Chemistry 106 University of Nebraska Spring 2009

1. Chemistry 106 University of Nebraska Spring 2009 MONDAY 30 March 2009

2. What do Additives do? • They improve or maintain the quality of foods • Functions of food additives • antioxidants • Colorings/dyes • Flavorings • Preservatives • Emulsifiers (keeps from seperating) • Stabilizers and Thickeners (adds quality)

3. Additives • Free-radicals atom or molecule with an unpaired electron • Fat or oil (or any type of compound) + oxygen free radicals + other products (responsible for rancidity) • **fats and oils particularly susceptible due to double bonds

4. Additives • Antioxidants • Compounds that prevent packaged, processed foods from becoming rancid due to oxidation of fats and oils which form harmful free radicals • Two most common: **recognize for test Butylated hydroxyanisole (BHA) Butylated hydroxytoluene (BHT) - interrupt free-radical oxidative reactions by contributing hydrogen from the phenolic hydroxyl groups - BHT & BHA become STABLE free radicals which do not initiate or propagate further oxidation of lipids.

5. Additives • Another important antioxidant: EDTA(ethylenediaminetetraacetic acid) • removes small amounts of metal ions from food (these ions cause catalytic oxidation – leading to food spoilage and “off flavors”) • EDTA molecule wraps itself around metal ions like a crab (the combination of the compound with the metal ion is called a chelate (from the Greek word meaning crab’s claw)) • In the act of holding the metal the chelating agent becomes a sequestrant (to remove or set apart) • EDTA (and like compounds) used in fats and oils, for protection of vitamins, and to reduce discoloration (browning) of many foods

6. **recognize for test!!! EDTA uses: -textiles-prevent dyes from being oxidized -cosmetics-keep fats and oils from oxidizing -food -paper-prevent white paper from discoloring

7. Additives • Colorings • Most foods are unlikely to reach grocery shelves at their peak in color • In 1900 more than 80 different synthetic dyes were used in foods to enhance natural colors • In recent years, more natural coloring compounds such as carotenoids (yellow-red) and anthocyanins(red-blue) are being used (about 30 today) • Beta-Carotene (a carotenoid) provides color as well as being an antioxidant and converted to vitamin A • Natural food colors are listed as “artificial color” while synthetic dyes are listed as an F, D, & C colorant.

8. Additives • Flavorings • Many used today are synthetic versions of natural flavorings (aldehydes, ketones, esters) • Some flavorings are simple with only a few components – others are very complex (tarragon contains over 80 different chemicals) • Why aren’t some man-made flavorings as “good” as their natural counterparts? – synthetics have only the essential compound(s) • Synthetic vanilla flavoring contains the aldehyde vanillin, natural vanilla contains the aldehyde along with several other compounds.

9. Additives • Flavorings • Many fruit flavorings are esters – banana, pear, pineapple, • Some are very strong (capasaicin-habanera pepper) • Some actually can cause cancer (safrole-found in tree that provides flavor for rootbeer)

10. **don’t need to recognize for test!

11. Additives • Flavor enhancement • Flavor enhancer mode of action • Synergistic: cooperative action of two different substances such that the total effect is greater that the sum of each effect alone • potentiation: substance that does not have an effect by itself but exaggerates the effects of other chemicals

12. Additives • Flavor enhancement • Monodoium glutamate (MSG) • A new taste (sweet, sour, salty, bitter) – savory taste • A synergistic compound • Table salt (NaCl) • Used for centuries to enhance flavor • A synergistic compound • Nucleotides • Acts as a potentiator (have no taste, but enhance taste of other compounds) • Commonly used on meats

13. Additives • Preservatives • Most are synthetic and have very low toxicity to humans • Most are used to inhibit growth of mold and other microorganisms • Sodium or calcium propionate – baked goods • Sodium benzoate – canned goods • Sodium nitrite – cold meats • Sorbic acid - cheese

14. Additives • Stabilizers • Humectants – keeps foods moist by attracting atmospheric water • glycerine (used in coconut) • Glyceryl monostearate (used in marshmallows) • Anticaking agents– keep finely powdered food dry and free flowing (added to hygroscopic (foods that tend to absorb water by themselves) foods) • Silicon dioxide and calcium silicates (used in salt, baking powder, etc)

15. Additives • Thickeners • Used in liquids to give a thicker texture and feel (pudding, salad dressing, etc) • Examples • Gum arabic – from the acacia tree • Starch – isolated from corn • Xanthan gum – complex carbohydrate from corn

16. Additives • Emulsifiers • Compounds that allow polar and nonpolar mixtures to remain mixed without separating • Examples • Xanthan gum – used in many salad dressings (thousand island) • Mono and diglycerides– used in peanut butter

17. Additives • pH Control • Weak organic acids (such as acetic acid) • Acid salts (Na2HPO4) • Enhance flavor and preserve • Buffers added to adjust pH (potassium tartrate)

18. SodiumNitrite – a preservative • Risk of use in cold meats: may cause cancer • Steps • NaNO2 Na+ + NO2- • NO2- + HCl  HNO2 + Cl- • HNO2 + protein (forming amines during digestion)  nitrosamine • Nitrosamines are carcinogenic

19. SodiumNitrite – a preservative • Benefits: effective in preventing growth of Clostridium botulinum which produces the botulinum toxin • Botulinum toxin is the worlds most potent toxin, natural or manmade

20. SodiumNitrite – a preservative • Only about 1/3 of nitrite salts in our stomach come from the additive if we eat cold meat • Bacteria in stomach convert sodium nitrate in fresh fruits and vegetables into nitrites • So, eliminating it from the diet doesn’t mean eliminating it altogether • Some fresh fruits and vegetables also contain compounds that react with nitrous acid to inhibit formation of amines.