CHEM 181 Study Guide - Winter 2018, Comprehensive Midterm Notes - Zinc, Wright Brothers, Wisconsin
12 Oct 2018
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CHEM 181
MIDTERM EXAM
STUDY GUIDE
Fall 2018
CHEM 181 – World of Chem: Foods
Unit 3
Topic 8: Chocolate and Weight Control
Lesson 1: Chocolate
Video 1
❖ Chocolate known as the foods of the gods
❖ Both science and lore associated with chocolate
❖ Study by Confectionary Association of Canada 1995: did they prefer chocolate or sex?
o 30% of men and 38% of women in Canada
o Quebec: 74%
o Nova Scotia: 20%
❖ More than 500 chemicals in chocolate such as phenylacetic acid, dimethylsufide, 2-methoxy-4-
methyphenol
❖ What we like about chocolate is less the taste and more the texture
o Melting point of cocoa fat is 36 degrees Celsius, one degree below human body
o Chocolate melts as soon as you put it in your mouth → sensation people enjoy
❖ “edish otaist aed ooa theooa aao eaig food of the gods
o Aztecs in Mexico would offer preparation based on cocoa as a liquid in a gold goblet
(only to be used once) to satisfy the gods
o Not easy to do since cocoa is difficult to dissolve
o Aztec term for cocoa is xocoatl which means bitter
o Needed to beat cocoa for long periods of time to get it to disperse liquid
❖ Cocoa was very valuable and used as a currency
o Spaniards came to Mexico and found cocoa beans in vaults indicating their value
❖ Spaniards believed cocoa had aphrodisiac properties, and so sent back to Spain under this
pretence
❖ Became popular in Europe as a beverage
o Bitter and so was mixed with sugar, vanilla, and cinnamon
o For most of its history, cocoa was not eaten, it was drunk as a beverage
❖ Today, most chocolate is eaten
o Canadians, according to 2004 data, eat roughly 4kg/9lbs per person per year
Video 2
❖ Cocoa flower hangs on the side of cocoa trees and gets converted into cocoa pods growing
throughout the tree
❖ There is no season for cocoa growing, grows year-round
❖ Big names in cocoa are Forastero, Trinitero, Criollo
o Cocoa/chocolate aficionado believe the best of all cocoa is Criollo
❖ When the cocoa pod reaches maturity it is picked and split open
o Cocoa nibs surrounded by white mucilage will be exposed
❖ Pod is left open to allow cocoa seeds to ferment
o Sugar → alcohol → acetic acid → esters
o Adds flavor
❖ Cocoa producers 2011:
o Ivory Coast – produces 1.51 metric million tons → top producer, quite far ahead others
o Ghana – 1.03
o Indonesia – 0.44
❖ Social aspect of cocoa production: Ivory Coast and others use child labour
o Children from African countries shipped by parents to camps where they pick cocoa and
work on it
o Can buy fair trade cocoa to provide the best deal for producers
❖ Once fermentation process is complete, cocoa seeds/beans left to dry out in sun
❖ Then the beans are roasted which enhances the flavor
o Reaction occurring is the Maillard reaction, a browning reaction
o Involves combination/reaction between amino acids and sugars to give taste
o Reaction named after French chemist Monsieur Maillard
❖ The result is much darker beans which then need to be shelled
❖ Produces cocoa nibs which are crushed in special machines to make chocolate liquor (non-
alcoholic) which is the basis for the making of chocolate
Video 3
❖ Taste of chocolate liquor similar to that of baking chocolate where nothing is added
❖ Chocolate by itself is very bitter and has high fat content
❖ In early 19th century the van Houten family looked into improving properties of chocolate
o Casparus van Houten separated cocoa powder from fat in a compressor
o One on side came out cocoa cakes (where cocoa powder is found – responsible for
taste), and on the other cocoa butter
➢ Cocoa butter is like butter and it is clear in terms of colour (cocoa cakes have
colour of chocolate)
➢ Melting point close to that of the body → used in lipstick so that it melts while
being applied, also used for medicinal purposes to deliver drugs rapidly
❖ Cocoa cakes are compressed cocoa powder → very bitter and not dissolved easily
❖ Conrad van Houten (1828) introduced a process to improve cocoa cake properties → the Dutch
process
o Treat natural cocoa with an alkali and convert into Dutch processed cocoa
o Acid is neutralized
o Natural cocoa much lighter than Dutch processed cocoa
o Acidity is cut down and solubility is increased → much easier to make drinks from
processed cocoa
o Heshes ooa is atual ooa
❖ First edible chocolate developed by Englishman J.S. Fry (1847) (NOT Swiss or Belgian)
o Had the idea to blend cocoa and variable amount of cocoa butter under controlled
conditions
o Bakes hoolate, i otast, ol deied fo hoolate liuo
❖ At same time English company Cadbury was making chocolate
❖ It was in Switzerland that milk chocolate was first produced
o Daniel Peter (1876), who owned a chocolate factory in Switzerland, had idea of cutting
down bitterness of chocolate further
o Had idea of adding milk
11
CHEM 181 Full Course Notes
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Document Summary
Chocolate known as the foods of the gods. Both science and lore associated with chocolate. Study by confectionary association of canada 1995: did they prefer chocolate or sex: 30% of men and 38% of women in canada, quebec: 74, nova scotia: 20% More than 500 chemicals in chocolate such as phenylacetic acid, dimethylsufide, 2-methoxy-4- methyphenol. Cocoa was very valuable and used as a currency: spaniards came to mexico and found cocoa beans in vaults indicating their value. Spaniards believed cocoa had aphrodisiac properties, and so sent back to spain under this pretence. Became popular in europe as a beverage: bitter and so was mixed with sugar, vanilla, and cinnamon, for most of its history, cocoa was not eaten, it was drunk as a beverage. Today, most chocolate is eaten: canadians, according to 2004 data, eat roughly 4kg/9lbs per person per year. Cocoa flower hangs on the side of cocoa trees and gets converted into cocoa pods growing throughout the tree.
