FOOD2000 Flashcards
What are the Major grains?
rice, wheat, corn/maize, barley
What are the Minor grains?
oats, rye, buckwheat (actually a seed not a grain), sorghum, spelt, quinoa, teff
What is the structure of grains?
bran layer, endosperm and germ
What does the bran layer consist of?
- outermost layer
- cellulose
- vitamins and minerals
Includes Aleurone layer: rich in protein, phosphorus and thiamine
What does the endosperm layer consist of?
- starch, protein but very little fibre and trace fats
What does the germ layer consist of?
- rich in fat, minerals and protein
- contains most of the riboflavin
What are Cereals?
- Processed grains
- 75-80% carbohydrate
- Bran cereals: 10-26g/cup dietary fibre (DF)
What are examples of Viscous soluble Dietary Fibre?
pectins,
gums
beta-glucans
psyllium
What are examples of soluble Dietary Fibre?
fructans
polydextrose
arabinoxylan
What are examples of insoluble Dietary Fibre?
resistant starches
cellulose
hemicellulose
lignin
Dietary Fibre fermentability
- the more processed it is, the more structure has been stripped away
- After digestion, DF escapes digestion in the small intestine and enters the large intestine for fermentation
- Becomes a source of nutrition for gut microbiome (organisms in gut)
- When gut microbes are fed well, they produce short chain fatty acids which protect your gut and prevents colorectal cancer
Whole grain vs cereal products
- Whole grain has bran and germ whereas whole meal has bran but no germ
- Cereal products are grain products without the germ
What is Starch?
- complex carbohydrate
- serves as a storage form of energy
What is the structure of starch?
2 types of starch molecules, most starches are a mixture of both:
Amylase (A) and Amylopectin (B).
What is Amylase (A)?
linear helical structure, polysaccharide
gelling characteristics of cooked food and cooled starch mixtures.
What is Amylopectin (B)?
highly branched polysaccharide of glucose.
thickening properties, no gelling
How much of each starch is typically in wheat, rice and corn starches?
What about potato and tapioca starches?
Typically wheat, rice and corn starches are 16-24% amylose and 74-76% amylopectin
Potato and tapioca starches are lower in amylose content
Are Raw starch granules soluble in cold water?
insoluble in cold water
gradually settle at the bottom (non viscous suspension)
What is the texture of Cooked starch?
soft or cohesive
What is the effect of moist heat on starch?
swells, increase in dispersion and viscosity
What is gelatinisation?
gradually occurs over temperature change
After the maximum swelling, the granule bursts. If continued heating, thickness will decrease.
How does starch gel formation occur?
due to amylose undergoing retrogradation
What is retrogradation?
realigning of linear amylose chains by hydrogen bonding eg gravy in fridge gets thicker
What is the effect of dry heat on starch?
- turns brown
- flavour change
- more soluble, reduced thickening
Properties of cooked starch:
- granules
- paste
- corn
Cooked starch granules: result in starch paste
Cooked starch paste: some form gels, some are non gelling
Corn starch forms gel, potato starch does not
What are the FIVE controlled conditions of Uniform starch cooking?
Heating temp
Heating Time
Stirring intensity
pH of mixture
Addition of other ingredients
How does Heating temperature and time affect starch cooking?
- larger granules swell first at lower temperature than smaller sizes, thus no exact gelatinisation temperature
- The more concentrated the mix, the higher the viscosity at lower temperatures due to larger number of granules that swell
- swell at higher temperatures
How does Stirring intensity affect starch cooking?
- accelerate gelatinisation
How does pH affect starch cooking?
decreased viscosity
How does Ingredient addition affect starch cooking?
- sugar
- fat and protein
- sugar: delays swelling and decreases thickness. Rises gelatinisation temperature.
- Fat and protein: coat the starch, delays swelling and hinders gelatinisation
What are Functional starch properties?
- thickeners in sauces
- Stabiliser
- Moisture retainer
- Gel forming agents
- Binders
- Fat substitutes: diet yogurt
- Flavour carrier: can trap oils and fats
What are Classes of wheat?
- hard, soft and durum
durum: high gluten content
What are the grades of flour?
- white flour
- Straight grade
- Patent flours
What is flour?
- fine powder obtained by grinding and sifting cereal
What are the types of flour?
- Hard Wheat; high protein, bread flours
- Soft Wheat; less protein, pastry
- Wheat flour; high starch, mostly gluten, binds ingredients together
- Wholemeal flour; grinder whole grains of wheat, has bran, germ and endosperm
- Strong or bread making flour; higher gluten content, blended flour
- White flour; self raising (has chemical agents) and all purpose (hard and soft), only endosperm, is bleached
- Pastry flour: weaker gluten quality
- Cake flour; reduced gluten content, bleached with chlorine, Protein needed to make cake mixture eg egg
- Enriched flour: white flour with vitamin B and iron\
What is Gluten?
- insoluble proteins in wheat
- Combined of glutanin and gliadin
- Provides elasticity and strength
- Can be extracted from dough
What are non wheat flours?
- cornmeal; chief protein is zein, high in starch
- oat flour; cereal products, cakes and cookies
- Barley flour; minimal gluten forming proteins
- Buckwheat flour; contains glutenous substances,
- Rice flour; no gluten, used as thickener
What is rice?
- short, medium and long grain
- short: glutinous white rice, sticky
- Medium: not as sticky, not as fluffy
- long: fluffy, stay separated after cooking
- Medium brown rice; more fibre and nutrients
Steps in corn refining
- Corn is separated into its components
- Corn inspected & cleaned
- Steeping carried out in mildly acidic water (0.1% sulphuric acid) = prevents excessive bacterial growth & loosens gluten bonds within corn, thus releasing starch
- Corn coarsely ground to break germ loose from other components = mechanical + solvent extraction to remove oil from germ = oil refined/filtered into finished corn oil
- Fibre screened out
- Starch and gluten seperation
What type of corn is used in corn refining?
Shelled corn used = been stripped from cob during harvesting
What is a fruit?
- fleshy/pulpy plant part commonly eaten as a dessert due to its sweetness
- the ripened ovary of a plant
What is a vegetable?
- plant or plant part served raw or cooked, as part of a meal
What is a vegetable-fruit?
- fruit part of plant that is not sweet & usually served with meal, e.g. cucumbers, tomatoes, pumpkins
What do the properties of fruit differ in?
botanical structure, chemical composition and climatic requirements
What are the properties of vegetables?
according to plant parts which derived from = roots; tubers; stems; leaves; buds
The composition of fruits and vegetables depends on?
- botanical variety
- cultivation practices
- Weather
- degree of maturity prior to harvest
- condition of ripeness = continues after harvest & influenced by storage conditions
What is the Structural composition of fruits and vegetables?
- Parenchyma cell (plant cell) = structural unit of the edible portion of most fruits & veges have same fundamental structure
- Vacuole
- Chloroplasts & Mitochondria
- Leucoplasts (colourless plastids)
- Nucleus
- Cell walls
What is the vacuole?
composed of water with soluble substances
What is the Chloroplasts & Mitochondria?
carry out energy conversion in the cell
chloroplasts = through photosynthesis,
mitochondria = through cellular respiration; contain fats, proteins & enzymes
What is the leucoplasts?
colourless plastids, store starch
What is the nucleus?
in cytoplasm, controls reproduction & protein synthesis
What is the cell wall?
consists of primary wall and secondary wall
primary walls of two cells joined together by a common layer
components are cellulose, hemicellulose & pectic substances (complex carbohydrates)
What are the Four main tissue types is fruits and vegetables?
- Dermal tissue (epidermis & endodermis)
- Vascular tissue (xylem & phloem)
- Supporting tissue
- Storage tissue
What is cell turgor?
- rigidity of plant cells resulting from water
- state of turgor depends on osmotic forces
- plant cells have cell walls strong/elastic enough to withstand turgor pressure
- responsible for plumpness, succulence, crispness of live fruits & veges
What are some other cell constituents affecting texture?
- Cellulose, Hemicellulose & Lignin
- Pectic Substances
- Starch
what are the four major groups of pigments?
Chlorophylls
Carotenoids
Anthocyanins (included in the tannins)
Anthoxanthins (included in the tannins)
Chlorophylls
- in chloroplasts
- role in photosynthetic production of carbohydrates
- gives leaves and other plants bright green colour
- oil-soluble
Carotenoids
- fat soluble
- ranging in colour from yellow through orange to red
- often occur along with chlorophylls in chloroplasts, but present in other chromoplasts
- important carotenoids
carotenes of carrots, corn, apricot, peach, citrus fruits; lycopene of tomato, watermelon, apricots
xanthophyll of corn, peach, paprika - some serve as precursors for vitamin A
Anthocyanins (included in the tannins)
- belong to plant chemical group called flavonoids
- water-soluble
- include purple, blue & red pigments of grapes, berries, plums, eggplant, purple cabbage
- are violet or blue in alkaline conditions; become red in acidic conditions
Tannins
- complex mixture of phenolic compounds
- colourless unless reacted with metal ions
- water-soluble tannins in grape & apple juices; tea & coffee brews
- colour & clarity of tea influenced by hardness & pH of brewing water
- possess astringency = influences flavour & contributes to body of tea, coffee, wine, apple cider…
- Excessive astringency = puckery sensation in the mouth = produced when over brewing of tea
Harvesting
- collecting F & V at the specific time of peak quality in terms of colour, texture & flavour
- Mechanical harvesting machines
- continue to respire after harvest (take in oxygen & give off carbon dioxide)
What is ripeness?
the optimum or peak condition of flavour, colour & texture
What is maturity?
the condition of a F/V when it is picked
What are the factors affecting ripening?
- Temperature
- Time
- Added gasses
What is a climacteric fruit?
fruits producing ethylene gas during ripening
What is a non climacteric fruit?
fruits don’t produce ethylene (- don’t ripen after harvesting) & are ethylene sensitive
What are some post harvest changes?
- changes to carbohydrates, pectins and organic acids
- post harvest changes cause a Quality decline in stored respiring F & V after harvesting = called senescence
What are some important factors of post harvest?
- Good humidity control
- Good sanitation
- Harvest at correct maturity stage
- Temperature reduction & maintenance: reduces metabolic activity of produce and prevents spoilage microorganisms
Commercial use of natural or synthetic chemicals
- To maintain quality through prolonged storage life
- Overcome effects of gases
- Edible coatings = lipid-based waxes
- Chemicals = chlorine-based solutions
- Gases = nitric oxide
Fruit/Veg processing
- sorted into size by machine
- Washed in continuously circulating water or under sprays of water
- Mechanical peeling
- moved to conveyer belts
Frozen fruits
- Often packed with dry sugar or syrup
- Individually quick frozen (IQF) fruit with specialised packaging bags
Fruit juices
- Extraction
- Clarification (clearing)
- Deaeration (removal of air)
- Pasteurisation/High-pressure processing (HPP)
- Concentration
- Essence add-back (flavours)
- Canning or bottling
- Freezing
cold pressed fruit juices
- a hydraulic press to extract juice from fruit
Frozen vegetables
- vegetables are boiled or slightly pre-cooked
- ensures that frozen veges retain most of their natural appearance & flavour
- No blanching = product would prematurely turn brown or oxidize before marketing
Legume
any plant from the Fabaceae family, including its leaves, stems & pods
Pulse
the edible seed from a legume plant
Beans
just one type of pulse
Pulses v grains
- Pulses belong to the legume family & grains are in grass family
- Pulses are dicotyledons & cereals are monocotyledons
- We eat the endosperm of cereals & the modified leaves (cotyledons) of pulses
What are the six major pulses in Australia?
- chickpea
- faba or broad bean
- field pea (green peas)
- lentil
- lupin
- mung bean
Pulses nutrition
- inexpensive source of protein and good lipids
- Contain vitamins and minerals
- Good source of complex carbohydrates & dietary fibre (resistant starch)
- Low in fat & high protein
- Protein content (lysine) much higher than in a cereal grain = meat replacement
- easy to digest
- Proteins are mainly albumins & globulins
- Albumins & globulins have lower bioavailability score than meat proteins
Why do pulses vary in colour?
due to anthocyanins & carotenoids = antioxidant compounds
Pulses: Albumin & Globulin Proteins
- Globulins = salt soluble, open flexible structure
- Albumins = water soluble, closed non flexible structure
- Important functional property -> foaming
Aquafaba
- liquid remaining after boiling pulses
- Foam used as a replacement in recipes where egg foams are an essential
Chickpea foam
What are the resistant starches in pulses?
Contain RS type 1 & RS type 3
- RS1 = due to cell wall matrix encapsulating the starch granules =difficult for digestive enzymes to penetrate and digest starch
- RS3 = occurs when pulses are cooked and cooled
Starch in cooled beans undergo retrogradation
What is the general use of pulses?
- fermented food; tofu, tempeh, soy sauce
- flours; gluten free, GF pasta like pulse pasta
- Imitation meat; binders
- Infant formulas
What are some products made from pulses?
- Soy ice cream
What are the types of soy fibre?
- Okara; A pulp fibre by-product of soymilk, Has less protein than whole soybeans. Tastes similar to coconut
- soy bran; Made from hulls. refined (fibrous material removed)
- Soy isolate fibre; Protein isolated in a fibrous form.
What is soybean?
- an oil seed rather than a pulse
Used in - Hydrolysed Vegetable Protein (HVP); Protein from soybeans. Broken down into amino acids by acid hydrolysis chemical process, enhances flavour
- Lecithin; from soy bean oil, used as an emulsifier, promotes stabilisation and smoothes texture
- meat analogous; Contain soy protein or tofu
- Soy fibre; Three basic types: Okara, Soy bran and Soy isolate fibre. High-quality, inexpensive dietary fibre sources
- Soy flour; Made from roasted soybeans ground into fine powder. Three kinds available: Natural, Defatted , Lecithinated. Gives protein boost.
Characteristics of pulses
- Contain oligosaccharides belonging to the raffinose family which are not digested, as humans do not produce the enzyme to break apart these bonds.
- enter the large intestine (LI) where microorganisms producing α-GAL ferment these RFOs
- Soaking beans reduces the RFOs by half & cooking reduces them further
Products from corn refining
- corn syrup
- corn oil
- ethanol
- corn starch
Byproducts of corn refining
- dextrose
- organic acids
- amino acids
- Vitamins C and E
What does the addition of water in cake batter do?
- moisture
- hydration of ingredients
- texture
- flavour
- activation of leavening agents
When all the glutenin genes are missing from wheat?
the loaf volume is a bit smaller.
