains antifungal
monoenes and dienes (1-acetoxy-2,4-dihydroxy- n-heptadeca-16-ene and
1-acetoxy-2-hydroxy-4-oxo-heneicosa- 12,15-diene) (167, 168) (Fig. 7).
?..The levels of these compounds decrease during fruit ripening, and
this decrease occurs more rapidly in disease-susceptible cultivars,
suggesting that the presence of inhibitory levels of these antifungal
substances in the peel of unripe fruit may arrest fungal growth and
LIT CITED ABOVE
Droby, S., D. Prusky, G. Jacoby, and A. Goldman. 1986. Presence of
antifungal compounds in the peel of mango fruits and their relation to
latent infections of Alternaria alternata. Physiol. Mol. Plant Pathol.
Fungal Resistance to Plant Antibiotics as a Mechanism of Pathogenesis
John p. Morrissey and Anne e. Osbourn*
MICROBIOLOGY AND MOLECULAR BIOLOGY REVIEWS,
Sept. 1999, p. 708?724 Vol. 63, No. 3
ANTHRACNOSE ? IRRADIATION ? MANGOES - RESEARCH
[abstract ? article available for online purchase]
?Three minute exposure to IR was found to be as effective as the
commercially used five minute hot water treatment in controlling
anthracnose (Colletotrichum gloeosporioides) and soft brown rot
(Nattrassia mangiferae) on seven mango cultivars??
SHORT WAVE INFRA-RED RADIATION AS AN ALTERNATIVE TO THE HOT WATER BATH
TO CONTROL POSTHARVEST DECAY IN MANGOES
?Extensive studies have been conducted to determine the effect of
r-radiation on the shelf life extension of mango.
The optimum radiation dose for Alphonso mango is 25 K rad, giving an
extension in shelf life of 6 to 8 days at ambient temperature.
A combination of hot water treatment (550 C for 5 minutes) followed by
30 Gy irradiation was found to be the best treatment in terms of shelf
life extension and quality of mangoes.
After this treatment, mangoes had a storage life of 38 days (at 150
C), 28% rotting and no irradiation injury.
It was observed that 300 Gy control mango seed weevil while 150 Gy was
shown to control 11 species of Tephritid fruitfly and 75 Gy prevents
the adults emerging from the fruits but more work is needed.
Doses of irradiation in excess of 600 Gy caused lenticel spotting,
surface discolouration and retardation of ripening of Kensington Pride
mangoes, but irradiation at this level contributed to only minor
improvements in disease control.
However, irradiation followed immediately by hot benomyl treatment
controlled anthracnose and stem-end rot during storage at 200 C for 15
MANGO - Post Harvest Technology
?It may be concluded that the wholesomeness of mangoes was not
affected by gamma-irradiation at a dose of 75 krd.?
The effects of low-dose gamma-irradiation on the wholesomeness of
mangoes (Mangifera indica) as determined by short-term feeding studies
Br J Nutr. 1976 Jan;35(1):67-75.
Gamma irradiation (30 Krad) causes ripening delay of 7 days in mangoes
stored at room temperature. The irradiated fruits ripen normally and
show no adverse effect on quality. Irradiation has not yet been
approved for this purpose.
FAO REPORT - CHAPTER XX MANGO: Post-harvest Operations
Pakistani Research on Use of Antifungal Treatments:
TBZ, Benlate, Antracal and hot water dip alone and in combination with
gamma irradiation (300Gy) were used to control the post harvest
problem of anthracnose and stem end rot in mangoes. However hot water
dip (55oC)highly significant to control this disease.
POST HARVEST HANDLING
Low-dose UV irradiation protects sweet pepper (1), mango (4), carrot
(43) and citrus fruits (49) against postharvest storage rots and
extends their storage life, increasing resistance to fungal pathogens.
However, it is necessary to study certain aspects of on-line
application of UV-C during fruit processing, including Phytoparasitica
26:1, 1998 61 factors such as fruit ripening and storage temperature
Reference cited for above
Boulet, M., Arul, J., Verret, P. and Kane, O. (1989) Induced
resistance of stored mango (Mangifera indica L.) fruits to mold
infection by treatment with Colletotrichum gloeosporioides L. cell
wall hydrolysate. Can. Inst. Food Sci. Technol. J. 22:161-168.
The Postharvest Phase: Emerging Technologies for the Control of Fungal Diseases
M. Mari and M. Guizzardi (1998) Phytoparasitica 26(1):59-66
[Abstract. Full text available for online purchase]
?Initial studies were carried out to ascertain the optimum radiation
dose required to delay ripening in the mango fruit.
Mature olive green Alphonso mangoes were irradiated in the
preclimacteric stage by 12, 25, 50, 75, 100 and 200 Krad. Optimum
radiation dose, as determined by maximum delaying effect and minimum
damage, was found to be 25 Krad and resulted in extension of storage
life of about 10 days at ambient temperatures (25?32°C).?
Dharkar, S.D. and Sreenivasan, A. 1972. IRRADIATION AS A METHOD FOR
IMPROVED STORAGE AND TRANSPORTATION OF MANGOES. Acta Hort. (ISHS)
All of the below from:
HEALTH CANADA - IRRADIATION OF MANGOES:
[page 1] http://www.hc-sc.gc.ca/food-aliment/fpi-ipa/e_mango_irradiate01.html
?The specific purpose of irradiation in the first submission is
disinfestation, specifically, to control fruit flies?..
[Page 2] http://www.hc-sc.gc.ca/food-aliment/fpi-ipa/e_mango_irradiate02.html
? The second submission is based on a request to be allowed "to extend
the shelf life of mangoes permitting the import and marketing of good
quality mangoes from tropical countries for the enjoyment of Canadian
consumers." The source of irradiation is Cobalt-60. The dose range
requested is 0.25 kGy to 1.5 kGy in order to accommodate mangoes of
various varieties and different types of irradiators (i.e. having
different dose uniformity ratios).
[page 4] http://www.hc-sc.gc.ca/food-aliment/fpi-ipa/e_mango_irradiate04.html
?With regard to physical alterations [of mangoes], the main one noted
is that higher doses than those required to delay ripening (i.e.
extend shelf-life) can result in scalding (surface browning or brown
spots) of the mango peel (skin). Optimal doses are variety-dependent
and, from Table 2 of the consultant?s review, seem to vary from 0.25 -
0.75 kGy for shelf life extension (reports examined encompass 12
varieties). Based on work undertaken on Haden, Keitt and Tommy Atkins
varieties, physical defects seem to be minimal up to a total overall
average absorbed dose of 0.60 kGy (maximum of approximately 1.0 kGy,
assuming a dose uniformity ratio of 1.2).?
?The effects of irradiation depend on the dose absorbed. Low doses (up
to 1 kGy) inhibit sprouting in tuber, bulb and root vegetables,
inhibit the growth of asparagus and mushrooms, and delay physiological
processes (ripening, etc.) in such fruits as banana, mango, and
papaya. Medium doses (1 to 10 kGy) extend the shelf life of
commodities, eliminate spoilage and pathogenic microorganisms, and
improve the technical properties of food. Lastly, high doses (10 to 50
kGy) can be used for industrial sterilization and decontamination of
certain additives or ingredients (Morrison 1992, ICGFI 1994, OTA 1985,
??Factors influencing the response of fresh fruits and vegetables to
irradiation include the type of commodity and cultivar, production
area and season, maturity at harvest, initial quality, and post
harvest handling procedures. Similarly, environmental conditions
during irradiation (temperature and atmospheric composition), and dose
rates are also influencing factors (ICGFI 1994, Kader 1986, OTA 1985,
Morrison 1992). The relative tolerances of fresh fruits and vegetables
to irradiation doses below 1 kGy are listed in Table 1 below.?
[mango not listed in Table 1]
US EPA: The Use of Irradiation for Post-Harvest and Quarantine Commodity Control*
*Many offline references in that article.
The Use of Irradiation for Post-Harvest and Quarantine Commodity Control
[page 2] ?..Studies have found that irradiation can have a number of
negative effects on this [Kensington Pride] type of mango. Firstly at
overall doses as low as 100 gray the ripening process in the fruit is
halted. (The Australian mango is normally picked when it is still firm
and green in order to prevent the fruit being over-ripe when it
reaches markets). The irradiation process also results in effects on
the skin colouration of the fruit. Uneven colour spotting results and
pores on the surface of the fruit turn black, in addition the skin is
bronzed resulting in a mottled browning effect??
[page 3] ?..The question of Dose Uniformity is particularly relevant
when dealing with fruits with hard kernels such as mangoes. A study
found that for mangoes a dose of 650 Gray was necessary to ensure a
minimum dose of 300 gray throughout.
??Besides the radiation source (E-Beams, Gamma Rays, X-Rays) there are
three important factors which affect the effectiveness of the
irradiation process. The distance of the food from the irradiation
source, the bulkiness of the food and its heterogenicity. It is of
concern that there is no detailed information in this application
regarding proposed procedure for irradiating these fruits. Important
points on which information is totally lacking are:
1. The distance of the fruits from the radiation source
2. Whether there will be a single radiation source or multiple
3. Whether there will be a single pass over the radiation source or multiple
4. If there is a single radiation source will the fruit be rotated or turned
over to ensure even dosage on all surfaces, including the ends
5. How will the fruit be packed when it is irradiated - is it loose, in trays
or in cases??
a. Rose, R.C. (1987), Ann.N.Y. Acad. Sci. 498, pp506-508
b. Murray, David.R, ?Biology of Food Irradiation? Taunton, Somerset, England.
Research Studies Press. 1990
c. Mathur, P.B., Lewis, N.F. ?Storage Behaviour of Gamma Irradiated Mangoes?
Int. J. Appl.Radiat. Isot. ; IJARA; (1961); v.11. pp 43-45.
IRRADIATION OF TROPICAL FRUITS - BREADFRUIT, CARAMBOLA, CUSTARD APPLE,
LITCHI, LONGAN, MANGO, MANGOSTEEN, PAPAYA, AND RAMBUTAN.
LITERATURE CITED IN OTHER ARTICLES
These looked promising, but are not available online.
SPALDING, DH & Reeder, W.f. 1986 Decay and acceptability of mangos
treated with combinations of hot water, imazil and gamma irradiation.
Plant Disease 70: 1149-1151
Upadhyay, IP, Noomhorm, A. & Ilangatile, S. 1994. Effects of gamma
irradiation and hot water treatment on the shelf life and quality of
Thai Mango cv. Rad. Pages 348-351 in: Postharvest handling of Tropical
fruits. Champ, BR. Highly, E. & Johnson, GI. (Eds) Proceedings of an
international conference held at Chiang Mai, Thailand.
COMPARATIVE STUDY OF COLLETOTRICHUM GLOEOSPORIOIDES FROM AVOCADO AND MANGO
So, that should give you everything you need. If anything I?ve said
isn?t clear, please feel free to ask for clarification. As I
mentioned, I will be away for the weekend, but will respond when I
return next week.
Thanks so much for your question ?
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