Midterm 2 Flashcards
Why is barley the principal grain used in brewing
source of malted carbs, malts easily, good flavour, high in starch and low in beta glycogen
What role do hops play in beer
- gives bitter flavour
- essential oils, tannins (aid in precip)
- PRESERVATION
What is the main difference in using grains as a source of fermentable substrate compared to using fruits
grains have less sugar than fruits
Explain the main function of each of the following steps in beermaking: malting, mashing, brewing, fermentation, pasteurization
Malting: pregermenation, beta amylase secretion will produce maltose during mashing (ROASTED)
Mashing: conversion of starch to fermentable sugars
Brewing: boiling to- inactivate enzymes, destroy microorganisms and sterile wort, hops extraction, give colour, denature
fermentation: ales: yeast cells trap CO2 therefore rise (top fermentation)
lagers: suspended yeast cells will sediment and therefore bottom fermentation
pasteurization: done in a bottle, maintain carbonation
Explain the differences between a traditional ale and a traditional lager
ale: top fermentation, served at 10-8 C
lager: bottom fermentation, served at 0-10 C
What are “adjuncts” and why would a brewer want to use them for beermaking
adjuncts: source of non malted carb (corn syrup)
- used to cut cost, also features such as better retention, flavours or nutritional value
lipids vs triglycerides
lipids: very large group of compounds including triglycerides
triglycerides: largest group of lipids (glycerol and 3 FAs)
fats vs oils
fats: solid at room temp, single bonds, saturated
oils: unsaturated, liquid at room temp and dbs
short vs long chain FAs
short: 4-10 carbon chains
long: 16-18 carbons long
saturated vs unsaturated
saturated: single bonds, solid at room temp
unsaturated: DB, liquid
Cis vs Trans isomers
cis: unsaturated, found naturally, cause kink, harder for crystallize
trans: saturated, hydrogenation (converts oil to fat)
n-3 vs. w-3 FAs
n-3: membrane structure (required in diet)
w-3: spy, canola, flax (lenolenic), fish oils- can be synthesized with sufficient linolenic acid
n-3 vs n-6 vs n-9
n-3 and n-9: can’t synthesize DB in body
n-6: lenoleic acid (sunflower oil), develops brain tissue
What does the designation “C18:3 n-3” tell you about the composition and structure of this fatty acid
has 3 DBs
- DB at 3rd carbon from methyl
- 18 carbons long
Why are phospholipids and lipoproteins needed for fat transport within the body
because they are good emulsifiers
role of bile in fat digestion
bile breaks down fat in stomach (emulsifies)
How do the composition of an intestinal micelle and a chylomicron differ
micelles: formed by ingested food lipids with help of bile salts (digested fats)
chylomicron: formed by triglycerides, phospholipids, cholesterol and proteins
Where do the components of chylomicrons and VLDLs originate
chylomicron: dietary fat
VLDLS: dietary proteins and carbs
Relate the relative triglyceride, cholesterol and protein contents of a chylomicron, a VLDL, a LDL and a HDL to their roles in the body
chylomicron: have the highest content of triglycerides; function to transport dietary lipids from intestines to other locations of the body
VLDL: have one of the highest cholesterol levels because of their role to carry cholesterol and triglycerides out; triglycerides is 50%
LDL: triglycerides are low because most have been carried out; cholesterol highest because role to deliver cholesterol to cells
HDL: emulsifiers so lowest triglyceride level and highest protein level
Why do people have their LDL and HDL measured?
LDL measured to measure cholesterol % in body
HDL measured to measure protein content in the body
Why are these referred to as “good” cholesterol and “bad” cholesterol?
LDL is bad because it has the highest cholesterol; collects on walls of BVs
HDL is good because is removes harmful, bad cholesterol
other biomarkers that correlate to CVD
smoking, diabetes; but most accurate are associated with lipids
Distinguish between the functions of pancreatic lipase, lipoprotein lipase and hormone-sensitive lipase
pancreatic lipase: absorption of dietary fat
lipoprotein lipase: enzyme for more important triglyceride derived FAs by muscle for utilization and adipose tissue for storage
hormone sensitive lipase: mobilize stored fats
How does atherosclerotic plaque develop and what effect can it have
develops from damage to endothelium caused by increased blood pressure, smoking or increased cholesterol; this damage leads to plaque formation and can lead to block of blood flow (ishcemia)
Explain in lay terms (as if to your parent or roommate) what fats we should or should not be consuming.
we don’t want to consume a significant about of saturated fats because they raise the cholesterol in our blood
polyunsaturated fats can help reduce bad cholesterol levels in blood which can reduce risk of CVD
Why are PUFAs considered a health benefit? Is there any reason why one might want to limit PUFA intake
health benefit because they lower risk for CVD by reducing bad cholesterol levels in the blood (PUFA long chain are high in HDL)
but may want to limit intake bc excessive intakes of PUFAs may reduce HDL and promote oxidation of LDL, enhancing plaque formation
Where do trans PUFAs come from and why are they considered a health risk
they increase risk for CVD because high in LDL and lowers HDL (double negative)
-have more than one trans double bond (hydrogenation of polyunsaturated oils)
What is the difference between a fat and an oil
the difference between a fat and an oil is MP; fats are solid and oils are liquid
How does triglyceride composition affect melting point
MP depends on chain length; the higher the chain length, the higher the MP
Describe the structure of an oil-in-water and a water-in-oil emulsion and give a few food examples of each
O/W- oil is dispersed and water is the dispersion medium (milk)
W/O- water is dispersed with oil (margarine)
How would you recognize oxidative rancidity of fats in a food product? Which fats are more prone to this problem
oxidative rancidity is evident by odours and bad flavours
- polyunsaturated fats are least stable and most prone to rancidity
- saturated fats are stable and resistant to rancidity
What are the benefits of and concerns about hydrogenation? In food products, what are the alternatives to the use of hydrogenated fats
benefits: more stable, increases shelf life pf foods
concerns: make them more saturated and therefor no health benefits, produces trans fats
alternate: is to add chemical preventives that will compete for oxygen and therefore protect the oil (additives are antioxidants; they work by reacting)
What are the major sources of food protein in the North American diet and how much protein should we eat
major source: peanuts, liver, hamburger, oats, cheese, beans, bread, milk
we consume 150ish g/day
adults should consume: 0.8 g of protein/kg of body weight/day
46g/day women
56g/day men
What is the basic structure of an amino acid, and how do amino acids interact to form proteins
basic structure: amino group, carboxylic group and a central carbon with a reactive R group
- AA acids interact by peptide bond formation through condensation reaction
- fold by H bonds to form secondary structure and fold by reactive r groups to make 3D shape (tertiary)
What is meant by primary, secondary, tertiary and quarternary structure of a protein
primary: individual sequence of AA bonded through peptide bonds
secondary: AA chain could or folds to (held together by H bonds)
tertiary: when secondary structure folds on itself caused by hydrophobic effect of R groups
quaternary: clusters of proteins that interchain by interaction of tertiary structures
Why does a protein take on an ordered higher structure
due to the intermolecular forces that cause it to coil or fold
What is meant by protein denaturation and how does it affect nutritional properties and protein functionality
protein denaturation- the unfolding of a proteins tertiary or secondary structure which causes a loss of function
due to extreme heat, pH, acid or base (becomes more saturated)
What is an “essential” amino acid
must exist preformed in diet
How do you determine if an essential amino acid in a food is “limiting”?
if its concentration in a food is lowest in relation to the AAs required for protein synthesis
What is meant by a “limiting” amino acid
when a specific essential AA is limiting then protein synthesis slows down and is its all used up then synthesis stops
If an amino acid in a food is limiting, is this significant? What is done about it?
it is significant bc if the shortage is chronic then the cells begin to break down their protein making machinery and the cells function less and less effectively even which essential AA is consumed again
Describe the fate of essential and non-essential amino acids after absorption
used to build part of growing protein
altered to make another needed compound, such as the vitamin niacin (fuel)
How do protein allergies develop
develop when mucosal cells are damaged through disease they may function poorly, and take in peptides; these absorbed proteins are often the cause pf allergies where the antibodies produced against these proteins cause anaphylaxis
What is meant by the isoelectric point of a protein and of what relevance is it
pH at which charges are neutralized (most proteins at neutral pH are negatively charged due to side groups)
Ip is significant in protein purification because it represents the pH where solubility is typically minimal
Why does heating usually cause a protein solution to thicken
when heated they are denatured which gives them a viscous property
Explain the role of proteins in stabilizing emulsions and foams
- they form a cohesive protein layer on the emulsion droplets.
- stabilize air bubbles within foams
How do the objectives of dry milling and wet milling differ
dry milling: produces a flour for bread and cake- breaks the seed and separates it into a number of pieces
wet milling: produces grains and corn- separates based on chemical composition rather than anatomical composition
What is the importance of protein in flour with respect to baking quality
the higher the extraction rate the more protein in the flour
- soft flour for cakes has low protein bc low extraction rate
hard flour for bread has high extraction rate and therefore high protein
What is all-purpose flour
for both pastry and bread **it contains more hard flour than soft
What is meant by extraction rate? What would be approximate extraction rates for cake/pastry flour, whole-wheat flour
extraction rate is the weight of flour/ wt of grain x100%
- cake and pastry has low extraction rates 25%
- whole wheat has rate greater than 95%
What is the consequence to the dough of a gluten structure that is too strong? too weak?
if gluten is too weak: can’t stretch in thin films around the air bubbles produced during fermentation and gas bubbles swell and burst therefore product lacks volume
-if gluten is too strong is won’t stretch so bubbles can’t expand therefore causing a dense loaf
What does “leavening” mean? How is a dough leavened?
leavening - the rising of bread due to dough holding CO2 from adding product such as yeast
What role does shortening play in dough formation
makes dough more easily workable and the final product more tender and soft, flaky texture
What is responsible for the gradual lowering of pH in meat after slaughter? Why is this beneficial?
conversion of glycogen to lactic acid causes oH drop which tenderizes meat
Describe the structure of a sarcomere. Why would sarcomere length affect meat tenderness?
sarcomeres are the smallest unit of a muscle fibre and include actin and myosin filaments.
- when they are contracted and shorter they’re less tender
-when long they are tender
this is because the greater the overlap between thick and thin filaments the less tender the meat
What is responsible for the bright red colour of raw meat? How can it be maintained
oxygen is responsible for the bright red colour of raw meat
hemoglobin and myoglobin both contain Fe and Fe++ state meat is fresh and looks red and this is maintained by no heat
Why is it safe to eat a good steak or roast rare* while hamburgers must be well done
rare steak is safe bc bacteria and viruses are on the outside of the meat and are eliminated when outside is cooked
- but burgers are ground beef and therefore the bacteria can be anywhere with in the meat
Explain the effects of location of muscle and marbling on meat tenderness
marbled appearance is more tender
general structure of a carb
carbon, hydrogen and oxygen
monosaccharide, disaccharide, polisaccaride
structural differences btw monosaccharides, disaccharides and polysaccharides? Give food examples of each
mono- simple sugar, mostly hexose sugars ex. glucose, fructose, galactose
di- 2 monosacaride sugars ex. sucrose, maltose, lactose
poly- 10 or more sugar units attached, ex. starches and fibres
What are the end products of digestion in the small intestine for: starch, glucose, sucrose, & lactose?
starch: pancreatic amylase secreted to SI and completes breakdown into glucose molecules for energy
sucrose: broken down into glucose and fructose by sucrase
lactose: lactase in small intestine breaks down to glucose and galactose for absorption
glucose: is the end product ready for absorption
Distinguish between glucagon and glycogen
glycogen is stored in the liver and liver will break it down to glucose by the release of glucagon secreted by the pancreas
Describe the opposing functions of glucagon and insulin in terms of blood glucose homeostasis after a meal and during fasting
after a meal (high glucose): pancreas secretes insulin, glucose in converted to glycogen and stored in the liver, and muscles and fat storing cells use glucose/ glycogen
during fasting (low glucose): pancreas secretes glucagon which converts stored glycogen in the liver to convert to glucose and secrete it in the blood, and gluconeogenises: breakdown of lactate, pyruvate or protein to
amino acids, which go
to liver to synthesize
glucose
What are the differences between Type I and Type II diabetes
type 1 (insulin dependent diabetes mellitus): where absorption of glucose must be assisted with insulin typeII (non insulin dependent diabetes mellitus): insulin resistant, tends to be associated with diets high in sugars and starches (obesity)
What is the difference between glycemic index and glycemic load?
high GI raises blood sugar more than medium to low GI. But the glycemic index does not take into account the amount of carbohydrate in a food %%%%
glycemic load is a better indicator of how a carbohydrate food will affect blood sugar gx%
Give examples of foods with low and with high glycemic indices. What can you suggest about food composition/structure that affects these values
low GI: 55 or less- more slowly digested, absorbed and metabolized and cause lower and slower rise in blood glucose and call for less insulin (kidney beans, pasta, apples)
high GI: 70 or more- these carbs breakdown quickly and have sharp rise in blood glucose (ex pure glucose)
What are the limitations of reporting a GI value for specific foods
type of starch, type of sugar, whether and how food is processed or cooked, whether there is any fat with the carb (fat slows rate of stomach emptying and do slows digestion), presence o any viscous fibre accompanying the carb (increases viscosity of contents of intestines and slows down interaction btw enzymes and starch slowing down digestion), and acidic foods slow down stomach emptying
How are volatile fatty acids formed in the colon? Name some examples of volatile fatty acids
formed when dietary finer is fermented in colon
- acetic acid
- propionic acid
- butyric acid
Does fibre increase or reduce transit time though the stomach? small intestine? large intestine? Why?
presence of any viscous fibre accompanying the carb: increases viscosity of contents of intestines and slows down interaction btw enzymes and starch slowing down digestion
What is the basis for the belief that increasing the fibre content of the diet decreases potential for development of coronary heart disease
dietary fibre plays a key role in
reduction of blood cholesterol
-by reducing bile re-cycling, more bile must be synthesized
and this uses cholesterol
-– the bile that is not re-cycled is excreted, which also serves to reduce cholesterol
What is the basis for the belief that increasing the fibre content of the diet decreases potential for development of diabetes
-slow rate of stomach emptying and passage in small intestine
gives more time for digestion
and helps to reduce glucose levels (spikes) in the
blood, hence reduces glycemic index value
Why would some people want to include Jerusalem artichoke flour as a component of their diet
good source of inert carbohydrate
medium glycemic index, therefore digested slowly - improve diabetes control and reduce risk for heart disease and stroke, successful for weightloss
How do starch and cellulose differ chemically and nutritionally?
starch is glycemic and cellulose is non glycemic (non hydrolyzed or absorbed in the SI)
starch is made of glucose polymers and cellulose makes up fibres - stable structure
What role do sugars play in food preservation? fermentation?
act as food preservative- by lowering water activity and reducing microbial
growth
fermentation- Serves as a growth substrate for microbes
in various foods (sugars are used to make acids, alcohols and carbon dioxide)
What role do sugars play in food colour?
browning reactions with heat (caramelization)
browning reactions with heat and amino acids (mallard browning- chips, bread)
