Here it is!
This has certainly been quite a project. Good thing I like vegetables!
I?ve tried to first, sum things up for you, and then present you with
the data to support the summary. However, not every point is reflected
in the data. For example, I found a generic reference to "water
soluble vitamins" degrading over time, but little research having to
do with the B vitamins specifically.
I?m confident that overall you?ll find it to be a good argument for your case.
REASONS FRESH VEGETABLES ARE MORE NUTRITIOUS THAN STORE-BOUGHT
From the moment they are harvested, plant matter begins to undergo
senescence -- a genetically regulated process which leads to the death
of cells, organs, or whole organisms.
In plants, senescence is accompanied by structural changes and/or
changes in biochemical and biophysical metabolic properties. This may
involve degradation of proteins, chlorophyll and nucleic acids.
This cell breakdown causes vegetables to cease forming nutritive
chemicals. As a result, they begin to lose nutrients in the form of
water soluble vitamins (B & C), antioxidants, and protein.
For this reason, time from field to consumer and the care of the crop
in between, are the defining variables that differentiate the
nutritive value of farm-fresh vegetables from those bought from
Also, any type of processing, even minimal, including cutting, slicing
or trimming increases the rate at which vegetables undergo nutritional
and quality deterioration.
Additionally, the more hands (and processes) they pass through on
their way to the consumer, the more likely they are to pick up
contamination such as bacteria.
Finally, because vegetables going to market must be picked earlier in
their development cycle than farm-fresh vegetables, many are harvested
before they achieve maximum nutrient capacity.
Time from Field to Consumer: 5 -14 days
During that time, the following occurs:
1. Vitamin C (ascorbic acid / ascorbate) degrades*
2. Degradation B vitamins
.....B5 /pantothenic acid;
.....B6 / pyridoxine
.....B9 / Folate and folic acid (2 forms of B9)
3. Loss of Antioxidants --
.....Monoterpenes: limonene, carvone, carveol;
.....Tetraterpenes: carotenoids like alpha- and beta-carotene,
lutein, lycopene zeaxanthine, cryptoxanthine
Also mentioned: Glucoraphanin, the glucosinolate precursor
of anticancer isothiocyanate sulforaphane
4. Decrease in protein
5. Potential for human contamination via packaging and handling
6. Increase in some natural toxins
(eg: synthesis of glycoalkaloids in potatoes)
Tomatoes and red sweet peppers picked unripe, increase vitamin A as
they ripen off the vine, but decrease in Vitamin C.
PEER REVIEWED PUBLISHED RESEARCH
Only the first study below actually compares nutrients between farm
fresh and simulated commercial storage and transport.
Most illustrate the breakdown of specific nutrients in specific
vegetables over time. However, the thing to remember is that every
time they refer to storage or processing, the researchers have to
start with a baseline control ? that is *fresh-picked* produce. They
can?t begin with a product that has already been transported and
stored for several days. The results would be meaningless.
For example, I?ve been to the USDA research farms in Beltsville
Maryland. They have acres of fields and miles of greenhouses where
they maintain these crops for testing purposes.
So, in reality, to be valid, all of these studies should be comparing
?fresh? produce to that which has been stored, transported, or
otherwise processed as it would be for retail sale.
"Total aliphatic and indole glucosinolates, phenolic compounds
(flavonoids and hydroxycinnamoyl derivatives), and vitamin C contents
were evaluated in freshly harvested broccoli (Brassica oleracea L.,
var. italica, cv. Marathon) inflorescences. These were film-wrapped
and stored for 7 days at 1 degrees C to simulate a maximum period of
commercial transport and distribution.
"Results showed major losses at the end of both periods, in comparison
with broccoli at harvest. Thus, the respective losses, at the end of
cold storage and retail periods, were 71-80% of total glucosinolates,
62-59% of total flavonoids, 51-44% of sinapic acid derivatives, and
73-74% caffeoyl-quinic acid derivatives. Slight differences in all
compound concentrations between storage and retail sale periods were
detected. Distribution and retail periods had minimal effects on
HEALTH-PROMOTING COMPOUNDS IN BROCCOLI AS INFLUENCED BY REFRIGERATED
TRANSPORT AND RETAIL SALE PERIOD.
Vallejo F, Tomas-Barberan F, Garcia-Viguera C.
Laboratorio de Fitoquimica, Departamento de Ciencia y Tecnologia de
los Alimentos, CEBAS-CSIC, P.O. Box 4195, E-30080 Murcia, Spain.
PURCHASE - $25
"Being highly unsaturated, carotenoids are susceptible to
isomerization and oxidation during processing and storage of foods.
Isomerization of trans-carotenoids to cis-carotenoids, promoted by
contact with acids, heat treatment and exposure to light, diminishes
the color and the vitamin A activity of carotenoids."
CHANGES IN CAROTENOIDS DURING PROCESSING AND STORAGE OF FOODS.
Arch Latinoam Nutr. 1999 Sep;49(3 Suppl 1):38S-47S.
"The present study investigated whether storage under
modified-atmosphere packaging (MAP) affected the antioxidant
properties of fresh lettuce (Lactuca sativa)...
"Eleven healthy volunteers (six men, five women) consumed 250 g fresh
lettuce, and blood was sampled before (0 h) and 2, 3 and 6 h after
"The protocol was repeated 3 d later with the same lettuce stored at
5°C under MAP conditions (O2?N2 (5:95, v/v))...
"Results showed that after ingestion of fresh lettuce, plasma total
radical-trapping antioxidant potential (TRAP), measured as area under
the curve, was significantly higher ?. THAN THE VALUE OBTAINED WITH
EFFECT OF ACUTE INGESTION OF FRESH AND STORED LETTUCE LACTUCA SATIVA)
ON PLASMA TOTAL ANTIOXIDANT CAPACITY AND ANTIOXIDANT LEVELS IN HUMAN
British Journal of Nutrition, December 2002, vol. 88, no. 6, pp. 615-623(9)
[Full text for purchase. $16.36 ]
"Beta-carotene acts as a pro-vitamin A or anti-cancer compound.
Carrots contain the highest amount of beta-carotene of common fruits
and vegetables, but each year 25% of carrot production is lost in the
U.S. during processing and storage...
"...This article is a review of the most recent studies concerning
beta-carotene retention in carrots during processing and storage.
"...The trans form of beta-carotene in carrots is replaced by the cis
form during processing. Beta-Carotene can be extracted from carrots,
but the half-life of free beta-carotene is reduced to 2 d in the juice
extract at room temperature..."
Crit Rev Food Sci Nutr. 1998 Jul;38(5):381-96
PRESERVATION OF BETA-CAROTENE FROM CARROTS.
Desobry SA, Netto FM, Labuza TP.
"Fresh Lima beans were subjected to various combinations of handling
factors, including storage time and temperature, air during storage,
water during preparation, hulling, and preparation method, to
determine their effects on ascorbic acid, thiamin, and carotene
Longer storage time and higher storage temperature resulted in
significant reduction in ascorbic acid. Bruising, such as that
occurring when beans are mechanically hulled, caused significant
losses of both carotene and ascorbic acid."
J Am Diet Assoc. 1976 Dec;69(6):640-4
EFFECTS OF STORAGE AND HANDLING ON VITAMINS IN FRESH LIMA BEANS.
Head MK, Giesbrecht FG.
"...the effect of traditional processing practices on the retention of
ascorbic acid, riboflavin and thiamine were studied using amaranth,
cowpea, peanut, pumpkin and sweetpotato leaves
"...sun/shade drying and storing in ventilated containers resulted in
a significant?decrease in ascorbic acid, riboflavin and thiamine for
J Am Diet Assoc. 1976 Dec;69(6):640-4
EFFECTS OF STORAGE AND HANDLING ON VITAMINS IN FRESH LIMA BEANS.
Head MK, Giesbrecht FG.
"The effects of post-harvest and packaging treatments on glucoraphanin
(4-methylsulfinylbutyl glucosinolate), the glucosinolate precursor of
anticancer isothiocyanate sulforaphane [4-methylsulfinylbutyl
isothiocyanate], were examined in broccoli (Brassica oleracea var.
italica) during storage times. The results showed that at 20 degrees
C, 55% loss of glucoraphanin concentration occurred in broccoli stored
in open boxes during the first 3 days of the treatment and 56% loss
was found in broccoli stored in plastic bags by day 7."
THE EFFECT OF POST-HARVEST AND PACKAGING TREATMENTS ON GLUCORAPHANIN
CONCENTRATION IN BROCCOLI (BRASSICA OLERACEA VAR. ITALICA).
Rangkadilok N, Tomkins B, Nicolas ME, Premier RR, Bennett RN, Eagling
DR, Taylor PW.
ARTICLE [48 hr web access - $25]
"The effect of modified atmosphere packaging (MAP) and cooking on the
flavonoids and vitamin C content (ascorbic + dehydroascorbic acid; AA
+ DHAA) of fresh-cut spinach was evaluated...
"A decrease in the total antioxidant activity was observed during
storage, particularly important in MAP-stored spinach."
EFFECT OF POSTHARVEST STORAGE AND PROCESSING ON THE ANTIOXIDANT
CONSTITUENTS (FLAVONOIDS AND VITAMIN C) OF FRESH-CUT SPINACH.
Gil MI, Ferreres F, Tomas-Barberan FA.
"...The ascorbate content declined rapidly in broccoli (Brassica
oleracea L. var. italica) florets, but not in the stem tissue, during
post-harvest senescence...it was observed that mRNA levels of
chloroplastic APX, BO-sAPX and BO-tbAPX, had decreased by 12 h after
harvest in broccoli florets, suggesting that the active oxygen species
(AOS) scavenging system in chloroplasts was largely abolished in
florets during the early hours of the post-harvest period."
ASCORBATE METABOLISM IN HARVESTED BROCCOLI
Received 7 July 2003; Accepted 21 July 2003
Fumie Nishikawa*,1, Masaya Kato3, Hiroshi Hyodo2, Yoshinori Ikoma3,
Minoru Sugiura3 and Masamichi Yano3
[Full text available - 24 hours for US $19.00.]
Harvest-induced senescence of broccoli results in tissue wilting and
sepal chlorosis. As senescence progresses, chlorophyll and protein
levels in floret tissues decline and endo-protease activity (measured
with azo-casein) increases
IDENTIFICATION OF DEHYDRATION-RESPONSIVE CYSTEINE PROTEASES DURING
POST-HARVEST SENESCENCE OF BROCCOLI FLORETS
Simon A. Coupe2,, Ben K. Sinclair, Lyn M. Watson, Julian A. Heyes and
Jocelyn R. Eason3,
[Full text available - 24 hours for US $19.00.]
* I?m not clear on whether or not this study began with fresh produce.
"The objective of this work was to conduct a systematic, comparative
kinetic study of Vitamin C deterioration for four different frozen
green vegetables, in the whole temperature range occuring in the real
distribution chain of frozen foods.
In all cases, Vitamin C loss followed apparent first order kinetics.
Spinach showed a significantly faster nutritional degradation at all
temperatures (50% loss in 2 months at -15oC), followed by green beans
and green peas, whereas, in okra, Vitamin C was well retained."
COMPARATIVE KINETIC STUDY AND EVALUATION OF NUTRIENT DEGRADATION
DURING DISTRIBUTION AND STORAGE OF FOUR FROZEN GREEN VEGETABLES
"Fresh peppers (Capsicum annuum L., variety California) in their green
and red ripe stages were stored at 20 degrees C for 7 and 19 days to
determine the effects of storage on whole fruit antioxidant capacity
(TAA) and ascorbate (ASC) content, as well as on some antioxidant
enzyme activities, such as catalase (CAT), superoxide dismutase (SOD),
and those of the ASC-glutathione cycle.
"...TAA, as well as the ASC content, was higher in red peppers than in
green, and storage increased the ASC in both green and red fruits."
ANTIOXIDANT SYSTEMS AND THEIR RELATIONSHIP WITH THE RESPONSE OF PEPPER
FRUITS TO STORAGE AT 20 DEGREES C.
Jimenez A, Romojaro F, Gomez JM, Llanos MR, Sevilla F.
"...Concentrations of total ascorbate dropped significantly in spinach
leaves following detachment, regardless of the storage atmosphere"
THE EFFECTS OF ETHYLENE, DEPRESSED OXYGEN AND ELEVATED CARBON DIOXIDE
ON ANTIOXIDANT PROFILES OF SENESCING SPINACH LEAVES
D. Mark Hodges1 and Charles F. Forney
Atlantic Food and Horticulture Research Centre, Agriculture and
Agri-Food Canada, 32 Main Street, Kentville, Nova Scotia, B4N 1J5
NATURAL TOXIN ISSUES
"Potatoes contain antinutritional and potentially toxic compounds ??
In this overview, we describe ?reported changes in glycoalkaloid
content of fresh and processed potatoes during storage, ?. Reducing
the glycoalkaloid content of potatoes will provide a variety of
benefits extending from the farm to processing, shipping, marketing,
and consumption of potatoes and potato products."
POSTHARVEST CHANGES IN GLYCOALKALOID CONTENT OF POTATOES.
Friedman M, McDonald GM.
Western Regional Research Center, U.S. Department of Agriculture,
Albany, California 94710, USA.
FOOD CONTAMINATION ISSUES
Locally produced farm-fresh vegetables may be safer (and thus more
nutritious) than store-bought vegetables, since *some* food-borne
pathogens originate in internationally grown crops.
The FDA states:
"...recently, it has been associated epidemiologically in the USA and
Canada with foodborne outbreaks. Items of fresh produce, mostly
imported, appear to be the vehicles - mesclun lettuce, basil, and
Also, the FDA notes some of the primary barriers to achieving their
?Healthy People 2000? objectives include:
"The increasing proportion of food imported from other countries.?
"The introduction of new food processing and packaging technologies.
For example, the use of modified atmosphere to prolong the shelf-life
and maintain the quality of vegetables may enable anaerobic organisms,
including human pathogens, to proliferate."
"The difficulty of convincing food workers that they need to be
concerned about food safety. A study of convenience store managers and
employees in Michigan showed that they tend to overestimate their
knowledge. Actual sanitary conditions in stores were closely
associated with actual knowledge."
"The difficulty of motivating all those who prepare food to follow
proper food preparation practices."
HEALTHY PEOPLE 2000: STATUS REPORT
FOOD SAFETY OBJECTIVES
FDA: Guide to Minimize Microbial Food Safety Hazards for Fresh Fruits
This I?m not sure is useful, but will leave it in and you can decide.
The following studies illustrate the danger of Hepatitis A virus being
transmitted from food handlers to consumers. Naturally, the more food
handlers involved in the processing of vegetables, the higher the
likelihood of contamination.
However, I haven?t been able to confirm where in the handling process
contamination takes place. It may in fact be at the farm. And, I
haven?t confirmed whether grocery store produce is an issue, or
whether the concern is more with restaurants. This may be a whole
other research project, but wanted to at least let you know about it.
THE SURVIVAL OF HEPATITIS A VIRUS IN FRESH PRODUCE.
Croci L, De Medici D, Scalfaro C, Fiore A, Toti L.
Applied and Environmental Microbiology, July 2000, p. 2759-2763, Vol. 66, No. 7
CONTAMINATION OF FOODS BY FOOD HANDLERS: EXPERIMENTS ON HEPATITIS A
VIRUS TRANSFER TO FOOD AND ITS INTERRUPTION
S. Bidawid,1,* J. M. Farber,1 and S. A. Sattar2
Not necessarily referenced or peer reviewed, but most from reputable sources.
"While the fat soluble vitamin content of food tends to be quite
stable and resists degradation, water soluble vitamins are fragile and
easily destroyed by lengthy storage, high temperatures, processing,
"Fruits and vegetables contain their highest level of nutrients when
they are harvested at full ripeness and eaten soon thereafter, with
only minimal processing. Thus, the most nutritious produce consists of
homegrown fruits and vegetables picked at full maturity (avoid picking
prematurely and allowing them to ripen off the vine) and eaten
"Fresh" supermarket produce does not always fit this description as it
is often picked before fully ripe, shipped long distances, and stored
under poor conditions.
"A cool, dark place is generally best since vitamin degradation
accelerates at higher temperatures and several of the water soluble
vitamins, riboflavin and vitamin C in particular, are very light
COLUMBIA UNIVERSITY COLLEGE OF PHYSICIANS & SURGEONS
MEDICAL GUIDE: The Basics of Good Nutrition - Vitamins
Postharvest Issues for Protected Agriculture Production
Postharvest Handling and Monitoring of Quality for Vegetables Produced
in Greenhouses in Hot, Arid Climates
Wilfried H. Schnitzler
Institute for Vegetable Science, Technische Universit ät München, Freising, Germany
"Postharvest losses include physiological changes and vitamin C
degradation of vegetables; these may be affected by postharvest
temperature and respiration rate. ?. Respiration rate is a good index
of the potential postharvest life of a vegetable since it increases
with the rate of deterioration.
"...Temperature, relative humidity, gases, micro-organisms and insects
are the most important environmental factors that affect water loss
POSTHARVEST HANDLING AND MONITORING OF QUALITY FOR VEGETABLES PRODUCED
IN GREENHOUSES IN HOT, ARID CLIMATES
"Qualitative losses include losses in (a) edibility, (b) nutritional
quality, (c) caloric value, and (d) consumer acceptability of
.... The rate of biological deterioration depends on various
environmental (external) factors including temperature, relative
humidity, air velocity, and concentrations of ethylene, oxygen, and
POSTHARVEST LOSSES OF HORTICULTURAL PERISHABLES
"...Much of the green produce available in the supermarket or
greengrocers is far from fresh. It is not uncommon for produce, after
harvesting, to spend several days being sorted and packaged. Once
placed in a refrigerated truck, the hapless vegetable may spend
several more days on a journey to a distribution centre, where yet
more time may be spent stored in a refrigerator. When it finally makes
its way through a supermarket checkout, the ?fresh? vegetable or fruit
may have spent a week or more in storage from the time it was picked.
Cold storage, fluctuations in light and temperature, and display
beneath supermarket lights, each cause degradation and breakdown of
"...Tests show that green beans, for example, lose 40 percent of their
vitamin C content in the first two days after harvesting, and within
three days of harvesting, a whopping 58 percent of vitamin C has gone.
Often foods are harvested before they are fully ripe, with the
expectation that further ripening will occur after harvest."
FRESH, FROZEN OR CANNED?
By: Lynda Wharton
This website discusses many of the major vegetable crops, and while
not giving specific nutrient information, does discuss the loss of
some nutrients in some vegetables as a result of improper storage over
time. I?ve provided some sample excerpts below.
OREGON STATE UNIV. Commercial Vegetable Production Guides
"...Fresh asparagus is highly perishable and deteriorates rapidly at
temperatures above 40 F. ? In addition to general deterioration, spear
growth, loss of tenderness, loss of flavor, loss of vitamin C, and
development of decay take place at moderately high temperatures."
ASPARAGUS - ASPARAGUS OFFICINALIS
"Research has shown that kale packed in polyethylene-lined crates and
protected by crushed ice keeps in excellent condition for 3 weeks at
32 F but only 1 week at 40 F and 3 days at 50 F. Vitamin content and
quality are retained better when wilting is prevented."
"...Broccoli is highly perishable, and it is usually stored for only a
brief period as needed for orderly marketing. Broccoli should be
hydrocooled or packed in ice immediately after harvest and kept at 32
F to maintain good salable condition, fresh green color, and vitamin C
content. ? The respiration rate of freshly harvested broccoli is very
high - comparable to that of asparagus, spinach, or sweet corn."
This Q & A illustrates the increase in Vitamin A and the decrease in
Vitamin C in tomatoes as they ripen from green to red.
"Q: At what stage of development does fruit contain the most nutrients??
"I found no specific information on the rate of degradation of
nutrients in tomato or peach, but in general, the fresher the better.
However a couple of points should be mentioned..."
"...some specifics for red and green tomato provided by the
Cooperative Extension Service (at the Univ. of Rhode Island). Their
source was: Pennington, J.A.T. (1989). Food values of portions
Vitamin A (IU) 789 1394
Vitamin C (mg) 29 22
Vitamin B1 (mg) 0.07 0.07
AT WHAT STAGE OF DEVELOPMENT DOES FRUIT CONTAIN THE MOST NUTRIENTS?
This very long in-depth FAO report contains a wealth of information on
post harvest losses in vegetables. While they make reference to
vitamin and other nutrient losses, I found no specific data. However,
I?ve pulled a couple of relevant quotes for you here --
CHAPTER 1. FRUITS AND VEGETABLES: AN OVERVIEW ON SOCIO-ECONOMICAL AND
"Physiological deterioration of fruits and vegetables refers to the
aging of products during storage due to natural reactions.
Deterioration caused by biochemical or chemical agents refers to
reactions, of which intermediate and final products are undesirable.
These can result in significant loss of nutritional value.."
CHAPTER 3. GENERAL CONSIDERATIONS FOR PRESERVATION OF FRUITS AND VEGETABLES
"...Because MP [minimally processed ] refrigerated products can be
raw, the cells of the vegetative tissue may be alive and respiring (as
in fruits and vegetables), and biochemical reactions can take place
that lead to rapid senescence and/or quality changes. ? in most cases,
minimally processed foods are more perishable than the unprocessed raw
materials from which they are made."
HANDLING AND PRESERVATION OF FRUITS AND VEGETABLES BY COMBINED METHODS
FOR RURAL AREAS
FAO Agricultural Services Bulletin 149
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
I?ve contacted the following organizations and individuals, but have
received no information from them.
So that you may follow up, here?s the info for you.
Email sent to USDA:
Rena Cutrufelli email@example.com
She forwarded it to ?vegetable specialist?:
These folks have a number of post-harvest specialists. Since some have
no email, I sent my request to general delivery--
UC DAVIS - DEPARTMENT OF VEGETABLE CROPS AND WEED SCIENCE PROGRAM
University of California, Davis
One Shields Ave.
Davis, CA 95616
General Info Email: firstname.lastname@example.org
Received reply today:
"I am forwarding your request to the Postharvest Research and
Information Center. You should also check the following web site:
Check the "documents" page."
Mary E. (Kitty) Schlosser
Vegetable Research & Information Center
University of California
One Shields Ave.
Davis, CA 95616
So, that?s what I?ve done. I?m going to leave you to digest everything
I?ve given you. I understand it may take awhile, that?s fine. Let me
know if you need clarification of any of the points.
As I said, this has been a huge undertaking, but I?ve sure learned a
lot. Kind of makes me look at that store-bought broccoli and those
pre-peeled carrots and wonder why I even bother ? maybe we should
arrange with the editors for me to be paid in produce. ;-) I?ve got
a craving for a good fresh salad right about now!
Let me know if you need anything ?
where to begin? :-)
I pretty much just worked PubMed to death. I didn?t think to save all
of my searches from there, but this is a partial sampling of a couple
hour?s work. The last number in the column refers to the number of
returns for the search that I then worked through.
#18 Search "farm to fork" 18:45:12 16
#12 Search vegetable contamination bacteria 18:41:19 253
#10 Search vegetable contamination 18:37:18 1573
#9 Search farm vegetable HAV 18:12:06 1
#6 Search virus vegetable HAV 18:10:57 9
#3 Search virus vegetables HAV
#34 Search spinach storage 18:55:53 57
#33 Search riboflavin spinach storage 18:55:48 0
#31 Search riboflavin degradation spinach 18:54:33 47
#30 Search riboflavin degradation vegetable 18:54:16 95
#26 Search thiamine degradation vegetable 18:52:20 55
#25 Search thiamine degradation 18:51:35 5475
#23 Search thiamine vegetable 18:50:09 119
#22 Search thiamine breakdown vegetable
#43 Search "farm gate" 17:16:09 11
#41 Search "harvest induced" 17:11:44 7
#40 Search "field to consumer" 17:11:15 0
#39 Search "farm to consumer" 17:10:48 133
#38 Search "ascorbate metabolism" vegetable storage 17:09:51 8
#35 Search "ascorbate metabolism" vegetables 17:08:31 200
#34 Search "ascorbate metabolism" 17:08:08 6634
#32 Search ascorbate metabolism 17:04:17 6634
#17 Search "post harvest" 17:03:27 200
#16 Search "post harvest" nutrient 14:43:21 2
#14 Search "field to consumer" nutrient 14:43:04 0
#13 Search "field to store" nutrient 14:42:58 0
#12 Search "farm to store" nutrient 14:42:51 0
#6 Search "fresh vegetables" 14:38:54 169
#2 Search "fresh cabbage" 14:37:53 104
#1 Search "fresh carrots"