Chapter 7 Flashcards
The energy content of a food can be considered as
The amount of energy that would be produced if the body converted it to CO2+H2O by aerobic metabolism
How the energy content of food is measured
The heat released is termed the heat of combustion and can be
measured in a bomb calorimeter
What is one calorie
calorie = amount of heat required to increase the temperature of 1
gram of H 2 O by 1 C
What is the conversion betwen calories and joules
1 J = 0.239 cal 1 cal = 4.184 J)
Food calories are usually measured in ___
Kilocalories
Why measuring food by burning in a bomb calorimeter is not reliable and give the example
because it does not take into
account digestibility .+ if you take apples, you will need to take seeds, because we usually do not eat them, as well as remove the peel maybe, etc.
Combustion of 1 g of cellulose produces the same amount of
heat as combustion of 1 g of starch whereas the human body
completely hydrolyzes starch to its glucose subunits but cannot digest
cellulose.
If the calorimeter is not the reliable source of info about caloric properties of food, so how it is measured
standard values for the heat of combustion of each class of macronutrients have been adopted.
Accordingly, a common method is
to use analytical chemistry to
determine the amounts of each of the macronutrients in a food
sample and then multiply each amount by the corresponding standard
value.
Carbohydrates: calories and joules
4 kcal
16.7 kj/g
Protein: calories and joules
4 kcal/g
16.7 kj/g
Fat: calories and joules
9 kcal/g
37.7 kj/g
Alcohol: calories and joules
7 kcal/g
29.3 kcal/g
Organic acids :calories and joules
3 kcal/g
12.5 kj/g
Polyols(sugar alcohols):calories and joules
2.4 kcal/g
10 kj/g
Fiber : calories and joules and why it has calories if we day that we cannot digest it
2 kcal/g
8.4 kj/g
calories due to organic acids that are going to be metabolized by bacteria
Polyols have calories, but we still them use as sucrose replacer, why?
1) The way how sugar alcohols metabolized in a different way in our body , so they wont be converted to fat
2) More sweet than sucrose
Why fat have so many calories
because it has a much higher number of carbon atoms per
gram , and accordingly combustion to CO 2 involves reaction with a
larger number of O 2 molecules
In addition to their higher energy content, fats are a compact way to
store energy because they are nonpolar and therefore not hydrated ;
The longer the fatty acid, ____ the caloric intake
higher
Calorie reduced foods are usually formulated by ___
( using alternative sweeteners to reduce calories derived from sugars
or
(ii) using carbohydrate or protein based fat replacers to mimic certain
functional properties of fat
What are nutritive sweeteners
Sugar alcohols polyols ), e.g., xylitol, sorbitol, maltitol, mannitol, etc.:
these are “ nutritive sweeteners ” because they contribute calories
(1.5 3 kcal/g).
Similar properties of sugar and sugar alcohols
- Most the functional properties with fewer calories, like sugar alcohols, they bind water by hydrogen bonding, which contributes
to the moistness of baked products.
What are non-nutritive sweeteners
are substances that do not contribute to the
calorie content of the food. These very sweet substances are used to
replace sugars as a sweetening agent but cannot provide other
functional properties of sugars.
What sweetener have bitter aftertaste and 200X more sweet than sucrose
Acesulfame-K
Structure of aspartame
is the methyl ester of a dipeptide phenylalanine +
aspartic acid
Does aspartame have caloric content
Yes, the same as proteins
How many times aspartame is more sweet than sucrose
200
A sweetener than is similar to aspartame , but cannot be hydrolyzed by enzymes
neotame
neotame sweetness
7000-13000
Structure of sucralose
is a sucrose molecule in which three of the hydroxyl groups
are replaced by chlorine atoms
Sweetness of sucralose
600
What is simplesse
is a reduced calorie fat replacer made of
microparticulated milk and/or egg white proteins
Simplesse and ___ are used in fat reduced products
Microcrystaline cellulose
Why simplesse is used as fat replace r
Microparticulation provides the mouthfeel of fat with less than half the
calories.
Where simplesse cannot be used
the thermal denaturation
What is olestra
is a sucrose molecule in which 6 8 of its hydroxyl groups are
esterified with fatty acids
Olestra properties
It provides the same properties as fats, is heat stable at frying
temperatures, and is indigestible (0
Is olestra used?
No, because of diarrhea
Carbohydrate-fat replacers: examples and digestibility
Carbohydrate based fat replacers may contribute calories (e.g.,
starch gels) but often are indigestible polysaccharides .
Roles of carbohydrates in digestion
Carbohydrates : both sugars and starch assist the body in utilizing fats
more efficiently by producing organic acids that are required to
convert fats fully to CO 2 and water ( extract maximum energy from
fat metabolism).
The roles of indigestible carbohydrates ( fiber ) in promoting health
have been increasingly recognized over the past few decades.
Fats and oils provide
: fats/oils provide the essential fatty acids ω 3 and ω 6
fatty acids) and are important carriers of fat soluble vitamins
Protein needs are the greatest at what point of time
Protein needs are greatest during pregnancy and childhood (growth).
What plant sources lack lysine
Wheat, corn and rice proteins
Legumes (soybean) lack
Methionine
How protein quality is measured
Protein digestibility and the effects of amino acid
balance/imbalance
What is protein efficiency ratio (PER)
Measure of animal’s weight gain/gram of protein consumed
What is BV
Biological value measures overall nitrogen retention
Calculated= nitrogen in protein consumed-nitrogen excreted
Net protein utilization formula
NPU=BV*digestibility factor
Net protein value (NPV) formula
NPU*%protein in food
What is PDCAAS
Protein Digestibility Corrected Amino Acid Score (PDCAAS)
The protein quality rankings are determined by comparing the amino acid
profile of the specific food protein against a standard amino acid profile
with the highest possible score being a 1.0.
1.0 score means, after digestion of the protein, it provides per unit of
protein 100% or more of the indispensable amino acids required .
What is DIAAS
Digestible Indispensable Amino Acid Score (DIAAS)
It determines amino acid digestibility, at the end of the small intestine ,
providing a more accurate measure of the amounts of amino acids
absorbed by the body and the protein’s contribution to human amino acid
and nitrogen requirements.
Is PDCAAS is accurate
PDCAAS is based on an estimate of crude protein digestibility determined
over the total digestive tract, and values stated using this method generally
overestimate the amount of amino acids absorbed
What is the vitamin
Organic compounds (other than essential amino acids and essential fatty acids) required in the food supply to maintain health and proper functioning of the body.
Food processing and vitamin content
Many food processing operations reduce the vitamin content or
availability in foods.
Fat soluble vitamins are usually more ___ than water soluble and also more likely to ___ ( organism)
Stable
Excessive amounts
3 forms of vitamin A
Retinol
Retinal
Retinoic acid
Where you can find vitamin A
Vitamin A is only found in animal derived food products but β
carotene , found in plants, is a precursor and is thus known as pro
vitamin A (but is not a vitamin
Roles of vitamin A
Retinol
Strengthens mucous membranes;
keeps skin flexible
Retinal
Plays a fundamental role in vision:
vitamin A deficiency
affects night vision
Retinoic acid
Regulates gene expression/
protein production in cell nucleus
What type of vitamin A can be toxic
Vitamin A itself ( from liver)
But not from beta-carotene
Milk in Canada is supplemented with
Vitamin A and D
Vitamin d in the body is synthesized from
cholesterol and other sterols upon exposure to sunlight (specifically
UV B).
Vitamin D is involved in
Vitamin D is involved in the absorption of calcium/phosphorus from
the kidneys.
Deficiency of vitamin D in children can cause
Rickets
How supplement of vitamin D is prepared
(Supplement is prepared by UV irradiation of ergosterol produced by
yeasts.)
Sources of vitamin D
Good food sources: fish, liver, dairy products, eggs
Vitamin E- another name and its function
: Vitamin E α tocopherol) is a natural antioxidant , involved
in cell membrane (lipid) stability
Where usually vitamin E is found and how it can be lost
Vitamin E is present in most unprocessed vegetable oils but may be
lost during processing and refining.
Vitamin K roles, food source and how it is synthesized
Vitamin K has several roles in the human body, including a role in
blood clotting
Good food sources: spinach/cabbage
Vitamin K is also synthesized by microorganisms in the intestinal
tract
Water soluble vitamins are generally _____ than fat soluble
vitamins and more easily _____ during
processing and/or cooking.
less stable
lost due to leaching into water
Other name for vitamin C
L-ascorbic acid
Deficiency disease of vitamin C
Scurvy
Scurvy symptoms
: symptoms include anemia, gum
degeneration, tooth loss, hemorrhaging in the skin, and mucous
membranes (and ultimately death).
Where the name ascorbic acid come from
ascorbic acid derives from the anti scurvy ( scorbuticus in
Latin) function of this molecule.
Vitamin C is very easily ____
oxidized
Vitamin C is only active in its reduced form, so what should be done to preserve its function
Reduce exposure to air
Common food sources of vitamin C
Fruits and vegetables
RDA for vitamin c
75-90 mg/day
In what forms vitamin C is added as an antioxidant
Both L ascorbic acid and its stereoisomer D isoascorbic acid
(erythorbic acid) are food additives employed as antioxidants
Why companies might like to use D isoform is vitamin D , but it is not good
D isoascorbic acid is cheaper but has 20 × less vitamin activity
Roles of vitamin B
enzyme cofactors
RDA for vitamin Bs
values for these vitamins range from a few milligrams/day
down to a few micrograms/day
Name vitamin B1, B2,B12,B3, B5 ,B6,B7,B9 and the other one
B 3 : Niacin B 5 : Pantothenic acid B 6 : Pyridoxine, pyridoxal, pyridoxamine B 7 : Biotin (formerly known as vitamin B 9 : Folacin/folic acid Choline
Source of thiamine
animal products (meat, liver, fish, poultry, etc.) and grain based products
Deficiency in vitamin B1 can lead to
beri beri (leading to muscle atrophy and death)
was associated with consumption of a diet largely made up of
polished ” rice (bran removed contains the thiamin)
Vitamain B1 is destroyed when and consequence of that
by its reaction with sulfite , a food additive;
addition of sulfite to meat (a good source of thiamin) is not permitted.
Source of riboflavin
: good food sources include dairy products, meat, liver,
leafy vegetables, and yeast.
Riboflavin in milk gives what color
yellow/green
Riboflavin is sensitive to ____ and resistant to
heat resistant but light sensitive
What metal does vitamin B12 has in its structure
contains cobalt in a porphyrin ring.
Sources of vitamin B12
Meat products
RDA for cobalamin
3 micrograms/day
It is necessary to obtain the RDA of water soluble vitamins
from diet on daily basis.
True/false
True
Definition of minerals (in nutrition):
Inorganic elements required in the
food supply to maintain health and proper functioning of the body.
Trace elements: what are they and issues with them
Selenium and cobalt are required in trace amounts
but are toxic at higher levels
What metals are toxic even at low levels
Lead and arsenic
Role of Na and RDA
Maintain fluid and electrolyte balance;
sodium ion channels
2000 mg/day
Role of K and RDA
Potassium ion channels
2000 mg/day
Role of Cl and RDA
HCl for gastric juices
2500 mg/day
Role of Ca and RDA
Main mineral component of bones and teeth;
calcium ion channels
1200 mg/day
Role of P and RDA
Energy transfer in the form of ATP/
ADP/ AMP ( present in every cell);
mineral component of bones and teeth
1200 mg/day
Role of Mg and RDA
Enzyme cofactor
300 mg/day
Role of I and RDA
Part of thyroid hormones
150 mg/day
The most common nutrient deficiency in industrialized countries is
Iron deficiency
Role of Fe and RDA
Oxygen transfer (
hemoglobin/ myoglobin)
15 mg/day
Role of Zn and RDA
Digestion/
metabolism of proteins
15 mg/day
Main job in food preservation is to design ____
processes that minimize
nutrient losses and maximize nutrient bioavailability
How much of iron on food is actually absorbed
1-10%
stability of vitamin A to oxidation/light
Unstable in both
Cooking losses of water-soluble vitamins can be minimized by
Steaming
Microwave cooking
stability of vitamin d to oxidation/light
unstable in both
stability of vitamin k to oxidation/light
stable to oxidation, unstable to light
stability of vitamin E to oxidation/light
unstable in both
stability of vitamin C to oxidation/light
Unstable in both
stability of vitamin B1 to oxidation/light
unstable to oxidation
Stable to light
Stability of vitamin B2
stable to oxidation
unstable to light
stability of minerals to oxidation/light
stable to both
stability of essential fatty acids to oxidation/light
unstable to both
stability of essential amino acids to oxidation/light
stable to both
Some foods contain ____ : processing may reduce
their effects and thereby enhance _____of certain food
constituents.
antinutritional factors
bioavailability
2 examples of antinutritional factors
-phytate (cereals and legumes) Trypsin inhibitor (soybean)
Another name for phytate
(inositol hexaphosphate )
Why phytates are bad
Its six phosphate groups bind calcium, iron, phosphorus and other
cations in foodstuffs by chelation and hence reduce their
bioavailability
What has been done to corn to male more nutritious for animals and humans
reduced phytate content by genetic modification
What is a trypsin inhibitor
: a protein present in soybeans acts as an inhibitor
of the digestive enzyme trypsin , which is a protease.
How to make soy more bioavailable?
Heat processing (cooking) denatures trypsin inhibitor
Method of determining protein content and principle
Kjeldahl
Determination of nitrogen content
How to determine moisture content and principle
Vacuum oven
Weight difference before/after drying
How to determine fat content and principle of this method
Soxhlet
Ether extraction
How to determine inorganic content in foods and its principle
Ashing
Combustion
Method to determine carbohydrate content
100-(P+M+F+A)
What is used in Kjeldahl method and what it assumes
Protein content is derived from the nitrogen content of the food
using a conversion factor : although the true conversion factor
depends on the amino acid composition of the protein, a factor of
6.25 is generally used.
Assumes that all nitrogen is coming from protein
How milk adulteration was conducted in China
milk scandal in China was due to adulteration of milk with
melamine (nitrogen content: 75 %) to fool ” the Kjeldahl test.
More complex and expensive analytical methods are employed for
the determination of:
Saturated, monounsaturated, polyunsaturated, and trans fat content Fiber Vitamins Specific minerals, etc.
The fraction of the absorbed nutrient that reaches the systemic
circulation is nutrient
Absorptivity b. Daily intake c. Bioavailability d. Digestibility e. None of the above……
bioavailability
