Week 4 : Alchemy in the kitchen Flashcards
[P1 : PHYSICS AND CHEMISTRY IN COOKING]
What are the 3 types of heat transfer in cooking and explain.
- Conduction : heat passing by direct contact between 2 materials
- Convection : Heat passes via movement of a heated material (water/air) against a colder material (e.g. when boiling, heat is transferred from hot water to food
3, Radiation : Heat transferred by electromagnetic radiation
[P1 : PHYSICS AND CHEMISTRY IN COOKING]
What are the 2 main importance of having heat transfer in food?
- Denaturation of proteins to affect texture (softer texture, more tender)
- Malillard reaction – impacts flavour, aroma, odour
[P1 : PHYSICS AND CHEMISTRY IN COOKING]
Changes in shapes of proteins can affect their taste and texture. True or False?
True
[P1 : PHYSICS AND CHEMISTRY IN COOKING]
define the Maillard reaction (4 key points)
A form of non-enzymatic browning that is initiated by a chemical reaction between a reducing sugar and an amino acid, upon the addition of heat.
[P1 : PHYSICS AND CHEMISTRY IN COOKING]
Maillard reaction involves a series of simultaneous and consecutive chemical reactions with intermediate products. True or False?
True
[P1 : PHYSICS AND CHEMISTRY IN COOKING]
Further flavour compounds arise from further interactions between the Maillard reaction and ___ (process)?
Thermal degradation of lipids
[P1 : PHYSICS AND CHEMISTRY IN COOKING]
How does Maillard reaction contribute to the browning on food?
Compounds, melanoidins are generated to contribute to brown colouration
[P1 : PHYSICS AND CHEMISTRY IN COOKING]
The Maillard reaction is always desirable in all food products. True or False?
False.
Flavours generated from Maillard reaction in products like fruit juice / milk are perceived as off-flavours.
Furthermore, the browning decreases product quality. Browning colour is undesirable in the products mentioned above too, and consumers may deem it to be unsafe for consumption.
[P1 : PHYSICS AND CHEMISTRY IN COOKING]
What are the 2 drawbacks of Maillard reaction in foods?
- Loss of nutrients –HEAT
- amino acids are destroyed and protein quality decreases.
- decreased bioavailability of amino acids and minerals (since AA bind w reducing sugars) - Potentially harmful substances generated
- e.g. Acrylamide in starch rich foods –> associated with cancer
[PT 2 : MICROBIAL SYSTEMS IN FOOD]
All microorganisms in food are harmful. True or False?
False, microbes in food (esp in fermented foods) are beneficial –> probiotics
[PT 2 : MICROBIAL SYSTEMS IN FOOD]
What are the 4 types of microbes that may be present in foods?
- Fermentation microbes – bacteria, yeasts, moulds
- Probiotics - mostly bacteria, promote health benefits
- Spoilage microbes – bacteria/moulds/yeasts that cause spilage
- Pathogens – mostly pathogenic bacteria and viruses causing food-borne illness/disease (food-poisoning)
[PT 2 : MICROBIAL SYSTEMS IN FOOD]
In food fermentation, beneficial microorganisms are intentionally introduced to influence which aspects of food?
Taste, aroma or nutritional quality
(technically shelf life too bc fermentation is a kind of preservation method)
[PT 2 : MICROBIAL SYSTEMS IN FOOD]
What are probiotics?
They are live microorganisms (mostly bacteria) when when administered in adequate amounts confer a health benefit on the host (human/animal) in terms of gut health or immunity
[PT 2 : MICROBIAL SYSTEMS IN FOOD]
Fermented foods are a well-known source of probiotics (e.g. yogurt). Are all MOs used in fermentation considered probiotics?
No, not all probiotics impact human health equally.
No, not all microbes used in fermentation are intended to be probiotics and might just be present to affect sensory qualities etc
[PT 2 : MICROBIAL SYSTEMS IN FOOD]
List a possible reason as to why not all fermented food contain probiotics ( when they are fermented by live bacteria)
These products go through additional processing which kill these live microbes
[PT 2 : MICROBIAL SYSTEMS IN FOOD]
What are prebiotics?
Most prebiotics are what kind of macronutrient?
Non digestible substances that provide a beneficial effect on host by selectively stimulating growth of probiotic bacteria.
Most prebiotics are carbohydrates (bacteria <3 glucose as carbon source)
[PT 2 : MICROBIAL SYSTEMS IN FOOD]
What are synbiotics?
Note : NOT SYMBIOTIC!!
They are preparations of probiotics + prebiotics to deliver the potentially best health effect
synergy
[PT 2 : MICROBIAL SYSTEMS IN FOOD]
What is the difference between the growth of microbes in rotten vs fermented foods?
In food rot, the microbes grow uncontrollably
In fermentation, the choice of MO and fermentation conditions are carefully designed and controlled.
[PT 2 : MICROBIAL SYSTEMS IN FOOD]
What is the difference between food spoilage and food rot?
Food spoilage may occur due to non-microbial means (doesn’t mean it is unsafe to eat but high chance that it is unsafe), while food rot is spoilage due to microbes (definitely unsafe to eat)
[PT 2 : MICROBIAL SYSTEMS IN FOOD]
What are the 4 types of food spoilage and is there a safety issue posed for each type of spoilage?
- Microbial spoilage – potential safety risk
- Chemical spoilage – no safety risk (e.g. oxidation/off-odour)
- Biochemical spoilage – no safety issues (enzymatic reactions, discolouration etc)
- Physical spoilage – no safety issue (e.g. Whey separation in yogurt)
[PT 2 : MICROBIAL SYSTEMS IN FOOD]
Spoiled food is definitely unsafe for consumption. True or False?
False.
– if its not microbial spoilage then its still safe for consumption
[PT 2 : MICROBIAL SYSTEMS IN FOOD]
Unsafe spoiled food will look, smell and taste spoiled. True or False.
False, unsafe spoilt food may not show any signs of physical/chemical spoilage (e.g. off odours/discolouration)
The food could look perfectly normal
[PT 2 : MICROBIAL SYSTEMS IN FOOD]
What is food infection and how can it be prevented?
The ingestion of foods containing pathogens.
Prevented by proper cooking as most microbes are destroyed by heat.
[PT 2 : MICROBIAL SYSTEMS IN FOOD]
What is food intoxication and how can it be prevented?
It is the ingestion of foods containing microbial toxins (the pathogens may be dead alr)
May not be preventable as some toxins are heat-resistant
