Transcript Food Additives

Food Safety
Food additives
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Additives: Substances, such as
preservatives (防腐劑), emulsifiers (乳
化劑), antioxidants (抗氧化劑), and
stabilizers (穩定劑), are often added to
a food to do the following:
• Enable it to be processed more easily
• Preserve it longer and reduce spoilage
(腐壞)
• Prevent contamination by
microorganisms and thus prevent foodborne disorders
• Improve taste, add color, or enhance its
aroma (氣味), making it more appealing
• For example, nitrite (亞硝酸, NO2− ), which
is used in cured meats, not only improves
flavor but also inhibits the growth of
bacteria that cause botulism (肉毒桿菌中
毒). However, nitrite converts to
nitrosamines (亞硝胺, R1N(-R2)-N=O,),
which can cause cancer in animals.
• approximately 90% of nitrosamine
compounds were deemed to be
carcinogenic (致癌物).
Common contaminants
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Pesticides
Heavy metals
Nitrates (in green leafy vegetables)
Aflatoxins (黃麴毒素), produced by
molds (in nuts and milk)
Growth-promoting hormones (in dairy
products and meat)
• 黃麴毒素的影響主要是在肝臟，高劑量黃
麴毒素會造成肝臟壞死及急性的肝衰竭，
可能會進一步發展成肝硬化或是肝癌。
• On the other hand, the amount of nitrite
added to cured meat is small compared
with the amount of nitrates (硝酸) that
occurs naturally in food and that is
converted to nitrite (亞硝酸) by the salivary
glands.#1
Food Safety
Botulism
• Clostridium botulinum is a bacterium
that produces dangerous toxins
(botulinum toxins) under low-oxygen
conditions.
• Botulinum toxins are one of the most
lethal substances known.
• Botulinum toxins block nerve functions
and can lead to respiratory and
muscular paralysis.
• Human botulism, caused by ingestion of
contaminated food, is a rare but potentially
fatal disease if not diagnosed rapidly and
treated with antitoxin.
• Foodborne botulism is often caused by
eating improperly processed food.
• Homemade canned, preserved (醃) or
fermented foodstuffs require extra caution.
Overview
• A serious, potentially fatal disease. However, it is
relatively rare. Usually caused by ingestion of
potent neurotoxins (神經毒素) in contaminated
foods. Person to person transmission of botulism
does not occur.
• spores that are heat-resistant and exist widely
in the environment, and in the absence of
oxygen they germinate, grow and then excrete
toxins.
• There are seven distinct forms of
botulinum toxin, types A–G. Four of these
(types A, B, E and rarely F) cause human
botulism. Types C, D and E cause illness
in other mammals, birds and fish.
• Mainly a foodborne intoxication, botulism
can also be caused by intestinal infection
in infants, wound infections, and by
inhalation.
Symptoms
• Early symptoms are marked fatigue,
weakness and vertigo (眩暈), usually
followed by blurred vision, dry mouth and
difficulty in swallowing and speaking.
Vomiting, diarrhoea (腹瀉), constipation
and abdominal swelling may also occur.
The disease can progress to weakness in
the neck and arms, after which the
respiratory muscles and muscles of the
lower body are affected.
• The paralysis may make breathing difficult.
There is no fever and no loss of consciousness.
Symptoms usually appear within 12 to 36 hours
(within a minimum and maximum range of four
hours to eight days) after exposure. Incidence of
botulism is low, but the mortality rate is high if
prompt diagnosis and appropriate, immediate
treatment (early administration of antitoxin and
intensive respiratory care) are not given. Fatal in
5-10 % of cases.
Botox
• The same bacterium that is used to
produce Botox, a pharmaceutical product
predominantly injected for clinical and
cosmetic use.
• Botox treatments employ the purified and
heavily diluted botulinum neurotoxin type A.
Salmonella (non-typhoidal)
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Salmonellosis (沙門桿菌病), is one of the
most common and widely distributed
foodborne diseases, with tens of millions of
human cases occurring worldwide every
year.
Most cases of salmonellosis are mild,
however, sometimes people die from
salmonellosis. The severity of the disease
may depend on host factors and the strain
of salmonella.
• Since the beginning of the 1990s,
salmonella strains which are resistant
to a range of antimicrobials have
emerged and are now a serious public
health concern.
• Basic food hygiene practices, such as
"cook thoroughly", is recommended as a
preventive measure against salmonellosis.
Zoonoses (寄生物病) and Food
Safety
• Zoonotic diseases are a group of infectious
diseases that are naturally transmitted between
vertebrate animals and humans.
• More than 60% of the newly identified infectious
agents that have affected people over the past
few decades have been caused by pathogens
originating from animals or animal products.
• Seventy percent of these zoonotic infections
originate from wildlife.
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some are transmissible to humans
through food (brucellosis布魯氏桿菌病
(unsterilized milk or meat, tuberculosis結
核), through bites from infected
mammals (rabies狂犬病) and insects
(Rift Valley Fever) or via environmental
contamination (echinococcosis絛蟲病
/hydatidosis).
• Avian influenza:
• Pandemic (H1N1) 2009:
• There are 17 different H antigens (H1 to
H17) and 10 different N antigens (N1 to
N10).
Microbiological risks in food
• We cannot expect to “solve” the problem
of microbiological food safety to the point
of having a zero-risk food supply.
• A microorganism evolves to become
pathogenic, or a pathogen evolves to
become more virulent.
• may become more susceptible to illness if
their immune system is not functioning at
an optimal level.
• The Centers for Disease Control and
Prevention (CDC) estimates there are 76
million cases of foodborne illness each
year, resulting in 325,000 hospitalizations
and 5,000 deaths.
• More than 200 known diseases are
caused by pathogens, their toxins, or other
substances transmitted through food.
• The recognized microbiological causes of
foodborne illness include viruses (病毒),
bacteria (細菌), parasites (寄生蟲), and
toxins produced by algae (藻類) and fungi
(真菌).
• For food safety, refrigerators should be
maintained at 40 F or cooler.
• The microorganisms that cause a food to
appear spoiled are different from the
foodborne pathogens that make people
sick. Spoilage microorganisms are rarely
pathogenic.
• Unlike spoilage microorganisms that often
produce changes in a food’s odor and
color, pathogens usually do not produce
observable changes in food.
• Fish species contain high levels of free
histidine (組胺酸) in their tissue and when
such fish are subjected to temperature
abuse after harvest, bacteria
decarboxylate (羧酸, -COO− ) histidine to
produce histamine. A number of bacterial
species can produce histamine.
• Each part of the food chain poses different
risks.
• Microbiological food safety is truly a farmto-table issue. #
Risks of Chemicals in Foods
• According to the Toxic Substances Control
Act list by the U.S. Environmental
Protection Agency (EPA), there are more
than 75000 known chemicals in our
environment, many of which may come in
contact with food via soil, air, or water.
Bisphenol A (雙酚A)
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Bisphenol A (BPA) is a widely used
chemical in polycarbonate (聚碳酸酯)
plastic and epoxy resins (環氧樹脂),
also used in food contact materials,
leading to potential consumer exposure
through food.
polycarbonate (聚碳酸酯)
• Optical media, building and construction,
transportation, appliances and
computer/business equipment, medical
and packaging.
• Food service items: sports bottles, baby
bottles, pitchers, tumblers, home food
containers and flatware.
epoxy resins
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Surface coating
Food cans：Two pieces with aluminium
Beverage cans：Three pieces with
epoxy-phenolics (合成樹脂)
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Polyvinyl chloride (PVC) (聚氯乙烯)：
Antioxidant and Inhibitor in
polymerization.
Thermal printing: A thin coating of leuco
(無色) dye.
Flame retardant: Printed circuit board,
Melamine (三聚氰胺)
• Produces crystals in urine when exceeds a
threshold.
• Stones, calculi in kidney (腎), ureter (輸尿
管), bladder.
• Industrially synthesized chemical for
laminates (薄片製品), coatings and
plastics.
Acrylamide (丙烯醯胺)
• is a chemical that is used to make
polyacrylamide materials.
• To flocculate solids in a liquid, soil
conditioner, a medium for electrophoresis
of proteins and nucleic acids.
• Polyacrylamide is not toxic. However,
unpolymerized acrylamide, which is a
neurotoxin.
• Is known to cause cancer in animals.
• Certain doses are toxic to the nervous
system of both animals and humans.
Persistent Organic Pollutants
(POPs)
• Chemicals of global concern due to their
potential for long-range transport,
persistence in the environment, ability to
bio-magnify and bio-accumulate in
ecosystems, as well as their significant
negative effects on human health and the
environment.
• mainly through the food we eat, but also
through the air we breathe, in the outdoors,
indoors and at the workplace.
• have been added to improve product
characteristics, such as flame retardants
or surfactants.
• The most commonly encountered POPs
are organochlorine pesticides, such as
DDT, industrial chemicals, most notably
polychlorinated biphenyls (PCB), as well
as unintentional by-products of many
industrial processes, especially
polychlorinated dibenzo-p-dioxins (PCDD)
and dibenzofurans (PCDF), commonly
known as 'dioxins‘.(戴奧辛)
• can lead, among others, to increased
cancer risk, reproductive disorders,
alteration of the immune system,
neurobehavioural impairment, endocrine
disruption, genotoxicity and increased birth
defects.