Summary and Overview:
Extraction and
Storage of Raw
Juices While Retaining
Nutrient Quality
by Vinny
Pinto, MA*
Introduction
This
document will provide an overview and summary of what we currently know
about juicing of fresh raw vegetable juices and storage of these juices
under refrigeration, in light of concerns about possible degradation of
nutrient quality. Some hints and opinions will be provided
regarding which type of juicer to use, how to best store juice under
refrigeration and how long it seems to last before serious degradation
of nutrients occurs.
Background
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 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 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.
Some
Guidelines on Juicing
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 accelerate ROS processes, and therefore,
degradation. Regarding
consumer juicers, the consensus, along with some good anecdotal
evidence,
seems to strongly indicate 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 twin-gear juicers (such as the Green Life and the Angel) seem to
produce
the least heating and least exposure to oxygen, yielding the highest
quality
juices. When the current author switched from a masticating
juicer
to a Green Life twin-gear juicer in late 2000 at the urging of Aaonus
Vonderplanitz
and several long-time RVAFers, he noticed a significant improvement in
the
quality of the juice.
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; such oxidation,
when severe, often yields a brownish color in the juice
- 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, Aajonus Vonderplanitz
has done studies which have shown that after 78 hours (3 days and 6
hours) the nutrients in the juice from a Green Life juicer still
retained at least 82% of their original potency.
Therefore, many
"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 (see below) 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), including this author, have been adding small amounts of
a
proprietary hydride (H-) donor antioxidant (MegaH™ aka MegaH-™) to
the raw juice before storage to decrease oxidative damage over time and
to
increase useful storage lifetime of the juice. This paper
will address
that as well. Further
guidelines, regarding storage
of juice, will appear below.
Introduction
to Some Laboratory
Studies and Trials
The current
author performed several
preliminary trial studies in late 2000 and early 2001 regarding quality
of
raw juice under storage, and completed a longer study in early 2001 to
measure
oxidative degradation over time of refrigerated fresh raw vegetable
juice
from a Green Life juicer, and also to look at the difference in
degradation
between untreated raw juice and juice (from the same source batch)
which
had been treated with
an earlier version of a product
currently marketed as MegaH® (aka
MegaH-). The
results of the longer study are presented in detailed format
(but in "technicalese" rather than plain
English!) on another page on this site. However, as indicated
above,
the results of that study and other trials are presented in this paper
(on
this page) in simpler summary format. 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 the 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 acidic 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.
The longer
and detailed study described above used two test batches of organic raw
green juice from a twin-gear juicer,
each drawn from the same well-mixed source batch and strained (to
remove
particles). One test batch was untreated raw juice, while the
other
batch, labeled the control batch, was treated by adding 250 mg (1
capsule
equiv.) of (an early form of) MegaH per quart as a
prophylactic
antioxidant. 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
|
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.)
Since about
1.5 ounces of juice
was to be drawn from each bottle at each test period, it is obvious
that
the level of the juice in the bottles would steadily decrease, thus
increasing
the amount of "headspace" and thus dead air, above the juice. 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. Therefore,
as the juice level in each test bottle declined, the headspace (dead
air
space) above the juice was flushed and filled with an inert gas (helium
gas)
prior to sealing the bottle (this reduced the amount of oxygen in the
headspace
to less than 1%.)
Brief
Summary of Study Findings
As stated
above, if you wish to
see the detailed longer study, please
go to that page, although it is written more in "technicalese" than is this page.
Briefly,
here is what was found:
Both batches
of juice started with
an ORP of +090. After MegaH™ (aka MegaH-™) was added to the
control batch, the ORP (after 3
minutes)
read -590.
The
untreated juice showed relatively
modest oxidation over the first 3.5 days, yielding a final ORP of about
+156
after 3.5 days. In the opinion of this author, this indicates that most
of
the nutrients in the juice were still intact. 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.
Due to
the
incredibly strong reducing
effect in the treated juice after even 7 days, the author has decided
that
far less MegaH may be used, and subsequent trials have shown that just
250
mg per gallon (or an amount 1/4 of that used in the study) is all that
is needed
to bring the juice to an initial ORP in the -290 range and keep it
below
-200 over 7 days, which is more than adequate protection for the
juice. It should be noted that the current author often makes 1.5 to 1.8
gallons
of raw juice at once and stores it for up to 7 days in the refrigerator
prior
to use.
Some
Guidelines on Juice
Storage
Based
upon the trials and
studies described above, and upon general current knowledge, here are
recommendations for storing fresh raw vegetable juice beyond the time
of juicing:
- When
juicing, use a twin-gear juicer only, or a twin-gear juicer followed by
a Norwalk press only.
-
When
juicing for storage, try to use only fresh organic
vegetables. Studies show that these usually start out with
higher levels of antioxidants, as well as higher levels of minerals and
other nutrients.
-
Immediately
after juicing, the juice must
be decanted into small bottles and then immediately
refrigerated. If
storing more than 4 bottles in the refrigerator at once, consider
placing
a few refrigerant gel packs from the freezer near them to speed the
chilling process.
-
The
juice must be stored in thick-walled
plastic HDPE bottles or glass bottles, each with tight-fitting,
air-tight,
screw-cap seals.
-
The
best plastic storage containers seem
to be wide-mouth 8 and 16 ounce Nalgene containers (they usually are
milky in color) with screw caps (usually blue) which fit
tightly. These containers
are sold in sporting goods stores for carrying water for camping; these
containers
have thick HDPE walls, and the screw caps fit tightly, forming an
airtight
seal.
- The
best glass storage containers seem
to be those usually recommended by Aajonus Vonderplanitz -- 8-ounce and
16-ounce glass "jelly" canning jars made by Ball, with tight-fitting
metal screw lids.
-
Thin-wall
plastic containers such as those in which fruit smoothies are sold, or
the the thin plastic jugs in which milk
is sold, are unusable due to the thin plastic walls, which allow
too-rapid
an incursion of oxygen as well as too-rapid an escape of the primary
antioxidants
(H- ions and the H2 breakdown products), as well as the fact that the
caps
allow some air incursion as well.
- The
bottles must be filled all the way
to the top, leaving little or no airspace at the top.
- The
size of the bottle or container must
be small enough that once it is opened and some contents used, the
remainder of the contents must be used within 8 hours to prevent
oxidative damage. Thus, for most users, 8 ounce or 16 ounce
containers or bottles will be needed. Do not use large containers, as the airspace above the juice, as the
container
is slowly emptied over time, will allow rapid degradation of juice due
to
presence of oxygen in the air as well as other factors.
- Again,
it bears repeating: DO NOT use
thin-walled containers such as those in which milk is sold in stores,
or
in which carrot juice and smoothies are sold in natural foods
stores. DO NOT use large containers. DO NOT leave airspace over juice
of more
than 1 to 3 mm.
-
If
you will be storing the juice for 3.5
days or less (and you started with organic vegetables and used a
twin-gear
juicer), then it appears that you can safely store the juice as-is,
without
any added antioxidants, although it appears the addition of MegaH™ (aka MegaH-™) as
an antioxidant will help further improve quality.
- If
you plan on storing the juice for longer than 3.5 days, or have used
non-organic vegetables, or wish even fresher juice
quality, then this author recommends use of
MegaH™ (aka MegaH-™)
as
an antioxidant at the rate of 250 mg (1 capsule equiv.) per gallon,
well-mixed into the bulk container or pitcher before decanting into
bottles. This
should extend the useful life of the juice to at least 7 days from the time
of
juicing.
Final
Notes
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.
Note: 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.
Final
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. The degree of degradation was especially
minimal
over the first two days. It is the opinion of the current
author that
the juice still retains a very large percentage of nutrient quality
after
3.5 days.
From the
experimental results observed here for the MegaH-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 MegaH equivalent to
only
1/4 the amount of MegaH 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 MegaH (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, yielding a
starting
ORP in the range of -290.
*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.