Note: Descriptions are shown in the official language in which they were submitted.
~o62s38
COATING OF POTP.TOES TO PREVENT GRE:ENING
This invention relates to the treatment of raw,
unpeeled potato tubers to prevent greening thercof.
Many varieties of pot~toes green rapidly when
exposed to light and this has become a major problem in
marketing potatoes in "see-through" plastic bags in super-
markets. Even exposure to light intensities as low as
100 foot-candles for as little as 24 hours can cause
greening in potatoes. Such light intensities are
frequently attained by the fluroescent lighting commonly
employed in supermarkets. Such exposures not only cause
greening, which has been shown to be due to chlorophyll
formation, but also cause bitterness and off-flavour.
Bitterness and off-flavour are believed to be due to an
excess of the alkaloid, solanine. Ingestion of green
potatoes containing large amounts of solanine may cause
severe illness and, occasionalLy, death in man.
Traditionally, therefore, green potatoes are rejected by the
consumer who, at the same time wishes to see what he or
she is buying and demands the use of transparent packaging
materials.
Many compositions and methods for overcoming the
problem of greening have been suggested. ~or example, the
use of controlled special atmospheres either in bulk or in
gas tight sale containers or bags is suggested in United
States Patent 3,533,810 but is acknowledged to be unduly
expensive and cumbcrsome, furthermore moisture accumu-
B lat~ons in the bags is considered unsightly. Similarly,
the use of specially coloured fluroescent lights ~e.g.
green and gold) has been proposed but has only limited
effectivcncss and applicability. Hot wax dipping with
- 2 -
ra/
106Z538
and without the addition of minor amounts of surfactant
to aid wetting has been proposed in United States Patent
2,755,189 and in other references but, although effective,
is expensive and suffers from the disadvantage that the
wax is relatively difficult to remove without damaging the
6kin of the potato thus severely limiting the manner in
which the potato may be prepared for table use. Wu et al
(J. Amer. Soc. Hort. Sci. 97(5) 614-616, 1972) have sug-
gested that the problem may be overcome by dipping the potato
tubers in coxn oil, such as that sola under the trade mark
"MAZOLA", but this i~ relatively expensive, may result in
suffocation of the tuber and furthermore limits the way in
which the tubers may be cooked as the oil cannot be easily
B removed without removing the epidermal layer~ or skin of the
tuber. United ~tates Patent 3,051,578 suggests treating
potatoes with a diluent containing ethylene-diamine tetra-
acetic acid (EDTA) or its calcium, sodium or potassium salts.
However, because of the sequestering action of EDTA on calcium,
only a verv limited use of the calcium salt only of EDTA is
permitted for use in foods in at least some countries in-
cluding Canada where this invention was made. Neither EDTA
nor any of its salts can be applied to raw agricultural
foodstuffs in certain countries including Canada, and hence
the method-is clearly impractical.
It is, therefore, an object of the present invention
to provide a cheap, simple, safc and effective method for
treating potatoes to prevent greening due to the production
of chlorophyll when the potatoes are removed from cold
~torage and before thcy are sold at the retail level.
3~ Is has bcen found that chlorophyll production can
bc substantially completely inhibited in an atmosphere con-
lx/~ ~
., , . , _,
106253~
taining at ledst 15~ CO2 but as noted heroinabove it has bcen
been found gencrally impractical to provide an external CO2
atmosphere. ~e have discovered that an internal C02 atmos-
phere within the potato tubers is equally effective. It
has been found that for a period of about 48 hours after
removal from cold storage, potato tubers undergo a burst
of aerobic respiratory activity which generates carbon
dioxide. ThP problem then is to provide a suitable film
around the tuber which is relatively impermeable to CO2 so
as to cause CO2 to accumulate within the tuber by aerobic
respiration so that the concentration near the potato surface
will be controlled at the minimum concentration required to
prevent greening, generally considered to be about 15%. The
film must also be capable of uniform application and rela*ive-
ly permeable to oxygen in order to preclude the development
of anaerobiosis or smothering over the range of temperatures
encountered from low temperature storage to retailing. The
film material must also be transparent and edible as it may
not be removed prior to preparation for table use.
We have found that suitable film forming materials
may be selected from long chain fatty acid derivatives commonly
used as surfactants. In particular, we have found that slight-
ly lipophilic to moderately hydrophillic polyoxyethylene sor-
bitan fatty acid esters, sorbitan fatty acid esters and poly-
ethylene glycol fatty acid esters are suitable. All of the
above surfactants are presently used by food processors, and
may also be applied to foodstuffs in pesticide formulations
and post harvest treatments. Their use is not monitored on
raw agricultural products and they are therefore believed to
be acceptable additives by Federal Regulatory ~uthorities.
Thus, by one aspect of the present invention there is
~4
lr/~
1062S38
provided a me~.hod for treating raw unpeeled potato tubers to
inhibit greening due to chlorophyll dovelopment comprising
applying an emulsion consisting essentially of a surfactant
and water to said tubers in a quantity sufficient to fo~m a thin oontin-
uous film of said surfactant thereon and drying thereon;
said surfactant containing long chain fatty acid moieties
and polyoxyalkylene or polyhydroxy moieties and having an
HLB below about 15.
The invention will now be described in more detail
with reference to the following drawings in which:
Fig. 1 is a graph showing development of chlorophyll
under elevated CO2 and normal 2 concentrations in peel re-
moved from Xennebec tubers 48 hours earlier and exposed to
laboratory temperatures (24-27C) and minimum bench level
illumination of 1076 lx.
Fig. 2 is a graph showing development of chlorophyll
under reduced 2 in peel removed from Kennebec tubers 48 hours
earlier and exposed to laboratory temperatures t24-27C) and
minimum bench level illumination of 076 lx.
Fig. 3 is a graph showing respiration measured at 21C
in Kennebec tubers in the interval following withdrawal from
5C storage. Tubers were sprayed to runoff with Tween 85 and
retained in light at laboratory temperatures (24-27C).
~ig. 4 is a graph-showing internal CO2 and 2 concentra-
tions in potato tubers (numbered clone) sprayed to runoff with
various concentrations of Tween 85 immediately following with-
drawal from 5C storage and measured after 5 days at laboratory
temperaturcs (24-25C); and
Fig. 5 is a graph showing changes in internal CO2 and 2
concentrations in Kennebec tubers sprayed to runoff with 4% Tween
85 immediately after withdrawal from 5C storage.
~s previously noted, the film ~orming materials
--5-
lx//.. '1
106Z538
found suitable to resist the oxodus o CO2 from
the potato tubers are generally long chain fatty acid
esters or glycerides which are relatively common sur-
factants. We have found that the series of polyoxyethylene
sorbitan fatty acid esters sold under the Registered
Trade Mark TW~EN by Atlas Chemical Corp. are generally
suitable and TWEEN 85 in particular. Similarly, the series
of sorbitan fatty acid esters sold under the Registered
Trade Mark SPAN by Atlas Chemical Corp.
are generally suitable. Polyethylene glycol fatty acid
esters selected from those sold under the Registered Trade
Mark PEGOSPERSE may also be suitable.
In order to illustrate the present invention a series
of experiments was conducted.
Example I
Tubers from cvs, Avon, Fundy, Keswick and Kennebec
and a numbered clone were used. Because Kennebec greened
most readily it was used most often. Whole tubers,
previously stored in darkness at 5C, were exposed to
laboratory temperatures of 2Io-27oc and to a minimun illum-
ination at the bench level of 1076 lx (cool white
fluroescent) on a continuous basis. When required, discs
of peel tissue were cut with a No. 6 stainless cork borer
and excised at a depth of 0.16 cms with a stainless steel
knife.
Chlorophyll in potato discs was estimated visually
and by the method of Arnon (Plan.t Physiol. 24,1-15, 1949)
using a Beckman DB spectrophotomcter and 5 discs (0.75 g)
per sample.
CO~ and 2 were determined with a Fry analyser
whose calibrated capacity WAS matched with a 1 ml all glass
6yringe. Internal gases from tubers were sampled using a
~ * trademark
r~ - 6 _
~062538
quick evacuation technique. This technique utilizes
the purging action of steam at prevailing atmospheric
pressure, and the subse~uent vacuum formed after the
~ystem is sealed and the steam condensed.
~ espiratory CO2 was determined with the aid
of a Beckman infra-red gas analyser.
Discs sampled from treated and untreated
potatoes were variously exposed to air and to concentra-
tions of CO2, 2 and balance N2, by placing them on
moistened Whatman No. 3 filters in open glass dishes;
- tissues and dishes were contained in humid environments
inside wide mouthed glass preserving jars of 3640 ml
capacity.
The tubers were sprayed to the point of runoff
with an aqu~ous emulsion formulated with Tween 60 (poly-
oxyethylene (20) sorbitan monostearate) or Tween 85
(polyoxyethylene (20) sorbitan trioleate). All applica-
tions were made immediately after withdrawal of the tubers
from storage.
RESULTS
Anti-greening treatments: The amount of material required
to control greening varied substantially with the cv
(Tables 1 & 2). A 15% emulsion of Tween 60 con-
trolled greening in the susceptible Kennebec cv. On a
weight of material applied basis, Tween 85 was the most
eficient substance; a residual of 0.40 g/kg of tuber,
applied by spraying to runoff with a 5% emulsion was
generally more than required. Control of greening was
largely assessed by visual means and was considered more
~han adequate if chlorophyll did not exceed 0.40 mg/100 g
peel.
--7-
Ir/" ~
1062538
C2' 2~ and greening in exciscd peel: When discs from
control tubers were retained in atmosphercs containing
high concentrations of CO2 (and 20~ 2 balance N2),
chlorophyll development decreased with increased CO2
concentration (Fig. l). However, concentrations as high
as 40% allowed some chlorophyll formation. When discs
were retained in atmospheres of reduced 2 (and 0.0~ CO2,
balance N2), there was no inhibition of chlorophyll
formation until 2 concentrations were reduced below 5%
(Fig. 2). When discs were retained in atmospheres of
increasing CO2 concentrations with the 2 fixed at a
slightly reduced level (15~), and balance in N2 the results
closely resembled those of Fig. l.
C2 output from tubers treated with Tween 85: Tween 8S
suppressed or dPlayed the norma~ respirational "burst"
which results when the tuber is removed from low tempera-
ture storage to higher temperatures (Fig. 3) but tended
to sustain the CO2 output at higher levels when compared
with controls over the whole period of observation (15
days approx.). Ultimately respiration declined sharply
toward the control level.
Internal CO2 and 2 in tubers treated with Tween 85: The
. . .
concentration of the applied surfactant, and thus pre-
sumably its weight, had a direct influence on the accumula-
tion of internal CO2 and the decline in internal 2 (Fig. 4).
In this instance a concentration of 4% Tween 85, which was
sufficient to control grecning, produced average internal
concentrations of 17% CO~ and 16% 2 (approx.) 5 days after
~reatment. Th~ pronounced accumulating effect of 4~ Tween
85 on internal CO2 in ~ennebec tubers is seen in Fig. 5.
Althou~h both CO2 and 2 concentrations began to return to
lr/,-~
106Z53~3
.
T nL~ 1
Grc~n color devclopment in potato tubers trcated
with aqueous emulsions of Tween G0 and rRtained at
laboratory tem~erature~ (29-27C) under a
minimum of 107G lx fluorescent light (CW)
.. .. . _ .
Chlorophyll (mg/100 g peel)
Kennebeca Avon~ Ke6wic~;b
Control (water) 6.75 3.67 4.44
5~ Tween 60 8.08 0.28 1.11
10~ Tween 60 3~31 0.08 0.39
15% Tween 60 0.31 - -
Initial color . 0.07 0.05 . 0.06
- . .. . _ - '. .
a After 13 days
b After 36 days
TABLE 2
Greening assessment in potato tubers treated with
aqueous emuisions of Tween 85 a~n~ retained at laboratory
~- temperature (24~27C) under a mi`n1mu~ of 1076 lx
.fluorescent light (CW) ~ w~
I .. IL3 - .. . . . . ..
Greening - after 6 days
~ ween-85 . ~~~
Yariety. 0-.-0 2.S ~ 5.0 -:7.S
. _ . _ .. . _ ... _ . , . . _ .
Avon
Keswick +- - - ~
Fundy +
Kennebec~+ +-
Greening - after 13 days
~von ~ +-
Ke~wick + +-
~undy ++ ~ _ ~
Kennebec~+~+ +~ - -
.
~06Z538
normal 6 days after treatment, CO2 concontxations still
d~fered sharply from thc controls after 16 days.
Other observations: In some instances both Tween
60 and Tween 85 were applied to tubers at substantially
higher concentrations than were required to stop green-
ing. Tween 60 at 20%, and Tween 85 at 7.5% produced
glossy surfaces (an apparent film) which persisted for
several hours and even days. Vnder these conditions
internal CO2 approached 100% (>90%) and internal 2
approached zero (<1.5~) and some tubers suffocated. When
these glossy suraces were abraded, (or punctured), thus
removing both surfactant and epidermal layers, greening
developed in the area proximal to the abrasion.
Example 2
The experiments described in Example 1 were
repeated the following season using a more comprehensive
collect;on of Tweens. Kennebec tubers were again sprayed
to runoff, but dips in warmed emulsions were used to
apply Tween 61 (65.6C) and Tween 65 (40.6C). Visual
assessment was relied on to determine the presence or
absence of greening. Chlorophyll concentrations were
determined in tubers treated at surfactant concentrations
proximal to the "optimum" using the method of ~rnon ~ibid),
0.75 g of peel, and a Beckman Model DB spectrophotometer;
in greened potatoes, tissues
--10--
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~o6Z538
were ~elected from thc greenest areas. Greening was
observed to occur when determinations exceeded 0.85 mg/75 g
peel.
When compared with previous observations, the
figures in Table 3 indicated an increased effectiveness
With Tweens 20, 80, and 60, while that of Tween 8S
remained unchanged.
Using linear interpolation, the weights of sur-
factant applied at the concentrations listed in Table 3,
and the figure 0.85 mentioned above, the weight rate of
each surfactant required to control greening was calcu-
lated and is listed in Table 4. It is readily apparent
that Tweens vary widely in their relative efficacy, and
that efficacy in terms of concentration does not
necessarily relate to efficacy in terms of mass applied.
Example 3
~ old stored (5C) cv Kennebec tubers were
sprayed with aa,ueous emulsions of mixtures of Tween and
Span and then exposed to continuous fluorescent illumin-
B ation k~s 1076 lx) for 15 days. The resul~s are tabulated
in Table 5.
- -Example 4
Cold stored Kennebec tubers were sprayed with
various PEGOSPERSE surfactants and exposed to fluorescent
light as in Example 3. The weight of surfactant required
to control greening for the different surfactants is
tabulated in Table 6.
106;~538
TAB~E 3
Tween surfactants in aqueous emulsion ranked for
greening control in Kennebcc tubcrs. Tubers were
treated on removal from 5C storage, retained 15
days at laboratory temperature (21 ~ C) under
continuous fluorescent illumination re~ 1076 lx).
Reduced greening Zero qreening
Rank ~lghest conc. Chlorophyll Lowest conc.
- tested (%) % of control . tested (%)
1. Tween 81 2.0 17.3 3.0
2. Tween 65 2.0 81.3 4.0
3. Tween 85 4.0 27.9 5.0
4. Tween 61 4.0 26.4 6.0
5. Tween 60 4-0 65.0 6.0
6. Tween 80 - 10.0 16.' 12.0
7. Tween 21 9 0 28.9 12.0
8. Tween 40 12.0 18.0 15.0
9. Tween 20 12.0 59.8 16.0
.... . .. . . _ . .
P.O.E. (No.) - Number of polyoxyethylene units
Tween 81 - P.O.E. (5) sorbitan monooleate
Tween 85 - P.O.E. (20) " trioleate
Tween 80 - P.O.E. (20) " monooleate
Tween 61 - P.O.E. (4) " monostearate
Tween 65 - P.O.E. (20) " tristearate
Tween 60 - P.O.E. (20) " monostcarate
Tween 40 - P.O.E. (20) " monoplamitate
Tween 21 - P.O.E. (~) " monolaurate
Tween 20 - P.O.E. (20) " monolaurate
Span 20 - P.O.E. (0) " monolaurate
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1062538
T~LE 4
The weight of various Tween surfactants requirçd to be
applied eithcr as an aqueous spray or dip to control
greening in Kcnnebec tubers subscquently cxposed for
15 days to continuous fluorescent light (cw 1076 lx)
. at laboratory temperatures (21-27C?
.
Surfactant of tubérs
.
1. Tween 81 - P.O.E. ~5) sorbitan monooleate 0.15
2. Tween 85 - P.O.E. (20) " trioleate 0.23
3. Tween 60 - P.O.E. (20) " monostearate 0.27
4. Tween 80 ~ P.O.E. (20) " monooleate 0.44
5. Tween 40 - P.O.E. (20) I- monopalmitate 0.71
- 6. Tween 65 - P.O.E. (20) " tristearate 0.83
7. Tween 61 - P.O.E. (4) " mono- ** 0.94
8. Tween 20 - P.O.E. (20) " mono~a~ra~ee 0.98
9. Tween 21 - P.O.E. (4) " monolaurate 1.32
.
P.O.E. (No.) - Number of polyoxyethylene units
Applied as a dip at 40.6C.
Applied as a dip at 65.6C.
- 13 -
1062538
TABLE 5
Chlorophyll development in cold-stored Kennebec tubers
(5 C) after 15 days cxposure at laboratory temperatures
~21-27C) to continuous fluoresccnt illumination (CW
1076 lx). Some tubers were sprayed with aqueous emulsions
of Tween and Span prepared in 1:1 ratios by weight.
~eadings <0.85 mg indicate no chlorophyll development
_
* Chlorophyll (mg/75 g peel)
Tween :
- Span Tw 2 0 Tw 4 0 Tw 60 Tw 65 Tw 8 0 Tw 8 5
conc (~) Sp 20 Sp 40 Sp 60 Sp 65 Sp 80 Sp 85
.
- 6.0:6.0 0.18+.04
5.0:5.0 0.15+.05
4.0:4.0 0.67+.03 2.50+.01 0.16+.00
3.0:3.0 1.74+.09 4.14+.08 2.81+.07
2.5 2.-5 0.45+.0~ 0.93+.05
2.0:2.0 2.61+.05 0.75+.08 0.29+.12
O 4.04+.22 5.29+.73 6.54+.04 4.05+.23 6.54+.0a 5.29+.73
Tween 20 - polyoxyethylene (20) sorbitan monolaurate
Tween 40 - " " " monopalmitate
Tween 60 - " " " monostearate
Tween 65 - " " " tristearate
Tween 80 - " " " monooleate
Tween 85 _ n ~ trioleate
Span (no) - consists of corresponding Tween molecule without-
polyoxyethylene units, i.e., Span 20 - sorbitan monolaurate.
TABL~ 6
The weight of various Pegosperse surfactants applied as
aqueous sprays to control greening on cold-stored (5C)
Kennebec tubers subsequently exposed for 15 days to con-
tinuous fluorescent light (CW 1076 lx) at laboratory
temperatures (21-27C).
Wt/kg
Surfactant of tubers
.
1. polyethylene glycol (400) ditri ricinoleate 0.15 g
2 . n H ~I dilaurate 0.20 g
3 ~ H ~ monotallatc 0. 24 g
4 . n n ~ dioleatc 0.36 g
5. ~ H (200) monolauratc 0.56 ~
6. n H , n dilaurate 0-75 g
ra/ B 14-
1062538
From the above experimental results w~ have
determined that greening control depcnds, at least to
some extent, upon the molocular structure of the surfac-
tant added and it is believed that the following
generalizations hold:
Comparing Tweens 81, 85, 80 -
~hortening POE
increasing fatty acid ) beneficial
substitution
LO Comparing Tweens 65, 61, 60 -
shortening POE
increasing fatty acid ) beneficial
substitution
Comparing Tweens 20, 21 -
shortening POE ) beneficial
Comparing the fatty acid substitutions beneficial effects
may be ranked: tristearate > trioleate > monostearate
> monooleate > monopalmitate > monolaurate.
Thus, it is believed that ef~ec':iveness in greening
control is related to the HLB (Hydrophile-Lipophile Balance)
rating of the surfactant used. The HLB rating of a
surfactant is a well-known method of assigning a numerical
value to surfactants to provide a classification based
upon their behaviour and solubility in water. Essentially
the HLB rating is a function of the ~leight percentage of
the hydrophilic portion of the molecule of a non-ionic
surfactant. The experimental procedure to determine HLB
values is long and tedious but has been described in detail
in the literature (J. Soc. Cosmetic Chem. I, 311-326, 1949),
and eomparative ranking lists have been published by
Griffin in J. Soc. Cosmetic Chcm. V, No. 4, p.249, Dec.,1954.
Reprosentative surfactants examined for use in tho
prcsent invontion have liLB ratings (as listed in Tho
_ 15 -
r~/
106Z538
Amer~can Perfumer and Essential Oil Review, Vol. 65, No. S,
p.27-29, May, 1955) as follows:
T~BLE 7
. . .
Surfactant Chemical DesignationHLB Rating (+l)
.. .. ...
Span 85 Sorbitan trioleate 1.8
Span 65 Sorbitan tristearate 2.1
Span 80 Sorbitan monooleate 4.3
Span 60 Sorbitan monostearate4.7
Span 20 Sorbitan monolaurate 8.6
Tween 81 Polyoxyethylene sorbitan
monooleate 10.0
Tween 65 Polyoxyethylene sorbitan
tristearate10.3
Tween 85 Polyoxyethylene sorbitan
trioleate 11.0
Tween 60 Polyoxyethylene sorbitan
monostearate14.9
Tween 80 Polyoxyethylene sorbitan
monooleate 15.0
Tween 40 Polyoxyethylene sorbitan
monopalmitate 15.6
Tween 20 Polyoxyethylene sorbitan
monolaurate16.7
_ . . _ . .
From a consideration of the molecular structure of
the surfactants outlined above in relation to the test
results reported in Examples 1-4, we have determined that
- for effective and economical control of greening in
susceptible potato tubers, surfactants having an HLB rating
below about 15 are most suitable. Preferably, a surfactant
having an HLB rating in the range between about 8.6-11.0
should be employed. Above HLB 11, the amount of surfactant
required for effective control may become excessive in some
potato varieties.
In a modified process according to the present
invention we have found that when the escape of respirational
C2 is impeded and thus cau.sed to accumulate within the potato
rA/ - 16 -
1062538
tuber tissue, the acids participating in the respiration (TCA
cycle acids) may accumulate, or their rate of consumption may
be reduced. Additionally, other plant acids may also accumulate.
Thus, potato tuber tissues experiencing anaerobic conditions
are known to accumulate lactic acid and applicants have, in fact,
observed an increase in hydrogen ion concentration (pH 6 to
pH 3.5 approx.) in tubers treated with effective concentrations
of surfactant. Further, the presence of mild acids in plant
tissues is known to cause a proton shift reducing chlorophyll
to brown pheophytin. However, when acid is applied externally
in a non-phytotoxic manner, new chlorophyll develops upon
exposure of the tuber to light, as soon as the applied acid
is-metabolized or diluted. But, if the escaping respirational
C2 is restricted slightly with a "small" amount of surfactant
(that is less than what is required to control greening), the
applied acid may be caused to persist for a few days, thus
precluding the redevelopment of chlorophyll for a few days.
This effect however can be greatly reinforced by a "tightening"
of the surfactant film applied to the tuber which is caused by
the addition of certain plant acids. These plant acids may be
added to the aqueous surfactant emulsion at the time of
preparation and appear to be compatible (soluble in emulsion)
with the surfactant. Thus, the amount of surfactant required
to produce an effective film upon application to the tuber
may be reduced far below the concentration required for control
of greening by the surfactant alone, and by the addition of
increasing amounts of the selected acid can be rendered
sufficiently impermeable to CO2. Effective combinations of
surfactant and selected acid are many, and permit attenuation of
the safe and effective concentration ranges.
Examples of acids which are effective in "tightening"
ra/ - 17 -
1~)62538
the surfactant films, are enumerated in Table 8. An
indication of their relative performance is shown in Tables 9,
10 and 11.
TABLE 8
The relative inhibitory effect on greening in
Kennebec tubers sprayed to run-off with aqueous
emulsions of Tween 60 combined with various plant
acids. Tubers were sprayed upon removal from
3.3C storage and retained at 22.2C under
fluorescent illumination (1076 lx).
.
. .
Treatment Days before
greening
. . . _ . _ . . _
1. Water only
2. 2% Tween 60
3. 2% Tw 60 + 7.5~6 lactic ac. 3
4. 2% Tw 60 + 15% lactic ac. 5
5. 2% Tw 60 + 596 ascorbic ac. 3
~ 6. 2~6 Tw 60 + 109~ ascorbic-ac. - 4
7. 2% Tw 60 + 7.5~6 tartaric c-c. 3-6
8. 2% TW 60 + 15% tartaric ac. 5-8
9. 2% Tw 60 + 596 D-isoascorbic ac. 3
10. 2% Tw 60 + 10% D-isoascorbic ac. 8 plus
11. 2% Tw 60 + 5% citric ac. 17 plus
. .
TABLE 9
Internal CO and O in Kennebec tubers treated
with (i) wa~er onl~ - controls (ii) Tween 60
(iii) Tween 60 plus citric acid, upon removal
from 3.3C storage and retained for various
intervals at 22.2C under fluorescent
illumination (CW-1076 lx).
.
.
Day
O 3 5 7
Treatment *~ C2 2 C2 2 2 2 2 2
.
Control 3.5 19.5 2.619.5 4.1 l9.S2.3 18.8
2% Tween 60 3.5 19.53. 719.0 3.519.~ 2.5 19.0
2% Tw 60 + 5% citric ac. 3.5l9.S 7.8 18.412.7 17.6 lS.S 16.3
2% Tw 60 + 10% citric ac. 3.5 19.5 9.518.516.7 lS.925.1 15.2
_ _ . . . _ . . .
* % C2 and % 2
measurement~ entered under day 3 and 5 actually made on day 2 and 4
respectively
ra/ - 18 -
~062538
TAsLE 10
Respiration of Kennebec tubers in the
interval following withdrawal from 3.3C
storage when retained at 21C and under
fluorescent illumination of 1076 lx. Tubers
were sprayed immediately upon removal from
storage with (i) water (controls), (ii) 2% Tween 60,
(iii) 2% Tween 60 plus 7.5% lactic acid,
. (iv) 2% Tween 60 plus 15% lactic acid,
(v) 2% Tween 60 plus 7.5% tartaric acid,
(vi) 2% Tween 60 plus 15~ tartaric acid.
.
Respiration rates (ml C0 ~ gtissue/hr)
2% Tw 60+2% Tw 60+ 2% Tw 60+ 2% Tw 60+
Day Control2% Tw 60 7.5% lactic 15% lactic 7.5% tartaric 15%
tartaric
0 5.0
1 15.9 11.5 5.3 3.1 1.9 1.7
2 17.3 13.5 7.9 6.2 3.5 3.3
3 lS.l 13.2 8.6 7.1 4.5 4.6
8 6.4 7.2 8.1 7.2 6.8 6.8
20 9 5.5 6.2 7.0 6.7 6.5 6.5
5.4 6.0 6.9 6.7 7.7 6.8
13 4.3 4.3 5.3 5.9 7.4 7.0
TABLE 11
Respiration of Kennebec tubers in the interval
following withdrawal from 3.3C storage when re-
tained at 21C and under fluorescent illumination
of 1076 lx. Tubers were sprayed immediately upon
removal from storage with (i) water (controls),
(ii) 2~ Tween 60, (iii) 2~ Tween 60 plus 5% citric
acid, (iv) 2% Tween 60 plus 10~6 citric acid,
(v) 2~ Tween 60 plus 15% citric acid.
Respiration rates (ml CO~cg tissue/hr)
2% Tw 60+ 2% Tw 60+2% Tw 60+
Day Control2% Tw 605% citrie ac.10% eitric ac. 15% citric ac.
0 6.7
1 18.4 11.2 2.2 1.9 1.4
2 17.0 11.8 3.3 2.6 1.7
3 15.2 13.2 6.6 5.3 4.4
4 10.5 10.7 6.6 5.8 5.2
40 7 6.6 7.4 7.7 6.8 8.6
9 6.3 6.0 8.5 8.6 13.0
6.7 5.7 9.7 9.2 13.3
11 5.7 5.0 9.4 9.5 11.9
14 5.6 3.8 10.0
16 6.4 4.6 12.1 12.4 12.2
17 7.0 4.7 13.3 13.6 12.8
.
B ra/ - 19 -
106Z538
Similar tests have also been conducted with
Tween 81 and Tween 80, with substantially similar results.
Table 9, which is a similar and analogous
compilation of data to that shown in Figs. 4 and 5, clearly
shows the effect that adding certain acids to an aqueous
surfactant emulsion ~or solution) has on the build-up of
internal CO2, so essential to the control of greening in this
process, within the tuber. This physical phenomenon can also
be appreciated by examining Tables 10 and 11 which are analogous
to Fig. 3.
ra/ - 20 -
