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Two cases of poisoning by raw taro leaf and how a poison control centre, food safety inspectors, and a specialty supermarket chain found a solution


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Although the taro plant, Colocasia esculenta, is commonly consumed throughout Asia, Africa, the Pacific Islands, and the Caribbean, its consumption is less common in North America. Exposure to raw or improperly prepared taro is associated with oropharyngeal irritation and swelling and, rarely, airway obstruction. Although cases of toxicity in countries where taro is a staple have been reported, cases in North America have not been described. Here, two cases of oral irritation and swelling in BC residents who ate raw taro leaf, were reported to the British Columbia Drug and Poison Information Centre (BC DPIC) and triggered an investigation involving a regional health authority and the Canadian Food Inspection Agency. Investigators found that the vendor, a chain of ethnic supermarkets, offered no point of sale preparation instructions. The vendor responded initially by posting instructional signage and later by voluntary product withdrawal. Analysis of BC DPIC records between 1 November 2011 and 20 December 2013 identified 11 cases of symptomatic taro exposure, five to the leaf and six to the corm. The two index cases and subsequent investigation illustrate how new foods or foods in unfamiliar contexts may present as calls to a poison control centre and that prevention requires collaboration among public and corporate stakeholders. Key words: taro, food safety, poison control, health protection
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Two cases of poisoning by raw taro leaf and how a
poison control centre, food safety inspectors, and a
specialty supermarket chain found a solution
John D. Omura*
, Christopher Blake
, Lorraine McIntyre
, Dorothy Li
and Tom Kosatsky
*University of British Columbia, School of Population and Public Health, Vancouver, BC.
Environmental Health Services, BC Centre for Disease Control, Vancouver, BC.
McMaster University, Hamilton, ON.
BC Drug and Poison Information Centre, BC Centre for Disease Control, Vancouver, BC.
Abstract: Although the taro plant, Colocasia esculenta, is commonly consumed throughout Asia, Africa, the Pacific Islands,
and the Caribbean, its consumption is less common in North America. Exposure to raw or improperly prepared taro is
associated with oropharyngeal irritation and swelling and, rarely, airway obstruction. Although cases of toxicity in
countries where taro is a staple have been reported, cases in North America have not been described. Here, two cases of
oral irritation and swelling in BC residents who ate raw taro leaf, were reported to the British Columbia Drug and Poison
Information Centre (BC DPIC) and triggered an investigation involving a regional health authority and the Canadian Food
Inspection Agency. Investigators found that the vendor, a chain of ethnic supermarkets, offered no point of sale
preparation instructions. The vendor responded initially by posting instructional signage and later by voluntary product
withdrawal. Analysis of BC DPIC records between 1 November 2011 and 20 December 2013 identified 11 cases of
symptomatic taro exposure, five to the leaf and six to the corm. The two index cases and subsequent investigation
illustrate how new foods or foods in unfamiliar contexts may present as calls to a poison control centre and that
prevention requires collaboration among public and corporate stakeholders.
Key words: taro, food safety, poison control, health protection
The taro plant, Colocasia esculenta, is a common staple
grown and consumed throughout Asia, Africa, the Pacific
Islands, and the Caribbean (Matthews 2004; Rao et al. 2010).
As raw consumption can result in an acrid taste accompanied
by swelling and irritation of the mouth and throat (Savage et al.
2009), corms, leaves, and possibly other parts (e.g., stalks) of the
taro are commonly eaten cooked. The potential for severe
reaction is illustrated by a case report from China that described
progression to airway obstruction following the ingestion of
wild Chinese taro (Alocasia cucullata) (Yuen 2001).
There is disagreement surrounding the exact mechanism by
which raw taro causes oropharyngeal irritation. It is largely
thought to stem from specialized plant cells called idioblasts,
which contain bundles of oxalate crystals called raphides coated
with a proteolytic enzyme. When the plant is crushed or
chewed, the idioblasts forcibly eject the raphides along with the
proteolytic enzyme into the oropharynx causing micro-trauma
and a local reaction (Bradbury and Nixon 1998; Noonan and
Savage 1999; Tagwireyi and Ball 2001; Paull et al. 1999; Savage
et al. 2009; Pang et al. 2010).
Taro contains both insoluble and soluble oxalates. Soluble
oxalates are more readily absorbed from the gastrointestinal
tract compared with the poorly absorbed insoluble oxalates and
are therefore more likely to cause systemic toxicity (Noonan
and Savage 1999). Rarely, renal failure and hypocalcemia (Sanz
and Reig 1992; Noonan and Savage 1999) have been associated
with consumption of plants containing oxalates. Only one case
(suicide attempt) of systemic toxicity attributed to taro leaf
ingestion was identified in the literature, with reported findings
including muscle spasms and renal insufficiency (Tagwireyi and
Ball 2001; Oscarsson and Savage 2007).
Distribution of taro products, particularly its leaves, is
uncommon in North America except through ethnic super-
markets. Consequently, a lack of public awareness regarding
proper preparation and cooking techniques could potentially
result in negative health consequences. The acridity of the taro
corms and leaves varies with species, age of plant, and growing
conditions. In some countries where cultivars are known to
have very low acridity, parts of the plant are eaten raw
(Bradbury and Nixon 1998; Rao et al. 2010). This report
Corresponding author: Tom Kosatsky (email: tom.kosatsky@bc
EHR Vol. 57(3) 5964 DOI: dx.doi.10.5864/d2014-027 Published on 9 October 2014
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presents a series of taro poisoning cases, the process by which a
provincial poison control centre brought these cases to the
attention of health protection services, and the subsequent
public health response.
Event summary
In June 2013 the British Columbia Drug and Poison
Information Centre (BC DPIC) received a call from a healthy
middle-aged couple reporting symptoms after ingestion of raw
taro leaves. They had purchased the item the same day from an
Asian supermarket in Vancouver, Canada. Unfamiliar with
appropriate preparation methods, they consumed one to two
raw leaves the size of a hand. Shortly afterwards, both
experienced irritation and burning in the mouth, followed by
swelling at the back of the throat. All symptoms resolved
spontaneously within several hours. The couple did not seek
further medical care.
In November 2013 BC DPIC received another call from a
healthy adult male who had consumed raw taro leaf the evening
prior. The product had been purchased from the same
supermarket chain, but at a different location. He immediately
developed oral paresthesia and swelling, followed by emesis and
pain in his mouth and throat. His symptoms slowly resolved
through the night with the exception of prolonged swelling of
his tongue. BC DPIC staff managed these cases at home by
instructing callers to drink milk and use ice chips to reduce the
oral irritation. Follow-up calls were made to monitor progres-
sion or resolution of symptoms.
Following the occurrence of these relatively uncommon
cases over a short period, BC DPIC’s database (Visual Dotlab
Enterprise, WBM Software, Fresno, CA) was searched for
similar cases between 1 November 2011 and 20 December
2013. Eleven cases of symptomatic taro exposure were
identified over this period, five related to taro leaves and six
to taro corm (Table 1). Of the cases pertaining to leaf
exposure, all occurred between April and November 2013 and
followed ingestion. One of the cases involved partially
Table 1. Symptomatic case reports of taro exposure made to DPIC (1 November 2012 to 31 December 2013).
Year Month Region Gender
Method of
exposure Amount of exposure Symptoms
2012 January Lower
Female Corm Dermal
Raw Dermal irritation
2012 May Lower
Female Corm Ingestion 30 g, raw Oral irritation within 5
2012 July Vancouver
Male Corm Ingestion 30 g, raw Mouth burning
2013 February Lower
Male Corm Ingestion 34 bites raw Sore throat within 30
2013 March Vancouver
Male Corm Ingestion Small piece raw Oral irritation within 20
2013 April Lower
Female Leaf Ingestion 2 leaves partially
cooked (no details)
Oral paresthesia within 30
2013 June Lower
Female Leaf Ingestion Few bites of food
cooked in taro leaf
Oral paresthesia
2013 June Lower
Male Leaf Ingestion 1 leaf (size of hand)
Burning in mouth, oral
2013 June Lower
Female Leaf Ingestion 2 leaves (size of hand)
Burning in mouth, oral
2013 November Lower
Male Leaf Ingestion 2 bites raw Oral irritation, swelling,
immediately; then
vomiting, sore throat,
2013 December Lower
Female Corm Ingestion 4 bites of dried corm,
cooked (method not
Bitter taste and tingling
tongue soon after
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cooked taro leaf and one case involved ingestion of food
cooked in taro leaf with no details provided on the method of
cooking. Of the cases pertaining to corm exposure, five were
related to ingestion and one to dermal exposure. The five oral
exposures occurred between May 2012 and December 2013.
All five cases pertaining to leaf exposure were received from
BC’s lower mainland. This region is home to the largest
population of immigrants in the province (WelcomeBC
2008). Of the corm-related cases, four were received from
the lower mainland (Vancouver and surrounding region) and
two were from Vancouver Island. In addition, five asympto-
matic calls all pertaining to raw corm exposure were identified
(Table 2). All symptomatic and asymptomatic cases were
Field investigation and communication
Following the initial report in June, BC DPIC staff contacted
food safety specialists at the BC Centre for Disease Control
(BCCDC). Finding an apparent lack of instructional in-
formation around taro leaf toxicity and safety practices on
government and regulatory websites, the BCCDC contacted
Health Canada and subsequently the Canadian Food Inspec-
tion Agency (CFIA). The CFIA referred the issue of taro
toxicity to their Fresh Fruits and Vegetables Program. Health
Canada staff brought the issue to the attention of the
Chemical Health Hazard Assessment Division of the Bureau
of Chemical Safety which recommended that a fact sheet be
With the emergence of the additional case in November,
discussions resumed between BCCDC and the CFIA. This
case identified the name and location of the supermarket store
where the product had been purchased. BCCDC notified and
requested assistance from the regional health authority, which
sent a food safety inspector to the store. At the time of
inspection, no cooking instructions were observed near the
product or on the product packaging (Figures 1, 2, and 3).
Further, employees who were interviewed provided conflicting
information regarding appropriate preparation methods: one
employee advised that taro leaf should only be used for display
or to infuse flavour into food and was not edible even after
cooking, whereas another employee advised that taro leaf was
safe to consume after cooking.
Six days after the initial inspection, the supermarket manager
voluntarily posted a sign instructing customers to cook taro
leaves prior to consumption (Figure 4). Two weeks later the
CFIA also sent an inspector to the supermarket and contacted
the chain’s head office to inquire about the product. At the end
of November the chain voluntarily discontinued sale of the
product. By December the CFIA began developing a consumer
fact sheet on natural toxins in taro leaves for the Natural
Toxins in Fresh Fruit and Vegetables section of their website.
Given that consumption of raw taro is uncommon, literature
regarding exposure to the raw form is limited. Despite this,
several case reports highlight the medical significance of raw
taro exposure. For example a 45-year-old man in Hong Kong
developed mouth and throat pain and later upper airway
obstruction after consuming raw wild Chinese taro (Alocasia
cucullata or Colocasia cucullata) (Yuen 2001). It was not
specified whether he consumed taro corm or leaf. Consump-
tion of taro leaves is typically less common than corms, and raw
leaf consumption is presumably even less common. However, a
case report from Greece demonstrates the potential health
consequences of raw taro leaf exposure: a 2-year-old boy who
presumably consumed a portion of the houseplant leaf known
as Elephant’s Ear (Colocasia esculenta) developed acute drool-
ing, speech difficulties, and dysphagia (Mihailidou et al. 2002).
The patient recovered without any treatment.
In Zimbabwe, Elephant Ear is known as Madhumbe and is a
staple food in certain regions. A retrospective review of hospital
Table 2. Asymptomatic calls of taro exposure made to DPIC (1 November 2012 to 31 December 2013)
Year Month Region Gender
Method of
exposure Amount of exposure Symptoms
2011 December Lower
Female Corm Ingestion 1 mouthful raw Asymptomatic at 5
2011 December Lower
Male Corm Ingestion 1 mouthful raw Asymptomatic at 5
2012 October Lower
Female Corm Ingestion 2 large raw; juiced with
vegetables and fruits
Asymptomatic at 15
2012 October Lower
Male Corm Ingestion 2 large raw; juiced with
vegetables and fruits
Asymptomatic at 15
2013 February Lower
Female Corm Ingestion Small piece raw Asymptomatic at 30
Omura et al. 61
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admissions in six referral hospitals in Zimbabwe from 1980
1989 due to food poisoning found 47 cases of taro leaf
poisoning, making it the third most commonly reported type
of food poisoning (Kasilo and Nhachi 1994). Moreover, the
majority of cases were among children, with 33 of the 47 (70%)
cases being under five years of age. Similarly, a retrospective
review from Hong Kong identified 21 adult cases of taro
poisoning between 2005 and 2009 (Pang et al. 2010),
constituting two-thirds of poison control calls for oral mucosal
irritation following plant ingestions. The part of the plant
consumed, corm or leaf, was not specified. Although both
reviews came from regions more commonly consuming taro
than North America, the frequency of events suggests that even
in areas of widespread taro availability and consumption,
symptomatic exposures to raw taro occur due to improper
preparation and consumption practices.
Lessons learned
Given the risk of problematic exposure to raw taro leaf
resulting from lack of awareness and increased availability of
Fig. 2. Taro leaf in product packaging as observed during
the grocery store inspection.
Fig. 3. Labelling of taro leaf product as observed during
the grocery store inspection.
Fig. 1. Taro leaf as observed during the grocery store
Fig. 4. Point of sale signage as subsequently observed in
the grocery store.
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the product, mitigating exposure appears necessary as demon-
strated by the frequency of reported cases and successful actions
described here. In fact, no new cases of taro leaf exposure were
reported to BC DPIC from 21 December 2013 to 26 May
2014. Although many food preparation techniques for detox-
ifying taro leaves have been described, including grating and
macerating, mashing and pounding, baking, boiling, steaming,
washing in cold water, adding salt, and soaking and cooking in
milk (Matthews 2004; Oscarsson and Savage 2007; Kaushal
et al. 2013), the most often recommended method is cooking
the leaves in boiling water for at least 30 minutes (Savage and
Dubois 2006). The mechanism by which cooking decreases the
acridity of the plant is not fully understood, though it has been
suggested that applying heat denatures the raphide protease
thought to be responsible for the plant’s toxicity (Paull et al.
1999). Individuals new to using taro leaf may not be familiar
with these food preparation techniques. Compared with taro
leaves, taro corm availability and consumption are more
common in North America. Taro corm (Figure 5), when
cooked, has an appealing purple colour and is used in many
popular Asian dishes such as taro cake (named yu
`tou or yu
in China) and in bubble teas. As with taro leaves, taro corm
preparation may involve washing in water, baking, boiling, or
other techniques prior to further preparation and consump-
tion. And just as consumers are unfamiliar with taro leaves,
they may also be unaware that taro corms need to be detoxified
before handling and consumption. As such, issues with
handling taro corms may also be of importance particularly
given the potential dermal reactions to skin contact with raw
corms. In general, additional interventions through public
health protection services are likely necessary to ensure that
consumers and food handlers are adequately informed regard-
ing preparation instructions, including information at the
point of sale. Instructions on the label packaging should
include the use of gloves while preparing these foods to prevent
dermal exposure, a warning not to consume raw taro leaves or
corms, and to details on how to thoroughly cook before
In the case of oral exposure to raw taro leaf or corm, patients
should first be assessed for airway compromise. Should
significant oropharyngeal swelling or airway compromise occur,
patients should obtain emergent medical attention at a health
care facility (Yuen 2001). In the absence of severe symptoms,
patients should be instructed to immediately remove any plant
debris from the mouth by wiping with a wet cloth, rinsing
the mouth with water to flush out the crystals, then drinking a
full glass of milk or ingesting another calcium-containing food
or supplement (Yuen 2001). The calcium is thought to limit
absorption of soluble oxalates by forming insoluble calcium
salts (Hossain 2003; Brogren and Savage 2003). Cold items such
as popsicles, ice cream, or ice chips may provide symptomatic
relief for the local irritation. Patients or caregivers can further
monitor for worsening of symptoms during the first few hours
after oral exposure.
Future challenges
In the setting of ever changing urban Canadian environments,
this report demonstrates the potential health impact of
emerging food products with which health protection services
may have limited awareness or experience. The described cases
likely under represent the actual number of taro plant
poisonings in the province because of the mild and self-
resolving nature of most reactions. Health protection services
must remain vigilant to changing population demographics,
food trends and preferences, and the retail food market. This
can be particularly challenging in multicultural cities where
such food products may be sold in a limited set of specialty
Poison control centres offer a potential mechanism for
monitoring such trends, therefore providing an important
service to the general public. BC DPIC receives over 26,000
calls annually and thus receives and holds valuable and
substantial data. When monitored in real time these data
have the potential to serve as an important surveillance tool,
and in doing so poison control centres can trigger and inform
health protection practices.
The authors would like to thank the BC Drug and Poison
Information Centre, the Canadian Food Inspection Agency,
Health Canada, and the Fraser Health Authority for their
assistance with this investigation.
The authors would like to thank Daniel Mosquin, Research
Manager, UBC Botanical Garden, Vancouver, BC, for his
assistance with plant terminology and identification.
The photographs used in this report are courtesy of the
Fraser Health Authority.
Bradbury, J., and Nixon, R. 1998. The acridity of raphides from the
edible aroids. J. Sci. Food Agric, 76: 608616. doi: 10.1002/(SICI)
Brogren, M., and Savage, G. 2003. Bioavailability of soluble oxalate
from spinach eaten with and without milk products. Asia Pac. J.
Clin. Nutr, 12(2): 219224.
Fig. 5. Taro corm.
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Hossain, R.Z., Ogawa, Y., Morozumi, M., Hokama, S., and Sugaya, K.
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Kasilo, O.M.J., and Nhachi, C.F.B. 1994. Food Poisoning Admissions
in Referral Hospitals in Zimbabwe: A Retrospective Study. Hum.
Exp. Toxicol, 13(2): 7782.doi: 10.1177/096032719401300203.
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... This may also apply to other leaf beetles such as Aplosonyx chalibaeus (Hope). Aplosonyx chalibaeus is a shiny-coloured beetle which feeds on taro, a plant known to be toxic when eaten raw [39]. A similar concern exists with the blister beetles Meloe sp. and Mylabris sp., which usually produce cantharidin that can cause poisoning [40] and the burnet moth Zygaena sp., which sequesters toxic cyanogenic glucosides as a chemical anti-predator defence [41]. ...
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Background: Data from poison centers have the potential to be valuable for public health surveillance of long-term trends, short-term aberrations from those trends, and poisonings occurring in near-real-time. This information can enable long-term prevention via programs and policies and short-term control via immediate public health response. Over the past decade, there has been an increasing use of poison control data for surveillance in the United States, Europe, and New Zealand, but this resource still remains widely underused. Objective: The British Columbia (BC) Drug and Poison Information Centre (DPIC) is one of five such services in Canada, and it is the only one nested within a public health agency. This study aimed to demonstrate how DPIC data are used for routine public health surveillance in near-real-time using the case study of its alerting system for illness related to consumption of shellfish (ASIRCS). Methods: Every hour, a connection is opened between the WBM software Visual Dotlab Enterprise, which holds the DPIC database, and the R statistical computing environment. This platform is used to extract, clean, and merge all necessary raw data tables into a single data file. ASIRCS automatically and retrospectively scans a 24-hour window within the data file for new cases related to illnesses from shellfish consumption. Detected cases are queried using a list of attributes: the caller location, exposure type, reasons for the exposure, and a list of keywords searched in the clinical notes. The alert generates a report that is tailored to the needs of food safety specialists, who then assess and respond to detected cases. Results: The ASIRCS system alerted on 79 cases between January 2015 and December 2016, and retrospective analysis found 11 cases that were missed. All cases were reviewed by food safety specialists, and 58% (46/79) were referred to designated regional health authority contacts for follow-up. Of the 42% (33/79) cases that were not referred to health authorities, some were missing follow-up information, some were triggered by allergies to shellfish, and some were triggered by shellfish-related keywords appearing in the case notes for nonshellfish-related cases. Improvements were made between 2015 and 2016 to reduce the number of cases with missing follow-up information. Conclusions: The surveillance capacity is evident within poison control data as shown from the novel use of DPIC data for identifying illnesses related to shellfish consumption in BC. The further development of surveillance programs could improve and enhance response to public health emergencies related to acute illnesses, chronic diseases, and environmental exposures.
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Panamá se caracteriza por una gran heterogeneidad topográfica y climática, lo que da lugar a una variedad de hábitats y microclimas que promueve a su vez una alta diversidad de plantas. La rica flora panameña ha sido objeto de estudios botánicos desde mucho antes de los primeros indicios de la construcción de la vía interoceánica a manos de los franceses. En 1790 los botánicos Luis Née y Thaddäus Haenke ya realizaban sus colecciones en los perímetros de la ciudad de Panamá. Desde entonces, el conocimiento de la flora panameña continúa en expansión, con nuevos reportes y especies nuevas para la ciencia y la humanidad. Si bien el endemismo, o sea la existencia de especies únicas de un territorio, y el descubrimiento de nuevas especies representan uno de los mayores alcances de los estudios botánicos en Panamá, hoy día las investigaciones botánicas toman un nuevo auge, pues las hojas, tallos, raíces y frutos de esta flora, albergan una alta diversidad; tanto de compuestos químicos prestos a ser descubiertos por la ciencia como posible cura de enfermedades, así como de endófitos (hongos o bacterias que viven en los tejidos vegetales sin causar daños aparentes a la planta hospedera), que también producen compuestos químicos utilizables en la búsqueda de fármacos útiles para la medicina. Y es que es conocido que más del 70% de la población mundial utiliza las plantas en la medicina tradicional para atender sus necesidades médicas. Para todos nos es común el té de mastranto, recetado por la abuela para algunos malestares estomacales, o un té de jengibre para el resfriado. Esto no solo resalta la importancia que tienen las plantas en la vida del hombre, sino la necesidad de seguir explorando de manera científica y sistemática la riqueza botánica de nuestro país. La bioprospección, que no es más que la exploración científica en plantas y otros organismos (p.ej., bacterias y endófitos) de moléculas potencialmente benéficas, ha contribuido a conocer más sobre la flora panameña. Los proyectos de bioprospección llevados a cabo en Panamá han generado capacidades técnicas en diferentes instituciones y áreas del conocimiento a nivel nacional. Además, ha servido de apoyo a la misión de conservación de muchas de las áreas protegidas del país. En este capítulo presentamos una muestra representativa del gran potencial farmacognóstico que tiene nuestra flora. Si bien en este caso se trata de especies cuyos compuestos químicos pueden ocasionar cuadros tóxicos severos y en ocasiones hasta la muerte, el mismo sirve de ejemplo de cómo los químicos contenidos en las plantas pueden mediar condiciones favorables o desfavorables para los humanos. Las especies presentadas en este capítulo representan una pequeña porción de la flora tóxica del país, pero brindan un buen ejemplo de la diversidad de compuestos tóxicos y principios activos de la flora panameña.
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Technology for utilization of seabuckthorn berries for preparation of fruit leather/bar was optimized by modifying the foam mat drying technique. The conversion of seabuckthorn juice/pulp into foam was standardized by whipping the pulp after addition of CMC @ 0–3% at 5 °C and drying the resultant foam in dehydrator (55 ± 2 °C) to a moisture content of about 12–14%. The fruit bar prepared from sulphited juice/pulp wrapped in a butter paper followed by packing in polyethylene pouches (20 g) and stored at ambient temperature (14.6–26.1 °C) experienced least changes in quality attributes like ascorbic acid (1045.7 mg/100 g vs 997.5 mg/100 g) and carotenoids (80.4 mg/100 g vs 72.3 mg/100 g) as compared to the leather made from the unsulphited pulp. Storage studies indicate that fruit bars are mildly hygroscopic (0.46–0.65) and can be stored within the RH of 46–65% at room temperature.
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Taro is one of the world’s oldest food crops, dating back over 9,000 years. This ancient crop, first domesticated in Southeast Asia, has continued to spread throughout the world and is now an important crop in Asia, Pacific, Africa and the Caribbean. It is a crop that has been maintained by farmers for millennia and taro genetic resources have remained largely under the control of local communities. The history of its adaptation, use and diversification can teach us many things about using and conserving genetic resources.
We describe a case of Taro poisoning presenting as severe buccal and throat pain, which later progress to cause upper airway obstruction. Chinese Taro is not normally consumed as food in Hong Kong, though it is readily found growing wild in the countryside. The chemical responsible for the poisoning is Oxalate, which is also found in other species of plant. (Hong Kong 2001;8:163-165) Case report A 45-year-old man presented to the local emergency department with severe mouth and throat pain after eating wild Chinese Taro obtained from the hillside near the border between Mainland China and Hong Kong. He was a villager and regularly picked plants from the hillside for cooking. His major complaint was severe mouth and throat pain immediately after he took a bite of the taro, which he did not ingest. Communication with him was difficult as the pain was so severe that he could not open his mouth properly and could only communicate by writing. His vitals signs were stable with a blood pressure of 150/80 mmHg and a regular pulse of 90 per minute. The oxygen saturation was 97% on room air with a respiratory rate of 18 per minute. Clinical examination revealed a middle age man in agony with swelling of the lips and cheeks and drooping of saliva at the angle of mouth. The chest was clear and there was no stridor audible. He was then given an intravenous injection of "Ketorolae" for the pain and his mouth was irrigated with saline. He was reassessed ten minutes later. The pain was still severe and he started to complain of shortness of breath. His respiratory rate had increased to 28 per minute with an oxygen saturation of 95%, but there was no stridor audible. A fibro-optic inspection of the larynx was performed, where they found a mildly swollen epiglottis partially obstructing the airway. The patient was intubated by fibro-optic means and admitted to ICU. A bolus dose of chlorpheniramine was administered. He undergone an uneventful recovery in ICU and was extubated on day 2 and discharged on day 4, with the advice that he should not pick up wild plants to eat in the future.
Tubers are important sources of carbohydrates as an energy source and are used as staple foods in tropical and subtropical countries. They are generally processed into various forms before consumption. Processing makes them digestible and palatable, extends the shelf life and reduces post-harvest losses. Taro (Colocasia esculenta) is a tropical tuber crop largely produced for its underground corms contain 70–80 % starch and the corms of Colocasia antiquorum contain anthocyanins such as cyanidin-3-glucoside, pelargonidin-3-glucoside and cyanidin-3-chemnoside which were reported to have antioxidative and anti-inflammatory properties. Taro consumption has been affected by the presence of acridity factors, which cause sharp irritation and burning sensation in the throat and mouth on ingestion. Taro is rich in gums (mucilage) and small sizes of starch granules makes it a highly digestible which is used for the preparation of various foods. The present paper deals with reviewing the nutritional, antinutritional and utilization of Taro into the various food products.
Oxalic acid and its salts occur as end products of metabolism in a number of plant tissues. When these plants are eaten they may have an adverse effect because oxalates bind calcium and other minerals. While oxalic acid is a normal end product of mammalian metabolism, the consumption of additional oxalic acid may cause stone formation in the urinary tract when the acid is excreted in the urine. Soaking and cooking of foodstuffs high in oxalate will reduce the oxalate content by leaching. The mean daily intake of oxalate in English diets has been calculated to be 70-150 mg, with tea appearing to contribute the greatest proportion of oxalate in these diets; rhubarb, spinach and beet are other common high oxalate-content foods. Vegetarians who consume greater amounts of vegetables will have a higher intake of oxalates, which may reduce calcium availability. This may be an increased risk factor for women, who require greater amounts of calcium in the diet. In humans, diets low in calcium and high in oxalates are not recommended but the occasional consumption of high oxalate foods as part of a nuritious diet does not pose any particular problem.
The corms and leaves of most cultivars of the edible aroids, the major staple food of about 200 million people in the tropics, are acrid. This means that if eaten raw they cause swelling of the lips, mouth and throat. This effect is related to the presence of needle-like raphides of calcium oxalate. A new method was developed for the separation of raphides using petroleum ether (PE) and then purification by centrifugation. The acrid raphides were shown by X-ray powder diffraction to consist of calcium oxalate monohydrate (whewellite) and their morphology was studied by scanning electron microscopy. Two distinct types of raphides (thick and thin) were observed and druses (rosette like structures of calcium oxalate) were found only in taro leaves. A comparative survey of raphide morphology was made over four species of aroids. The removal of the acridity of raphides by immersion in hydroxylic solvents, but not in PE, indicates the presence of an irritant on the raphides. Acridity is due to the dual action of the sharp raphides in puncturing soft skin and the irritant (a protease) in causing swelling and soreness. © 1998 SCI.
The acridity in Araceae species was not apparently due to the calcium oxalate raphides. Some irritant on the raphide surface caused the acridity, with the raphides apparently functioning to carry the acridity factor. Methanol and methylene chloride extracts from purified raphides did not show any compounds in GC-mass spectrometry (MS) analysis that could be regarded as acrid. The data suggested that a 26 kDa protein, possibly a cysteine proteinase, was the active factor. There were a few other uncharacterized protein bands associated with the raphides that could also be involved. Some amino acid sequence data for the 26 kDa protein was obtained.
Taro (Colocasia esculenta var. Schott) is a major staple food crop in parts of Asia and the Pacific Islands and two different cultivars of taro plants Taro Tonga (C. esculenta) and Taro Futuna (Xanthosoma sagittifolium), known respectively as Maori and Japanese, are grown as a minor crop in New Zealand. The leaves are either boiled or baked before they are consumed. In this experiment the leaves were baked at 150 °C for 1.5 h either alone or with additions of cows milk and coconut milk prior to baking. Oxalate contents of both cultivars of leaves were determined following extraction by either hot distilled water (80 °C) to give soluble oxalates or hot (80 °C) acid (0.2 mol/l HCl) to give total oxalates. The extracted oxalates were then determined by HPLC chromatography. Baked Maori-type taro leaves contained 719.3 ± 12.0 mg total oxalates/100 g fresh weight (FW) and 365.9 ± 11.4 soluble oxalates/100 g FW while baked Japanese-type leaves contained 533.9 ± 14.9 mg total oxalates/100 g FW and 352.6 ± 8.4 mg soluble oxalates/100 g FW. The total and soluble oxalate content of the baked leaves was considerably reduced when the leaves were baked with cows milk, coconut milk or mixtures of these two (mean % reduction of total oxalates was 43.2 ± 3.8% while the mean % reduction of soluble oxalates was 58.7 ± 1.8%).
Taro (Colocasia esculenta var. Schott) is a major staple food crop in parts of Asia and the Pacific Islands and is grown as a minor crop in New Zealand. Soluble, insoluble and total oxalate content of young and older leaves were determined by HPLC following hot water (80 °C) and hot (80 °C) acid (0.2 mol/L HCL) extractions. Young taro leaves contained 589 ± 35.8 mg total oxalates/100 g fresh weight (FW) while older taro leaves contained (443 ± 15.0 mg total oxalates/100 g FW). Soluble oxalates were 74% of the total oxalate content of the young and old leaves.Oxalate analysis was also carried out on leaves baked at 150°C for 1.5 h either alone or with 50 ml cows milk. The soluble oxalate content of the fresh baked tissue fell to a mean of 59% for both samples of leaves. Baking the young and old leaves with milk led to a further reduction of the soluble oxalate content in the cooked leaves (mean 21.4% of the total oxalates). The results from this study suggest that baked taro leaves should be regarded as a high oxalate food but baking with milk significantly reduces the amount of soluble oxalate that could be absorbed from the cooked leaves.
Objective To study the local epidemiology and clinical presentation after ingestion of oral mucosal irritating plants. Methodology Cases presenting with immediate oral mucosal irritation after plant product ingestion from July 2005 to June 2009 were retrieved from the Hong Kong Poison Information Centre's clinical database. Their clinical features and management were reviewed. Results Thirty cases were retrieved and analysed, including 14 males and 16 females. Poisoning occurred all year round with no seasonal predilection. Vomiting and dysphagia were the two most common symptoms other than immediate oral mucosal irritation. Half of the cases could be managed with symptomatic treatment and discharged after a few hours of observation. Six patients presented with angioedema and were managed initially with the use of intravenous steroid, antihistamine and with or without adrenaline. Urgent airway assessment with laryngoscope was performed in 3 patients. No patient required endotracheal intubation. Conclusion Oral mucosal irritating plant ingestion is not uncommon in Hong Kong. Its clinical feature can mimic angioedema on presentation. Immediate and localized oral mucosal symptoms after plant product ingestion are the key to diagnosis.