Unit 3 Flashcards
What is the smell associated with Cis-3-hexane-1-ol =
cut grass
Flavors have 2 modes of formation:
Thermal and Enzymatic (including fermentation)
One way of classifying compounds is based on their mode of formation; flavors can be generated wither ____________ or by ___________ during food processing.
naturally
heat treatment
Natural flavors are mainly ______________________ (phytochemicals) of the living tissue, formed during the natural growth cycle of the organism by the action of enzymes, whereas flavors produced by heat treatment is the result of thermal _____________ and oxidation of various food ingredients and their complex interactions.
secondary metabolites
degradation
The initial or primary precursors of flavors are the polymers found in food such as ________, ________, _________ and DNA which can undergo either enzymatic or thermal hydrolysis, to produce the intermediate precursors mainly dimers and monomers
proteins
lipids
polysaccharides
The type of flavor effect depends on the conditions of ____________ and the type of the initial precursors found in the particular food product
processing
In terms of composition, thermally generated flavors are richer in ____________ compounds compared to enzymatically produced flavors
heterocyclic
What are the 3 groups of reactions that account for most chemical transformations of intermediate precursors in food:
- Maillard & Strecker reactions (caramelization)
- Thermal decomposition
- Lipid oxidation
Name the possible carcinogen in red raw meat:
N-glycolylneuraminic acid
The raw meat has no particular appealing flavor, however, during various processes of cooking, the initial precursors in meat, produce water soluble intermediate precursors, such as :
- glycopeptides
- free nucleotides
- peptides
- amino acids
- amino-sugars
- free sugars
- fatty acids
The meat flavor, therefore, is the combined effect of the chemicals produced from the _____________ of these intermediates and the products formed from the amino-carbonyl interactions, such as between the reducing sugars and amino acids this reaction is known as the Maillard reaction or ________________ since it is responsible also for the brown color produced when foods are heated
thermal degradation
non-enzymatic browning
__________ and __________ (dipeptides) are by far the most abundant amino compounds in red meat followed by sulfur containing amino acids (_____________ and ___________). Nucleotides and lipids can also undergo either enzymatic or thermal hydrolysis to produce nucleosides and free fatty acids as important intermediate precursors
Anserine and Carnosine
Cysteine and cystine
What are the intermediate precursors in meat:
- Amino acid/sugars
- Sulfur amino acids
- Fatty acids
- Thiamine & Ribose-5’-phosphate
Thiamin (vit B1) generates different _____________ at different pH values
volatile degradation products
Vitamin B1 structure can be classified has a ________________
heteroatom (sulfur, nitrogen + oxygen)
T or F: Thiamin produces hundreads of degradation products
T
T or F: Heterocyclic compounds have very low threshold values
T
T or F: Sugars caramelize at relatively high temperatures
T
If the sugar reacts with an amino acid then the temperature at which the sugar will degrade gets much _________
lower
What is the key aspect if we want to obtain beautiful browning reactions?
The key is of course dehydration, too much water will not generate browning (concentrated solution is best for that)
Fructose is what type of sugar?
Keto-sugar
Glucose is what type of sugar?
Aldehyde-suagr
When sugars are put in solution, they get into the ________________ and they are then able to receive amino acids
open-ring
Process of ring opening and closing is called:
tautomerization
T or F: Glucose is the least unstable sugar (open form = 0.005%), ribose has like 20% open-form and reacts even more with protein within our body which is unfavourable
T
Strecker aldehyde =
CH3CHO
What type of reaction involves an amino acid reacting with 2 carbonyls?
The Strecker reaction
During a strecker reaction we generate an _____________
aldehyde (called strecker aldehyde)
T or F: aldehyde is part of a group of aroma chemicals that are intensively aromatic (with very low threshold value) so its valuable for food industries to generate lots of aldehydes in food processing conditions such as strecker aldehydes
T
Acetaldehyde (CH3CHO) is the strecker aldehyde of _________
alanine
Formaldehyde (CH2O) is the strecker aldehyde of ____________
glycine
T or F: strecker aldehydes have special aroma properties
T
The first step involved in the processing of stimulant beverages, is fermentation and _____________ giving rise to flavor precursors. This step is followed by firing and drying in driers. In the case of coffee, another step of _______ (above 180C) is carried out during which primary and intermediate precursors undergo important thermal degradations. These Maillard reactions lead to the formation of a great number of volatile substances responsible for the coffee aroma (around _______ components)
enzymatic degradations
roasting
700
Fermentation in tea =
enzymatic oxidation of tannins
letting the tea leaves stay in a moist environment (controlled chambers) in which enzymes are activated, those enzymes will promote __________ of phenolic components and form polyphenolic structures and dimeric structures
oxidation
Tea and coffee are very similar in character both in their composition and in the various steps leading to the production of corresponding beverages. They contain ___________ of the xanthine group such as 1,3,7-trimethylxanthine (caffeine) and 3,7-dimethylxanthine (theobromine) that impart a ___________ to the beverage
alkaloids
bitter taste
Caffeine is the main component of __________ and __________, whereas theobromine is present in relatively large amounts in tea
coffee and tea
What are some aroma precursors in tea: (3)
- amino acids
- carotenoids
- lipids
For teas that require oxidation, the leaves are left on their own in _________________ room where they turn progressively _________. This is accompanied by agitation in some cases. In this process the chlorophyll, carotenoids, lipids in the leaves are enzymatically broken down, and its _________ are released or transformed . This process is sometimes referred to as fermentation on the tea industry.
climate-controlled
darker
tannins
The tea producer may choose when the oxidation should be stopped, which depends on the _____________ in the final tea as well as the weather conditions (heat and humidity). For light oolong teas this may be anywhere from ______ % oxidation, in darker cooling teas _____ and in black teas _____ oxidation
desired qualities
5-40
60-70
100
The black tea aroma is a typical example of the important changes induced by ______________. Three groups of substances are involved as flavor precursors: ____________________. Other components of biological matter which contribute to thermal degradation, may also act as precursors.
- fermentation/oxidation
- polyphenols (mainly flavanols)
- carotenoids
- unsaturated fatty acids (linoleic acid)
The ____________ oxidation constitutes one of the important factors contributing to tea flavor.
carotene
Name some carotenoids present in fresh tea leaves:
- theoxanthin
- lutein
- violaxanthin
- ionone
The analysis of the black tea aroma reveals the presence of a great number of substances arising from carotene oxidation such as: play a preponderant role in black tea aroma
- dihydroactinidiolide
- theaspirone
T or F: enzymatic oxidation reactions are more controlled whereas thermal oxidation reactions produce a wide variety of products
T
The carbonyl compound formation under the action of ___________ upon C-18 unsaturated fatty acids of lipids contained in leaves and fruits of various plants has been the subject of many studies
lipoxygenase
Researchers using tea leaf chloroplasts showed that 14C-labelled linolenic acid is converted into ________________________. It is described as having a coarse vegetable-like aroma
12-oxo(E)-dodecen-10-oic acid
(alpha-amino acids and sugars in tea): The changes occurring during the fermentation process may account for the formation of ____________________ by amino acid degradation
aldehydes
What is the most common amino acid in tea:
Theanine (N-ethyl glutamine)
During the next firing step (tea), sugar and amino acid interactions are responsible for the formation of the following heterocyclic compounds:
- furans
- pyrroles
- pyridines
- pyrazines
- oxazoles
- thiazoles
- quinolines
T or F: In the solid extract of tea, 6.52% of total sugars are present including fructose (2.0%), glucose (1.9%), sucrose (1.6%), meso-inositol (0.5%), raffinose (0.3%) and maltose (0.1%).
T
___________________, these two are important reactive compounds which have been found to be present in tea aroma, contribute to the formation of sulphur-containing heterocyclic compounds (thiophenes, thiazoles, dithiolanes, etc)
hydrogen sulphide and dimethyl sulphide
________________ which accounts for 7% of the solid extract, is not practically affected during the preparation of the black tea. On the other hand, it has a significant effect on the astringency taste of the infusion due to its complexation
Caffeine (alkaloids)
_________________ on the black tea polyphenols are the specific sites involved in the complexation with caffeine
The galloyl groups
What is the most important dimeric structure (polyphenol) in tea:
theaflavins
Compounds called catechins are the building blocks of ____________________; they are oxidized to produce theaflavins and thearubigens
black tea polyphenols
T or F: theaflavins comprise 3-5% of black tea and are responsible for its red-orange appearance
T
T or F: The compounds in tea derived from catechins can have antioxidant effects on the body - research has shown these could have beneficial effects on cardiovascular health
T
It has been suggested that ____________ proteins in milk could bind to polyphenols and as a result prevent their antioxidant effects
casein
The composition of roasted coffee not only varies according to the origin of green coffee but also the technique used, the degree of roasting and the _______________
roasting time
___________________ are responsible for modifications which lead to the emanation of off-flavors or a deterioration of aroma itself
seed storage and humidity
What are the main chemical groups of precursors involved during coffee roasting:
- carbohydrates/sugars
- proteins/amino acids
- amines/tryptamines
- phenol acids
- trigonelline
- non-volatile acids such as citric acid
Carbohydrates and sugars are equivalent to ___________ of the green coffee bean weight. These carbohydrates are highly polymerized water-soluble molecules whose components are ___________ and ___________
40-50%
mannose and galactose
____________________ do not appear to be susceptible to roasting, and their hydrolysis is difficult to achieve
Galactomannoses
T or F: during the roasting process the amount of galactose and arabinose which result from thermally degradable polysaccharides,_________________- whereas the amount of mannose ___________
degreases
increases
Sucrose in green coffee accounts for ___________% of its weight. This constituent is the most susceptible to heating
6-10
In the course of the roasting process, the reducing sugars participate in the various steps of the ________________________. It is worthy to note that they also undergo cyclodehydration reactions, in the course of which, furfural along with _______________ are formed from pentoses and hexoses respectively
- Maillard reaction
- 5-hydroxymethyl derivative
Out of 17 green coffee amino acids, __ were also proved to be totally destroyed during roasting
5
What are the 5 amino acids destroyed during coffee roasting:
- arginine
- cysteine
- lysine
- serine
- threonine
What are 4 amino acids that see their concentration increase during coffee roasting:
- glutamic acid
- leucine
- phenylalanine
- proline
The three polyamines (3): which are present in green coffee are either destroyed or transformed during the roasting process
- putrescine
- spermine
- sperminidine
Putrescine (polyamine in green coffee) is converted into:
pyrrolidine
T or F: hydroxytryptamines have been identified in green coffee wax, these amines possess ___________________ towards lard. They are also susceptible to temperature and to roasting time
anti-oxidizing properties
Coffee lipids break down into:
glycerides + fatty acids
The saponifiable fraction of coffee lipids contains:
- linoleic acid (47%)
- palmitic acid (32%)
- oleic acid (8%)
The unsaturated aldehydes in coffee that play a prominent olfactory role in coffee aroma are obtained from the oxidation of _____________________
unsaturated fatty acids in C-18
Coffee oil contains 2 diterpenic alcohols:
- kahweol
- cafestal
What are the three important phenolic acids in coffee: (they breakdown during roasting into important aroma components)
- chlorogenic acid
- quinic acid
- caffeic acid
Among the coffee phenol acids which account for 7% of the weight ______________ is the most significant
chlorogenic
T or F: Trigonelline is used as an indicator for different types of coffee origins and sometimes it will be used in quality control measures
T
T or F: trigonelline is easily degraded by heating at 180-230C for 15 mins in a sealed tube. This reaction gives rise to pyridine, pyrrole, catechol
T
Acidity plays an important role in the ____________ of coffee beverages
flavor acceptance
During the coffee roasting operation ____________ acids are partly degraded
citric + malic
Wine is mostly ___________ + ______________
water + ethanol
Catechins can polymerize into _____________
tannins
T or F: champagne is made from similar grapes as white wine
T
Modern cacao processors _______, _________ and ________ cacao beans. Then they grind the beans, forming a ______________, a thick, brown liquid that solidifies near room temperature. About 55% of the liquor is _______________, a fat consisting of various triglycerides with mainly oleic acid, stearic acid, and palmitic acid side chains.
ferment dry roast cacao liquor cacao butter
Fat levels in the liquor are too high for making ____________ and too low for making so called eating chocolate. So manufacturers separate the cacao butter from the liquor and use it to raise the fat content of eating chocolate. The separation process leaves behind solid cacao. That material is pulverized and used to manufacture drinking chocolate , cocoa powder, and chocolate flavoring used by bakers and candy makers.
cocoa powder
Beer taste different because of the __________________ added at the mashing step
alpha acids
T or F: the more hops added, the more bitter the waste will become
T
Beer contains: alpha acids, beta acids, _________, _________
essential oils
esters
Name the six steps in the beer making process:
- milling
- mashing
- brewing
- cooling
- fermenting
- maturing
Grapes contain lots of flavor compounds such as ______________
terpenoids
T or F: red wine has a higher fermentation temperature because you want to have enough time to extract the red pigments, that’s they we leave the skin of the grapes when we make red wine
T
Some alcoholic beverages are fermented but also distilled some just distilled like:
Gin
T or F: Wine and beer are fermented but not distilled
T
Lactone in wine is a ________________
cyclic ester
T or F: Terpenoids contained in grapes depend on the type of grape, the soil where the grapes were grown, time, temperature, aging, what type of wood
T
Process of wine making: the pressed grapes (_____) are inoculated by ______ such as Saccharomyces Cerevisiae and are let to ferment (in vats) for 10-15 days at 10-21C for ___________ and several months for ______ and 5-7 days at 25C for _____. The process is termed _________
must yeasts white wine ice wine red wine racking
The temperature of fermentation is important for wine making. Cool fermentation is preferred for _______ to reduce the activity of wild yeast and bacteria and to minimize the loss of volatiles such as alcohols; on the other hand red wine requires _________________ to aid in the extraction of color pigments from the skin of the grape.
white wine
higher temperatures
T or F: During fermentation, the skin is not removed during the making of red wine
T
The fermentation is continued until pectic substances precipitate and they are removed by __________. The wine is then matured or aged for ____. Vintage wines are aged for more than ____ years
pectic enzymes
1-2 years
20
T or F: white wine only requires primary alcoholic fermentation
T
In red wine there is a ________________ (malo-lactic fermentation)
secondary alcoholic
T or F: with the primary fermentation we want to convert all the sugars in the grape juice into carbon dioxide, ethanol and many other important aroma chemicals
T
Red wine is kept in __________
barrels
What is the goal of the malo-lactic fermentation:
convert malic acid (very harsh) into lactic acid (milder acid)
Aging is normally done in wooden ________ from oak tree, oak also contains many important aroma compounds, aging gives the time for other reactions to happen such as reactions involving sugars, amino acids, Maillard reaction, oxidation reactions
barrels
Limousin oak =
Troncais oak =
open grain
tight grain
What are the three main sources of flavor compounds in the wine:
- grapes
- fermentation process
- aging (by Maillard type reactions and/or extraction from wood)
Primary fermentation converts sugar into:
- ethanol (48%)
- carbon dioxide (49%)
- other (3% alcohols, aldehydes, esters)
T or F: The type of wood in which wine is stored or aged can also contribute to the overall flavor of the wine
T
Most of the 300 or so flavor compounds identified in different wines are formed during _______________
fermentation
Extraction of ________, vanillin, oak lactone and other phenolics from the wood (during the first 3 years). Slow oxidation of tannins and other components due to gradual exposure to oxygen coming in through the pores of the wood (during the fourth, fifth and sixth years)
tannins
Alcohols formed during fermentation acccount for _____ of all aromatic substances (500 mg/l). They are present in slightly higher concentration than their perception threshold and they are responsible for the _____ taste of wine.
50%
sweet
_________ contains on average 1.5g/l of alcohols and in whisky _____ and in rums _____
Cognac
- 0g/l
- 6g/l
______________ plays an important role, it gives to the wine its hard character
ethyl acetate
Esters are also produced by fermentation. Among more than 50 esters reported in wine aroma, three of them are of more abundant:
- ethyl acetate
- ethyl lactate
- ethyl octanoate
T or F: tartaric acid is responsible for the crystals
T
High acidity level in wine (pH from 2.8 to 3.8) is linked to a relatively strong acid found in grapes:
tartaric acid
Lactic acid bacteria transform tartaric acid and other constituents such as sugars into ___________
acetic acid
Sometimes _____________ precipitates on storage of wine (also known as wine diamonds)
potassium tartarate
The hardness of red wines depends on the level of _____ acid and ______________, when present in excessive amounts, they reduce the sensory qualities of the wine.
acetic
ethyl acetate
Among amino acids found in wine, 5 predominate:
- asparagine
- aspartic acid
- glutamine
- glutamic acid
- alanine
- proline
The presence of _____ substituted pyrazines in some alcoholic beverages such as rum may be explained by a Maillard reaction between amino acids and sugars during aging
alkyl
All gins must be primarily flavoured by ___________
juniper berries
What is compound gin:
In compound gins, the botanical ingredients are added to a spirit without any redistillation
What is pot-distilled gin:
Neutral spirit is distilled, botanical ingredients are soaked in it and it is then redistilled
What is column-distilled gin:
column distillation creates a highly concentrated spirit which is then redistilled with botanicals
What is the starting material of rum:
sugar cane / molasses
Dark rum comes the ____________ of sugars
caramelization
T or F: in vodka, coumarin is responsible for the strong smell, it is also toxic so it has to be controlled
T
T or F: the value and taste of whisky is mostly affected by ageing (more than with other alcohols)
T
What are the 3 sources of aroma compound in distilled spirits
- raw materials
- alcoholic fermentation
- ageing
Fermentation of CHO not only leads to the main products ethanol, glycerol and CO2, but also to a typical fingerprint of volatile metabolites at relatively low levels like aldehydes, ketones, higher alcohols, organic acids and esters which are called:
fermentation by-products
carbonyl compounds have a _______ threshold value compared to alcohols in ethanol solution
lower
Ageing of distilled spirits is an important technological step to ________________ since fresh distillates are often characterized by a raw, pungent odor and taste.
improve the flavor
Different components of a fresh distillate may _____ during the maturation period, which is favored by a high ethanol content of the distillates to be stored. Thus, the concentrations of ethyl esters of fatty acids __________ during ageing, but the concentrations of esters of other alcohols decrease by ___________________________. Further reactions during ageing are the evaporation of ___________________ or their reaction to form acetals
react
increase
transesterification
aldehydes
By storing distillates in wooden casks, volatile aroma compounds whishky lactone, vanillin, eugenol and other ____________________ migrate from the toasted wood into the distillate. These compounds are responsible for the characteristic oak wood and vanilla-like flavor.
phenolic compounds
What is the aroma compound of oak wood with the highest threshold value:
Furfural (smoky almond)
What is the aroma compound of oak wood with the lowest threshold value:
Guajacol
___________________ and _____________ compounds of wood change the color of the distillate and contribute to an up-rounded flavor.
Semi-volatile
Non-volatile
T or F: aged products normally have a darker color due to polymerization
T
The wooden barrels which are permeable allow air to pass and cause ethanol to __________; thus, the ethanol content decreases and the aroma gets more intense, complex, and concentrated. Also harsher aroma constituents are removed and the spirit changes to mellow
evaporate
The period of maturation depends on the ______ of the casks used, the alcoholic strength, as well as the temperature and humidity in the warehouse which leads to a __________ flavor
size
smoother
For the production of neutral highly rectified distilled spirits like vodka, grain spirit, or white rum, the _________________ is of utmost importance to the flavor
quality of the water
T or F: fatty acids play ar big role in the taste of tomatoes
T
Currently, 176 components are identified in tomato aroma in its various preparations (canned, juice, ketchup). Although few heterocyclic compounds contribute to this aroma, one of them is responsible for its _________ flavor. This distinctive heterocyclic compound is 2-isobuthylthiazole
peculiar
Tomato lipids are ______________, ________________, and ___________ high a high linoleic and linolenic acid content. These unsaturated fatty acids are generated through the action of acylhydrolases and phospholipases.
phospholipids
galactolipids
triglycerides
Carbonyl compounds present in tomato aroma can arise from the enzymatic degradation of amino acids during the maturation process. For example leucine yields:
3-methyl-butanal and 3-methyl-butanol
___________________ identified in the tomato aroma seems to be related to the thermal degradation of B-carotenes
B-Ionone
The acidity of tomato is due to certain mineral and organic acids such as:
- acetic acid
- lactic acid
- malic acid
T or F: Tomato possesses a high vitamin C (ascorbic acid) content (10-30 mg/100g)
T
Over 200 aroma compounds have been identified in differently processed milk, some of these compounds have their origin in the raw milk and some of them are formed during processing due to the degradation of the main precursors found in raw milk such as:
- fats
- carbohydrates (lactose)
- proteins
In milk, fats, carbs, and proteins undergo 2 types of transformations:
- chemical such as oxidations
- biochemical with the participation of the enzymes and the microbial flora contained in the milk or by exogenous bacteria and microbial flora such as during preparation of cheese and yoghurt
The most important precursor responsible for the production of milk aroma is the ________
lipid
Milk triglycerides are hydrolyzed by bacterial lipases to produce _________________ which in turn are oxidized into different carbonyl compounds, among them, many _______________ responsible for the milk aroma, other important carbonyl compounds include ______________ (responsible for the metallic aroma)
free fatty acids
methyl ketones
oct-1-en-3-one
__________ and _______ lactones are formed by the thermal oxidation of fatty acids in milk
gamma and delta
Characteristic odor of cream =
(Z)-4-heptenal
