Mechanical and Temperature Effects on Shelf Life Stability of Fruits and Vegetables - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 57

TABLE 2.6
Recommended Temperature and Relative Humidity
for Curing Roots and Tubers

Crop Temperature, °CRelative Humidity, %Time, a days

Irish potato 13-17 Above 85 7-15

Sweet potato 27-33 Above 90 5-7

Yam b 32-40 Above 90 1-4

Taro (dasheen) 30-35 Above 95 4-7

Cassava 30-35 Above 80 4-7

a

In practice, at least 7 days should be allowed for curing.

b

Dioscoreaalata and D.rotundota .

Data from Prevention of Post-Harvest Food Losses: Fruits, Vegetables and Root
Crops, A Training Manual, FAO Training Series No. 17/2, Food and Agriculture
Organization of the United Nations, Rome, Italy, 1989.

and this occurred at maximum rates within 5 days. They inferred that this combi-
nation of lignified tissues and wound periderm formed after a 5-day curing period
was an effective barrier against the entry of pathogens. Storage stability of sweet
potatoes, however, may not only rely on whether wound healing has occurred, but
rather it is an interaction of several other factors. Table 2.6 shows the recommended
conditions for curing of different root crops and tubers.

W ARMINGTOTHE D ESIRED T EMPERATURE B EFORE H ANDLING

Wouters and co-workers 86 suggested warming the tubers to above 10°C before
handling, as an effective way of reducing the susceptibility of the potatoes to bruise
damage, especially when the dry matter content of the tubers is low. They correlated
bruise susceptibility to the rupture force obtained from a puncturing test.

P RE-AND P OSTHARVEST C HEMICAL T REATMENT

Preharvest sprays to control infection caused by mechanical injury are generally not
encouraged because only a small portion of the fungicide is bound to the harvested
product, and this may be removed during washing. Nevertheless, Rippon 52 believed
that this may be a desirable approach to the problem of the high incidence of
superficial injuries and attendant decay from mechanical harvesting. Chemical treat-
ment to control infections should be applied soon after harvest to avert the penetration
of pathogens into the host tissue. According to Eckert, 87 the maximum period
between harvest and successful treatment varies: 10 h for peaches inoculated with
Rhizopus spp. and held at 25°C, and 24 h for oranges inoculated with green mold
( Penniciliumdigitatum ) and held at 24°C. The maximum time to control Phoma