Bagster, L.S.

Connah, Madoline V.

University of Queensland eSpace

University of Qyeensland 
PAPERS 
DEPARTMENT OF CHEMISTRY 
Volume 1 1939 Number 10 
Artificial Ripening of Oranges 
BY 
L. S BAGSTER, D.Sc., and MADOLINE V. CONNAH, M.Sc. 
REPRINtED 
from 
tHE PROCEEDINGS OF THE ROYAL SOCIETY OF QUEENSLAND 
VOL. L, No. 14, pp. 153-160. 
6th JUNE, 1939 
VoLUME l. 
DEPARTMENT o:F' CHEJHIS'l'RY. 
1939. NUMBER 10. 
ARrriHIOIAL RIPlBNING OB, OH.ANGl£8. 
By 
L. S. BAGSTBR, D.Sc., 
and 
l\IADOLINE V. CONNAH, M.Sc. 
Departml'nt of Chem·istry, University of Queensland. 
[Reprinted from the Proceedings of tlw Rayed Society of Queensland. 
Vol. h, No. 14, pp. 153-160.] 
VoL. L., No. 14. 153 
Artificial Ripening of 0Tanges. 
BY I1. S. BAGSTER., D.Sc., A.A.C.I., and J\IADOioiNE V. CONNAH, M.Sc. 
Department of Chemistry, University of Queensland. 
[Read before the Royal Society of Queensland, 28th November, 1938.] 
A R'riFICIAL ripening of fruits by means of treatment with ethylene
gas is a well-known commercial process, and in recent years has been 
the subject of considerable investigation. 
It has been shown that with fruit such as the banana, apple, pine­
apple, ethylene treatment causes actual ripening of the pulp as well as 
hastening the colouring of the skin. It has been suggested by Lynch 
(1935) that ethylene acts as a coenzyme to an oxidase system such as is 
known to be present in both the skin and pulp of such fruits. This 
suggestion is supported by the fact that the skin of citrus fruits, such 
as the orange. and lemon, which are known to contain an oxidase system 
is affected by the process, whereas the pulp which contains no oxidase 
system is not affected. 
Egana and Acerati (1935) investigated very thoroughly this process 
with regard to oranges of various types. They found that the orange 
may acquire colour by this process, but it is necessary for it to have 
begun its natural change of colour. It is impossible by this method to 
colour a completely green orange, whereas the banana can be coloured 
by ethylene at any stage of maturity. With regard to the actual pulp, 
no change due to ethylene treatment \Vas observed in the citric acid, 
glucose, or invert sugar content. 
It was therefore thought of interest to study the effect of ethylene 
on the enzyme catalase which is present in the orange pulp, and also 
its effect on the ascorbic acid content of oranges. The investigation 
covered the fruit from one particular tree throughout the season. The 
tree was a well-grown 10-year-old plant about 6 ft. high and of approxi­
mately 6 ft. spread. It was grown in an open position in brown loam 
soil. 
The ethylene treatment used was that of Egana, namely-tempera­
ture 18-20° C., humidity 75-80°, concentration of ethylene 2 in 1000. 
T'he ripening cupboard was swept out every eight hours with fresh air 
and then recharged with ethylene. The treatment requires about four 
da.ys. 
The catalase was estimated as oxygen liberated in one hour by 
1 c.c. of 30% hydrogen peroxide in 3 c.c. water added to 10 c.c. juice
mixed with approximately 3 grs. calcium carbonate in 40 c.c. of M/5 
potassium hydrogen phosphate-M/5 sodium hydroxide buffer which 
gave pH 7. A vessel containing a strong solution of sodium hydroxide 
' was used to absorb the carbon dioxide liberated, and it was ascertained 
that all this had been absorbed before the peroxide was added. 
For estimation of ascorbic acid 5 c.c. of a solution of 2·6 dichlorindo­
phenol and 0·5 c.c. glacial acetic acid were titrated against the orange 
juice. The dye solution was standardised by means of freshly prepared 
ascorbic acid solution which was itself standardised by titration against 
0·01 N iodine. 
The fruit was cut with a stainless knife, squeezed on glass, filtered 
through a porcelain sieve, and used immediately. 
Experiments showed that grinding the juice with fine silver sand 
reduced the catalase but had no appreciable effect on the ascorbic acid 
content. 
The results are shown in the accompanying tables. 
154 PROCEEDINGS OF 'l'HE ROYAL SOCIETY OF QlJEENSI,AND. 
No. of Orange. 
----�-----·---
Batch I (29-3-38)-
At 
A• 
A a 
Bt 
B • B; 
cl 
c. 
c. 
. .  
. .  
.. . 
. . 
. . 
.
. 
. .  
. .
 
, ,  
. 
. 
. . 
. 
. 
. 
. 
. 
. 
. 
. 
. 
. 
. 
. 
. .  
Batch 2 (4-4-38)-
Bt 
B• 
Ba 
cl 
c. 
c. 
. .  
. . 
. . 
. .
 
. . 
.
. 
. . 
. . 
.
. 
. . 
. 
. 
. . 
Batch 3 (ll-4-38)-
Bt . .  
B. . .  
cl . .  
c. . .  
. 
. 
. . 
. . 
. . 
Batch 4 (I8-4-38)--· 
Bt 
Bz 
Ba 
cl 
c. 
c: • 
. .  
.
. 
. .  
. .  
.
.
 
. .  
. . 
. . 
. . 
. 
. 
. . 
. . 
Batch 5 (26-4-38)-
At 
Bt 
B• 
cl 
c. 
. .  
. . 
. .  
.
. 
. .  
. .
. .
. . 
. . 
. . 
Batch 6 (29-4-38)-· 
Bt 
B. 
cl 
c. 
c. 
. .  
. .  
. .  
. .  
. .  
. . 
. . 
. . 
. 
. 
. . 
. . 
. . 
. . 
' 
. 
. . 
. . 
. 
. 
. 
. 
. . 
. 
. 
. . 
. 
. 
. .  
. 
. 
. . 
. 
. 
. . 
. . 
. 
. 
. . 
. . 
. . 
. 
. 
. . 
. 
. 
. 
. 
. . 
. 
. 
. . 
. . 
. 
. 
. . 
. . 
. 
. 
. 
. 
. . 
. . 
. . 
. . 
. . 
. 
. 
. 
. 
. 
. 
. . 
. 
. 
. . 
. 
. 
. . 
. . 
. . 
. . 
. . 
. 
. 
. . 
. 
. 
. . 
. 
. 
. . 
. . 
. . 
. . 
. 
. 
. . 
. 
. 
. 
. 
. . 
. 
. 
. . 
. . 
. 
. 
Ca talasc (as 02 Ascoruic Acid 
Colour. Tnstc. at N.T.P. from (mgr. in 10 c.c. 
10 c.c. juice.) juice.) 
I 1 I·5 5·65 
I 2 8·I n·7l 
I 2 3·3 6·48 
III 2 0·0 5·68 
II 2 2·0 6·58 
II 2 0·9 5·8I 
III I IO·I 6·25 
IV 3 6·7 6·58 
IV 4 3·4 5·95 
II 4 4·4 5·22 
II 3 4·6 5·63 
II 3 0·0 5·83 
IV 4 8·4 6·50 
IV 3 5·8 5·96 
IV 3 0·2 5·83 
II 3 2·7 6·54 
II 3 I·5 7·52 
IV 4 2·4 6·24 
IV 4 0·5 5·55 
II 4 3·5 6·05 
III 3 5·0 6·4I 
III 3 5·1 6·05 
III 4 20·6 5·42 
v 3 6·4 5·78 
III 3 3·7 5·84 
I 3 I·6 5·I8 
II 2 8·4 4·87 
II 2 6·0 5·40 
IV 3 5·8 6·17 
IV 3 4·8 6·45 
III 4 12·4 5·51 
II 4 4·6 5·04 
IV 4 7·2 5·3I 
IV 4 8·3 4·99 
IV 4 13·2 5·61 
ARTIFICIAL RIPENING OF ORANGES. 155 
Catalase (ns 02 Ascorbic Acid 
No. of Orange. Colour. 'l'nstc. at N.T.P. from (mgr. in 10 c.c. 10 c.c. juice.) juice.) 
Batch 7 (5-5-38)-
A1 I 1·9 5·56 
Az I 0·0 5·56 
B1 III 4 6·7 5·32 
B. II 3 15·7 4·63 
lJ 1 . .  IV 3 6·!) 5·14 *Cz IV 3 14·2 4·73 
Batch 8 (12-5-38)--
Al I 0·0 5·0!) 
Az II 0·4 5·0!) 
B1 III 4 13·7 5·67 
n. III 4 10·!J 4·84 
c1 IV 4 11·5 5·22 
c. v 4 6·0 5·28 
Batch 9 (16-5-38)-
B1 III 4 7·8 5·57 
B• III 3 0·0 5·44 
cl III 4 11·4 5·13 
c. IV 3 3-4 5·44 
c. III 4 1·1 5·78 
Batch IO (I9-5-38)-
A1 I I O·!J 5·7I 
A• I I 0·0 4·87 
B1 IV 7·6 5·34 
B� III 4 9·22 4·83 
*C1 v 4 I 4·2 5·20 
c. v 4 4·!J 5·93 
Batch I2 (30-5-38)-
B1 III 4 7·4 5·3I 
B• III 3 0·0 6·08 
*Cl v 4 9·6 5·02 *Cz v 3 11·4 5·63 
Batch 13 (6-6-38)-
Bl III 4 24·I 5·23 
n. III 3 3·6 5·71 
cl IV 3 6·05 4·94 
c. v 3 I3·5 5·71 
156 PROCEEDINGS OF THE ROYAL SOCIETY OF QUEENSLAND. 
No. of Orange. Colour. Taste. 
Catalase (as 021 Ascorbic Acid 
at N.T.P. from (mgr. in 10 c.c. 
------
10 c. c .. juice.) 
I
juice.) 
Batch 14 (17-6-38)-
B, III 1·5 5·32 
c, v 5 24·7 5·66 
c. v 5 4·7 4·77 
Batch 15 (29-6-38)-
v Judged not completely ripe. 
Batch 16 (6-7-38)-
D, v 5 10·5 4·57 
Batch 17 (17-7-38)-
D, v 5 2·1 4·75 
Batch 18 (25-7-38)-
D, v 6 6·8 5·90 
D• v 6 1·7 6·81 
Batch 19 (8-8-38)-
D, v 6 5·0 f)·20 
D• v 6 O·D !)·42 
Batch 20 (17-8-38)-
D, v 6 5-4 7·70 
D• v 6 8·4 7·38 
Batch 21 (20-8-38)-
D, v 6 3·7 8·02 
D• v 6 2·2 6·76 
Batch 22 (5-9-38)-
D, v 6 3·2 6·52 
D. v 6 1·7 7·64 
Batch 23 (11-9-38)-
D, v 4 5·9 5·D2 
D• v 6 6·6 6·13 
EXPLANATION OF SYMBOLS USED IN TABLE. 
A, green oranges tested the same day as picked; B, partly ripened when picked, 
untreated, but kept for test with group 0; 0, partly coloured when picked, 
treated with ethylene; D, ripened on the tree, tested the same day as picked. 
Colour: I, green; ll, yellowish-green; III, greenish yellow; IV, pale yellow; 
V, orange. Taste: 1, very sour, extremely unpleasant to taste and completely 
inedible; 2, sour, edible but definitely unpleasant; 3, fairly sour, juice palatable 
with sugar; 4, slightly sour, quite edible but faint sourness underlying the sweetish 
taste; 5, sweetish, no trace of sourness but not yet fully ripened, poor flavour; 
6, sweet to definitely ripe and fully flavoured. 
Samples C for treatment with ethylene in each experiment were selected to 
conespond closely in size and colour with corresponding check samples B. Tbe colour 
given to these in the tables is that after ethylene treatment. 
ARTIFICIAL RIPENING OF ORANGES. 157 
Although the results are rather irregular, certain conclusions seem 
fairly de:finite-
1. The catalase content of completely green oranges was very
low and showed an increase as the fruit ripened until the 
oranges became really ripe, when it was decreased again, but 
did not become as low as in the completely green oranges. 
2. The ethylene treatment had apparently no effect on the catalase
content. 
3. The ascorbic acid content varied but little throughout the
season, but showed a slight tendency to increase as the 
oranges became really ripe. 
4. The ethylene treatment produced no definite change in ascorbic
acid content. Oranges marked thus* had a slight but definite 
unpleasant "musty" flavour after treatment with ethylene. 
Apart from this the treatment seemed to have no effect on 
the taste. 
This work was carried out by aid of a grant from funds provided 
to the University of Queensland by the Commonwealth Government 
through the Council for Scientific and Industrial Research. 
The authors are indebted to Miss N. McGinn, who carried out some 
of the later experimental work. 
REFERENCES. 
EGAN A, M:.K. and AcERATI, A., B'ol. del. Inst. de Invest. Agrov. 1935, vol. I, 
p 4.9 
LYNCH, L .. J., Proc. Roy. Soc. Qland. 1935, Vol. XLVII, P. 18. 


Artificial ripening of oranges

http://espace.library.uq.edu.au/view/UQ:363309/Artificial_Ripening_Oranges_v1no10.pdf

Artificial ripening of oranges

Abstract

Similar works

Full text

Available Versions

University of Queensland eSpace