Lecture 11

Lecture 11 - FST 1 – Main topics – Lecture 11 Food...

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Unformatted text preview: FST 1 – Main topics – Lecture 11 Food Additives – Preservatives ‐ Antimicrobials: prevent spoilage from bacteria, molds, yeasts ‐ Others: : ‐ slow or prevent changes in color, flavor, or texture ‐ delay lipid oxidation (antioxidants) ‐ maintain freshness Antimicrobial compounds may inhibit the growth (Bacteriostatic and Fungistatic) or kill (Bactericidal and Fungicidal) microorganisms. At the levels commonly used, most preservatives stop the growth of microorganisms. Examples of preservatives are salt (oldest preservative known) and some organic acids: Organic acids Found in Active against Acetic acid Vinegar Bacteria, yeasts Benzoic acid Cranberries Fungi Lactic acid Fermented foods Bacteria Propionic acid Swiss cheese Yeasts, molds, some bacteria Propionic acid is frequently used as antimicrobial agent in baked goods. It may be added directly to bread dough; it has no effect on baker’s yeast. Foodborne Illnesses: Intoxications and Infections Foodborne illness: disease caused by consuming contaminated foods or beverages. It can be infections or of toxic nature. More than 250 different foodborne diseases have been described. Every person is at risk of foodborne illness. Foodborne INFECTIONS are caused by pathogens (disease –causing microorganism: bacteria, parasites, viruses). Foodborne INTOXICATIONS are caused by toxins or chemicals that have contaminated the food. Throughout history humans learnt to recognize what was safe to eat (FOOD), and what could be harmful to the body (POISONS). Poison or Toxicant: chemical that is harmful to living organisms. Food Toxicology: study of toxicants found in foods Paracelsus (1493 –1541) “all substances are poisons”. The right dose differentiates a poison and a remedy” Potential Sources of Toxicants in Food Nutrients Naturally occurring food toxicants Contaminants Chemicals intentionally added to food Chemicals formed during food preparation or processing Overall, when obtained directly from natural foods, nutrients do not pose any significant health problems. Some exceptions are: vitamin A, vitamin D. Toxicity symptoms due to consumption of vitamin A in excess include: birth defects, hair loss, skin disorders, bone pain, fractures. Prevention: limit consumption of vitamin A rich foods (such as liver), avoid megadose vitamin supplements. Naturally occurring food toxicants ‐ Plant toxins. Two examples: Oxalic acid; Cyanogenic compounds Rhubarb leaves contain toxic levels of oxalates; consumption may result in kidney damage. Cyanogenic glycosides : naturally occurring compounds that release hydrogen cyanide (highly toxic ) when broken down. Symptoms of intoxication are: mental confusion, muscular paralysis, respiratory problems. Examples of plants containing cyanogenic glycosides are cassava roots, lima beans. ‐ Animal toxins. Ex.: Ciguatera fish poisoning. This illness is caused by eating fish that contain toxins, such as ciguatoxins, which are produced by marine microalgae. Many finfish can accumulate these toxins through their diet. Usual sources are barracuda, grouper, snapper, but more than 400 fish species are affected. Symptoms of ciguatera fish poisoning include nausea, vomiting, neurological symptoms, tingling fingers or toes. Ciguatera has no cure. Symptoms usually go away in days or weeks but can last foryears. Contaminants: pesticide residues; animal drugs (hormone and antibiotic residues); environmental chemicals. Many pollutants can contaminate food production areas: animal and industrial waste; human sewage; other runoff. Methyl Mercury is an environmental contaminant; it is toxic to the nervous system. Fish absorb methyl mercury from the environment. Predatory fish can accumulate high levels of the toxicant; ex.: swordfish, king mackerel. High levels of mercury have also been found in canned white, or albacore. However, canned light tuna (skipjack tuna, a medium sized tuna) is generally safer. Melamine is an industrial chemical widely used. In 2007, melamine was found in pet foods (containing imported ingredients) sold in the United States. A large number of pets died due to kidney failure. In 2008, powdered baby formula tainted with melamine sickened about 300,000 Chinese babies, many with severe kidney problems. Some contaminants can be introduced to food through migration from food packaging. An emerging contaminant is bisphenol‐A (BPA). BPA is used to make some types of plastic bottles, such as baby bottles, and also in the lining of most food cans. Among many adverse effects, BPA may cause developmental and reproductive problems. Recently the NIH (National Institutes of Health) reported concerns that BPA can affect the brain, behavior and prostate gland in children Foodborne intoxication can also be associated with microbial toxins, such as toxins produced by the bacterium Staphylococcus aureus. Foodborne INFECTIONS (see reading 6 listed below). The leading cause of bacterial foodborne illness is Salmonella, and among foodborne viral infections, Noroviruses. Readings 1. McGee p. 258‐261 (Toxins in some fruits and vegetables; Fresh produce and food poisoning) 2. McGee p. 395‐306 (Cassava) 3. McGee p. 367 (Rhubarb) 4. McGee p. 184‐187 (Health Hazards) 5. Mercury in fish (pdf file posted on the course web page) 6. Food Safety‐USDA (pdf file posted on the course web page) ...
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This note was uploaded on 08/16/2011 for the course FST 001 taught by Professor Charlesf.shoemaker during the Winter '10 term at UC Davis.

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