Research Report, March
20, 2001:
Raw Juice Quality Study #1
Enhanced Vitality Research
Measurement of Oxidative Degradation Over Time of
High-quality Fresh Raw
Vegetable Juice Stored
Under Refrigeration
and
a Comparison of Untreated Raw Juice with Raw Juice Treated with a
Hydride (H-)-donor Antioxidant
by
Vinny
Pinto, MA*
Summary
and Overview
For
a plain English simplified summary and overview of what was
learned in
this and related studies and trials,
including guidelines on fresh raw juicing and preservation under
refrigeration,
please see the
Summary
and Overview page.
Introduction
There
has
been some speculation in the raw foods world for at least several years
regarding the viability of fresh raw vegetable juices, namely: for how
long after juicing do the juices retain maximal or near-maximal
nutrient value? Nutrient value has
usually been informally defined as preservation of important nutrients
in
the juice, including vitamins, enzymes, proteins and complex
carbohydrates,
and including numerous plant substances found in juices which may be
poorly-identified
and enumerated by scientific researchers to date. The largest
single
source of degradation in a refrigerated raw fresh juice (as well as
most
other raw foods) is oxidative degradation due to a family of so-called
free
radicals known as reactive oxygen species (ROS), which include peroxide
ions,
superoxide anions, and other aggressive oxygen species, including O3
and
other
short-lived oxygen radicals. It is well known that the degree
of exposure
during juicing (and after) of the juice to heat and ambient air
containing
oxygen, particularly tiny bubbles of oxygen which are finely dispersed
(as
in repeated grinding, blending or mastication), can rapidly accelerate
the
formation of these ROS components, and thus, rapidly accelerate aging
of
the juice and its nutrient quality.
For example,
it has long been acknowledged that the method of juice extraction
greatly affects juice quality. As noted above, methods which involve
excessive heating, grinding, or mastication
tend to rapidly accelerative ROS processes. In the world of
consumer
and commercial (juice bar or food stand) juicers, several studies,
along
with massive anecdotal evidence, have strongly indicated that
centrifugal
juicers generally yield juice with the greatest oxidative damage,
followed
by masticating juicers (such as the Champion and the crushing stage of
some
Norwalk juicers), which tend to produce a juice with
significantly
less oxidative damage. However, the above-mentioned evidence
indicates
that twin-gear juicers (such as the Green Life and the Angel) tend to
produce
the least heating and least exposure to oxygen, yielding the highest
quality
juices.
A number of
persons in the raw foods world have come up with guidelines for the
quality of each class of juicer, and, while there is some variance,
most seem to agree that:
- the
juice from a centrifugal juicer must be consumed almost immediately
after juicing to take advantage of nutrients before serious oxidative
damage can progressively damage nutrients
-
the
juice from a masticating juicer
may be refrigerated and stored for up to 24 hours, while maintaining an
acceptable nutrient quality
- the
juice from a twin-gear juicer may be stored under refrigeration for up
to at least three days, while maintaining an acceptable nutrient quality
Indeed, most
"serious" devotees of juicing
seem to end up using twin-gear juicers in order to yield higher juice
quality
and the ability to juice vegetables in quantity and then store the
juice
in 8-ounce or 16-ounce tightly sealed containers under refrigeration
for
a few (3+) days, while still maintaining high nutrient
quality. Recently,
a fair number of raw foodists who eat raw vegetable and animal diets
(RVAF
diets) seem to be adding small amounts of a proprietary hydride (H-
) donor antioxidant (MegaH™ aka MegaH-™
, see note 1) to the raw juice before storage to decrease oxidative
damage overtime and to increase useful storage lifetime of the juice.
The
purpose
of the present study was two-fold, to determine, using
oxidation-reduction potential (ORP) as a
relative indicator of oxidative damage versus antioxidant reserves, the
oxidative
degradation of fresh raw vegetable juice from a twin-gear juicer,
stored
under refrigeration in tightly sealed containers, as follows:
1)
the degree of oxidative degradation over four days of the unaltered and
unadulterated juice (this juice and the periodic samples therefrom were
labeled the control batch juice) 2)
the degree of oxidative degradation over 7 days of juice (same bulk
batch source as above) with a small amount of H-
donor (MegaH aka MegaH-) antioxidant added as prophylaxis
to retard oxidation (this juice was labeled the experimental batch
juice)
Design
For
all
studies, the primary measure
of oxidative degradation of the raw juice was oxidation-reduction
potential
(also called "redox") or ORP. ORP is measured with an ORP
meter, and
such meters range in cost from $89 to $2,000. (The ORP meters
used
in this study were laboratory-quality and were priced in the range of
$300
apiece.) ORP measures the degree of oxidation or reduction
(reduction is absence of oxidation and is tantamount to anti-oxidant
power) of a water-based substance, and the ORP scale ranges from -1,200
(strongly reducing) to +1200 (strongly oxidizing.)
For example, hydrogen peroxide from your medicine cabinet or chlorine
bleach from under your sink (mixed with some water) would both show an
ORP near +1,200, indicating that they are potent oxidizers. On the
other hand, so-called "alkaline" ionized water from a home water
ionizer would read an ORP of from -150 to -800, indicating moderate to
strong reducing (antioxidant) properties.
Most raw
organic green vegetable juices from a good juicer will show an initial
ORP from -100 through +160, indicating a fairly good store of primitive
(reducing) antioxidants in the juice (the pH will usually be about 5.6
to 5.9, indicating presence of plant acids). Raw organic
carrot juice will sometimes show an ORP as low as
-170 to -200 (and a pH of about 6.8 or higher, since carrots are not
as
acid as some other vegetables), as will some raw organic wheatgrass
juice. However, most green juices and vegetable juice mixes
show an ORP between -100
and +160. As a juice ages and gradually oxidizes (e.g., due
to any
of these factors: heat, exposure to air and light, time), the ORP will
climb
steadily, finally reaching a "settling" zone of perhaps +350 to
+450. As a juice oxidizes, it steadily loses nutrient
value. In general,
one would wish to see raw organic green juices in storage remain at or
below an ORP of +180, although one could safely say that an ORP of up
to
perhaps 210 might be acceptable under some circumstances. A
better way of stating the matter might be this: you do not want to see
the ORP rise (toward +1,200) more than 80 counts over the initial value.
Secondary
measures of juice quality and oxidative damage were observations of
smell, taste and appearance, made by the researcher at each test
period. pH (acid-alkaline), juice temperature, and electrical
conductivity were measured as well at each test period, for reference
purposes.
One gallon
of juice was to be prepared as a bulk batch and stirred well
immediately after extraction, and then immediately decanted through a
fine strainer (to remove larger particulates) into two nominal 16 ounce
containers, one labeled "control" and the other labeled
"experimental". ORP and pH were to be measured
immediately for both containers, and then MegaH (aka MegaH-)
antioxidant was to
be added to
the container labeled "experimental" and stirred well. ORP of
this container
was measured again after 3 minutes, and then both containers were
refilled
("topped-off") from the bulk pitcher to leave less than 3 m or airspace
(headspace)
above the liquid surface, and then both bottles were tightly sealed and
stored
on a refrigerator shelf kept at a nominal temperature of 39 degrees
F. Periodic measurements of ORP and pH as well as evaluations of taste,
smell
and appearance, were made approximately every 1.5 to 2 days, with more
frequent
one-day measurements after the 4th day. Based upon prior
anecdotal
reports and previous observations made by the researcher, it was
decided
that the measurement of samples from the control batch would cease
after
4 days, and the measurements of samples from the experimental batch
would
cease after 7 days.
(Any raw
juice left over from the original batch (1 gallon, minus 2 x 20 ounces)
would be decanted into storage containers for subsequent consumption by
the author.)
The
experimental batch of juice was treated as follows after the decanting
from the source bulk batch into its 570 ml. container: pure MegaH™ (aka MegaH-™) powder
(proprietary silica hydride,
obtained from Flanagan Technologies,
Flagstaff, AZ) was added to the liquid at the rate of 250 mg per liter
(33.8
oz) (250 mg was the amount of MegaH™ (aka
MegaH-™) then found in one capsule of
MegaH™ marketed
in capsule form), or roughly the equivalent of 1 capsule of MegaH per
quart,
and then stirred briskly for ten seconds.
The source
batch was one gallon of fresh raw organic vegetable juice, juiced in a
Green Life twin-gear juicer, using fresh organic pre-washed
(winter-time) vegetables in the following approximate
ratios by weight :
| celery |
45%
|
| parsley |
18%
|
| cucumber |
18%
|
| carrots |
9%
|
| beets |
9%
|
| habanero
pepper (1
ounce raw) | trace
|
Methods
Study
performed in mid-March, 2001 by the author. Nominal
refrigeration storage temperature for both containers was 39 degrees F,
with average deviation of +/- 2 degrees or less. Juice test
batches refrigerated immediately after juicing.
All ORP
and
pH measurements were made with a laboratory-grade
microprocessor-controlled instrument using separate electrodes for
measurement of ORP and pH, and all measurements of samples were
repeated and checked with a second laboratory-grade instrument to
ensure reasonable accuracy. All ORP electrodes were
rinsed after each use in cold water, then soaked for 10 min. in an
acidic, oxidizing water solution
(pH = 2.4; ORP = +1,150) to clean the electrodes and reverse any ion
penetration/degradation
of electrode shell, followed by rinse in purified water prior to
storage.
Failure to clean electrodes will result in progressive degradation of
ORP
electrode, reducing sensitivity to the H ions (reducing environment)
and
resulting in regression of ORP readings toward a low positive range (~
+300).
Some ORP
measurements of raw vegetable
juices tend show to drift prior to settling, particularly when the ORP
is
in the range of -100 through +400 and not strongly buffered by ion
reserves
in the liquid. Much of the drift is likely due to
interactions between
the ORP electrode inner shell and various particulates and colloids in
the
juice, as well as electrostatically-induced drift of same. For this
reason, all ORP measurements were allowed to "settle" for 3
minutes prior to recording final reading.
The
two test
batches of juice were stored in one-pint heavy-duty, wide-mouth Nalgene
(TM) HDPE thick-walled bottles in a 39 degree F refrigerator. ORP,
smell, taste and appearance were measured approximately every 1.5
to 2 days, or more frequently as needed. These plastic
bottles were chosen because they offer almost as much impermeability to
oxygen and other substances as glass, and yet are far less
fragile. (Indeed, the current author uses ten of these pint
bottles to store his
day-to-day green juice after juicing.)
Decanting of
liquid samples from the control and experimental batch bottles for
periodic measurement resulted in steady and progressive lowering of
liquid surface below bottle cap, resulting in increasing headspace in
container above liquid surface which would have been normally occupied
by ambient room air containing 20% to 21% O 2,
and offering the potential of accelerated oxidative degradation over
liquid stored in a filled bottle with little or no (3 mm or less)
headspace. Since air is about 21% oxygen, this air above the
juice surface is a potent and major force in accelerating oxidation
over what would be seen in juice stored in a container with little or
no air space above the juice (e.g., a full bottle,
well-sealed). If this were allowed to happen, the results of
the study would show greater rate of oxidative degradation than would
be
seen in the "real world", where the juice would be stored in an 8 or 16
ounce
bottle and would be used all at once or at least over no more than an
8-hour
period.
Thus, to
manage or control this factor and to reduce this exposure to O2
in the headspace, all headspace (dead air space) above liquid in
storage containers was flushed and filled with an inert gas after each
opening/decanting and prior to subsequent return to refrigerated
storage. The flush/fill inert gas used was
high-purity helium (He, 99.997% tech. grade), yielding O2
concentration
of < 1% in headspace after flushing and filling, as
measured with
an oxygen probe during pre-trial tests.
Storage
containers were NALGENE (TM) brand wide-mouth food-quality thick-wall
HDPE storage containers with screw caps, with nominal 500 ml
(1 pint) capacity and actual capacity of ~570 ml (about 17.5
ounces). These containers are commonly available via
scientific catalogs and in many camping and sporting goods stores,
sold
as leakproof, heavy-duty bottles for storage of liquids in rough
environments.
The
thick-wall Nalgene (TM) HDPE containers and thick screw caps, which
form an airtight and sturdy seal, offer
an impermeability to moisture and oxygen only slightly less than that
of
a glass container of similar capacity and dimensions while offering
far less vulnerability to breakage. Use of glass
containers with
airtight lids would yielded have yielded slightly lesser oxidative
degradation
over time than observed with the HDPE containers, due to a slightly
lower
rate of incursion of oxygen through walls of the glass container.
Results
Table
I. Study: High-quality
Fresh Raw Juice Storage Under Refrigeration and Evidence of Oxidative
Degradation.
ORP and pH vs.
Elapsed time in storage in sealed 570
ml (17.6 oz.) HDPE containers
rankings
for quality measures
(taste, smell and appearance) were on a scale of 1 to 5, as follows: 1
= poorest, 5 = excellent
note:
increasing headspace due to decanting of liquid for measurements was
flushed prior to storage with inert gas (He, 99.97% tech. grade),
yielding O2 presence of < 1%
Elapsed
Time
hours
| Elapsed
Time
days
| Control
ORP
| Control
pH
| Control
Quality
taste
| Control
Quality
smell
| Control
Quality
appearance
(color, etc.)
| Experim.
ORP
| Experim.
pH
| Experim.
Quality
taste
| Experim.
Quality
smell
| Experim.
Quality
appearance
(color, etc.)
|
| 0
| 0
| +090
| 5.6
| 5
| 5
| 5
| -596
| 5.9
| 5
| 5
| 5
|
| 48
| 2
| +128
| 5.7
| 5
| 5
| 5
| -545
| 5.9
| 5
| 5
| 5
|
| 84
| 3.5
| +156
| 5.8
| 5
| 5
| 5
| -534
| 5.8
| 5
| 5
| 5
|
| 100
| 4.13
| +167
| 5.9
| 4.8
| 4.8
| 4.8
| -529
| 5.8
| 5
| 5
| 5
|
| 108
| 4.5
| --
| --
| |
|
|
-525
| 5.9
| 5
| 5
| 5
|
| 120
| 5
| --
| --
| |
|
|
-522
| 5.9
| 5
| 5
| 5
|
| 144
| 6
| --
| --
| |
|
|
-513
| 6.0
| 5
| 5
| 5
|
| 168
| 7
| --
| --
| |
|
|
-499
| 6.1
| 5
| 5
| 5
|
| 192
| 8
| --
| --
| |
|
|
-484
| 6.1
| 4.6
| 4.6
| 4.6
|
It will
be
noted that the pH of
the fresh raw juice is mildly acidic, falling in the pH range of 5.5 to
6.0. This is to be expected (it is often even far more acidic with fresh raw
fruit
juices) and is simply due to the presence of various plant
acids. It
will also be noted that the pH of the MegaH-treated batch was slightly
higher
than that of the control batch: this is due to the mildly-alkaline
pH-buffering
action of MegaH.
It will further be
noticed that the pH of periodic samples from both batches, after
stabilization, show a mild trend over time to increase. This
increase is usually due to long-term slow changes in chemical
equilibrium in the juice while in storage, and
also to the slow but constant action of decay microorganisms as they
digest
juice components and thus slightly shift the acid-alkaline balance.
Conclusions
From
the
results observed here, which are in harmony with earlier studies done
at this laboratory, it appears that the rate of oxidative degradation
of the untreated fresh raw juice (control batch) was relatively minimal
over the first 3 days, and that the juice
could be expected to have retained a large percentage of nutrient
quality
over the first 3.5 days (this is also in harmony with information
received
from other researchers and nutritional consultants). The
degree of
degradation was especially minimal over the first two days. It is the
opinion of the current author that the untreated raw juice still
retains
a very large percentage of nutrient quality after 3.5 days. Further,
all secondary measures (smell, taste, appearance) still rated a score
of
"5" on a scale of 1 to 5 after 3.5 days.
The
treated
juice, which started at an ORP of -590, ended up at -529 after 3.5
days, and -499 after 7 days. In the opinion of this author,
this indicates that almost all of the nutrients in the juice were still
intact at both 3.5 days and 7 days. Further, all secondary
measures (smell, taste, appearance) still rated a score of
"5" on a scale of 1 to 5 after 3.5 days and after 7 days. Minor
degradation of taste and smell was noted in this batch after 8
days; this was likely
due to slow and steady bacterial action, resulting in decomposition and
slight "fermentation". This is not necessarily harmful.
From
the
experimental results observed here for the MH-treated batch (the
experimental batch), the degree of apparent oxidative damage to the
treated juice after even 7 days appeared to be extremely
minimal. Note that after even 8 days the ORP remained in a
strongly reduced range of -485. It is the opinion of the
current author that the treated juice still retains a very large
percentage of nutrient quality after 6 days. However, after
observing the relatively strongly-reducing environment as shown by ORP
in the -520 range, the author believes that for day-to-day preservation
of raw juices, an amount of MH equivalent to only 1/4 that amount of MH
used may be needed in order to yield a strong level of antioxidant
protection for the juice. A rate 1/4 of the present amount
would be 250 mg MH (1 capsule equiv.) per 4 liters (~ 1 gallon) of
juice,
or 63 mg per liter (~ 1 quart). Subsequent trials have shown
that even
an amount 1/4 the amount used in this study appear to be fully adequate
to
protect the juice from oxidative damage over 7 days, yielding
a starting
ORP in the range of -290 or lower.
*Vinny Pinto,
MA, Enhanced Vitality Research.Notes:
study performed in
mid-March, 2001. Nominal
refrigeration storage temperature was 39 degrees F, with an average
deviation
of +/- 2 degrees or less.
All ORP
and pH
measurements were performed with
a laboratory-grade microprocessor-controlled instrument with separate
electrodes
for measurement of ORP and pH, and all measurements were checked with a
second
laboratory-grade instrument for accuracy. All ORP electrodes
were rinsed
after each use in cold water, then soaked for 10 min. in an acidic,
oxidizing
water solution (pH = 2.4; ORP = +1,150) to clean the electrodes and
reverse
any ion penetration/degradation of electrode shell, followed by rinsing
in
cold water prior to storage. Failure to clean electrodes will
result
in progressive degradation of ORP electrode, resulting in regression of
ORP readings toward a low positive range (~ +300).
Decanting
of liquid from
the control and experimental batch bottles for periodic measurement
resulted in steady lowering of liquid surface below bottle cap,
resulting in increasing headspace in container above
liquid surface which would have been normally occupied by ambient room
air
containing 20% - 21% O2, offering the
potential of accelerated
oxidative degradation over liquid stored in a filled bottle with little
or
no (3 mm or less) headspace allowing accumulation of air. Thus, to
reduce this exposure to O2 in the headspace, all
headspace (dead
air space) above the liquid in storage containers was flushed with an inert
gas
after each opening/decanting and prior to subsequent return to
refrigerated
storage. The inert gas used for flushing and
filling headspace
in the container was helium gas (He, 99.997% tech. grade), yielding a
measured
O2 concentration of < 1% in
headspace after flushing/filling,
as measured with an oxygen probe in test trials conducted prior to this
study.
Storage
containers were
NALGENE (TM) brand wide-mouth
food-quality thick-wall HDPE storage containers with screw caps,
with nominal 500 ml (1 pint) capacity and an actual capacity of ~570
ml. These
containers are commonly available via scientific catalogs and in many
camping
and sporting goods stores, sold as leakproof, heavy-duty bottles for
storage of liquids in rough environments.
The
thick-wall HDPE
containers and thick screw
caps, which form an airtight and sturdy seal, offer an impermeability
to
moisture and oxygen only slightly less than that of a glass container
of
similar capacity and dimensions while offering far less vulnerability
to
breakage and/or leakage.
MegaHydrin
™, MegaH™
and MegaH-™ are registered trademarks owned by Flantech Group.
Nalgene® is
a registered trademark owned by Nalge Nunc International.