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Thesis

THE SHRINKAGE OF POTATOES IN STORAGE.
Submitted by

Arthur Alexis Shillander.,
eomemeernerers <®

To the Horticultural Department,
Michigan Agricultural College,
June, 1915.
 

THESIG
Table of Contents.

Introduction

Resume of Literature
Description of Txperiment
Results

Conclusions

1035005

le
THE SHRIW<AGE OF POTATOES IN STORAGE,
Introduction,

It is a well known fact that potatoes lose weight
when kept in storaze. As several investigators have dis-
covered, this loss is due to evaporation of water and to
changes caused by the process of respiration in the ore
ganic matter. Considerable amounts of votatoes are kept
over winter by the pvnotato growers for the purpose of sgell-
ing them in the spring when the price is usually higher.
Therefore, if cheap and convenient nethods of storing the
tubers can be discovered, that will lessen the amount of
shrinkage, these will ve the means of saving money to the
grower. Even determining how much the loss in weight will
be, will undoubtedly be of value to the grower in helping
him to decide whether it will pay to keep the potatoes
over winter or not. Briefly stated, the primary purpose
of this experiment is to solve such proolems as the ones
mentioned.

A few experiments on this subject have teen carried
on by men in different parts of this country and in other
countries. <A brief survey of what these investigators have
found would not be out of nlace at this time,

Resume of Literature,

One of the first investigators was Nobve. He studied
the chanzes in weight and in chemical composition 3s ine
fluenced by temverature, moisture, light, etc. His cone

* Tandw. Vers. Stat., 7(1865) 452 -461., obs. in E.S.R.V.

3p. 494,
wa Dan

clusions were: that the controlling factors in determine-
ing the loss in weight by keeping were first of all heat
(temperature) and next in innortance was moisture in the
air. Heat increased the losses and noisture lessened them,
Light had no perceptible effect on the loss in weight. The
proportions of water and carbonic acid given off were four
times as much of the former as of the latter. This exe
periment was carried on under artificial conditions and
with a small number of tubers.

Muller and Thurgeau™ found that three distinct chenges
taxe place in the tubers, namely, respiration, sugar for-
mation and retrogrades starch formation,

E. Wollny** conducted an exneriment on a larzer scale.
He took twelve different varieties and selected 100 tubers
from each, early in Cetobcr. These were placed in lead
cylinders in a moderately dark, deep, day cellar, where
the temperature varied from 69 to 119 C, The tubers were
weizhed the first and fifteenth of each month, oeginning
in October and continuing to April lst. After that time
tne weight was taken the first of each month. "Under the
conditions of the experiment the greatest losses in weight
were directly after digging and decreased from then till
the first of Marcn, when they commenced to increase,” The

average percentage of losses of the twelve varieties ‘vere

 

* Eot. Centralbl., 19(1°82) No. 2; Oos. in ES. R.V. IV.
Page 494,
*# Wollny, F. Studies of the “hanges in Potato “ucers in

Keeping. Forsch, auf. 4d. Seh. 1. Agr. VThysik 14,

wml) 7 ~ ArT ~: 2 os ~— os ~ 6 UTP? “ 7" ANE
as follows for each month: Oct. 202%, Nov. 1, 18%, Dec.
50%, Jan. 50%, Feo. 81%, Mar. 41%, Anril 50%. Wollny
stated that 0° = 10°C, (329-,509°F) is the most rational
temperature for keeping notatoes since within these
limits the resniartion is low. Losses of organic matter
increase in proportion to the growth of srrouts. When
they start, the loss in weight is rapid.

C. O. Appleman*® after carryinz on experiments at the
Maryland Exveriment Station, states that cotatoes lose
weight due to evaporated water and respired carbon di-
oxide, Pry corditions favor evaporation. The loss of
COs is higher at high temperatures. The greatest loss in
weizht occurs just after digging and decreases during the
winter months. At the beginning of the veriod of warm
weather suroutinz commences and the loss in weight rapide
ly increases. <A storage temperature of slightly above
freezing is vest for seed potatoes Sut for culinary pur-
poses a moderately dry well ventilated cellar, tempera-
ture 38° to 429 F, is prefaracle.

lL, R. Taft and U. P. Hedrick,* in 1893 stored 180
pounds of votetoes in a barrel in a potato basement and
found that the tubers lost five ver cent of their weight
between Sept. 30, 1893 and Mar. 20, 1894. On May first

they weighed them azain and found an additional loss of

 

* Appleman, CO.0. Changes in Irish Potatoes During Stor-
age. Maryland Agr. Fxp. Sta. Bul. 167. pp. 327-34.

ee Toft, LT. R. and tT, P. Hedrick. Does it Fay to “eep
Fotatoes Over Winter. WYicn. Agr. Fxp, Sta. Bul.

No. 119. p. 9.
awalae

64 per cent making a total of 11$ per cent loss between
septemoer 30th and May lst. At the latter weighing the
tubers were beginning to get soft and flabby. They state
also that the basement was perhaps a little warmer than it
should have been. They recommend a well ventilated roote
house, kept at about 45°F. or a little lower as a very
good place for keepinz potatoes,

In 1897, R. H. Price® of the Texas Agricultural Ex-
periment Station, tried several metiiods of storing po-
tatoes. The author states that the tuoers rotted rapidly
there cecause of moisture and warm weather. Tubers were
stored in sand in a barrel but they rotted soon. Also,
some were placed in the ground, one foot under the sure
face; tiling w2s run thru the center to give ventilation
but under these conditions the tubers were rotted in six
weeks. Another plan was to spread the tucers on the
ground under yartial shade and cover them with hay about
two inches deep. They were kept moist oy sprinkling with
water from a hose. Avdout fifty per cent of them kept till
the first of October. Several rows of potatoes were left
in the ground and a plow was used to throw dirt upon each
row, They were left in this condition until the 15th of
August and 75 per cent had kept well; by the first of
September fifty ner cent had decayed. A few scund ones

were found on the 15th of Feoruary.

* Price, R. H,. Methods of Storaze of Potatoes. Texas

Agr. Bxpo. Sta. Bul. No. 4°,
a -5ee

vw

F, Parisot*® states that a tenverature of 89°C. is the
best for storing potatoes either for food or for seed be-
cause at this temperature the respiration, combustion and
formation of starch are considered as off setting the fore
mation of sugar, and that at a higher temperature the
quantity of sugar is smaller than at a lower temperature.

A storage test was made by W. Christie”, at the
Hedemarken County Fxperiment Station by placing potatoes
on the soil surface and covering them with alternating
layers of straw and dirt. Two piles of tubters, of the
General Cronje variety were spilled 14 meters wide by
three meters long and as high as the tuvsers would lie.
The piles were covered with two layers of straw alterna-
ting with two layers of dirt. The larger pile was venti-
lated at the surface of the ground and at the top of the
pile; the smaller one, only at the top. ‘he storage per-
iod was between Nov. 1, 1908 and Apr. 20, 1909. Temper-
ature readings at ten day intervals showed a minimum for
the period of -23.9 C. When the piles were opened, a
few potatoes in the top layer were frozen. Bacterial rot
had spoiled considerable quantities, probably because

of moist condition of the potatoes when stored. In the

 

<* Parisot, F, &.S.R. V. 16, P. 970; Jour. Agr. Prat.,
N, ser., 8(1904) No. 50. pp 763 - 765.
eeChristie, W., Ber Hedemarkens Amt. Fersookestat Verks.,

6(1910) pp. 58.
~--60~<

large piles 43 per cent of the tubers were sound as come
pared with 54 per cent in the small piles,

Denaiffe* states that the loss in weight of stored
potatoes varies with the variety.

At the Agricultural Fxperiment Station in Arkansas**

HM

and Indiana™ tests have been carried on to determine the

keeping qualities of different varieties,

* Denaife, Loss in Weight of Stored Potatoes, Jardin, 21
(1907), No 481, pp. 76-79.
*#Arkansas State Report ‘Io. 889, p. 39.

##% Indiana Bull. 1892. p. 23,
w= Jeu

Other investigators on the loss of weizht of potatoes
but whose writings are not at present available to the
writer are;

R, Heinrick (Zweiter Ber. land, Vers. Stat. Rostock
1894 »n.229).

FE. J. Woodhouse and H, L. Dutt (Agr. Jour. Bihar and
Orissa (India), 1, 1913. No. 2, pp. 1152137.

Bengal Quarterly, pvublished vy Department of Agriculture,

India, Jour 3(1909) No. 1. pp.1-12.
--8.-

Description of Experiment,

The following are the questions which the writer has
tried to answer in this work:

1. How does storing potatoes in crates, in bins
(in cellar), in pits in the ground, wrapped in newsvaper,
one and two thicknesses effect the shrinkage?

2. At what time of the storage season does the greate
est shrinkage take place?

3. Does the spraying of potatoes while growing affect
the shrinkage in storage?

1191 tubers or about 11 bushels of the Sir Walter
Raleigh variety were brushed, weighed and diameters
measured separately. Tach tuter was numbered with India
ink and the points where the diameter was measured were
marked so that it would be taken at the same points
again. Most tubers have three dimensions or diameters:
length, breadth, and thickness; the one giving the breadth
was measured. This was done by means of a caliper. Ore
dinary postal scales were used for weighing. Weighing
and measuring were begun one week after the potatoes were
dug and was completed two weeks after, on November 28th,
Cn account of the limited amount of time that the writer
had at his disposal the work could not be completed ina
shorter time as w2s desired.

100 tucers (that had been sprayed) were placed ia

each of the following conditions; in bins, in crates, in
--Se-

pits in the ground and in one and two thicknesses of
newspsver wrapped around each tuber. The potatoes in the
pits were two feet vtelow the surface of the ground, with
enough leaves and straw over them to keep the soil from
coming in direct. contact with the tubers. This was put
on so that they could be easily found when dug up again.
The potatoes wrarped in paper were placed in boxes. This
part of the experiment was repeated by putting 25 sprayed
injured tubers in the same conditions. Now, the same a-
mounts of unsprayed potatoes were placeji in the same con-
ditions. The purpose of handling injured tubers in the
same way was to see if they would be effected differently,
All of the potatoes except those in the pits were
kept in a moderately well ventilated potats scilar, the
temperature ranging from 40° ts “O°F. during the whole
Storage period. The atmosphere contained sligntly more
moisture than that outside. The weighing and measuring
was done on the 28th of each month, April 2&th being the

last.

Results.
The unsprayed potatoes, wrapped in two thicknesses
ot newspaper did not keep well. ‘They were attacked by a
fusarium rot so that in February 6 of the 100 were starting
to rot and they were thrown out of the experiment, On
March llth more had to be thrown out, making a total of

17 rotten ones in 125. The rotting, undouttedly was
Sprayed or:

 

+35 Gain:
Bs 0 oof,

: April 28

Gain

:or loss:

nsprayed_ : |:Loss ounces $

Unsprayed :
"
Sprayed :
© 8%

Unsprayed

Sprayed

Unsprayed

"
Sprayed :

" 5
Unsprayed :

|
Sprayed ;
Sprayed :

Unsprayed 3;

" ;
Syrayed :
|

: Nov. 28
:% Gain:Gain

or

loss ;Ounces

sor loss;

to Apr,

: % Gain
or

Loss

28,

 

Suban
36:
121.77:

ates

= 393

1 253d:

ene
8 t
: ere:
1.19:
el. 35;
+3. 69:
; 07:
ener
acess
: 658:

 

<10.0
a9.

45
3.5:
3207
13:3
13.5;
Vos

43.533
3.49 ;
29.5 :

3.9:
22.4:
2.7:
21.0 :
rs a

21.25: --¥0,4
~2.38:

66:
2,04: 3.6

4,94: 3.5

4.43: 16.9:

1,93: <5.
t ;
6, 5

2.96;

3.94
2.26:

1.8:
o§4 3 3

2 21.3
-61
-7.28
8
-.48
-3.86

oy age

5
iw
oO
or

‘
w
°o
BS
GI!

 

larch 28

Nov.

28

 

Sprayed
or
Insvray ed

Yd °

loss:
Jt,

ed

> Gain
% sor loss:

CM.

 

Unsprayet 3.0 :

Synrayed

Uaspraye53

Sprayed

6:
3:
2.1:
a:
6:
110.6:

Unsprayed-2.4:

"

Sprayed

‘1.4:

-.5;

 

Unspraye

"

Sprayeé

Unspraye¢

Snvayed

OO re

8, 3 :
-.7 :
one :

one «4

 

 

April 28
> Gain ;
@ sor loss:
_. : c.m,
-.43 -3.7
3450 2.9:
32: -3.2:
“1.253 242 3
-.78 : <-2.0 :
-.64 -.6
-.08 : -9.1:
-1,62 : none
wa of e1.3:
21-47:
2902 99:
“1.52 3 -9.6 |
-.48 -.8 7
none ~1.5
none “1.4

~ 54;
~.51;
~.45:
1.33;
~.30.

. 353

-1, 33:

none:
“277:
-.71:
652:

¢-1.79:

=32.3:
a)
=27,2:

~2.5;

217.2

-8.7
- 34.

-29.2

-7,
-23.1
-6.7

~29.9

-5,2

2° 33.4

-5.3

-1.4

 

-4.46
-2.51
-3.88
-1,46
22.5
-4.98
-4.8
-4,28
-4.,02
-3.42
-3.78
-5.38
-3.13
-4.74
-4.10
-.01
-. 39
-.78
-.62
Table III.
Giving the average gains and losses in weight in per cent

of sprayed and unsprayed potatoes,

Method Nov. 28
of Dec, Jan, Feb, Mar, Apr. to
Storage Apr. 28

 

In Bins -6.7624 06% -2.31% -1.874% 2.91% -2.73%

In Grates <2. 55% = 3.24% 263% 028% 2.70% -2.71%
l Thickness |

Paper 2.57% -1.37% 1.40% .41% -2.35% +1.42%
2 Thickness

Paper ~4,42% -2.98% 1.79% -.70% 2.70% +3.84% -
In Pits | 57%

aa -@-@ o-oo aoe & © --@——iew —— —s

Average 4.08% -1,.914 ~378% -1% 1.70% -2.02

 

 

Table IV.
Giving the averaze zains and losses in diameter in per

cent of sprayed and unsprayed potatoes,

Method Nov. 28
of Dec, Jan. Feb, Mar, Apr. to
Storage oe Apr. 28, __

 

 

In Bins <2,45% «,44% «,21% -.88% -.50% +-3.87%
In Crates -1.12% .02% +.44% -.50% +-.82%  -4,34%

1 Thickness
Paper -1,80% +.12% -.045%  +.4154 -.04% -3.08%

Thickness
Paper -2.17% -.38% = 54% -.50% -.66% -4.09%

In Pits -.43%

—_ aa -om

Average 1.884 +-.24% -.31% ~.57% =.53% =+3.16%
@-l0e«~

caused in part by the moisture and higher temperature kept
near the tubers by two thicknesses of paper. The other
potatoes kept well, even the injured ones. Those that
were under ground, when dug were firm and all sound. Their
increased weight was probably due to moisture absorbed
from the soil.

In some instances there was a slight gain in weight
over the preceding month as may ove seen vy referring to
table I, These gains occurred mostly during the months
of February and March when the losses in the others were
the lesst. “No reason for this gain can be given except
that it may be due to a greater amount of moisture in the
atmosphere at this time. In the case of the injured
tubers, there was no appreciable difference vetween the
percentage of shrinkage in them and the uninjured ones,
for the whole length of time.

Tables III and IV contain data which answers the
first question. For the month of December those tubers
setred in bins lost the most by weight, 6.76 per cent
while those wrapped in one thickness of paper and those
in crates showed the least loss of all stored above the
ground. This holds true also for the period November
28th to April 28th. In the other months there was more
variation and on that data no general rule can be laid
down that will hold for each month. There is a reason
why the shrinkage should take place more rapidly when

potatoes are in bins than in crates, wrapped in paper.
Table VY,

Giving the differences in per cent between sprayed and

unsprayed potatoes in changes of weight and diameter,

Unsprayed

Sprayed

Unsprayed

Sprayed

In
Bins

-2. 624%
~4, 844%

-4.15%
- 3.60%

 

In 1 Thickness
Crates Paper
23.32% -.49%
-2.10% =-5.18%
Diameters
-4.25% 2-3.50%
~4,42% <-2,67%

2 Thick. In
paper Ground Av,
4. 33% 014% -1.34%
-7.1% -99% -3.66%
-3.74%  -.15% -3.09%
-4 8% -.70% -3.24%
~eollea-
When potatoes are in piles as in bins, they are kept
warmer than when in small piles as in crates and when
wrapped in paper. According to other investigators,
Nobbe™ in particular, heat increases the losses. The
shrinkage in size as measured by the diameter, in the
main, follows that of the loss in weight but there are some
variations between December and April.

From the averages as given in tavle III and IV, one
can easily see that the greatest shrinkage takes place in
the month just following the digging, and decreases from
then till March, when it begins to increase. The chief
cause for this fact is the temperature; it being lower
curing January and “ebruary, the chemical changes are
less active and there is also less evaporation of water.

As to the question whether spraying effects the
shrinkage of potatoes, one may conclude from the figures
given in table V that it does. An average of the per-
centagees of losses and gains for unsprayed potatoes stored
in the different places shows that they have lost only 1.34
per cent of their original weight while the sprayed potatoes
placed under similar conditions have lost 3.66 per cent,

a difference of 2.32 per cent in favor of the unsprayed.
Shrinkage as measured by diameter follows the same rule
though there is not so great a difference between the

sprayed and unsprayed.

 

* EL. S. R. V.3. p.494.
eo)]D--«

Conclusions and Summary.

1. Potatoes shrink the least when nlaced in pits,
at least two feet deep and covered with earth so that
they will not freeze. The loss in weight is greatest
when potatoes are put in large piles as in bins. This is
due to the fact that there is a higher temperature in the
piles. Ventilating the cellar and lowering the tempera-
ture, but not to freezing voint, would overcome this to
a large extent.

2. As was clearly brought out by the data given,
votatoes shrink in storege more in the month just after
oeing dug than at any other time; the losses are least
in February.

3. Sprayed potatoes lose more weizht in storage

than the unspraye4d,
MICHIGAN STATE UNIVERSITY LIBRARIES

Lia

 
 

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