David Peters Baran Group Meeting Food Chemistry: An Organic Perspective 10/5/19 Food Chemistry: TODAY’S CASE STUDIES The study of the chemical processes, both biological and abiotic, that occur in food substances during processing, handling, and consumption. - What was in Pepsi Muscle Milk® Jelly Belly® Blue? Food Chemists: - What exacty does solve problems of the above processes with the use of change of food Phil drink after the components, their ratios, and conditions gym? - What is in those jelly beans? Pepsi Blue® Goup Meeting DOES NOT Include: - in-depth coverage of “food chemistry” - concepts of food processing - discussion of nutrition WHY HAVE YOU EATEN THESE?! - any official health advice regarding diet H O O OH N O Goup Meeting Includes: S O - organic chemistry-related topics O H regarding food Na - major reactions during cooking - flavor addititives O - food coloring additives - vitamins and minerals (brief) EtO ● Foods largely in 3 categories: - other common additives & Me - carbohydrates EU Food Additive #’s: preservatives - proteins E100 to E199: color additives - fun & interactive chemical exploration - lipids E200 to E299: preservatives Major references for this group meeting: Should there be more?! E300 to E399: antioxidants & - an ever-expanding variety of new pH reg. - Nursten, H. The Maillard Reaction 2005. Cambridge, UK. The Royal Society chemotypes in food E400 to E499: thickeners, stablizers of Chemistry. Food and Drug Administration (FDA): & emulsifiers - Baht, S.V., et. al. Chemistry of Natural Products 2005. New York, NY, Springer. - sets guidelines, allowances and E500 to E599: anti-caking - Ullman’s Encyclopedia of Industrial Chemistry 2002. Wiley-VCH. tollerances for food products E600 to E699: flavor enhancers - Porter, J. Cooking for Geeks 2010, Sebastapol, CA. O’Rielly Media. - nothing is ever permanently approved E700 to E799: antibiotics - www.FDA.gov - “Natural”= original source is natural E900 to E999: miscellaneous - www.thegoofscentscompany.com - “Artificial” = source is not food-based E1000 to E1599: additional chem. - www.femaflavor.org - GRAS = generally recognized as safe David Peters Baran Group Meeting Food Chemistry: An Organic Perspective 10/5/19 The Maillard Reaction R R R OH OH O OH OH N OH OH HN OH OH HN HO R NH2 H HO HO HO − H2O OH OH OH OH OH OH OH O 1,2-enaminol Amadori product R OH N R OH O OH O OH O OH OH HN + H2O HO HO HO Me HO HO − H NR − H2O − H2NR 2 OH OH OH O OH O OH OH OH OH retro-aldol 2,3-enaminol − H2O HMF O O OH OH OH OH OH OH OH O O H HO Me HO Me HO Me HO HO Me − H2O O reductone O O OH O O OH O Other Possible Ketone/Aldehyde Products R R R O O O OH H H + amino acid + H2O H Me HO HO H O HO H Me Me − H O O H 2 N CO2H − CO2 N O Strecker O O Me Me Me aldehyde O O O H N Protein O HO HO HO OH 2 Protein H H Me intermediates N Protein Advanced above N NH2 N HO Glycation End O O HO HO CO2H NH Products Me HN N Protein N Protein H Me H Me H HO O OH O acetic & Type I formic acid polymer Me CO2H Me H X X X Stage II NH X = O, NR Colored NH2 CO2H 2 Intermediates NH2 CO2H R CHO & Polymer O N O N Amines − CO O NH2 2 X X X NH2 R NH R 2 X X Type II O polymer Acrylamide − NH3 O NH2 David Peters Baran Group Meeting Food Chemistry: An Organic Perspective 10/5/19 The Maillard Reaction Products: - term used for non-enzymatic browning of food products when amines and - produces heterogeneous polymers, volatile hydrocarbons, complex sugars are involved heterocycles - First described by Louis-Camille Maillard in 1912 while he is trying to make - the colored polymeric structures are called melanoidins peptides w/ amino acids and reductants - molar mass of polymers increases w/ temperature NOT time - The “reaction” is a mind boggling complex mixture of hundreds of reactants, - those above 3 kDa are generally insoluble reactions, and products − hard to study - melanoidins are 25% of the dry mass of coffee - schematic pathway of reactions proposed in - numerous other products can be benificial or detrimental to taste 1953 by John E. Hodge - carcinogenic/mutagenic compounds are genereally product of very high - divided the process into three stages temperatures and long reaction times I. Initial Stage (colorless) - acrylamide is result of high temp. and high concentration of asparagine A. amine-sugar condensation N O Me O O S HO B. Amadori rearrangement O Me Me O II. Intermediate Stage (light yellow) N H N O C. sugar dehydration O Me Me O Et D. sugar fragmentation S O HO O E. amino acid degradation N O Me III. Final Stage (highly colored) Me CO H F. aldol condensation O Me 2 G. adehyde-amine polymerization/ kahweofuran Cyclotene alapyridine heterocycle formation CO H 13 Hodge, J. Agric. Food Chem. 1953, 1, 928. N O N O N 2 OH [1- C] Starting materials: glucose O + - N-terminal amines, lysine side chain, or any other amine! proline - taste and smell mostly independent of sugars present O OH O OH OH - taste and smell dependent upon amino acids present - Strecker aldehydes maltoxazine - high levels of asparagine leads to high levels of acrylamide…(that’s bad) OH O OH O O O O O OH H2N H2N H2N O CHO O O OH = bread OH = meat/ OH = floral N N crackers O HN O Me Me SH (2 eq.) O O HO Progress: OH OH indolizinium-6-olate - becomes noticable ~154 ºC (310 ºF); cooking below this = no browning derivative - extent of reaction is depended upon time, temperature, pH and pressure - kahweofuran is in coffee; gives a roasted/smoky aroma O - pH can change the dominant reaction pathway - cyclotene is an important caramel odorant H2N R - 1,2-enol @ low pH; 2,3-enol @ high pH - effects product distribution - alapyridine increases sensitivity to sweetness ~16x - maltoxazine is in dark malt (stouts/porters); 10 mg/kg CO H - progress inhibited by bisulfite (used in food industry) - indoliziniums are extremely bitter and are undesirable O OH 2 David Peters Baran Group Meeting Food Chemistry: An Organic Perspective 10/5/19 acrylamide Caramelization Food Item (ng/g) NH2 N - term used for the non-enzymatic browning of sugars (alone) Potatoes (raw) n.d. - the process is a form of pyrolysis (irreversible thermal decomposition w/o Potatoes (boiled) n.d. Me N N Me combustion) Potato chips (fried) 3500 Potato chips (fried; overcooked) 13000 - products/reaction intermediates are very similar to those of Maillard Rection N Rye crackers 4000 - Begins ~150 ºC; Most noticable between 160-200 ºC (320-400 ºF) Breakfast cereal 1400 IQx - low temp. = light colors - most studied model is that of sucrose [highly mutagenic] Breakfast cereal (rice-based) 250 - high temp. = dark colors - medium temp. = rich flavors Proteins in Food: Yang, Energy and Fuels 2017, 31, 8291. - where we get the majority of our amino acids to turn into our own proteins HO - denatured proteins are a staple of human food HO HO O O OH - heat and pH and mechanical aggitation are major the factors in destroying O HO O OH ∆ OH native proteins before consumption HO HO HO OH - denatured/coagulated proteins change in texture, solubility, color, solublizing OH O OH properties, etc. (nearly all physio-chemical properties) HO OH OH - the change in properties is often utilized to create food properties Sucrose OH Fructose Glucose - eg.− properly denatured egg whites are emulsifiers of air OH ∆ ∆ - temperatures of cooking are determined by this process 1,4:3,6-dianhydro - eg.− people prefer meat with actin but without myosin HO OH glucopyranose O OH (DGP) Coagulated O OH Native Denatured Temperatures of Denaturation: O O Egg whites: 61 ºC (122 ºF) OH O OH HO O O Myosin: 50 ºC (122 ºF) O HO OH ∆ O Actin: 65.5 ºC (150 ºC) OH O O O OH levoglucosan O O (LG) Emulsifiers/Emulsification: O OH HO OH - emulsifiers act as the border between oil and water O OH HO HO O HO OH - help create and maintain the texture and from of food (eg. - ice cream) HO OH OH - Must be a ambiphillic molecule to affect its purpose O OH HO2C CO H O - generally carbohydrate or fatty acid esters O 2 O APP O Oleate O HO O O Me OH Common Emulsifiers: mO O O CMC O - soy/egg lecitin OH CO2H Me O O HO O Me - canola oil z OH HO HO − OH O O - carrageenan OSO3 O EtOAc O O x O O - polysorbates yOH polysorbate-80 O O HO O O - carboxymethylcellulose (CMC) HO O ∆ HO OH - guar gum (galactose/manose; branched) − OSO3 H AGF - xanthan gum (glucose/manose; branched) Carrageenan David Peters Baran Group Meeting Food Chemistry: An Organic Perspective 10/5/19 Artificial Sweeteners: Aspartame (and other “tames”) - delayed & lasting sweetness; slight bitterness - saccharin was the first (1884) - WWI and WWII helped its poularity - ~4 kcal/g - natural non-caloric sweeteners used throughout world previously - aspartame accidentaly discovered in 1965 O - originaly used mainly by diabetics and was taxed to protect sugar industry - solubility is highest at pH = 2.2 NHR - obesity & health affects of high-sugar diets has changed perspective/demand - maximum stability at pH = 4.0 MeO2C N H - sweetness is measured as a relative to dilute sucrose (~0.1g/L) - releases methanol and forms DKP - ADI: 50 mg/kg/day CO2H - all sweeteners have an asymtotic sweetness w/ concentration Aspartame: R = H Pb(OAc) -sweetness decreases after certain [conc.] OMe - many have “off tastes” - circumvented via blends of sweeteners 2 Neotame: R = t “Sugar of Lead” - other “tames” do not form DKP Bu - blended sweeteners are generally synergistic in sweetness - last two developed based on SAR Advantame: R = - may actually combat tooth decay OH Sweetness Intensity - most sweeteners are found by chance OMe Sucralose: Cl sucrose 1 - very little sweetness-SAR is known - 1976 discovery after discovery that halogenation O sodium cyclamate 35 increases carbohydrate sweetness Cl O OH stevioside 160 - melts at 125 ºC w/ decomposition acesulfame K 200 - 283 g/L solubility in water HO aspartame 200 - slight delay (blends help); lasting effect; generally OH O OH Me O rebaudioside A 250 good neohesper.