Pm. Chen et al., RIPENING BEHAVIOR AND COMBINED FUNGICIDE AND PRESTORAGE HEAT-EFFECTS ON DECAY CONTROL OF BOSC PEARS IN AIR OR STEP-WISE LOW-OXYGEN STORAGE, Postharvest biology and technology, 6(3-4), 1995, pp. 235-248
'Bosc' pears (Pyrus communis, L.) harvested at commercial maturity wit
h flesh firmness (FF) of 75 Newton (N) from the southern district of O
regon were stored in either air or step-wise low O-2 at -1 degrees C d
uring the 1992-'93 and 1993-'94 seasons. The levels of O-2 in the step
-wise low O-2 Storage were maintained and increased from 0.5% for four
months to 1.0% for two months, and finally to 1.5% for two months whi
le the CO2 concentration in the storage was kept below 0.05%. Air-stor
ed fruit were capable of ripening normally with good dessert quality a
fter one, two, and three months of storage. These fruit softened to be
tween 9.7 N and 15.0 N and reached the ethylene climacteric peak on da
y 7 or 8 of ripening at 20 degrees C. The ripened fruit developed a bu
ttery and juicy texture as indicated by an apparent reduction of extra
ctable juice (EJ) from 67 ml juice per 100 g fresh weight (FW) of unri
pened pulp tissue to less than 45.0 mi juice per 100 g FW of ripened p
ulp tissue. Fruit in air storage for four and five months reached the
ethylene climacteric peak on day 4 of ripening but did not soften prop
erly. Fruit stored in step-wise low O-2 for six, seven and eight month
s reached the ethylene climacteric peak on day 6 of ripening. Step-wis
e low-O-2-stored fruit softened properly to 12 N or lower and reduced
EJ to 49 ml 100 g(-1) FW (six and seven months of storage) or 59 ml 10
0 g(-1) FW (eight months of storage) on day 8 of ripening. Based on th
e analyses of ethylene production, fruit softening and reduction of EJ
during ripening, fruit stored in the step-wise low O-2 Storage for si
x, seven and eight months maintained a physiological state similar to
the fruit stored in air for one to three months. The combination of pr
estorage heat (28 degrees C for one day) and step-wise low oxygen stor
age effectively reduced side rot by 60 and 63% in 1993 and 1994, respe
ctively. Even greater decay control was obtained with the fungicides i
mazalil and Exp10412A on inoculated fruit, and thiabendazole plus capt
an on non-inoculated fruit.