Food additives • 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 food-borne 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 • 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)
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
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) • 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.
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 farm-to-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) • 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 • Surface coating • Food cans：Two pieces with aluminium • Beverage cans：Three pieces with epoxy-phenolics (合成樹脂)
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.