1102 EXAM Flashcards
Factors affecting food choices
Physical- affects ability to detect flavours
= body chemistry, taste buds, age, gender
Physiological- taste bias due to past experiences
= brand, advertisement, peers, setting
Cultural- beliefs+ behaviours influence food exposure+ preferences
= religious practices, lifestyle, holiday traditions
Environmental- availability, economical
= Geography, climate, costs, obtainability, we tend to prefer foods that we have been exposed to in childhood
Super- tasters
strong dislikes& fussy but good detection
Medium- tasters
like all foods, sometimes fussy, may detect well
Non- tasters
cannot detect, not fussy, depend on smell and presentation
types of sensory tests
Affective= untrained consumers/ panelists so can detect individual preferences
Analytical= Detect differences, minimal training required
how to prepare for sensory evaluation
- away from cooking and smells
- all samples look identical
- rinse w water first
ideal participant characteristics for sensory evaluation
- No cold/ flu
- No chewing gum immediately beforehand
- Haven’t ingested food w/in an hour before testing
- Nonsmokers
- Not colour blind
- Good mixture of people
VISUAL physical evaluation tests
Microscope= observes microorganisms, starch granules, sugar/ salt crystals etc.
Spectroscopy= Measures colour in foods by detecting amount + wavelength of light transmitted through a solution
WEIGHT/ VOLUME, CONCENTRATION Physical evaluation tests
Refractometer: sugar concentration- determines the angle of polarised light passed through the solution
Spectroscopy= AAS- measure minerals content
TEXTURE, VISCOSITY physical evaluation tests
Linespread test- measures viscosity of viscous foods
Penetrometer- stimulates teeth biting
Shortometer- measures resistance of baked products
What is the Kjeldhal method used for
used to measure protein content
Food industry- accurate labeling+ product quality
Animal Feed- balanced diet+ maintain feed quality
Agriculture- assists in selecting high- protein crop varieties
Steps in the Kjeldahl Method
- Digestion: The sample is mixed with sulfuric acid to break down organic matter, converting nitrogen into ammonium sulfate.
- Distillation: The digest is then made alkaline, releasing ammonia. This ammonia is distilled and captured in a boric acid solution.
- Titration: Finally, the amount of ammonia is measured by titration with a known concentration of acid, usually hydrochloric acid. The amount of nitrogen is then calculated, and a conversion factor (often 6.25) is applied to estimate the total protein content.
What is Benedict’s test used for
detect the presence of reducing sugars, such as glucose, fructose, and lactose, in a sample.
Food Industry: Used to assess sugar content in foods and beverages.
Medical Diagnostics: Sometimes used to detect glucose in urine, which can be an indicator of diabetes.
Benedict’s Test procedure
- Preparation: Benedict’s reagent, a bright blue solution containing copper(II) sulfate, is added to the sample.
- Heating: The mixture is heated in a water bath.
- Observation: If reducing sugars are present, the solution changes color:
Green: low sugar concentration
Yellow to orange: moderate sugar concentration
Red or brick red precipitate: high sugar concentration.
what is the Iodine Test used for
Detect the presence of starch
Food Industry: To test starch content in processed foods.
Botany: To observe starch storage in plant cells.
Education: Commonly used in labs to demonstrate carbohydrate detection
Iodine Test Procedure
- Preparation: A few drops of iodine solution (usually potassium iodide with iodine) are added to the sample.
- Observation: If starch is present, the iodine reacts with it, producing a color change:
Blue-black: Indicates the presence of starch.
Yellow-brown (no color change): Indicates that starch is absent or present in very low amounts.
Cooking
the transfer of energy from a heat source to a food
Destroys pathogens to reduce illness
Changes molecular structure of foods
Ripening
result of enzyme activity+ ethylene gas
Chlorophyll degrade, flavour changes, nutrient changes
Spoilage
Microorganisms prefer high sugar-> natural decomposition-> food lost
Enzymes: rancidity, off- odour, off- taste
Water loss- dehydration, loss of flavour
Decreased eating quality- sensory changes
What are the functions of food packaging
protection, Containment, communication, food safety, production efficiency, environmental impact, convenience, food availability
Primary Packaging
direct contact with food products
-consumers see the most
food safety requirements
e.g metal cans, bottles
Secondary Packaging
protection against physical abuse
Tertiary packaging
distribution of packaged foods
- never seen by customers
Quaternary Packaging
distribution of packaged foods
- never seen by customers
e.g shipping containers
blanching
quick cooking technique that involves briefly boiling food and then plunging it into cold water to preserve its color, texture, and nutrients, often used for vegetables before freezing or further cooking.
destroys enzymes+ reduces microbial load
- hot water 89-99 degrees
- steam 100 degrees
- time varies depending on food
Pasteurisation
heat-treatment process that kills harmful bacteria in food and beverages, particularly dairy, by heating them to a specific temperature for a set period without affecting their quality.
destroys enzymes and reduces pathogens
- high temp, short time
var
sterilisation- canning
food preservation method that involves sealing food in airtight containers and then heating them to high temperatures to kill all microorganisms, including bacteria and spores.
- extends shelf life
slow freezing
preservation method where food is frozen gradually, forming larger ice crystals that can affect texture but still extend shelf life.
-18- -25degrees
- 3 hours
Fast freezing
food is frozen rapidly at very low temperatures, creating small ice crystals that help preserve its texture, flavor, and nutrients better than slower methods.
-18- -40degrees
-5-10 min
Freeze- drying
food is frozen and then subjected to a vacuum, causing the ice in the food to sublimate directly from a solid to a gas, bypassing the liquid phase
- removes moisture while retaining the food’s original structure, nutrients, and flavor, making it lightweight and shelf-stable for long-term storage without refrigeration
