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
-596
5.9
5
5
48
2
+128
5.7
5
-545
5.9
5
5
84
3.5
+156 
5.8
5
-534
5.8
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
120
5
-- 
-- 
     
-522
5.9
144
6
 --
 --
     
-513
6.0
168
7
 --
-- 
     
-499
6.1
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 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 rinse 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 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 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 widemouth food-quality thick-wall HDPE storage containers with screw caps, with  nominal 500 ml (1 pint) capacity and 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. 


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