> suppliers in California, I am told, have made the decision to change
> packaging. This seems to be in keeping the national TV campaign by
> ziplock type plastic bag manufacturers to convince consumers that
> salad ingredients at home should be stored in airtight bags to promote
> freshness and allow consumers to keep vegetables longer.
> I am aware of the Chinese debacle a few years back when they packaged
> mushrooms in airtight containers and discovered that the mushrooms
> continued to respire for a time after packaging. An anaerobic
> environment was created and botulism was the result.
People should be aware that different kinds of plastic films differ
greatly in oxygen permeability. Botulinum requires very low oxygen to
grow. This, along with the whole issue of ethylene and senescence,
makes this subject a lot more complicated than it appears.
Manufacturers of packaging know a lot about these things and should be
> problem being courted by sprout producers/supermarkets and/or ziplock
> bag manufacturers? If the mushroom model applies, a real problem may
> be brewing in the USA. Or, are sprouts radically different than
Sprouts tend to have problems with aerobic organisms that grow on seed
exudates during production.
PS. Here are a couple relevant abstracts:
U: Varoquaux,-P.; Albagnac,-G.; The,-C.N.; Varoquaux,-F.
TI: Modified atmosphere packaging of fresh beansprouts.
SO: J-sci-food-agric. Sussex : John Wiley & Sons Limited. Feb 1996.
v. 70 (2) p. 224-230.
CN: DNAL 382-So12
AB: Freshly harvested beansprouts displayed a respiration rate of
about 1 mmol O2 kg-1 h-1 at 10 degrees C which was strongly dependent on
temperature, a 10-fold increase being observed every 16.5 degrees C (z =
16.5 degrees C, ie Q10 = 4.4). This commodity is also characterised by a
high initial microbial load (about 10(7) cells g-1). During storage at
various temperatures from 1 to 20 degrees C, oxygen uptake rates
dramatically increased with time and this phenomenon was well correlated
with the development of aerobic microorganisms which reached 10(9) cells
g-1 after 2 days at 20 degrees C or 9 days at 1 degrees C. Beansprouts
were packaged in films, with permeabilities ranging from 950 to 200000
ml O2 m-2 day-1 atm-1, and stored at 8 degrees C. Due to plant and
microbial metabolism, oxygen concentrations decreased steadily within
all packs until the onset of plant tissue decay. The latter occurred
after 5-6 days with the least permeable films but did not occur within
when the film permeability was over 100000 ml O2 m-2 day-1 atm-1.
However, such films favoured brown discolouration, exudation texture and
breakdown. The orientated polypropylene film (OPP) induced anoxic
condition within 2 days and favoured anaerobic metabolism and necrosis
of the sprouts. In all packages there was a rapid development of aerobic
microorganisms and lactic acid bacteria that resulted in the
accumulation of acetate and lactate and a decrease in pH. Thus, it
clearly appeared that tissue decay was enhanced by microbial activity.
At 8 degrees C 0.24 m2 of film per kg of sprouts provided the optimal
atmosphere composition (ie 5% oxygen and 15% carbon dioxide) when a film
permeability of 50000.
ml O2 m-2 day-1 atm-1 was used. These conditions allowed a shelf-life
of 4-5 days.
TI: Pathogenic microorganisms associated with fresh produce.
SO: J-food-prot. Des Moines, Iowa : International Association of
Milk, Food and Environmental Sanitarians. Feb 1996. v. 59 (2) p.
CN: DNAL 44.8-J824
AB: The presence of numerous genera of spoilage bacteria, yeasts and
molds, and an occasional pathogen on fresh produce has been recognized
for many years. Several outbreaks of human gastroenteritis have been
linked to the consumption of contaminated fresh vegetables and, to a
lesser extent, fruits. Salads containing raw vegetables have been
identified as vehicles of traveler's diarrhea, an illness sometimes
experienced by visitors to developing countries. Enterotoxigenic
Escherichia coli is the most common cause of this illness.
Enterohemorrhagic E. coli, specifically serotype O157:H7, has been
implicated as the causative agent in an outbreak of gastroenteritis
resulting from the consumption of cantaloupes. Outbreaks of
salmonellosis in humans have been attributed to consumption of
contaminated tomatoes, mustard cress, bean sprouts, cantaloupe, and
watermelon. An onion-associated outbreak of Shigella flexneri
gastroenteritis has recently been reported in the United States.
Outbreaks of human listeriosis have been epidemiologically linked to the
consumption of fresh cabbage and lettuce. Gastrointestinal illness
caused by the consumption of raw vegetable seed sprouts contaminated by
Bacillus cereus has been documented. The ability of Aeromonas hydrophila
and Aeromonas sobria to produce several virulence factors has been
documented and their fairly common occurrence in water raises concern
over public health risks that may be associated with the consumption of
salad vegetables, although their role as agents in foodborne illness has
not been fully confirmed. Viruses are not likely to grow on contaminated
vegetables and fruits but can survive long enough to cause
illness in humans. An increased per capita consumption of fresh and
lightly processed produce in the United States and other countries,
coupled with an increase in importation of produce to these countries
from regions where standards for growing and handling produce may be
compromised, has resulted in heightened interest in outbreaks of human
gastroenteritis that may be attributed to contaminated fresh produce,
particularly salad vegetables. Likewise methods of handling, processing,
packaging, and distribution of fresh produce on a regional or local
scale within countries are receiving attention in terms of identifying
and controlling microbiological hazards. Hazard analysis critical
control point (HACCP) programs are being developed in an effort to
minimize the risk of illness associated with consumption of fresh
produce. Examples of pathogenic microorganisms associated with fresh
produce as well as procedures that can be used to reduce their incidence
at the point of consumption are discussed.
> - --
> William Muraskin, Ph.D.
> Professor, Dept of Urban Studies
> Queens College, CUNY
> Michele Gale-Sinex, communications manager
> Center for Integrated Ag Systems
> UW-Madison College of Ag and Life Sciences
> Voice: (608) 262-8018 FAX: (608) 265-3020
> The black sesame rice crackers weren't sealed well,
> so they're the slightest bit soggy. They stick to my
> teeth like tamari Captain Crunch. --Mister 3D
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