Most of the research on scald prior to 1945 was reviewed by Smock and 
Southwick (112). 1/ More recent reviews of the factors affecting scald and 
scald control research were published by Pentzer and Heinze (76) in 1954, 
Marcellin and Leblond (49) in 1957, Fidler (16) in 1959, Ginsburg (23), Martin 
and Lewis (52), and Smock (109) in 1961. 
The cause of scald is still unknown although many possibilities have 
been investigated. The usual theory is that some volatile substances produced 
by the fruit accumulate in the skin and directly or indirectly are responsible 
for the death of susceptible tissue. However,*the volatile theory is becoming 
increasingly controversial, and whether volatile substances are ares in- 
volved in scald is still duikaoen (6, 14, 17, 26, 42, 43, 44, 75, 7» LED 
Bain (1) found that scald symptoms were due to eraeaen of eee sca Epi- 
dermal cells were not affected unless scald was very severe. 
Later Bain and Mercer (2) examined Granny Smith apples by electron 
microscopy. The first symptom of scald detected was the formation of an addi- 
tional electron-dense material in close association with a normal constituent 
of the vacuoles of hypodermal cells. The additional material accumulated on 
the tonoplast as scald became more severe, and the protoplasts became disorgan- 
ized, tan and increasingly electron dense. Following this the cells collapsed 
radially, forming the dark brown sunken lesion associated with severe scald, 
Shutak and others (100) found that scald did not develop on areas of 
fruit surface that had part of the cutin removed. The cuticle may act as a 
barrier to the escape of substances responsible for scald. Siegelman and 
Schomer (101) and Metlitskii and Tsekhomskaya (59) reported that scalded apple 
skin had a lower rate of respiration than nonscalded skin, probably due to cell 
destruction in scalded tissue. Patterson (/5) showed that the scald reaction 
was enzymatic. 
In 1958, Metlitskii and Tsekhomskaya (59) proposed that scald should be 
regarded as a disturbance of metabolic equilibrium with a deviation of respir- 
ation towards anaerobiosis. This resulted in alcohol and acetaldehyde accumu- 
lation in tissues. They found that during storage there is a noticeable de- 
crease in the air permeability of apple skin. Also, in apples affected by 
scald, skin permeability is much lower than in healthy apple skin. 
Dilley et al. (13) proposed that apple scald is composed of two physio- 
logically distinct phases; one of anaerobic induction and one of aerobic de- 
velopment. Brief nitrogen treatments of 36 to 108 hours at 20° C. (68° F.) were 
used to induce scald on Rome and McIntosh apples. It is not known if scald 
could be anaerobically induced immediately after harvest because the fruit used 
in this test had been stored 3 months before nitrogen was administered. 
Role of Volatiles 
Apples give off various volatile materials some of which may be respon- 
sible for scald development. Meigh (56) found that acetone and acetaldehyde 
were two of the most abundant volatiles produced by apples. He found no cor- 
relation between high carbonyl evolution and heavy incidence of scald. 
Griffiths and Potter (26) stated that a high concentration of volatile sub- 
stances in the storage atmosphere coincides with a marked increase in scald. 
1/ Underscored numbers in parentheses refer to Literature Cited, p. 204. 
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